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Bishara M, Wu DT, Miron RJ, Nguyen TT, Sinada N, Gluckman H, Salama M. Partial Extraction Therapy (Part 2): Complication Management in Full-Arch Dental Implant Therapy. INT J PERIODONT REST 2023; 43:570-577. [PMID: 37338918 DOI: 10.11607/prd.6127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Partial extraction therapy (PET) is a group of surgical techniques that preserve the periodontium and peri-implant tissues during restorative and implant therapy by conserving a portion of the patient's own root structure to maintain the blood supply, derived from the periodontal ligament complex. PET includes the socket shield technique (SST), proximal shield technique (PrST), pontic shield technique (PtST), and root submergence technique (RST). Although their clinical success and benefits have been demonstrated, several studies report possible complications. The focus of this article is to highlight management strategies for the most common complications associated with PET, including internal root fragment exposure, external root fragment exposure, and root fragment mobility.
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2
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Wen SC, Saleh M, Alrmali A, Wu DT, Wang HL. Utilizing Individualized Titanium Frames (ITFs) for Protected Alveolar Bone Augmentation: A feasibility case series. INT J PERIODONT REST 2023. [PMID: 37552187 DOI: 10.11607/prd.6568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
Despite the various barrier membranes proposed, one of the main challenges for guided bone regeneration (GBR) is space maintenance for large defects as well as ensure adequate blood supply. The presented feasibility case series aims to introduce an original titanium frame (TF) design, customized for each defect, as a modification of well-known principles and materials for GBR, for an enhanced and more predictable horizontal and vertical bone augmentation. Three patients with significant horizontal defects were treated with pre-trimmed TFs to create needed space, a 50%-50% mixture of autograft and bovine xenograft was placed, and then covered with collagen membrane. After 8 months of healing, the sites were reopened, the titanium screws were removed with the frame. An average of 8.0 ± 1.0mm horizontal and 3.0 ± 0.0mm vertical bone gain was achieved at the time of re-entry and implant placement surgery. Bone core biopsy was obtained during the implant placement. Histomorphometric analysis revealed that 42.8% of the sample was new vital bone, 18.8% was residual bone graft particles, and 38.4% was bone marrow like structures. After 3-4 months from implant placement, the implants were restored with provisional crowns and then finalized with zirconia screw-retained crowns. This case series suggests that GBR utilizing TFs with or without collagen membranes can be considered a suitable approach for horizontal and vertical bone augmentation. However, based on only three reported cases, the result should be carefully interpreted.
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3
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Bishara M, Sinada N, Wu DT, Miron RJ, Karateew D, Gluckman H, Salama M. Partial Extraction Therapy (Part 1): Applications in Full-Arch Dental Implant Therapy. INT J PERIODONT REST 2023; 43:443-449. [PMID: 37552191 DOI: 10.11607/prd.5859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
Partial extraction therapy (PET) is a set of surgical techniques that preserve a portion of the patient's own root structure to maintain blood supply derived from the periodontal ligament complex in order to maintain the periodontium and peri-implant tissues during restorative and implant therapy. PET includes the socket shield technique (SST), proximal shield technique (PrST), pontic shield technique (PtST), and root submergence technique (RST). In a traditional hybrid technique, total extraction and full-arch dental implant therapy often require significant bone reduction and palatal/lingual implant placement. In addition, postextraction preservation of the ridge architecture is a major challenge. This case series demonstrates the use of a combination of PET techniques with digital implant planning and guided implant surgery to achieve highly esthetic outcomes in full-arch implant therapy.
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4
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Wu DT, Zhu J, Ohyama H. Students' perceptions on virtual interactive clinical case-based tutorials: A 2-year comparison study. J Dent Educ 2023; 87 Suppl 1:888-891. [PMID: 36341540 DOI: 10.1002/jdd.13140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Revised: 10/18/2022] [Accepted: 10/29/2022] [Indexed: 07/20/2023]
Affiliation(s)
- David T Wu
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
| | - Jenna Zhu
- Harvard School of Dental Medicine, Boston, MA, USA
| | - Hiroe Ohyama
- Department of Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine, Boston, MA, USA
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5
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Wu DT, Diba M, Yang S, Freedman BR, Elosegui‐Artola A, Mooney DJ. Hydrogel viscoelasticity modulates migration and fusion of mesenchymal stem cell spheroids. Bioeng Transl Med 2023; 8:e10464. [PMID: 37206235 PMCID: PMC10189430 DOI: 10.1002/btm2.10464] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 10/17/2022] [Accepted: 11/23/2022] [Indexed: 08/01/2023] Open
Abstract
Multicellular spheroids made of stem cells can act as building blocks that fuse to capture complex aspects of native in vivo environments, but the effect of hydrogel viscoelasticity on cell migration from spheroids and their fusion remains largely unknown. Here, we investigated the effect of viscoelasticity on migration and fusion behavior of mesenchymal stem cell (MSC) spheroids using hydrogels with a similar elasticity but different stress relaxation profiles. Fast relaxing (FR) matrices were found to be significantly more permissive to cell migration and consequent fusion of MSC spheroids. Mechanistically, inhibition of ROCK and Rac1 pathways prevented cell migration. Moreover, the combination of biophysical and biochemical cues provided by fast relaxing hydrogels and platelet-derived growth factor (PDGF) supplementation, respectively, resulted in a synergistic enhancement of migration and fusion. Overall, these findings emphasize the important role of matrix viscoelasticity in tissue engineering and regenerative medicine strategies based on spheroids.
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Affiliation(s)
- David T. Wu
- Laboratory for Cell and Tissue Engineering, John A. Paulson School of Engineering and Applied SciencesHarvard UniversityCambridgeMassachusettsUSA
- Wyss Institute for Biologically Inspired Engineering, Harvard UniversityBostonMassachusettsUSA
- Department of Oral Medicine, Infection, and ImmunityHarvard School of Dental MedicineBostonMassachusettsUSA
| | - Mani Diba
- Laboratory for Cell and Tissue Engineering, John A. Paulson School of Engineering and Applied SciencesHarvard UniversityCambridgeMassachusettsUSA
- Wyss Institute for Biologically Inspired Engineering, Harvard UniversityBostonMassachusettsUSA
- Department of Dentistry‐Regenerative BiomaterialsRadboud Institute for Molecular Life Sciences, Radboud University Medical CenterNijmegenthe Netherlands
| | - Stephanie Yang
- Laboratory for Cell and Tissue Engineering, John A. Paulson School of Engineering and Applied SciencesHarvard UniversityCambridgeMassachusettsUSA
- Department of Oral Medicine, Infection, and ImmunityHarvard School of Dental MedicineBostonMassachusettsUSA
| | - Benjamin R. Freedman
- Laboratory for Cell and Tissue Engineering, John A. Paulson School of Engineering and Applied SciencesHarvard UniversityCambridgeMassachusettsUSA
- Wyss Institute for Biologically Inspired Engineering, Harvard UniversityBostonMassachusettsUSA
| | - Alberto Elosegui‐Artola
- Laboratory for Cell and Tissue Engineering, John A. Paulson School of Engineering and Applied SciencesHarvard UniversityCambridgeMassachusettsUSA
- Wyss Institute for Biologically Inspired Engineering, Harvard UniversityBostonMassachusettsUSA
- Present address:
Cell and Tissue Mechanobiology LaboratoryThe Francis Crick InstituteLondonUK
- Present address:
Department of PhysicsKing's College LondonLondonUK
| | - David J. Mooney
- Laboratory for Cell and Tissue Engineering, John A. Paulson School of Engineering and Applied SciencesHarvard UniversityCambridgeMassachusettsUSA
- Wyss Institute for Biologically Inspired Engineering, Harvard UniversityBostonMassachusettsUSA
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6
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Nath S, Chung D, Yang J, Wu DT. Piloting an innovation society as a tool to supplement dental curricula. J Dent Educ 2022. [PMID: 36565716 DOI: 10.1002/jdd.13164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 12/02/2022] [Accepted: 12/06/2022] [Indexed: 12/26/2022]
Affiliation(s)
- Sapna Nath
- Harvard School of Dental Medicine, Boston, Massachusetts, USA
| | - Dahee Chung
- Harvard School of Dental Medicine, Boston, Massachusetts, USA
| | - Joshua Yang
- Harvard School of Dental Medicine, Boston, Massachusetts, USA
| | - David T Wu
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, USA
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7
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Bishara M, Miron RJ, Kurtzman GM, Sinada N, Wu DT. A Digital Approach to Immediate-Load, Full-Arch Implant Dentistry: A Case Report. INT J PERIODONT REST 2022; 42:587-593. [PMID: 36044687 DOI: 10.11607/prd.6048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Conventional approaches to full-arch implant dentistry require a verified master model created by luting together impression jigs. This process involves numerous steps and is sometimes prone to errors that require subsequent correction. A novel approach involving an extraoral scanning technique using an Imetric 4D Imaging system demonstrates an alternative for same-day delivery of printed full-arch prosthetics. Advantages include the ability to offer a same-day provisional restoration without needing to verify an analog master cast.
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8
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Dai L, Chakraborty S, Wu G, Ye J, Lau YH, Ramanarayan H, Wu DT. Molecular simulation of linear octacosane via a CG10 coarse grain scheme. Phys Chem Chem Phys 2022; 24:5351-5359. [PMID: 35169819 DOI: 10.1039/d1cp05143a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Following our previous work on the united-atom simulation on octacosane (C28H58) (Dai et al., Phys. Chem. Chem. Phys., 2021, 23, 21262-21271), we developed a coarse grain scheme (CG10), which is able to reproduce the pivotal phase characteristics of octacosane with highly improved computational efficiency. The CG10 octacosane chain was composed of 10 consecutive beads, maintaining the fundamental zigzag chain morphology. When the potential functions were set up and the coefficients were parameterized, our CG10 models yielded solid phase diagrams and transitions during an annealing process. We also detected the melting point by various means: direct observation, bond order, density tracking, and an enthalpy plot. Furthermore, our CG10 successfully reproduced the liquid density with only 2% underestimation, indicating its applicability across the solid and liquid phases. Therefore, with the ability to reproduce critical structure and property characteristics, our CG10 scheme provides an effective means of numerically modelling octacosane with highly improved computational efficiency.
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Affiliation(s)
- L Dai
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - S Chakraborty
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - G Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - J Ye
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - Y H Lau
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - H Ramanarayan
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - D T Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
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9
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Tambe LV, Tandale MM, Chhibber R, Wu DT. Treatment of Multiple Gingival Recessions Using Modified Tunnel Technique with V-reverse Sutures: A Report of Three Cases. J Contemp Dent Pract 2022; 23:232-236. [PMID: 35748455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
AIM The clinical case series presents a minimally invasive modified tunnel procedure with autogenous connective tissue graft (CTG) using a V-reverse sutures to treat multiple gingival recessions. BACKGROUND In periodontal and peri-implant plastic procedures, proper graft and flap stabilization are crucial in the outcomes. The coronally advanced flap allows for better access with the possibility of suturing the graft to the de-epithelialized papillae of the periosteum; there is little evidence with using the V-reverse sutures technique in stabilizing the graft and the flap when performing tunnel techniques (TUN). The following case series presents a minimally invasive modified tunnel procedure with autogenous CTG using V-reverse sutures to treat gingival recessions. CASE DESCRIPTION Three patients with Miller Class I maxillary buccal gingival recessions defects were selected for this study. All subjects were treated with the minimally invasive modified tunnel technique with autogenous subepithelial CTG. V-reverse sutures technique was performed to further improve the stability of the graft at the recipient site. Clinical parameters, including mean recession depth and root coverage esthetic score (RES), were recorded at baseline, 1 week, 2 weeks, 1 month, 3 months, 6 months, and 1-year postoperative follow-up visits. CONCLUSION At the 1-year follow-up, complete root coverage was achieved in multiple gingival recessions defect sites. In conclusion, this technique represents an alternative treatment for Miller Class I gingival recessions defects with clinical and esthetically satisfactory outcomes. CLINICAL SIGNIFICANCE Combining the advantages of V-reverse sutures and CTG in the treatment of gingival recessions is feasible and noninvasive.
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Affiliation(s)
- Lashika V Tambe
- Department of Periodontology, Government Dental College and Hospital, Mumbai, Maharashtra, India
| | - Madhura M Tandale
- Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Radhika Chhibber
- Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada, Phone: +5144431573, e-mail:
| | - David T Wu
- Division of Periodontology, Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, United States of America
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10
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Wu DT, Liu QY, Xiao L, Fu FF, Hu WJ, Li Z, Ding YZ. [Clinicopathological and molecular genetic characteristics of superficial soft tissue common venous malformation]. Zhonghua Bing Li Xue Za Zhi 2022; 51:53-55. [PMID: 34979756 DOI: 10.3760/cma.j.cn112151-20210517-00360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Affiliation(s)
- D T Wu
- Department of Pathology, Henan Provincial People's Hospital, Zhengzhou 450003, China
| | - Q Y Liu
- Department of Pathology, Henan Provincial People's Hospital, Zhengzhou 450003, China
| | - L Xiao
- Department of Hemangioma, Henan Provincial People's Hospital, Zhengzhou 450003, China
| | - F F Fu
- Department of Image, Henan Provincial People's Hospital, Zhengzhou 450003, China
| | - W J Hu
- Department of Ultrasonography, Henan Provincial People's Hospital, Zhengzhou 450003, China
| | - Z Li
- Department of Pathology, Henan Provincial People's Hospital, Zhengzhou 450003, China
| | - Y Z Ding
- Department of Pathology, Henan Provincial People's Hospital, Zhengzhou 450003, China
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11
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Wu DT, Raoof S, Latimer JM, Nguyen TT. Partial Extraction Therapy: A Review of Human Clinical Studies. J ORAL IMPLANTOL 2021; 48:436-454. [PMID: 34937086 DOI: 10.1563/aaid-joi-d-21-00095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Partial extraction therapy (PET) is a collective concept encompassing a group of surgical techniques including socket shield, root membrane, proximal shield, pontic shield and root submergence. PET utilizes the patient's own root structure to maintain blood supply derived from the periodontal ligament complex in order to preserve the periodontium and peri-implant tissues during restorative and implant therapy. This review aims to summarize current knowledge regarding PET techniques and present a comprehensive evaluation of human clinical studies in the literature. Two independent reviewers conducted electronic and manual searches until January 1 st , 2021 in the following electronic bibliographic databases: PubMed, EMBASE, and Dentistry & Oral Sciences Source. Grey literature was searched to identify additional candidates for potential inclusion. Articles were screened by a group of 4 reviewers using the Covidence software and synthesized. Systematic search of the literature yielded 5,714 results. 64 articles were selected for full-text assessment, of which, 42 eligible studies were included in the review. 12 studies were added to the synthesis after manual search of the reference lists. A total of 54 studies were examined in this review. In sum, PET techniques offer several clinical advantages: 1) preservation of buccal bone post-extraction and limitation of alveolar ridge resorption 2) mitigation of the need for invasive ridge augmentation procedures 3) soft tissue dimensional stability and high esthetic outcomes. Further randomized clinical studies with larger sample sizes are needed to improve understanding of the long-term clinical outcomes of PET.
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Affiliation(s)
- David T Wu
- Harvard School of Dental Medicine Periodontology Resident & DMSc Candidate Department of Oral Medicine, Infection, and Immunity 188 Longwood Avenue UNITED STATES Boston Massachusetts 02115 Division of Periodontology, Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, USA
| | - Shahram Raoof
- Division of Periodontology, Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, USA
| | - Jessica M Latimer
- Division of Periodontology, Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, USA
| | - Thomas T Nguyen
- McGill University Faculty of Dentistry Assistant Professor Division of Periodontology 2001 McGill College Avenue Room 519 CANADA Montreal QC H3A 1G1 +15143982089 +15143987203 ext 00061 Division of Periodontics, Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
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12
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Dai L, Rutkevych PP, Chakraborty S, Wu G, Ye J, Lau YH, Ramanarayan H, Wu DT. Molecular dynamics simulation of octacosane for phase diagrams and properties via the united-atom scheme. Phys Chem Chem Phys 2021; 23:21262-21271. [PMID: 34543374 DOI: 10.1039/d1cp02720d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We used the united-atom scheme to build three types of crystalline structures for octacosane (C28H58) and carried out molecular dynamics simulations to investigate their phase properties. By gradually heating the three polymorphs, we managed to reproduce the sequence of experimentally reported crystalline phases and rotator phases. By studying the system density, molecule morphology, chain tilt angle and cell anisotropy, we hypothesized three mechanisms behind the observed system deformations and phase transformations during the annealing process. Furthermore, our model successfully predicted the melting temperature and heat of fusion. We also reproduced the characteristics of the rotator phases and the liquid phase, validating the transferability of the united-atom scheme among the different condensed phases of octacosane. Our methodology represents an effective and efficient means of numerical study for octacosane and may be used for other members of the n-alkane family.
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Affiliation(s)
- L Dai
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - P P Rutkevych
- Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore
| | - S Chakraborty
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - G Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - J Ye
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - Y H Lau
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - H Ramanarayan
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
| | - D T Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore.
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13
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Latimer JM, Maekawa S, Yao Y, Wu DT, Chen M, Giannobile WV. Regenerative Medicine Technologies to Treat Dental, Oral, and Craniofacial Defects. Front Bioeng Biotechnol 2021; 9:704048. [PMID: 34422781 PMCID: PMC8378232 DOI: 10.3389/fbioe.2021.704048] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 06/29/2021] [Indexed: 01/10/2023] Open
Abstract
Additive manufacturing (AM) is the automated production of three-dimensional (3D) structures through successive layer-by-layer deposition of materials directed by computer-aided-design (CAD) software. While current clinical procedures that aim to reconstruct hard and soft tissue defects resulting from periodontal disease, congenital or acquired pathology, and maxillofacial trauma often utilize mass-produced biomaterials created for a variety of surgical indications, AM represents a paradigm shift in manufacturing at the individual patient level. Computer-aided systems employ algorithms to design customized, image-based scaffolds with high external shape complexity and spatial patterning of internal architecture guided by topology optimization. 3D bioprinting and surface modification techniques further enhance scaffold functionalization and osteogenic potential through the incorporation of viable cells, bioactive molecules, biomimetic materials and vectors for transgene expression within the layered architecture. These computational design features enable fabrication of tissue engineering constructs with highly tailored mechanical, structural, and biochemical properties for bone. This review examines key properties of scaffold design, bioresorbable bone scaffolds produced by AM processes, and clinical applications of these regenerative technologies. AM is transforming the field of personalized dental medicine and has great potential to improve regenerative outcomes in patient care.
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Affiliation(s)
- Jessica M Latimer
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, United States
| | - Shogo Maekawa
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, United States.,Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yao Yao
- Department of Periodontics & Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI, United States.,Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States
| | - David T Wu
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, United States.,Laboratory for Cell and Tissue Engineering, Harvard John A. Paulson School of Engineering and Applied Sciences, Boston, MA, United States.,Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, United States
| | - Michael Chen
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, United States
| | - William V Giannobile
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, United States
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14
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Abstract
The role of urea as a kinetic promoter for the growth of CO2 hydrates is revealed for the first time using molecular dynamics simulations. Analysis of simulation trajectories shows that urea plays two important roles in the growth process: increasing mass transport of CO2 and catalyzing cage formation at the solid-liquid interface.
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Affiliation(s)
- Po-Wei Wang
- Department of Chemical Engineering, National Taiwan University, Taiwan.
| | - David T Wu
- Department of Chemistry and Department of Chemical and Biological Engineering, Colorado School of Mines, USA
| | - Shiang-Tai Lin
- Department of Chemical Engineering, National Taiwan University, Taiwan.
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15
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Maestas JR, Ma F, Wu N, Wu DT. Electric-Field-Driven Assembly of Dipolar Spheres Asymmetrically Confined between Two Electrodes. ACS Nano 2021; 15:2399-2412. [PMID: 33570907 DOI: 10.1021/acsnano.0c04939] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Externally applied electric fields have previously been utilized to direct the assembly of colloidal particles confined at a surface into a large variety of colloidal oligomers and nonclose-packed honeycomb lattices (J. Am. Chem. Soc. 2013, 135, 7839-7842). The colloids under such confinement and fields are observed to spontaneously organize into bilayers near the electrode. To extend and better understand how particles can come together to form quasi-two-dimensional materials, we have performed Monte Carlo simulations and complementary experiments of colloids that are strongly confined between two electrodes under an applied alternating current electric field, controlling field strength and particle area fraction. Of particular importance, we control the fraction of particles in the upper vs lower plane, which we describe as asymmetric confinement, and which effectively modulates the coordination number of particles in each plane. We model the particle-particle interactions using a Stockmayer potential to capture the dipolar interactions induced by the electric field. Phase diagrams are then delineated as a function of the control parameters, and a theoretical model is developed in which the energies of several idealized lattices are calculated and compared. We find that the resulting theoretical phase diagrams agree well with simulation. We have not only reproduced the structures observed in experiments using parameters that are close to experimental conditions but also found several previously unobserved phases in the simulations, including a network of rectangular bands, zig zags, and a sigma lattice, which we were then able to confirm in experiment. We further propose a simple way to precisely control the number ratio of particles between different planes, that is, superimposing a direct current electric field with the alternating current electric field, which can be implemented conveniently in experiments. Our work demonstrates that a diverse collection of materials can be assembled from relatively simple ingredients, which can be analyzed effectively through comparison of simulation, theory, and experiment. Our model further explains possible pathways between different phases and provides a platform for examining phases that have yet to be observed in experiments.
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Affiliation(s)
- Joseph R Maestas
- Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Fuduo Ma
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Ning Wu
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - David T Wu
- Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, United States
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
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16
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Wu DT, Wu KY, Nguyen TT, Tran SD. The impact of COVID-19 on dental education in North America-Where do we go next? Eur J Dent Educ 2020; 24:825-827. [PMID: 32654328 PMCID: PMC7404882 DOI: 10.1111/eje.12561] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/02/2020] [Accepted: 06/12/2020] [Indexed: 05/23/2023]
Abstract
During the COVID-19 pandemic, the dental education community faced unprecedented challenges. In this commentary, we share the perspectives of faculty clinicians, residents and students in academic dental institutions in the United States and Canada. We discuss COVID-19's impact on various aspects of academic dentistry including patient care, education, research and raise key concerns regarding the future of dental education post-pandemic.
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Affiliation(s)
- David T. Wu
- Department of Oral Medicine, Infection and ImmunityHarvard School of Dental MedicineBostonMAUSA
| | - Kevin Y. Wu
- Faculty of DentistryMcGill UniversityMontrealQCCanada
- Faculty of MedicineLaval UniversityQuebecQCCanada
| | - Thomas T. Nguyen
- Department of Oral Medicine, Infection and ImmunityHarvard School of Dental MedicineBostonMAUSA
| | - Simon D. Tran
- Faculty of DentistryMcGill UniversityMontrealQCCanada
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Wu KY, Wu DT, Nguyen TT, Tran SD. COVID-19's impact on private practice and academic dentistry in North America. Oral Dis 2020; 27 Suppl 3:684-687. [PMID: 32472974 PMCID: PMC7300727 DOI: 10.1111/odi.13444] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 05/14/2020] [Accepted: 05/15/2020] [Indexed: 11/29/2022]
Abstract
The COVID-19 pandemic is a major public health crisis for countries around the world. In response to this global outbreak, the World Health Organization declared a public health emergency of international concern. Dental professionals are especially at high risk of contracting the COVID-19 virus due to the unique nature of dentistry, more specifically, exposure to aerosols and droplets. When it comes to dental emergencies, it was crucial to maintain urgent dental care services operational to help reduce the burden on our healthcare system and hospitals already under pressure. The COVID-19 pandemic has significantly impacted how dentistry is practiced in North America in both the private practice and academic settings. This article shares the perspectives of dentists practicing in private practice and clinician-researchers in academic dental institutions. More specifically, we discuss about measures implemented to minimize risks of disease transmission, challenges in emergency dental care, impact on patients, as well as impact on the professional and personal lives of the dental team during the COVID-19 crisis.
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Affiliation(s)
- Kevin Y Wu
- Faculty of Dentistry, McGill University, Montreal, QC, Canada.,Faculty of Medicine, Laval University, Quebec, QC, Canada
| | - David T Wu
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
| | - Thomas T Nguyen
- Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
| | - Simon D Tran
- Faculty of Dentistry, McGill University, Montreal, QC, Canada
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18
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Abstract
Methane bubble dispersions in a water column can be observed in both vertical subsea piping as well as subsea gas seepages. Hydrate growth has been shown to occur at the gas-water interface under flowing conditions, yet the majority of the current literature is limited to quiescent systems. Gas hydrate risks in subsea piping have been shown to increase in late life production wells with increased water content and with gas-in-water bubble dispersions. The dissolution of subsea methane seepages into seawater, or methane release into the atmosphere, can be affected by hydrate film growth on rising bubbles. A high-pressure water tunnel (HPWT), was used to generate a turbulent, continuous water flow system representative of a vertical jumper line to study the relationship between bulk methane hydrate growth and bubble size during a production-well restart. The HPWT comprises a flow loop of 19.1 mm inner diameter and 4.9 m length, with a vertical section containing an optical window to enable visualization of the bubble and hydrate flow dynamics via a high-speed, high-resolution video camera. Additional online monitoring includes the differential pressure drop, viscosity, temperature, flow rates, and gas consumption. Experimental conditions were maintained at 275 K and 6.2 MPa during hydrate formation and 298 K and 1.4 MPa during hydrate dissociation. Hydrate growth using freshwater and saltwater (3.5 wt % NaCl) was measured at four flow velocities (0.8, 1.2, 1.6, and 1.9 m s-1). The addition of salt is shown in this work to alter the surface properties of bubbles, which introduces changes to bubble dynamics of dispersion and coalescence. Hydrate volume fractions and growth rates in the presence of salt were on average ∼32% lower compared to that in freshwater. This was observed and validated to be due to bubble size and dynamic factors and not due to the 1.5 K thermodynamic inhibition effect of salt. Throughout hydrate growth, methane bubbles in pure freshwater maintained larger diameters (2.4-4.2 mm), whereas the presence of salt promoted fine gas bubble dispersions (0.1-0.7 mm), increasing gas-water interfacial area. While gas bubble coalescence was observed in all freshwater experiments, the addition of salt limited coalescence between gas bubbles and reduced bubble size. Consequently, earlier formation of solid hydrate shells in saltwater produced early mass-transfer barriers reducing hydrate growth rates. While primarily directed toward flow assurance, the observed relationship between hydrates, bubble size, and saltwater also applies to broader research fields in subsea gas seepages and naturally occurring hydrates.
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Affiliation(s)
- Louis C Y Yu
- Center for Hydrate Research, Department of Chemical and Biological Engineering , Colorado School of Mines , 1613 Illinois Street , Golden , Colorado 80401 , United States
- Fluid Science and Resources , The University of Western Australia , 35 Stirling Highway , Crawley , WA 6009 , Australia
| | - Thomas B Charlton
- Center for Hydrate Research, Department of Chemical and Biological Engineering , Colorado School of Mines , 1613 Illinois Street , Golden , Colorado 80401 , United States
- Fluid Science and Resources , The University of Western Australia , 35 Stirling Highway , Crawley , WA 6009 , Australia
| | - Zachary M Aman
- Fluid Science and Resources , The University of Western Australia , 35 Stirling Highway , Crawley , WA 6009 , Australia
| | - David T Wu
- Center for Hydrate Research, Department of Chemical and Biological Engineering , Colorado School of Mines , 1613 Illinois Street , Golden , Colorado 80401 , United States
- Department of Chemistry , Colorado School of Mines , 1012 14th Street , Golden , Colorado 80401 , United States
| | - Carolyn A Koh
- Center for Hydrate Research, Department of Chemical and Biological Engineering , Colorado School of Mines , 1613 Illinois Street , Golden , Colorado 80401 , United States
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Kumari A, Wu DT, Motiani KK, Wu KY, Palumbo M, Tran SD. Career pathways and professional skills of postgraduate students from a dental research-intensive programme. Eur J Dent Educ 2019; 23:143-150. [PMID: 30582648 DOI: 10.1111/eje.12413] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 12/07/2018] [Indexed: 06/09/2023]
Abstract
BACKGROUND With current global trends in postgraduate education, graduate programmes must make evidence-based improvements to offer the best programme that aligns with student needs and prepare them for their future career prospects. The aim of this cross-sectional study was to investigate the postgraduation career pathways of MSc and PhD students who graduated within the past 15 years from the McGill University Postgraduate Dental Research Program. MATERIALS AND METHODS An online questionnaire, composed of 10 closed-ended format items, was used that covered domains such as student profile, career profile, postgraduate skill development, job search experience and satisfaction. Descriptive statistics and interpretative qualitative analysis were used to evaluate student feedback. RESULTS Sixty-six students responded to the online survey, out of which sixty-two students completed the survey (61% participation rate). The majority of the graduate students, 67% (n = 44), obtained MSc degree in Dental Sciences. Overall, our results showed that most graduates started careers in academia in their original field of study and were satisfied with their income. Most graduates reported "critical and creative thinking" to be the strongest acquired skills during their postgraduate training and identified fierce competition for their position of interest as the main challenge after graduation. DISCUSSION AND CONCLUSION Our results showed that graduates in dental research appeared to be overall satisfied with their careers after postgraduate research training, both in terms of scope of practice and income. However, strong competition in obtaining the position of their interest seemed to be the main obstacle after graduation.
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Affiliation(s)
- Amrita Kumari
- Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
| | - David T Wu
- Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
| | | | - Kevin Y Wu
- Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
| | - Maria Palumbo
- Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
| | - Simon D Tran
- Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
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20
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Brumby PE, Yuhara D, Hasegawa T, Wu DT, Sum AK, Yasuoka K. Cage occupancies, lattice constants, and guest chemical potentials for structure II hydrogen clathrate hydrate from Gibbs ensemble Monte Carlo simulations. J Chem Phys 2019; 150:134503. [DOI: 10.1063/1.5084785] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Paul E. Brumby
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Daisuke Yuhara
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Tomohiro Hasegawa
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - David T. Wu
- Chemistry Department, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Amadeu K. Sum
- Hydrates Energy Innovation Laboratory, Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Kenji Yasuoka
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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Chang CK, Chen WL, Wu DT, Lin ST. Improved Directional Hydrogen Bonding Interactions for the Prediction of Activity Coefficients with COSMO-SAC. Ind Eng Chem Res 2018. [DOI: 10.1021/acs.iecr.8b02493] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chun-Kai Chang
- Department of Chemical Engineering, National Taiwan University, Taipei City 10617, Taiwan
| | - Wei-Lin Chen
- Department of Chemical Engineering, National Taiwan University, Taipei City 10617, Taiwan
| | - David T. Wu
- Departments of Chemistry and of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Shiang-Tai Lin
- Department of Chemical Engineering, National Taiwan University, Taipei City 10617, Taiwan
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Yuhara D, Brumby PE, Wu DT, Sum AK, Yasuoka K. Analysis of three-phase equilibrium conditions for methane hydrate by isometric-isothermal molecular dynamics simulations. J Chem Phys 2018; 148:184501. [DOI: 10.1063/1.5016609] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Affiliation(s)
- Daisuke Yuhara
- Department of Mechanical Engineering, Keio University, 3-4-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Paul E. Brumby
- Department of Mechanical Engineering, Keio University, 3-4-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - David T. Wu
- Chemistry Department, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Amadeu K. Sum
- Hydrates Energy Innovation Lab, Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Kenji Yasuoka
- Department of Mechanical Engineering, Keio University, 3-4-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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Abstract
Uranyl, ligand and solvent interactions lead to unique supramolecular assembly.
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24
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Majid AAA, Wu DT, Koh CA. New in Situ Measurements of the Viscosity of Gas Clathrate Hydrate Slurries Formed from Model Water-in-Oil Emulsions. Langmuir 2017; 33:11436-11445. [PMID: 28926254 DOI: 10.1021/acs.langmuir.7b02642] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In situ rheological measurements for clathrate hydrate slurries were performed using a high pressure rheometer to determine the effect of hydrate particles on the viscosity and transportability of these slurries. These measurements were conducted using a well-characterized model water-in-oil emulsion ( Delgado-Linares et al. Model Water in-Oil Emulsions for Gas Hydrate Studies in Oil Continuous Systems . Energy Fuels 2013 , 27 , 4564 - 4573 ). The emulsion consists of a model liquid hydrocarbon, water, and a surfactant mixture of sorbitane monooleate 80 (Span 80) and sodium di-2-ethylhexylsulfosuccinate (Aerosol OT, AOT). This emulsion was used as an analog to water-in-crude oil (w/o) emulsions and provides reproducible results. The flow properties of the model w/o emulsion prior to hydrate formation were investigated in terms of several parameters including water percentage, temperature and pressure. A general equation that describes the viscosity of the emulsion as a function of the aforementioned parameters was developed. This general equation was able to predict the viscosity of a saturated emulsion at various temperatures and water percentages to within ±13% error. The general equation was then used to analyze the effect of hydrate formation on the transportability of gas hydrate slurries. As for hydrate slurries investigation, measurements were performed using methane gas as the hydrate former and a straight vane impeller as a stirring system. Tests were conducted at constant temperature and pressure (1 °C and 1500 psig of methane) and water percentages ranging from 5 to 30 vol %. Results of this work were analyzed and presented in terms of relative values, i.e., viscosities of the slurries relative to the viscosities of the continuous phase at similar temperature and pressure. In this work, a correlation to predict the relative viscosity of a hydrate slurry at various hydrate volume fractions was developed. Analysis of the developed correlation showed that the model was able to predict the relative viscosity of a hydrate slurry to within ±17% error.
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Affiliation(s)
- Ahmad A A Majid
- Center for Hydrate Research, Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
- Faculty of Chemical & Natural Resources Engineering, Universiti Malaysia Pahang , Lebuhraya Tun Razak, 26300 Gambang, Malaysia
| | - David T Wu
- Center for Hydrate Research, Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
- Department of Chemistry, Colorado School of Mines , Golden, Colorado 80401, United States
| | - Carolyn A Koh
- Center for Hydrate Research, Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
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25
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Hu R, Wu DT, Wang D. Modeling intra- and intermolecular correlations for linear and branched polymers using a modified test-chain self-consistent field theory. Phys Rev E 2017; 95:042502. [PMID: 28505798 DOI: 10.1103/physreve.95.042502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Indexed: 11/07/2022]
Abstract
A modified test-chain self-consistent field theory (SCFT) is presented to study the intra- and intermolecular correlations of linear and branched polymers in various solutions and melts. The key to the test-chain SCFT is to break the the translational symmetry by fixing a monomer at the origin of a coordinate. This theory successfully describes the crossover from self-avoiding walk at short distances to screened random walk at long distances in a semidilute solution or melt. The calculations indicated that branching enhances the swelling of polymers in melts and influences stretching at short distances. The test-chain SCFT calculations show good agreement with experiments and classic polymer theories. We highlight that the theory presented here provides a solution to interpret the polymer conformation and behavior under various conditions within the framework of one theory.
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Affiliation(s)
- Renfeng Hu
- Department of Chemical and Biological Engineering and Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, USA
| | - David T Wu
- Department of Chemical and Biological Engineering and Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Dapeng Wang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China
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26
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He Q, Wang SF, Hu R, Akgun B, Tormey C, Peri S, Wu DT, Foster MD. Evidence and Limits of Universal Topological Surface Segregation of Cyclic Polymers. Phys Rev Lett 2017; 118:167801. [PMID: 28474912 DOI: 10.1103/physrevlett.118.167801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Indexed: 06/07/2023]
Abstract
If you mix lines and circles, what happens at the edge of the mixture? The problem is simply stated, but the answer is not obvious. Twenty years ago it was proposed that a universal topological driving force would drive cyclic chains to enrich the surface of blends of linear and cyclic chains. Here such behavior is demonstrated experimentally for sufficiently long chains and the limit in molecular weight where packing effects dominate over the topological driving force is identified.
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Affiliation(s)
- Qiming He
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | - Shih-Fan Wang
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | - Renfeng Hu
- Chemical Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Bulent Akgun
- Department of Chemistry, Bogazici University, Bebek, Istanbul 34342, Turkey
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, 20742, USA
| | - Caleb Tormey
- Chemical Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Somesh Peri
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | - David T Wu
- Chemical Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Mark D Foster
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
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27
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Yang XY, Zhang M, Luo XP, Wang JJ, Yin L, Pang C, Wang GA, Shen YX, Wu DT, Zhang L, Ren YC, Wang BY, Zhang HY, Zhou JM, Han CY, Zhao Y, Feng TP, Hu DS, Zhao JZ. [Body mass index, waist circumference and waist-to-height ratio associated with the incidence of type 2 diabetes mellitus: a cohort study]. Zhonghua Yu Fang Yi Xue Za Zhi 2017; 50:328-33. [PMID: 27029364 DOI: 10.3760/cma.j.issn.0253-9624.2016.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE To investigate the association between body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), and the incidence risk of type 2 diabetes mellitus (T2DM). METHODS In total, 20 194 participants ≥18 years old were selected randomly by cluster sampling from two township (town) of the county in Henan province from July to August of 2007 and July to August of 2008 and the investigation included questionnaires, anthropometric measurements, fasting plasma glucose, and lipid profile examination were performed at baseline; 17 236 participants were enrolled in this cohort study. 14 720 (85.4%) were followed up from July to August 2013 and July to October 2014. Finally, 11 643 participants (4 301 males and 7 342 females) were included in this study. Incidence density and Cox proportional hazards regression models were used to evaluate the risk of T2DM associated with baseline BMI, WC, WHtR, and their dynamic changes. RESULTS After average of 6.01 years following up for 11 643 participants, 613 developed T2DM and the incidence density was 0.89 per 100 person-years. After adjusted for baseline sex, age, smoking, drinking, family history of diabetes, as well as the difference of fasting plasma-glucose (FPG), total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), systolic blood pressure (SBP), diastolic blood pressure (DBP) between baseline and follow-up, Cox Proportional-Hazards regression analysis indicated that T2DM risk of baseline BMI overweight group, BMI obesity group, abnormal WC group and abnormal WHtR group were significantly higher than that of the corresponding baseline normal groups , and the incidence risk of T2DM reached the highest for those whose baseline BMI, WC and WHtR were all abnormal, the corresponding HR (95%CI) were 2.05 (1.62-2.59), 3.01 (2.33-3.90), 2.34 (1.89-2.90), 2.88 (2.21-3.74), 3.32 (2.50-4.40), respectively. Whether baseline BMI/WC was normal or not, T2DM risk increased if baseline WHtR was abnormal, and the HR (95%CI) of baseline normal BMI/abnormal WHtR group, baseline abnormal BMI/abnormal WHtR group, baseline normal WC/abnormal WHtR group, baseline abnormal WC/abnormal WHtR group were 1.88 (1.29-2.74), 3.08 (2.34-4.05), 2.15(1.53-3.00), 3.22 (2.45-4.23), respectively. The analysis for dynamic changes of BMI, WC, and WHtR indicated that in baseline normal WC or WHtR group, T2DM risk increased when baseline normal WC or WHtR developed abnormal at follow-up, and the corresponding HR (95%CI) were 1.79 (1.26-2.55), 2.12(1.32-3.39), respectively. In baseline abnormal WC or WHtR group, T2DM risk decresed when baseline abnormal WC or WHtR reversed to normal at follow-up, and the corresponding HR (95%CI) were 2.16 (1.42-3.29), 2.62 (1.63-4.20), respectively. CONCLUSION BMI, WC, and WHtR were associated with increased T2DM risk. The more abnormal aggregation of BMI, WC, and WHtR presents, the higher T2DM risk was. T2DM risk could be decreased when abnormal WC or WHtR reversed to normal.
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Affiliation(s)
- X Y Yang
- Department of Epidemiology and Health Statistics, College of Public Health, Zhengzhou University, Zhengzhou 450001, China
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28
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Servis MJ, Wu DT, Braley JC. Network analysis and percolation transition in hydrogen bonded clusters: nitric acid and water extracted by tributyl phosphate. Phys Chem Chem Phys 2017; 19:11326-11339. [DOI: 10.1039/c7cp01845b] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Network analysis of hydrogen bonded clusters formed in simulation by extraction of nitric acid and water by TBP interprets cluster topologies and identifies the mechanism for third phase formation.
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Abstract
The surface fluctuations of a melt film of a low molecular weight cyclic polystyrene (CPS) manifest confinement effects for a film thickness (14Rg) much larger than that for which a melt film of the linear chain analog manifests confinement. This is true both in terms of absolute thickness and thickness relative to chain size, Rg. In fact, the linear analog polymer does not manifest confinement effects even at a thickness of 7Rg. Both types of films have a strongly adsorbed layer at the substrate that plays a role in slowing the surface fluctuations for the thinnest films. This layer is 70% thicker for the cyclic chains than for the linear chains. At the interface with the substrate the packing of the cyclic chains is perturbed much more strongly than is the packing of the linear chains.
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Affiliation(s)
- Qiming He
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Suresh Narayanan
- X-ray
Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - David T. Wu
- Chemical
Engineering and Chemistry Departments, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Mark D. Foster
- Department
of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
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Sun L, Akgun B, Hu R, Browning JF, Wu DT, Foster MD. Scaling Behavior and Segment Concentration Profile of Densely Grafted Polymer Brushes Swollen in Vapor. Langmuir 2016; 32:5623-5628. [PMID: 27172089 DOI: 10.1021/acs.langmuir.6b00845] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The scaling of the thickness, hs, of a densely grafted polymer brush of chain length N and grafting density σ swollen in vapor agrees quantitatively with the scaling reported by Kuhl et al. for densely grafted brushes swollen in liquid. Deep in the brush, next to the substrate, the shape of the segment concentration profile is the same whether the brush is swollen by liquid or by vapor. Differences in the segment concentration profile are manifested primarily in the swollen brush interface with the surrounding fluid. The interface of the polymer brush swollen in vapor is much more abrupt than that of the same brush swollen in liquid. This has implications for the compressibility of the swollen brush surface and for fluctuations at that surface.
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Affiliation(s)
- Liang Sun
- Department of Polymer Science, The University of Akron , Akron, Ohio 44325, United States
| | - Bulent Akgun
- NIST Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland, 20899, United States
- Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States
- Department of Chemistry, Bogazici University , Bebek, Istanbul, Turkey
| | - Renfeng Hu
- Department of Chemistry and Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
- Advanced Research Center for Nanolithography (ARCNL) , Amsterdam, The Netherlands
| | - James F Browning
- Chemical and Engineering Materials Division, Spallation Neutron Source, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - David T Wu
- Department of Chemistry and Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401, United States
| | - Mark D Foster
- Department of Polymer Science, The University of Akron , Akron, Ohio 44325, United States
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31
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Zeidman BD, Lu N, Wu DT. Hysteresis of liquid adsorption in porous media by coarse-grained Monte Carlo with direct experimental validation. J Chem Phys 2016; 144:174709. [PMID: 27155649 DOI: 10.1063/1.4948437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The effects of path-dependent wetting and drying manifest themselves in many types of physical systems, including nanomaterials, biological systems, and porous media such as soil. It is desirable to better understand how these hysteretic macroscopic properties result from a complex interplay between gasses, liquids, and solids at the pore scale. Coarse-Grained Monte Carlo (CGMC) is an appealing approach to model these phenomena in complex pore spaces, including ones determined experimentally. We present two-dimensional CGMC simulations of wetting and drying in two systems with pore spaces determined by sections from micro X-ray computed tomography: a system of randomly distributed spheres and a system of Ottawa sand. Results for the phase distribution, water uptake, and matric suction when corrected for extending to three dimensions show excellent agreement with experimental measurements on the same systems. This supports the hypothesis that CGMC can generate metastable configurations representative of experimental hysteresis and can also be used to predict hysteretic constitutive properties of particular experimental systems, given pore space images.
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Affiliation(s)
- Benjamin D Zeidman
- Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Ning Lu
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, USA
| | - David T Wu
- Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, USA
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32
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Servis MJ, Tormey CA, Wu DT, Braley JC. A Molecular Dynamics Study of Tributyl Phosphate and Diamyl Amyl Phosphonate Self-Aggregation in Dodecane and Octane. J Phys Chem B 2016; 120:2796-806. [PMID: 26886767 DOI: 10.1021/acs.jpcb.5b08579] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A molecular dynamics model for tributyl phosphate (TBP) and diamyl amyl phosphonate (DAAP) is presented using the Generalized AMBER Force Field (GAFF) and the AM1-BCC method for calculated atomic charges with a modification to the phosphorus-containing dihedral parameters. The density and average molecular dipole in a neat liquid simulation, and dimerization in dodecane and octane diluents, compare favorably to experimental values. At low extractant concentration, investigation of the dimer structure reveals the offset "head-to-head" orientation as the predominant structure over a range of TBP and DAAP concentrations with a phosphoryl oxygen separation distance between dimerized extractants of 3-5.5 Å. At high extractant concentrations, a graph analysis of extractant aggregates was used to determine concentrations of each aggregate size and the average coordination number, which gives a measure of the linearity of the aggregates. For aggregates up to 7 extractant molecules, the mean free energy of association per molecule was found to be 0.55-0.59 and 0.72 kcal/mol for TBP and DAAP, respectively. In both diluents, TBP formed large aggregates more frequently than DAAP, and those aggregates were more nonlinear than their DAAP equivalents. This finding anticipates differences in aggregation chemistry between TBP and DAAP in PUREX extraction systems.
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Affiliation(s)
- Michael J Servis
- Department of Chemistry and Geochemistry, Colorado School of Mines , Golden, Colorado 80401, United States
| | - Caleb A Tormey
- Department of Chemistry and Geochemistry, Colorado School of Mines , Golden, Colorado 80401, United States
| | - David T Wu
- Department of Chemistry and Geochemistry, Colorado School of Mines , Golden, Colorado 80401, United States
| | - Jenifer C Braley
- Department of Chemistry and Geochemistry, Colorado School of Mines , Golden, Colorado 80401, United States
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33
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Wang D, Hu R, Mabry JN, Miao B, Wu DT, Koynov K, Schwartz DK. Scaling of Polymer Dynamics at an Oil–Water Interface in Regimes Dominated by Viscous Drag and Desorption-Mediated Flights. J Am Chem Soc 2015; 137:12312-20. [DOI: 10.1021/jacs.5b07108] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dapeng Wang
- Department
of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, United States
| | - Renfeng Hu
- Department
of Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Joshua N. Mabry
- Department
of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, United States
| | - Bing Miao
- College
of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - David T. Wu
- Department
of Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Kaloian Koynov
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Daniel K. Schwartz
- Department
of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, United States
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34
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Yuhara D, Barnes BC, Suh D, Knott BC, Beckham GT, Yasuoka K, Wu DT, Sum AK. Nucleation rate analysis of methane hydrate from molecular dynamics simulations. Faraday Discuss 2015; 179:463-74. [PMID: 25876773 DOI: 10.1039/c4fd00219a] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Clathrate hydrates are solid crystalline structures most commonly formed from solutions that have nucleated to form a mixed solid composed of water and gas. Understanding the mechanism of clathrate hydrate nucleation is essential to grasp the fundamental chemistry of these complex structures and their applications. Molecular dynamics (MD) simulation is an ideal method to study nucleation at the molecular level because the size of the critical nucleus and formation rate occur on the nano scale. Various analysis methods for nucleation have been developed through MD to analyze nucleation. In particular, the mean first-passage time (MFPT) and survival probability (SP) methods have proven to be effective in procuring the nucleation rate and critical nucleus size for monatomic systems. This study assesses the MFPT and SP methods, previously used for monatomic systems, when applied to analyzing clathrate hydrate nucleation. Because clathrate hydrate nucleation is relatively difficult to observe in MD simulations (due to its high free energy barrier), these methods have yet to be applied to clathrate hydrate systems. In this study, we have analyzed the nucleation rate and critical nucleus size of methane hydrate using MFPT and SP methods from data generated by MD simulations at 255 K and 50 MPa. MFPT was modified for clathrate hydrate from the original version by adding the maximum likelihood estimate and growth effect term. The nucleation rates calculated by MFPT and SP methods are within 5%, and the critical nucleus size estimated by the MFPT method was 50% higher, than values obtained through other more rigorous but computationally expensive estimates. These methods can also be extended to the analysis of other clathrate hydrates.
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Affiliation(s)
- Daisuke Yuhara
- Department of Mechanical Engineering, Keio University, Yokohama, Japan
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35
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Sun CC, Sun W, Price S, Hughes C, Ter Horst J, Veesler S, Lewtas K, Myerson A, Pan H, Coquerel G, van den Ende J, Meekes H, Mazzotti M, Rosbottom I, Taulelle F, Black S, Mackenzie A, Janbon S, Vekilov P, Threlfall T, Turner T, Back K, Cuppen H, Toroz D, Sefcik J, Lovelock J, Hammond R, Candoni N, Simone E, Ward M, Bertran CA, Vetter T, Sear R, De Yoreo J, Davey R, Anwar J, Santiso E, Wu DT, Roberts K, Peters B, Schroeder S, Jones F, Rasmuson A, Cölfen H, Zeglinski J, Salvalaglio M. Solvent and additive interactions as determinants in the nucleation pathway: general discussion. Faraday Discuss 2015; 179:383-420. [DOI: 10.1039/c5fd90038g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Price S, Rimez B, Sun W, Peters B, Christenson H, Hughes C, Sun CC, Veesler S, Pan H, Brandel C, Biscans B, Meekes H, Rosbottom I, Roth WJ, Seton L, Taulelle F, Black S, Threlfall T, Vekilov P, Poornachary S, Diemand J, Toroz D, Salvalaglio M, Tipduangta P, Sefcik J, Booth S, Rasmuson A, Janbon S, Ter Horst J, Simone E, Hammond R, Bertran CA, Vetter T, Sear R, De Yoreo J, Harris K, Ristic R, Kavanagh A, Roberts K, Breynaert E, Myerson A, Coquerel G, Wu D, Cölfen H, Cuppen H, Smets M, Wu DT. Nucleation in complex multi-component and multi-phase systems: general discussion. Faraday Discuss 2015; 179:503-42. [DOI: 10.1039/c5fd90039e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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37
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Lee JS, Lee NH, Peri S, Foster MD, Majkrzak CF, Hu R, Wu DT. Surface segregation driven by molecular architecture asymmetry in polymer blends. Phys Rev Lett 2014; 113:225702. [PMID: 25494077 DOI: 10.1103/physrevlett.113.225702] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Indexed: 06/04/2023]
Abstract
The contributions of chain ends and branch points to surface segregation of long-branched chains in blends with linear chains have been studied using neutron reflectometry and surface-enhanced Raman spectroscopy for a series of novel, well-defined polystyrenes. A linear response theory accounting for the number and type of branch points and chain ends is consistent with surface excesses and composition profile decay lengths, and allows the first determination of branch point potentials. Surface excess is determined primarily by chain ends with branch points playing a secondary role.
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Affiliation(s)
- Jae Sik Lee
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA
| | - Nam-Heui Lee
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA
| | - Somesh Peri
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA
| | - Mark D Foster
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA
| | - Charles F Majkrzak
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Renfeng Hu
- Department of Chemical Engineering and Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, USA
| | - David T Wu
- Department of Chemical Engineering and Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, USA
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Abstract
Nucleation from solution is a ubiquitous phenomenon with relevance to myriad scientific disciplines, including pharmaceuticals, biomineralization, and disease. One prominent example is the nucleation of clathrate hydrates, multicomponent crystalline inclusion compounds relevant to the energy industry where they block pipelines and also constitute a potential vast energy resource. Despite their importance, the molecular mechanism of incipient hydrate formation remains unknown. Herein, we employ advanced molecular simulation tools (pB histogram, equilibrium path sampling) to provide a statistical-mechanical basis for extracting physical insight into the molecular steps by which clathrates form. Through testing the Mutually Coordinated Guest (MCG) order parameter, we demonstrate that both guest (methane) and host (water) structuring are crucial to accurately describe the nucleation of hydrates and determine a critical nucleus size of MCG-1 = 16 at 255 K and 500 bar. Equipped with a validated (and novel) reaction coordinate, subsequent equilibrium path sampling simulations yield the free energy barrier and nucleation rate. The resulting quantitative nucleation process is described by the MCG clustering mechanism. This constitutes a significant advance in the field of hydrates research, as the fitness of a molecular descriptor has never been statistically verified. More broadly, this work has significance to a wide range of multicomponent nucleation contexts wherein the formation mechanism depends on contributions from both solute and solvent.
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Affiliation(s)
- Brian C Barnes
- Center for Hydrate Research, Chemical & Biological Engineering Department, Colorado School of Mines , Golden, Colorado 80401, United States
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39
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Ma F, Wang S, Zhao H, Wu DT, Wu N. Colloidal structures of asymmetric dimers via orientation-dependent interactions. Soft Matter 2014; 10:8349-8357. [PMID: 25207502 DOI: 10.1039/c4sm01492h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We apply an AC electric field to induce anisotropic interactions among asymmetric colloidal dimers. These anisotropic interactions, being shape-specific and orientation-dependent, can create complex and unique structures that are not possible for spherical particles or symmetric dimers. More specifically, we show a series of novel structures that closely resemble one- and two-dimensional antiferromagnetic lattices, including small clusters, linear chains, square lattices, and frustrated triangular arrays. All of them are uniquely formed by alternating association between dimers with opposite orientations. Our theoretical model attributes those patterns to an exquisite balance between electrostatic (primarily dipolar) and electrohydrodynamic interactions. Although similarly oriented dimers are strongly repulsive, the oppositely oriented dimers possess a concave shoulder in the pair interaction, which favors clustering to minimize the number of overlaps between neighboring particles. By combining the anisotropy in both particle geometry and field-induced interaction, our work suggests a new way to tailor colloidal interactions on anisotropic particles, which is important for both scientific understanding and practical applications.
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Affiliation(s)
- Fuduo Ma
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, USA.
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40
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41
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Abstract
Methane clathrate hydrate nucleation and growth is investigated via analysis of molecular dynamics simulations using a new order parameter. This order parameter (OP), named the Mutually Coordinated Guest (MCG) OP, quantifies the appearance and connectivity of molecular clusters composed of guests separated by water clusters. It is the first two-component OP used for quantifying hydrate nucleation and growth. The algorithm for calculating the MCG OP is described in detail. Its physical motivation and advantages compared to existing methods are discussed.
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Affiliation(s)
- Brian C Barnes
- Center for Hydrate Research, Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Gregg T Beckham
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - David T Wu
- Center for Hydrate Research, Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA
| | - Amadeu K Sum
- Center for Hydrate Research, Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA
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42
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Wang SF, Yang S, Lee J, Akgun B, Wu DT, Foster MD. Anomalous surface relaxations of branched-polymer melts. Phys Rev Lett 2013; 111:068303. [PMID: 23971618 DOI: 10.1103/physrevlett.111.068303] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Indexed: 06/02/2023]
Abstract
The dynamics of thermally stimulated surface fluctuations of 100 nm thick films of long-branched polymers are measured for the first time. In contrast to comparable films of linear or cyclic chains that show no change in viscosity upon confinement, films of 6-pom, 6-star, and 6-end end-branched stars show viscosities, inferred from x-ray photon correlation spectroscopy, as much as 100 times higher than in the bulk. This difference varies in magnitude with chain architecture. Branching has a profound effect on confinement, even for these unentangled chains.
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Affiliation(s)
- Shih-fan Wang
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
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43
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Affiliation(s)
- Fuduo Ma
- Department of Chemical and Biological
Engineering, Colorado School of Mines,
Golden, Colorado 80401, United States
| | - David T. Wu
- Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, United
States
| | - Ning Wu
- Department of Chemical and Biological
Engineering, Colorado School of Mines,
Golden, Colorado 80401, United States
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44
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Affiliation(s)
- Boxi Liu
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United
States
| | - Suresh Narayanan
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - David T. Wu
- Chemical Engineering
and Chemistry
Departments, Colorado School of Mines,
Golden, Colorado 80401, United States
| | - Mark D. Foster
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United
States
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45
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Lafond PG, Gilmer MW, Koh CA, Sloan ED, Wu DT, Sum AK. Orifice jamming of fluid-driven granular flow. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 87:042204. [PMID: 23679404 DOI: 10.1103/physreve.87.042204] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Indexed: 06/02/2023]
Abstract
The three-dimensional jamming of neutrally buoyant monodisperse, bidisperse, and tridisperse mixtures of particles flowing through a restriction under fluid flow has been studied. During the transient initial accumulation of particles at the restriction, a low probability of a jamming event is observed, followed by a transition to a steady-state flowing backlog of particles, where the jamming probability per particle reaches a constant. Analogous to the steady-state flow in gravity-driven jams, this results in a geometric distribution describing the number of particles that discharge prior to a jamming event. We develop new models to describe the transition from an accumulation to a steady-state flow, and the jamming probability after the transition has occurred. Predictions of the behavior of the geometric distribution see the log-probability of a jam occurring proportionally to (R(2)(2)-1), where R(2) is the ratio of opening diameter to the second moment number average particle diameter. This behavior is demonstrated to apply to more general restriction shapes, and collapses for all mixture compositions for the restriction sizes tested.
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Affiliation(s)
- Patrick G Lafond
- Center for Hydrate Research, Department of Chemical & Biological Engineering, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, USA
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46
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Guariguata A, Pascall MA, Gilmer MW, Sum AK, Sloan ED, Koh CA, Wu DT. Jamming of particles in a two-dimensional fluid-driven flow. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 86:061311. [PMID: 23367936 DOI: 10.1103/physreve.86.061311] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Indexed: 06/01/2023]
Abstract
The jamming of particles under flow is of critical importance in a broad range of natural and industrial settings, such as the jamming of ice in rivers, or the plugging of suspended solids in pipeline transport. Relatively few studies have been carried out on jamming of suspended particles under flow, in comparison to the many studies on jamming in gravity-driven flows that have revealed various features of the jamming process. Fluid-driven particle flows differ in several aspects from gravity-driven flows, particularly in being compatible with a range of particle concentrations and velocities. Additionally, there are fluid-particle interactions and hydrodynamic effects. To investigate particle jamming in fluid-driven flows, we have performed both experiments and computer simulations on the flow of circular particles floating over water in an open channel with a restriction. We determined the flow-rate boundary for a dilute-to-dense flow transition, similar to that seen in gravity-driven flows. The maximum particle throughput increased for larger restriction sizes consistent with a Beverloo equation form over the entire range of particle mixtures and restriction sizes. The exponent of ~3/2 in the Beverloo equation is consistent with approximately constant acceleration of grains due to fluid drag in the immediate region of the opening. We verified that the jamming probability from the dense flow gave a geometric distribution in the number of particles escaping before a jam. The probability of jamming in both experiments and simulations was found to be dependent on the ratio of channel opening to particle size, but only weakly dependent on the fluid flow velocity. Flow entrance effects were measured and observed to affect the jamming probability, and dependence on particle friction coefficient was determined from simulation. A comprehensive model for the jamming probability integrating these observations from the different flow regimes was shown to be in good agreement for experimental data on average times before jamming.
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Affiliation(s)
- Alfredo Guariguata
- Center for Hydrate Research, Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado 80401, USA
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Abstract
Fundamental understanding of gas hydrate formation and decomposition processes is critical in many energy and environmental areas and has special importance in flow assurance for the oil and gas industry. These areas represent the core of gas hydrate applications, which, albeit widely studied, are still developing as growing fields of research. Discovering the molecular pathways and chemical and physical concepts underlying gas hydrate formation potentially can lead us beyond flowline blockage prevention strategies toward advancing new technological solutions for fuel storage and transportation, safely producing a new energy resource from natural deposits of gas hydrates in oceanic and arctic sediments, and potentially facilitating effective desalination of seawater. The state of the art in gas hydrate research is leading us to new understanding of formation and dissociation phenomena that focuses on measurement and modeling of time-dependent properties of gas hydrates on the basis of their well-established thermodynamic properties.
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Affiliation(s)
- Carolyn A Koh
- Center for Hydrate Research, Colorado School of Mines, Golden, CO 80401, USA.
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Lin CM, Li CS, Sheng YJ, Wu DT, Tsao HK. Size-dependent properties of small unilamellar vesicles formed by model lipids. Langmuir 2012; 28:689-700. [PMID: 22126796 DOI: 10.1021/la203755v] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The size-dependent behavior of small unilamellar vesicles is explored by dissipative particle dynamics, including the membrane characteristics and mechanical properties. The spontaneously formed vesicles are in the metastable state and the vesicle size is controlled by the concentration of model lipids. As the vesicle size decreases, the bilayer gets thinner and the area density of heads declines. Nonetheless, the area density in the inner leaflet is higher than that in the outer. The packing parameters are calculated for both leaflets. The result indicates that the shape of lipid in the outer leaflet is like a truncated cone but that in the inner leaflet resembles an inverted truncated cone. Based on a local order parameter, our simulations indication that the orientation order of lipid molecules decreases as the size of the vesicle reduces and this fact reveals that the bilayer becoming thinner for smaller vesicle is mainly attributed to the orientation disorder of the lipids. The membrane tension can be obtained through the Young-Laplace equation. The tension is found to grow with reducing vesicle size. Therefore, small vesicles are less stable against fusion. Using the inflation method, the area stretching and bending moduli can be determined and those moduli are found to grow with reducing size. Nonetheless, a general equation with a single numerical constant can relate bending modulus, area stretching modulus, and bilayer thickness irrespective of the vesicle size. Finally, a simple metastable model is proposed to explain the size-dependent behavior of bilayer thickness, orientation, and tension.
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Affiliation(s)
- Chun-Min Lin
- Institute of Polymer Science and Engineering, National Taiwan University, Taipei, Taiwan 106, ROC
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49
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Abstract
The size of droplets in emulsions is important in many industrial, biological, and environmental systems, as it determines the stability, rheology, and area available in the emulsion for physical or chemical processes that occur at the interface. While the balance of fluid inertia and surface tension in determining droplet size under turbulent mixing in the inertial subrange has been well established, the classical scaling prediction by Shinnar half a century ago of the dependence of droplet size on the viscosity of the continuous phase in the viscous subrange has not been clearly validated in experiment. By employing extremely stable suspensions of highly viscous oils as the continuous phase and using a particle video microscope (PVM) probe and a focused beam reflectance method (FBRM) probe, we report measurements spanning 2 orders of magnitude in the continuous phase viscosity for the size of droplets in water-in-oil emulsions. The wide range in measurements allowed identification of a scaling regime of droplet size proportional to the inverse square root of the viscosity, consistent with the viscous subrange theory of Shinnar. A single curve for droplet size based on the Reynolds and Weber numbers is shown to accurately predict droplet size for a range of shear rates, mixing geometries, interfacial tensions, and viscosities. Viscous subrange control of droplet size is shown to be important for high viscous shear stresses, i.e., very high shear rates, as is desirable or found in many industrial or natural processes, or very high viscosities, as is the case in the present study.
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Affiliation(s)
- John A Boxall
- Center for Hydrate Research, Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
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50
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Abstract
ABSTRACTHillert’s model of grain growth consists of a drift term in size space that leads asymptotically to a distribution function and a growth exponent not often observed. Later theories introduce a diffusion term that is either assumed to dominate the drift term or a correction to it. This paper shows that the lower order drift term alone determines asymptotic grain growth behavior. A possible conclusion is that experimental results may need to be reinterpreted.
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