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Panin SV, Nguyen DA, Buslovich DG, Alexenko VO, Pervikov AV, Kornienko LA, Berto F. Effect of Various Type of Nanoparticles on Mechanical and Tribological Properties of Wear-Resistant PEEK + PTFE-Based Composites. Materials (Basel) 2021; 14:ma14051113. [PMID: 33673543 PMCID: PMC7956855 DOI: 10.3390/ma14051113] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 02/17/2021] [Accepted: 02/23/2021] [Indexed: 11/16/2022]
Abstract
The mechanical and tribological properties of polyetheretherketone (PEEK)- and PEEK + PTFE (polytetrafluoroethylene)-based composites loaded with and four types of nanoparticles (carbonaceous, metallic, bimetal oxide, and ceramic) under metal- and ceramic-polymer tribological contact conditions were investigated. It was found that loading with the nanofillers in a small content (0.3 wt.%) enabled improvement of the elastic modulus of the PEEK-based composites by 10-15%. In the metal-polymer tribological contact, wear resistance of all nanocomposites was increased by 1.5-2.3 times. In the ceramic-polymer tribological contact, loading PEEK with metal nanoparticles caused the intensification of oxidation processes, the microabrasive counterpart wear, and a multiple increase in the wear rate of the composites. The three component "PEEK/10PTFE/0.3 nanofillers" composites provided an increase in wear resistance, up to 22 times, for the metal-polymer tribological contact and up to 12 times for the ceramic-polymer one (with a slight decrease in the mechanical properties) compared to that of neat PEEK. In all cases, this was achieved by the polymer transfer film formation and adherence on the counterparts. The various effects of the four types of nanoparticles on wear resistance were determined by their ability to fix the PTFE-containing transfer film on the counterpart surfaces.
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Affiliation(s)
- Sergey V. Panin
- Laboratory of Mechanics of Polymer Composite Materials, Institute of Strength Physics and Materials Science SB RAS, 634055 Tomsk, Russia; (D.G.B.); (V.O.A.); (L.A.K.)
- Department of Materials Science, Engineering School of Advanced Manufacturing Technologies, National Research Tomsk Polytechnic University, 634030 Tomsk, Russia
- Correspondence:
| | - Duc A. Nguyen
- Seaside Branch Russian-Vietnamese Tropical Center, Department of Tropical Endurance, Nha Trang 57106, Vietnam;
| | - Dmitry G. Buslovich
- Laboratory of Mechanics of Polymer Composite Materials, Institute of Strength Physics and Materials Science SB RAS, 634055 Tomsk, Russia; (D.G.B.); (V.O.A.); (L.A.K.)
- Department of Materials Science, Engineering School of Advanced Manufacturing Technologies, National Research Tomsk Polytechnic University, 634030 Tomsk, Russia
| | - Vladislav O. Alexenko
- Laboratory of Mechanics of Polymer Composite Materials, Institute of Strength Physics and Materials Science SB RAS, 634055 Tomsk, Russia; (D.G.B.); (V.O.A.); (L.A.K.)
| | - Aleksander V. Pervikov
- Laboratory of Physical Chemistry of Ultrafine Materials, Institute of Strength Physics and Materials Science SB RAS, 634055 Tomsk, Russia;
| | - Lyudmila A. Kornienko
- Laboratory of Mechanics of Polymer Composite Materials, Institute of Strength Physics and Materials Science SB RAS, 634055 Tomsk, Russia; (D.G.B.); (V.O.A.); (L.A.K.)
| | - Filippo Berto
- Faculty of Engineering, Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway;
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Vu HX, Schneider M, Bentrup U, Dang TT, Phan BMQ, Nguyen DA, Armbruster U, Martin A. Hierarchical ZSM-5 Materials for an Enhanced Formation of Gasoline-Range Hydrocarbons and Light Olefins in Catalytic Cracking of Triglyceride-Rich Biomass. Ind Eng Chem Res 2015. [DOI: 10.1021/ie504519q] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [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)
- Hoan X. Vu
- Leibniz Institute for Catalysis e.V. at the University of Rostock, Albert Einstein Str. 29a, 18059 Rostock, Germany
- Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - Matthias Schneider
- Leibniz Institute for Catalysis e.V. at the University of Rostock, Albert Einstein Str. 29a, 18059 Rostock, Germany
| | - Ursula Bentrup
- Leibniz Institute for Catalysis e.V. at the University of Rostock, Albert Einstein Str. 29a, 18059 Rostock, Germany
| | - Tung T. Dang
- Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - Binh M. Q. Phan
- Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - Duc A. Nguyen
- Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - Udo Armbruster
- Leibniz Institute for Catalysis e.V. at the University of Rostock, Albert Einstein Str. 29a, 18059 Rostock, Germany
| | - Andreas Martin
- Leibniz Institute for Catalysis e.V. at the University of Rostock, Albert Einstein Str. 29a, 18059 Rostock, Germany
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Sarkar K, Nguyen DA, Gruebele M. Loop and stem dynamics during RNA hairpin folding and unfolding. RNA 2010; 16:2427-34. [PMID: 20962040 PMCID: PMC2995403 DOI: 10.1261/rna.2253310] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [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: 05/05/2010] [Accepted: 08/26/2010] [Indexed: 05/24/2023]
Abstract
2-Aminopurine (2AP) is a fluorescent adenine analog that probes mainly base stacking in nucleic acids. We labeled the loop or the stem of the RNA hairpin gacUACGguc with 2AP to study folding thermodynamics and kinetics at both loci. Thermal melts and fast laser temperature jumps detected by 2AP fluorescence monitored the stability and folding/unfolding kinetics. The observed thermodynamic and kinetic traces of the stem and loop mutants, though strikingly different at a first glance, can be fitted to the same free-energy landscape. The differences between the two probe locations arise because base stacking decreases upon unfolding in the stem, whereas it increases in the loop. We conclude that 2AP is a conservative adenine substitution for mapping out the contributions of different RNA structural elements to the overall folding process. Molecular dynamics (MD) totaling 0.6 μsec were performed to look at the conformations populated by the RNA at different temperatures. The combined experimental data, and MD simulations lead us to propose a minimal four-state free-energy landscape for the RNA hairpin. Analysis of this landscape shows that a sequential folding model is a good approximation for the full folding dynamics. The frayed state formed initially from the native state is a heterogeneous ensemble of structures whose stem is frayed either from the end or from the loop.
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Affiliation(s)
- Krishnarjun Sarkar
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
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Uddin LQ, Supekar KS, Amin H, Nguyen DA, Greicius MD, Menon V. Functional and structural connectivity of the human intraparietal sulcus and angular gyrus. Neuroimage 2009. [DOI: 10.1016/s1053-8119(09)70269-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Sridhar T, Nguyen DA, Prabhakar R, Prakash JR. Rheological observation of glassy dynamics of dilute polymer solutions near the coil-stretch transition in elongational flows. Phys Rev Lett 2007; 98:167801. [PMID: 17501464 DOI: 10.1103/physrevlett.98.167801] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Indexed: 05/15/2023]
Abstract
It has long been conjectured that the macroscopic dynamics of dilute polymer solutions may exhibit a glasslike slowdown caused by ergodicity breaking, in the vicinity of the coil-stretch transition in elongational flows. We report experimental observations using a filament stretching rheometer that confirm the existence of such glassy states. It is observed that different time-dependent elongational strain-rate profiles lead to a pronounced history dependence and aging effects within a narrow range of strain rates. The results have a direct bearing on the analysis and design of processes employing dilute polymer solutions, such as ink-jet printing, surface coating, and turbulent-drag reduction.
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Affiliation(s)
- T Sridhar
- Department of Chemical Engineering, Monash University, Melbourne, VIC-3800, Australia
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Nguyen DA, Moraes FFD, Fogler HS. Fused Chemical Reactions. 3. Controlled Release of a Catalyst To Control the Temperature Profile in Tubular Reactors. Ind Eng Chem Res 2004. [DOI: 10.1021/ie049933k] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [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)
- Duc A. Nguyen
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, and Departamento de Engenharia Quimica, Universidade Estadual de Maringa, Avenida Colombo 5790, Bloco D-90, Sala 102, 87020-900 Maringa, PR, Brazil
| | - Flavio Faria de Moraes
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, and Departamento de Engenharia Quimica, Universidade Estadual de Maringa, Avenida Colombo 5790, Bloco D-90, Sala 102, 87020-900 Maringa, PR, Brazil
| | - H. Scott Fogler
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, and Departamento de Engenharia Quimica, Universidade Estadual de Maringa, Avenida Colombo 5790, Bloco D-90, Sala 102, 87020-900 Maringa, PR, Brazil
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Abstract
Closure of the tight junctions of the mammary epithelium has been shown to accompany the onset of copious milk secretion or lactogenesis, stage 2, in both goats and humans. Here we use injection of [(14)C]sucrose and FITC-albumin (fluorescein isothiocyanate-albumin) into the mammary duct to follow the course of tight junction closure during lactogenesis in mice. To examine the hormonal changes responsible, we ovariectomized day 16 or 17 pregnant mice and found that closure followed ovariectomy with a mean delay of 13.6+/-1.5 (s.e.m. ) h. That progesterone withdrawal is the trigger for closure was shown by the finding that injection of progesterone within 4 h of ovariectomy delayed closure and that closure occurred after injection of the progesterone antagonist RU 486 in intact late pregnant mice. Endocrine ablation studies showed that low to moderate concentrations of corticosterone and either placental lactogen or prolactin are necessary for tight junction closure triggered by progesterone withdrawal. Thus the hormonal requirements for tight junction closure are similar to those shown by other investigators to promote lactogenesis, stage 2. Further, the tight temporal control of tight junction permeability suggests that ovariectomy of the late pregnant mouse may be a good model for molecular studies of the lactogenic switch.
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Affiliation(s)
- D A Nguyen
- Department of Physiology, University of Colorado School of Medicine, Denver, Colorado 80262, USA
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Nguyen DA, Fogler HS, Chavadej S. Fused Chemical Reactions. 2. Encapsulation: Application to Remediation of Paraffin Plugged Pipelines. Ind Eng Chem Res 2001. [DOI: 10.1021/ie0009886] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [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)
- Duc A. Nguyen
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, and The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 10330
| | - H. Scott Fogler
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, and The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 10330
| | - Sumaeth Chavadej
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, and The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 10330
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Abstract
Tight junctions form a narrow, continuous seal that surrounds each endothelial and epithelial cell at the apical border, and act to regulate the movement of material through the paracellular pathway. In the mammary gland, the tight junctions of the alveolar epithelial cells are impermeable during lactation, and thus allow milk to be stored between nursing periods without leakage of milk components from the lumen. Nonetheless mammary epithelial tight junctions are dynamic and can be regulated by a number of stimuli. Tight junctions of the mammary gland from the pregnant animal are leaky, undergoing closure around parturition to become the impermeable tight junctions of the lactating animal. Milk stasis, high doses of oxytocin, and mastitis have been shown to increase tight junction permeability. In general changes in tight junction permeability in the mammary gland appear to be the results of a state change and not assembly and disassembly of tight junctions. Both local factors, such as intramammary pressure and TGF-beta, and systemic factors, such as prolactin, progesterone, and glucocorticoids, appear to play a role in the regulation of mammary tight junctions. Finally, the tight junction state appears to be closely linked to milk secretion. An increase in tight junction permeability is accompanied by decrease in the milk secretion rate, and conversely, a decrease in tight junction permeability is accompanied by an increase in the milk secretion rate.
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Affiliation(s)
- D A Nguyen
- University of Colorado Health Sciences Center, Department of Physiology and Biophysics, Denver 80262, USA
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Ribera AB, Nguyen DA. Primary sensory neurons express a Shaker-like potassium channel gene. J Neurosci 1993; 13:4988-96. [PMID: 8229210 PMCID: PMC6576330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Developmentally regulated action potentials are a hallmark of Rohon-Beard cells, a class of sensory neurons. In these neurons as well as other primary spinal neurons of Xenopus laevis, the functional differentiation of delayed-rectifier potassium current regulates the waveform of the action potential during the initial day of its appearance. Later, the acquisition of another voltage-dependent potassium current--the A current--plays a major role in regulating excitability. In order to understand the molecular basis of this functional differentiation, genes encoding voltage-dependent potassium currents expressed in the embryonic amphibian nervous system are being cloned. Here, we report the functional properties and developmental localization of a second Xenopus Shaker-like gene (Xenopus Kv 1.1; XSha1; GenBank accession number M94258) encoding a potassium current. Homology screening with the mouse gene MBK1 led to its isolation. Functional expression in oocytes identifies it as a delayed-rectifier current when assembled as a homooligomeric structure. Specific transcripts corresponding to XSha1 and to the previously cloned gene XSha2 are both detectable by RNase protection in RNA isolated from the embryonic nervous system. However, whole-mount in situ hybridization reveals the temporal pattern and cellular localization of XSha1 but not XSha2 mRNA, suggesting that the concentration of XSha2 transcripts in individual cells is lower than the threshold for detection by this method. Of particular interest, Rohon-Beard cells express XSha1 mRNA. In addition, XSha1 mRNA is detected in several structures containing neural crest derivatives including spinal ganglia, the trigeminal ganglion, and branchial arches; its presence in motor nerves and lateral spinal tracts suggests that both CNS and PNS glia express the mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A B Ribera
- Department of Physiology, University of Colorado Health Sciences Center, Denver 80262
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Sernka TJ, Langley AE, Smith SG, Nguyen DA. Milrinone produces a positive inotropy but is not inhibitory to gastric ion transport. Proc Soc Exp Biol Med 1986; 183:140-4. [PMID: 3749031 DOI: 10.3181/00379727-183-1-rc1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The cardiac drugs ouabain and milrinone are positive inotropic agents. Since ouabain has inhibitory effects on ion transport in the gastrointestinal tract associated with vasoconstriction and hypoxia, milrinone needed to be tested also. This report indicates that therapeutic levels of milrinone on either side of the isolated stomach wall of the guinea pig has no significant effects on active chloride ion transport or the electrical parameters of the tissue. To verify that milrinone was active in the heart at these same levels, contractility of the isolated heart of the guinea pig was measured. Milrinone significantly increased ventricular pressure and pressure development. Thus milrinone may be expected to exert its inotropic stimulation of the heart during heart failure without compromising gastrointestinal functions.
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Nguyen DA, Sernka TJ. Effects of bile salts and prostaglandins on sodium transport in isolated rat gastric mucosa. Gen Physiol Biophys 1985; 4:337-48. [PMID: 3861466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To determine whether prostaglandins may protect against bile salt inhibition of ion transport in the stomach, gastric mucosal tissue was isolated from the rat and mounted in flux chambers. Transport of Na+ was traced with radioisotopes in the absence of bile salts and then in the presence of conjugated taurocholate or unconjugated deoxycholate at low, intermediate and high mucosal concentrations (1, 5 and 15 mmol/1). At a high (7.40) or low (3.4) mucosal pH, only the unconjugated deoxycholate inhibited active Na+ transport from mucosa to submucosa with respect to untreated controls. Inhibition of Na+ transport was apparent at a low level of deoxycholate, which also inhibited the electrical potential difference. Intermediate and high levels of deoxycholate lowered the tissue resistance. When the tissues were exposed to mucosal prostaglandin E2 or its 16,16-dimethyl analogue before and during acidified taurocholate administration, Na+ transport was not changed significantly but the electrical resistance remained high. Thus, unconjugated bile salt is more potent than conjugated bile salt in inhibiting Na+ transport and breaking the gastric mucosal barrier, and prostaglandins may afford some small protection.
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