1
|
Ranjuna MK, Balakrishnan J. High temperature anomalous Raman and photoluminescence response of molybdenum disulfide with sulfur vacancies. Sci Rep 2023; 13:16418. [PMID: 37775525 PMCID: PMC10541451 DOI: 10.1038/s41598-023-43756-w] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 09/27/2023] [Indexed: 10/01/2023] Open
Abstract
We report an intriguing anomalous behavior observed in the temperature-dependent Raman spectra of mono-, bi-, and trilayer molybdenum disulfide samples with sulfur vacancies, measured at high temperatures ranging from room temperature to 463 K. In contrast to existing reports, we observed a decrease in the FWHM of the A[Formula: see text] phonon mode, along with an increase in the relative intensity of the A[Formula: see text] mode to the E[Formula: see text] mode, as the temperature increased. This trend becomes less prominent as the layer number increases from monolayer, disappearing entirely in few-layer samples. Additionally, we observed an intensity enhancement in the photoluminescence spectra of MoS2 samples at high temperatures (up to 550 K), which depends on the layer number. These observations are explained by considering the presence of sulfur vacancies, their interaction with the environment, electron density reduction, and a phonon-mediated intervalley charge transfer at elevated temperatures. Our results unambiguously establish that the effect of defects (sulfur vacancies) is more prominently reflected in the temperature dependence of FWHM and the relative intensity of the Raman modes rather than in the Raman peak positions.
Collapse
Affiliation(s)
- M K Ranjuna
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad, Kerala, 678623, India.
| | - Jayakumar Balakrishnan
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad, Kerala, 678623, India.
| |
Collapse
|
2
|
Jeemon P, Bahuleyan CG, Chandgalu Javaregowda D, Punnoose E, Rajendiran G, Unni G, Abdullakutty J, Balakrishnan J, Joseph J, Gnanaraj JP, Sreedharan M, Pillai MR, KR N, Thomas P, Sebastian P, Daniel R, Edakutty R, Ahmad S, Mattummal S, Thomas SC, Joseph S, Pisharody S, Chacko S, Syam N, Nair T, Nanjappa V, Ganesan V, George V, Ganapathi S, Harikrishnan S. Team based collaborative care model, facilitated by mHealth enabled and trained nurses, for management of heart failure with reduced ejection fraction in India (TIME-HF): design and rationale of a parallel group, open label, multi-centric cluster randomised controlled trial. Wellcome Open Res 2023; 8:197. [PMID: 37795133 PMCID: PMC10545985 DOI: 10.12688/wellcomeopenres.19196.2] [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] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2023] [Indexed: 10/06/2023] Open
Abstract
Background: Heart failure (HF) is a debilitating condition associated with enormous public health burden. Management of HF is complex as it requires care-coordination with different cadres of health care providers. We propose to develop a team based collaborative care model (CCM), facilitated by trained nurses, for management of HF with the support of mHealth and evaluate its acceptability and effectiveness in Indian setting. Methods: The proposed study will use mixed-methods research. Formative qualitative research will identify barriers and facilitators for implementing CCM for the management of HF. Subsequently, a cluster randomised controlled trial (RCT) involving 22 centres (tertiary-care hospitals) and more than 1500 HF patients will be conducted to assess the efficacy of the CCM in improving the overall survival as well as days alive and out of hospital (DAOH) at two-years (CTRI/2021/11/037797). The DAOH will be calculated by subtracting days in hospital and days from death until end of study follow-up from the total follow-up time. Poisson regression with a robust variance estimate and an offset term to account for clustering will be employed in the analyses of DAOH. A rate ratio and its 95% confidence interval (CI) will be estimated. The scalability of the proposed intervention model will be assessed through economic analyses (cost-effectiveness) and the acceptability of the intervention at both the provider and patient level will be understood through both qualitative and quantitative process evaluation methods. Potential Impact: The TIME-HF trial will provide evidence on whether a CCM with mHealth support is effective in improving the clinical outcomes of HF with reduced ejection fraction in India. The findings may change the practice of management of HF in low and middle-income countries.
Collapse
Affiliation(s)
- Panniyammakal Jeemon
- Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, 695011, India
| | | | | | - Eapen Punnoose
- Malankara Orthodox Syrian Church Medical College, Kolenchery, Kerala, India
| | | | - Govindan Unni
- Jubilee Mission medical College and Research Institute, Thrissur, Kerala, India
| | | | | | | | - Justin Paul Gnanaraj
- Rajiv Gandhi Government General Hospital, Madras Medical College, Chennai, Tamilnadu, India
| | - Madhu Sreedharan
- NIMS Heart Foundation, NIMS Medicity, Thiruvananthapuram, Kerala, India
| | | | - Neenumol KR
- Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, 695011, India
| | | | | | - Rachel Daniel
- NS Memorial Institute of Medical Sciences, Kollam, Kerala, India
| | | | - Sajan Ahmad
- St Gregorios Memorial Mission Hospital, Parumala, Kerala, India
| | | | - Sunu C Thomas
- Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, 695011, India
| | - Stigi Joseph
- Little Flower Hospital and Research Centre, Angamaly, Ernakulam, Kerala, India
| | - Sunil Pisharody
- EMS Memorial Cooperative Hospital and Research Centre Ltd, Malappuram, Kerala, India
| | - Susanna Chacko
- Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, 695011, India
| | - N Syam
- Government District Hospital, Kollam, Kerala, India
| | - Tiny Nair
- PRS Hospital, Thiruvananthapuram, Kerala, India
| | - Veena Nanjappa
- Sri Jayadeva Institute of Cardiovascular Science and Research, Mysore, Karnataka, India
| | | | | | - Sanjay Ganapathi
- Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, 695011, India
| | | |
Collapse
|
3
|
Joy NJ, K RM, Balakrishnan J. A simple and robust machine learning assisted process flow for the layer number identification of TMDs using optical contrast spectroscopy. J Phys Condens Matter 2022; 51:025901. [PMID: 36322998 DOI: 10.1088/1361-648x/ac9f96] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 11/02/2022] [Indexed: 06/16/2023]
Abstract
Layered transition metal dichalcogenides (TMDs) like tungsten disulphide (WS2) possess a large direct electronic band gap (∼2 eV) in the monolayer limit, making them ideal candidates for opto-electronic applications. The size and nature of the bandgap is strongly dependent on the number of layers. However, different TMDs require different experimental tools under specific conditions to accurately determine the number of layers. Here, we identify the number of layers of WS2exfoliated on top of SiO2/Si wafer from optical images using the variation of optical contrast with thickness. Optical contrast is a universal feature that can be easily extracted from digital images. But fine variations in the optical images due to different capturing conditions often lead to inaccurate layer number determination. In this paper, we have implemented a simple Machine Learning assisted image processing workflow that uses image segmentation to eliminate this difficulty. The workflow developed for WS2is also demonstrated on MoS2, graphene and h-BN, showing its applicability across various classes of 2D materials. A graphical user interface is provided to enhance the adoption of this technique in the 2D materials research community.
Collapse
Affiliation(s)
- Nikhil Joseph Joy
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad 678623, Kerala, India
| | - Ranjuna M K
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad 678623, Kerala, India
| | - Jayakumar Balakrishnan
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad 678623, Kerala, India
| |
Collapse
|
4
|
M K R, Balakrishnan J. Investigating the thermal transport in gold decorated graphene by opto-thermal Raman technique. Nanotechnology 2022; 33:135706. [PMID: 34937004 DOI: 10.1088/1361-6528/ac45c2] [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] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Abstract
We report a systematic study on the thermal transport properties of gold nanoparticles (Au NPs) decorated single-layer graphene on a SiO2/Si substrate by the opto-thermal Raman technique. Our results, with moderate Au NPs coverage (<10%), demonstrate an enhancement in the thermal conductivity of graphene by ∼55% from its pristine value and a decrement in the interface conductance by a factor of 1.5. A detailed analysis of our results shows the importance of the photo-thermal conversion efficiency of Au NPs, plasmon-phonon coupling and lattice modifications in the graphene developed after gold nanoparticles deposition in enhancing the thermal conductivity and reducing the interface thermal conductance of the system. Our study paves way for a better understanding of the thermal management in such hybrid systems, which are envisioned as excellent candidates for optoelectronics and photonics applications.
Collapse
Affiliation(s)
- Ranjuna M K
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad-678623, Kerala, India
| | - Jayakumar Balakrishnan
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad-678623, Kerala, India
| |
Collapse
|
5
|
Sinha A, Ranjan P, Ali A, Balakrishnan J, Thakur AD. Graphene oxide and its derivatives as potential Ovchinnikov ferromagnets. J Phys Condens Matter 2021; 33:375801. [PMID: 34157699 DOI: 10.1088/1361-648x/ac0d84] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 06/22/2021] [Indexed: 06/13/2023]
Abstract
Ovchinnikov postulated the possibility of ferromagnetism in organic compounds having a mixed density ofsp3andsp2carbon atoms. Such systems provide an interesting avenue for exploring magnetism in the absence of the quintessentiald- andf-block elements as ingredients. As graphene oxide (GO) and its derivatives naturally possess a mixture ofsp3andsp2carbon atoms, it is pertinent to look at them as potential candidates for Ovchinnikov ferromagnetism. We have looked at the evolution of magnetic property in a series of GO samples with a gradual increase in the degree of oxidation and hence thesp3/sp2fraction. Starting with a GO sample with a highsp3/sp2ratio, we utilize chemical reduction technique to prepare another set of reduced graphene oxide (rGO) samples. Magnetization measurements on these samples further illustrate the importance ofsp3/sp2fraction on magnetic behavior suggesting GO and its derivatives as a potential Ovchinnikov ferromagnet candidate. The evolution of magnetic moment withsp3/sp2carbons can be utilized in carbon based spintronic applications.
Collapse
Affiliation(s)
- Apurva Sinha
- Department of Physics, Indian Institute of Technology, Patna, Bihta 801106, India
| | - Pranay Ranjan
- Department of Physics, UAE University, Al-Ain 15551, United Arab Emirates
| | - Anzar Ali
- Department of Physics, Indian Institute of Science Education and Research, Mohali 140306, India
| | - Jayakumar Balakrishnan
- Department of Physics, Indian Institute of Technology Palakkad, Kozhippara 678557, India
| | - Ajay D Thakur
- Department of Physics, Indian Institute of Technology, Patna, Bihta 801106, India
| |
Collapse
|
6
|
|
7
|
Ranjan P, Agrawal S, Sinha A, Rao TR, Balakrishnan J, Thakur AD. Author Correction: A Low-Cost Non-explosive Synthesis of Graphene Oxide for Scalable Applications. Sci Rep 2018; 8:14593. [PMID: 30254338 PMCID: PMC6156589 DOI: 10.1038/s41598-018-32556-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Collapse
Affiliation(s)
- Pranay Ranjan
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801106, India.
| | - Shweta Agrawal
- Department of Chemistry, Indian Institute of Technology Patna, Bihta, 801106, India
| | - Apurva Sinha
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801106, India
| | - T Rajagopala Rao
- Department of Chemistry, Indian Institute of Technology Patna, Bihta, 801106, India
| | - Jayakumar Balakrishnan
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801106, India.,Department of Physics, Indian Institute of Technology Palakkad, Palakkad, 678557, India
| | - Ajay D Thakur
- Department of Physics, Indian Institute of Technology Patna, Bihta, 801106, India.
| |
Collapse
|
8
|
Abstract
We report an interesting bow-tie shaped bursting behaviour in a certain parameter regime of two resistive-capacitative shunted Josephson junctions, one in the oscillatory and the other in the excitable mode and coupled together resistively. The burst emerges in both the junctions and they show near-complete synchronization for strong enough couplings. We discuss a possible bifurcation scenario to explain the origin of the burst. An exhaustive study on the parameter space of the system is performed, demarcating the regions of bursting from other solutions.
Collapse
Affiliation(s)
- Thotreithem Hongray
- School of Physics, University of Hyderabad, Central University, P.O., Gachi Bowli, Hyderabad 500 046, India
| | - J Balakrishnan
- School of Natural Sciences and Engineering, National Institute of Advanced Studies (N.I.A.S.), Indian Institute of Science Campus, Bangalore-560012, India
| | - Syamal K Dana
- CSIR-Indian Institute of Chemical Biology, Kolkata-700032, India
| |
Collapse
|
9
|
Cherian CT, Giustiniano F, Martin-Fernandez I, Andersen H, Balakrishnan J, Özyilmaz B. 'Bubble-free' electrochemical delamination of CVD graphene films. Small 2015; 11:189-94. [PMID: 25179223 DOI: 10.1002/smll.201402024] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 07/22/2014] [Indexed: 05/08/2023]
Abstract
The production of large amounts of hydrogen bubbles, typical of electrochemical delamination methods based on the electrolysis of water, results in mechanical damage to graphene during the delamination, transfer, and drying steps. Here a novel 'bubble-free' delamination method is introduced which exploits the electrochemical dissolution of native copper oxide at a potential lower than that required for the formation of hydrogen bubbles, enabling the production of defect-free graphene stack.
Collapse
Affiliation(s)
- Christie Thomas Cherian
- Department of Physics, National University of Singapore, Singapore, 117542; Graphene Research Center, National University of Singapore, Singapore, 117542
| | | | | | | | | | | |
Collapse
|
10
|
Avsar A, Tan JY, Taychatanapat T, Balakrishnan J, Koon G, Yeo Y, Lahiri J, Carvalho A, Rodin AS, O’Farrell E, Eda G, Castro Neto AH, Özyilmaz B. Spin–orbit proximity effect in graphene. Nat Commun 2014; 5:4875. [DOI: 10.1038/ncomms5875] [Citation(s) in RCA: 350] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 07/31/2014] [Indexed: 01/13/2023] Open
|
11
|
Saha S, Kahya O, Jaiswal M, Srivastava A, Annadi A, Balakrishnan J, Pachoud A, Toh CT, Hong BH, Ahn JH, Venkatesan T, Özyilmaz B. Unconventional transport through graphene on SrTiO₃: a plausible effect of SrTiO₃ phase-transitions. Sci Rep 2014; 4:6173. [PMID: 25146230 PMCID: PMC4141260 DOI: 10.1038/srep06173] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 08/05/2014] [Indexed: 11/25/2022] Open
Abstract
High-k dielectric oxides are supposedly ideal gate-materials for ultra-high doping in graphene and other 2D-crystals. Here, we report a temperature-dependent electronic transport study on chemical vapor deposited-graphene gated with SrTiO3 (STO) thin film substrate. At carrier densities away from charge neutrality point the temperature-dependent resistivity of our graphene samples on both STO and SiO2/Si substrates show metallic behavior with contributions from Coulomb scattering and flexural phonons attributable to the presence of characteristic quasi-periodic nano-ripple arrays. Significantly, for graphene samples on STO substrates we observe an anomalous ‘slope-break' in the temperature-dependent resistivity for T = 50 to 100 K accompanied by a decrease in mobility above 30 K. Furthermore, we observe an unusual decrease in the gate-induced doping-rate at low temperatures, despite an increase in dielectric constant of the substrate. We believe that a complex mechanism is at play as a consequence of the structural phase transition of the underlying substrate showing an anomalous transport behavior in graphene on STO. The anomalies are discussed in the context of Coulomb as well as phonon scattering.
Collapse
Affiliation(s)
- Surajit Saha
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore [3]
| | - Orhan Kahya
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2]
| | - Manu Jaiswal
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] Graphene Research Center, National University of Singapore, Singapore 117542, Singapore [3] Department of Chemistry, National University of Singapore, Singapore 117543, Singapore [4]
| | - Amar Srivastava
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - Anil Annadi
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - Jayakumar Balakrishnan
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2]
| | - Alexandre Pachoud
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] NUS Graduate School for Integrative Sciences and Engineering (NGS), Singapore 117456, Singapore
| | - Chee-Tat Toh
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Byung-Hee Hong
- Department of Chemistry, Seoul National University, Seoul 152742, Korea
| | - Jong-Hyun Ahn
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 120749, Korea
| | - T Venkatesan
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore [3] Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
| | - Barbaros Özyilmaz
- 1] Department of Physics, National University of Singapore, Singapore 117542, Singapore [2] NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore [3] Graphene Research Center, National University of Singapore, Singapore 117542, Singapore [4] NUS Graduate School for Integrative Sciences and Engineering (NGS), Singapore 117456, Singapore
| |
Collapse
|
12
|
Yang TY, Balakrishnan J, Volmer F, Avsar A, Jaiswal M, Samm J, Ali SR, Pachoud A, Zeng M, Popinciuc M, Güntherodt G, Beschoten B, Özyilmaz B. Observation of long spin-relaxation times in bilayer graphene at room temperature. Phys Rev Lett 2011; 107:047206. [PMID: 21867039 DOI: 10.1103/physrevlett.107.047206] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2010] [Indexed: 05/27/2023]
Abstract
We report on the first systematic study of spin transport in bilayer graphene (BLG) as a function of mobility, minimum conductivity, charge density, and temperature. The spin-relaxation time τ(s) scales inversely with the mobility μ of BLG samples both at room temperature (RT) and at low temperature (LT). This indicates the importance of D'yakonov-Perel' spin scattering in BLG. Spin-relaxation times of up to 2 ns at RT are observed in samples with the lowest mobility. These times are an order of magnitude longer than any values previously reported for single-layer graphene (SLG). We discuss the role of intrinsic and extrinsic factors that could lead to the dominance of D'yakonov-Perel' spin scattering in BLG. In comparison to SLG, significant changes in the carrier density dependence of τ(s) are observed as a function of temperature.
Collapse
Affiliation(s)
- T-Y Yang
- II. Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Avsar A, Yang TY, Bae S, Balakrishnan J, Volmer F, Jaiswal M, Yi Z, Ali SR, Güntherodt G, Hong BH, Beschoten B, Özyilmaz B. Toward wafer scale fabrication of graphene based spin valve devices. Nano Lett 2011; 11:2363-2368. [PMID: 21563787 DOI: 10.1021/nl200714q] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We demonstrate injection, transport, and detection of spins in spin valve arrays patterned in both copper based chemical vapor deposition (Cu-CVD) synthesized wafer scale single layer and bilayer graphene. We observe spin relaxation times comparable to those reported for exfoliated graphene samples demonstrating that chemical vapor deposition specific structural differences such as nanoripples do not limit spin transport in the present samples. Our observations make Cu-CVD graphene a promising material of choice for large scale spintronic applications.
Collapse
Affiliation(s)
- Ahmet Avsar
- Graphene Research Center & Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Bae S, Kim H, Lee Y, Xu X, Park JS, Zheng Y, Balakrishnan J, Lei T, Kim HR, Song YI, Kim YJ, Kim KS, Ozyilmaz B, Ahn JH, Hong BH, Iijima S. Roll-to-roll production of 30-inch graphene films for transparent electrodes. Nat Nanotechnol 2010; 5:574-8. [PMID: 20562870 DOI: 10.1038/nnano.2010.132] [Citation(s) in RCA: 2965] [Impact Index Per Article: 211.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 05/28/2010] [Indexed: 05/20/2023]
Abstract
The outstanding electrical, mechanical and chemical properties of graphene make it attractive for applications in flexible electronics. However, efforts to make transparent conducting films from graphene have been hampered by the lack of efficient methods for the synthesis, transfer and doping of graphene at the scale and quality required for applications. Here, we report the roll-to-roll production and wet-chemical doping of predominantly monolayer 30-inch graphene films grown by chemical vapour deposition onto flexible copper substrates. The films have sheet resistances as low as approximately 125 ohms square(-1) with 97.4% optical transmittance, and exhibit the half-integer quantum Hall effect, indicating their high quality. We further use layer-by-layer stacking to fabricate a doped four-layer film and measure its sheet resistance at values as low as approximately 30 ohms square(-1) at approximately 90% transparency, which is superior to commercial transparent electrodes such as indium tin oxides. Graphene electrodes were incorporated into a fully functional touch-screen panel device capable of withstanding high strain.
Collapse
Affiliation(s)
- Sukang Bae
- SKKU Advanced Institute of Nanotechnology and Center for Human Interface Nano Technology, Sungkyunkwan University, Suwon 440-746, Korea
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Balakrishnan J, Ashok B. The role of Hopf bifurcation dynamics in sensory processes. J Theor Biol 2010; 265:126-35. [PMID: 20382169 DOI: 10.1016/j.jtbi.2010.04.006] [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: 07/03/2009] [Revised: 04/03/2010] [Accepted: 04/05/2010] [Indexed: 10/19/2022]
Abstract
We emphasize here the role of the Hopf bifurcation in detection of stimuli in sensory processes--we discuss in particular chemosensors. It is shown that the essential nonlinearities inherent in the signal transduction mechanism can take advantage of the noise from the environment the system is subject to, to display a highly amplified response to stimuli in a frequency-selective manner. It is shown that in the absence of any externally applied stimulus, the feedback mechanisms playing a regulatory role in the transduction mechanism can give rise, in the presence of noise, to peaks in the spectral power density, suggesting enhanced spontaneous activity in sensory cells. The power law in this spectrum is determined.
Collapse
Affiliation(s)
- J Balakrishnan
- School of Physics, University of Hyderabad, Central University P.O., Gachi Bowli, Hyderabad 500 046, India.
| | | |
Collapse
|
16
|
Ohman KVH, Hettiaratchi JPA, Ruwanpura J, Balakrishnan J, Achari G. Development of a landfill model to prioritize design and operating objectives. Environ Monit Assess 2007; 135:85-97. [PMID: 17492360 DOI: 10.1007/s10661-007-9715-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2006] [Revised: 11/10/2006] [Accepted: 11/15/2006] [Indexed: 05/15/2023]
Abstract
The application of scientifically based decision making tools to help address solid waste management issues dates back to the early 1960s. Researchers continue to use operations research tools to help optimize landfill design and operating parameters. This paper discusses the application of another type of decision making tool, the analytical hierarchy process (AHP), to address priority ranking for a number of landfill engineering design and operating objectives in developing and developed countries. In this application, the AHP is used to rank, and prioritize, economic, environmental, health and safety, legislative and public perception objectives for landfill design and operations specific to landfill distance from a community, and precipitation levels. Results from a global survey using the Delphi process are included, with a discussion on the survey's impact on the objective rankings relative to community proximity and precipitation. The Delphi process worked extremely well, and was an excellent tool to use in this application. The initial results from the objective rankings show promise in the development of an integrated model for landfill design and operation.
Collapse
Affiliation(s)
- K V H Ohman
- Department of Civil Engineering, University of Calgary, Calgary, AB, Canada
| | | | | | | | | |
Collapse
|
17
|
Heine DR, Rammohan AR, Balakrishnan J. Atomistic simulations of the interaction between lipid bilayers and substrates. Molecular Simulation 2007. [DOI: 10.1080/08927020601154124] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
18
|
Balakrishnan J. Geometric framework for phase synchronization in coupled noisy nonlinear systems. Phys Rev E Stat Nonlin Soft Matter Phys 2006; 73:036206. [PMID: 16605630 DOI: 10.1103/physreve.73.036206] [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] [Subscribe] [Scholar Register] [Received: 10/12/2005] [Indexed: 05/08/2023]
Abstract
A geometric approach is introduced for understanding the phenomenon of phase synchronization in coupled nonlinear systems in the presence of additive noise. We show that the emergence of cooperative behavior through a change of stability via a Hopf bifurcation entails the spontaneous appearance of a gauge structure in the system, arising from the evolution of the slow dynamics, but induced by the fast variables. The conditions for the oscillators to be synchronised in phase are obtained. The role of weak noise appears to be to drive the system towards a more synchronized behavior. Our analysis provides a framework to explain recent experimental observations on noise-induced phase synchronization in coupled nonlinear systems.
Collapse
Affiliation(s)
- J Balakrishnan
- Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, Postbus 9506, 2300 RA Leiden, The Netherlands.
| |
Collapse
|
19
|
|
20
|
Abstract
Group theoretical concepts are invoked in a specific model to explain how only twenty amino acids occur in nature out of a possible sixty four. The methods we use enable us to justify the occurrence of the recently discovered 21st amino acid selenocysteine, and also enables us to predict the possible existence of two more, as yet undiscovered amino acids.
Collapse
Affiliation(s)
- J Balakrishnan
- CSIR Centre for Mathematical Modelling and Computer Simulation (C-MMACS), NAL Wind Tunnel Road, Bangalore-560 037, India.
| |
Collapse
|
21
|
Fokstuen S, Hobi C, Balakrishnan J, Kotzot D, Hergersberg M. Homozygosity of the cystic fibrosis (CF) gene allele IVS8-(5T) in a Tamil male with congenital bilateral absence of the vas deferens (CBAVD). Mol Hum Reprod 2000; 6:669-70. [PMID: 10871656 DOI: 10.1093/molehr/6.7.669] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
22
|
Balakrishnan J. Spatial curvature effects on molecular transport by diffusion. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 61:4648-51. [PMID: 11088274 DOI: 10.1103/physreve.61.4648] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/1999] [Revised: 11/10/1999] [Indexed: 11/07/2022]
Abstract
For a substance diffusing on a curved surface, we obtain an explicit relation valid for very small values of the time, between the local concentration, the diffusion coefficient, the intrinsic spatial curvature, and the time. We recover the known solution of Fick's law of diffusion in the flat space limit. In the biological context, this result would be useful in understanding the variations in the diffusion rates of integral proteins and other molecules on membranes.
Collapse
Affiliation(s)
- J Balakrishnan
- Department of High Voltage Engineering, Indian Institute of Science, Bangalore, 560 012, India.
| |
Collapse
|
23
|
Hergersberg M, Balakrishnan J, Bettecken T, Chevalier-Porst F, Brägger C, Burger R, Einschenk I, Liechti-Gallati S, Morris M, Schorderet D, Thonney F, Moser H, Malik N. A new mutation, 3905insT, accounts for 4.8% of 1173 CF chromosomes in Switzerland and causes a severe phenotype. Hum Genet 1997; 100:220-3. [PMID: 9254853 DOI: 10.1007/s004390050494] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have analysed 1173 cystic fibrosis (CF) chromosomes from Switzerland for eight mutations in the CF transmembrane conductance regulator (CFTR) gene. This permitted the identification of 88.5% of all mutations present. A novel insertion mutation in exon 20 of the CFTR gene, 3905insT, was discovered. This mutation accounted for 4.8% of CFTR gene mutations in Switzerland and has since been identified in other populations of probable Swiss descent. It is associated with a highly variable clinical phenotype but always with pancreatic insufficiency. Haplotype analysis with three intragenic microsatellites in the CFTR gene showed that the mutation is associated with a haplotype rarely identified on other CFTR alleles and, therefore, that the frequency of the mutation in Switzerland is explained by a founder effect of a relatively recent mutation event.
Collapse
Affiliation(s)
- M Hergersberg
- Institut für Medizinische Genetik, Universität Zürich, Switzerland.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
|
25
|
Balakrishnan J, Toms DJ. Gauge-independent effective potential for minimally coupled quantum fields in curved space. Phys Rev D Part Fields 1992; 46:4413-4420. [PMID: 10014820 DOI: 10.1103/physrevd.46.4413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
26
|
Balakrishnan J, Becker PS, Kumar AJ, Zinreich SJ, McArthur JC, Bryan RN. Acquired immunodeficiency syndrome: correlation of radiologic and pathologic findings in the brain. Radiographics 1990; 10:201-15. [PMID: 2326512 DOI: 10.1148/radiographics.10.2.2326512] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The appearance on magnetic resonance (MR) and computed tomographic (CT) images of specific central nervous system disorders associated with acquired immunodeficiency syndrome in 12 cases was correlated with autopsy findings. There were three cases of human immunodeficiency virus (HIV) encephalopathy; three, primary lymphoma; three, toxoplasmosis; one, cryptococcosis; one, cytomegalovirus infection; and one, progressive multifocal leukoencephalopathy. MR imaging demonstrated the various cranial lesions more clearly than did CT. On the basis of MR imaging characteristics, HIV encephalopathy could be distinguished from other lesions, particularly progressive multifocal leukoencephalopathy. Basal ganglia were the most common sites of involvement in opportunistic infections and primary lymphoma. Reliable distinguishing features among lesions of the basal ganglia were not found, except for cryptococcal lesions, which had a unique appearance.
Collapse
Affiliation(s)
- J Balakrishnan
- Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins Medical Institutions, Baltimore, MD 21205
| | | | | | | | | | | |
Collapse
|
27
|
Yousem DM, Balakrishnan J, Debrun GM, Bryan RN. Hyperintense thrombus on GRASS MR images: potential pitfall in flow evaluation. AJNR Am J Neuroradiol 1990; 11:51-8. [PMID: 2105617 PMCID: PMC8332476] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Gradient-recalled acquisition in the steady state (GRASS) MR images, obtained in four patients with angiographic evidence of successful occlusion of cerebral arteriovenous malformations, demonstrated hyperintense signal intraluminally. Although this was initially mistaken as evidence of persistent blood flow in the arteriovenous malformation, the short TR/TE spin-echo images showed hyperintense signal rather than flow void, thereby indicating the presence of subacute thrombus. GRASS images alone should not be used to determine the success of embolotherapy of cerebral arteriovenous malformations or to determine aneurysm patency, since the hyperintense signal is a potential pitfall that may mislead the radiologist in the absence of corroborative images, particularly the short TR/TE spin-echo sequences.
Collapse
Affiliation(s)
- D M Yousem
- Neuroradiology Division, Johns Hopkins Hospital, Baltimore, MD 21205
| | | | | | | |
Collapse
|
28
|
McArthur JC, Becker PS, Parisi JE, Trapp B, Selnes OA, Cornblath DR, Balakrishnan J, Griffin JW, Price D. Neuropathological changes in early HIV-1 dementia. Ann Neurol 1989; 26:681-4. [PMID: 2817844 DOI: 10.1002/ana.410260516] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Early pathological abnormalities in human immunodeficiency virus (HIV-1)-related dementia have not been well documented. We report a homosexual man with fatigue and intermittent diarrhea in whom early HIV-1-related dementia was demonstrated during neurological screening in the Multicenter AIDS Cohort Study. Within 4 months he died of massive epistaxis, and the brain revealed astrocytosis of white matter and mild pallor of myelin staining in the absence of inflammation, multinucleated giant cells, and brain atrophy.
Collapse
Affiliation(s)
- J C McArthur
- Johns Hopkins Medical Institutions, Baltimore, MD
| | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Balakrishnan J, Meziane MA, Siegelman SS, Fishman EK. Pulmonary infarction: CT appearance with pathologic correlation. J Comput Assist Tomogr 1989; 13:941-5. [PMID: 2584503] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The CT appearance of 12 proven pulmonary infarcts in 10 patients was analyzed and correlated with pathologic appearance. The diagnosis of pulmonary infarction was clinically suspected in only 2 of the 10 patients. A pleural based parenchymal density with convex, bulging borders and linear strands directed from the apex of the density toward the hilum was noted in each case (n = 12). Other features were a truncated apex (n = 10), a broad pleural base (n = 10), and scattered areas of reduced attenuation within the lesions (n = 7). This distinctive complex of findings on CT should raise a strong suspicion of pulmonary infarction.
Collapse
Affiliation(s)
- J Balakrishnan
- Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins Medical Institutions, Baltimore, MD 21205
| | | | | | | |
Collapse
|
30
|
Pierpaoli W, Balakrishnan J, Maestroni GJ, Sache E, Choay J. Bone marrow: a "morphostatic brain" for control of normal and neoplastic growth. Experimental evidence. Ann N Y Acad Sci 1988; 521:300-11. [PMID: 3377367 DOI: 10.1111/j.1749-6632.1988.tb35287.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- W Pierpaoli
- Institute for Integrative Biomedical Research, Ebmatingen, Switzerland
| | | | | | | | | |
Collapse
|
31
|
Balakrishnan J, Biswas SN, Goyal A, Soni SK. Chiral anomaly for parafermions from stochastic quantization. Phys Rev D Part Fields 1988; 37:571-573. [PMID: 9958718 DOI: 10.1103/physrevd.37.571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
32
|
Pierpaoli W, Balakrishnan J, Sache E, Choay J, Maestroni GJ. Neuroendocrine and bone marrow factors for control of marrow transplantation and tissue regeneration. Ann N Y Acad Sci 1987; 496:27-38. [PMID: 3300470 DOI: 10.1111/j.1749-6632.1987.tb35743.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|