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Somphonsane R, Ramamoorthy H, He G, Nathawat J, Yin S, Kwan CP, Arabchigavkani N, Barut B, Zhao M, Jin Z, Fransson J, Bird JP. Universal scaling of weak localization in graphene due to bias-induced dispersion decoherence. Sci Rep 2020; 10:5611. [PMID: 32221340 PMCID: PMC7101405 DOI: 10.1038/s41598-020-62313-3] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 03/11/2020] [Indexed: 11/29/2022] Open
Abstract
The differential conductance of graphene is shown to exhibit a zero-bias anomaly at low temperatures, arising from a suppression of the quantum corrections due to weak localization and electron interactions. A simple rescaling of these data, free of any adjustable parameters, shows that this anomaly exhibits a universal, temperature- (T) independent form. According to this, the differential conductance is approximately constant at small voltages (V < kBT/e), while at larger voltages it increases logarithmically with the applied bias. For theoretical insight into the origins of this behaviour, which is inconsistent with electron heating, we formulate a model for weak-localization in the presence of nonequilibrium transport. According to this model, the applied voltage causes unavoidable dispersion decoherence, which arises as diffusing electron partial waves, with a spread of energies defined by the value of the applied voltage, gradually decohere with one another as they diffuse through the system. The decoherence yields a universal scaling of the conductance as a function of eV/kBT, with a logarithmic variation for eV/kBT > 1, variations in accordance with the results of experiment. Our theoretical description of nonequilibrium transport in the presence of this source of decoherence exhibits strong similarities with the results of experiment, including the aforementioned rescaling of the conductance and its logarithmic variation as a function of the applied voltage.
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Affiliation(s)
- R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520, Thailand.
- Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok, 10400, Thailand.
| | - H Ramamoorthy
- Department of Electronic Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520, Thailand
| | - G He
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
| | - J Nathawat
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
| | - S Yin
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
| | - C-P Kwan
- Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1500, USA
| | - N Arabchigavkani
- Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1500, USA
| | - B Barut
- Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1500, USA
| | - M Zhao
- High-Frequency High-Voltage Device and Integrated Circuits Center, Institute of Microelectronics of Chinese Academy of Sciences, 3 Beitucheng West Road, Chaoyang District, Beijing, PR China
| | - Z Jin
- High-Frequency High-Voltage Device and Integrated Circuits Center, Institute of Microelectronics of Chinese Academy of Sciences, 3 Beitucheng West Road, Chaoyang District, Beijing, PR China
| | - J Fransson
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 21, Uppsala, Sweden
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-1900, USA
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He G, Ramamoorthy H, Kwan CP, Lee YH, Nathawat J, Somphonsane R, Matsunaga M, Higuchi A, Yamanaka T, Aoki N, Gong Y, Zhang X, Vajtai R, Ajayan PM, Bird JP. Thermally Assisted Nonvolatile Memory in Monolayer MoS 2 Transistors. Nano Lett 2016; 16:6445-6451. [PMID: 27680095 DOI: 10.1021/acs.nanolett.6b02905] [Citation(s) in RCA: 17] [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] [Indexed: 06/06/2023]
Abstract
We demonstrate a novel form of thermally-assisted hysteresis in the transfer curves of monolayer MoS2 FETs, characterized by the appearance of a large gate-voltage window and distinct current levels that differ by a factor of ∼102. The hysteresis emerges for temperatures in excess of 400 K and, from studies in which the gate-voltage sweep parameters are varied, appears to be related to charge injection into the SiO2 gate dielectric. The thermally-assisted memory is strongly suppressed in equivalent measurements performed on bilayer transistors, suggesting that weak screening in the monolayer system plays a vital role in generating its strongly sensitive response to the charge-injection process. By exploiting the full features of the hysteretic transfer curves, programmable memory operation is demonstrated. The essential principles demonstrated here point the way to a new class of thermally assisted memories based on atomically thin two-dimensional semiconductors.
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Affiliation(s)
- G He
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - H Ramamoorthy
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - C-P Kwan
- Department of Physics, University at Buffalo, The State University of New York , Buffalo, New York 14260-1500, United States
| | - Y-H Lee
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - J Nathawat
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang , Bangkok 10520, Thailand
| | - M Matsunaga
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - A Higuchi
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - T Yamanaka
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - N Aoki
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Y Gong
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - X Zhang
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - R Vajtai
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - P M Ajayan
- Department of Materials Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Ramamoorthy H, Somphonsane R, Radice J, He G, Kwan CP, Bird JP. Correction to "Freeing" Graphene from Its Substrate: Observing Intrinsic Velocity Saturation with Rapid Electrical Pulsing. Nano Lett 2016; 16:1514. [PMID: 26807871 DOI: 10.1021/acs.nanolett.6b00287] [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: 06/05/2023]
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Ramamoorthy H, Somphonsane R, Radice J, He G, Kwan CP, Bird JP. "Freeing" Graphene from Its Substrate: Observing Intrinsic Velocity Saturation with Rapid Electrical Pulsing. Nano Lett 2016; 16:399-403. [PMID: 26649478 DOI: 10.1021/acs.nanolett.5b04003] [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] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Rapid (nanosecond-scale) electrical pulsing is used to study drift-velocity saturation in graphene field-effect devices. In these experiments, high-field pulses are utilized to drive graphene's carriers on time scales much faster than that on which energy loss to the underlying substrate can occur, thereby allowing the observation of the highest saturation velocities reported to date. In a dramatic departure from the behavior exhibited by conventional metals and semiconductors, as the electron or hole density is reduced toward the charge-neutrality point, the drift velocity is found to reach values comparable to the Fermi velocity itself. Corresponding current densities are as large as 10(9) A/cm(2), similar to the values reported for carbon nanotubes and for graphene-on-diamond transistors. In essence, our approach of rapid pulsing allows us to "free" graphene from the deleterious influence of its substrate, revealing a pathway to achieve the superior electrical performance promised by this material. The usefulness of this approach is not merely limited to graphene but should extend also to a broad variety of two-dimensional semiconductors.
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Affiliation(s)
- H Ramamoorthy
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
| | - R Somphonsane
- Department of Physics, King Mongkut's Institute of Technology Ladkrabang , Bangkok 10520, Thailand
| | - J Radice
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
| | - G He
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
| | - C-P Kwan
- Department of Physics, University at Buffalo, the State University of New York , Buffalo, New York 14260-1500, United States
| | - J P Bird
- Department of Electrical Engineering, University at Buffalo, the State University of New York , Buffalo, New York 14260-1900, United States
- Graduate School of Advanced Integration Science, Chiba University , 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Kwan CP, Venkataraman G, Shriver Z, Raman R, Liu D, Qi Y, Varticovski L, Sasisekharan R. Probing fibroblast growth factor dimerization and role of heparin-like glycosaminoglycans in modulating dimerization and signaling. J Biol Chem 2001; 276:23421-9. [PMID: 11292822 DOI: 10.1074/jbc.m010786200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [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: 11/06/2022] Open
Abstract
For a number of growth factors and cytokines, ligand dimerization is believed to be central to the formation of an active signaling complex. In the case of fibroblast growth factor-2 (FGF2) signaling, heparin/heparan sulfate-like glycosaminoglycans (HLGAGs) are involved through interaction with both FGF2 and its receptors (FGFRs) in assembling a tertiary complex and modulating FGF2 activity. Biochemical data have suggested different modes of HLGAG-induced FGF2 dimerization involving specific protein-protein contacts. In addition, several recent x-ray crystallography studies of FGF.FGFR and FGF.FGFR.HLGAG complexes have revealed other modes of molecular assemblage, with no FGF-FGF contacts. All these different biochemical and structural findings have clarified less and in fact raised more questions as to which mode of FGF2 dimerization, if any, is essential for signaling. In this study, we address the issue of FGF2 dimerization in signaling using a combination of biochemical, biophysical, and site-directed mutagenesis approaches. Our findings presented here provide direct evidence of FGF2 dimerization in mediating FGF2 signaling.
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Affiliation(s)
- C P Kwan
- Division of Bioengineering and Environmental Health, the Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Chau TN, Sung JJ, Kwan CP, Ng C, Lai JY, Lai TS, Yuen H. Biliary tract disease and acute non-A-E hepatitis in Hong Kong: prospective study. Hong Kong Med J 2001; 7:124-30. [PMID: 11514745] [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: 02/21/2023] Open
Abstract
OBJECTIVE To investigate the role of biliary tract disease in patients with acute non-A-E hepatitis. DESIGN Prospective study. SETTING Infectious diseases unit, government hospital, Hong Kong. PATIENTS Sixty-one consecutive patients, admitted with the diagnosis of acute hepatitis and negative hepatitis serology for hepatitis A, B, C, D, and E virus. MAIN OUTCOME MEASURES Abdominal ultrasound and endoscopic retrograde cholangiopancreatography findings; clinical outcome. RESULTS Ultrasonographic abnormalities indicating biliary tract disease were found in 30% (18/61) of patients. Endoscopic retrograde cholangiopancreatography performed in 78% (14/18) of patients with abnormal ultrasound finding(s) confirmed the presence of biliary tract disease. Age, sex, serum alanine aminotransferase level, and serum albumin level were independent predictors of biliary tract disease in the patients studied. CONCLUSION Biliary tract diseases were found in 20% of patients with acute non-A-E hepatitis. Serum amylase and abdominal ultrasonography should be performed for all patients presenting with acute non-A-E hepatitis. Endoscopic retrograde cholangiopancreatography is indicated for those with apparent gallstones or abnormal biliary tract findings.
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Affiliation(s)
- T N Chau
- Department of Medicine and Geriatrics, Princess Margaret Hospital, Kwai Chung, Hong Kong
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Berry D, Kwan CP, Shriver Z, Venkataraman G, Sasisekharan R. Distinct heparan sulfate glycosaminoglycans are responsible for mediating fibroblast growth factor-2 biological activity through different fibroblast growth factor receptors. FASEB J 2001; 15:1422-4. [PMID: 11387244 DOI: 10.1096/fj.00-0661fje] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- D Berry
- Division of Bioengineering and Environmental Health, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Martin KJ, Kritzman BM, Price LM, Koh B, Kwan CP, Zhang X, Mackay A, O'Hare MJ, Kaelin CM, Mutter GL, Pardee AB, Sager R. Linking gene expression patterns to therapeutic groups in breast cancer. Cancer Res 2000; 60:2232-8. [PMID: 10786689] [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: 02/16/2023]
Abstract
A major objective of current cancer research is to develop a detailed molecular characterization of tumor cells and tissues that is linked to clinical information. Toward this end, we have identified approximately one-quarter of all genes that were aberrantly expressed in a breast cancer cell line using differential display. The cancer cells lost the expression of many genes involved in cell adhesion, communication, and maintenance of cell shape, while they gained the expression of many synthetic and metabolic enzymes important for cell proliferation. High-density, membrane-based hybridization arrays were used to study mRNA expression patterns of these genes in cultured cells and archived tumor tissue. Cluster analysis was then used to identify groups of genes, the expression patterns of which correlated with clinical information. Two clusters of genes, represented by p53 and maspin, had expression patterns that strongly associated with estrogen receptor status. A third cluster that included HSP-90 tended to be associated with clinical tumor stage, whereas a forth cluster that included keratin 14 tended to be associated with tumor size. Expression levels of these clinically relevant gene clusters allowed breast tumors to be grouped into distinct categories. Gene expression fingerprints that include these four gene clusters have the potential to improve prognostic accuracy and therapeutic outcomes for breast cancer patients.
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Affiliation(s)
- K J Martin
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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Martin KJ, Kwan CP, Nagasaki K, Zhang X, O'Hare MJ, Kaelin CM, Burgeson RE, Pardee AB, Sager R. Down-regulation of laminin-5 in breast carcinoma cells. Mol Med 1998; 4:602-13. [PMID: 9848077 PMCID: PMC2230317] [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: 02/09/2023] Open
Abstract
BACKGROUND Laminin-5 (ln-5), a large heterotrimeric glycoprotein consisting of an alpha 3, beta 3, and gamma 2 chain, is a component of epithelial cell basement membranes that functions as a ligand of the alpha 3 beta 1 and alpha 6 beta 4 integrins to regulate cell adhesion, migration, and morphogenesis. The ln-5 chains show tissue-specific patterns of regulation in tumors derived from different tissues. For example, ln-5 is often up-regulated in gliomas, gastric carcinomas, and squamous carcinomas and down-regulated in prostate and basal cell carcinomas. Ln-5 expression patterns may represent useful tumor markers and help to elucidate the role of ln-5 in tumor progression in different tissue types. MATERIALS AND METHODS We have studied ln-5 expression patterns in the breast. mRNA levels were examined in tumor and normal breast epithelial cell lines, tissue samples, and immunomagnetically sorted primary cultures using differential display, Northern blotting, and hybridization arrays. Protein levels were examined by immunoprecipitation. Gene integrity was assessed by Southern blotting of representative cell types. RESULTS Ln-5 alpha 3, beta 3, and gamma 2 mRNA expression was found to be markedly down-regulated in a panel of breast tumor cell lines when compared with normal breast epithelial cells. Ln-5 mRNA was expressed at relatively high levels in MCF-10A immortal normal breast epithelial cells, long-term cultures of normal breast cells, and sorted primary cultures of normal breast luminal epithelial and myoepithelial cells. Reduced, but detectable, levels of ln-5 tended to be expressed in cell lines derived from early-stage breast tumors, whereas expression was generally not detected in cell lines derived from later-stage tumors. In breast tumor tissue specimens, expression of ln alpha 3 and beta 3 mRNAs tended to be reduced relative to levels observed in adjacent nontumor tissue, whereas in gamma 2 levels were elevated in specimens with increased amounts of myoepithelial cells. These ln-5 expression changes could not be attributed to large-scale mutations or gene rearrangements. Ln-5 protein levels were found to reflect mRNA levels in representative cell lines. At senescence, a growth state believed to suppress tumorigenesis, expression of all three ln-5 mRNAs was up-regulated. CONCLUSION The down-regulation of ln-5 mRNA expression in breast tumors cells provides a new molecular marker and suggests that ln-5 functions to control tumor progression in the breast.
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Affiliation(s)
- K J Martin
- Division of Cancer Genetics, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA.
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Martin KJ, Kwan CP, O'Hare MJ, Pardee AB, Sager R. Identification and verification of differential display cDNAs using gene-specific primers and hybridization arrays. Biotechniques 1998; 24:1018-26. [PMID: 9631197 DOI: 10.2144/98246cr01] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [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: 02/07/2023] Open
Abstract
An accurate and streamlined approach to differential display (DD) band identification and verification is described. To minimize false positives, the strategy avoids the use of impure Northern blot probes obtained from PCR-amplified DD bands. To increase throughput, the cloning of DD bands is replaced by a gene-specific primer approach, and hybridization arrays are used in place of Northern blots. In summary, DD bands obtained with long primers were directly sequenced to allow the design and synthesis of gene-specific primers, which were then used to PCR-amplify homogeneous probes for the verification of expression patterns by hybridization array analysis. Differential expression of 60 of the 63 genes tested was confirmed. Thus, false positives are not inherent to DD. The results demonstrate the power of DD used with hybridization arrays to rapidly generate information on expression patterns of differentially expressed genes.
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Affiliation(s)
- K J Martin
- Division of Cancer Genetics, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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Affiliation(s)
- K J Martin
- Division of Cancer Genetics, Dana-Farber Cancer Institute, Boston, MA, USA
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Abstract
The diagnosis and management of antral gastrin-(G-) cell hyperplasia was a major topic of interest in the 1970s. Following the discovery of Helicobacter pylori in the 1980s, little attention was paid to this condition until it was shown that H. pylori infection was associated with hypergastrinaemia and that eradication of the organism returned the gastrin level to normal. Recent reports have examined the relationship between H. pylori and antral G-cell hyperplasia. H. pylori infection is present in about 50% of cases of antral G-cell hyperplasia and, importantly, eradication of the organism normalizes not only the gastrin level but also the antral G-cell count. Eradication treatment should be the therapy of choice. It is also of interest that H. pylori-negative antral G-cell hyperplasia or hyperfunction does exist. The historical aspects, the relationship between antral G-cell hyperplasia and H. pylori and recent case reports are reviewed.
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Affiliation(s)
- C P Kwan
- Department of Gastroenterology and Hepatology, Academic Medical Centre, Amsterdam, Netherlands
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