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Nat Commun ; 9(1): 2776, 2018 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-30018365


Competition between liquid and solid states in two-dimensional electron systems is an intriguing problem in condensed matter physics. We have investigated competing Wigner crystal and fractional quantum Hall (FQH) liquid phases in atomically thin suspended graphene devices in Corbino geometry. Low-temperature magnetoconductance and transconductance measurements along with IV characteristics all indicate strong charge density dependent modulation of electron transport. Our results show unconventional FQH phases which do not fit the standard Jain's series for conventional FQH states, instead they appear to originate from residual interactions of composite fermions in partially filled Landau levels. Also at very low charge density with filling factors [Formula: see text], electrons crystallize into an ordered Wigner solid which eventually transforms into an incompressible Hall liquid at filling factors around ν ≤ 1/7. Building on the unique Corbino sample structure, our experiments pave the way for enhanced understanding of the ordered phases of interacting electrons.

Sci Rep ; 8(1): 594, 2018 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-29330431


We have investigated tunneling current through a suspended graphene Corbino disk in high magnetic fields at the Dirac point, i.e. at filling factor ν = 0. At the onset of the dielectric breakdown the current through the disk grows exponentially before ohmic behaviour, but in a manner distinct from thermal activation. We find that Zener tunneling between Landau sublevels dominates, facilitated by tilting of the source-drain bias potential. According to our analytic modelling, the Zener tunneling is strongly affected by the gyrotropic force (Lorentz force) due to the high magnetic field.

Rev Sci Instrum ; 88(9): 093903, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28964189


Shot noise measurements on atomic and molecular junctions provide rich information about the quantum transport properties of the junctions and on the inelastic scattering events taking place in the process. Dissipation at the nanoscale, a problem of central interest in nano-electronics, can be studied in its most explicit and simplified form. Here, we describe a measurement technique that permits extending previous noise measurements to a much higher frequency range, and to much higher bias voltage range, while maintaining a high accuracy in noise and conductance. We also demonstrate the advantages of having access to the spectral information for diagnostics.

J Microbiol ; 50(4): 603-12, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22923108


The present study searched for potential probiotic strains from various human fecal samples. A total of 67 aerobic and 38 anaerobic strains were isolated from 5 different categories of human feces. Systematic procedures were used to evaluate the probiotic properties of the isolated strains. These showed about 75-97% survivability in acidic and bile salt environments. Adhesion to intestinal cell line Caco-2 was also high. The isolates exhibited hydrophobic properties in hexadecane. The culture supernatants of these strains showed antagonistic effects against pathogens. The isolates were resistant to a simulated gastrointestinal environment in vitro. Of the 4 best isolates, MAbB4 (Staphylococcus succinus) and FIdM3 (Enterococcus fecium), were promising candidates for a potential probiotic. S. succinus was found to be a probiotic strain, which is the second such species reported to date in this particular genus. A substantial zone of inhibition was found against Salmonella spp., which adds further support to the suggestion that the probiotic strain could help prevent intestinal infection. This study suggested that the human flora itself is a potential source of probiotics.

Bactérias/isolamento & purificação , Fezes/microbiologia , Probióticos/isolamento & purificação , Ácidos/toxicidade , Adulto , Antibiose , Bactérias/classificação , Bactérias/genética , Adesão Celular , Criança , Pré-Escolar , DNA Bacteriano/química , DNA Bacteriano/genética , Tolerância a Medicamentos , Células Epiteliais/microbiologia , Feminino , Experimentação Humana , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Gravidez , Análise de Sequência de DNA
Phys Rev Lett ; 108(14): 146602, 2012 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-22540815


We present shot noise measurements on Au nanowires showing very pronounced vibration-mode features. In accordance to recent theoretical predictions the sign of the inelastic signal, i.e., the signal due to vibration excitations, depends on the transmission probability becoming negative below a certain transmission value. We argue that the negative contribution to noise arises from coherent two-electron processes mediated by electron-phonon scattering and the Pauli exclusion principle. These signals can provide unique information on the local phonon population and lattice temperature of the nanoscale system.

J Neurol Sci ; 315(1-2): 72-6, 2012 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-22177087


Aspirin is the most commonly used antiplatelet drug for treatment of a serious vascular event, most notably myocardial infarction and stroke. Significant fraction of aspirin treated patients is resistant to the antiplatelet effects of the drugs. Previous studies have suggested that a genetic basis for aspirin resistance exists. Therefore the present study was taken up to investigate the role of C3435T polymorphism (rs 1045642) of multiple drug resistance-1 (MDR-1) gene with aspirin resistance in stroke patients. Five hundred and sixty ischemic stroke patients and 560 age and sex matched healthy controls were involved in the study. Baseline clinical data were collected and follow-up telephone interviews were conducted with patients at 3, 6 and 12 months post event to determine stroke outcome. Blood samples were collected and genotypes determined. Significant difference was observed in the genotype distribution and allele frequency between patients and controls. The results were confirmed by a step wise multiple logistic regression analysis controlling all other confounding risk factors [adjusted Odds ratio=3.132 (95% CI; 2.043-4.800; p<0.001)]. There was a significant difference in genotype distribution between drug responders and non-responders. The risk of aspirin resistance was significantly high in patients with TT genotype in comparison to those with CC genotype [(TT vs. CC, χ(2)=6.268; p=0.012, Odds ratio=1.85) (95% CI; 1.142-3.017) (adjusted Odds ratio=2.465; 95% CI; 1.895-4.625 and p<0.001)]. As far as the stroke subtypes are concerned TT genotype associated significantly with aspirin resistance in intracranial large artery atherosclerosis. Our results indicate that the risk of aspirin resistance is more in patients with 3435TT genotype than in those with CC genotype. However, this is a preliminary study and a large study of replication is needed to confirm our results.

Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Aspirina/uso terapêutico , Isquemia Encefálica/genética , Resistência a Medicamentos/genética , Polimorfismo Genético/genética , Acidente Vascular Cerebral/genética , Subfamília B de Transportador de Cassetes de Ligação de ATP , Adulto , Idoso , Isquemia Encefálica/classificação , Isquemia Encefálica/prevenção & controle , Feminino , Seguimentos , Estudos de Associação Genética/métodos , Humanos , Masculino , Pessoa de Meia-Idade , Acidente Vascular Cerebral/classificação , Acidente Vascular Cerebral/prevenção & controle