1,009 research outputs found
Critical Behavior in Doping-Driven MetalInsulator Transition on Single-Crystalline Organic Mott-FET
We present the carrier transport properties in the vicinity of a
doping-driven Mott transition observed at a field-effect transistor (FET)
channel using a single crystal of the typical two-dimensional organic Mott
insulator -(BEDT-TTF)CuN(CN)Cl (-Cl).The FET shows a
continuous metalinsulator transition (MIT) as electrostatic doping proceeds.
The phase transition appears to involve two-step crossovers, one in Hall
measurement and the other in conductivity measurement. The crossover in
conductivity occurs around the conductance quantum , and hence is not
associated with "bad metal" behavior, which is in stark contrast to the MIT in
half-filled organic Mott insulators or that in doped inorganic Mott insulators.
Through in-depth scaling analysis of the conductivity, it is found that the
above carrier transport properties in the vicinity of the MIT can be described
by a high-temperature Mott quantum critical crossover, which is theoretically
argued to be a ubiquitous feature of various types of Mott transitions. [This
document is the unedited Authors' version of a Submitted Work that was
subsequently accepted for publication in Nano Letters, copyright \copyright
American Chemical Society after peer review. To access the final edited and
published work see http://dx.doi.org/10.1021/acs.nanolett.6b03817]Comment: 40 pages, 16 figures in Nano Letters, ASAP (2017
Cubic lead perovskite PbMoO3 with anomalous metallic behavior
A previously unreported Pb-based perovskite PbMoO is obtained by
high-pressure and high-temperature synthesis. This material crystallizes in the
cubic structure at room temperature, making it distinct from
typical Pb-based perovskite oxides with a structural distortion. PbMoO
exhibits a metallic behavior down to 0.1 K with an unusual -sub linear
dependence of the electrical resistivity. Moreover, a large specific heat is
observed at low temperatures accompanied by a peak in around 10 K, in
marked contrast to the isostructural metallic system SrMoO. These transport
and thermal properties for PbMoO, taking into account anomalously large Pb
atomic displacements detected through diffraction experiments, are attributed
to a low-energy vibrational mode, associated with incoherent off-centering of
lone pair Pb cations. We discuss the unusual behavior of the electrical
resistivity in terms of a polaron-like conduction, mediated by the strong
coupling between conduction electrons and optical phonons of the local
low-energy vibrational mode.Comment: 5 pages, 5 figure
Asymptotic analysis of the model for distribution of high-tax payers
The z-transform technique is used to investigate the model for distribution
of high-tax payers, which is proposed by two of the authors (K. Y and S. M) and
others. Our analysis shows an asymptotic power-law of this model with the
exponent -5/2 when a total ``mass'' has a certain critical value. Below the
critical value, the system exhibits an ordinary critical behavior, and scaling
relations hold. Above the threshold, numerical simulations show that a
power-law distribution coexists with a huge ``monopolized'' member. It is
argued that these behaviors are observed universally in conserved aggregation
processes, by analizing an extended model.Comment: 5pages, 3figure
Field-induced carrier delocalization in the strain-induced Mott insulating state of an organic superconductor
We report the influence of the field effect on the dc resistance and Hall
coefficient in the strain-induced Mott insulating state of an organic
superconductor -(BEDT-TTF)Cu[N(CN)]Br. Conductivity obeys
the formula for activated transport , where is a constant and depends on
the gate voltage. The gate voltage dependence of the Hall coefficient shows
that, unlike in conventional FETs, the effective mobility of dense hole
carriers ( cm) is enhanced by a positive gate
voltage. This implies that carrier doping involves delocalization of intrinsic
carriers that were initially localized due to electron correlation.Comment: 5 pages, 3 figure
Transcriptional control of glyoxalase 1 by Nrf2 provides a stress-responsive defence against dicarbonyl glycation
Abnormal cellular accumulation of the dicarbonyl metabolite MG (methylglyoxal) occurs on exposure to high glucose concentrations, inflammation, cell aging and senescence. It is associated with increased MG-adduct content of protein and DNA linked to increased DNA strand breaks and mutagenesis, mitochondrial dysfunction and ROS (reactive oxygen species) formation and cell detachment from the extracellular matrix. MG-mediated damage is countered by glutathione-dependent metabolism by Glo1 (glyoxalase 1). It is not known, however, whether Glo1 has stress-responsive up-regulation to counter periods of high MG concentration or dicarbonyl stress. We identified a functional ARE (antioxidant-response element) in the 5'-untranslated region of exon 1 of the mammalian Glo1 gene. Transcription factor Nrf2 (nuclear factor-erythroid 2 p45 subunit-related factor 2) binds to this ARE, increasing basal and inducible expression of Glo1. Activators of Nrf2 induced increased Glo1 mRNA, protein and activity. Increased expression of Glo1 decreased cellular and extracellular concentrations of MG, MG-derived protein adducts, mutagenesis and cell detachment. Hepatic, brain, heart, kidney and lung Glo1 mRNA and protein were decreased in Nrf2-/- mice, and urinary excretion of MG protein and nucleotide adducts were increased approximately 2-fold. We conclude that dicarbonyl stress is countered by up-regulation of Glo1 in the Nrf2 stress-responsive system, protecting protein and DNA from increased damage and preserving cell function
Transgenic amplification of glucocorticoid action in adipose tissue causes high blood pressure in mice
Obesity is closely associated with the metabolic syndrome, a combination of disorders including insulin resistance, diabetes, dyslipidemia, and hypertension. A role for local glucocorticoid reamplification in obesity and the metabolic syndrome has been suggested. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) regenerates active cortisol from inactive 11-keto forms, and aP2-HSD1 mice with relative transgenic overexpression of this enzyme in fat cells develop visceral obesity with insulin resistance and dyslipidemia. Here we report that aP2-HSD1 mice also have high arterial blood pressure (BP). The mice have increased sensitivity to dietary salt and increased plasma levels of angiotensinogen, angiotensin II, and aldosterone. This hypertension is abolished by selective angiotensin II receptor AT-1 antagonist at a low dose that does not affect BP in non-Tg littermates. These findings suggest that activation of the circulating renin-angiotensin system (RAS) develops in aP2-HSD1 mice. The long-term hypertension is further reflected by an appreciable hypertrophy and hyperplasia of the distal tubule epithelium of the nephron, resembling salt-sensitive or angiotensin II–mediated hypertension. Taken together, our findings suggest that overexpression of 11β-HSD1 in fat is sufficient to cause salt-sensitive hypertension mediated by an activated RAS. The potential role of adipose 11β-HSD1 in mediating critical features of the metabolic syndrome extends beyond obesity and metabolic complications to include the most central cardiovascular feature of this disorder
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