4,682 research outputs found
Biomarkers for Aging
A statistical and functional correlation strategy to identify changes in cellular pathways specifically linked to impaired cognitive function with aging. Analyses using the strategy identified multiple groups of genes expressed in the hippocampi of mammals, where the genes were expressed at different levels for several ages. The aging changes in expression began before mid-life. Many of the genes were involved in specific neuronal and glial pathways with previously unrecognized relationships to aging and/or cognitive decline. These identified genes and the proteins they encode can be used as novel biomarkers of brain aging and as targets for developing treatment methods against age-related cognitive decline, Alzheimer\u27s Disease and Parkinson\u27s Disease
Boilerplate and Party Intent
In this work we examined optical and defect properties of as-grown and Ni-coated ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition by means of optically detected magnetic resonance (ODMR). Several grown-in defects are revealed by monitoring visible photoluminescence (PL) emissions and are attributed to Zn vacancies, O vacancies, a shallow (but not effective mass) donor and exchange-coupled pairs of a Zn vacancy and a Zn interstitial. It is also found that the same ODMR signals are detected in the as-grown and Ni-coated NWs, indicating that metal coatings does not significantly affect formation of the aforementioned defects and that the observed defects are located in the bulk of the NWs
Coulomb interactions at quantum Hall critical points of systems in a periodic potential
We study the consequences of long-range Coulomb interactions at the critical
points between integer/fractional quantum Hall states and an insulator. We use
low energy theories for such transitions in anyon gases in the presence of an
external periodic potential. We find that Coulomb interactions are marginally
irrelevant for the integer quantum Hall case. For the fractional case,
depending upon the anyon statistics parameter, we find behavior similar to the
integer case, or flow to a novel line of fixed points with exponents ,
stable against weak disorder in the position of the critical point,
or run-away flow to strong coupling.Comment: 12 pages, REVTEX, 1 figur
Ferromagnetism in Diluted Magnetic Semiconductor Heterojunction Systems
Diluted magnetic semiconductors (DMSs), in which magnetic elements are
substituted for a small fraction of host elements in a semiconductor lattice,
can become ferromagnetic when doped. In this article we discuss the physics of
DMS ferromagnetism in systems with semiconductor heterojunctions. We focus on
the mechanism that cause magnetic and magnetoresistive properties to depend on
doping profiles, defect distributions, gate voltage, and other system
parameters that can in principle be engineered to yield desired results.Comment: 12 pages, 7 figures, review, special issue of Semicon. Sci. Technol.
on semiconductor spintronic
The effects of weak disorders on Quantum Hall critical points
We study the consequences of random mass, random scalar potential and random
vector potential on the line of clean fixed points between integer/fractional
quantum Hall states and an insulator. This line of fixed points was first
identified in a clean Dirac fermion system with both Chern-Simon coupling and
Coulomb interaction in Phys. Rev. Lett. {\bf 80}, 5409 (1998). By performing a
Renormalization Group analysis in 1/N (N is the No. of species of Dirac
fermions) and the variances of three disorders , we find that is irrelevant along this line, both
and are marginal. With the presence of all the three
disorders, the pure fixed line is unstable. Setting Chern-Simon interaction to
zero, we find one non-trivial line of fixed points in plane
with dynamic exponent z=1 and continuously changing , it is stable against
small in a small range of the line ,
therefore it may be relevant to integer quantum Hall transition. Setting
, we find a fixed plane with z=1, the part of this plane with
is stable against small , therefore it may be relevant to
fractional quantum Hall transition.Comment: 16 pages, 19 figure
Spin- and charge-density waves in the Hartree-Fock ground state of the two-dimensional Hubbard model
The ground states of the two-dimensional repulsive Hubbard model are studied
within the unrestricted Hartree-Fock (UHF) theory. Magnetic and charge
properties are determined by systematic, large-scale, exact numerical
calculations, and quantified as a function of electron doping . In the
solution of the self-consistent UHF equations, multiple initial configurations
and simulated annealing are used to facilitate convergence to the global
minimum. New approaches are employed to minimize finite-size effects in order
to reach the thermodynamic limit. At low to moderate interacting strengths and
low doping, the UHF ground state is a linear spin-density wave (l-SDW), with
antiferromagnetic order and a modulating wave. The wavelength of the modulating
wave is . Corresponding charge order exists but is substantially weaker
than the spin order, hence holes are mobile. As the interaction is increased,
the l-SDW states evolves into several different phases, with the holes
eventually becoming localized. A simple pairing model is presented with
analytic calculations for low interaction strength and small doping, to help
understand the numerical results and provide a physical picture for the
properties of the SDW ground state. By comparison with recent many-body
calculations, it is shown that, for intermediate interactions, the UHF solution
provides a good description of the magnetic correlations in the true ground
state of the Hubbard model.Comment: 13 pages, 17 figure, 0 table
Selective production of hydrogen peroxide and oxidation of hydrogen sulfide in an unbiased solar photoelectrochemical cell
A solar-to-chemical conversion process is demonstrated using a photoelectrochemical cell without external bias for selective oxidation of hydrogen sulfide (H2S) to produce hydrogen peroxide (H2O2) and sulfur (S). The process integrates two redox couples anthraquinone/anthrahydroquinone and I−/I3−, and conceptually illustrates the remediation of a waste product for producing valuable chemicals
Gene Essentiality Profiling Reveals Gene Networks and Synthetic Lethal Interactions with Oncogenic Ras
The genetic dependencies of human cancers widely vary. Here, we catalog this heterogeneity and use it to identify functional gene interactions and genotype-dependent liabilities in cancer. By using genome-wide CRISPR-based screens, we generate a gene essentiality dataset across 14 human acute myeloid leukemia (AML) cell lines. Sets of genes with correlated patterns of essentiality across the lines reveal new gene relationships, the essential substrates of enzymes, and the molecular functions of uncharacterized proteins. Comparisons of differentially essential genes between Ras-dependent and -independent lines uncover synthetic lethal partners of oncogenic Ras. Screens in both human AML and engineered mouse pro-B cells converge on a surprisingly small number of genes in the Ras processing and MAPK pathways and pinpoint PREX1 as an AML-specific activator of MAPK signaling. Our findings suggest general strategies for defining mammalian gene networks and synthetic lethal interactions by exploiting the natural genetic and epigenetic diversity of human cancer cells. Keywords: CRISPR; AML; synthetic lethality; gene networks; RAS; genetic screensNational Institutes of Health (U.S.) (Grant CA103866)National Institutes of Health (U.S.) (Grant F31CA189437
Ectopy on a single 12‐lead ECG, incident cardiac myopathy, and death in the community
BackgroundAtrial fibrillation and heart failure are 2 of the most common diseases, yet ready means to identify individuals at risk are lacking. The 12-lead ECG is one of the most accessible tests in medicine. Our objective was to determine whether a premature atrial contraction observed on a standard 12-lead ECG would predict atrial fibrillation and mortality and whether a premature ventricular contraction would predict heart failure and mortality.Methods and resultsWe utilized the CHS (Cardiovascular Health) Study, which followed 5577 participants for a median of 12 years, as the primary cohort. The ARIC (Atherosclerosis Risk in Communities Study), the replication cohort, captured data from 15 792 participants over a median of 22 years. In the CHS, multivariable analyses revealed that a baseline 12-lead ECG premature atrial contraction predicted a 60% increased risk of atrial fibrillation (hazard ratio, 1.6; 95% CI, 1.3-2.0; P<0.001) and a premature ventricular contraction predicted a 30% increased risk of heart failure (hazard ratio, 1.3; 95% CI, 1.0-1.6; P=0.021). In the negative control analyses, neither predicted incident myocardial infarction. A premature atrial contraction was associated with a 30% increased risk of death (hazard ratio, 1.3; 95% CI, 1.1-1.5; P=0.008) and a premature ventricular contraction was associated with a 20% increased risk of death (hazard ratio, 1.2; 95% CI, 1.0-1.3; P=0.044). Similarly statistically significant results for each analysis were also observed in ARIC.ConclusionsBased on a single standard ECG, a premature atrial contraction predicted incident atrial fibrillation and death and a premature ventricular contraction predicted incident heart failure and death, suggesting that this commonly used test may predict future disease
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