Theoretical Study of One-dimensional Chains of Metal Atoms in Nanotubes

Using first-principles total-energy pseudopotential calculations, we have studied the properties of chains of potassium and aluminum in nanotubes. For BN tubes, there is little interaction between the metal chains and the tubes, and the conductivity of these tubes is through carriers located at the inner part of the tube. In contrast, for small radius carbon nanotubes, there are two types of interactions: charge-transfer (dominant for alkali atoms) leading to strong ionic cohesion, and hybridization (for multivalent metal atoms) resulting in a smaller cohesion. For Al-atomic chains in carbon tubes, we show that both effects contribute. New electronic properties related to these confined atomic chains of metal are analyzed.Comment: 12 pages + 3 figure

Quantum Correlated Interstitials and the Hall Resistivity of the Magnetically Induced Wigner Crystal

We study a trial wavefunction for an interstitial in a Wigner crystal. We find that the electron correlations, ignored in a conventional Hartree-Fock treatment, dramatically lower the interstitial energy, especially at fillings close to an incompressible liquid state. The correlation between the interstitial electron and the lattice electrons at $\nu <1/m$ is introduced by constructing a trial wave- function which bears a Jastrow factor of a Laughlin state at $\nu=1/m$. For fillings close to but just below $\nu=1/m$, we find that a perfect Wigner crystal becomes unstable against formation of such interstitials. It is argued that conduction due to correlated interstitials in the presence of weak disorder leads to the {\it classical} Hall resistivity, as seen experimentally.Comment: 10 pages, RevTe

Nonlinear Optical studies of the Transient Coherence in the Quantum Hall System

We review recent investigations of the femtosecond non-linear optical response of the two-dimensional electron gas (2DEG) in a strong magnetic field. We probe the Quantum Hall (QH) regime for filling factors $\nu \sim 1$. Our focus is on the transient coherence induced via optical excitation and on its time evolution during early femtosecond timescales. We simultaneously study the interband and intraband coherence in this system by using a nonlinear spectroscopic technique, transient three-pulse four wave mixing optical spectroscopy, and a many-body theory. We observe striking differences in the temporal and spectral profile of the nonlinear optical signal between a modulation doped quantum well system (with the 2DEG) and a similar undoped quantum well (without a 2DEG). We attribute these qualitative differences to Coulomb correlations between the photoexcited electron-hole pairs and the 2DEG. We show, in particular, that intraband many-particle coherences assisted by the inter-Landau-level magnetoplasmon excitations of the 2DEG dominate the femtosecond nonlinear optical responce. The most striking effect of these exciton-magnetoplasmon coherences is a large off-resonant four-wave-mixing signal in the case of very low photoexcited carrier densities, not observed in the undoped system, with strong temporal oscillations and unusually symmetric temporal profile.Comment: 22 pages, 9 figures; review article to be published in Solid State Communication

Altered levels of blood proteins in Alzheimer\u27s disease longitudinal study: Results from Australian Imaging Biomarkers Lifestyle Study of Ageing cohort

Introduction A blood-based biomarker panel to identify individuals with preclinical Alzheimer\u27s disease (AD) would be an inexpensive and accessible first step for routine testing. Methods We analyzed 14 biomarkers that have previously been linked to AD in the Australian Imaging Biomarkers lifestyle longitudinal study of aging cohort. Results Levels of apolipoprotein J (apoJ) were higher in AD individuals compared with healthy controls at baseline and 18 months (P =.0003) and chemokine-309 (I-309) were increased in AD patients compared to mild cognitive impaired individuals over 36 months (P =.0008). Discussion These data suggest that apoJ may have potential in the context of use (COU) of AD diagnostics, I-309 may be specifically useful in the COU of identifying individuals at greatest risk for progressing toward AD. This work takes an initial step toward identifying blood biomarkers with potential use in the diagnosis and prognosis of AD and should be validated across other prospective cohorts. © 2017 The Author

GWAS of QRS duration identifies new loci specific to Hispanic/Latino populations

Background The electrocardiographically quantified QRS duration measures ventricular depolarization and conduction. QRS prolongation has been associated with poor heart failure prognosis and cardiovascular mortality, including sudden death. While previous genome-wide association studies (GWAS) have identified 32 QRS SNPs across 26 loci among European, African, and Asian-descent populations, the genetics of QRS among Hispanics/Latinos has not been previously explored. Methods We performed a GWAS of QRS duration among Hispanic/Latino ancestry populations (n = 15,124) from four studies using 1000 Genomes imputed genotype data (adjusted for age, sex, global ancestry, clinical and study-specific covariates). Study-specific results were combined using fixed-effects, inverse variance-weighted meta-analysis. Results We identified six loci associated with QRS (P&lt;5x10-8), including two novel loci: MYOCD, a nuclear protein expressed in the heart, and SYT1, an integral membrane protein. The top SNP in the MYOCD locus, intronic SNP rs16946539, was found in Hispanics/Latinos with a minor allele frequency (MAF) of 0.04, but is monomorphic in European and African descent populations. The most significant QRS duration association was with intronic SNP rs3922344 (P = 1.19x10-24) in SCN5A/SCN10A. Three other previously identified loci, CDKN1A, VTI1A, and HAND1, also exceeded the GWAS significance threshold among Hispanics/Latinos. A total of 27 of 32 previously identified QRS duration SNPs were shown to generalize in Hispanics/Latinos. Conclusions Our QRS duration GWAS, the first in Hispanic/Latino populations, identified two new loci, underscoring the utility of extending large scale genomic studies to currently under-examined populations

Corporate characteristics and stock prices : evidence from listed companies in the Philippines

A company\u27s stock can be an indicator of how well or bad a company is performing in the market. Because of this, companies plan their actions and movements comprehensively in order to obtain a higher stock price. These would also include determining the factors, which could influence the movements of the stock price. The study explored the effects of corporate governance, disclosure compliance, firm size, and firm tenure on the change in stock price among publicly listed companies in the Philippines during the years 2008 – 2012. To accomplish this, the researchers made use of panel data regression with corporate governance, disclosure compliance, firm size, and firm tenure as independent variables and the change in stock price as the dependent variable to highlight the relationship and impact of the various independent variables on the stock price. The result showed that the disclosure compliance, the number of board of directors and the total assets of the company do not significantly affect the publicly listed companies’ change in stock price. Nonetheless, market capitalization, ratio of outside to total number of board of directors, and firm tenure exhibits significant impact on companies’ change in stock price. By being able to point out which factors would positively affect stock prices, management would be to plan their actions and movements more comprehensively in order to be able to create more opportunities that could increase the company’s stock price