2,788 research outputs found
No Association Between an Oxytocin Receptor Genetic Variant and Depressive Symptoms
âą Depression has the greatest impact on daily functioning capability of all diseases and adversely effects individuals globally (Flint & Kendler, 2014). âą Human capital value of these losses has been about $40 billion dollars annually (Kessler, 2012). âą Analysis of the genetic and biological systems associated with depressive symptoms, such as the oxytocin system, could lead to identifying risk variants and possible treatment development. âą Genetic Variation in OXTR is associated with a variation in depressive symptoms including low selfesteem, pessimism, and low self-efficacy, etc. (Conner et al., 2018). âą The A allele of the SNP rs53576 is considered the risk allele as itâs associated with decreased pro-social behavior and increased loneliness and suicide attempts (Parris et. Al., 2018) âą The exact mechanism has not been identified, but G/G homozygotes recorded to have higher oxytocin levels, associated with increased emotional responsiveness (Marsh et al., 2012; Tost et al., 2010) âą We hypothesize that: (1) individuals possessing the A allele of the rs53576 SNP of OXTR will have more depressive symptoms on average. (2) Females will have more depressive symptoms on average. (3) There is an interaction between genotype and biological sex, as A allele females will have more depressive symptoms on average
Understanding the viability of impurity-band photovoltaics : a case study of S-doped Si
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 137-149).This thesis explores the electronic structure, optical properties, and carrier lifetimes in silicon that is doped with sulfur beyond the equilibrium solid solubility limit, with a focus on applications as an absorber layer for an impurity-band photovoltaic device. The concept of an impurity-band material envisions the creation of a band of electronic states by incorporating high concentrations of deep-level dopants, which enable the generation of free carriers using photons with energy less than that of the band gap of the host semiconductor. The investigations reported in this thesis provide a framework for the appropriate selection of impurity-band candidate materials. The thesis is divided into three primary sections, one for each of three experimental techniques, respectively. First, the electronic band structure is studied using synchrotron-based x-ray emission spectroscopy. These spectra provide the first insights into how the electronic structure changes as the sulfur concentration is increased across the metal-insulator transition, and how the electronic structure is linked to the anomalously high subband gap absorption. A discrete change in local electronic structure is seen that corresponds to the macroscopic change in electronic behavior. Additionally, a direct correlation is seen between sulfur-induced states and the sub-band gap absorption. Next, the optical properties are studied using Fourier transform infrared spectroscopy. Extraction of the complex index of refraction is performed using numerical models that simulate both the transmission and reflection measurements. Analysis of the absorption coefficient determines the position of the sulfur-induced states within the band gap and their optical cross section for different sulfur concentrations and annealing conditions. At sulfur concentrations above the metal-insulator transition, the sulfur states become degenerate or near-degenerate with the conduction band, and such high concentrations are deemed to have an electronic structure unsuitable for an impurity-band photovoltaic material. Third, low-temperature photoconductivity experiments determine the mobility-lifetime product for carriers generated via sub-band gap photons. Combining both the FTIR optical results with the mobility-lifetime product measured from photoconductivity experiments provide the first empirical determination of the impurity-band figure of merit for sulfur-doped silicon. The figure of merit is found to be over an order of magnitude too low to be suitable as an impurity band absorber layer. Finally, in the conclusion, future directions and a predictive methodology for selecting new candidate impurity band materials that hold promise are discussed. The predictive methodology describes a simple way to estimate the figure of merit for super-saturated materials solely using literature values of the optical and electrical capture cross sections at dilute concentrations.by Joseph Timothy Sullivan.Ph.D
Long Lived Fourth Generation and the Higgs
A chiral fourth generation is a simple and well motivated extension of the
standard model, and has important consequences for Higgs phenomenology. Here we
consider a scenario where the fourth generation neutrinos are long lived and
have both a Dirac and Majorana mass term. Such neutrinos can be as light as 40
GeV and can be the dominant decay mode of the Higgs boson for Higgs masses
below the W-boson threshold. We study the effect of the Majorana mass term on
the Higgs branching fractions and reevaluate the Tevatron constraints on the
Higgs mass. We discuss the prospects for the LHC to detect the semi-invisible
Higgs decays into fourth generation neutrino pairs. Under the assumption that
the lightest fourth generation neutrino is stable, it's thermal relic density
can be up to 20% of the observed dark matter density in the universe. This is
in agreement with current constraints on the spin dependent neutrino-neutron
cross section, but can be probed by the next generation of dark matter direct
detection experiments.Comment: v1: 19 pages, 5 figures; v2: References added; v3: version to appear
in JHE
Left-right symmetry at LHC and precise 1-loop low energy data
Despite many tests, even the Minimal Manifest Left-Right Symmetric Model
(MLRSM) has never been ultimately confirmed or falsified. LHC gives a new
possibility to test directly the most conservative version of left-right
symmetric models at so far not reachable energy scales. If we take into account
precise limits on the model which come from low energy processes, like the muon
decay, possible LHC signals are strongly limited through the correlations of
parameters among heavy neutrinos, heavy gauge bosons and heavy Higgs particles.
To illustrate the situation in the context of LHC, we consider the "golden"
process . For instance, in a case of degenerate heavy neutrinos
and heavy Higgs masses at 15 TeV (in agreement with FCNC bounds) we get
fb at TeV which is consistent with muon
decay data for a very limited masses in the range (3008 GeV, 3040 GeV).
Without restrictions coming from the muon data, masses would be in the
range (1.0 TeV, 3.5 TeV). Influence of heavy Higgs particles themselves on the
considered LHC process is negligible (the same is true for the light, SM
neutral Higgs scalar analog). In the paper decay modes of the right-handed
heavy gauge bosons and heavy neutrinos are also discussed. Both scenarios with
typical see-saw light-heavy neutrino mixings and the mixings which are
independent of heavy neutrino masses are considered. In the second case heavy
neutrino decays to the heavy charged gauge bosons not necessarily dominate over
decay modes which include only light, SM-like particles.Comment: 16 pages, 10 figs, KL-KS and new ATLAS limits taken into accoun
Cohomological tautness for Riemannian foliations
In this paper we present some new results on the tautness of Riemannian
foliations in their historical context. The first part of the paper gives a
short history of the problem. For a closed manifold, the tautness of a
Riemannian foliation can be characterized cohomologically. We extend this
cohomological characterization to a class of foliations which includes the
foliated strata of any singular Riemannian foliation of a closed manifold
Modified differentials and basic cohomology for Riemannian foliations
We define a new version of the exterior derivative on the basic forms of a
Riemannian foliation to obtain a new form of basic cohomology that satisfies
Poincar\'e duality in the transversally orientable case. We use this twisted
basic cohomology to show relationships between curvature, tautness, and
vanishing of the basic Euler characteristic and basic signature.Comment: 20 pages, references added, minor corrections mad
Psychometric precision in phenotype definition is a useful step in molecular genetic investigation of psychiatric disorders
Affective disorders are highly heritable, but few genetic risk variants have been consistently replicated in molecular genetic association studies. The common method of defining psychiatric phenotypes in molecular genetic research is either a summation of symptom scores or binary threshold score representing the risk of diagnosis. Psychometric latent variable methods can improve the precision of psychiatric phenotypes, especially when the data structure is not straightforward. Using data from the British 1946 birth cohort, we compared summary scores with psychometric modeling based on the General Health Questionnaire (GHQ-28) scale for affective symptoms in an association analysis of 27 candidate genes (249 single-nucleotide polymorphisms (SNPs)). The psychometric method utilized a bi-factor model that partitioned the phenotype variances into five orthogonal latent variable factors, in accordance with the multidimensional data structure of the GHQ-28 involving somatic, social, anxiety and depression domains. Results showed that, compared with the summation approach, the affective symptoms defined by the bi-factor psychometric model had a higher number of associated SNPs of larger effect sizes. These results suggest that psychometrically defined mental health phenotypes can reflect the dimensions of complex phenotypes better than summation scores, and therefore offer a useful approach in genetic association investigations
Study of intermediate velocity products in the Ar+Ni collisions between 52 and 95 A.MeV
Intermediate velocity products in Ar+Ni collisions from 52 to 95 A.MeV are
studied in an experiment performed at the GANIL facility with the 4
multidetector INDRA. It is shown that these emissions cannot be explained by
statistical decays of the quasi-projectile and the quasi-target in complete
equilibrium. Three methods are used to isolate and characterize intermediate
velocity products. The total mass of these products increases with the violence
of the collision and reaches a large fraction of the system mass in mid-central
collisions. This mass is found independent of the incident energy, but strongly
dependent on the geometry of the collision. Finally it is shown that the
kinematical characteristics of intermediate velocity products are weakly
dependent on the experimental impact parameter, but strongly dependent on the
incident energy. The observed trends are consistent with a
participant-spectator like scenario or with neck emissions and/or break-up.Comment: 37 pages, 13 figure
PET imaging of the autonomic myocardial function: methods and interpretation.
Cardiac positron emission tomography (PET) is mainly applied in myocardial perfusion and viability detection. Noninvasive imaging of myocardial innervation using PET is a valuable additional methodology in cardiac imaging. Novel methods and different PET ligands have been developed to measure presynaptic and postsynaptic function of the cardiac neuronal system. Obtained PET data can be analysed quantitatively or interpreted qualitatively. Thus far, PET is not a widely used clinical application in autonomic heart imaging; however, due to its technical advantages, the excellent properties of the imaging agents, and the availability of tools for quantification, it deserves a better position in the clinic. From a historical point of view, the focus of PET software packages for image analysis was mainly oncology and neurology driven. Actually, commercially available software for cardiac PET image analysis is still only available for the quantification of myocardial blood flow. Thus far, no commercial software package is available for the interpretation and quantification of PET innervation scans. However, image data quantification and analysis of kinetic data can be performed using adjusted generic tools. This paper gives an overview of different neuronal PET ligands, interpretation and quantification of acquired PET data
Measurements of sideward flow around the balance energy
Sideward flow values have been determined with the INDRA multidetector for
Ar+Ni, Ni+Ni and Xe+Sn systems studied at GANIL in the 30 to 100 A.MeV incident
energy range. The balance energies found for Ar+Ni and Ni+Ni systems are in
agreement with previous experimental results and theoretical calculations.
Negative sideward flow values have been measured. The possible origins of such
negative values are discussed. They could result from a more important
contribution of evaporated particles with respect to the contribution of
promptly emitted particles at mid-rapidity. But effects induced by the methods
used to reconstruct the reaction plane cannot be totally excluded. Complete
tests of these methods are presented and the origins of the
``auto-correlation'' effect have been traced back. For heavy fragments, the
observed negative flow values seem to be mainly due to the reaction plane
reconstruction methods. For light charged particles, these negative values
could result from the dynamics of the collisions and from the reaction plane
reconstruction methods as well. These effects have to be taken into account
when comparisons with theoretical calculations are done.Comment: 27 pages, 15 figure
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