Measuring valley polarization in two-dimensional materials with second-harmonic spectroscopy

A population imbalance at different valleys of an electronic system lowers its effective rotational symmetry. We introduce a technique to measure such imbalance - a valley polarization - that exploits the unique fingerprints of this symmetry reduction in the polarization-dependent second-harmonic generation (SHG). We present the principle and detection scheme in the context of hexagonal two-dimensional crystals, which include graphene-based systems and the family of transition metal dichalcogenides, and provide a direct experimental demonstration using a 2H-MoSe$_{2}$ monolayer at room temperature. We deliberately use the simplest possible setup, where a single pulsed laser beam simultaneously controls the valley imbalance and tracks the SHG process. We further developed a model of the transient population dynamics which analytically describes the valley-induced SHG rotation in very good agreement with the experiment. In addition to providing the first experimental demonstration of the effect, this work establishes a conceptually simple, com-pact and transferable way of measuring instantaneous valley polarization, with direct applicability in the nascent field of valleytronics

Teleparallel Killing Vectors of Spherically Symmetric Spacetimes

In this paper, Killing vectors of spherically spacetimes have been evaluated in the context of teleparallel theory of gravitation. Further, we investigate the Killing vectors of the Friedmann metrics. It is found that for static spherically spacetimes the number of Killing vectors turn out to be \emph{seven} while for the Friedmann models, we obtain \emph{six} teleparallel Killing vectors. The results are then compared with those of General Relativity. We conclude that both of these descriptions of gravity do not provide the consistent results in general. However, these results may coincide under certain conditions for a particular spacetime.Comment: 14 pages, accepted for publication in Communications in Theoretical Physic

Meta-analysis of Penetrance and Systematic Review on Transition to Disease in Genetic Hypertrophic Cardiomyopathy

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is characterized by unexplained left ventricular hypertrophy (LVH) and is classically caused by pathogenic or likely pathogenic variants (P/LP) in genes encoding sarcomere proteins. Not all subclinical variant carriers will manifest clinically overt disease, as penetrance (proportion of G+ who develop disease) is variable, age-dependent, and not reliably predicted. METHODS: A systematic search of the literature was performed. We employed random effects generalized linear mixed model meta-analyses to contrast the cross-sectional prevalence and penetrance of sarcomere genes in two different contexts: clinically-based studies on patients and families with HCM versus population/community-based studies. Longitudinal family/clinical studies were additionally analyzed to investigate the rate of phenotypic conversion from subclinical to overt HCM during follow-up. FINDINGS: 455 full text manuscripts were assessed. In family/clinical studies, the prevalence of sarcomere variants in patients diagnosed with HCM was 34%. The penetrance across all genes in non-proband relatives carrying P/LP variants identified during cascade screening was 57% (95% confidence interval [CI] [52,63]) and the mean age of HCM diagnosis was 38 years (95% CI [36, 40]). Penetrance varied from ~32% for myosin light chain (MYL3) to ~55% for myosin binding protein C (MYBPC3), ~60% troponin T (TNNT2) and troponin I (TNNI3), and ~65% for myosin heavy chain (MYH7). Population-based genetic studies demonstrate that P/LP sarcomere variants are present in the background population, but at a low prevalence of <1%. The penetrance of HCM in incidentally identified P/LP variant carriers was also substantially lower; approximatively 11%, ranging from 0% in Atherosclerosis Risk in Communities to 18% in UK Biobank. In longitudinal family studies, the pooled phenotypic conversion across all genes was 15% over an average of ~8 years of follow up, starting from a mean age of ~16 years. However, short-term gene-specific phenotypic conversion varied between ~12% for MYBPC3 to ~23% for MYH7. CONCLUSIONS: The penetrance of P/LP variants is highly variable and influenced by currently undefined and context-dependent genetic and environmental factors. Additional longitudinal studies are needed to improve understanding of true lifetime penetrance in families and in the community, and to identify drivers of the transition from subclinical to overt HCM

The Effect of Active Galactic Nuclei on the Mid-Infrared Aromatic Features

We present Spitzer measurements of the aromatic (also known as PAH) features for 35 Seyfert galaxies from the revised Shapley-Ames sample and find that the relative strengths of the features differ significantly from those observed in star-forming galaxies. Specifically, the features at 6.2, 7.7, and 8.6 micron are suppressed relative to the 11.3 micron feature in Seyferts. Furthermore, we find an anti-correlation between the L(7.7 micron)/L(11.3 micron) ratio and the strength of the rotational H2 (molecular hydrogen) emission, which traces shocked gas. This suggests that shocks suppress the short-wavelength features by modifying the structure of the aromatic molecules or destroying the smallest grains. Most Seyfert nuclei fall on the relationship between aromatic emission and [Ne II] emission for star-forming galaxies, indicating that aromatic-based estimates of the star-formation rate in AGN host galaxies are generally reasonable. For the outliers from this relationship, which have small L(7.7 micron)/L(11.3 micron) ratios and strong H2 emission, the 11.3 micron feature still provides a valid measure of the star-formation rate.Comment: Accepted for publication in ApJ. 17 pages, 12 figure

The Mid-Infrared High-Ionization Lines from Active Galactic Nuclei and Star-Forming Galaxies

We used Spitzer/IRS spectroscopic data on 426 galaxies including quasars, Seyferts, LINER and HII galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne V]14.3 um and 24.3 um (97.1 eV) and the [O IV]25.9 um (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne III]15.56 um (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne III] excess due to star formation in Seyfert galaxies. We also estimated the [O IV] luminosity due to star formation in active galaxies and determined that it dominates the [O IV] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the AGN dominates the [O IV] emission in most Seyfert galaxies, whereas star-formation adequately explains the observed [O IV] emission in optically classified HII galaxies. Finally we computed photoionization models to determine the physical conditions of the narrow line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log nH (cm-2) < 21.Comment: Accepted for Publication in ApJ, 19 pages, 13 figure

Local Luminous Infrared Galaxies. II. AGN Activity from Spitzer/IRS spectra

We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000micron) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs). We decompose the Spitzer Infrared Spectrograph (IRS) low-resolution 5-38micron spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is ~62%. The derived AGN bolometric luminosities are in the range L_bol(AGN)=0.4 -50x10^{43} erg/s. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L_bol(AGN)/L_IR<0.05. Only ~8% of local LIRGs have a significant AGN bolometric contribution L_bol(AGN)/L_IR > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies, we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for 5%^{+8%}_{-3%} of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of Omega_IR(AGN) = 3x10^5 L_sun Mpc^{-3}$ in LIRGs.Comment: 20 pages, accepted for publication in Ap

The evolutionary dynamics of the Saccharomyces cerevisiae protein interaction network after duplication

Gene duplication is an important mechanism in the evolution of protein interaction networks. Duplications are followed by the gain and loss of interactions, rewiring the network at some unknown rate. Because rewiring is likely to change the distribution of network motifs within the duplicated interaction set, it should be possible to study network rewiring by tracking the evolution of these motifs. We have developed a mathematical framework that, together with duplication data from comparative genomic and proteomic studies, allows us to infer the connectivity of the preduplication network and the changes in connectivity over time. We focused on the whole-genome duplication (WGD) event in Saccharomyces cerevisiae. The model allowed us to predict the frequency of intergene interaction before WGD and the post duplication probabilities of interaction gain and loss. We find that the predicted frequency of self-interactions in the preduplication network is significantly higher than that observed in today's network. This could suggest a structural difference between the modern and ancestral networks, preferential addition or retention of interactions between ohnologs, or selective pressure to preserve duplicates of self-interacting proteins

Mulsemedia: State of the art, perspectives, and challenges

Mulsemedia-multiple sensorial media-captures a wide variety of research efforts and applications. This article presents a historic perspective on mulsemedia work and reviews current developments in the area. These take place across the traditional multimedia spectrum-from virtual reality applications to computer games-as well as efforts in the arts, gastronomy, and therapy, to mention a few. We also describe standardization efforts, via the MPEG-V standard, and identify future developments and exciting challenges the community needs to overcome

Equilibrium, kinetic and thermodynamic studies on the removal of U(VI) by low cost agricultural waste

In this research, biosorption efficiency of different agro-wastes were evaluated with rice husk showing maximum biosorption capacity among the selected biosorbents. Optimization of native, SDS-treated and immobilized rice husk adsorption parameters including pH, biosorbent amount, contact time, initial U(VI) concentration and temperature for maximum U(VI) removal was investigated. Maximum biosorption capacity for native (29.56 mg g-1) and immobilized biomass (17.59 mg g-1) was observed at pH 4 while SDS-treated biomass showed maximum removal (28.08 mg g-1) at pH 5. The Langmuir sorption isotherm model correlated best with the U(IV) biosorption equilibrium data for the 10-100 mg L-1 concentration range. The kinetics of the reaction followed pseudo-second order kinetic model. Thermodynamic parameters like free energy (ΔG°) and enthalpy (ΔH°) confirmed the spontaneous and exothermic nature of the process. Experiments to determine the regeneration capacity of the selected biosorbents and the effect of competing metal ions on biosorption capacity were also conducted. The biomass was characterised using scanning electron microscopy, surface area analysis, Fourier transformed infra-red spectroscopy and thermal gravimetric analysis. The study proved that rice husk has potential to treat uranium in wastewater

Yeast Protein Interactome Topology Provides Framework for Coordinated-Functionality

The architecture of the network of protein-protein physical interactions in Saccharomyces cerevisiae is exposed through the combination of two complementary theoretical network measures, betweenness centrality and `Q-modularity'. The yeast interactome is characterized by well-defined topological modules connected via a small number of inter-module protein interactions. Should such topological inter-module connections turn out to constitute a form of functional coordination between the modules, we speculate that this coordination is occurring typically in a pair-wise fashion, rather than by way of high-degree hub proteins responsible for coordinating multiple modules. The unique non-hub-centric hierarchical organization of the interactome is not reproduced by gene duplication-and-divergence stochastic growth models that disregard global selective pressures.Comment: Final, revised version. 13 pages. Please see Nucleic Acids open access article for higher resolution figure