A first-principles DFT+GW study of spin-filter and spin-gapless semiconducting Heusler compounds

Among Heusler compounds, the ones being magnetic semiconductors (also known as spin-filter materials) are widely studied as they offer novel functionalities in spintronic/magnetoelectronic devices. The spin-gapless semiconductors are a special case. They possess a zero or almost-zero energy gap in one of the two spin channels. We employ the $GW$ approximation, which allows an elaborate treatment of the electronic correlations, to simulate the electronic band structure of these materials. Our results suggest that in most cases the use of $GW$ self energy instead of the usual density functionals is important to accurately determine the electronic properties of magnetic semiconductors.Comment: Final version as publishe

Quasiparticle band structure of the almost-gapless transition-metal-based Heusler semiconductors

Transition-metal-based Heusler semiconductors are promising materials for a variety of applications ranging from spintronics to thermoelectricity. Employing the $GW$ approximation within the framework of the FLAPW method, we study the quasi-particle band structure of a number of such compounds being almost gapless semiconductors. We find that in contrast to the \textit{sp}-electron based semiconductors such as Si and GaAs, in these systems the many-body corrections have a minimal effect on the electronic band structure and the energy band gap increases by less than 0.2~eV, which makes the starting point density functional theory (DFT) a good approximation for the description of electronic and optical properties of these materials. Furthermore, the band gap can be tuned either by the variation of the lattice parameter or by the substitution of the \emph{sp}-chemical element

Temporal variations in phytoplankton composition in the northeastern Sea of Marmara: potentially toxic species and mucilage event

Temporal variations in phytoplankton composition in the northeastern Sea of Marmara was investigated associated with physico-chemical variables from January 2004 to December 2007. The occurrence of potentially toxic species and a mucilage event was also evaluated during this study period. The confined upper layer of the Sea of Marmara is mesotrophic to eutrophic and has higher productivity when compared to the neighbouring Black Sea and Aegean Sea. 132 taxa in the micro-phytoplankton community were identified, 11 of which are known to be potentially toxic. The most abundant species were Pseudo-nitzschia species from diatoms and Prorocentrum micans from dinoflagellates. Potentially toxic species were more common at the coastal stations. The onset of a mucilage formation was observed in October 2007, and well-known mucilage producers such as Gonyaulax hyalina (reported as G. fragilis) and Thalassiosira gravida (reported as T. rotula) dominated the phytoplankton community during this event. A marked decrease in the number of species and diversity index following June 2007 and reported shifts in the zooplankton community during the same period points to probable cascading effects in the pelagic ecosystem of the Sea of Marmara

Drive, filter, and stick: A protein sorting conspiracy in photoreceptors.

The sorting of proteins into different functional compartments is a fundamental cellular task. In this issue, Maza et al. (2019. J. Cell Biol https://doi.org/10.1083/jcb.201906024) demonstrate that distinct protein populations are dynamically generated in specialized regions of photoreceptors via an interplay of protein-membrane affinity, impeded diffusion, and driven transport

Multiple detection using the eigenvalues of the spectral matrix

In this study we treat the problem of detecting from multidimensional data, the number of uncorrelated signais in passive array treatment as it is the case in underwater acoustics, array processing and seismology . We use four detection criteria. Some of them are known, like AIC and MDL criteria where direct Kullback's divergence is the information measure; we prolong them using the inverse Kullback's divergence. We also adapt a new criterion using the logarithm of the likelihood ratio that has a chi square distribution and we suggest a simplified threshold criterion that uses the eigenvalues of the spectral matrix of the data . We study and compare the performances of these criteria in realistic simulations . The first one is inspired by the problems of array processing and the second one by seismic problems. Finally we study the robustness of these criteria when the classical hypothesis of uncorrelated noises having equal variances is not fulfilled . Thus we outline some application limits of these criteria .Critères de détection, résultats sur des simulation

Consumer credit in comparative perspective

We review the literature in sociology and related fields on the fast global growth of consumer credit and debt and the possible explanations for this expansion. We describe the ways people interact with the strongly segmented consumer credit system around the world—more specifically, the way they access credit and the way they are held accountable for their debt. We then report on research on two areas in which consumer credit is consequential: its effects on social relations and on physical and mental health. Throughout the article, we point out national variations and discuss explanations for these differences. We conclude with a brief discussion of the future tasks and challenges of comparative research on consumer credit.Accepted manuscrip

Antarctic Volcanic Flux Ratios from Law Dome Ice Cores

Explosive volcanic eruptions can inject large quantities of sulphur dioxide into the stratosphere. The aerosols that result from oxidation of the sulphur dioxide can produce significant cooling of the troposphere by reflecting or absorbing solar radiation. It is possible to obtain an estimate of the relative stratospheric sulphur aerosol concentration produced by different volcanoes by comparing sulphuric acid fluxes determined by analysis of polar ice cores. Here, we use a non-sea-salt sulphate time series derived from three well-dated Law Dome ice cores to investigate sulphuric acid flux ratios for major eruptions over the period AD 1301-1995. We use additional data from other cores to investigate systematic spatial variability in the ratios. Only for the Kuwae eruption (Law Dome ice date AD 1459.5) was the H2SO4 flux larger than that deposited by Tambora (Law Dome ice date AD 1816.7)

Localization of correlated sources by array processing using spatial smoothing

In this paper, the classical array processing methods are separated in two classes : uncoupled solutions and global solutions . We expose the method that uses the spatial smooting to decorrelate the received signais . Then we apply these array processing methods to signais that are recorded in an underwater acoustics experiment ; in this situation the spatial smoothing is compulsary . Results are discussed .Dans cet article, nous regroupons les diverses méthodes connues de traitement d'antenne en deux catégories : méthodes découplées, méthodes globales . Nous présentons la méthode du lissage spatial qui permet de décorréler les sources à la réception . Nous appliquons ensuite ces méthodes de traitement d'antenne à des signaux enregistrés au cours d'une expérimentation en acoustique sous-marine dans laquelle une onde monochromatique a été émise dans différentes configurations géométriques et météorologiques . Dans cette situation, le lissage spatial doit être utilisé pour décorréler les trajets multiples

Nonequilibrium Electron Interactions in Metal Films

Ultrafast relaxation dynamics of an athermal electron distribution is investigated in silver films using a femtosecond pump-probe technique with 18 fs pulses in off-resonant conditions. The results yield evidence for an increase with time of the electron-gas energy loss rate to the lattice and of the free electron damping during the early stages of the electron-gas thermalization. These effects are attributed to transient alterations of the electron average scattering processes due to the athermal nature of the electron gas, in agreement with numerical simulations