It is generally accepted that spin-dependent electron transmission may appear in chiral systems, even without magnetic components, as long as significant spin–orbit coupling is present in some of its ...elements. However, how this chirality-induced spin selectivity (CISS) manifests in experiments, where the system is taken out of equilibrium, is still debated. Aided by group theoretical considerations and nonequilibrium DFT-based quantum transport calculations, here we show that when spatial symmetries that forbid a finite spin polarization in equilibrium are broken, a net spin accumulation appears at finite bias in an arbitrary two-terminal nanojunction. Furthermore, when a suitably magnetized detector is introduced into the system, the net spin accumulation, in turn, translates into a finite magneto-conductance. The symmetry prerequisites are mostly analogous to those for the spin polarization at any bias with the vectorial nature given by the direction of magnetization, hence establishing an interconnection between these quantities.
Mismatch repair (MMR) is a near ubiquitous pathway, essential for the maintenance of genome stability. Members of the MutS and MutL protein families perform key steps in mismatch correction. Despite ...the major importance of this repair pathway, MutS-MutL are absent in almost all Actinobacteria and many Archaea. However, these organisms exhibit rates and spectra of spontaneous mutations similar to MMR-bearing species, suggesting the existence of an alternative to the canonical MutS-MutL-based MMR. Here we report that Mycobacterium smegmatis NucS/EndoMS, a putative endonuclease with no structural homology to known MMR factors, is required for mutation avoidance and anti-recombination, hallmarks of the canonical MMR. Furthermore, phenotypic analysis of naturally occurring polymorphic NucS in a M. smegmatis surrogate model, suggests the existence of M. tuberculosis mutator strains. The phylogenetic analysis of NucS indicates a complex evolutionary process leading to a disperse distribution pattern in prokaryotes. Together, these findings indicate that distinct pathways for MMR have evolved at least twice in nature.
Spin–orbit coupling gives rise to a range of spin-charge interconversion phenomena in nonmagnetic systems where certain spatial symmetries are reduced or absent. Chirality-induced spin-selectivity ...(CISS), a term that generically refers to a spin-dependent electron transfer in nonmagnetic chiral systems, is one such case, appearing in a variety of seemingly unrelated situations ranging from inorganic materials to molecular devices. In particular, the origin of CISS in molecular junctions is a matter of an intense current debate. Here, we derive a set of geometrical conditions for this effect to appear, hinting at the fundamental role of symmetries beyond otherwise relevant quantitative issues. Our approach, which draws on the use of point-group symmetries within the scattering formalism for transport, shows that electrode symmetries are as important as those of the molecule when it comes to the emergence of a spin-polarization and, by extension, to the possible appearance of CISS. It turns out that standalone metallic nanocontacts can exhibit spin-polarization when relative rotations which reduce the symmetry are introduced. As a corollary, molecular junctions with achiral molecules can also exhibit spin-polarization along the direction of transport, provided that the whole junction is chiral in a specific way. This formalism also allows the prediction of qualitative changes of the spin-polarization upon substitution of a chiral molecule in the junction with its enantiomeric partner. Quantum transport calculations based on density functional theory corroborate all of our predictions and provide further quantitative insight within the single-particle framework.
The bulk photovoltaic effect is an experimentally verified phenomenon by which a direct charge current is induced within a non-centrosymmetric material by light illumination. Calculations of its ...intrinsic contribution, the shift current, are nowadays amenable from first-principles employing plane-wave bases. In this work, we present a general method for evaluating the shift conductivity in the framework of localized Gaussian basis sets that can be employed in both the length and velocity gauges, carrying the idiosyncrasies of the quantum-chemistry approach. The (possibly magnetic) symmetry of the system is exploited in order to fold the reciprocal space summations to the representation domain, allowing us to reduce computation time and unveiling the complete symmetry properties of the conductivity tensor under general light polarization.
ABSTRACT The "main sequence of galaxies"-defined in terms of the total star formation rate versus the total stellar mass M*-is a well-studied tight relation that has been observed at several ...wavelengths and at different redshifts. All earlier studies have derived this relation from integrated properties of galaxies. We recover the same relation from an analysis of spatially resolved properties, with integral field spectroscopic (IFS) observations of 306 galaxies from the CALIFA survey. We consider the SFR surface density in units of log(M yr−1 Kpc−2) and the stellar mass surface density in units of log(M Kpc−2) in individual spaxels that probe spatial scales of 0.5-1.5 Kpc. This local relation exhibits a high degree of correlation with small scatter ( = 0.23 dex), irrespective of the dominant ionization source of the host galaxy or its integrated stellar mass. We highlight (i) the integrated star formation main sequence formed by galaxies whose dominant ionization process is related to star formation, for which we find a slope of 0.81 0.02; (ii) for the spatially resolved relation obtained with the spaxel analysis, we find a slope of 0.72 0.04; and (iii) for the integrated main sequence, we also identified a sequence formed by galaxies that are dominated by an old stellar population, which we have called the retired galaxies sequence.
Abstract Spin-charge inter-conversion mediated by spin-orbit coupling can lead to finite magnetoconductance in two-terminal molecular nanojunctions under non-equilibrium conditions. Here, we ...demonstrate how such a finite magnetoconductance can emerge in model two-terminal molecular nanojunctions by means of density functional theory based transport calculations with spin-orbit coupling in a first-order perturbation approximation. The junctions are built from the two chiral partners of an idealized helical molecule and tungsten or gold electrodes with two layers of magnetic nickel at the interface of the drain electrodes. Using Au source electrodes and a low applied bias of 0.1 V, we find percentage relative magnetoconductance values in excess of the lower bound reported in recent low-temperature, low-bias, experiments. The left-handed molecule is seen to exhibit greater magnetoconductance than its right-handed chiral partner for both Au and W source electrodes, thus demonstrating that our calculations can also exhibit enantioselectivity.
To assess the effect of experimental Type 1 diabetes on male fertility, male Sprague Dawley rats were injected with either streptozotocine (STZ) to induce diabetes or with citrate buffer as controls. ...Diabetic animals and 2 control groups (STZ‐resistant and buffer‐injected rats) were sacrificed at 2 different times after injection: 6 weeks (6W) and 20 weeks (20W). We analyzed serum testosterone (sTT), epididymal sperm parameters, and weight of testicles and epididymides, and carried out a histological evaluation of testicular tissue. Diabetic animals presented a significant increase in teratozoospermia (20W, P < .01) and a decrease in sTT (P < .01), tubular diameter (6W, P < .05), and testicular (6W, P < .01) and epididymal (P < .01) weight. STZ‐resistant animals showed significantly decreased sTT (6W, P < .01), epididymal weight (6W, P < .05), and sperm count (6W, P < .01) compared with buffer–injected controls. Experimental STZ diabetes increases teratozoospermia and decreases sTT, testicular weight (reverting at medium‐term), and epididymal weight.
Purpose
Assess the utility of a hands-on workshop on abdominal wall reconstruction for teaching the posterior components separation (PCS) with transversus abdominis release.
Methods
Our department ...has been organizing a training course on abdominal wall reconstruction for the last 6 years. It is a 2-day-long course and 10–12 surgeons with experience in abdominal wall surgery attend to every course. The first day is dedicated to theoretical lectures and two simultaneous live surgeries, and the second day there is a cadaver dissection. Feedback from the trainees was collected at the end of the workshop. A survey was sent to all the surgeons who had completed the course at least a year ago, to inquire how the course had improved their surgical practice.
Results
From 2013 to April 2017, we have made 15 editions of the course. A total of 192 surgeons from Europe, South Africa and Middle East attended. All the surgeons answered the survey that was carried out at the end of the course. It showed a very high level of satisfaction in more than 98% of the cases. The second survey was answered by 79 surgeons (41.15%). 96% of the surgeons had modified, after attending the course, their way of dealing with complex abdominal wall problems. Only 29% of the surgeons had made a TAR before attending the course, while 86% are performing it after attending the course and 60% do it on a regular basis. In fact, 43% of surgeons have performed more than five posterior component separations in the last year.
Conclusions
A workshop of abdominal wall surgery that combines live surgery, theoretical content and a cadaver lab can be a very useful tool to expand the use of new surgical techniques.
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