Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel ...spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.
Motivated by recent observations of chiral-induced magnetization and spin-selective transport we studied the effect of chiral molecules on conventional BCS superconductors. By applying scanning ...tunneling spectroscopy, we demonstrate that the singlet-pairing s-wave order parameter of Nb is significantly altered upon adsorption of chiral polyalanine alpha-helix molecules on its surface. The tunneling spectra exhibit zero-bias conductance peaks embedded inside gaps or gap-like features, suggesting the emergence of unconventional triplet-pairing components with either d-wave or p-wave symmetry at the Nb organic-molecules interface, as corroborated by simulations. These results may open a way for realizing simple superconducting spintronics devices.
Does kin selection moderate sexual conflict in Drosophila? Chippindale, Adam K.; Berggren, Meredith; Alpern, Joshua H. M. ...
Proceedings of the Royal Society. B, Biological sciences,
08/2015, Letnik:
282, Številka:
1813
Journal Article
Recenzirano
Odprti dostop
Two recent studies provide provocative experimental findings about the potential influence of kin recognition and cooperation on the level of sexual conflict in Drosophila melanogaster. In both ...studies, male fruit flies apparently curbed their mate-harming behaviours in the presence of a few familiar or related males, suggesting some form of cooperation mediated by kin selection. In one study, the reduction in agonistic behaviour by brothers apparently rendered them vulnerable to dramatic loss of paternity share when competing with an unrelated male. If these results are robust and generalizable, fruit flies could be a major new focus for the experimental study of kin selection and social evolution. In our opinion, however, the restrictive conditions required for male cooperation to be adaptive in this species make it unlikely to evolve. We investigated these phenomena in two different populations of D. melanogaster using protocols very similar to those in the two previous studies. Our experiments show no evidence for a reduction in mate harm based upon either relatedness or familiarity between males, and no reduction in male reproductive success when two brothers are in the presence of an unfamiliar, unrelated, ‘foreign’ male. Thus, the reduction of sexual conflict owing to male cooperation does not appear to be a general feature of the species, at least under domestication, and these contrasting results call for further investigation: in new populations, in the field and in the laboratory populations in which these phenomena have been reported.
•UV–visible-Near IR GaN light detector was realized by surface modifications.•The detector is operating as standard photoresistor at the UV range.•Near-IR detection up to 1350nm was done at constant ...UV illumination.•Surface modifications included plasma asher and organic molecules adsorption.•The detector is simple to fabricate, reproducible and with high responsivity.
Gallium-nitride (GaN) light detectors are sensitive to ultraviolet (UV) radiation below 365nm wavelength due to their wide bandgap – 3.4eV. However, the presence of impurities, especially surface traps, leads to slow relaxation rates and sub-bandgap response due to new energy levels. In the present work we offer utilizing these impurities to broad the spectral range up to the near-infrared (NIR) and modifying the surface of the photoresistors to enhance the response, the recovery time, and the repeatability by using several surface treatments such as plasma asher and the adsorption of organic molecules. The wide band response up to the NIR range was achieved by exciting the detector with a constant UV light intensity, resulting in a responsivity of 10–100A/W. We ascribe the high sensitivity to visible and NIR wavelengths to a gating amplification effect caused by trapped charges. Owing to the band bending of energy levels, a large depletion layer is created on the surface of the GaN layer, effectively separating the surface conductivity from the bulk. These properties make the detector sensitive to changes on the surface, thus making it ideal for biological and chemical uses as well as for broadband light detectors.
The combination of a superconductor with a magnetically inhomogeneous material has been established as an efficient mechanism for the generation of long-ranged spin-polarized (spin-triplet) Cooper ...pairs. Evidence for this mechanism, however, has been demonstrated based on studies done on thin-film multilayers, where the strong bonds existing at the interface between the superconductor and the magnetic material should in principle enhance proximity effects and strengthen any electronic correlations. Here, we fabricate devices based on van der Waals (vdW) stacks of flakes of the NbS_{2} combined with flakes of Cr_{1/3}NbS_{2}, which has a built-in magnetic inhomogeneity due to its helimagnetic spin texture at low temperatures. We find that the critical temperature of these vdW heterostructures is strongly dependent on the magnetic state of Cr_{1/3}NbS_{2}, whose degree of magnetic inhomogeneity can be controlled via an applied magnetic field. Our results demonstrate evidence for the generation of long-ranged spin-triplet pairs across the Cr_{1/3}NbS_{2}/NbS_{2} vdW interface.
When two species interbreed, the resulting hybrid offspring are often sterile, with the heterogametic (e.g. XY) hybrid usually being more severely affected. The prevailing theory for this pattern of ...sterility evokes divergent changes in separate lineages having maladaptive interactions when placed together in a hybrid individual, with recessive factors on the sex chromosome interacting with dominant factors on the autosomes. The effect of these interactions on gametogenesis should not be uniform across species pairs unless genetic divergence follows the same paths in different lineages or if a specific stage of gametogenesis is more susceptible to detrimental genetic interactions. Here, we perform a detailed cellular characterization of hybrid male sterility across three recently diverged species pairs of
. Across all three pairs, sterile hybrid sperm are alive but exhibit rapid nuclear de-condensation with age, with active, but non-differentiated, mitochondria. Surprisingly, all three sets of interspecies hybrids produce half of the number of sperm per round of spermatogenesis, with each sperm cell containing two tails. We identify non-disjunction failures during meiosis I as the likely cause. Thus, errors during meiosis I may be a general phenomenon underlying
male sterility, indicating either a heightened sensitivity of this spermatogenic stage to failure, or a basis to sterility other than the prevailing model.
Nature Communications 8: Article number: 14024 (2017); Published: 19 January 2017; Updated: 1 March 2017 The present address for U. Sassi is incorrect in this Article. This author does not have a ...present address. The correct full affiliation details for this author are given below: Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, UK.
In many species, males have evolved to produce a sterile sperm (parasperm) in conjunction with fertilizing sperm (eusperm). Here, we document evidence of males depositing two morphologically distinct ...types of parasperm (1 and 2) into the female reproductive tract in Drosophila pseudoobscura. These parasperm differ in length, shape, amount produced, amount in long‐term storage and may have separate roles in ensuring male fertilization success. Although both parasperm types protect eusperm from female spermicides, only parasperm 2, which has a corkscrew shape, is associated with sperm competition. Increased production of parasperm 2 is also negatively correlated with the eusperm and parasperm 1 production. Thus, selection may be acting on parasperm production in the presence of sperm competition. Our findings show how both sperm competition and cryptic female choice may be acting in conjunction to influence the evolution of ejaculate composition. Our identification and characterization of two distinct parasperm morphs will enhance the ability for further evaluation of parasperm's role in fertilization.
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