Summary
Recently, the question of whether vitamin D exerts an effect on the pathogenic process of infertility has become the centre of attention. There are some controversial conclusions on this ...issue. Based on previous studies, we sought to explore the difference of serum 25‐hydroxyvitamin D3, 1,25‐dihydroxyvitamin D3 levels between infertile patients and fertile men, and to find the influence on semen quality. The analysis of serum 25‐hydroxyvitamin D3 level showed no significant difference between infertile patients and fertile men. However, the levels of serum 1,25‐dihydroxyvitamin D3 in oligospermia (P < 0.05), asthenospermia (P < 0.01), oligoasthenospermia (P < 0.05) and azoospermia (P < 0.01) patients were significantly lower than those in fertile men. Moreover, serum 1,25‐dihydroxyvitamin D3 level was positively correlated with progressive motility and total sperm number in infertile patients. In addition, a positive correlation between serum prolactin and 1,25‐dihydroxyvitamin D3 was observed in fertile men. Our results indicated that lower vitamin D could be a risk factor for poor semen quality in infertile men. The 1,25‐dihydroxyvitamin D3, as the biologically active form of vitamin D, may be more significant.
Hexagonal boron nitride (h-BN) is a natural hyperbolic material, in which the dielectric constants are the same in the basal plane (ε(t) ≡ ε(x) = ε(y)) but have opposite signs (ε(t)ε(z) < 0) in the ...normal plane (ε(z)). Owing to this property, finite-thickness slabs of h-BN act as multimode waveguides for the propagation of hyperbolic phonon polaritons--collective modes that originate from the coupling between photons and electric dipoles in phonons. However, control of these hyperbolic phonon polaritons modes has remained challenging, mostly because their electrodynamic properties are dictated by the crystal lattice of h-BN. Here we show, by direct nano-infrared imaging, that these hyperbolic polaritons can be effectively modulated in a van der Waals heterostructure composed of monolayer graphene on h-BN. Tunability originates from the hybridization of surface plasmon polaritons in graphene with hyperbolic phonon polaritons in h-BN, so that the eigenmodes of the graphene/h-BN heterostructure are hyperbolic plasmon-phonon polaritons. The hyperbolic plasmon-phonon polaritons in graphene/h-BN suffer little from ohmic losses, making their propagation length 1.5-2.0 times greater than that of hyperbolic phonon polaritons in h-BN. The hyperbolic plasmon-phonon polaritons possess the combined virtues of surface plasmon polaritons in graphene and hyperbolic phonon polaritons in h-BN. Therefore, graphene/h-BN can be classified as an electromagnetic metamaterial as the resulting properties of these devices are not present in its constituent elements alone.
The matter-neutrino resonance (MNR) phenomenon has the potential to significantly alter the flavor content of neutrinos emitted from compact object mergers. We present the first calculations of MNR ...transitions using neutrino self-interaction potentials and matter potentials generated self-consistently from a dynamical model of a three-dimensional neutron star merger. In the context of the single angle approximation, we find that symmetric and standard MNR transitions occur in both normal and inverted hierarchy scenarios. We examine the spatial regions above the merger remnant where propagating neutrinos will encounter the matter-neutrino resonance and find that a significant fraction of the neutrinos are likely to undergo MNR transitions.
Abstract
The mergers of binary neutron stars, as well as black hole–neutron star systems, are expected to produce an electromagnetic counterpart that can be analyzed to infer the element synthesis ...that occurred in these events. We investigate one source of uncertainties pertinent to lanthanide-rich outflows: the nuclear inputs to rapid neutron capture nucleosynthesis calculations. We begin by examining 32 different combinations of nuclear inputs: eight mass models, two types of spontaneous fission rates, and two types of fission daughter product distributions. We find that such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in key quantities such as the nuclear heating (one and a half orders of magnitude at 1 day post-merger), the bolometric luminosity (one order of magnitude at 5 days post-merger), and the inferred mass of material from the bolometric luminosity (factor of 8 when considering the 8–10 day region). Since particular nuclear processes are critical for determining the electromagnetic signal, we provide tables of key nuclei undergoing
β
-decay,
α
-decay, and spontaneous fission important for heating at different times, identifying decays that are common among the many nuclear input combinations.
Abstract
Merging neutron stars produce “kilonovae”—electromagnetic transients powered by the decay of unstable nuclei synthesized via rapid neutron capture (the
r
-process) in material that is ...gravitationally unbound during inspiral and coalescence. Kilonova emission, if accurately interpreted, can be used to characterize the masses and compositions of merger-driven outflows, helping to resolve a long-standing debate about the origins of
r
-process material in the Universe. We explore how the uncertain properties of nuclei involved in the
r
-process complicate the inference of outflow properties from kilonova observations. Using
r
-process simulations, we show how nuclear physics uncertainties impact predictions of radioactive heating and element synthesis. For a set of models that span a large range in both predicted heating and final abundances, we carry out detailed numerical calculations of decay product thermalization and radiation transport in a kilonova ejecta with a fixed mass and density profile. The light curves associated with our models exhibit great diversity in their luminosities, with peak brightness varying by more than an order of magnitude. We also find variability in the shape of the kilonova light curves and their color, which in some cases runs counter to the expectation that increasing levels of lanthanide and/or actinide enrichment will be correlated with longer, dimmer, redder emission.
We report on nano-infrared (IR) imaging studies of confined plasmon modes inside patterned graphene nanoribbons (GNRs) fabricated with high-quality chemical-vapor-deposited (CVD) graphene on Al2O3 ...substrates. The confined geometry of these ribbons leads to distinct mode patterns and strong field enhancement, both of which evolve systematically with the ribbon width. In addition, spectroscopic nanoimaging in the mid-infrared range 850–1450 cm–1 allowed us to evaluate the effect of the substrate phonons on the plasmon damping. Furthermore, we observed edge plasmons: peculiar one-dimensional modes propagating strictly along the edges of our patterned graphene nanostructures.
Neutron star mergers offer unique conditions for the creation of the heavy elements, and additionally provide a testbed for our understanding of this synthesis known as the r-process. We have ...performed dynamical nucleosynthesis calculations and identified a single isotope, 254Cf, which has a particularly high impact on the brightness of electromagnetic transients associated with mergers on the order of 15 to 250 days. This is due to the anomalously long half-life of this isotope and the efficiency of fission thermalization compared to other nuclear channels. We estimate the fission fragment yield of this nucleus and outline the astrophysical conditions under which 254Cf has the greatest impact to the light curve. Future observations in the mid-infrared, which are bright during this regime, could indicate the production of actinide nucleosynthesis.
The highly stable spin of neutron stars can be exploited for a variety of (astro)physical investigations. In particular, arrays of pulsars with rotational periods of the order of milliseconds can be ...used to detect correlated signals such as those caused by gravitational waves. Three such ‘pulsar timing arrays’ (PTAs) have been set up around the world over the past decades and collectively form the ‘International’ PTA (IPTA). In this paper, we describe the first joint analysis of the data from the three regional PTAs, i.e. of the first IPTA data set. We describe the available PTA data, the approach presently followed for its combination and suggest improvements for future PTA research. Particular attention is paid to subtle details (such as underestimation of measurement uncertainty and long-period noise) that have often been ignored but which become important in this unprecedentedly large and inhomogeneous data set. We identify and describe in detail several factors that complicate IPTA research and provide recommendations for future pulsar timing efforts. The first IPTA data release presented here (and available online) is used to demonstrate the IPTA's potential of improving upon gravitational-wave limits placed by individual PTAs by a factor of ∼2 and provides a 2σ limit on the dimensionless amplitude of a stochastic gravitational-wave background of 1.7 × 10−15 at a frequency of 1 yr−1. This is 1.7 times less constraining than the limit placed by Shannon et al., due mostly to the more recent, high-quality data they used.
The adsorption capacity of expanded graphite (EG) with three different particle sizes of 32 mesh, 50 mesh, and 80 mesh was studied by the water-soluble adsorption method. The self-made NaNO3–NaCl ...(95–5 wt%) was selected as the phase change heat storage material, and the three kinds of EG were used as additives. The 80 wt% NaNO3–NaCl/20 wt% EG shaped composite phase change materials (CPCM) were prepared and their properties were tested and analyzed. The research results showed that the smaller the particle size, the stronger the adsorption capacity of EG. However, the choice of EG should consider the particle size of the phase change material (PCM). The 50 mesh EG was more suitable as the adsorption carrier of NaNO3–NaCl. Compared with pure NaNO3–NaCl, NaNO3–NaCl/EG had a lower degree of supercooling, which improved the heat storage capacity of the material. As the particle size of EG decreased, the thermal conductivity increased slightly. The study analyzed the relationship between the EG adsorption capacity and its particle size, and prepared NaNO3–NaCl/EG heat storage material with high heat storage density and high thermal conductivity. It was helpful to promote the application of EG based composite heat storage materials and the development of heat storage technology.
•The adsorption capacity of EG with a smaller particle size is stronger.•50 mesh EG is more suitable as the adsorption carrier of NaNO3–NaCl.•EG addition lowers the supercooling degree of composite PCM.•NaNO3–NaCl/EG composite material after shaping treatment has good thermal stability.•The thermal conductivity increases slightly with the decrease of EG particle size.
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