Evidence of Strong-Coupled Superconductivity in CaC6 from Tunneling Spectroscopy

Point-contact tunneling on CaC$_6$ crystals reproducibly reveals superconducting gaps, $\Delta$, of 2.3$\pm$0.2 meV which are $\sim$~40% larger than earlier reports. That puts CaC$_6$ into the class of very strong-coupled superconductors since 2$\Delta$/kT$_c\sim$~4.6. Thus soft Ca phonons will be primarily involved in the superconductivity, a conclusion that explains the large Ca isotope effect found recently for CaC$_6$. Consistency among superconductor-insulator-normal metal (SIN), SIS and Andreev reflection (SN) junctions reinforces the intrinsic nature of this result.Comment: 2nd version, 4 pages, 4 figures, re-submitted to Physical Review Letter

Characteristic Energy of the Coulomb Interactions and the Pileup of States

Tunneling data on $\mathrm{La_{1.28}Sr_{1.72}Mn_2O_7}$ crystals confirm Coulomb interaction effects through the $\sqrt{\mathrm{E}}$ dependence of the density of states. Importantly, the data and analysis at high energy, E, show a pileup of states: most of the states removed from near the Fermi level are found between ~40 and 130 meV, from which we infer the possibility of universal behavior. The agreement of our tunneling data with recent photoemission results further confirms our analysis.Comment: 4 pages, 4 figures, submitted to PR

Persistent household food insecurity, HIV, and maternal stress in Peri-Urban Ghana

BACKGROUND: The mental health of caregivers has been shown to be important for improving HIV prevention and treatment. Household food insecurity affects hundreds of millions of individuals in Sub-Saharan Africa, a region that experiences a disproportionate burden of the HIV pandemic. Both maternal HIV diagnosis and household food insecurity may be linked with maternal stress. This in turn may lead to unhealthy coping behaviors. We examined the independent associations of HIV, persistent household food insecurity and the synergistic effect of both on maternal stress. METHODS: Ghanaian women recruited prenatally from hospitals offering voluntary counseling and testing (VCT) were followed for 12 months after childbirth (N = 232). A locally adapted 7-item version of the US Household Food Security Survey Module was applied at four time points postpartum. We dichotomized participant households as being persistently food insecure (i.e., food insecure at each time point) or not (i.e., food secure at any time point). We dichotomized participant women as not perceiving vs. perceiving stress at 12 months postpartum in reference to the median sample score on the 4-item Cohen’s stress scale. Binary multivariate logistic regression models were used to assess the independent and interactive effects of maternal HIV and persistent household food insecurity on maternal stress. RESULTS: The proportion of HIV-positive women that lived in severe food insecure households increased over time. By contrast, the HIV-negative group living in severely food insecure households experienced a steady decline across time. HIV-infection (AOR = 2.31, 95% CI 1.29-4.12) and persistent household food insecurity (AOR = 3.55, 95% CI 1.13-11.13) were independently associated with maternal stress in a multivariate model. Being both HIV-positive and persistently food insecure strongly and synergistically increased the risk for maternal perceived stress (AOR = 15.35, 95% CI 1.90-124.14). CONCLUSION: In agreement with syndemic theory there is a powerful synergism between maternal HIV diagnosis and household food insecurity on maternal stress. Comprehensive multi-dimensional intervention studies are needed to better understand how to reduce stress among HIV-positive women living in persistently food insecure households and how to reduce the likelihood of food insecurity in HIV-affected households in Sub-Saharan Africa

The suitability of soils for on-site wastewater disposal.

pt. 1. Water quality and nutrient budget by John E. Gannon and Daniel J. Mazur--pt. 2. The suitability of soils for on-site wastewater disposal by Arthur Gold and John E. Gannon. Includes bibliographies.http://deepblue.lib.umich.edu/bitstream/2027.42/49260/2/2193573.0008.001.pd

Precipitating Electrons: Evidence For Effects On Mesospheric Odd Nitrogen

Observations of electron fluxes made by the PET and LICA instruments aboard SAMPEX have been used with NO measurements made by HALOE aboard UARS to provide evidence of mesospheric and lower thermospheric NO formation due to precipitating electrons. Results indicate significant NO increases from 70 to 120 km which are associated with the occurrence of enhanced electron populations in the outer trapping regions of the magnetosphere, 2.5 ≤ L ≤ 7, which precipitate into the atmosphere

The preparation route and final form of V-MXenes override the effect of the O/F ratio on their magnetic properties

This work was supported by OP VVV “Excellent Research Teams” project no. CZ.02.1.01/0.0/0.0/15_003/0000417 – CUCAM. P. E. would like to also acknowledge the Czech Science Foundation for the ExPro project (19-27551X). Computational resources and low-temperature infrastructure were supplied by the projects “e-Infrastruktura CZ” (e-INFRA CZ LM2018140) and MGML (LM2023065) supported by the Ministry of Education, Youth and Sports of the Czech Republic.Transition metal carbides and nitrides (MXenes) show a high potential for electrochemical energy storage in batteries and supercapacitors and for electrocatalysis. Their excellent electronic and magnetic characteristics have been highlighted in several theoretical studies. However, experimental research on MXenes is yet to confirm their predicted properties as candidates for controllable magnetic 2D materials. Here, we report our theoretical and experimental study of V2CTx MXenes (T = O, OH, F), providing key insights into their magnetism. Based on our density functional theory (DFT) analysis, we predicted ferromagnetic (FM) and antiferromagnetic (AFM) states of V2CTx, which are determined by the O/F ratio of surface functional groups. Accordingly, we prepared V2CTx MXenes in the form of multilayered powders and thin films with different O/F ratios. No experimental evidence of FM or AFM properties was found in any material. Nevertheless, powders and films with almost identical chemical compositions (in terms of O/F ratio) displayed different magnetic properties, whereas films with disparate chemical compositions revealed a similar magnetic character. Therefore, the preparation route and form of the final V2CTx material override the effect of the O/F ratio, which is often overestimated in theoretical studies. Moreover, these findings underscore the importance of preparing MXene materials to experimentally confirm their theoretically predicted properties.Peer reviewe

Electron Beam-Treated Enzymatically Mineralized Gelatin Hydrogels for Bone Tissue Engineering

Biological hydrogels are highly promising materials for bone tissue engineering (BTE) due to their high biocompatibility and biomimetic characteristics. However, for advanced and customized BTE, precise tools for material stabilization and tuning material properties are desired while optimal mineralisation must be ensured. Therefore, reagent-free crosslinking techniques such as high energy electron beam treatment promise effective material modifications without formation of cytotoxic by-products. In the case of the hydrogel gelatin, electron beam crosslinking further induces thermal stability enabling biomedical application at physiological temperatures. In the case of enzymatic mineralisation, induced by Alkaline Phosphatase (ALP) and mediated by Calcium Glycerophosphate (CaGP), it is necessary to investigate if electron beam treatment before mineralisation has an influence on the enzymatic activity and thus affects the mineralisation process. The presented study investigates electron beam-treated gelatin hydrogels with previously incorporated ALP and successive mineralisation via incubation in a medium containing CaGP. It could be shown that electron beam treatment optimally maintains enzymatic activity of ALP which allows mineralisation. Furthermore, the precise tuning of material properties such as increasing compressive modulus is possible. This study characterizes the mineralised hydrogels in terms of mineral formation and demonstrates the formation of CaP in dependence of ALP concentration and electron dose. Furthermore, investigations of uniaxial compression stability indicate increased compression moduli for mineralised electron beam-treated gelatin hydrogels. In summary, electron beam-treated mineralized gelatin hydrogels reveal good cytocompatibility for MG-63 osteoblast like cells indicating a high potential for BTE applications

High-Order Coherent Communications Using Modelocked Dark-Pulse Kerr Combs from Microresonators

Microresonator frequency combs harness the nonlinear Kerr effect in an integrated optical cavity to generate a multitude of phase-locked frequency lines. The line spacing can reach values in the order of 100 GHz, making it an attractive multi-wavelength light source for applications in fiber-optic communications. Depending on the dispersion of the microresonator, different physical dynamics have been observed. A recently discovered comb state corresponds to the formation of mode-locked dark pulses in a normal-dispersion microcavity. Such dark-pulse combs are particularly compelling for advanced coherent communications since they display unusually high power-conversion efficiency. Here, we report the first coherent-transmission experiments using 64-quadrature amplitude modulation encoded onto the frequency lines of a dark-pulse comb. The high conversion efficiency of the comb enables transmitted optical signal-to-noise ratios above 33 dB, while maintaining a laser pump power level compatible with state-of-the-art hybrid silicon lasers

Eisenstein Series of Weight One, q-Averages of the 0-Logarithm and Periods of Elliptic Curves

For any elliptic curve E over k ⊂ R with E(C) = C^×/q^Z, q = e^(2πiz),Im(z) >, we study the q-average D_(0,q), defined on E(C), of the function D_0(z) = Im(z/(1−z)). Let Ω+(E) denote the real period of E. We show that there is a rational function R ∈ Q(X_1(N)) such that for any non-cuspidal real point s ∈ X_1(N) (which defines an elliptic curve E(s) over R together with a point P(s) of order N), πD_(0,q)(P(s)) equals Ω+(E(s))R(s). In particular, if s is Q-rational point of X_1(N), a rare occurrence according to Mazur, R(s) is a rational number