Absence of superconductivity in iron polyhydrides at high pressures

Recently, C. M. Pépin et al. [Science 357, 382 (2017)] reported the formation of several new iron polyhydrides FeHx at pressures in the megabar range and spotted FeH5, which forms above 130 GPa, as a potential high-Tc superconductor because of an alleged layer of dense metallic hydrogen. Shortly after, two studies by A. Majumdar et al. [Phys. Rev. B 96, 201107 (2017)] and A. G. Kvashnin et al. [J. Phys. Chem. C 122, 4731 (2018)] based on ab initio Migdal-Eliashberg theory seemed to independently confirm such a conjecture. We conversely find, on the same theoretical-numerical basis, that neither FeH5 nor its precursor, FeH3, shows any conventional superconductivity and explain why this is the case. We also show that superconductivity may be attained by transition-metal polyhydrides in the FeH3 structure type by adding more electrons to partially fill one of the Fe-H hybrid bands (as, e.g., in NiH3). Critical temperatures, however, will remain low because the d-metal bonding, and not the metallic hydrogen, dominates the behavior of electrons and phonons involved in the superconducting pairing in these compounds

Модификация состава лесообразующих пород ЗАО Bakonyerdő в лесничестве Papa

Были исследованы медленно растущие леса из робинии псевдоакации на площади 250 га в лесничестве Pápa ЗАО Bakonyerdő на трех пробных площадях (Egyházaskesző, Kemeneshőgyész, Magyargencs). Леса на выбранных ПП достигнут возраста рубки в течение следующего 10-летнего периода лесной таксации. Задачей работы было выяснение взаимосвязи между параметрами древостоя и индексами выхода древесины

Visible-light induced emulsion photopolymerization with carbon nitride as stabilizer and photoinitiator

Photopolymerization is a common method in the synthesis of polymers with various applications. Herein, a simple and effective route for surfactant-free emulsion photopolymerization (EPP) under visible light irradiation is described. Therein, graphitic carbon nitride (g-CN) was utilized as an stabilizer and a photoinitiator at the same time. As such, g-CN provides the starting point for polymer chain growth and particle formation. Notably, the as-prepared polymer latexes are directly crosslinked by g-CN, and the existence of g-CN is confirmed inside of the particle, as well as outside, where it forms relatively stable latexes. Moreover, surface functionalized g-CN was utilized to tailor the g-CN/monomer interactions for improved particle formation. g-CN quantum dots with enhanced photoluminescence properties were introduced in EPP as well, providing polymer latexes with enhanced photoluminescence. The obtained polymer nanoparticles might be promising candidates for bioimaging applications

Measurement of the Permanent Electric Dipole Moment of the 129^{129}Xe Atom

We report on a new measurement of the CP-violating permanent Electric Dipole Moment (EDM) of the neutral $^{129}$Xe atom. Our experimental approach is based on the detection of the free precession of co-located nuclear spin-polarized $^3$He and $^{129}$Xe samples. The EDM measurement sensitivity benefits strongly from long spin coherence times of several hours achieved in diluted gases and homogeneous weak magnetic fields of about 400~nT. A finite EDM is indicated by a change in the precession frequency, as an electric field is periodically reversed with respect to the magnetic guiding field. Our result, $\left(-4.7\pm6.4\right)\cdot 10^{-28}$ ecm, is consistent with zero and is used to place a new upper limit on the $^{129}$Xe EDM: $|d_\text{Xe}|<1.5 \cdot 10^{-27}$ ecm (95% C.L.). We also discuss the implications of this result for various CP-violating observables as they relate to theories of physics beyond the standard model

Nucleosynthesis in the Early Galaxy

Recent observations of r-process-enriched metal-poor star abundances reveal a non-uniform abundance pattern for elements $Z\leq47$. Based on non-correlation trends between elemental abundances as a function of Eu-richness in a large sample of metal-poor stars, it is shown that the mixing of a consistent and robust light element primary process (LEPP) and the r-process pattern found in r-II metal-poor stars explains such apparent non-uniformity. Furthermore, we derive the abundance pattern of the LEPP from observation and show that it is consistent with a missing component in the solar abundances when using a recent s-process model. As the astrophysical site of the LEPP is not known, we explore the possibility of a neutron capture process within a site-independent approach. It is suggested that scenarios with neutron densities $n_{n}\leq10^{13}$ $cm^{-3}$ or in the range $n_{n}\geq10^{24}$ $cm^{-3}$ best explain the observations.Comment: 28 pages, 7 Postscript figures. To be published in The Astrophysical Journa

Visible-light induced emulsion photopolymerization with carbon nitride as stabilizer and photoinitiator

Photopolymerization is a common method in the synthesis of polymers with various applications. Herein, a simple and effective route for surfactant-free emulsion photopolymerization (EPP) under visible light irradiation is described. Therein, graphitic carbon nitride (g-CN) was utilized as an stabilizer and a photoinitiator at the same time. As such, g-CN provides the starting point for polymer chain growth and particle formation. Notably, the as-prepared polymer latexes are directly crosslinked by g-CN, and the existence of g-CN is confirmed inside of the particle, as well as outside, where it forms relatively stable latexes. Moreover, surface functionalized g-CN was utilized to tailor the g-CN/monomer interactions for improved particle formation. g-CN quantum dots with enhanced photoluminescence properties were introduced in EPP as well, providing polymer latexes with enhanced photoluminescence. The obtained polymer nanoparticles might be promising candidates for bioimaging applications

The bearable lightness of being

How are philosophical questions about what kinds of things there are to be understood and how are they to be answered? This paper defends broadly Fregean answers to these questions. Ontological categories-such as object, property, and relation-are explained in terms of a prior logical categorization of expressions, as singular terms, predicates of varying degree and level, etc. Questions about what kinds of object, property, etc., there are are, on this approach, reduce to questions about truth and logical form: for example, the question whether there are numbers is the question whether there are true atomic statements in which expressions function as singular terms which, if they have reference at all, stand for numbers, and the question whether there are properties of a given type is a question about whether there are meaningful predicates of an appropriate degree and level. This approach is defended against the objection that it must be wrong because makes what there depend on us or our language. Some problems confronting the Fregean approach-including Frege's notorious paradox of the concept horse-are addressed. It is argued that the approach results in a modest and sober deflationary understanding of ontological commitments