Normal and Lateral Casimir Forces between Deformed Plates

The Casimir force between macroscopic bodies depends strongly on their shape and orientation. To study this geometry dependence in the case of two deformed metal plates, we use a path integral quantization of the electromagnetic field which properly treats the many-body nature of the interaction, going beyond the commonly used pairwise summation (PWS) of van der Waals forces. For arbitrary deformations we provide an analytical result for the deformation induced change in Casimir energy, which is exact to second order in the deformation amplitude. For the specific case of sinusoidally corrugated plates, we calculate both the normal and the lateral Casimir forces. The deformation induced change in the Casimir interaction of a flat and a corrugated plate shows an interesting crossover as a function of the ratio of the mean platedistance H to the corrugation length \lambda: For \lambda \ll H we find a slower decay \sim H^{-4}, compared to the H^{-5} behavior predicted by PWS which we show to be valid only for \lambda \gg H. The amplitude of the lateral force between two corrugated plates which are out of registry is shown to have a maximum at an optimal wavelength of \lambda \approx 2.5 H. With increasing H/\lambda \gtrsim 0.3 the PWS approach becomes a progressively worse description of the lateral force due to many-body effects. These results may be of relevance for the design and operation of novel microelectromechanical systems (MEMS) and other nanoscale devices.Comment: 20 pages, 5 figure

Combined effect of coherent Z exchange and the hyperfine interaction in atomic PNC

The nuclear spin-dependent parity nonconserving (PNC) interaction arising from a combination of the hyperfine interaction and the coherent, spin-independent, PNC interaction from Z exchange is evaluated using many-body perturbation theory. For the 6s-7s transition in 133Cs, we obtain a result that is about 40% smaller than that found previously by Bouchiat and Piketty [Phys. Lett. B 269, 195 (1991)]. Applying this result to 133Cs, leads to an increase in the experimental value of nuclear anapole moment and exacerbates differences between constraints on PNC meson coupling constants obtained from the Cs anapole moment and those obtained from other nuclear parity violating experiments. Nuclear spin-dependent PNC dipole matrix elements, including contributions from the combined weak-hyperfine interaction, are also given for the 7s-8s transition in 211Fr and for transitions between ground-state hyperfine levels in K, Rb, Cs, Ba+, Au, Tl, Fr, and Ra+.Comment: Revtex4 preprint 19 pages 4 table

Constraints on dark matter particles charged under a hidden gauge group from primordial black holes

In order to accommodate increasingly tighter observational constraints on dark matter, several models have been proposed recently in which dark matter particles are charged under some hidden gauge group. Hidden gauge charges are invisible for the standard model particles, hence such scenarios are very difficult to constrain directly. However black holes are sensitive to all gauge charges, whether they belong to the standard model or not. Here, we examine the constraints on the possible values of the dark matter particle mass and hidden gauge charge from the evolution of primordial black holes. We find that the existence of the primordial black holes with reasonable mass is incompatible with dark matter particles whose charge to mass ratio is of the order of one. For dark matter particles whose charge to mass ratio is much less than one, we are able to exclude only heavy dark matter in the mass range of 10^(11) GeV - 10^(16) GeV. Finally, for dark matter particles whose charge to mass ratio is much greater than one, there are no useful limits coming from primordial black holes.Comment: accepted for publication in JCA

IBPOWER Project, Intermediate band materials and solar cells for photovoltaics with high efficiency and reduced cost

IBPOWER is a Project awarded under the 7th European Framework Programme that aims to advance research on intermediate band solar cells (IBSCs). These are solar cells conceived to absorb below bandgap energy photons by means of an electronic energy band that is located within the semiconductor bandgap, whilst producing photocurrent with output voltage still limited by the total semiconductor bandgap. IBPOWER employs two basic strategies for implementing the IBSC concept. The first is based on the use of quantum dots, the IB arising from the confined energy levels of the electrons in the dots. Quantum dots have led to devices that demonstrate the physical operation principles of the IB concept and have allowed identification of the problems to be solved to achieve actual high efficiencies. The second approach is based on the creation of bulk intermediate band materials by the insertion of an appropriate impurity into a bulk semiconductor. Under this approach it is expected that, when inserted at high densities, these impurities will find it difficult to capture electrons by producing a breathing mode and will cease behaving as non-radiative recombination centres. Towards this end the following systems are being investigated: a) Mn: In1-xGax N; b) transition metals in GaAs and c) thin films

A White Paper on keV sterile neutrino Dark Matter

We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos

Study of plants of genus stachys on the example of Betonicaofficinalisl. Within the scientific course “pharmaceutical remake”

The paper describes a retrospective analysis of the use of common betony in traditional and modern medicine. The Stachys plants have not been used in modern domestic medicine yet. Therefore, based on the historical experience of the use of common betony in traditional medicine, we have emphasized its value as a plant with high therapeutic potential. In this study, we used the so-called “Pharmaceutical remake”, intended to revive interest in the now-forgotten objects of flora, which were previously widely used in medicine. The polyphenol structure of betony grass was studies with the use of the reverse-phase and graduate elution high-performance liquid chromatography. The presence of glycosides of diosmin, acacetin, luteolin and apigenin was established. The grass also contains hydroxycinnamic acids such as chlorogenic and rosemary acids, with the latter dominating in the polyphenol complex. The composition of plant terpenes in a hexane extraction has been studied by gas-liquid chromatography with mass spectrometric detection. It was determined that the terpenoid composition of betony is mainly represented by sesquiterpens: aromadendrene and germacrene, and monoterpenes: 3-carene and dihydrocarveol. © 2016, International Journal of Pharmacy and Technology. All rights reserved

An innovative way for extraction of essential oil components from Pimpinella anisum L. fruits

Objective: The aim of this article was to test the hypothesis about the possibility for extraction of essential oil components from the plant raw material (PRM) by the example of Pimpinella anisum L. fruits with two different perfluoro organic solvents, Novec 1230 and Novec 7100. Methods: For the studies, we used Pimpinella anisum L. fruits ground to obtain particle size between 0.1 and 0.5 mm. The study of qualitative and quantitative content of the extracts was carried out by the following method: simple maceration, PRM: extractant ratio 1:10 w/v; and circulation method for extraction using Soxhlet extractor, PRM: extractant ratio 1:5 w/v. Qualitative analysis of extracts was carried out by gas chromatography-mass spectrometry (GC-MS) method. Quantitative analysis of trans-anethole in the extracts was carried out by reverse phase high-performance liquid chromatography (RP HPLC) method. Results: The largest yield of anethole was observed for n-hexane, 84±4 %, and for Novec 7100, 81±4 %. In case of Novec 1230 solvent, the yield of anethole was noted to be three times less, 32±2 %. The yield of anethole under the conditions of solvents (Novec 1230 and Novec 7100) circulation method was up to 94±5 % within two hours. Conclusion: Adequacy of the working hypothesis about the possibility for extraction of essential oil components from Pimpinella anisum L. fruits by two different perfluoro organic solvents, Novec 1230 and Novec 7100, was verified experimentally. In the context of the solvents tested, it was found that the level of fluorination of the solvent’s molecule had a great influence on its extraction properties in regard to anethole and vegetable oil. © 2019 The Authors