Exciton spectroscopy of hexagonal boron nitride using non-resonant x-ray Raman scattering

We report non-resonant x-ray Raman scattering (XRS) measurements from hexagonal boron nitride for transferred momentum from 2 to 9 $\mathrm{\AA}^{-1}$ along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calculations of the projected density of states in the spherical harmonics basis, reveals that a strong pre-edge feature is a dominantly $Y_{10}$-type Frenkel exciton with no other \textit{s}-, \textit{p}-, or \textit{d}- components. This conclusion is supported by a second, independent calculation of the \textbf{q}-dependent XRS cross-section based on the Bethe-Salpeter equation

X-ray Raman scattering study of aligned polyfluorene

We present a non-resonant inelastic x-ray scattering study at the carbon K-edge on aligned poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] and show that the x-ray Raman scattering technique can be used as a practical alternative to x-ray absorption measurements. We demonstrate that this novel method can be applied to studies on aligned $\pi$-conjugated polymers complementing diffraction and optical studies. Combining the experimental data and a very recently proposed theoretical scheme we demonstrate a unique property of x-ray Raman scattering by performing the symmetry decomposition on the density of unoccupied electronic states into $s$- and $p$-type symmetry contributions.Comment: 19 pages, 8 figure

GINZBURG-LANDAU THEORY OF VORTICES IN dd-WAVE SUPERCONDUCTORS

Ginzburg-Landau theory is used to study the properties of single vortices and of the Abrikosov vortex lattice in a $d_{x^2-y^2}$ superconductor. For a single vortex, the $s$-wave order parameter has the expected four-lobe structure in a ring around the core and falls off like $1/r^2$ at large distances. The topological structure of the $s$-wave order parameter consists of one counter-rotating unit vortex, centered at the core, surrounded by four symmetrically placed positive unit vortices. The Abrikosov lattice is shown to have a triangular structure close to $T_c$ and an oblique structure at lower temperatures. Comparison is made to recent neutron scattering data.Comment: 4 pages, REVTeX, 3 figures available upon reques

Ginzburg-Landau Theory for a p-Wave Sr_2RuO_4 Superconductor: Vortex Core Structure and Extended London Theory

Based on a two dimensional odd-parity superconducting order parameter for Sr_2RuO_4 with p-wave symmetry, we investigate the single vortex and vortex lattice structure of the mixed phase near H_{c1}. Ginzburg-Landau calculations for a single vortex show a fourfold structure with an orientation depending on the microscopic Fermi surface properties. The corresponding extended London theory is developed to determine the vortex lattice structure and we find near H_{c1} a centered rectangular vortex lattice. As the field is increased from H_{c1} this lattice continuously deforms until a square vortex lattice is achieved. In the centered rectangular phase the field distribution, as measurable through \mu-SR experiments, exhibits a characteristic two peak structure (similar to that predicted in high temperature and borocarbide superconductors).Comment: 12 pages, 7 figure

Grain Boundary Induced Magneto-Far Infrared Resonances in Superconducting YBa2_2Cu3_3O7−δ_{7-\delta } Thin Films

Spectral features induced by 45$^{\circ }$ in-plane misoriented grains have been observed in the far infrared magneto-transmission of YBa$_2$Cu$_3$O$_{7-\delta }$ thin films. Two strong dispersive features are found at 80 and 160 $cm^{-1}$ and a weaker one at 116 $cm^{-1}$. The data can be well represented by Lorentzian oscillator contributions to the conductivity. Several possible interpretations are discussed. We conclude that the resonances are due to vortex core excitations.Comment: Latex file (14 pages) + 4 Postscript figures, uuencode

5-Year health-related quality of life outcome in patients with idiopathic normal pressure hydrocephalus

Background Health-related quality of life (HRQoL) is severely impaired in persons with idiopathic normal pressure hydrocephalus (iNPH). The HRQoL improves in a number of patients after the placement of a cerebrospinal fluid (CSF) shunt, but long-term follow-up of HRQoL is rare. Methods Extended follow-up (60 months) of a prospective cohort study involving 189 patients with iNPH who underwent shunt surgery. Preoperative variables were used to predict favorable HRQoL outcome (improvement or non-deterioration) measured by the 15D instrument 5 years after shunting. Results Out of the 189 initially enrolled study participants, 88 had completed 5-year HRQoL follow-up (46%), 64 had died (34%), and 37 (20%) failed to complete the HRQoL follow-up but were alive at the end of the study. After initial post-operative HRQoL improvement, HRQoL deteriorated so that 37/88 participants (42%) had a favorable HRQoL outcome 5 years after shunting. Multivariate binary logistic regression analysis indicated that younger age (adjusted OR 0.86, 95% CI 0.77-0.95; p <0.005), lower body mass index (adjusted OR 0.87, 95% CI 0.77-0.98; p <0.05) and better Mini-Mental State Examination performance (adjusted OR 1.16, 95% CI 1.01-1.32; p <0.05) before surgery predicted favorable 5-year outcome. Conclusions This extended follow-up showed that the self-evaluated HRQoL outcome is associated with iNPH patients' pre-operative cognitive status, overweight and age. The post-operative deterioration may reflect the natural progression of iNPH, but also derive from aging and comorbidities. It indicates a need for long-term follow-up.Peer reviewe

Field induced dx2−y2+idxyd_{x^2-y^2}+id_{xy} state and marginal stability of high-Tc superconductors

It is shown that the {\em complex} $d_{xy}$ component is generated in d-wave superconductor in the magnetic field. As one enters superconducting state at finite field the normal to superconducting transition occurs into bulk $d_{x^2-y^2}+i d_{xy}$ state . The driving force for the transition is the linear coupling between magnetic field and non zero magnetization of the $d_{x^2-y^2}+i d_{xy}$ condensate. The external magnetic field violates parity and time reversal symmetries and the nodal quasiparticle states respond by generating the $id_{xy}$ component of the order parameter, with the magnitude estimated to be on the order of few Kelvin. Parity (P) and time reversal (T) symmetries are violated in this state.Comment: 4 pages, latex file with two eps figure file

Критерии энергоаудита сельскохозяйственных предприятий: новые подходы и оценки (по промежуточным результатам российско-финляндского проекта)

Currently implemented project “Russian-Finnish Bioeconomy Competence Сentre – BioCom” within South-East Finland – Russia Cross-Border Cooperation Programme 2014-2020 aims to integrate the BioEconomy principles and approaches into the agricultural sector of the neighbouring border areas of Russia and Finland. The energy efficiency of farming and sustainable use of energy resources is one of the fundamentals of the bio-economy concept. The energy audit is the first step in identifying opportunities to reduce the energy inputs on the farms.(Research purpose) To discover the new approaches to the energy auditing of agricultural enterprises and new assessment indicators following the project experience.(Materials and methods) Four farms were selected for the energy inspection – two farms located in the Leningrad Region, Russia, and two farms located in the South Savo Region, Finland. In Russia the standard energy auditing, measurement, and calculation procedure was applied. The systems of electrical power supply, heat supply, water supply, sewage, and building envelopes on the farms were examined and estimated.(Results and discussion) Following the outcomes of the energy audits in the project framework and the previous relevant experience, the basic energy-saving and efficiency improvement measures were established. Three new approaches to the energy auditing of agricultural enterprises were suggested – energy and environmental assessment of applied technologies and equipment; consideration of the application of renewable energy-generating sources; consideration of the conversion of vehicles to biogas.(Conclusions) The study outcomes proved the energy audits to play an important role in improving the energy efficiency of agricultural production provided they are mandatory, take into account the energy environmental assessment criteria, consider the application of renewable energy-generating sources and the conversion of vehicles to biogas.Реализуемый в настоящее время проект «Российско-финляндский центр компетенции в области биоэкономики – BioCom» в рамках Программы приграничного сотрудничества Юго-Восточной Финляндии и России на 2014-2020 годы направлен на интеграцию принципов и подходов биоэкономики в сельскохозяйственный сектор соседних приграничных районов России и Финляндии. Подтвердили, что энергоэффективность сельского хозяйства и устойчивое использование энергоресурсов составляют одну из основ концепции биоэкономики. Показали необходимость проведения энергоаудита при определении возможностей для снижения энергозатрат в сельском хозяйстве.(Цель исследования) Выявить новые подходы к энергоаудиту сельхозпредприятий и показатели оценки на основе опыта реализации проекта.(Материалы и методы) Для энергетического обследования выбрали четыре хозяйства – два в Ленинградской области, Россия, и два в регионе Южное Саво, Финляндия. В России применяли стандартную процедуру энергоаудита, измерений и расчетов. Обследовали и оценили системы электро-, тепло-, водоснабжения, канализации и ограждающих конструкций.(Результаты и обсуждение). По результатам энергетических аудитов в рамках проекта и предыдущего соответствующего опыта установили основные меры по энергосбережению и повышению энергоэффективности. Предложили три новых подхода к энергоаудиту сельскохозяйственных предприятий: энергоэкологическую оценку применяемых технологий и оборудования; рассмотрение вопроса об использовании возобновляемых источников энергии; изучение возможности перевода транспорта на биогаз.(Выводы) Подтвердили необходимость энергоаудита в целях повышения энергоэффективности сельскохозяйственного производства. Показали, что энергетические обследования должны учитывать критерии энергоэкологической оценки, возможность применения возобновляемых источников энергии и перевода транспортных средств на биогаз

Vortex lattice structure in a d_{x^2-y^2}-wave superconductor

The vortex lattice structure in a d_{x^2-y^2}-wave superconductor is investigated near the upper critical magnetic field in the framework of the Ginzburg Landau theory extended by including the correction terms such as the higher order derivatives derived from the Gor'kov equation. On lowering temperature, the unit cell shape of the vortex lattice gradually varies from a regular triangular lattice to a square lattice through the shape of an isosceles triangle. As for the orientation of the vortex lattice, the base of an isosceles triangle is along the a axis or the b axis of the crystal. The fourfold symmetric structure around a vortex core is also studied in the vortex lattice case. It is noted that these characteristic features appear even in the case the induced s-wave order parameter is absent around the vortex of the d_{x^2-y^2}-wave superconductivity. We also investigate the effect of the induced s-wave order parameter. It enhances (suppresses) these characteristic features of the d_{x^2-y^2}-wave superconductor when the s-wave component of the interaction is attractive (repulsive).Comment: 20 pages, RevTex, 9 figures in 3 PS-files and 5 GIF-file