Superfluid Interfaces in Quantum Solids

One scenario for the non-classical moment of inertia of solid He-4 discovered by Kim and Chan [Nature 427, 225 (2004)] is the superfluidity of micro-crystallite interfaces. On the basis of the most simple model of a quantum crystal--the checkerboard lattice solid--we show that the superfluidity of interfaces between solid domains can exist in a wide range of parameters. At strong enough inter-particle interaction, a superfluid interface becomes an insulator via a quantum phase transition. Under the conditions of particle-hole symmetry, the transition is of the standard U(1) universality class in 3D, while in 2D the onset of superfluidity is accompanied by the interface roughening, driven by fractionally charged topological excitations.Comment: 4 revtex4 page

Evaluation of the PV cell operation temperature in the process of fast switching to open-circuit mode

A procedure for measuring the overheating temperature (ΔT ) of a p-n junction area in the structure of photovoltaic (PV) cells converting laser or solar radiations relative to the ambient temperature has been proposed for the conditions of connecting to an electric load. The basis of the procedure is the measurement of the open-circuit voltage (VO C ) during the initial time period after the fast disconnection of the external resistive load. The simultaneous temperature control on an external heated part of a PV module gives the means for determining the value of VO C at ambient temperature. Comparing it with that measured after switching OFF the load makes the calculation of ΔT possible. Calibration data on the VO C = f(T ) dependences for single-junction AlGaAs/GaAs and triple-junction InGaP/GaAs/Ge PV cells are presented. The temperature dynamics in the PV cells has been determined under flash illumination and during fast commutation of the load. Temperature measurements were taken in two cases: converting continuous laser power by single-junction cells and converting solar power by triple-junction cells operating in the concentrator modules

Increasing the quantum efficiency of InAs/GaAs QD arrays for solar cells grown by MOVPE without using strain-balance technology

Research into the formation of InAs quantum dots (QDs) in GaAs using the metalorganic vapor phase epitaxy technique ispresented. This technique is deemed to be cheaper than the more often used and studied molecular beam epitaxy. The bestconditions for obtaining a high photoluminescence response, indicating a good material quality, have been found among awide range of possibilities. Solar cells with an excellent quantum ef?ciency have been obtained, with a sub-bandgapphoto-response of 0.07 mA/cm2per QD layer, the highest achieved so far with the InAs/GaAs system, proving the potentialof this technology to be able to increase the ef?ciency of lattice-matched multi-junction solar cells and contributing to abetter understanding of QD technology toward the achievement of practical intermediate-band solar cells

УПРАВЛЕНИЕ МИКРОСТРУКТУРОЙ И СВОЙСТВАМИ ФЕРРИТОВ С ПОМОЩЬЮ ДВУХСТАДИЙНОГО СИНТЕЗА

Two−phase influence on microstructure and property of ferrite of different purpose was investigated. It is shown that fine dispersed component doped at the second step (milling) effectively brakes growth of grains, promoting reception of dense, homogeneous, fine−grained ferrite materials. Thus such properties as initial magnetic permeability, mechanical strength essentially raise and magnetic losses decrease. Change of modes of baking allows to receive coarse−grained homogeneous materials.Influence of two−phase synthesis on a microstructure and property nickel−zinc, manganese−zinc, lithium−titanic ferrite spinels is more below considered discussed.Исследовано влияние двухстадийного синтеза на микроструктуру и свойства ферритов различного назначения. Показано, что мелкодисперсный компонент, вводимый на второй стадии (при измельчении), эффективно тормозит рост зерен, способствуя получению плотных, однородных, мелкозернистых ферритовых материалов. При этом существенно повышаются начальная магнитная проницаемость, механическая прочность и их воспроизводимость, а магнитные потери уменьшаются. Изменение режимов спекания позволяет получать крупнозернистые одно-родные материалы.Ниже рассмотрено влияние двухстадийного синтеза на микроструктуру и свойства никельцинковых и магний−цинковых феррошпинелей

MODELING OF LOGP FOR HYDROCARBON COMPOUNDS

ABSTRACT A method for calculation of partition coefficient LogP is introduced. The method is based on an atomic additive scheme. LogP value is obtained as a sum of individual contributions of each atom of the molecule. The atom contributions called increments correspond to atom classes derived on the base of local atomic properties. Increment values are calculated by means of linear regression applied for a set of hydrocarbon compounds. Test results are presented and discussed

Mutual Effect of Components of Protective Films Applied on Copper and Brass from Octadecylamine and 1,2,3-Benzotriazole Vapors

It has been shown by a set of corrosion, electrochemical and physical methods that a chamber corrosion inhibitor that consists of a mixture of octadecylamine (ODA) and benzotriazole (BTA) efficiently protects copper and brass from atmospheric corrosion and can be used for the temporary protection of metal items. The optimum temperatures of treatment with the ODA + BTA mixed inhibitor is 120 °C for brass and 100 °C for copper. One-hour treatment in ODA + BTA vapors at these temperatures results in the formation of nanosized adsorption films on the surface of these metals. These films stabilize the passive state and provide efficient temporary protection of metal items. The ODA + BTA inhibitor is superior to its components in terms of protective aftereffect. Our analysis of the mutual effect of BTA and ODA indicated that they show an antagonism of protective action on copper, but there is also a synergistic enhancement in the case of brass. Electrochemical impedance spectroscopy studies demonstrate that the inhibitors in question mainly act by using a blocking mechanism on copper and brass. Chamber treatment of the metals studied in vapors of the ODA + BTA mixture resulted in a noticeable hydrophobization of the copper surface and an insignificant effect on the brass surface. Chamber treatment of copper samples with artificially created polymodal roughness made it possible to obtain a superhydrophobic surface

Autofluorescence and White Light Bronchoscopy in the Diagnosis of Endobronchial Malignant Lesions

Background: Autofluorescence bronchoscopy (AFB) allows a more sensitive approach to the diagnosis of premalignant and malignant endobronchial lesions than white light bronchoscopy (WLB) can do