Multiple scattering of matter waves: an analytic model of the refractive index for atomic and molecular gases

We present an analytic model of the refractive index for matter waves propagating through atomic or molecular gases. The model, which combines a WKB treatment of the long range attraction with the Fraunhofer model treatment of the short range repulsion, furnishes a refractive index in compelling agreement with recent experiments of Jacquey et al. [Phys. Rev. Lett. 98, 240405 (2007)] on Li atom matter waves passing through dilute noble gases. We show that the diffractive contribution, which arises from scattering by a two dimensional "hard core" of the potential, is essential for obtaining a correct imaginary part of the refractive index.Comment: 5 pages, 1 figure, 2 table

Influence of lecithins on disorders of cognitive functions of animals caused by tetrachloromethane.

In our time the study of the influence of soya and especially sunflower lecithin as one of the natural monopolies inUkraine, on the state of cognitive functions is relevant. Specified neurotropic activity of lecithin is characterized by the obstacle to the development of behavioral manifestations of neurotoxic action of carbon tetrachloride, prevention of inhibition of mobility, research, unconditional reflex activity. In this article the determination of the effects of soy lecithin (L), and sunflower lecithin on a state of cognitive processes in rats showed that there is no significant differences between them. Changes in memory were judged by conventional passive-defensive reactions. Conditional reaction of passive avoidance (passive avoidance reaction) was produced on the basis of a single electric-skin support. We proposed modified method of assessing the presence of individually obtained memory trace and a group of genetically fixed form of memory. The establishment of this fact allows to make a comparative analysis of changes caused by the two lecithins in reproduction of individually obtainjed memory trace. Lecithin, derived from both plants in the conditions of intoxication by carbon tetrachloride prevents and improves reproduction of conditional reaction of passive avoidance. Soy lecithin and sunflower lecithin prevent the development of behavioral manifestations of neurotoxic action of carbon tetrachloride, preventing inhibition of mobility, research, unconditional reflex activity, cause expressive anti-amnesic effect contributing to the course of protective instinctive behavior in recognition of new circumstances as a safe. Both lecithins of plant origin exhibit the improving effect on the course of cognitive processes and their neuro-hormonal mechanisms in conditions of poisoning with carbon tetrachloride. Sunflower lecithin has more antidepressive, nootropic effect whereas soy lecithin has been demonstrated to have significant anti-amnestic effect

An analytic model of rotationally inelastic collisions of polar molecules in electric fields

We present an analytic model of thermal state-to-state rotationally inelastic collisions of polar molecules in electric fields. The model is based on the Fraunhofer scattering of matter waves and requires Legendre moments characterizing the "shape" of the target in the body-fixed frame as its input. The electric field orients the target in the space-fixed frame and thereby effects a striking alteration of the dynamical observables: both the phase and amplitude of the oscillations in the partial differential cross sections undergo characteristic field-dependent changes that transgress into the partial integral cross sections. As the cross sections can be evaluated for a field applied parallel or perpendicular to the relative velocity, the model also offers predictions about steric asymmetry. We exemplify the field-dependent quantum collision dynamics with the behavior of the Ne-OCS($^{1}\Sigma$) and Ar-NO($^2\Pi$) systems. A comparison with the close-coupling calculations available for the latter system [Chem. Phys. Lett. \textbf{313}, 491 (1999)] demonstrates the model's ability to qualitatively explain the field dependence of all the scattering features observed

Quasiparticle Interference on the Surface of Topological Crystalline Insulator Pb(1-x)Sn(x)Se

Topological crystalline insulators represent a novel topological phase of matter in which the surface states are protected by discrete point group-symmetries of the underlying lattice. Rock-salt lead-tin-selenide alloy is one possible realization of this phase which undergoes a topological phase transition upon changing the lead content. We used scanning tunneling microscopy (STM) and angle resolved photoemission spectroscopy (ARPES) to probe the surface states on (001) Pb$_{1-x}$Sn$_{x}$Se in the topologically non-trivial (x=0.23) and topologically trivial (x=0) phases. We observed quasiparticle interference with STM on the surface of the topological crystalline insulator and demonstrated that the measured interference can be understood from ARPES studies and a simple band structure model. Furthermore, our findings support the fact that Pb$_{0.77}$Sn$_{0.23}$Se and PbSe have different topological nature.Comment: 5 pages, 4 figure

Conventional superconductivity at 203 K at high pressures

A superconductor is a material that can conduct electricity with no resistance below its critical temperature (Tc). The highest Tc that has been achieved in cuprates1 is 133 K at ambient pressure2 and 164 K at high pressures3. As the nature of superconductivity in these materials has still not been explained, the prospects for a higher Tc are not clear. In contrast, the Bardeen-Cooper-Schrieffer (BCS) theory gives a guide for achieving high Tc and does not put bounds on Tc, all that is needed is a favorable combination of high frequency phonons, strong electron-phonon coupling, and a high density of states. These conditions can be fulfilled for metallic hydrogen and covalent compounds dominated by hydrogen4,5. Numerous calculations support this idea and predict Tc of 50-235 K for many hydrides6 but only moderate Tc=17 K has been observed experimentally7. Here we studied sulfur hydride8 where a Tc~80 K was predicted9. We found that it transforms to a metal at pressure ~90 GPa. With cooling superconductivity was found deduced from a sharp drop of the resistivity to zero and a decrease of Tc with magnetic field. The pronounce isotope shift of Tc in D2S is evidence of an electron-phonon mechanism of superconductivity that is consistent with the BCS scenario. The superconductivity has been confirmed by magnetic susceptibility measurements with Tc=203K. The high Tc superconductivity most likely is due to H3S which is formed from H2S under its decomposition under pressure. Even higher Tc, room temperature superconductivity, can be expected in other hydrogen-based materials since hydrogen atoms provide the high frequency phonon modes as well as the strong electron-phonon coupling

Proposal for realizing Majorana fermions in chains of magnetic atoms on a superconductor

We propose an easy-to-build easy-to-detect scheme for realizing Majorana fermions at the ends of a chain of magnetic atoms on the surface of a superconductor. Model calculations show that such chains can be easily tuned between trivial and topological ground states. In the latter, spatially resolved spectroscopy can be used to probe the Majorana fermion end states. Decoupled Majorana bound states can form even in short magnetic chains consisting of only tens of atoms. We propose scanning tunneling microscopy as the ideal technique to fabricate such systems and to probe their topological properties

The use of titanium alloys for details of downhole hammers

The influence of cementation technology of titanium alloy Ti-Al-Mn on its wear resistance is studied. It is established that after lubrication a friction pair with mineral oil the wear resistance of the cemented titanium alloy is comparable to wear resistance of the tempered steel 12HN3A, and in water medium surpasses it by 1.5 times. Decrease in the tendency to seizure with steel is the main reason for increase of wear resistance of titanium alloy. Industrial tests of the ASH43 hammer have shown that the use of titanium alloys for the manufacture of hammer strikers allows to increase impact capacity by 1.5 times and to increase drilling rate by 30 % compared to hammers with steel strikers

Trait peculiarities of diabetic retinopathy individuals

The purpose of the research was to study proliferative and non-proliferative retinopathy diabetes’ traits. It was examined 30 diabetic retinopathy patients (Type I – 12 persons and Type II – 18 persons) during an open-label controlled study. 20 patients were diagnosed with a non-proliferative stage of diabetic retinopathy, and 10 patients were diagnosed with a proliferative stage. The peculiarities of retinopathy diabetes’ traits were determined by the method of R. Ketell. All diabetic retinopathy patients were characterized by independence, suspicion, anxiety, uncertainty, concern, timidity, lack of motivation, self-confidence, conservatism, discipline. Non-proliferative diabetic retinopathy patients’ traits were carelessness, suspicion, independence, insensitivity, conflict, developed self-control, self-confidence, callousness, conservatism, low motivation, skepticism, rigidity of thinking. The serious problems for these individuals were their conservatism, doubts about new ideas, skepticism, cynicism, pragmatism; the moderate ones were seclusion, distrust, silo mentality, difficulty in mastering new material, low motivation, laziness, ease, a tendency to comply with the rules, the desire to introduce oneself “in a favourable position”. The leading traits of proliferative diabetic retinopathy people were suspicion, self-confidence, developed self-control, responsibility, conservatism, self-confidence, anxiety, irritability and pessimism. Conservatism and doubts about new ideas were the most difficult problems for these individuals; the moderate ones are seclusion, distrust, silo mentality, difficulty in mastering new material, low tolerance for emotional factors, self-doubt, irritability, frequent manifestation of excitement, increased caution, discretion, restraint, sometimes pessimism desire to be in the shadows, preference for a limit of close friends, excessive selfconfidence, subjectivism, hypertrophied desire for independence, stubbornness, skepticism, sometimes cynicism, pragmatism, low motivation and laziness. Prospects for further research are the need to determine the impact of emotional, motivational and intellectual characteristics of diabetic retinopathy patients and their impact on quality of life and the formation of compliance. Дроздов В.О., Сакович В.М., Сакович Є.М., Фокіна С.М. Особливості характеру осіб з діабетичною ретинопатією. Метою дослідження було вивчення особливостей характеру хворих із проліферативною та непроліферативною стадіями діабетичної ретинопатії. Відкритим контрольованим дослідженням було охоплено 30 хворих із діабетичною ретинопатією, з них: у 12 і 18 було діагностовано цукровий діабет І і ІІ типу, у 20 осіб діагностовано непроліферативну стадію діабетичної ретинопатії, у 10 – проліферативну. Особливості характеру осіб з діабетичною ретинопатією визначено за методикою Р. Кетелла. Усім хворим з діабетичною ретинопатією були притаманні незалежність, підозрілість, тривожність, невпевненість, заклопотаність, боязкість, недостатня мотивація, самовпевненість, консерватизм, дисциплінованість. Особливостями характеру пацієнтів з непроліферативною діабетичною ретинопатією були безтурботність, підозрілість, незалежність, нечутливість. Конфліктність, розвинений самоконтроль, самовпевненість, консерватизм, низька мотивація, скептицизм, ригідність мислення. Найвиразнішими в них були консерватизм, сумніви щодо нових ідей, скептицизм, цинізм, прагматизм; менш виразними – замкнутість, недовіра, обмежене мислення, труднощі щодо засвоєння нового матеріалу, низька мотивація, лінощі, незворушність, схильність до усвідомленого дотримання норм, бажання уявити себе «у вигідному світлі». До особливостей характеру осіб з проліферативною діабетичною ретинопатією можна зарахувати підозрілість, самовпевненість, розвинений самоконтроль, відповідальність, консерватизм, самовпевненість, тривожність, роздратованість, песимізм. Найвиразнішими у них були консерватизм, сумніви щодо нових ідей; менш виразними – замкненість, недовіра, обмежене мислення, труднощі в засвоєнні нового матеріалу, низька толерантність до емоціогенних чинників, невпевненість у собі, роздратованість, часті прояви хвилювання, підвищена обережність, розсудливість, стриманість, іноді песимізм, сировість, виразна сором’язливість, боязкість, обережність, перевага вузького кола людей, надмірна самовпевненість, цинізм, прагматизм, лінощі. Перспективами подальших досліджень є необхідність вивчення впливу емоційних, мотиваційних та інтелектуальних особливостей хворих з діабетичною ретинопатією та їх впливу на якість життя та формування комплайєнсу

Electron energy relaxation under terahertz excitation in (Cd1−xZnx)3As2 Dirac semimetals

We demonstrate that measurements of the photo-electromagnetic effect using terahertz laser radiation provide an argument for the existence of highly conductive surface electron states with a spin texture in Dirac semimetals (Cd₁-xZnx)₃As