Modelling of potentials for interparticle interactions between methanol molecules

Peculiarities of interparticle interactions between methanol molecules in the methanol vapor are investigated. The bare potential is considered as a sum of repulsive, dispersive and electrostatic forces. It is supposed that H-bond is of electrostatic nature (the irreducible contribution caused by overlapping of electronic shells is unessential). The dispersive interaction is approximated with London's formula, the electrostatic interaction is modelled by a multipole expansion up to dipole-octupole contribution. The multipole moments are assumed to be equal to their experimental values or to quantum chemical calculations. The repulsion is modelled by power potential, whose parameters are fitted to the second virial coefficient and to the parameters of dimers. Along with the bare potential, the averaged potential of interparticle interaction is analyzed. It is shown that the repulsive potential has an exponent $n=28$. The multipole potential, presented in this paper, is scrupulously compared with the potential known as the OPLS.Comment: 10 pages, 4 figures, 8 table

From ‘red Manchester’ to ‘red Disneyland’: constructivist architecture and the representation of Ivanovo

The article was submitted on 05.04.2016.Рассматривается роль конструктивистской архитектуры в культурно-историческом наследии города Иваново (до 1932 г. – Иваново-Вознесенска). Будучи к рубежу XIX–XX вв. крупным текстильным центром, город стал в 1918 г. центром новой губернии, а в 1929 г. – центром крупной промышленной области. Стремительный рост численности населения требовал эффективного решения жилищных проблем, а новый административный статус города предполагал создание соответствующей инфраструктуры. Это определило активное использование Иваново-Вознесенска как образцового социалистического города передовых архитектурных и инженерных идей. В городе были созданы рабочие поселки, реализовавшие идею «города-сада», а во второй половине 1920-х – начале 1930-х гг. по проектам московских, ленинградских и местных архитекторов был возведен ряд объектов в стиле конструктивизма. В 1950-х гг. некоторые из них были реконструированы, а в 1970-е два уникальных объекта были уничтожены. Вплоть до конца 1990-х гг. архитектурное наследие 1920–1930-х гг. не рассматривалось как важная часть культурного наследия города в различных репрезентационных практиках. Только с начала XXI в. в рамках выставочной деятельности Ивановского художественного музея и Музея промышленности и искусства актуализируется ценность авангардного наследия, частью которого являются сохранившиеся ансамбли конструктивистской застройки. В настоящее время перспективность использования раннесоветской культуры в репрезентационных практиках находит все больше и больше понимания в СМИ и административных учреждениях, курирующих работу с культурным наследием. По мнению автора, позиционирование Иваново на разных этапах советской истории как «красного Манчестера», «родины первого Совета», «третьей пролетарской столицы» дает уникальную возможность для использования этого символического капитала в рамках «красного туризма».The author studies the role of constructivist architecture in the cultural and historical heritage of the city of Ivanovo (known as Ivanovo-Voznesensk before 1932). Due to its becoming a large textiles center by the turn of the 20th century, the city transformed into the center of a new governorate in 1918 and the center of a major industrial region in 1929. As its population was rapidly growing, certain housing issues needed to be addressed and the new administrative status of the city implied the development of a proper infrastructure. This determined the formation of Ivanovo-Voznesensk as a model socialist city of pioneer architectural and engineering solutions. There appeared work settlements that realized the idea of a ‘garden city’, and in the second half of the 1920s – early 1930s, a few constructivist buildings designed by Moscow, Leningrad and local architects were built. During the 1950s, some of them were remodeled, and later on in the 1970s two unique buildings were demolished. Until the late 1990s, the architectural heritage of the 1920s – 1930s had not been regarded as an important part of the cultural heritage of the city. It was only as late as the 21st century that the value of the avant-garde heritage (whose part is the remaining constructivist ensemble of the city) was recognized by means of the activity of the Ivanovo Fine Arts Museum and the Museum of Industry and Arts. At present, more and more emphasis is put on the use of early Soviet culture in representation practices both by the media and administrative structures, controlling the work with the cultural heritage. According to the author, the fact that Ivanovo was at different stages of Soviet history represented as a ‘red Manchester’, the ‘homeland for the first Soviet’, and the ‘third proletarian capital’ makes it possible to use the architecture of the city as a unique symbolic asset in the project of ‘red tourism’

Single-shot single-gate RF spin readout in silicon

For solid-state spin qubits, single-gate RF readout can help minimise the number of gates required for scale-up to many qubits since the readout sensor can integrate into the existing gates required to manipulate the qubits (Veldhorst 2017, Pakkiam 2018). However, a key requirement for a scalable quantum computer is that we must be capable of resolving the qubit state within single-shot, that is, a single measurement (DiVincenzo 2000). Here we demonstrate single-gate, single-shot readout of a singlet-triplet spin state in silicon, with an average readout fidelity of $82.9\%$ at a $3.3~\text{kHz}$ measurement bandwidth. We use this technique to measure a triplet $T_-$ to singlet $S_0$ relaxation time of $0.62~\text{ms}$ in precision donor quantum dots in silicon. We also show that the use of RF readout does not impact the maximum readout time at zero detuning limited by the $S_0$ to $T_-$ decay, which remained at approximately $2~\text{ms}$. This establishes single-gate sensing as a viable readout method for spin qubits

Вероятность ошибочной регистрации данных в однофотонном канале связи стирающего типа с приёмником на основе счётчика фотонов

When measuring low-power optical signals, it is necessary to ensure the highest reliability of the received data, which is especially important for single-photon communication channels. This determines the expediency of using photon counters as receiving modules for such channels. They are highly sensitive, but are characterized by data recording errors. Therefore, the purpose of this work was to investigate the influence of the intensity of the registered optical radiation J0 during the transmission of binary symbols “0” on the probability of registering symbols “1” at the output of the communication channel in the presence of symbols “0” at its input P(1/0).The statistical distributions of the mixture of the number of dark and signal pulses at the output of the photon counter during the registration of binary symbols “0” Pst0 (N ) were determined. To do this, a technique was used to reduce information loss. As a result, the minimum probability P(1/0) was reached.The probabilities P(1/0) were calculated for a communication channel containing a photon counter as a receiving module. This calculation was carried out at different values of the supply voltage of the avalanche photodetector U and the intensity of the optical signal used to transmit the binary symbols “0” J0 .The experimental results showed that with increasing optical signal intensity J0 , the dependences P(1/0) on J0 initially remain almost unchanged and retain a constant value. However, with a further increase in J0 , there is a linearly increasing character of the dependences P(1/0) on J0 . Moreover, with other equal reception parameters, such a character of the dependences P(1/0) on J0 begins to manifest itself at higher intensities of the optical signal J0 with an increase in the supply voltage of the avalanche photodetector.При измерении маломощных оптических сигналов, передаваемых в каналах однофотонной связи, приёмные модули должны обеспечивать наибольшую достоверность принятых данных.В этой связи целесообразно использовать счётчики фотонов, которые являются высокочувствительными, однако характеризуются ошибками регистрации данных. Поэтому цель работы– исследовать влияние интенсивности регистрируемого оптического излучения J0 при передаче двоичных символов «0» на вероятность регистрации на выходе канала связи символов «1» при наличии символов «0» на его входе P(1/0).На основе методики уменьшения потерь информации определены статистические распределения смеси числа темновых и сигнальных импульсов на выходе счётчика фотонов при регистрации двоичных символов «0» Pst0 (N ), при которых вероятность P(1/0) минимальная.Определены вероятности P(1/0) для канала связи, содержащего в качестве приёмного модуля счётчик фотонов при различных значениях напряжения питания лавинного фотоприёмника Uпит и интенсивности оптического сигнала, используемого для передачи двоичных символов «0» J0 .Экспериментальные результаты показали, что с увеличением интенсивности оптического сигнала J0 зависимости P(1/0) от J0 вначале практически не изменяются и сохраняют постоянную величину. Однако при дальнейшем увеличении J0 имеет место линейно возрастающий характер зависимостей P(1/0) от J0 . Причём при прочих равных параметрах приёма такой характер зависимостей P(1/0) от J0 начинает проявляться при бо́льших интенсивностях оптического сигнала J0 с увеличением напряжения питания лавинного фотоприёмника

Principal-component-based population structure adjustment in the North American Rheumatoid Arthritis Consortium data: impact of single-nucleotide polymorphism set and analysis method

Population structure occurs when a sample is composed of individuals with different ancestries and can result in excess type I error in genome-wide association studies. Genome-wide principal-component analysis (PCA) has become a popular method for identifying and adjusting for subtle population structure in association studies. Using the Genetic Analysis Workshop 16 (GAW16) NARAC data, we explore two unresolved issues concerning the use of genome-wide PCA to account for population structure in genetic associations studies: the choice of single-nucleotide polymorphism (SNP) subset and the choice of adjustment model. We computed PCs for subsets of genome-wide SNPs with varying levels of LD. The first two PCs were similar for all subsets and the first three PCs were associated with case status for all subsets. When the PCs associated with case status were included as covariates in an association model, the reduction in genomic inflation factor was similar for all SNP sets. Several models have been proposed to account for structure using PCs, but it is not yet clear whether the different methods will result in substantively different results for association studies with individuals of European descent. We compared genome-wide association p-values and results for two positive-control SNPs previously associated with rheumatoid arthritis using four PC adjustment methods as well as no adjustment and genomic control. We found that in this sample, adjusting for the continuous PCs or adjusting for discrete clusters identified using the PCs adequately accounts for the case-control population structure, but that a recently proposed randomization test performs poorly

Second harmonic electromagnetic emission of a turbulent magnetized plasma driven by a powerful electron beam

The power of second harmonic electromagnetic emission is calculated for the case when strong plasma turbulence is excited by a powerful electron beam in a magnetized plasma. It is shown that the simple analytical model of strong plasma turbulence with the assumption of a constant pump power is able to explain experimentally observed bursts of electromagnetic radiation as a consequence of separate collapse events. It is also found that the electromagnetic emission power calculated for three-wave interaction processes occurring in the long-wavelength part of turbulent spectrum is in order-of-magnitude agreement with experimental results

Inhomogeneous Quasi-stationary States in a Mean-field Model with Repulsive Cosine Interactions

The system of N particles moving on a circle and interacting via a global repulsive cosine interaction is well known to display spatially inhomogeneous structures of extraordinary stability starting from certain low energy initial conditions. The object of this paper is to show in a detailed manner how these structures arise and to explain their stability. By a convenient canonical transformation we rewrite the Hamiltonian in such a way that fast and slow variables are singled out and the canonical coordinates of a collective mode are naturally introduced. If, initially, enough energy is put in this mode, its decay can be extremely slow. However, both analytical arguments and numerical simulations suggest that these structures eventually decay to the spatially uniform equilibrium state, although this can happen on impressively long time scales. Finally, we heuristically introduce a one-particle time dependent Hamiltonian that well reproduces most of the observed phenomenology.Comment: to be published in J. Phys.

Probability of Erroneous Data Registration in a Single Photon Erasure-Type Communication Channel with a Receiver Based on a Photon Counter

When measuring low-power optical signals, it is necessary to ensure the highest reliability of the received data, which is especially important for single-photon communication channels. This determines the expediency of using photon counters as receiving modules for such channels. They are highly sensitive, but are characterized by data recording errors. Therefore, the purpose of this work was to investigate the influence of the intensity of the registered optical radiation J0 during the transmission of binary symbols “0” on the probability of registering symbols “1” at the output of the communication channel in the presence of symbols “0” at its input P(1/0). The statistical distributions of the mixture of the number of dark and signal pulses at the output of the photon counter during the registration of binary symbols “0” Pst0 (N ) were determined. To do this, a technique was used to reduce information loss. As a result, the minimum probability P(1/0) was reached. The probabilities P(1/0) were calculated for a communication channel containing a photon counter as a receiving module. This calculation was carried out at different values of the supply voltage of the avalanche photodetector U and the intensity of the optical signal used to transmit the binary symbols “0” J0 . The experimental results showed that with increasing optical signal intensity J0 , the dependences P(1/0) on J0 initially remain almost unchanged and retain a constant value. However, with a further increase in J0 , there is a linearly increasing character of the dependences P(1/0) on J0 . Moreover, with other equal reception parameters, such a character of the dependences P(1/0) on J0 begins to manifest itself at higher intensities of the optical signal J0 with an increase in the supply voltage of the avalanche photodetector

The Josephson heat interferometer

The Josephson effect represents perhaps the prototype of macroscopic phase coherence and is at the basis of the most widespread interferometer, i.e., the superconducting quantum interference device (SQUID). Yet, in analogy to electric interference, Maki and Griffin predicted in 1965 that thermal current flowing through a temperature-biased Josephson tunnel junction is a stationary periodic function of the quantum phase difference between the superconductors. The interplay between quasiparticles and Cooper pairs condensate is at the origin of such phase-dependent heat current, and is unique to Josephson junctions. In this scenario, a temperature-biased SQUID would allow heat currents to interfere thus implementing the thermal version of the electric Josephson interferometer. The dissipative character of heat flux makes this coherent phenomenon not less extraordinary than its electric (non-dissipative) counterpart. Albeit weird, this striking effect has never been demonstrated so far. Here we report the first experimental realization of a heat interferometer. We investigate heat exchange between two normal metal electrodes kept at different temperatures and tunnel-coupled to each other through a thermal `modulator' in the form of a DC-SQUID. Heat transport in the system is found to be phase dependent, in agreement with the original prediction. With our design the Josephson heat interferometer yields magnetic-flux-dependent temperature oscillations of amplitude up to ~21 mK, and provides a flux-to-temperature transfer coefficient exceeding ~ 60mK/Phi_0 at 235 mK [Phi_0 2* 10^(-15) Wb is the flux quantum]. Besides offering remarkable insight into thermal transport in Josephson junctions, our results represent a significant step toward phase-coherent mastering of heat in solid-state nanocircuits, and pave the way to the design of novel-concept coherent caloritronic devices.Comment: 4+ pages, 3 color figure