Dynamics of methyl radical formation by 266 nm photolysis of xylenes and mesitylene

The 266 nm photodissociation of three xylene isomers and mesitylene leading to the formation of methyl radical was examined. The kinetic energy release profiles for the methyl radical were almost identical for all the three isomers of xylene and mesitylene, while substantial differences were observed for the corresponding profiles of the co-fragment produced by loss of one methyl group. This observation be attributed to the formation of the methyl radical from alternate channels. The total kinetic energy distribution profiles were rationalized based on the dissociation of {sp2}C–C{sp3} bond in the cationic state, wherein the {sp2}C–C{sp3} bond dissociation energy is lowered relative to the ground state. The dissocaiton in the cationic state follows a resonant three-photon absorption process, resulting in maximum total kinetic energy of about 1.6 – 1.8 eV for the photofragments. A results in. Fitting of the TKER distribution profiles to empirical function reveals that the dynamics of {sp2}C–C{sp3} bond dissociation is insensitive to the position of substitution but marginally dependent on the number of methyl groups.

Comparative Analysis of Methods for Mathematical Modeling of Specific Electrical Conductivity of Plasma in the Channel of an Electric Discharge in Water

In the present work, a comparative analysis of three methods for determining the specific electrical conductivity of the plasma formed in the channel of an electric discharge in water is carried out for its mathematical modeling. The parameters of the empirical function are determined, at which the results of mathematical modeling are consistent with the experimental data. The necessity of using empirical functions in calculating the specific electrical conductivity of plasma has been substantiated. The obtained ratios made it possible to significantly increase the adequacy of the previously developed mathematical model of the physical discharge processes in water and to expand the range of parameters in which it can be used.

BUFFER SYSTEMS BASED ON AMINOMETANESULPHONATE AND MONOETHANOLAMMONIUM N-ALKYLAMINOMETHANESULPHONATES

The limits of the pH buffering action (pHbuff) of YNHCH2SO3H – NH2CH2CH2OH –H2O (Y = H, CH3, HOCH2CH2, t-С4H9 and C6H5CH2) were determined and their buffer capacity (p) for monoethanolamine (MEA) was estimated in the temperature range 293–313 K. For systems with aminomethanesulfonic acid (AMSA), its N‑methyl, N‑hydroxyethyl (HEAMSA) and N‑benzyl (BzAMSA) derivatives, an increase in temperature leads to a decrease in the pH values of the lower limit of the buffering action of their solutions with monoethanolamine; in the case of N‑tert-butylaminomethanesulfonic acid (t-BuAMSA) – to an increase in the specified characteristic. An increase in temperature for systems with the most hydrophobic t-BuAMSA and BzAMSA (in comparison with other studied aminomethanesulfonic acids) leads to a decrease in the pH values of the upper limit of the buffer action. A decrease in the YNHCH2SO3H and NH2CH2CH2OH concentration leads to a shift in the boundaries of the pH of the buffering action to a more acidic region. The nature of the influence of the empirical function, combining their acid-base properties and lipophilicity (рKа + lgPow), on the concentration dependence of the buffer capacity according to MEA was revealed. It is shown that the buffering effect of the studied systems is due to the presence, in addition to the systems N‑alkylammoniummethanesulfonate – N‑alkylaminomethanesulfonate and 2-hydroxyethylammonium – monoethanolamine, ionic associates (pairs and triples). The position of the extrema on the graphical π=f(CMEA)/QYAMSA) dependencies for systems with hydrophilic AMSA and HEAMSA coincides with the position of the first minima on the differential titration curves dpH/dV = f(CMEA)/QYAMSA). Substitution of MEA to potassium aminomethanesulfonate leads to a shift in the pH buffering action to a more acidic region and increases the buffer capacity of the resulting systems.

DETERMINATION OF WIRE SWING BOOM OF OVERHEAD POWER TRANSMISSION LINES IN ICE FORMATION MONITORING DEVICE BASED ON PHYSICAL SIMULATION RESULTS

Стрела провеса является важным параметром для безопасной эксплуатации воздушных линий электропередачи и может быть использована в качестве одного из основополагающих критериев анализа интенсивности гололедообразования. В данной статье рассматривается возможность определения стрелы провеса при закреплении на одном из проводов фазы датчика, измеряющего угол между проводом и плоскостью земли в непосредственной близости от опоры. Для формализации эмпирической зависимости был проведен натурный эксперимент, моделирующий физические свойства провеса провода ВЛ, размещенного на опорах. Обработка полученных данных и аппроксимация эмпирической функции была реализована в среде MATLAB. После обработки данных была получена эмпирическая функция, которая может быть использована в автономных системах мониторинга для контроля стрелы провеса провода. Автономное устройство мониторинга гололедной обстановки на проводах ВЛ, разработанное авторами, для которого была найдена рассматриваемая эмпирическая зависимость, позволяет следить за интенсивностью гололедообразования, а также контролировать массу гололедных отложений и среднюю толщину стенки гололеда. Информация о гололедной обстановке передается на диспетчерский пункт посредством GSM модема. Увеличение интенсивности гололедных отложений вызывает увеличение стрелы провеса провода, относительно его колебаний, обусловленных технологическими параметрами, поэтому система мониторинга гололеда включающая анализ угла провеса провода является аналогом тензометрических датчиков тяжения, но не требует реконструкции ВЛ и отключения последней на время модернизации. Устройство оборудовано также дополнительными датчиками, что позволяет увеличить вероятность правильного обнаружения опасной гололедной обстановки. The sagging boom is an important parameter for the safe operation of overhead power lines and can be used as one of the fundamental criteria for the analysis of ice formation intensity. This article discusses the possibility of determining the sagging boom when a sensor phase is fixed to one of the wires, which measures the angle between the wire and the ground plane in the immediate vicinity of the support. To formalize empirical dependence, a full-scale experiment was conducted that simulates the physical properties of the LL wire held on supports. The processing of the obtained data and the approximation of the empirical function were implemented in the MATLAB environment. After processing the data, an empirical function was obtained that can be used in autonomous monitoring systems to control the wire sagging boom.An Autonomous device for monitoring the ice situation on the overhead lines, developed by the authors, for which the empirical dependence was found, al-lows to monitor the intensity of ice formation, as well as to control the mass of ice deposits and the average thickness of the ice wall. Information about the ice condi-tions is transferred to the control station via GSM modem. An autonomous device for monitoring the ice situation on VL wires, developed by the authors, for which the considered empirical dependence was found, allows you to monitor the intensity of ice formation, as well as control the mass of ice deposits and the average thickness of the ice wall. Ice information is transmitted to the control room via the GSM modem. Increasing the intensity of icy deposits causes an increase in the wire sag boom relative to its fluctuations due to process parameters, therefore, the ice monitoring system including analysis of the wire sag angle is an analogue of strain gauges, but does not require reconstruction of the VL and disconnection of the latter during modernization. The device is also equipped with additional sensors, which increases the probability of correct detection of a dangerous ice situation.

Study on the Diffusion Rate of the Charge Carrier Transport in Regio-Random and Regio-Regular P3HT

Muon spin relaxation experiment has been conducted to probe the hopping mechanism in the poly(3-hexylthiophene-2,5-diyl) (P3HT) for both types of regio-random (Rdm) and regio-regular (RR). In this study we have performed calculations over the collected data to obtain the parallel and perpendicular diffusion rates, at temperatures of 10 K and 300 K. The calculation is based on the fitting method to the empirical function that relates the relaxation rate with the diffusion rates. For Rdm-P3HT, we have obtained the parallel diffusion rate to be 5.43 x 1013 rad/s at 300 K and 4.90 x 1014 rad/s at 10 K. While the perpendicular diffusion rates are 5.29 x 108 rad/s at 300 K and 1.88 x 106 rad/s at 10 K. For RR-P3HT, we have obtained the parallel diffusion rate to be 1.04 x 1014 rad/s at 300 K and 1.28 x 1015 rad/s at 10 K. While the perpendicular diffusion rates are 6.10 x 108 rad/s at 300 K and 5.35 x 105 at 10 K. The diffusion rates of RR-P3HT are higher than that of Rdm-P3HT, especially in the parallel direction. In both types of material, the parallel diffusion rate decreased with temperature, while the perpendicular diffusion rate increased with temperature, showing a change of behavior from 1D to 3D direction of charge transport.

Reaction Kinetic Models of Antibiotic Heteroresistance

Bacterial heteroresistance (i.e., the co-existence of several subpopulations with different antibiotic susceptibilities) can delay the clearance of bacteria even with long antibiotic exposure. Some proposed mechanisms have been successfully described with mathematical models of drug-target binding where the mechanism’s downstream of drug-target binding are not explicitly modeled and subsumed in an empirical function, connecting target occupancy to antibiotic action. However, with current approaches it is difficult to model mechanisms that involve multi-step reactions that lead to bacterial killing. Here, we have a dual aim: first, to establish pharmacodynamic models that include multi-step reaction pathways, and second, to model heteroresistance and investigate which molecular heterogeneities can lead to delayed bacterial killing. We show that simulations based on Gillespie algorithms, which have been employed to model reaction kinetics for decades, can be useful tools to model antibiotic action via multi-step reactions. We highlight the strengths and weaknesses of current models and Gillespie simulations. Finally, we show that in our models, slight normally distributed variances in the rates of any event leading to bacterial death can (depending on parameter choices) lead to delayed bacterial killing (i.e., heteroresistance). This means that a slowly declining residual bacterial population due to heteroresistance is most likely the default scenario and should be taken into account when planning treatment length.

Increasing the efficiency and accuracy of the ABACUS protein sequence design method

Motivation The ABACUS (a backbone-based amino acid usage survey) method uses unique statistical energy functions to carry out protein sequence design. Although some of its results have been experimentally verified, its accuracy remains improvable because several important components of the method have not been specifically optimized for sequence design or in contexts of other parts of the method. The computational efficiency also needs to be improved to support interactive online applications or the consideration of a large number of alternative backbone structures. Results We derived a model to measure solvent accessibility with larger mutual information with residue types than previous models, optimized a set of rotamers which can approximate the sidechain atomic positions more accurately, and devised an empirical function to treat inter-atomic packing with parameters fitted to native structures and optimized in consistence with the rotamer set. Energy calculations have been accelerated by interpolation between pre-determined representative points in high-dimensional structural feature spaces. Sidechain repacking tests showed that ABACUS2 can accurately reproduce the conformation of native sidechains. In sequence design tests, the native residue type recovery rate reached 37.7%, exceeding the value of 32.7% for ABACUS1. Applying ABACUS2 to designed sequences on three native backbones produced proteins shown to be well-folded by experiments. Availability and implementation The ABACUS2 sequence design server can be visited at http://biocomp.ustc.edu.cn/servers/abacus-design.php. Supplementary information Supplementary data are available at Bioinformatics online.

Estimating the mass of CMEs from the analysis of EUV dimmings

Context. Reliable estimates of the mass of coronal mass ejections (CMEs) are required to quantify their energy and predict how they affect space weather. When a CME propagates near the observer’s line of sight, these tasks involve considerable errors, which motivated us to develop alternative means for estimating the CME mass. Aims. We aim at further developing and testing a method that allows estimating the mass of CMEs that propagate approximately along the observer’s line of sight. Methods. We analyzed the temporal evolution of the mass of 32 white-light CMEs propagating across heliocentric heights of 2.5–15 R⊙, in combination with that of the mass evacuated from the associated low coronal dimming regions. The mass of the white-light CMEs was determined through existing methods, while the mass evacuated by each CME in the low corona was estimated using a recently developed technique that analyzes the dimming in extreme-UV (EUV) images. The combined white-light and EUV analyses allow the quantification of an empirical function that describes the evolution of CME mass with height. Results. The analysis of 32 events yielded reliable estimates of the masses of front-side CMEs. We quantified the success of the method by calculating the relative error with respect to the mass of CMEs determined from white-light STEREO data, where the CMEs propagate close to the plane of sky. The median for the relative error in absolute values is ≈30%; 75% of the events in our sample have an absolute relative error smaller than 51%. The sources of uncertainty include the lack of knowledge of piled-up material, subsequent additional mass supply from the dimming region, and limitations in the mass-loss estimation from EUV data. The proposed method does not rely on assumptions of CME size or distance to the observer’s plane of sky and is solely based on the determination of the mass that is evacuated in the low corona. It therefore represents a valuable tool for estimating the mass of Earth-directed events.

Permeability of mine tailings measured in triaxial cell

The execution of permeability tests using a triaxial cell makes it possible to eliminate the uncertainties that characterize tests performed using conventional equipment. This paper contains the results of 48 tests carried out on three materials recovered from tailings of Riotinto mines (Spain). The equipment involved a modified triaxial system to facilitate the execution of permeability tests under constant head. The tests were performed on samples consolidated to 50, 100, 200, and 300 kPa for four different hydraulic gradients established by applying a backpressure difference (ΔBp). The magnitude of the backpressure difference was applied as a percentage of the initial effective consolidation pressure, expressed as ΔBp/[Formula: see text]; namely, values of 10%, 15%, 20%, and 25%, which resulted in hydraulic gradients between 5 and 80. The backpressure (Bp) was constant (400 kPa) in all cases, allowing a degree of saturation close to 100% to be achieved. This was verified by calculating Skempton’s B parameter, which was very close to unity in all cases. The results indicate that it is feasible to define an empirical function including the coefficient of permeability (k) and the effective consolidation pressure ([Formula: see text]), the mean effective confining pressure ([Formula: see text]), and the backpressure differential (ΔBp).