The orbits of outer planetary satellites using the Gaia data

Launch of the Gaia space observatory started a new era in astrometry when the accuracy of star coordinates increased by thousands of times. Significant improvement of accuracy was also expected for the coordinates of the Solar system bodies. Gaia DR3 provided us with the data which could be used to test our expectations. In this work, we refine the orbits of a number of outer planetary satellites using both ground-based and Gaia observations. From thirteen outer satellites observed by Gaia, we chose six to obtain their orbits. Some specific moments in using observations of outer satellites made by Gaia are demonstrated. These pecularities stem from scanning motion of Gaia, in particular from the fact that the accuracy of observations is significantly different along and across the scanning direction. As expected, Gaia observations proved to be more precise than those made from Earth, which results in more accurate satellite ephemerides. We estimate accuracy of the ephemerides of considered satellites for the interval between 1996 and 2030. As astrometric positions published in Gaia DR3 were not corrected for the relativistic light deflection by the Sun, we took into account this effect, which slightly diminished the rms residuals. In addition, relativistic light deflection by the giant planets was estimated, which, as it turned out, can be neglected with the given accuracy of Gaia observations.Comment: accepted in MNRAS 28.03.2023, 9 pages, 8 figure

Особенности изготовления отливок из алюминиевых сплавов по выжигаемым аддитивным FDM-моделям

This article describes the results of a study aimed at improving production technology of experimental castings from aluminum alloys by investment casting using models produced by 3D printing. The consumable models were produced using fused deposition modeling (FDM). Biodegradable polylactide (PLA) was used as a material for the models. In order to decrease the surface roughness of consumable PLA  model.  chemical  post-treatment  by  dichloromethane  needs  to  be  performed.  After  immersion  of  the  model  into the solvent for 10s, its surface becomes smooth and glossy. Three-point static bending tests of PLA plates demonstrated a mechanical strength of average ~45.1 MPa. A thermomechanical analysis of polylactide demonstrated that in the course of heating of ceramic shell in excess of 150 °C, the polylactide model begins to expand intensively by exerting significant pressure on the ceramic shell. In order to decrease stress during the removal of polylactide model from ceramic mold, the heating time in the range of 150–300 °C needs to be heated to a maximum. The use of hollow consumable casting models with a cellular structure not higher than 30 % is also sensible. The stresses on the shell will not exceed its strength. Characteristic  temperature  properties  of  PLA  plastic  thermal  destruction  were detected using thermogravimetric analysis. Polylactide was established to completely burn out upon  heating  to 500  °C  leaving  no ash residue. Analysis of the results identified the burning modes of polylactide models from ceramic molds. Using a Picaso 3D Designer printer (Russia), the PLA models were printed used for production of experimental castings from aluminum alloys. It was revealed that the surface roughness (Ra) of a casting produced using a consumable model treated by dichloromethane decreases by 81.75 %: from 13.7 to 2.5 μm.Приведены результаты исследований, направленные на совершенствование литейной технологии получения опытно-экспериментальных отливок из алюминиевых сплавов методом литья по выжигаемым моделям, изготовленным с применением 3D-печати. Для создания выжигаемых моделей использовали метод осаждения расплавленной нити (FDM – fused deposition modeling), а в качестве материала моделей был выбран биоразлагаемый материал – полилактид (PLA – polylactide). Установлено, что для уменьшения  шероховатости  выжигаемой  PLA-модели  необходимо  проводить  химическую  постобработку ее поверхности дихлорметаном. В результате окунания модели в растворитель на 10 с она приобретает гладкую и глянцевую поверхность. Испытания механической прочности PLA-пластин на трехточечный статический изгиб показали, что данный показатель составляет в среднем ~ 45,1 МПа. Термомеханический анализ полилактида выявил, что в процессе нагрева керамической оболочки выше 150 °С полилактидная модель начинает интенсивно расширяться, оказывая существенное давление на керамическую оболочку. Для уменьшения напряжений в процессе удаления полилактидной модели из керамической формы необходимо максимально увеличить время нагрева в интервале температур 150–300 °С, а также целесообразно использовать пустотелые выжигаемые модели отливки со степенью заполнения ячеистой структуры не более 30 %. При этом напряжения в оболочке не будут превышать ее прочность. С помощью термогравиметрического анализа выявлены характерные температурные характеристики термодеструкции PLA-пластика. Установлено, что материал из полилактида полностью  выгорает  при нагреве до температуры 500 °С, не оставляя после себя остатков золы. Анализ результатов позволил определить технологические режимы выжигания полилактидных моделей из керамических форм. На принтере Picaso 3D Designer (Россия) были напечатаны PLA-модели, которые  использовали  для  получения  опытно-экспериментальных  отливок  из  алюминиевых  сплавов.  Выявлено, что шероховатость поверхности (Ra)  отливки,  полученной  по  выжигаемой  модели,  обработанной  дихлорметаном,  уменьшается на 81,75 % – с 13,7 до 2,5 мкм

A method for calculating the enthalpy of hydrophobic effect

A new method for calculating the enthalpy of hydrophobic effect for compounds incapable of specific interactions with water was suggested. The method is based on separating the enthalpy of hydration into the contributions from nonspecific hydration and hydrophobic effect. The contribution from nonspecific hydration was determined by a method described previously. The enthalpies of hydrophobic effect for inert gases, alkanes, aromatic hydrocarbons, and their derivatives were determined. It was found that the enthalpy of hydrophobic effect for inert gases and alkanes is negative and independent of the size of the molecule dissolved in water. For aromatic compounds, the enthalpy is positive; it increases with the molecular size. © Pleiades Publishing, Inc., 2006

Non-perturbative vacuum-polarization effects in proton-laser collisions

In the collision of a high-energy proton beam and a strong laser field, merging of the laser photons can occur due to the polarization of vacuum. The probability of photon merging is calculated by accounting exactly for the laser field and presents a highly non-perturbative dependence on the laser intensity and frequency. It is shown that the non-perturbative vacuum-polarization effects can be experimentally measured by combining the next-generation of table-top petawatt lasers with presently available proton accelerators.Comment: 5 pages, 2 figure

Calculating the Gibbs energy of hydrogen bonding for proton acceptors with a solvent in methanol solutions

We propose a method for calculating the Gibbs energies of hydrogen bonding of solutes with associated solvents via the thermodynamic analysis of experimental values of solvation Gibbs energies. The method is applied to solutions of different proton acceptors in methanol. It is shown that the contribution of hydrogen bonding processes to the solvation Gibbs energy in methanol is in most cases very different in magnitude from the formation Gibbs energy of equimolar complexes of the solute and methanol. We demonstrate the need to include the contributions from solvophobic effects in investigating intermolecular interactions in associated solvents by means of thermodynamic data. © 2011 Pleiades Publishing, Ltd

Speed of Sound, Density, and Related Thermodynamic Excess Properties of Binary Mixtures of 2-Pyrrolidone and N-Methyl-2-pyrrolidone with Acetonitrile and Chloroform

© 2016 American Chemical Society.Densities and speeds of sound were measured for binary mixtures of 2-pyrrolidone or N-methyl-2-pyrrolidone with acetonitrile or chloroform at temperatures of (293.15 to 323.15) K and at atmospheric pressure, with uncertainties of 0.5 kg·m-3 and 0.5 m·s-1, respectively. From the measured speeds and densities, isentropic compressibilities and molar excesses of volume, isentropic compression, and thermal expansion were calculated. All of the excesses are negative, which is due to the geometries of the molecules and changes in the hydrogen bonding upon mixing. In the simplest case of the N-methyl-2-pyrrolidone + acetonitrile system, the negative excesses result only from the different sizes of the molecules because the components are incapable of forming either self- or cross-associates. For the other systems, the net effects of the formation and/or dissociation of the hydrogen bonds lead to bigger negative excesses of molar volume and thermal expansion. The negative excesses of compression are probably caused mainly by filling of the gaps between the big lactam molecules with the smaller acetonitrile or chloroform molecules, while the formation of the hydrogen-bonded cross-associates plays a minor role

Enthalpy of cooperative hydrogen bonding in the complexes of triethyl- and tri-n-butylamines with alcohols: Effect of the alkyl chain length

The measurements of enthalpies of triethylamine and tri-n-butylamine dissolution in aliphatic alcohols and, vice versa, of aliphatic alcohols in amines were carried out. Enthalpies of specific interactions in the studied systems were calculated. The enthalpy of specific interaction determined in the alcohol medium, are significantly less than those obtained at dissolving alcohols in amines. The mechanism of specific interaction of amines with alcohols is discussed. Enthalpies of cooperative hydrogen bonds of tertiary amines with alcohol clusters are calculated. The dependences between the enthalpies of hydrogen bond and the spatial structure of interacting molecules are revealed. © 2010 Pleiades Publishing, Ltd

Thermochemistry of dissolution, solvation, and hydrogen bonding of anilines in proton-acceptor organic solvents at 298.15 K

© 2014 Pleiades Publishing, Ltd. Enthalpies of dissolution at infinite dilution (298.15 K) of aniline, N-methylaniline, and N,N-dimethylaniline in a series of proton-acceptor solvents of different classes of compounds have been measured. The solvation enthalpies have been determined, and its relationship with the anilines structure has been analyzed. Enthalpy of hydrogen bonding in the complexes of aniline (1: 2) and N-methylaniline (1: 1) with the solvents has been calculated. In the case of aniline complexes, negative cooperativity of hydrogen bonding has been revealed, the effect enhancing with increasing the solvent proton-acceptor ability

Thermodynamics of the hydrogen bonding of nitrogen-containing cyclic and aromatic compounds with proton donors: The structure-property relationship

© 2014 Pleiades Publishing, Ltd. Enthalpies of dissolution are measured at infinite dilution of nitrogen-containing cyclic (pyrrolidine, piperidine) and aromatic compounds (aniline, N-methylaniline, N,N-dimethylaniline, N-methylimidazole, pyridine, 2-, 3-, 4-methylpyridine, pyrrole, N-methylpyrrole) in chloroform and dichloromethane, and vice versa (T = 298.15 K). The enthalpies of hydrogen bonds in the above systems are calculated. Relationships between resulting thermochemical data and the structure of nitrogen-containing cyclic and aromatic compounds are explored

The ability of ionic liquids to form hydrogen bonds with organic solutes evaluated by different experimental techniques. Part I. Alkyl substituted imidazolium and sulfonium based ionic liquids

© 2018 This work is devoted to the quantitative study of hydrogen bond formation of N-alkyl substituted ionic liquids with proton acceptor and proton donor organic solvents. 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [BMIM][NTf2], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO], 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], triethylsulfonium bis(trifluoromethylsulfonyl)imide [Et3S][NTf2], 1-butyl-3-methylimidazolium tricyanomethanide [BMIM][TCM], 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF4] were investigated by solution calorimetry and FTIR-spectroscopy techniques. The stretching vibration region of C[dbnd]O group of 2-pentanone in mixture with N-alkyl substituted ionic liquid in inert solvent carbon tetrachloride was analyzed at different concentrations of components for the estimation of proton donor ability of ionic liquids. Also, the stretching vibration region of the OH-group of methanol was studied in a ternary system carbon tetrachloride (inert solvent), methanol (proton donor) and N-alkyl substituted ionic liquid for the estimation of proton acceptor ability of ionic liquids. The hydrogen bond enthalpy of methanol in ionic liquids was calculated using data of measured solution enthalpies and data extracted from the literature. The frequency shifts of the OH-group of methanol induced by intermolecular interactions within ionic liquids in a carbon tetrachloride solution were compared with the hydrogen bonding enthalpies of methanol with ionic liquids. A linear relationship between the frequency shifts of the OH-groups and hydrogen binding enthalpies of methanol in ionic liquids were found. According to measured FTIR-spectroscopy data, the N-alkyl substituted ionic liquids analyzed in this work possess weak proton donor properties, and at the same time their proton acceptor ability (basicity) is much higher and shows dependency on anion structure