Analysis of guest binary mixtures by tert-butylcalix[6]arene using host memory of previously bound guests

A new principle of quantitative and qualitative analysis of binary organic mixtures is offered, which is based on an ability of calixarene receptor for specific polymorphic transitions related to the composition of the analyzed guest mixture. The ability of tert-butylcalix[6]arene to remember selectively some guests bound from headspace both of pure liquids and their binary mixtures is used. The image of guest mixture remains written in metastable polymorphs of host after partial or complete guest elimination from clathrates. The memory was read using differential scanning calorimetry as the enthalpy of exothermic polymorphic transition of host collapse. This enthalpy monotonously changes with the variation of guests' ratio in mixture, unlike the enthalpies of endothermic pseudopolymorphic transitions of guest release. So, the composition of volatile binary mixture can be estimated using only one receptor and only one its parameter even in absence of preferential binding from a binary mixture of guests. This is an example of a genuine molecular recognition. © 2013 The Royal Society of Chemistry

The influence of western countries’ sanctions on the development of the Russian exit tourism

© 2015, Asian Social Science. All rights reserved. The article is devoted to the influence of Western countries’ sanctions on the current state of the Russian tourist market. The tourist services market of the period before sanctions is compared with its modern condition. The reasons of the exit tourism crisis and their connection with sanctions against Russia are analyzed

Thermal analysis of charge-transfer complex formed by nitrogen dioxide and substituted calix[4]arene: Characterization of complexation reversibility

Simultaneous thermal analysis with evolved gas analysis (STA-EGA) was used to study the ability of 1,3-alternate conformer of tert-butylcalix[4]arene with four n-propoxy substituents (1) to be applied for detection of nitrogen dioxide in reversible sensors. Solid calixarene 1 forms an intensively colored charge-transfer complex (CTC) with gaseous NO2/N2O4. Using the STA-EGA method, the nature and conditions of CTC bleaching were characterized, including the conditions of its reversible change of color from white to dark blue and back at CTC formation and decomposition. For this, the thermal stability of CTC and its regeneration products were studied. This, together with the ion thermograms for evolved gases, gives the information on the oxidation of 1 by nitrogen dioxide if present. © Akadémiai Kiadó, Budapest, Hungary 2011

Configuration effect of the tert-butylthiacalix[4]arene tetracarboxy derivative on its receptor properties toward vaporous organic compounds

The effect of carboxy groups and the stable conformation of tert-butylcalix[4]arenes containing four carboxymethoxy substituents at the lower rim on their receptor properties toward organic substances and water was studied for the systems with guest vapor and solid host. For this purpose, the compositions of clathrates formed in these systems, their thermal stability, and parameters of the host-guest affinity were determined by the quartz microbalance method, thermogravimetry, thermogravimetry combined with differential scanning calorimetry and mass spectrometry, and static headspace gas chromatography. The introduction of four carboxymethoxy groups into tert-butylthiacalix[4]arene enhances its receptor capacity and affinity to water and aliphatic alcohols and decreases the thermal stability of the most part of the studied clathrates with hydrophobic guests except benzene. The studied tert-butylthiacalix[4]arene derivatives can be promising receptors for use in mass-sensitive sensors of the quartz microbalance type to methanol and ethanol vapors. © 2009 Springer Science+Business Media, Inc

Liquid silyl derivative of beta-cyclodextrin

© ISUCT Publishing. Per-6-O-(tert-butyl)(diphenyl)silyl-β-cyclodextrin was found to form metastable liquid phase, which is unusual for cyclodextrin mono-derivatives under ambient conditions. Also, it can exist in a solid amorphous state as a stable molecular glass. Conditions and parameters of phase transitions between crystal, glassy and liquid forms were determined. The studied compound is soluble in various solvents. Crystallization from its solutions and overcooled melt results in formation of two different polymorphs. The liquid mono-derivative of beta-cyclodextrin is amphiphilic and preferable for application in solutions, in pure form or even as a solvent for substrates with various structures

Nonregular structure-property relationships for inclusion parameters of tert-butylcalix[5]arene

The effect of macrocycle size on the structure-property relationships was studied for inclusion compounds of tert-butylcalix[n]arenes (n = 4,5) with volatile organic guests having various molecular size and group composition. Vapor-sorption isotherms, guest-inclusion stoichiometry and Gibbs energy, thermostability parameters and decomposition enthalpies were determined for host-guest compounds (clathrates) obtained using saturation of solid calixarene powder with guest vapor. The increase of the host macrocycle in the studied calixarene pair changes the observed structure-property relationship from the guest-binding selectivity mostly seen in inclusion Gibbs energy to the high sensitivity for guest structure in inclusion stoichiometry. The host with the larger macrocycle has more clathrates with stepwise formation and decomposition. Specific types of guest binding with solid hosts are discussed. © The Royal Society of Chemistry

Using clathrate pseudopolymorphism for a single sensor detection of target component in the headspace of liquid mixture

A new sensing mechanism for mass-sensitive sensors is offered, which is based not on the preferential binding as usual, but on the specific shape of sensor kinetic response. The used mechanism includes formation of an intermediate clathrate and then of a saturated clathrate between a substrate (guest) and a receptor (host), which breaks the sensor response into two separate steps. The corresponding host-guest pseudopolymorphism allows the discrimination of a target substrate in complex mixtures using a single gravimetric sensor. This mechanism does not require for a substrate to have multiple functional groups for a complementary host-guest binding. Moreover, qualitative and quantitative molecular recognition of hydrocarbon in the mixtures with its close homologues can be achieved. Such ability was performed in the present work for a thiacalix[4]arene derivative coating of a quartz-microbalance sensor, which is able to recognize benzene in the headspace of its liquid mixtures with toluene, xylenes, ethylbenzene, water, nitriles, alcohols and other compounds. The pseudopolymorphism of host-guest clathrate and low-temperature polymorphism of the host was confirmed by the determination of vapor sorption isotherms, thermoanalysis and X-ray powder diffraction analysis of the host-guest saturation products. © 2010 Elsevier B.V. All rights reserved

RESOURCES OF BIM TECHNOLOGIES AT THE STAGES OF JUSTIFICATION OF CONSTRUCTION AND DESIGN OF COMPLEX THE BUILDINGS FOR VARIOUS PURPOSES

Информационное моделирование зданий в настоящее время становится все более востребованным. Применение информационного моделирования позволяет на протяжении всего жизненного цикла объекта сокращать расходы на управление финансами, ресурсами, оборудованием и материалами. В данной статье рассмотрены возможности использования BIM-технологий при энергомоделировании.Building information modeling is now becoming more and more in demand. The use of information modeling allows you to reduce the cost of managing finances, resources, equipment and materials throughout the entire life cycle of an object. This article discusses the possibilities of using BIM-technologies for energy modeling

STUDY OF KINEMATIC PROPERTIES OF JET FLOWING FROM THE MIDDLE SIDE DUCT ORIFICE

In work the supply jet flowing out of the flat channel through a side orifice considered. Determined jet exit angle, as well as its kinematic properties. The velocity profiles plotted. The comparison of the results with the known data carried out.В работе рассмотрена приточная струя, выходящая из плоского канала через боковое отверстие. Определен угол выхода струи, а так же ее кинематические свойства. Построены профили скорости. Приведено сравнение полученных результатов с известными данными