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The ratio of low-frequency (LF, ~0.1 Hz) waves of RR interval duration (RRI) and systolic blood pressure (SAP) reflects the cardiac baroreflex sensitivity (BRS). Gravitational unloading (GU) may alter BRS during head-up tilt test (HUT) and lower body negative pressure (LBNP) test. Both effects cause blood redistribution to the lower body, but HUT is accompanied by greater unloading of sinocarotid baroreceptors than LBNP and activation of the vestibulosympathetic reflex. However, GU effects on BRS in these tests have not been directly compared previously. In this study we tested the hypothesis that the effect of dry immersion (DI, on-ground model of GU) on BRS in the same subjects will be more pronounced during HUT than during LBNP, while causing a comparable decrease in stroke volume (SV). Nine healthy men participated in two test sessions (before and after 7-day DI) consisting of five 3-min HUT (65°C) and five 3-min LBNP (–35 mmHg) with data averaging in each test. Wavelet analysis was used to determine the amplitude of the RRI and SAP waves in the 0.05–0.13 Hz range. The amplitude of LF waves of SAP increased in both tests, after DI—more significantly in HUT. The amplitude of LF RRI waves decreased in two tests; the percentage decrease did not differ between tests and did not change under the influence of DI. The α-coefficient (the ratio of RRI and SAP LF wave amplitudes) decreased equally in two tests before DI. After DI, more pronounced α-coefficient reduction was observed in HUT test but not in LBNP test. Thus, the effect of DI on BRS is evident in HUT, but not in LBNP, which may be explained by the more pronounced influence of HUT on the mechanisms of neural control of heart rhythm. [ABSTRACT FROM AUTHOR]

We studied the effects of long-term anti-orthostatic hypokinesia (head-down bed rest—BR, a model of gravitational unloading) on the dynamics of orthostasis-induced changes in the content of total (THb), deoxygenated (HHb), and oxygenated (OHb) hemoglobin in the calf at the level of the gastrocnemius muscle medial head using near-infrared spectroscopy. In seven young men, 2–4 days before and on the 19th day of BR, a passive head-up tilt test was performed (15 min in the supine position, then 15 min at 65°). After BR, there was an increase in heart rate and a decrease in stroke volume in the supine position, as well as more pronounced changes in these parameters during orthostasis. Blood pressure in the supine position and orthostasis did not change after BR. THb content increased gradually during orthostasis and reached a plateau by the end of the test; after BR, an increase in the half-rise time and a twofold increase in the plateau level were observed. Tissue HHb content by the end of the tilt test also increased after BR. The dynamics of OHb before BR was more complicated: this indicator grew, reached a maximum during a minute, and then gradually decreased to half of the maximum by the end of the test. After BR, the dynamics of OHb changed drastically: the signal increased gradually and reached a level that was twice the peak value of OHb content before BR. The results allow us to conclude that exposure to BR weakens the compensatory constriction of calf vessels during tilt test; consequently, it is followed by higher blood accumulation in calf vascular bed, which, in turn, leads to smaller SV during orthostasis. [ABSTRACT FROM AUTHOR]

Discrete analogs of pseudo-differential operators and equations in discrete Sobolev–Slobodetsky spaces are considered. Using suitable discrete boundary conditions, we prove the unique solvability of the discrete boundary-value problem. [ABSTRACT FROM AUTHOR]

Age-related changes in phase synchronization of spontaneous mean arterial pressure (MAP) and heart rate (HR) fluctuations within the baroreflex wave range (around 0.1 Hz) were studied in 66 subjects aged 20 to 52 years. During the head-up tilt test, MAP (photocompensation method), ECG (to calculate heart rate), and respiratory rate were continuously recorded. To quantify MAP–HR coupling, the phase synchronization index (PSI) was used. In people over 40 years, an increase in phase synchronization of MAP and HR was found in a supine position compared with subjects aged 20–24 years. At the same time, the increase in PSI of MAP and HR in response to orthostatic stress decreased after the age of 40, which may reflect a decrease in baroreflex activity with age. [ABSTRACT FROM AUTHOR]

Motivation: Application of chemical named entity recognition (CNER) algorithms allows retrieval of information from texts about chemical compound identifiers and creates associations with physical–chemical properties and biological activities. Scientific texts represent low-formalized sources of information. Most methods aimed at CNER are based on machine learning approaches, including conditional random fields and deep neural networks. In general, most machine learning approaches require either vector or sparse word representation of texts. Chemical named entities (CNEs) constitute only a small fraction of the whole text, and the datasets used for training are highly imbalanced. Methods and results: We propose a new method for extracting CNEs from texts based on the naïve Bayes classifier combined with specially developed filters. In contrast to the earlier developed CNER methods, our approach uses the representation of the data as a set of fragments of text (FoTs) with the subsequent preparati'on of a set of multi-n-grams (sequences from one to n symbols) for each FoT. Our approach may provide the recognition of novel CNEs. For CHEMDNER corpus, the values of the sensitivity (recall) was 0.95, precision was 0.74, specificity was 0.88, and balanced accuracy was 0.92 based on five-fold cross validation. We applied the developed algorithm to the extracted CNEs of potential Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease (Mpro) inhibitors. A set of CNEs corresponding to the chemical substances evaluated in the biochemical assays used for the discovery of Mpro inhibitors was retrieved. Manual analysis of the appropriate texts showed that CNEs of potential SARS-CoV-2 Mpro inhibitors were successfully identified by our method. Conclusion: The obtained results show that the proposed method can be used for filtering out words that are not related to CNEs; therefore, it can be successfully applied to the extraction of CNEs for the purposes of cheminformatics and medicinal chemistry. [ABSTRACT FROM AUTHOR]

Successive one-pot reactions of monolithiated N,N-diethylprop-2-yn-1-amine with 2-(ethenyloxy)-ethyl isothiocyanate and 2-(bromomethyl)-1,3-dioxolane afforded 5-[(1,3-dioxolan-2-ylmethyl)sulfanyl]-1[2-(ethenyloxy)ethyl]-N,N-diethyl-1H-pyrrol-2-amine in 91% yield. In the system t-BuOK–DMSO at room tem-perature (1 h), the product was converted to 1-[2-(ethenyloxy)ethyl]-N,N-diethyl-5-{[2-(2-hydroxyethoxy)-ethenyl]-sulfanyl}-1H-pyrrol-2-amine (yield 68%) instead of expected 1-vinyl derivative. [ABSTRACT FROM AUTHOR]

Changes in the baroreflex control of heart rate were studied in male subjects during their aerobic veloergometric exercises, using the phase synchronization index (PSI) of the mean arterial pressure (MAP) and heart rate (HR) oscillations in the frequency range of baroreflex waves (from 0.06 to 0.12 Hz). The protocol of tests included continuous recordings of blood pressure (by the photocompensation method) and ECG in volunteers (young men), with the load intensity specified individually for each subject in reference to his anaerobic threshold (AT). It has been shown in the test with a stepwise change in the load power, at a relatively moderate load (60% AT) PSI did not change compared with the value at rest, but significantly decreased when the load was increased up to 80% AT. To assess the time of the PSI, which can characterize the dynamics in the baroreflex resetting, changes caused by variations in the load we used the test with sinusoidally varying power (the mean value was 50% AT, the amplitude was 30% AT, and the power modulation period varied from 1000 to 100 s), MAP, HR and PSI values were calculated for successive 4-min intervals with 3-min overlapping. Whereas under this test, the PSI modulation, due to load power variations, almost disappeared as the period decreased from 1000 to 500 s, but the MAP and HR modulation was preserved until the 250-s period. Thus, the phase synchronization of MAP and HR oscillations at frequencies of baroreflex waves decreases during intensive aerobic exercise, and the pattern of its changes due to load variations are characterized by a relatively slow temporal dynamics. [ABSTRACT FROM AUTHOR]

The sequential reaction of lithiated methoxyallene, methyl isothiocyanate, and 2-(bromomethyl)-1,3-dioxolane in the presence of CuBr yields a 2,3-disubstituted thiophene instead of the expected pyrrole. The process is accomplished in one preparative stage and involves intramolecular cyclization of the in situ-generated lithium allenylimidothioate and N-alkylation of the resulting lithium thienylamide. Varying the reaction conditions does not affect its route: in all cases, the only product is N-(1,3-dioxolan-2-ylmethyl)-3-methoxy-N-methylthiophen-2-amine. [ABSTRACT FROM AUTHOR]

An unusual [2+2]-cyclodimerization of 5-ethenylidene-4,5-dihydro-1,3-thiazole, obtained from lithiated methoxyallene, isopropyl isothiocyanate, and propargylbromide, into highly functionalized 1,3-bis(methylene)cyclobutane is discovered. [ABSTRACT FROM AUTHOR]

Main intermediates in the electrocatalytic hydrogen evolution promoted by N-methyl-9-phenyl-acridinium iodide have been identified and characterized using cyclic voltammetry (CV) and NMR and ESR spectroscopy. A probable mechanism of the process has been proposed on the basis of DFT quantum chemical calculations. Analysis of structural and energetic parameters of intermediate products has shown that the electrocatalytic process involves formation of N-protonated radical cation, followed by reductive elimination of molecular hydrogen in the bimolecular reaction of two radical cations. [ABSTRACT FROM AUTHOR]

Immobilization of acridine and its derivatives (9-phenylacridine and N-methyl-9-phenylacridinium iodide) has been studied and quantitative data on physical adsorption have been obtained. The adsorption equilibrium constants K, the parameters A∞ and ΔGads have been calculated from the Langmuir adsorption isotherms. The electrochemical properties of organic compounds immobilized on a carbon material surface have been studied by means of cyclic voltammetry. [ABSTRACT FROM AUTHOR]

A convenient one-pot procedure has been proposed for the preparation of 1-(1-alkoxyethoxy)allenes from alkoxyethenes and prop-2-yn-1-ol with the use of trifluoroacetic acid as highly efficient catalyst for the synthesis of 3-(1-alkoxyethoxy)prop-1-ynes and of the system t-BuOK-DMSO for the isomerization of the latter into allenes. [ABSTRACT FROM AUTHOR]

Methyl and tert-butyl 2-{[5-(diethylamino)-1-methyl-1H-pyrrol-2-yl]sulfanyl|acetates have been synthesized in one preparative stage from accessible N,N-diethylprop-2-yn-1-amine, methyl isothiocyanate, and methyl 2-bromoacetate. [ABSTRACT FROM AUTHOR]

Derivatives of 2,3,6,7-tetrahydro-5H-[1,3]thiazolo[3,2-a]pyridine and 5,6-dihydropyridin-2(1H)-one were unexpectedly obtained at treating methyl 2-[(6-methyl-3-ethoxy-5,6-dihydropyridin-2-yl)sulfanyl]-acetate with a dilute solution of hydrochloric acid. Their formation resulted from the hydration of 5,6-dihydropyridine at the C=N bond accompanied with the elimination of a methyl 2-sulfanylacetate molecule and the addition of the methyl 2-sulfanylacetate to the second 5,6-dihydropyridine molecule at the C3=C4 bond followed by the elimination of a methanol molecule and the closure of a thiazole ring. [ABSTRACT FROM AUTHOR]

N-Alkylidene-1-(propargylsulfanyl)-2-(1 H-pyrrol-1-yl)buta-1,3-dien-1-amines at treatment by a superbasic system t-BuONa-THF-DMSO under standard conditions of the synthesis of seven-membered azaheterocycles are chemo- and stereoselectively converted into 4,4-disubstituted 5-ethenylidene-2-[( Z)-1-(1 H-pyrrol-1-yl)prop-1-enyl]-4,5-dihydro-1,3-thiazoles. [ABSTRACT FROM AUTHOR]

Aromatization of 2-methyl-6-(methylsulfanyl)-5-phenyl-2,3-dihydropyridine in DMSO in the presence of potassium tert-butoxide is accompanied by dimerization with formation of a mixture of 6-methyl-2-(methylsulfanyl)-3-phenylpyridine (major product), 2-methyl-6-(methylsulfanyl)-5-phenyl-2,3,4,5-tetrahydropyridine, and 2-methyl-4-[2-methyl-6-(methylsulfanyl)-5-phenyl-2,3-dihydropyridin-3-yl]-6-(methylsulfanyl)- 5-phenyl-2,3,4,5-tetrahydropyridine. [ABSTRACT FROM AUTHOR]

The results of investigations carried out in school students aged 11-16 years ( n = 930) have allowed us to determine some gender- and age-specific features in the neurodynamic and autonomic indicators of adolescents and identify the factors determining the formation of their psychophysiological state. The analysis of associations between the characteristics recorded in adolescents and a specific type of autonomic regulation has led to the conclusion about the predictive significance shown by the assessment of their functional constitution as an individual's adaptation and resource characteristics. [ABSTRACT FROM AUTHOR]

The electron impact mass spectra of 1-R-substituted 3-alkoxy-2-(propargylsulfanyl)- and 3-alkoxy-2-(allenylsulfanyl)-1 H-pyrroles (R = Me, i-Pr, s-Bu, Ph) have been studied for the first time. These compounds give rise to stable molecular ions whose primary fragmentation follows three competing pathways: cleavage of the C-O bonds with expulsion of alkyl radical, cleavage of the C-S bonds with formation of [ M-CH] ions, and cleavage of the C-N bonds with synchronous hydrogen transfer to give odd-electron [ M-CH]+ · ion. The main fragmentation pathway of 2-(propargylsulfanyl) derivatives is cleavage of the C-S bond with formation of [ M-CH] ion. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding the conversion of 6-(methylsulfanyl)-5-phenyl-2-[(vinyloxy)methyl)]-2,3-dihydropyridine 6- methyl-2-(methylsulfanyl)-3-phenylpyridine via the removal of vinyl alcohol and hydrogen.

By mass spectrometry methods applying electron ionization (70 eV) and laser desorption/ionization (NALDI, MALDI) 1-(alkyl-, cycloalkyl-, vinyloxyethyl-, and aryl)substituted 2-(alkyl- and propargylsulfanyl)-3-(ferrocenylmethoxy)pyrroles were studied and characterized. At the electron ionization the peak of the molecular ion possesses very low intensity. The main fraction ions are the ferrocenylmethyl ion (the most abundant peak) and its decomposition ions. Under the NALDI conditions molecular ions and protonated molecules [ M + H] are generated. The general fragmentation rules in the field-free region are determined. By an example of 1-phenyl derivative of pyrrole the MALDI procedure was also demonstrated to be suitable for investigation of 2-(alkylsulfanyl)-3-(ferrocenylmethoxy)pyrroles. [ABSTRACT FROM AUTHOR]

The activity of many physiological mechanisms depends on pH; therefore, maintaining a normal pH in the body is one of the important tasks of homeostatic regulation. Shifts in the acid–base balance can be associated with both pathological and physiological processes. Physiological acidosis in skeletal muscles appears due to physical exercise as muscle contractions may significantly reduce pH in muscle fibers and interstitium. However, after the cessation of contractions, the pH level rapidly normalizes, which is largely ensured by the work of the circulatory system, which removes metabolic products from the muscle. Acidosis causes vasodilatation by affecting the activities of numerous mechanisms in smooth muscle and endothelial cells and by inhibiting vasoconstrictor nerve influence. Vasodilation and increased muscle blood flow are favorable to recovery of the skeletal muscle performance following intense contractions. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) have been considered for many years as negative regulators in the cardiovascular system. Indeed, excessive production of ROS characterizes many cardiovascular diseases. The damaging effect of ROS can be especially pronounced in a newborn organism, since during this period their vasoconstrictor effect in pulmonary arteries remains as high as in pre-term fetus and the antioxidant systems have not yet formed. Therefore, in the first hours and days of independent life, pulmonary arteries tend to contract, primarily due to the low bioavailability of endothelial NO, which increases the risk of developing pulmonary hypertension in newborns. At the same time, during the perinatal period, ROS play an important role in the adaptive reactions of the circulatory system. ROS provide occlusion of the ductus arteriosus and separation of the pulmonary and systemic circulations soon after birth, and also contribute to the contraction of peripheral vessels during hypoxia, which often accompanies the delivery, and therefore provide priority blood supply to the brain in these conditions. The vasomotor effect of ROS is also pronounced in early postnatal ontogenesis, but it has a different character. In the first weeks of life, the action of ROS serves as one of the mechanisms for increasing endothelium-dependent relaxation of pulmonary vessels. In addition, during early postnatal ontogeny, ROS may play an important role in the regulation of systemic vascular tone. This review outlines the current understanding of the vasomotor role of ROS in the vessels of the pulmonary and systemic circulations and considers the mechanisms of ROS effects on the functioning of vascular endothelial and smooth muscle cells in the perinatal and early postnatal periods. [ABSTRACT FROM AUTHOR]

The article describes the aromatization of 2,3-dihydropyridines through hemiacetal elimination. The authors established that 5- (1-ethoxyethoxy)-2-methyl-6-(methylsulfanyl)-2,3-dihydropyridine 4, which was synthesized from allene 2, ethyl isothiocyanate, and methyl iodide, was quantitatively converted into 2-methyl-6-(methylsulfanyl) pyridine. The data of the elemental analysis, infrared and nuclear magnetic resonance spectra are noted.

The article discusses a study regarding the synthesis of pyrrolylpyridines from alkynes and isothiocyanates. Topics include the addition of a solution of butyllithium on the mixture under vigorous stirring, the reactivity and aromatization of 2,3-dihydropyridines, and the measurement of nuclear magnetic resonance spectra on a Bruker DPX-400 spectrometer.

The previously unavailable methyl 4-methoxy-3-methyl-5-(methylamino)thiophene-2-carboxylate was obtained by the one-pot procedure from a lithiated methoxyallene, methyl isothiocyanate, and methyl 2-bromoacetate. [ABSTRACT FROM AUTHOR]

1-Aza-1,3,4-trienes containing a methoxycarbonylmethyl substituent on the sulfur atom exhibit dual reactivity which can be controlled by the catalyst nature (CuBr or t-BuOK) so that to obtain methyl (pyrrol-2-yl)sulfanylacetates or methyl (methylamino)thiophene-2-carboxylates with high chemoselectivity. [ABSTRACT FROM AUTHOR]

Aromatization of 5-methoxy-6-(methylsulfanyl)-2-[(vinyloxy)methyl]-2,3-dihydropyridine by the action of potassium tert-butoxide in DMSO afforded a mixture of 2-(methylsulfanyl)-6-[(vinyloxy)methyl]- pyridine and 3-methoxy-6-methyl-2-(methylsulfanyl)pyridine at a ratio of 48: 52. [ABSTRACT FROM AUTHOR]

Benzylsulfanyl-substituted 2-aza-1,3,5-triene prepared according to one-pot procedure from methoxyallene, isopropyl isothiocyanate, and benzyl bromide underwent unexpected rearrangement in the superbasic t-BuOK-THF-DMSO system with formation of 2-[( Z)-1-methoxyprop-1-en-1-yl]-4,4-dimethyl-5-phenyl-4,5-dihydro-1,3-thiazole via α-deprotonation of the benzylsulfanyl substituent, followed by intramolecular [1,5]-cyclization. Concurrent deprotonation of methyl group in the ketone imine fragment and subsequent [1,7]-electrocyclization of the resulting azatriene carbanion afforded 2-(benzylsulfanyl)-3-methoxy-7-methyl-4,5-dihydro-3 H-azepine and 6-methoxy-2-methyl-3 H-azepine. [ABSTRACT FROM AUTHOR]

The results of studying solid solutions with the composition of BiNbZrO, BiYNbZrO ( y = 0-0.5; Δ y = 0.1), and BiYNbZrO ( y = 0.1-1; Δ y = 0.1) are presented. XRD and electron microscopy with X-ray microanalysis are used to determine the homogeneity regions of solid solutions; crystallochemical parameters are calculated. It is shown that irrespective of the ratio of Bi: Nb, two cubic phases are formed at an increase in the dopant amount. One of these represents a solid solution based on BiNbO (δ-phase) and the second one is a solid solution based on δ-BiO (δ′-phase). Conductivity of sintered samples is studied using the impedance spectroscopy technique. Introduction of yttrium into the bismuth sublattice results in no increase in conductivity of solid solutions, while in the case of the ratio of Bi: Nb = 3: 1, overall conductivity of solid solutions is somewhat higher at similar dopant concentrations. [ABSTRACT FROM AUTHOR]

It is well known that metabolic, cardiovascular, and respiratory indices during exercise of moderate intensity are linearly related to the power of the exercise. After the load reaches a definite level, this relationship becomes nonlinear. Different methods for evaluating the intensity of load at which this transition takes place are discussed. The methods for investigating the time course of the transitional process in the systems of energy supply for muscle contractions with the changing intensity of the contractions are described. The dependence of the dynamic characteristics of physiological indices on the fitness level, which, in turn, depends on the age and level of physical activity, is discussed. [ABSTRACT FROM AUTHOR]

For the case of 1-(allylsulfanyl)-2-methoxy- N-(1-methylethylidene)buta-1,3-dien-1-amine, obtained from α-lithiated methoxyallene, isopropyl isothiocyanate, and allyl bromide, it was shown that 5-ethylidene-2-(1-methoxyprop-2-enyl)-4,4-dimethyl-4,5-dihydro-1,3-thiazole and 6-methoxy-2-methyl-3H-azepine are formed competitively upon the action of the t-BuOK-THF-DMSO system. [ABSTRACT FROM AUTHOR]

Changes in daily mean and daily maximum surface ozone concentrations, temperature, and relative humidity are evaluated based on the data of long-term observations (from 11 to 16 years) carried out at eight German stations. For all stations the trends of daily mean surface ozone concentration are statistically significant and positive. The trend values are different and generally range from 0 to 10% per 10 years. The trends of the maximum daily concentration are, on average, approximately 1.5 times less. Noticeable part of trends of the surface ozone concentration is connected with the trends of meteorological variables: temperature, relative humidity, and air mass transport direction. After the account of the influence of the trends of meteorological variables, the trends of the surface ozone concentration at most stations substantially decrease. The highest trend values of daily mean and daily maximum surface ozone concentrations are observed in a cold season; in a warm season, the trend values are much lower, at some stations they are statistically insignificant. A conclusion is made that for a correct revealing of reasons of long-term changes in the surface ozone concentration one should take into account changes in meteorological factors influencing its formation. [ABSTRACT FROM AUTHOR]

The article discusses the unexpected transformations of 1-Aza-1,3,4-trienes in alcoholic potassium hydroxide. It mentions the reactions of isothiocyanates with carbanions derived from alkenes, allenes and acetylene. This become inexhaustible source of various aza diene and aza triene systems. Moreover, the reaction of shiff bases with alkali metal akoxides is noted in the article.

The article focuses on the study on the general procedure for the preparation of N-vinylpyrroles. It notes the importance of vinylation of NH-pyrroles as the general procedure for the preparation of N-vinylpyrroles. It mentions that the reaction being discovered of the mild cleavage of N-[2-(vinyloxy)ethyl] fragment effected by the system t-BuOK-DMSO not only essentially extends and intensifies the fundamental knowledge on the chemistry of vinyl ethers.

Using as example 3-methoxy-1-(2-methoxyethyl)-2-methylsulfanylpyrrole, obtained in one preparative stage from α-lithiated methoxyallene and 2-methoxyethyl isothiocyanate, a facile cleavage of a C–O bond in the N-(2-methoxyethyl) substituent by the t-BuOK–DMSO system has been discovered, opening access to a new class of N-vinylpyrroles (through β-elimination of methanol). [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which discusses the study on 4,5-dihydro-3H-azepines and aryl-substituted 3H-azepines prepared from isopropyl isothiocyanate and dilithiated propargylbenzene (I).

The first representative of thienyl-substituted 3H-azepines has been synthesized starting from dilithiated 2-methyl-5-propargylthiophene and isopropyl isothiocyanate. It was shown that N-(1-methylethylidene)-2-(5-methyl-2-thienyl)-1-(methylthio)-1,3-butadiene-1-amine (2-aza-1,3,5-triene) formed as a result of this reaction is readily converted into 2-methyl-6-(5-methyl-2-thienyl)-3H-azepine under the action of super bases. [ABSTRACT FROM AUTHOR]

The concentration, radiocarbon (14C) and stable isotope (13C and 18O) content of CO have been determined in air samples collected across Russia (about 8,500 km) and along the Ob river during the summer of 1999 to study the CO sources and sinks. An instrumented carriage on the Trans-Siberian railway and a boat on the river Ob were used as atmospheric measurement platforms. In general, CO mixing ratios, CO stable isotope ratios, as well as the abundances of 14CO over West Siberia were similar to those found at remote northern hemispheric baseline monitoring stations. Identified sources of CO along the Ob appear to be connected to methane oxidation based on an inferred δ13Csource = −36.8 ± 0.6‰, while the value for δ18Osource = 9.0 ± 1.6‰ identifies it as burning. Thus flaring in the oil and gas production can be supposed to be a source. The extreme 13C depletion and concomitant 18O enrichment for two of the boat samples unambiguously indicates contamination by CO from combustion of natural gas (inferred values δ13Csource = −40.3‰ and δ18Osource = 17.5‰). For these two samples, that have strongly elevated 14CO concentrations, the industrial area near Tomsk is identified as a source area using meteorological calculations. Along the Trans-Siberian Railroad background CO was to various degrees contaminated with CO from methane combustion (δ13Csource = −35.7 ± 6.2‰ and δ18Osource = 10.3 ± 1.8‰). The impact of industrial burning was discernable in the vicinity of Perm-Kungur. [ABSTRACT FROM AUTHOR]

The article examines the compound [2+2]-cyclodimerization of 1-aza-1,3,4-trienes, which is considered the first representative of 3,4-diisopropylidenecyclobutane-1,2-dicarbimidothioates. These compounds are unique and universal precursors of various carbo- and heterocyclic structures [1, 2]. 1-Aza-1,3,4-triene Ia was prepared as a mixture of E and Z isomers (9 : 1) [13] in almost quantitative yield by reaction of ?-lithiated 3-methylbuta-1,2-diene (II) and cyclopropyl isothiocyanate

Abstract: The first string of 70 in the IceCube neutrino observatory was deployed at the South Pole site in January 2005 and is now taking data. An IceCube string is composed of 60 digital optical modules (DOMs) each of which is an integrated package of a large area photomultiplier tube, high voltage unit, LED flasher calibration board, and embedded digital data acquisition system encased inside a glass pressure housing. The DOM posed a challenging design problem that had to simultaneously meet the extremes of high reliability in a remotely-deployed high pressure and low temperature environment, low power, wide dynamic range from single photon hits emitted by passing cosmic ray muons to tens of thousands of photons from immense electromagnetic showers, and fast time tagging of events to nanosecond precision. In addition the DOM had to be cost effective and reliably producible in quantities of several thousand units. The first year of real DOM production and testing was 2004: 400 DOMs were produced worldwide and tested in special dark freezer laboratories at temperatures ranging from to . Two hundred and eighty DOMs were sent to the South Pole for deployment and tested there again prior to deployment. Now frozen in the ice, the DOMs are showing exceptionally promising functionality. [Copyright &y& Elsevier]

Triads of isomeric N-alkyl- N-methyl-3-phenylthiophen-2-amines, N-methyl-3-alkyl-4-methylidene-3-phenylthietan-2-imines, and N-methyl-4-alkylsulfanyl-2-phenylcyclobut-2-en-1-imines (Alk = Me, Et, Bu) were synthesized from 1,3-dilithio-3-phenylpropyne, methyl isothiocyanate, and alkyl halides, and their fragmentation under electron impact was studied. Primary decomposition of the molecular ions of 2-aminothiophenes is determined by the localization of a radical cation center on the nitrogen atom, and it follows a path typical of alkyl(aryl)amines with elimination of hydrogen atom or methyl or propyl radical from the α-carbon atom in the N-alkyl substituent. Fragmentation of the iminothietanes involves cleavage of the four-membered ring in half to give neutral MeNCS molecule and 1-alkyl-1-phenylallene radical cation. Alkylsulfanyl(imino)-cyclobutenes undergo cleavage at the sulfur-containing side chain according to general relations holding in the fragmentation of alkyl sulfides. [ABSTRACT FROM AUTHOR]

Reactions of pyrrole, imidazole, pyrazole, and 1,2,4-triazole with allene and propyne in the gas phase with formation of the corresponding N-isopropenylazoles were simulated at the RHF/6-31G**, B3LYP/6-31G**, and MP2(full)/6-31G** levels. Dissociation of the N-H bond to give azolate ion is the main constituent of the reaction coordinate. All the examined azoles react preferentially with allene rather than with propyne; their reactivity decreases in the series pyrrole > imidazole > pyrazole > 1,2,4-triazole due to participation of the pyridine type nitrogen atoms in the prototropic propyne-allene rearrangement. [ABSTRACT FROM AUTHOR]

The reaction of 1,3-dilithio-3-phenylpropyne with methyl isothiocyanate in THF-hexane at -90 to -55°C, followed by successive treatment of intermediate product with a donor of protons, superbase, and alkyl halide, yields isomeric iminocyclobutenes and iminothietanes in addition to the expected aminothiophene. The ratio of the products depends on the amount and nature of proton donor (MeOH, t-BuOH), base (MeONa, t-BuOM, M = Li, Na, K; t-AmOK), co-solvent (DMSO, HMPA), and alkyl halide (MeI, EtI, BuBr). The system t-BuOH(MeOH)-t-BuOK-DMSO is the most favorable for the formation of the corresponding iminocyclobutene. [ABSTRACT FROM AUTHOR]

Fragmentation under electron impact of all N-isopropenylazoles, except for N-isopropenyl-2- phenylpyrrole, involves elimination of propyne or allene with formation of the corresponding NH azoles. N-Isopropenylpyrrole, N-isopropenyl-4,5,6,7-tetrahydroindole, and N-isopropenylindole give rise to rearrangement of the molecular ion into azepine structure, while the fragmentation of N-isopropenyl-2-phenylpyrrole is accompanied by transfromation into 5-methyl-5,6-dihydropyrrolo[2,1-a]isoquinoline. Retrodiene decom- position is the main fragmentation pathway of the molecular ions derived from N-isopropenyl-4,5,6,7-tetrahydroindole and its 2-methyl-substituted analog. In the decomposition of 2,3-di- and 2,3,5-trimethyl-N-isopropenylpyrrole, the major fragment ions are formed from the [M - H]+ ion having a pyridinium structure rather than from the molecular ion. N-Isopropenyldi- and -triazoles undergo fragmentation along competing pathways involving cleavage of the heteroring. [ABSTRACT FROM AUTHOR]

Abstract Aim: We studied transmitter characteristics of proximal and distal arteries supplying skin (saphenous artery and its medial tarsal branch), kidneys (terminal branches of renal artery and interlobar arteries) and skeletal muscle (proximal and distal sections of external sural artery). Methods: Artery segments were mounted in an isometric myograph and intramural nerves were activated by electrical field stimulation. Adrenergic and purinergic components of the neurogenic response were blocked using phenoxybenzamine and α,β-methylene adenosine triphosphate (mATP), respectively. Results: Arteries from skin or kidney developed rapid and prominent neurogenic contractile responses, with half-maximal amplitude reached within 5–15 s; responses in proximal vessels were greater than in distal vessels. Arteries from skeletal muscle responded to sympathetic stimulation with a moderate contraction developing over 1 min or more, the response of distal segments was greater than that of proximal segments. In skeletal muscle vessels the sympathetically evoked contraction was completely blocked by phenoxybenzamine, whereas in skin and renal vessels it was the combined effect of noradrenaline and adenosine triphosphate (ATP). Given alone, mATP did not change the magnitude of the response to nerve stimulation, but increased its latency and also potentiated the response to exogenous noradrenaline. In all vascular beds, distal vessels were more sensitive to noradrenaline and mATP. Conclusion: It thus appears that the noradrenaline/ATP ratio of the sympathetic vasoconstrictor response differs between vascular beds in a way that is consistent with known differences in the selective regulation of regional vascular resistance by the sympathetic nervous system. [ABSTRACT FROM AUTHOR]