NEW SPECTROPHOTOMETRIC METHOD FOR DETERMINING TITANIUM(IV) IN NATURAL OBJECTS

The article considers the interaction of Ti(IV) with 2, 3, 4-trihydroxy-3'-fluoroazobenzene (H3R) in the presence and absence of phenontroline (Phen), α, α'-dipyridine (α, α'-dip), and batophenontroline (B-phen) studied by using a spectrophotometric method. It has been found that the yield of the binary complex is maximum at pHopt = 5 (λmax = 428 nm), and for mixed-ligand complexes, pHopt = 3.0; 4.0; 3.5; λmax = 477 nm, 443 nm, 440 nm Ti(OH)2(H2R)-Phen, Ti (OH)2(H2R)-α, α'-dip and Ti(OH)2(H2R)-B-phen, respectively. It has been investigated that a twofold excess of the reagent is required for complete binding of titanium(IV) into the complex. The influence of time and temperature on the complexation is investigated. The stability constants of binary and mixed-ligand titanium(IV) complexes were calculated: logβ = 8.61 ± 0.05 for Ti(OH)2(H2R)2, logβ = 10.98 ± 0.06 for Ti(OH)2(H2R)-Phen, logβ = 10.85 ± 0.04 for Ti (OH)2(H2R)-α, α'-dip, logβ = 11.26 ± 0.03 for Ti(OH)2(H2R)-B-phen. The ratio of the reacting components in the binary complex is 1 : 2, and in the mixed ligands 1 : 2 : 2. The influence of foreign ions and masking substances on the titanium(IV) complexation with reagents has been studied. The determination is practically not interfered by alkaline, alkaline-earth and some transition elements. Due to these characteristics, the complexes can be used for defining titanium(IV) in different objects.

Assessment of influence of surface crack-like stress concentrators on main pipeline operability

Устранение поверхностных трещиноподобных дефектов типа «риска» на участках подводных переходов магистральных трубопроводов возможно методом вышлифовки на глубину до 20 % толщины трубы. Ранее было подтверждено, что в подводных условиях все основные методы неразрушающего контроля позволяют стабильно выявлять имеющиеся в зоне вышлифовки произвольно ориентированные поверхностные дефекты протяженностью от 20 мм и глубиной от 1,5 мм. Однако при меньших геометрических параметрах дефектов имеется вероятность их неполного устранения либо необнаружения. Для оценки возможности эксплуатации трубопровода с поверхностным дефектом с учетом принятых режимов диагностики проведены циклические испытания по критериям механики разрушений полноразмерных образцов с нанесенными в зоне вышлифовки поверхностными трещиноподобными концентраторами напряжений указанных размеров. Все группы образцов показали более чем двукратное превышение длительности инкубационного периода развития трещины по сравнению с количеством циклов нагружения, которое может испытать трубопровод за средний межинспекционный период эксплуатации. По результатам испытаний подтверждена возможность проведения ремонта поверхностных трещиноподобных дефектов типа «риска» на подводных переходах магистральных трубопроводов с различным сроком эксплуатации методом вышлифовки без установки кессона на ремонтируемый участок. Elimination of surface crack-like defects of the “risk” type on underwater crossing sections of trunk pipelines is possible by grinding to a depth of up to 20 % of pipe thickness. Previously, it was confirmed that in underwater conditions, all main non-destructive testing methods make it possible to stably identify randomly oriented surface defects in the grinding zone with a length of 20 mm and a depth of 1.5 mm. However, with smaller geometric parameters of defects, there is a possibility of their incomplete elimination or non-detection. To assess the possibility of operating a pipeline with surface defect, taking into account the accepted diagnostic modes, cyclic tests were carried out according to the fracture mechanics criteria of full-size specimens with surface crack-like stress concentrators of the indicated sizes applied in the grinding zone. All groups of samples showed more than a twofold excess of the duration of crack development incubation period in comparison with the number of loading cycles that the pipeline can experience during the average inter-inspection period of operation. Based on the test results, the possibility of repairing surface crack-like defects of the “risk” type at trunk pipeline underwater crossings with different service life by grinding without installing a caisson on the repaired section was confirmed.

N-Aroylbenzotriazoles as Efficient Reagents for o-Aroylation in Absence of Organic Solvent

N-Aroylbenzotriazoles have been shown to be efficient reagents for esterification in the absence of organic solvent. Grinding of N-aroylbenzoytiazoles with twofold excess of alcohols for a couple of hours at room temperature gave corresponding esters in high percentage of yields.

Efficient Biginelli Synthesis of 2-Aminodihydropyrimidines under Microwave Irradiation

A practical and general method for the Biginelli cyclocondensation of guanidine with aldehydes and β-dicarbonyl compounds is described and illustrated with the synthesis of a set of 26 functionalized 2-amino-3,4-dihydropyrimidines. The simple protocol involves the ­microwave-mediated reaction of a twofold excess of guanidine hydrochloride with the required reaction partners in an alcohol at 120 °C. Yields are generally good, with short reaction times and a simple workup. The scope is considerably wider than that of similar reactions ­carried out under conventional heating.

Trioxorhenium(VII) Complexes with Imidazolin-2-iminato Ligands

The Staudinger reaction of the N-heterocyclic carbenes 1,3-di-tert-butylimidazolin-2-ylidene (1a), 1,3-dimesitylimidazolin-2-ylidene (1b) and 1,3-diisopropyl-4,5-dimethylimidazolin-2- ylidene (1c) with trimethylsilyl azide in boiling toluene furnishes the corresponding 2- (trimethylsilylimino)imidazolines 2a - c. Treatment of Re2O7 with a twofold excess of these N-silylated imines results in the formation of the imidazolin-2-iminato trioxorhenium(VII) complexes 3a - c and hexamethyldisiloxane, Me3SiOSiMe3. The molecular structures of 2a, 3a and 3b are reported. In addition, the X-ray crystal structure determination of complex 3c · H2O is presented, which has formed by hydrolysis and cleavage of the metal-nitrogen bond in 3c. 3c · H2O consists of 2-aminoimidazolium cations and tetraoxorhenate(VII) anions, which are linked by N-H-O hydrogen bonds.

Roles of Mycobacterium smegmatisd-Alanine:d-Alanine Ligase and d-Alanine Racemase in the Mechanisms of Action of and Resistance to the Peptidoglycan Inhibitor d-Cycloserine

ABSTRACT d-Cycloserine (DCS) targets the peptidoglycan biosynthetic enzymes d-alanine racemase (Alr) and d-alanine:d-alanine ligase (Ddl). Previously, we demonstrated that the overproduction of Alr in Mycobacterium smegmatis determines a DCS resistance phenotype. In this study, we investigated the roles of both Alr and Ddl in the mechanisms of action of and resistance to DCS in M. smegmatis. We found that the overexpression of either the M. smegmatis or the Mycobacterium tuberculosis ddl gene in M. smegmatis confers resistance to DCS, but at lower levels than the overexpression of the alr gene. Furthermore, a strain overexpressing both the alr and ddl genes displayed an eightfold-higher level of resistance. To test the hypothesis that inhibition of Alr by DCS decreases the intracellular pool of d-alanine, we determined the alanine pools in M. smegmatis wild-type and recombinant strains with or without DCS treatment. Alr-overproducing strain GPM14 cells not exposed to DCS displayed almost equimolar amounts of l- and d-alanine in the steady state. The wild-type strain and Ddl-overproducing strains contained a twofold excess of l- over d-alanine. In all strains, DCS treatment led to a significant accumulation of l-alanine and a concomitant decease of d-alanine, with approximately a 20-fold excess of l-alanine in the Ddl-overproducing strains. These data suggest that Ddl is not significantly inhibited by DCS at concentrations that inhibit Alr. This study is of significance for the identification of the lethal target(s) of DCS and the development of novel drugs targeting the d-alanine branch of mycobacterial peptidoglycan biosynthesis.

Metallkomplexe mit funktionalisierten Schwefelliganden, XV [1]. Reaktionen von Platin(0)-Komplexen mit 1,2,4-Trithiolanen, 1,2,4,5-Tetrathianen, 1,2,3,5,6-Pentathiepanen sowie Thioketonen. Kristallstrukturanalyse von (Ph3P)2Pt(η2-Ph2C=S) / Metal Complexes of Functionalized Sulfur Containing Ligands, XV [1]. Reactions of Platinum(O) Complexes with 1,2,4-Trithiolanes, 1,2,4,5-Tetrathianes, 1,2,3,5,6-Pentathiepanes as well as Thioketones. X-Ray Structure Analysis of (Ph3P)2Pt(η2-Ph2C=S)

3,3,5,5-Tetraphenyl-1,2,4-trithiolane (1) reacts with twofold excess of (Ph3P)2Pt(η2-C2H4) (4) to give a 1:1 mixture of the complexes (Ph3P)2 (6a) and (Ph3P)2Pt(η2-Ph2C=S) (7a). Treatment of 3,3,6,6-tetraphenyl-1,2,4,5-tetrathiane (2) with a fourfold excess of 4 yields [Pt2(PPh3)4(μ-S)2] (8) and the platinum(O) compound 7a. The reaction of the 1,2,3,5,6- pentathiepane 3 with a fourfold excess of 4 affords a 1:1:1 mixture of 8, the platinum(O) complex 7b and the bis-thiolato platinum(II) complex 6b. The thioketone complexes 7a-c were formed in smooth reactions of 4 with the thioketones 5a-c. The molecular structure of (Ph3P)2Pt(η2-Ph2C=S) (7a) has been established by single-crystal X-ray analysis.

Positive Life Change and Recovery from Depression and Anxiety

BackgroundThe objective was to examine the relationship between positive life change (PLC) and recovery from depression and anxiety. Following Brown et al (1988, 1992), we hypothesised: (a) that an excess of PLC would be found in the 3-month period before recovery compared with base rates (‘excess hypothesis’) and (b) that fresh-start and anchoring subtypes of PLC would trigger recovery from depression and anxiety respectively (‘specificity hypothesis’).MethodOne hundred and seventy primary care patients with a depressive and/or anxiety disorder, selected from 1994 consecutive attenders, were assessed at baseline and at 1-year and 3.5-year follow-ups on life change (LEDS) and psychopathology (PSE and Course Interview).ResultsOur results appeared to confirm the excess hypothesis regarding depression and anxiety (twofold excess was found prior to recovery), but not regarding mixed anxiety/depression. They did not support the specificity hypothesis.ConclusionsPLC facilitates recovery but is neither a necessary nor sufficient condition for remission. Difficulty reduction is the most important recovery-enhancing factor.