Feasibility Exploration of Laser‐based Techniques for Characterization of a Flashing Jet

Two‐phase flows hold an interest in many areas of science and engineering. In the safety field, one such topic is the accidental release of flammable and toxic pressure‐liquefied gases. In case of such a release, a flashing vapor explosion takes place resulting in a very dense two‐phase cloud. If the released substance is flammable, this cloud can be combustible and can lead to deflagration or detonation. For understanding the source processes of flashing and risk assessment, data related to cloud characteristics (i.e. droplet size, velocity etc.) is needed especially in the near region of the release. Due to the non‐equilibrium nature of the near field regions accurate data measurement is not possible with intrusive techniques. Therefore, laser‐based optical techniques (like Particle Image Velocimetry (PIV), Particle Tracking Velocimetry and Sizing (PTVS), Phase Doppler Anemometry (PDA) etc.) present the only possibility to obtain information for particle diameter and velocity evolution in this harsh environment.     

Synthesis,spectral properties,and antimicrobial activity of 2-arilamino-2,4,4,6,6-pentachloro-1,3,5,2λ<Superscript>5</Superscript>,4λ<Superscript>5</Superscript>,6λ<Superscript>5</Superscript>-triazatriphosphines and poly[bis(4-fluorophenylamino)phosphazene]

2-(4-Chloro and 4-fluorophenylamino)-2,4,4,6,6-pentachloro-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphinines and poly[bis(4-fluorophenylamino)phosphazene] were synthesized by reactions of 4-fluoroaniline and 4-chloroaniline with 2,2,4,4,6,6-hexachloro-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphinin and poly(dichlorophosphazene), respectively, in tetrahydrofuran under argon at ?20°C, followed by heating under reflux. The products were isolated by column chromatography and were characterized by FTIR, NMR (¹H, ¹³C, ³¹P), and mass spectra, termogravimetry, and high-performance liquid chromatography. Antimicrobial activity of the monomeric compounds and polymer against 9 bacteria and 5 yeast cultures was evaluated by the disk diffusion method in dimethyl sulfoxide relative to a number of commercial antibiotics and antifungal agents. Aminophosphazene derivatives exhibited a broad spectrum of activity against both Gram-positive and Gram-negative bacterial with a magnitude comparable to reference antimicrobial agents. The polymeric product turned out to be more potent than the monomeric compounds.     

High-performance liquid chromatographic method for the determination of a novel leukotriene D4 antagonist (MK-0571) in biological specimens

A rapid, sensitive and selective liquid chromatographic procedure was developed to quantitate the levels of a novel leukotriene D4 antagonist, MK-0571 (I), in biological samples. The method involves the addition of an internal standard, an analogue of I, and methanol to the biological matrix. Following centrifugation the supernatant is chromatographed isocratically on a C18 reversed-phase column and the acids are detected with an ultraviolet detector. The sensitivity of the method is such that 50 ng of drug can be quantitated per aliquot of sample. Assays were linear over a 0.06-40.0 micrograms range and exhibited a recovery of 100.5 +/- 7.0% (mean +/- S.D.) over this range. This procedure was utilized to monitor plasma, liver and urinary levels of I in chronic and acute toxicity studies in several animal species.     

Synthesis and Liquid Crystalline Behavior of Random Copolymer of Poly(ethylene oxide) Macromonomer and Liquid Crystalline Monomer by the Photon Transmission Technique

Random copolymers of poly(ethylene oxide) macromonomer with p‐vinylbenzyl end‐functional group (PEOVB) and liquid crystalline monomer, namely 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate (COA), were prepared by conventional free radical polymerization. A living anionic polymerization technique was employed for the synthesis of PEO macromonomers bearing p‐vinylbenzyl moiety at one end. The photon transmission method was also applied to study the phase transitions of COA monomer and its random copolymer with PEO. It was found that, for both samples, the nematic‐smectic A transition is continuous, but the critical fluctuation regions do not allow to obtain 3D XY values. Instead, we have obtained the values close to mean field regime. Scaling of thermal hystersis for random copolymer sample near the nematic‐isotropic transition was studied as well. Thermal hysteresis loops were produced under linearly varying temperature. It was shown that the areas of the hysteresis loops scale with the temperature scanning rate with an exponent being equal to 0.614 which is in good agreement with the field‐theoretical value.     

Evaluation of the (Allyl alcohol 1,2‐butoxylate‐block‐etoxylate)‐b‐PMMA Copolymers Composition by the Dielectric Measurements

Redox initiated free‐radical polymerization of methyl methacrylate (MMA) with allyl alcohol 1,2‐butoxylate‐block‐etoxylate (AABE) was carried out to yield AABE‐b‐PMMA copolymers at elevated temperatures. The composition of the copolymers depending on the polymerization temperature was qualitatively estimated by the dielectric measurements. It has been seen that AABE segment quantity decreased and PMMA segment quantity increased with increasing the polymerization temperature. The dielectric constant and the dissipation factor of the copolymers were investigated as a function of frequency and temperature. The dielectric constant and the dissipation factor were found to be strongly affected by the polymerization temperature. The highest dielectric constant in all studied temperatures and frequencies was obtained in the case of the copolymer which was prepared at 313 K. The dipolar C‐O and OH groups of the AABE segment have the primary effect on the dielectric constant. The copolymer which was prepared at 323 K, showed the highest dissipation factor near the relaxation temperature of PMMA.     

由蒽醌衍生的二价和三价过渡金属偶氮配合物及其致突变－畸变作用

制备了4-(5′-氨基萘-3′-磺酸)偶氮-(2″-N-(4苁,6苁-二氯-S-三嗪)苯-5″-(β-羟乙基砜硫酸酯)-2-甲基蒽醌(2a),4-(2′-氨基苯磺酸)偶氮-(2″-N-(4苁,6苁-二氯-S-三嗪)-3″-苯磺酸)-2-甲基蒽醌,4-(5′-氨基萘-3′-磺酸)偶氮-(2″-N-(4苁,6苁-二氯-S-三嗪)苯-5″-(β-羟乙基砜硫酸酯)-2-甲基蒽醌和4-(p-(β-羟乙基砜硫酸酯)偶氮-(2″-N-(4苁,6苁-二氯-S-三嗪)萘-5″-磺酸)-2-甲基蒽醌的FeIII,CoII金属配合物,并在安姆/沙门氏菌/微粒体致突变试验(Ames/Salmonella/Microsome Test)和大鼠胚胎中测定其致突变-畸变作用。不管是否使用代谢赋活剂S9mix,2a-Fe和2a-Co对TA98 and TA100菌株均无致突变-畸变作用。     

Substituent effects on the ring‐opening mechanism of gem‐dibromospiropentanes to related allenes: a theoretical study

Density functional theory computations at B3LYP and X3LYP levels were performed for ring openings of substituted gem‐dibromospiropentanes (R = ―H, ―Cl, ―Br, ―CH₃, ―SiH₃, ―OH, ―OCH₃, ―CF₃, ―BF₂, and ―SH) to related allenes. The conversion of spiropentanoids 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j to the corresponding allenes 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j can proceed in both concerted and stepwise mechanism except for R = ―H. Both ring‐opening mechanisms have similar activation energy barriers to open the spiropentanylidene ring and generate the structure of allene at all theoretical levels used herein. Generally the π electron‐donating group (―OH or ―SH) decreases the activation barrier for the follow‐up reaction of 1‐bromo‐1‐lithiospiropentanoid and free spiropentanylidene. Hence, both bearing electron‐donating substituents are more reactive than those with electron‐withdrawing group, and the first one to open the ring to the LiBr–allene complex does so more readily than the second. The sEDA index used to measure sigma‐electron excess/deficiency of the cyclopropylidene ring is mutually correlated for the studied systems. Copyright © 2015 John Wiley & Sons, Ltd.     

A self-tuning heuristic for the design of communication networks

This paper addresses the design of communication networks that has a large application area. The problem is to design a minimum cost network subject to a given reliability level. Complexity of the problem is twofold: (1) finding a minimum-cost network topology that every pair of nodes can communicate with each other and (2) computing overall reliability to provide the reliability constraint. Over the last two decades, metaheuristic algorithms have been widely applied to solve this problem due to its NP-hardness. In this study, a self-tuning heuristic (STH), which is a new approach free from parameter tuning, is applied to the design of communication networks. Extensive computational results confirm that STH generates superior solutions to the problem in comparison to some well-known local search metaheuristics, and also more sophisticated metaheuristics proposed in the literature. The practical advantage of STH lies in both its effectiveness and simplicity in application to the design problem.     

Equilibrium Formation of Stable All‐Silicon Versions of 1,3‐Cyclobutanediyl

Main group analogues of cyclobutane‐1,3‐diyls are fascinating due to their unique reactivity and electronic properties. So far only heteronuclear examples have been isolated. Here we report the isolation and characterization of all‐silicon 1,3‐cyclobutanediyls as stable closed‐shell singlet species from the reversible reactions of cyclotrisilene c‐Si₃Tip₄ (Tip=2,4,6‐triisopropylphenyl) with the N‐heterocyclic silylenes c‐[(CR₂CH₂)(NtBu)₂]Si: (R=H or methyl) with saturated backbones. At elevated temperatures, tetrasilacyclobutenes are obtained from these equilibrium mixtures. The corresponding reaction with the unsaturated N‐heterocyclic silylene c‐(CH)₂(NtBu)₂Si: proceeds directly to the corresponding tetrasilacyclobutene without detection of the assumed 1,3‐cyclobutanediyl intermediate.