Kinetic Behavior of Quaternary Ammonium Hydroxides in Mixed Methane and Carbon Dioxide Hydrates

This study evaluates the kinetic hydrate inhibition (KHI) performance of four quaternary ammonium hydroxides (QAH) on mixed CH₄ + CO₂ hydrate systems. The studied QAHs are; tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide (TBAOH), tetramethylammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPrAOH). The test was performed in a high-pressure hydrate reactor at temperatures of 274.0 K and 277.0 K, and a concentration of 1 wt.% using the isochoric cooling method. The kinetics results suggest that all the QAHs potentially delayed mixed CH₄ + CO₂ hydrates formation due to their steric hindrance abilities. The presence of QAHs reduced hydrate formation risk than the conventional hydrate inhibitor, PVP, at higher subcooling conditions. The findings indicate that increasing QAHs alkyl chain lengths increase their kinetic hydrate inhibition efficacies due to better surface adsorption abilities. QAHs with longer chain lengths have lesser amounts of solute particles to prevent hydrate formation. The outcomes of this study contribute significantly to current efforts to control gas hydrate formation in offshore petroleum pipelines.     

Phytochemical Profiling of Lavandula coronopifolia Poir. Aerial Parts Extract and Its Larvicidal,Antibacterial, and Antibiofilm Activity Against Pseudomonas aeruginosa

Infections associated with the emergence of multidrug resistance and mosquito-borne diseases have resulted in serious crises associated with high mortality and left behind a huge socioeconomic burden. The chemical investigation of Lavandula coronopifolia aerial parts extract using HPLC–MS/MS led to the tentative identification of 46 compounds belonging to phenolic acids, flavonoids and their glycosides, and biflavonoids. The extract displayed larvicidal activity against Culex pipiens larvae (LC₅₀ = 29.08 µg/mL at 72 h). It significantly inhibited cytochrome P-450 monooxygenase (CYP450), acetylcholinesterase (AChE), and carboxylesterase (CarE) enzymes with the comparable pattern to the control group, which could explain the mode of larvae toxification. The extract also inhibited the biofilm formation of Pseudomonas aeruginosa by 17–38% at different Minimum Inhibitory Concentrations (MICs) (0.5–0.125 mg/mL) while the activity was doubled when combined with ciprofloxacin (ratio = 1:1 v:v). In conclusion, the wild plant, L. coronopifolia, can be considered a promising natural source against resistant bacteria and infectious carriers.     

Production of Alkyl Aryl Sulfides from Aromatic Disulfides and Alkyl Carboxylates via a Disilathiane–Disulfide Interchange Reaction

The results of this study show that disilathiane is an effective mediator in the synthesis of alkyl aryl sulfides with disulfides and alkyl carboxylates. Mechanistic studies suggest that disilathiane promotes cleavage of the sulfur–sulfur bond of disulfides to generate thiosilane as a key intermediate. Diselenides were also applicable to this transformation to produce the corresponding selenides.     

Driving Organic Nanocrystals Dissolution Through Electrochemistry

We have recently discussed how organic nanocrystal dissolution appears in different morphologies and the role of the solution pH in the crystal detriment process. We also highlighted the role of the local molecular chemistry in porphyrin nanocrystals having comparable structures: in water-based acid solutions, protonation of free-base porphyrin molecules is the driving force for crystal dissolution, whereas metal (Zn^II) porphyrin nanocrystals remain unperturbed. However, all porphyrin types, having an electron rich π-structure, can be electrochemically oxidized. In this scenario, a key question is: does electrochemistry represent a viable strategy to drive the dissolution of both free-base and metal porphyrin nanocrystals? In this work, by exploiting electrochemical atomic force microscopy (EC-AFM), we monitor in situ and in real time the dissolution of both free-base and metal porphyrin nanocrystals, as soon as molecules reach the oxidation potential, showing different regimes according to the applied EC potential.     

Redox-Mediated Alcohol Oxidation Coupled to Hydrogen Gas Formation in a Dye-Sensitized Photosynthesis Cell

This work reports a dye-sensitized photoelectrochemical cell (DSPEC) that couples redox-mediated light-driven oxidative organic transformations to reductive hydrogen (H₂) formation. The DSPEC photoanode consists of a mesoporous anatase TiO₂ film on FTO (fluorine-doped tin oxide), sensitized with the thienopyrroledione-based dye AP11 , while H₂ was formed at a FTO-Pt cathode. Irradiation of the dye-sensitized photoanode transforms 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) to the oxidized TEMPO (TEMPO⁺), which acts as a chemical oxidant for the conversion of benzyl alcohol. The TEMPO^0/+ couple, previously used as redox mediator in DSSC, mediates efficient electron transfer from the organic substrate to the photo-oxidized dye. A DSPEC photoreactor was designed that allows in situ monitoring the reaction progress by infrared spectroscopy and gas chromatography. Sustained light-driven oxidation of benzyl alcohol to benzaldehyde within the DSPEC photoreactor, using of TEMPO as mediator, demonstrated the efficiency of the device, with a photocurrent of 0.4 mA cm⁻², approaching quantitative Faradaic efficiency and exhibiting excellent device stability.     

Turbulent flow past a transverse cavity with inclined side walls. 1. Flow structure

The process of vortex formation in a cavity with inclined walls, which has a moderate aspect ratio, is experimentally studied, and the distribution of pressure coefficients is measured. The angle of inclination of the side walls ϕ is varied from 30 to 90°. It is found that the flow in the cavity becomes unstable in the range of inclination angles ϕ = 60–70°. Flow reconstruction occurs, which substantially alters the surface-temperature and static-pressure distributions. Large changes in these characteristics and their nonuniform distributions for these angles are observed across the cavity on its frontal wall and on the bottom. For small angles (ϕ = 30 and 45°), the pressure on the rear wall drastically increases, which leads to a small increase in pressure averaged over the entire cavity surface. __________ Translated from PrikladnayaMekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 68–76, September–October, 2006.     

Direct numerical simulations of two-layer viscosity-stratified flow

Two-dimensional simulations of flow instability at the interface of a two-layer, density-matched, viscosity-stratified Poiseuille flow are performed using a front-tracking/finite difference method. We present results for the small-amplitude (linear) growth rate of the instability at small to medium Reynolds number for varying thickness ratio n, viscosity ratio m, and wavenumber. We also present results for large-amplitude non-linear evolution of the interface for varying viscosity ratio and interfacial tension. For the linear case, the interfacial mode is neutrally stable for as predicted by analysis. The growth rate is proportional to Reynolds number for small Re, and increases with viscosity ratio. The growth rate also increases when the thickness of the more viscous layer is reduced. Strong non-linear behavior is observed for relatively large initial perturbation amplitude. The higher viscosity fluid is drawn out as a finger that penetrates into the lower viscosity layer. The simulated interface shape compares well with previously reported experiments. Increasing interfacial tension retards the growth rate of the interface as expected, whereas increasing the viscosity ratio enhances it. Drop formation at the small Reynolds number considered in this study is precluded by the two-dimensional nature of the calculations.     

Order and Pattern Formation in Psychotherapy

In an empirical analysis of the dynamics of psychotherapy processes, concepts and tools from self-organization theory are applied. Our focus is on pattern formation in the therapy system, i.e. the system constituted by the interaction dynamics of therapist and patient. The hypothesis of pattern formation explored is based on data sets of 28 psychotherapy courses (10 behavioral, 3 client-centered, 9 heuristic, 6 schema-oriented; 40 to 90 weekly sessions). Patients' and therapists' therapy session records are analyzed (33 variables addressing various aspects of the therapeutic relationship, of progress within and outside the therapy setting). Multivariate methods are implemented to test the key hypothesis of self-organization theory, namely the reduction of degrees of freedom of a system. Consistent with this hypothesis, a significant reduction of degrees of freedom is found when the initial and final sessions of the therapies are compared. Correspondingly, Landsberg order increased significantly in the course of therapies. Given these findings, the explorative question of how this self-organizing property relates to therapy outcome is investigated. We find a significant positive association with various outcome measures, such as: therapist's and client's evaluations of success (direct change measures), feelings of guilt, anxiety, social potence, depression (pre-post effect sizes), and others. These results suggest that order is related to therapy outcome. In our interpretation, order is a dynamical attribute of the therapeutic alliance to be considered as a promising therapy process variable.     

四川泸定县泥石流灾害成因、特征与防治建议

泸定县地处川西高原与四川盆地的过渡地带,地质环境条件复杂,分布泥石流沟127条,发育密度054条·10km-2。在遥感解译和地面调查基础上,论述了泸定县泥石流灾害成因、发生特征、危害和发展趋势,提出了相关防治建议。(1)成因表现为复杂的断裂构造导致流域内松散物源丰富,较大的相对高差提供了良好势能条件,而汛期集中强降雨则提供了动能条件,且雨量条件中当日雨量与前期有效降雨量之间具有幂函数关系; (2)发生特征表现出典型的空间群发性(包括2005-06-30群发性泥石流、2005-08-11群发性泥石流和2006-07-14群发性泥石流)与时间的夜发性; (3)危害方式主要包括淤埋、冲毁、侵蚀、堵河4种,泥石流已造成74人死亡; (4)发展趋势表现为泥石流沟多处于形成期和发展期(113条,占89%),发生的年际准周期由20a缩短至不足10a,且发生条(次)由4条(次)增加至44条次(2005年); (5)泸定县泥石流防治的突出问题表现为城镇泥石流问题、泥石流堵塞主河问题、风景区泥石流问题与冲沟泥石流问题,建议通过科学规划、风险防御体系构建、土木工程治理、监测预警等措施予以防御。     

Non-linear dynamics and pattern formation in a vertical fluid layer heated from the side

We study both experimentally and numerically the convective flow in a tall vertical slot with differently heated walls. The flow is investigated for the fluid with the Prandtl number Pr=26, which is large enough to ensure the traveling waves as primary instability and small enough to prevent boundary layer convection. The flow evolution is determined on the base of the visual observations, power spectra and amplitude analysis. In the numerical simulations of two- and three-dimensional flows, we accept an assumption of an infinite fluid layer. The satisfactory agreement with experiment is observed, and the sequence of convection states is discovered. It starts with a plane-parallel flow as primary solution, which becomes unstable to two counter-propagating waves. It is followed by a tertiary three-dimensional flow in the form of wavy traveling waves. As the Grashof number is increased even further, a chaotically oscillating cellular pattern consisting of the pieces of broken waves arises. The formation of a structure in the form of the vertical rolls chaotically modulated along axes concludes this complicated picture.