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Kinetic studies of ligand substitutions of the six-coordinated Ru^sup II^ pseudo-macrocyclic complex [Ru(CHDH)^sub 2^- (PPh^sub 3^)^sub 2^] (CHDH=cyclohexanedione-dioximato) have been spectrophotometrically investigated in a variety of solvents and at 70, 80, 85 and 90°C. The reactions studied are of the form: [(PPh^sub 3^)Ru(CHDH)^sub 2^(PPh^sub 3^)] + L =[(PPh^sub 3^)Ru(CHDH)^sub 2^L] + PPH^sub 3^ where L is imidazole, pyridine, piperidine or thiophene or a solvent molecule (PhCl, PhMe, MeCN, DMSO or DMF). The solvolysis reactions with chlorobenzene and toluene proceed to an equilibrium position favoring the bis-triphenylphosphine complex. All other reactions proceed to completion. From a mechanistic point of view the reactions were found to proceed through the formation of a five coordinate intermediate that possesses little or no discriminating ability towards the incoming nucleophiles. The rate data were thus interpreted in terms of a dissociative (D) or dissociative interchange (Id) mechanism. Activation parameters ΔH^sup [double dagger]^ and ΔS^sup [double dagger]^ are reported. Preliminary studies on the solvatochromic behavior of [Ru(CHDH)^sub 2^(PPh^sub 3^)^sub 2^] and the corresponding mixed complexes are discussed.[PUBLICATION ABSTRACT]

Kinetics of the reduction of potassium hexacyanoferrate (III) with sodium met bisulfite was investigated as a function of pH and at four temperatures, viz. 15o, 20˚, 25˚and 30˚C. The ionic strength was maintained at 1.0 M KCl. The pH range used varied between 2.6 to4.7 using McIlvaine phosphate /citric acid buffer system. The second order observed rate constant was found to follow an inverse H+ dependence of the form kobs= k1 + k2/[H+]. At 298.15 K, the second order rate constant k1= (1.02 ± 0.20) X 10-2 s-1 and -1mol-1L the first order rate constant k2= The activation parameters for k1 are: ΔH‡= 73.64 kJ mol-1, ΔS‡= -36.63 JK-1 mol-1and ΔG‡= 84.56 kJ mol-1 and for k2 are 41.71 KJ mol-1, -205.03 JK-1 mol-1 and 102.84 KJ mol-1 respectively. The kinetic data were very well explained by invoking radical mechanism in which the HSO3- and SO32- formed HSO3* and SO3-* radicals, alternatively the redox process could take place by a mechanism in which a fast reversible equilibrium is established between the hydrogen ions and hexacyanoferrate (III), followed by a slow reaction of the protonated species with the sulfite ion leading to the formation of sulfite free radical. التأثير الحركي تحرى دراسة تفاعل K3[Fe(CN)6] مع Na2S2O5 كدالة في pH عند أربع درجات حرارة هي : 15, 20، 25، 30 oC و قوة أيونية ثابتة مقدارها .1 M, KCl قيم الأس الهيدروجيني (pH) تراوحت بين 2.6- 4.7 باستخدام محلول McIlvaine المنظم المكون من نظام phosphate/citric acid. درس تأثير درجة الحرارة للحصول على معايير التنشيط ΔS 2 ‡ ΔG _ ‡ΔH. و قد وجد أن ثابت معدل التفاعل ذو الرتبة الثانية ، الملاحظ kobs يتناسب تناسبا عكسيا مع تركيز Kobs = k1 + k2/[H]. و عند درجة حرارة 298.15K وجد أن قيمة ثابت المعدل ذو الرتبة الثانية k1= (1.02 } 0.20)×10-2 s-1mol-L بينما قمية ثابت المعدل ذو الرتبة الأولى k2= (6.33 } 0.12)×10-6 s -1، و معايير تنشيط k1 هي : ΔH ‡ = 73.64 kJ mol- ΔS 2 1 ‡ = -36.63 JK-1 mo-1 و ΔG -1 ‡ = 84.56 kJ molk _ -1 هي : 41.71 kJ mol-205.03 JK 2 -1 و 102.84 kJ mol-1 على التوالي. و تم تفسير البيانات الحركية بالاستناد إلى ميكانيكية الشقوق، حيث ينتج من تفاعل HSO3 و SO-2 مع معقد الحديد الثلاثي تكوين شقوق حرة هي HSO3 و SO و ذلك بانتقال إلكترون منهما إلى الحديد الثلاثي، و يمكن أن تحدث عملية الأكسدة و الاختزال من قبل ميكانيكية يحصل فيها اتزان عكسي سريع بين أيونات الهيدروجين و hexacyanoferrate(III) متبوعا بتفاعل بطئ للمعقد الناتج مع أيون السلفايت لتكوين شق السلفايت الحر.

In aircraft structures and engines, fatigue damage is manifest in the progressive emergence of distributed surface cracks near locations of high stress concentrations. At the present time, reliable methods for prediction of fatigue crack initiation are not available, because the phenomenon starts at the atomic scale. Initiation of fatigue cracks is associated with the formation of Persistent slip bands (PSBs), which start at certain critical conditions inside metals with specific microstructure dimensions. The main objective of this research is to develop predictive computational capabilities for plasticity and fatigue damage evolution in finite volumes. In that attempt, a dislocation dynamics model that incorporates the influence of free and internal interfaces on dislocation motion is presented. The model is based on a self-consistent formulation of 3-D Parametric Dislocation Dynamics (PDD) with the Boundary Element method (BEM) to describe dislocation motion, and hence microscopic plastic flow in finite volumes. The developed computer models are bench-marked by detailed comparisons with the experimental data, developed at the Wright-Patterson Air Force Lab (WP-AFRL), by three dimensional large scale simulations of compression loading on micro-scale samples of FCC single crystals. These simulation results provide an understanding of plastic deformation of micron-size single crystals. The plastic flow characteristics as well as the stress-strain behavior of simulated micropillars are shown to be in general agreement with experimental observations. New size scaling aspects of plastic flow and work-hardening are identified through the use of these simulations. The flow strength versus the diameter of the micropillar follows a power law with an exponent equal to -0.69. A stronger correlation is observed between the flow strength and the average length of activated dislocation sources. This relationship is again a power law, with an exponent -0.85. Simulation results with and without the activation of cross-slip are compared. Discontinuous hardening is observed when cross-slip is included. Experimentally-observed size effects on plastic flow and work- hardening are consistent with a \"weakest-link activation mechanism\". In addition, the variations and periodicity of dislocation activation are analyzed using the Fast Fourier Transform (FFT). We then present models of localized plastic deformation inside Persistent Slip Band channels. We investigate the interaction between screw dislocations as they pass one another inside channel walls in copper. The model shows the mechanisms of dislocation bowing, dipole formation and binding, and dipole destruction as screw dislocations pass one another. The mechanism of (dipole passing) is assessed and interpreted in terms of the fatigue saturation stress. We also present results for the effects of the wall dipole structure on the dipole passing mechanism. The edge dislocation dipolar walls is seen to have an effect on the passing stress as well. It is shown that the passing stress in the middle of the channel is reduced by 11 to 23% depending on the initial configuration of the screw dislocations with respect to one another. Finally, from large scale simulations of the expansion process of the edge dipoles from the walls in the channel the screw dislocations in the PSB channels may not meet \"symmetrically\", i.e. precisely in the center of the channel but preferably a little on one or the other side. For this configuration the passing stress will be lowered which is in agreement to experimental observations.

Lithography is the critical step in the fabrication of nanostructures for integrated circuit manufacturing. It consists of a sequence of operations that include numerous thermal processes where a semiconductor substrate is baked at an elevated temperature or cooled from one. Substrate temperature uniformity during thermal processing is the usual process objective. In conventional systems substrates are baked with so-called “bake plates” and cooled with so-called “chill plates.” Baking is usually followed immediately by chilling to bring the substrate to a temperature suitable for the subsequent process. These plates have large thermal mass with very slow response, and operate at fixed temperatures. They are optimized for steady state plate temperature uniformity. Conventional thermal processing modules have a number of drawbacks. They cannot address transient or spatial process variations from substrate to substrate due to disturbances. In addition, transferring substrates from a bake plate to a chill plate requires a finite time, contact with a robotic arm, and motion through the ambient. All of these induce nonuniformities on the substrate while still at an elevated temperature where processing is ongoing. These issues (and others) motivate our novel thermal processing module that enables programmable plate temperature profiles in both space and time. The module also integrates the bake and chill functions into a single unit, eliminating the need for substrate transfer. Experimental data is presented that demonstrates the processing capabilities of the module.

Forest fires destroy productive land throughout the world. In Brazil, mainly the Northeast of Brazil (NEB) is strongly affected by forest fires and bush fires. Similarly, there is no adequate study of long-term data from ground and satellite-based estimation of fire foci in NEB. The objectives of this study are: (i) to evaluate the spatiotemporal estimation of fires in NEB biomes via environmental satellites during the long term over 1998–2018, and (ii) to characterize the environmental degradation in the NEB biomes via orbital products during 1998–2018, obtained from the Burn Database (BDQueimadas) for 1794 municipalities. The spatiotemporal variation is estimated statistically (descriptive, exploratory and multivariate statistics) from the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Standardized Precipitation Index (SPI) through the Climate Hazards Group InfraRed Precipitation Station (CHIRPS). Moreover, we identify 10 homogeneous groups of fire foci (G1–G10) with a total variance of 76.5%. The G1 group is the most extended group, along with the G2 group, the exception being the G3 group. Similarly, the G4–G10 groups have a high percentage of hotspots, with more values in the municipality of Grajaú, which belongs to the agricultural consortium. The gradient of fire foci from the coast to the interior of the NEB is directly associated with land use/land cover (LULC) changes, where the sparse vegetation category and areas without vegetation are mainly involved. The Caatinga and Cerrado biomes lose vegetation, unlike the Amazon and Atlantic Forest biomes. The fires detected in the Cerrado and Atlantic Forest biomes are the result of agricultural consortia. Additionally, the two periods 2003–2006 and 2013–2018 show periods of severe and prolonged drought due to the action of El Niño.

Background Estrogen and progesterone receptors are expressed in the anal canal. Fecal control deteriorates after menopause. This phenomenon is related to decreased circulating levels of estrogen and progesterone due to ovarian failure at menopause. Aim of work To study the effects of estrogen and progesterone on inflammatory cells, submucosal collagen fibers, and vascular plexus of the anal canal of postmenopausal women. Subjects and methods Experiments were performed on samples of anorectal tissue obtained from 40 women, 19 menstruating (group I), and 21 postmenopausal women (group II). Investigations included immunohistochemistry of estrogen and progesterone receptors and CD34. Results In negative estrogen receptors (ER) and progesterone receptors (PR), inflammatory cells, submucosal blood vessels, collagen type I were nonsignificantly changed in postmenopausal women relative to menstruating women (P > 0.05) whereas, in positive ER and PR, inflammatory cells and collagen I were significantly increased and submucosal blood vessels were significantly decreased in postmenopausal women relative to menstruating women (P < 0.05). Conclusion Estrogen and progesterone, in menstruating women, produce beneficial effects by decreasing incidence of inflammation and increasing anal canal submucosal blood vessels number and collagen types I, thus both hormones have a positive effect on anal compliance and pressure.

Objectives: This study was done for evaluation of children’s anxiety level with three different injection techniques of local anesthesia including the standard concealment technique, showing the dental syringe before injection and camouflaging by sleeves. Material and method: 60 patients, ranging from 7 -12 years old, required infiltration anesthesia in the upper arch were selected for this study. They were randomly allocated into 3 groups (n=20) according to the technique used for administration of local anesthesia. Group (1) the control group in which the basic injection technique was used.