Ligand-Metal Surface Interactions: Synthesis, Structure and Reactivity

Creep behavior of the ZK60 magnesium alloy was investigated using impression creep technique. The tests were carried out under constant punching stress at high temperatures (175, 200 and 225 °C) under low stresses (25, 50, 75 and 100 MPa) and at low temperatures (100, 125 and 150 °C) under high stresses (100, 125, 150 and 175 MPa). The creep mechanism of the extruded ZK60 magnesium alloy is grain boundary sliding by dislocation climbing obtained at low temperature and high pressure. At high temperature and under low pressure, the creep mechanism of the extruded ZK60 magnesium alloy is grain boundary diffusion by grain boundary sliding. The initial microstructure of the extruded ZK60 magnesium alloy was composed of mainly Mg phase and a little MgZn phase. Under the conditions of low temperature and high pressure, MgZn2 phase precipitated during creep deformation. Under the conditions of high temperature and low pressure, MgZn2 phase and a small amount of Zr-Zn phase precipitated during creep deformation. The creep resistance of magnesium alloy ZK60 under the conditions of low temperature and high pressure is better than under the conditions of high temperature and low pressure.

The contribution of coping related variables and cardiac vagal activity on the performance of a dart throwing task under pressure

Effect of time Pressure on Dynamic Visual Search Performance

The preparation of graphene with high quality serves as a prerequisite for its usage. Traditional methods of graphene production, represented by liquid-phase exfoliation and chemical vapor depositi...

The etching of polysiloxane spin‐on‐glass (SOG) layers on aluminum by a fluorine‐based plasma has been studied by Auger electron spectroscopy. The etching of such film by , , and is characterized by a residual film formation which is significantly thicker than the residues found after etching, under identical conditions, of a chemically vapor deposited (CVD) silicon dioxide on aluminum. A study of the residual layer composition is presented for various film structures, processing, and etching conditions for three types of reactive ion etching (RIE) systems operating at high, medium, and low pressures. The results indicate the presence of fluorocarbon polymer‐like residual films, typical for each one of the systems. The thicker residual layer was found for SOG films on aluminum etched at high pressure. The film structure, as found by Auger electron spectroscopy, is of fluorocarbon material on an aluminum oxide. The formation of such residual layer can be reduced by decreasing the gas pressure in the system and increasing the bias between the sample and the plasma during etching. For the films etched in the very low pressure range, about 2–3 mt, the residual film is thin, 0.5–1.0 nm, and is not much different from those found for CVD oxide. The results are also compared to the residues found after etching similar films on silicon.

Abstract. The aims of this study were to assess the predictive role of coping-related variables (CRV) on cardiac vagal activity (derived from heart rate variability), and to investigate the influence of CRV (and cardiac vagal activity) on prone rifle shooting performance under low pressure (LP) and high pressure (HP) conditions. Participants ( n = 38) competed in a shooting task under LP and HP. Cardiac vagal activity measurements were taken at baseline, task, and recovery for 5 min, alongside ratings of stress via a visual analogue scale. Upon task conclusion, self-report measures of motivation, stress appraisal, attention, perceived pressure, and trait CRV questionnaires (Decision-Specific Reinvestment Scale [DSRS], Movement-Specific Reinvestment Scale [MSRS], and Trait Emotional Intelligence Questionnaire [TEIQue]) were completed. Results indicated that task cardiac vagal activity was predicted by resting cardiac vagal activity and self-control in HP and LP. Post-task cardiac vagal activity was predicted by resting cardiac vagal activity in both conditions with the addition of a trait and state CRV in HP. Cardiac vagal reactivity, the change from resting to task, was predicted by resting cardiac vagal activity and self-control in LP and HP. Cardiac vagal recovery, the change from task to post-task, was predicted by a trait CRV in HP. Shooting performance was predicted by experience and cardiac vagal activity in LP and cardiac vagal activity and a trait in HP. Findings suggest both CRV and cardiac vagal activity influence cardiac vagal activity throughout a pressure task. Additionally, shooting performance directly influences cardiac vagal recovery.

The importance of cardioplegic infusion pressure in neonatal myocardial protection

A numerical modeling study is presented concerning the role of total pressure in gas-phase nucleation. We consider a generic self-clustering mechanism for particle production in which the cluster transport properties are assumed to scale with monomer properties. A steady-state isothermal plug flow reactor model is considered in which axial diffusion of gas species is allowed. Species conservation equations with appropriate boundary conditions are solved in the one-dimensional reactor space. A steady-state nucleation current is shown to be achievable when the monomer concentration is fixed, regardless of the total pressure. In the case when the monomer concentration is varied, we demonstrate that diffusion can play a critical role at low pressures, where the nucleation rate is found to be highly pressure-sensitive. In this regime steady-state nucleation is not possible. As pressure increases, the nucleation rate becomes gradually pressure-insensitive and approaches the high-pressure limit. A dimensionless analysis is performed for a series of irreversible clustering reactions, and the effects of dimensionless system parameters on the nucleation rate are presented as a function of pressure. The results indicate that to minimize particle formation in chemical vapor deposition reactors while maintaining high deposition rates one should operate in the pressure-dependent regime, with low total reactor pressures and high partial pressures of reactants.

The laryngeal mask airway (LMA) is a large foreign body that exerts pressure on the pharyngeal mucosa, which may lead to throat discomfort. To determine whether intracuff pressures are associated with such discomfort, a randomized, double-blind study was performed to determine the effect of high versus low intracuff pressures. Seventy healthy women were randomly allocated to two groups with different LMA intracuff pressures: 30 mmHg (low pressure) or 180 mmHg (high pressure). Pressures were controlled with a microprocessor-controlled monitor. Insertion of the LMA was performed by one investigator and facilitated with propofol and verified fiberoptically. Anesthesia was maintained with enflurane and nitrous oxide. The LMAs were removed while the patients were still asleep. Patients assessed their laryngopharyngeal complaints (sore throat, dysphagia, hoarseness) at 8, 24, and 48 h after operation on a 101-point numerical rating scale. No significant difference was found in the overall incidence of complaints between both groups (low pressure: 50%; high pressure: 42%). On the day of surgery, dysphagia (38%) was more frequent than sore throat (16%) or hoarseness (6%) (P < 0.05) within the high-pressure group. In the low-pressure group, the incidence of these complaints was not significantly different (33%, 20%, and 23%, respectively). On the following day, dysphagia was still present in 20% of the women in both groups, and other symptoms comprised 10% or less of the reported complaints. Differences in LMA intracuff pressures did not influence either the incidence or severity of laryngopharyngeal complaints.

Gillard, C. L., Ranatunga, N. K. and Conner, R. L. 2012. The effect of foliar fungicide application timing on the control of dry bean anthracnose. Can. J. Plant Sci. 92: 109–118. Anthracnose caused by Colletotrichum lindemuthianum is a major disease of dry bean (Phaseolus vulgaris L.), reducing seed quality and yield. A study carried out in 2005 and 2006 at Exeter, ON, and at Morden, MB, determined that a sequential application of fungicide at the correct time is crucial for the effective management of the disease. The effect of the fungicides azoxystrobin and pyraclostrobin at four single foliar application timings at 5th trifoliolate (A), 1st flower (B), full flower (C) and 10 d after full flower (D) and at three sequential timings (A+C, B+C, and B+D) were evaluated under low and high disease pressure conditions. Data were collected on leaf vein and pod infection, plant maturity, dockage, pick, seed weight, yield and return on investment. Results were analyzed using analysis of variance (ANOVA) and contrast comparisons were carried out for various treatment combinations. Differences between the two fungicides for leaf symptoms were not apparent under low disease pressure, but occurred early in plant development under high disease pressure. Pyraclostrobin-treated plots produced a higher yield under high disease pressure and better quality seeds at both high and low disease pressure conditions. A single fungicide application at the A timing gave higher yield under low disease pressure, while timings B and C gave a higher yield under high disease pressure. A sequential application often provided greater anthracnose control and improved yield and seed quality, compared with single application timings. For the sequential application timings, the highest yields occurred at the A+C timing under low disease pressure, and at the A+C or B+C timing under high disease pressure.

Mechanisms that underlie autoregulation in the newborn vasculature are unclear. Here we tested the hypothesis that in newborn porcine cerebral arteries intravascular pressure elevates wall tension, leading to an increase in intracellular calcium concentration ([Ca2+]i) and a constriction that is opposed by pressure-induced K+ channel activation. Incremental step (20 mmHg) elevations in intravascular pressure between 10 and 90 mmHg induced an immediate transient elevation in arterial wall [Ca2+]i and a short-lived constriction that was followed by a smaller steady-state [Ca2+]i elevation and sustained constriction. Pressures between 10 and 90 mmHg increased steady-state arterial wall [Ca2+]i between approximately 142 and 299 nM and myogenic (defined as passive-active) tension between 25 and 437 dyn/cm. The relationship between pressure and myogenic tension was strongly Ca2+ dependent until forced dilation. At low pressure, 60 mM K+ induced a steady-state elevation in arterial wall [Ca2+]i and a constriction. Nimodipine, a voltage-dependent Ca2+ channel blocker, and removal of extracellular Ca2+ similarly dilated arteries at low or high pressures. 4-Aminopyridine, a voltage-dependent K+ (Kv) channel blocker, induced significantly larger constrictions at high pressure, when compared with those at low pressure. Although selective Ca2+-activated K+ (KCa) channel blockers and intracellular Ca2+ release inhibitors induced only small constrictions at low and high pressures, a low concentration of caffeine (1 microM), a ryanodine-sensitive Ca2+ release (RyR) channel activator, increased KCa channel activity and induced dilation. These data suggest that in newborn cerebral arteries, intravascular pressure elevates wall tension, leading to voltage-dependent Ca2+ channel activation, an increase in wall [Ca2+]i and Ca2+-dependent constriction. In addition, pressure strongly activates Kv channels that opposes constriction but only weakly activates KCa channels.

A study of scaling 3D experiment and analysis on feasibility of SAGD process in high pressure environment

Deployable aeroshells offer the promise of achieving larger aeroshell surface areas for entry vehicles than otherwise attainable without deployment. With the larger surface area comes the ability to decelerate high-mass entry vehicles at relatively low ballistic coefficients. However, for an aeroshell to perform even at the low ballistic coefficients attainable with deployable aeroshells, a flexible thermal protection system (TPS) is required that is capable of surviving reasonably high heat flux and durable enough to survive the rigors of construction handling, high density packing, deployment, aerodynamic loading and aerothermal heating. The Program for the Advancement of Inflatable Decelerators for Atmospheric Entry (PAIDAE) is tasked with developing the technologies required to increase the technology readiness level (TRL) of inflatable deployable aeroshells, and one of several of the technologies PAIDAE is developing for use on inflatable aeroshells is flexible TPS. Several flexible TPS layups were designed, based on commercially available materials, and tested in NASA Langley Research Center's 8 Foot High Temperature Tunnel (8ft HTT). The TPS layups were designed for, and tested at three different conditions that are representative of conditions seen in entry simulation analyses of inflatable aeroshell concepts. Two conditions were produced in a single run with a sting-mounted dual wedge test fixture. The dual wedge test fixture had one row of sample mounting locations (forward) at about half the running length of the top surface of the wedge. At about two thirds of the running length of the wedge, a second test surface drafted up at five degrees relative to the first test surface established the remaining running length of the wedge test fixture. A second row of sample mounting locations (aft) was positioned in the middle of the running length of the second test surface. Once the desired flow conditions were established in the test section the dual wedge test fixture, oriented at 5 degrees angle of attack down, was injected into the flow. In this configuration the aft sample mounting location was subjected to roughly twice the heat flux and surface pressure of the forward mounting location. The tunnel was run at two different conditions for the test series: 1) 'Low Pressure', and 2) 'High Pressure'. At 'Low Pressure' conditions the TPS layups were tested at 6W/cm2 and 11W/cm2 while at 'High Pressure' conditions the TPS layups were tested at 11W/cm2 and 20W/cm2. This paper details the test configuration of the TPS samples in the 8Ft HTT, the sample holder assembly, TPS sample layup construction, sample instrumentation, results from this testing, as well as lessons learned.

Model systems for studying molecular surface chemistry have evolved from single crystal surfaces at low pressure to colloidal nanoparticles at high pressure. Low pressure surface structure studies of platinum single crystals using molecular beam surface scattering and low energy electron diffraction techniques probe the unique activity of defects, steps and kinks at the surface for dissociation reactions (H-H, C-H, C-C, O=O bonds). High-pressure investigations of platinum single crystals using sum frequency generation vibrational spectroscopy have revealed the presence and the nature of reaction intermediates. High pressure scanning tunneling microscopy of platinum single crystal surfaces showed adsorbate mobility during a catalytic reaction. Nanoparticle systems are used to determine the role of metal-oxide interfaces, site blocking and the role of surface structures in reactive surface chemistry. The size, shape and composition of nanoparticles play important roles in determining reaction activity and selectivity and is covered in this tutorial review.

Microcrystalline growth regimes and solar cells obtained in different pressure and silane depletion conditions are studied in a large area KAI-S plasma reactor. The microcrystalline material quality is systematically investigated by Fourier Transform Photocurrent Spectroscopy (FTPS) to evaluate the defect density. It is shown that higher pressure and silane depletion positively affect the material quality. A clear correlation between FTPS measurements and cell efficiency is established, showing that the limiting factor is the material quality of the intrinsic microcrystalline layers. The highest efficiency achieved so far is 8.2% for a 1.2 μm thick microcrystalline solar cell deposited at 3 A/s on glass coated with ZnO deposited by low pressure chemical vapor deposition. The efficiency drops to 6.4% for solar cells deposited at 9 A/s in conditions where silane powder is present in the plasma. Upon modifying the reactor geometry in order to suppress powder formation, solar cells achieve 7.0% efficiency at 12 A/s. The results can be described by pressure and silane depletion dependent ion bombardment. Transition curves from amorphous to microcrystalline are studied, revealing ion bombardment induced amorphization of the layer at low pressure and low silane depletion. Modeling of the ion energy bombarding the substrate supports this interpretation.