Increase Of Initial Pressure Research Articles

Quantitative response of trehalose and glycerol syntheses by Candida krusei to osmotic stress of the medium

The effect of osmotic stress on the biosyntheses of trehalose and glycerol by Candida krusei was quantitatively studied. With the increase of initial osmotic pressure (IOP) between 959 and 2108 mOsm kg −1, the cell growth and trehalose accumulation were decreased; the extracellular and intracellular glycerol syntheses were enhanced with an increase of IOP from 1320 to 1678 mOsm kg −1, and leveled off at an even higher IOP (i.e. 2108 mOsm kg −1). The cellular response to medium osmotic pressure was also dependent on the physiological state of cells (growth phase). The cells in exponential growth phase survived better than those in stationary and lag phases. For the exponential phase cells, the glycerol concentration doubled and the trehalose content increased 19% compared to the control. In contrast, for the lag phase cells, the trehalose content decreased while the glycerol synthesis was enhanced. The results are considered helpful to the further understanding of the metabolism of the osmophilic yeast under osmotic environments and the work may be useful for quantitative manipulation of the metabolites’ production on a large scale.

05/00611 Effective reforming of methane with CO 2 and O 2 to low H 2/CO ratio syngas over Ni/MgO [sbnd]SiO 2 using fluidized bed reactor

Biomass-derived syngas composition varies considerably depending on different feedstocks and processing techniques and thereby complicates the combustion control. A study on the effects of variations in the fuel composition and initial pressure on the characteristics of premixed H2/CO/CH4 flames was conducted using the spherical expanding flame method and CHEMIKIN package. Experimental measurements and numerical simulations were performed at an initial temperature of 303 K, equivalence ratios of 0.6–1.5 and pressures of 0.1–0.5 MPa with a wide range of H2/CO/CH4 compositions. The thermal and chemical kinetic analyses are also presented. The measured laminar flame speed was compared with simulations using the Li mechanism. The experimental data show a reasonable agreement with the calculated values, especially at fuel-lean and low pressure conditions. With the increase of H2 fraction in the fuel, the laminar flame speed increases significantly, but for the CH4 enrichment flame, the behavior is quite the contrary that it has the lowest laminar flame speed. With the increase of CO fraction in the fuel, the laminar flame speed does not change much. The thermal and chemical kinetic analyses indicate that the CO addition has more effect on the adiabatic flame temperature but only plays a small role in the chemical effect compared to that of the H2 addition. On the other hand, at elevated pressures, the Li mechanism gives slight overestimations for lean mixtures but underestimations for rich mixtures. The laminar flame speed decreases with the increase of initial pressure under tested equivalence ratio which is mainly due to the increasing unburned mixture density and decreasing H, OH radicals concentrations.

Influence of initial pressure on the explosibility of cork dust/air mixtures

Abstract Flammability studies of air/cork dust mixtures were conducted in a near-spherical 22.7 l explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as air-dispersed dust clouds and the uniformity of the dispersion in the chamber was evaluated through optical dust probes. Tested particle dust had mass median diameters of 71.3 and 222.1 μm and the covered dust cloud concentration was up to 700–800 g/m3. Measured explosion parameters included minimum explosion concentration, maximum explosion pressure and maximum rate of pressure rise. The effect of initial pressure on the explosion characteristics parameters was studied by varying the initial absolute pressure from 0.9 to 2.2 bar, and it was found that as initial pressure increases, there is a proportional increase of minimum explosion limit, maximum explosion pressure, and maximum rate of pressure rise.

Influence of initial pressure on cork dust/air mixtures explosibility

Flammability studies of air/cork dust mixtures were conducted in a near-spherical 22.7 L explosibility test chamber, using 2500 J pyrotechnic ignitors. The suspension dust burned as air-dispersed dust clouds and the uniformity of the dispersion in the chamber was evaluated through optical dust probes. Tested particles dust had mass median diameters of 71.3 μm and 222.1 μm and the covered dust cloud concentration was up to 700-800 g/m 3 . Measured explosion parameters included minimum explosion concentration, maximum explosion pressure and maximum rate of pressure rise. The effect of initial pressure on the explosion characteristics parameters was studied by varying the initial absolute pressure from 0.9 bar to 2.2 bar, and it was found that as initial pressure increases, there is a proportional increase of minimum explosion limit, maximum explosion pressure, and maximum rate of pressure rise.

Determination of Propane and Air Maximum Mixing Times

The model of gaseous fuel and air mixing, developed by the authors, is applied here to calculate maximum mixing times of propane and air. The degree of mixing is determined using the mass fraction of fuel while the rate of mixing is determined from the rate of this mass fraction. The values of both these parameters are local, i.e., measured within an infinitesimal element of fluid. A Eulerian representation is used. The model is based on the assumption that both fuel and air behave as a single chemical species. It is further assumed that pressure is low and only fuel and air are present within the fluid element. Under nonreacting conditions, the model is valid anywhere in the combustor. Under reacting conditions, the model is valid within those combustor regions where the fuel–air mixture is not flammable. The results of this analysis show that mixing times of propane and air are most reduced by high gradients of temperature and velocity, as long as these gradients provide in phase contribution. To a lesser degree, high gradients of pressure also help reduce mixing times. High initial pressure and temperature increase mixing time. Mixing with air penetration into the fuel flow is slower than with propane dispersion into the surrounding air. In general, the exact mixing time has to be determined numerically. Nevertheless, the analytical solutions included here provide maximum mixing times of propane and air under most conditions. These results provide important guidelines for the development of high intensity, high efficiency, and low emission combustors.

Fusion of vesicles with the air–water interface: the influence of polar head group, salt concentration, and vesicle size

Fusion of vesicles with the air–water interface and consequent monolayer formation has been studied as a function of temperature. Unilamellar vesicles of DMPC, DPPC, and DODAX (X=Cl −, Br −) were injected into a subphase containing NaCl, and the surface pressure (tension) was recorded on a Langmuir Balance (Tensiometer) using the Wilhelmy plate (Ring) method. For the zwitterionic vesicles, plots of the initial surface pressure increase rate (surface tension decrease rate) as a function of temperature show a peak at the phase transition temperature ( T m) of the vesicles, whereas for ionic ones they show a sharp rise. At high concentrations of NaCl, ionic DODA(Cl) vesicles seem to behave like zwitterionic ones, and the rate of fusion is higher at the T m. The influence of size was studied comparing large DODA(Cl) vesicles with small sonicated ones, and no significant changes were found regarding the rate of fusion with the air–water interface.

Haemorrheology of equine platelet-neutrophil aggregates

The filterability of platelet-neutrophil aggregates through filters containing 5 μm pores was determined to evaluate the potential of plateletneutrophil aggregates to alter blood flow in the microvasculature. Incubation of platelet-neutrophil mixture with platelet-activating factor (PAF) and with 0.5 μM adenosine diphosphate (ADP) resulted in large platelet-neutrophil aggregates which rapidly plugged filter pores. Incubation of platelet-neutrophil mixtures with lower concentrations of ADP resulted in small platelet-neutrophil aggregates that contained only one neutrophil. Filtration of these samples resulted in a 1.3-, 3.2- and 3.7-fold increase in initial filtration pressure at ADP concentrations of 0.05, 0.15 and 0.25 μM, respectively. We conclude that platelet-neutrophil aggregates have reduced deformability and may alter blood flow in the microvasculature.

Pumping, spraying, and mixing of fluids by electric fields

AbstractThe mechanism of electrostatic spraying of insulating fluids, such as air or organic solvents, into relatively conductive fluids, such as water, is investigated in this work. Experiments with air sprayed into water through an electrified capillary showed that the pressure inside the capillary increases, reaches a maximum, and then decreases as the applied voltage is increased. The initial pressure increase is due to the electric stress on the fluid interface, while the decrease is due to the Coulombic electrohydrodynamic flow generated near the end of the capillary. It is shown that electric fields can cause simultaneous pumping, spraying, and mixing of fluids. This phenomenon is demonstrated for air and kerosene in water.

A fundamental study of hydrogen supplemented natural gas vehicle to meet ULEV

In the present study, investigations were carried out to obtain data on combustion characteristics of methane gas and hydrogen supplemented methane gas in a constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The maximum combustion pressure increases as the initial pressure and hydrogen supplement rate increase, the total burning time is shorten by lowering the initial pressure and by increasing the hydrogen supplement rate. The maximum flame temperature and NO concentration increase by the initial pressure and hydrogen supplement rate increase. The flame propagation processes in near stoichiometric mixture are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate.

EXPERIMENTAL STUDY OF FLAME-SPREADING PROCESSES OVER Mg/PTFE/Mg THIN FOILS

An experimental study of flame-spreading behavior over thin Mg/PTFE/Mg foils (called Enerfoil™ Pyrotechnic Film) with thicknesses of 10/25/10 μm was conducted in an argon environment. This thin film pyrotechnic material has been designed to serve as an ignition enhancer in passenger-side airbag gas generators. The objective of this study was to determine the effects of initial chamber pressure and gap width between two foils on the intrinsic flame-spreading rate of Enerfoil™ films. In the experimental setup, the steady-state flame-spreading rate (VFS) was deduced from the flame-front trajectory measured by an array of fast-response Lead-Selenide (Pb-Se) IR photodetectors. The initial chamber pressure was varied from 0.1 to 10.5 MPa. Results indicated that for single-foil tests VFS decreased as the initial chamber pressure was increased; this observed trend is believed to be caused by a greater heat loss to the ambient gas at higher pressures. An experimental correlation was developed with a pressure exponent of −0.118. For double-foil tests, the gap width between two adjacent foils was varied from 50 to 400 μm. It was found that for double-foil tests there exists an optimal gap width for obtaining a maximum VFS at a given initial chamber pressure. The optimal gap width appears to become smaller as the initial chamber pressure increases. For each gap width tested, there is also an optimal pressure at which the VFS reaches a maximum. The existence of the optimal pressure and gap width is caused by the combination of several factors, including required physical space for complete gas-phase reactions, heat transfer rates to both unburned foils and ambient gases.

Influence of Hydrogen Pressure on the Properties of CVD Tungsten Silicide Films

In this paper, the properties of low pressure chemically vapor deposited tungsten silicide films processed from tungsten chlorides and silane are studied as a function of hydrogen initial partial pressure. By means of thermodynamic calculations, we have defined a priori the operating conditions leading to each silicide deposition. The corresponding films are grown in a cold‐wall reactor and characterized by x‐ray diffraction and scanning electron microscopy studies. Good agreement between theoretical and experimental results is obtained. The increase of initial hydrogen partial pressure has two possible consequences: a modification of the film composition for high partial pressure and a modification of the film growth rate for lower partial pressure.

Deposition and Properties of Reactively Sputtered Ruthenium Dioxide Thin Films as an Electrode for Ferroelectric Capacitors

Ruthenium dioxide (RuO2) films are studied for use as a bottom electrode of the (Ba, Sr)TiO3 thin-film capacitor. RuO2 films have been deposited by reactive DC magnetron sputtering of ruthenium at a relatively low sputtering power. Stoichiometric RuO2 films are obtained at oxygen partial pressures as low as 0.6 mTorr. The properties of the films have been investigated using techniques such as Rutherford backscattering spectrometry, Auger electron spectrometry, X-ray diffraction, and scanning electron microscopy. The oxygen composition in as-deposited RuOx films increases from 2.0 to 2.4 with the increase of initial O2 partial pressure from 1.2 to 5.6 mTorr at a sputtering power of 200 W. The films deposited under low oxygen partial pressures followed by annealing show preferential crystal growth in the [110] direction, whereas those deposited in high oxygen partial pressures show growth in the [101] direction. A resistivity of 65 µΩ·cm is obtained after annealing at 800°C. Even after high-temperature deposition and subsequent annealing processes, clear interfaces between (Ba, Sr)TiO3 and RuO2 films are obtained.

Metallic wastes from fuel assemblies

Investigation of a pulsed pneumatic transportation system for spent fuel is briefly described. Testing parameters for air transport included nozzle optimization and transportation range. The range of particles (30 to 40 mm metal chunks) was determined as a function of the nozzle diameter. A 35 mm diameter was determined to be optimal for the receiver volume and initial gas pressure. Experimental results showed that as receiver volume increases, the transportation range increases linearly until a critical volume is reached; at that point, range becomes constant. As initial gas pressure increases, the transportation range curve is displaced upwards. The system gave stable movement of the metal chunks, eliminating plugs in the standard operating regime. 5 refs., 3 figs.

Electric-discharge excited blast waves in a flat subsonic nozzle

The persistence of pressure waves generated by an electric discharge in the throat of a subsonic nozzle is studied analytically and numerically with particular reference to the operation of the high-power EUREKA excimer laser under construction at the national Italian ENEA Frascati laboratories. The attention is focused on transverse waves traveling parallel to the discharge electrodes. After some analytical estimates, a quasi-twodimensional numerical simulation is presented of the propagation of these waves in the anticipated geometry of the discharge chamber of the EUREKA laser. The possibility of reflection of pressure waves on the thermal slug left behind by the previous discharge is also considered. N a high-power, high-repetition-rate excimer laser, gas flows at a subsonic speed through a nozzle of elongated cross section in the throat of which an electric discharge is periodically fired with a repetition rate of the order of 1 kHz. Only about 1% of the energy released by the discharge is usefully converted into electromagnetic waves in the laser cavity positioned at the throat of the nozzle. All of the remaining energy instantaneously heats up the gas, with respect to the propagation time of sound, and produces blast waves that, if still present in the discharge chamber when the next pulse fires, may cause instability of the following discharges. A one-dimensional picture of the phenomenon is shown in Fig. 1. The initial instantaneous temperature and pressure increase subsequently divides up into three waves: an entropy wave (the thermal slug), which travels with the main flow velocity and forward and backward pressure waves with velocity V + a and V — a, respectively (a being the speed of sound). In the simplified one-dimensional situation depicted in Fig. 1, these waves propagate out and do not interfere with following discharges if only enough time is allowed for all three waves to abandon the discharge volume. Provided that V<a/2, the slowest wave is the entropy wave; therefore, this criterion may be expressed figuratively by saying that the gas where one discharge has occurred must be washed out of the discharge volume before another discharge may be fired. However, various circumstances may disrupt such an ideal behavior: 1) If the pressure waves are strong enough to behave as shock waves, the entropy change through the backward wave may change the thermodynamical state of the gas arriving at the discharge section. 2) Obstacles or bends in the feed and exhaust ducts may reflect the waves back onto the discharge section. 3) Transverse waves, propagating at an angle with respect to the flow direction, may be excited by disuniformities in the discharge and come back on reflection by the lateral walls. Problem 1 is not a major concern for the typical energy release during a discharge of the order of 50 -s-100 J/l under a gas pressure of the order of some atmospheres. The shock strength can be calculated from the equation of state of an ideal gas to be given by

Sensory and motor responses to rectal distention vary according to rate and pattern of balloon inflation

Anorectal motor activity and rectal sensation were recorded in 12 normal male subjects during ramp distention of the rectum with water and air at randomized rates of 10, 20, 50, and 100 mL/min and during intermittent rapid distention with air. There were no significant differences between the results of ramp inflation with water or with air, and the repeated infusion of the same medium yielded reproducible results. Ramp distention induced sigmoid pressure-volume profiles. Different sensations occurred at specific points on the pressure-volume curve and were maintained until succeeded by the next sensation. Initial perception of the distention occurred during the initial steep pressure increase, the sensation of wind occurred during the plateau phase, and the desire to defecate occurred at the onset of the final rapid ascent. Rectal sensations were induced at lower volumes at low infusion rates when the slope of the pressure-volume relationship was shallower than at high infusion rates. This suggests that the receptor triggering rectal sensation is not a simple volume or pressure receptor, but is more likely to be a slowly adapting mechanoreceptor lying parallel to the circular muscle of the rectal wall. During rapid intermittent distention, the rectal volumes required to elicit rectal sensations were lower than during ramp distention, although the pressure-volume curve was steeper. Moreover, sensations often only lasted a short period of time but recurred on deflation. These data suggest activation of an additional population of rapidly adapting or high threshold mechanoreceptors. Anal relaxation was always evoked by intermittent rectal distention and was almost always associated with a rectal sensation and an increase in external anal sphincter activity. In contrast, anal relaxation could be absent or delayed during ramp inflation, especially at lower infusion rates, suggesting that internal sphincter can maintain continence for a long period of time while the rectum is slowly filling. Rectal sensation and concomitant external anal sphincter activity was not associated with anal relaxation during ramp inflation; most subjects felt the sensation long after the pressure reached its lowest level. However, under all circumstances the onset of rectal sensation was associated with an increase of external anal sphincter electrical activity. In conclusion, the rectal sensory and anorectal motor responses to distention depend on the rate and pattern of distention, which may activate a different population of receptors. Results from different laboratories cannot be compared directly unless the pattern and rate of distention are the same.

Behavior of soil under a brief dynamic load

1. The damping coefficients both of cohesive and noncohesive soils practically do not depend on the state of the soils relative to the limit state almost up to loss of strength by the soil specimen. An increase of the initial lateral pressure and dry density of the noncohesive soil as well as a decrease of the moisture content of cohesive soil noticeably reduce the value of the damping coefficients (from 0.6 to 0.05 for noncohesive and from 0.3 to 0.15 for cohesive). The interval of variations of the damping coefficients obtained under conditions of small values of the initial lateral pressure (within 0.1 MPa) and combined stress state leads to the need for an experimental determination of the damping coefficients, at least for similar conditions. 2. The shear moduli for small values of the initial lateral pressure and under conditions of a combined stress state for cohesive soil depend on the level of the initial lateral pressure and for the noncohesive on the change in the moisture content. In the interval of stresses created in the specimen, when the initial lateral pressure does not exceed 0.098 MPa and the average static stress does not exceed 0.3 MPa, the shear moduli are practically proportional to the average stress. 3. Both volumetric strains and distortional strains under a brief dynamic shear load and under conditions of a combined stress state are far less than the strains from an equal static load. In this case, whereas the volumetric strains in shear for noncohesive soil have the character of compacting, for cohesive soils they are always loosening. 4. The description of the process of soil deformation as a result of a brief dynamic load obtained shows the possibility of determining the nonlinear reaction of soil to this load by means of the linear acceleration method, if the system under consideration can be represented as a system with one degree of freedom.

配合した三池炭抽出溶液の接触水素化処理反応

Hydrotreating of a blend of 25 percent SRC (derived from Miike Coal) and 75 percent Creosote Oil has been studied using batch autoclave under the various conditions. The result obtained here can be summarized as follows1) HI and BI conversions increase with an increase in reaction temperature, time and hydrogen initial pressure. Polymerization reaction of products, observed in the hydrotreating of SRC without solvent, is not observed in this study.2) Sulfur removal is from 65 to 90 percent and Nitrogen removal is from 10 to 28 percent.3) Yield of light fraction can be increased by using hydrogen donor solvent.4) Ni/Mo/Al2O3 catalyst is the most effective for hydrogenation of this filtrate, but Co/Mo/Al2O3 is better for sulfur removal.

Shock absorber with improved back check and anti‐dump valve mechanisms

A shock absorber of the direct acting type for vehicles in which improved riding characteristics are obtained by providing an additional back check valve mechanism and anti-dump valve mechanism. Both valve mechanisms are normally biased in a closed position, are opened in response to an initial pressure increase and move into a second closed position when pressure conditions reach a predetermined value above the lower initial pressure increase level. The back check valve mechanism can be made responsive either to the pressure in the compression space or the rebound space. The anti-dump valve mechanism is carried by the piston and controls initial and low pressure flow between the compression space and rebound space.

Central peptidergic stimulation in blood pressure control: role of enkephalins in rats.

1. The central blood pressure effects of the enkephalin analogue, d-Ala2-Met-enkephalin were investigated in normotensive rats and in spontaneously hypertensive rats. 2. In conscious Wistar rats, injection of 1.7, 17 and 170 nmol of d-Ala2-Met-enkephalin into the lateral brain ventricle produced dose-dependent blood pressure increases of 5.3 ± 1.8, 10.5 ± 2.8 and 15.3 ± 3.0 mmHg respectively. In contrast, in α-chloralose-anaesthetized rats, the same doses of the enkephalin analogue produced dose-dependent blood pressure falls of −8.9 ± 1.9, −11.1 ± 5.2 and −19.8 ± 8.4 mmHg. 3. The pressor responses to 170 nmol of d-Ala2-Met-enkephalin were blocked by intracerebroventricular pretreatment with the opiate receptor antagonists diprenorphine and naloxone at doses of 10–500 nmol. The depressor effects under anaesthesia were blocked by diprenorphine (10–100 nmol) but not by naloxone. 4. Spontaneously hypertensive rats showed enhanced pressor responses to centrally applied enkephalin when compared with normotensive rats. 5. Central injection of diprenorphine alone produced an initial short blood pressure increase followed by a long-lasting blood pressure fall, which was significantly greater in spontaneously hypertensive rats than in normotensive rats. 6. The results indicate that the central blood pressure effects of enkephalins depend on the state of consciousness and are mediated through naloxone- and diprenorphine-sensitive opioid receptors. 7. The increased sensitivity to centrally applied enkephalins and the depressor responses to the intracerebroventricular injection of diprenorphine suggest a central enkephalinergic contribution to the maintenance of hypertension in spontaneously hypertensive rats.

Stop-flow effects on human salivary composition and hydrostatic pressures

Saliva was collected, after cannulation of the parotid duct of six subjects, either without stimulation or at a constant flow-rate (FR) using gustatory stimulation. The normal secretory pressure at different parotid saliva FRs, the pressure developed during stop-flow (SF) and the compositional changes induced by SF were determined. Gustatory stimulation, where employed, was continued at the same intensity whilst flow was stopped and the pressure measured with a strain gauge. On SF, there was a rapid initial pressure increase of 5–20 mmHg, dependent on the preceding FR, which is interpreted as the normal secretory pressure, followed by a more gradual increase to a mean of 45 mmHg at high intensities of continued gustatory stimulation but with oscillations in amplitude of about 20 mmHg. Following SF for 3 min at a preceding FR of 1 ml/min, total protein concentration was temporarily decreased by about 40 per cent but several-fold increases in the concentrations of Mg, glucose and albumin occurred. Thus, following SF there may be a transient increase in permeability of the salivary tubules which allows some equilibration between the components of extracellular fluid and saliva.