Higher Pressure Values Research Articles

Production of fire extinguishing mixture by solid propellant propulsion

The behavior of fire suppression by water mist spray has been studied by using the experimental setup which employs the double-based solid propellant gas generator for water mist production. The burning products of solid fuel form a supersonic flow injected through the nozzle into the diffuser chamber having input for the water component ejected from the storage. High values of temperature and pressure at stagnation point impart the substantial kinetic energy to the flow, which provides the atomization of water droplets into mist spray. Since the water evaporation occurs already in the diffuser chamber due to the high temperature of input gas flow, the droplet size is gradually decreases to the lower limit value that could ever exist. The presence of vapor phase enlarges the volume of fire extinguishing jet allowing it to operate as a flooding agent (along with the effect of heat consumption due to water evaporation) at the very beginning of fire suppression process, much before the water droplets evaporation by the flame itself. Proposed technique of the water mist production has showed noticeable fire suppression capability through the series of testing application to the gasoline and wood model fire sources.

Repercussão da pressão positiva expiratória final na pressão de perfusão cerebral em pacientes adultos com acidente vascular hemorrágico

Positive intrathoracic pressure may cause hemodynamic changes, which can be transmitted to the cranial compartment, changing intracranial pressure and cerebral perfusion pressure. This can be increased when high positive end-expiratory pressure values are used. To measure the impact of different positive end-expiratory pressure levels on intracranial pressure, cerebral perfusion pressure and mean blood pressure. This study was conducted in a neurological intensive care unit and included 25 adult hemorrhagic stroke patients who were mechanically ventilated on airway pressure control mode. Patients were subjected to various positive end-expiratory values ranging between 0 and 14 cmH2O. The order of these values were randomized, and the variables were assessed five minutes after each new positive end-expiratory pressure level was initiated. Incremental positive end-expiratory pressures led to increased intracranial pressure (p < 0.001), however, no statistically significant changes were observed in mean blood pressure or cerebral perfusion pressure. In this population of patients with hemorrhagic stroke, positive end-expiratory pressure values up to 14 cmH2O did not alter cerebral perfusion pressure or mean blood pressure. Increased intracranial pressures were noted, although these elevations were not clinically significant.

The Evolving Price of Perfection

The Evolving Price of Perfection

Three Dimensional Seepage Analyses in Mollasadra Dam after Its Impoundments

Mollasadra dam is an earth fill dam with a clayey core and a height of 72 m from river bed, constructed on Kor River. pore water pressure in the dam was investigated following its construction and first and second impoundments. The dam was modeled by a finite element mesh. After the first and second dam impoundments, the overall trend in monitored pore water pressure was well modeled by the transient analysis. The result showed the six month time period between impoundments was long enough for the pore water pressure to reach equilibrium everywhere throughout the core, except where considerable initial constructioninduced pore water pressure was observed. High values of construction-induced pore water pressure at elevation2050 m did not dissipate completely during the 6 month period of almost constant reservoir level (el. 2098.3 m) and the pore pressures were still at the transient state throughout the core. Therefore, it was concluded that porepressures in the core of earth fill dams may not achieve steady state conditions even several months after the dam construction and impoundments.

Influence of NaCl concentration and high pressure treatment on thermal denaturation of soybean proteins

In the present work the effect of high pressure (HP) treatment in the presence of NaCl on the thermal behavior of soybean proteins was analyzed by differential scanning calorimetry. The thermograms obtained have shown that NaCl addition increased the thermal stability – increase in temperatures of denaturation (Td) – of both glycinin and β-conglycinin. HP treatments increased thermal stability of glycinin, but decreased that of β-conglycinin. High NaCl concentrations decreased (in glycinin) or inverted (in β-conglycinin) the effects of HP on thermal stability. Cooperativity of denaturation of glycinin was enhanced by NaCl and HP. Cooperativity of denaturation of β-conglycinin was enhanced by HP and also by NaCl at 0.2 mol/L but decreased with the combination of treatments. Salt addition increased the enthalpy, ΔH, of denaturation of glycinin and β-conglycinin, being this effect stronger on glycinin. HP treatment provoked the denaturation of both protein fractions. The presence of NaCl protected glycinin against HP-denaturation at any assayed salt concentration and pressure level, while β-conglycinin was only protected at 200 and 400 MPa, but was more denaturated at 600 MPa in the presence of 0.6 mol/L of NaCl. The knowledge provided by this work may be useful in the handling of high pressure-treated food with high NaCl content (e.g. meat emulsions, smallgoods) where soybean proteins are used as additives, in order to choose high pressure values to achieve their denaturation or predict the effects of ulterior thermal treatments. Thus, this knowledge may be useful to increase the use of high pressure in food industry.

Effect of Temperature and Pressure on Wear Properties of Ion Nitrided AISI 316 and 409 Stainless Steels

Abstract Stainless steels are widely used in chemical and other industries due to their corrosion resistance. However, because of their low hardness and wear properties, their applications are limited. Many attempts have been made to increase the surface hardness of these materials by using plasma techniques. Plasma nitriding is distinguished by its effectiveness, and for presenting a relatively low cost and being a clean process, producing hard surface layers on stainless steels. Aiming to verify the influence of the temperature and pressure on the modified resultant layers, samples of AISI 316 and 409 stainless steels were plasma nitrided in two different temperatures (450 and 500°C) and pressures of 400, 500, and 600 Pa for 5 h. After the nitriding treatment, the layers were analyzed by means of optical microscopy and wear tests. Wear tests were conducted in a fixed-ball micro-wear machine without lubrication. After the plasma nitriding treatment on AISI 316 and 409 samples, homogeneous and continuous layers were produced and their thicknesses increased as the temperature increased and as the pressure decreased. The nitriding treatment on the AISI 316 steel resulted on the formation of expanded austenite layers at 450°C and chromium nitrides (CrN and Cr2N) phases at 500°C. The nitriding treatment on AISI 409 yielded the formation of similar layers for both treatment temperatures; these layers constituted mainly chromium (Cr2N) and iron (Fe2N, Fe3N, and Fe4N) nitrides. After the nitriding treatment, the AISI 316 steel sample presented higher wear resistance for lower temperature and pressure values. The increase on layer fragility, for higher temperature and pressure values, can be responsible for this inverse tendency. The wear resistance of the nitrided AISI 409 sample followed a logic tendency: the harder the layer, the better the performance, i.e., the performance was improved with the increase in both the temperature and pressure.

Optimal process conditions for the isomerization–cracking of long-chain n-paraffins to high octane isomerizate gasoline over Pt/SO 42––ZrO 2 catalysts

An assessment of the process conditions for the isomerization–cracking of long-chain n-paraffins over commercial Pt/SO 4 2––ZrO 2 catalysts was made. Pretreatment and reaction conditions were optimized with a focus on the maximization of the yield of short, high octane branched paraffins for the gasoline pool. While selectivity was an important issue attention was also paid to the reduction of the yield to gases (C 1–C 4). Therefore cracking had to be modulated to produce the correct molecular size adjustment without scission to too much smaller fragments. Skeletal isomerization was to be maximized. The activity in both acid-catalyzed reactions had to be tuned while keeping a stable activity level. The only pretreatment condition assessed was the calcination temperature (screened in the 600–800 °C range). Calcination at 600 °C produced the highest activity level while 700 °C was convenient from the point of view of selectivity. The optimum temperature coincided with the production of the highest concentration of Brönsted acid sites. Regarding the reaction conditions, increasing temperature values augmented the conversion but also increased the cracking. Therefore optimum values were found at a moderate temperature, 225 °C, given the high reactivity of the feed. Space velocity values were analyzed with attention to the liquid C 5+ yield, the selectivity to branched isomers and the stability of the catalysts. Best yields to branched naphtha products were obtained at WHSV = 18 h – 1 . The H 2/hydrocarbon molar ratio was a function of the catalyst coking rate. A value of 10 was enough to attain a stable conversion value. The values of liquid yield as a function of pressure displayed a volcano pattern that was rationalized in terms of a non-classical bifunctional mechanism of reaction. High pressure values increased the concentration of Brönsted acid sites and hence the activity while high pressures enhanced hydrocracking and decreased the liquid yield. The optimal pressure value was 20 atm.

3D flow simulation at the geometry of thirteen main arteries of a human

Biomechanical properties of blood flow are researched in 13 main arteries of human body. 3D blood network model consists of regions such as aorta, carotid, iliac, renal and celiac sections. A real patient data is used as the geometric domain and the Womersley velocity profile is implemented as the inlet. Investigating 13 main arteries at once as a full system helps to improve the understanding of the short artery sections. Comparing the effects of velocity and flow patterns in 13 artery system shows a better understanding of biomechanical properties in dissected regions, especially at arterial branch points. The main purpose of this work is to simulate the blood flow using 13 branches of the most crucial and largest arteries in the chest and abdominal region of a human. It is thought as arteries and veins as simple tubes, so the artery is susceptible to biomechanical factors. Our focus here is arterial trees and their relation between the circulation systems which are constantly being researched in order to find substitutes clinically. Therefore, simulation in disease progression and clinical intervention are associated within artery wall mechanics. Results show that velocity, pressure and wall shear stress (WSS) distributions vary when examined with local bisections. Results also show that better representation of complex 13 artery bifurcation geometry gives more detail on the flow characteristics, hinting us the flow projections of a nozzle effect and high pressure increment at the level two bifurcation in the iliac. The narrowing of the arteries in the celiac region happens to show high speed and pressure values in the results. This is referred to as stenosis.

Antihypertensive Therapy in Diabetes: The Legacy Effect and RAAS Blockade

Two recently published post-monitoring follow-up studies of the United Kingdom Prospective Diabetes Study (UKPDS) have shown that although early and intensive treatment of hyperglycemia provides benefits for cardiovascular mortality that extend over time, the effects of a tight antihypertensive strategy in patients with diabetes did not seem to last during the following years. The authors concluded that blood pressure control is of crucial importance in patients with diabetes but is not protective against cardiovascular events when it is not sustained. Several lines of evidence suggest, however, that early and intensive antihypertensive treatment with some classes of drugs exerts benefits that may persist during the following years. Particularly, blockade of the renin-angiotensin-aldosterone system (RAAS) may interrupt the molecular and cellular mechanisms underlying cardiac and vascular remodeling and the maintenance of high blood pressure values. This review article critically discusses current evidence and explores the rationale for a legacy effect of RAAS blockade in hypertensive patients with diabetes.

The high hydrostatic pressure effect on shallow donor binding energies in GaAs–(Ga, Al)As cylindrical quantum well wires at selected temperatures

We have presented the behavior of a shallow donor impurity with binding energy in cylindrical-shaped GaAs/Ga 0.7Al 0.3As quantum well wires under high hydrostatic pressure values. Our results are obtained in the effective mass approximation using the variational procedures. In our calculations, we have not considered the pressure related Γ−X crossover effects. The hydrostatic pressure dependence on the expectation value of ground state binding energy is calculated as a function of wire radius at selected temperatures. We have also discussed the effects of high hydrostatic pressure and temperature on some physical parameters such as effective mass, dielectric constant, and barrier height. A detailed analysis of these calculations has proved that the effective mass is the most important parameter, which explains the dependency of donor impurity binding energies on the high hydrostatic pressure values.

Influence of probe application pressure on in vitro and in vivo capacitance (Corneometer CM 825®) and conductance (Skicon 200 EX®) measurements

The measuring probe of the electrical hydration instruments is equipped with a spring system to ensure a constant pressure of probe application on the skin surface. However, it is possible to trigger the measurement at, respectively, a low and a high force of probe application. It is the purpose of this paper to compare the in vitro and in vivo hydration values of the capacitance and conductance method at, respectively, low and high values of application pressure on the considered surface. In vitro capacitance and conductance hydration measurements were carried out at a low and a high pressure on a calibration filter pad impregnated with different alcohols and in vivo on different skin sites covering a wide range of hydration values. The in vitro results were pressure dependent and higher hydration values were noticed when the probes were applied with a high pressure compared with a low pressure. In vivo, the pressure effect was a function of the skin type and it was more pronounced for dry skin (40%), lower for normal skin (20%) and the lowest for hydrated skin (5-8%). This study confirms the influence of probe pressure application on the skin surface when carrying out capacitance and conductance hydration measurements.

Oligonucleotide-Based Amphiphilic Block Copolymers Interacting with Cell Membrane Models at the Air-Water Interface

Oligonucleotides have exceptional molecular recognition properties, which are involved in biological mechanisms such as gene silencing or cell-surface receptor recognition. In many cases, the cell membrane structure is barrier to investigate their use in human therapy for drug or gene delivery. However, this can be obviated by grafting a hydrophobic tail to the oligonucleotide. In this present work, we demonstrate that two oligonucleotides, one consisting of 12 guanosine units (G12), and the other one consisting of five adenosine and seven guanosine (A5G7) units, when functionalized with poly(butadiene), namely PB-G12 and PB-A5G7, can be incorporated into Langmuir monolayers of dipalmitoyl phosphatidyl choline (DPPC), which served as a cell membrane model. With surface pressure and surface potential-area isotherm, we observed that PB-G12 and PB-A5G7 affect the DPPC monolayer, even at high values of surface pressure. The effects from PB-G12 were consistently stronger, particularly in reducing the surface compressibility of the DPPC monolayers, which may have important biological implications. Multilayers of DPPC and nucleotide-based copolymers could be transferred onto solid supports, in the form of Y-type Langmuir-Blodgett films, in which the molecular-level interactions led to lower energies in the vibrational spectra of the nucleotide-based copolymers. The successful deposition of solid films opens the way for devices to be produced which exploit the molecular recognition properties of the nucleotides.

Dependence of the efficiency of a capillary column in gas chromatography on the relative pressure of the carrier gas

The effect of relative pressure on the efficiency of an open capillary column in gas chromatography was studied. It was shown that the relative pressure was not the only parameter determining the column efficiency. The pressure drop in the column is an additional parameter. At high values of relative pressure, the pressure drop in the column becomes determining for the column efficiency. The smallest value of a height equivalent to a theoretical plate (HETP) is achieved at the minimum values of the pressure drop and the relative pressure, which is accompanied by a decrease in the optimal flow rate of the carrier gas and an increase in the time of determination. The maximum improvement in the column efficiency is determined by the column properties and can exceed 12.5%, that is, the value predicted by Cramers for open capillary columns.

Electrogalvanized Low Carbon Steel Adhesion Tendency in Friction Processes Under Mixed Lubrication Regime

Although some authors work at times with large flat dies and evaluate friction under more realistic conditions than usual, pressure is not totally controlled. In any case, cohesive friction does not appear to have been well studied in literature, but pressure and sliding velocity may provide useful information about preventing the cohesive phenomenon in sheet stamping processes. In this work, the coefficient of friction (COF) for DC-05 electrogalvanized steel is experimentally evaluated under lubrication regime by flat face dies. These tests are also considered to reproduce friction conditions in the die-sheet-blankholder system at some stages of the deep drawing process. High pressure condition in a flat friction system can also be considered for studying the friction behavior in the die radius. This work investigates the influence of contact pressure and sliding velocity of the sheet on the COF value. Adhesion tendency during sliding is also evaluated. Sheets were lubricated with a prelube type mineral oil and different lubricant film thicknesses are present on the sheet as a result of the draining off time effect, an aspect that will be evaluated later. Although sliding velocity has almost no influence on the COF value, pressure has an influence that may be expressed by a potential mathematical function. The COF value tends to be constant for high enough pressure values. This behavior may be explained, in part, from the viewpoint of zinc acting as a typical soft metallic lubricant. Sliding velocity is the most important variable from the adhesion phenomenon point of view, which appears more frequently for low velocity values. The draining off time, which some research works consider fixes the initial lubrication conditions in friction tests, has no significant effect when a mineral oil, typically used as a prelube, is selected as a lubricant. The authors found that pressure is the most important variable for the COF value. Velocity is the determining factor for the adhesion phenomenon in friction processes under mixed lubrication.

Inaccuracies introduced by single width blood pressure cuffs

Blood pressure cuff dimensions directly affect accuracy of blood pressure measurements. For accurate blood pressure measurements, the width of the cuff must be proportional to arm circumference. A cuff that is too narrow results in falsely high blood pressure values, and a cuff that is too wide results in falsely low values. Some blood pressure standards permit a single width cuff regardless of arm circumference. The purpose of this study was to evaluate whether 12 cm single width cuffs currently permitted by the British Hypertension Society (BHS) standard are sufficiently accurate to pass the Association for the Advancement of Medical Instrumentation (AAMI), BHS, and European Society of Hypertension (ESH) International Protocol (IP1) Working Group standards for accuracy. Each of 101 subjects was tested sequentially with both a single and a proportional width cuff in random order. Auscultatory blood pressure was determined by 2 observers using a double binaural stethoscope. Accuracy was determined by comparing the resulting differences with the AAMI, BHS, and IP1 standards for accuracy. The single width blood pressure cuff failed the AAMI accuracy standards for both systolic blood pressure on large arms and diastolic blood pressure on small and large arms, and overall. The single width cuffs, also, failed the BHS accuracy standards for diastolic BP. In conclusion, these single width cuffs could result in a significant number of people being misdiagnosed and mistreated for hypertension. Therefore, to avoid 'cuff hypertension' and 'cuff hypotension', the cuff width should be proportional to arm circumference.

Fast Separation Ultra-Performance Liquid Chromatography for Determination of Pre-Column Derivative Abamectin and Ivermectin Residues in Vegetable

A new residue method for quantification of abamectin and ivermectin in vegetable is described in the article. The derivative process is devised that acylating chemical is firstly performed by N-methylimidazole (MI) and trifluoroacetic anhydride (TFAA), then which reacted with hydroxyl function of abamerctin to make fluorescence. The influence of triethylamin (TEA) is examined. Separation is resolute by a short column of 1.7 μm size and operated at high pressure values (10.000 psi). The optimal chromatographic condition and the highest sensitivity are achieved by acetonitrile: water (95: 5), 0.4 mL/min, 0.2 μL injector. The detection limits of abamectin and ivermectin are 1 μg/kg respectively.

¿Debemos modificar nuestra conducta terapéutica como consecuencia de la revisión de 2009 de la guía para el manejo de la hipertensión arterial de la ESH/ESC?

The recent publication in November 2009 of the revision of the European guidelines on hypertension management by the European Society of hypertension has aroused great interest. It has included the results of new important studies on hypertension, reinforcing the evidence on which the recommendations of the 2007 ESH/ESC guidelines were based. However, some of the recommendations that were firmly established until now are reconsidered. This dual aspect can generate some relevant doubts in clinical practice, even more so if we consider that some recommendations are opposite to other recently published guidelines. The presentation of a frequently appearing clinical case, as a hypertensive and diabetic female patient >65 years old, provides us the opportunity to analyze and interpret new recommendations, in comparison to the previous ones and to establish the best clinical action approach in the daily practice. In addition to the changes in the management of diabetic patients, some especially relevant aspects of the revised guide are updated, for example, subclinical injury of the target organ and its affect on cardiovascular risk stratification, how to manage those patients with high normal blood pressure values and other cardiovascular risk factors, the “new” blood pressure goals, as well as the objectives and the treatments under specific conditions such as the elderly population and the associated cardiovascular disease.

Melting of Peridotite to 140 Gigapascals

Interrogating physical processes that occur within the lowermost mantle is a key to understanding Earth's evolution and present-day inner composition. Among such processes, partial melting has been proposed to explain mantle regions with ultralow seismic velocities near the core-mantle boundary, but experimental validation at the appropriate temperature and pressure regimes remains challenging. Using laser-heated diamond anvil cells, we constructed the solidus curve of a natural fertile peridotite between 36 and 140 gigapascals. Melting at core-mantle boundary pressures occurs at 4180 ± 150 kelvin, which is a value that matches estimated mantle geotherms. Molten regions may therefore exist at the base of the present-day mantle. Melting phase relations and element partitioning data also show that these liquids could host many incompatible elements at the base of the mantle.

Screening of optimal pretreatment and reaction conditions for the isomerization-cracking of long paraffins over Pt/WO 3–ZrO 2 catalysts

Pretreatment and reaction conditions for the isomerization-cracking of long paraffins over commercial Pt/WO 3–ZrO 2 catalysts were screened. Optimal conditions were seeked for the production of short, high octane branched paraffins for the gasoline pool. n-C 16 was used as a model molecule. The reaction over the acidic catalyst was used to adjust the size of the molecules to the boiling range of gasolines and to add branching in order to increase the octane number of the product. These adjustments had to be done while minimizing the production of light gases and getting a stable activity level. With respect to the pretreatment it was confirmed that the best calcination temperature of the tungstate oxoanion promoted hydroxides was 800 °C. Optimality was mostly related to the activity level. The optimum temperature coincides with the appearance of small WO 3 crystallites which are thought to be center for creation of Brönsted acid sites in the presence of platinum and hydrogen. Regarding the reaction conditions, increasing temperature values augmented the conversion but also increased the cracking. Therefore optimum values were found at moderate temperature given the high reactivity of the feed. Space velocity values were analyzed with attention to the liquid C 5+ yield, the selectivity to branched isomers and the stability of the catalysts. Best yields to branched naphtha products were obtained with Pt/WO 3–ZrO 2 at WHSV = 18 h −1. The catalyst coking rate was a function of the H 2/hydrocarbon ratio. A value of 6 was enough to attain a stable conversion value on Pt/WO 3–ZrO 2. The values of liquid yield as a function of pressure displayed a volcano pattern that was rationalized in terms of a non-classical bifunctional mechanism of reaction. High pressure values increased the concentration of Brönsted acid sites and hence the activity. Too high pressures enhanced hydrocracking and decreased the liquid yield. The results indicate that in general terms Pt/WO 3–ZrO 2 at moderate reaction conditions transforms a paraffinic heavy cut into a branched isomerizate that can be added to the gasoline pool to improve the quality properties. It was however found that under some conditions the octane gain is inversely proportional to the yield of light gases indicating that a high RON isomerizate can only be got at the expense of the liquid yield.

Chemical composition, volatile components, and trace elements in the magmatic melt of the Kurama mining district, Middle Tien Shan: Evidence from the investigation of inclusions in quartz

Melt and fluid inclusions were investigated in six quartz phenocryst samples from the igneous rocks of the extrusive (ignimbrites and rhyolites) and subvolcanic (granite porphyries) facies of the Lashkerek Depression in the Kurama mining district, Middle Tien Shan. The method of inclusion homogenization was used, and glasses from more than 40 inclusions were analyzed on electron and ion microprobes. The chemical characteristics of these inclusions are typical of silicic magmatic melts. The average composition is the following (wt %): 72.4 SiO2, 0.06 TiO2, 13.3 Al2O3, 0.95 FeO, 0.03 MnO, 0.01 MgO, 0.46 CaO, 3.33 Na2O, 5.16K2O, 0.32 F, and 0.21 Cl. Potassium strongly prevails over sodium in all of the inclusions (K2O/Na2O averages 1.60). The average total of components in melt inclusions from five samples is 95.3 wt %, which indicates a possible average water content in the melt of no less than 3–4 wt %. Water contents of 2.0 wt % and 6.6 wt % were determined in melt inclusions from two samples using an ion microprobe. The analyses of ore elements in the melt inclusions revealed high contents of Sn (up to 970 ppm), Th (19–62 ppm, 47 ppm on average), and U (9–26 ppm, 18 ppm on average), but very low Eu contents (0.01 ppm). Melt inclusions of two different compositions were detected in quartz from a granite porphyry sample: silicate and chloride, the latter being more abundant. In addition to Na and K chlorides, the salt inclusions usually contain one or several anisotropic crystals and an opaque phase. The homogenization temperatures of the salt inclusions are rather high, from 680 to 820°C. In addition to silicate inclusions with homogenization temperatures of 820–850°C, a primary fluid inclusion of aqueous solution with a concentration of 3.7 wt % NaCl eq. and a very high density of 0.93 g/cm3 was found in quartz from the ignimbrite. High fluid pressure values of 6.5–8.3 kbar were calculated for the temperature of quartz formation. These estimates are comparable with values obtained by us previously for other regions of the world: 2.6–4.3 kbar for Italy, 3.7 kbar for Mongolia, 3.3–8.7 kbar for central Slovakia, and 3.3–9.6 kbar for eastern Slovakia. Unusual melt inclusions were investigated in quartz from another ignimbrite sample. In addition to a gas phase and transparent glass, they contain spherical Feoxide globules (81.2 wt % FeO) with high content of SiO2 (9.9 wt %). The globules were dissolved in the silicate melt within a narrow temperature range of 1050–1100°C, and the complete homogenization of the inclusions was observed at temperatures of 1140°C or higher. The combined analysis of the results of the investigation of these inclusions allowed us to conclude that immiscible liquids were formed in the high-temperature silicic magma with the separation of iron oxide-dominated droplets.