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Although twin culverts are often preferred for watercourse crossing, little is known about the earth pressures they experience under high embankments. Centrifuge test results have been used in this research to verify a numerical model used to evaluate culvert spacing and compressible zone geometry for twin positive projecting and induced trench box culverts. Lower pressures were calculated for twin positive projecting culverts than for a single culvert. For the induced trench case, one compressible zone spanning both culverts was the preferred geometry for culverts spaced at 0.5[B.sub.c] and 1.0[B.sub.c] (where [B.sub.c] is the culvert width), while two zones 1.2[B.sub.c] wide were found to be optimal for 1.5[B.sub.c] spacing. The twin configurations generally resulted in slightly higher vertical and lower lateral earth pressures than a single culvert configuration. The base contact pressures were 25%-76% greater than the top pressure plus dead load because of shear stresses mobilized along the sidewalls; however, they were 41%--17% lower than the pressures for positive projecting configurations. The maximum bending moments calculated for the induced trench culverts were 54%-59% lower than for the positive projecting ones. Induced trench construction therefore appears to be viable for twin box culverts, provided that frictional forces along the sidewalls are taken into account. Key words: induced trench, twin culverts, box culverts, numerical modelling, high embankments, and soil arching. Les ponceaux doubles sont souvent utilises pour les traverses de cours d'eau, malgre le fait qu'il y ait peu de connaissances sur les pressions des terres qu'ils subissent sous des remblais epais. Des resultats d'essais en centrifuge ont ete utilises dans cette etude afin de verifier un modele numerique servant a evaluer l'espacement des ponceaux et la geometrie de la zone compressible pour les ponceaux doubles a projection positive et pour les ponceaux rectangulaires avec tranchee induite. Des pressions plus faibles ont ete calculees pour les ponceaux doubles a projection positive comparativement aux ponceaux simples. Pour le cas de trancheees induites, une seule zone compressible couvrant les deux ponceaux correspond a la geomeetrie preferable pour des ponceaux espacees de 0,5[B.sub.c] et 1,0[B.sub.c] (oil [B.sub.c] est la largeur du ponceau), tandis que deux zones de 1,2[B.sub.c] de largeur representent la configuration optimale pour un espacement de 1,5[B.sub.c]. Les configurations doubles ont geeneralement des pressions des terres verticales un peu plus elevees et des pressions laterales plus faibles qu'une configuration a un seul ponceau. Les pressions de contact a la base sont plus elevees par un facteur de 25 a 76 % par rapport aux pressions sur le dessus en plus de la charge du ponceau, puisque les contraintes de cisaillement sont mobiliseees le long des murs de cote; cependant elles sont 41 a 47 % plus faibles que les pressions exerceees dans le cas de configurations a projection positive. Les moments de torsion maximums calcules pour les ponceaux avec tranchee induite sont de 54 a 59 % plus faibles que pour les configurations a projection positive. La construction de tranchees induites semble alors etre approprieee pour les ponceaux rectangulaires doubles lorsque les forces de friction le long des murs de cote sont considerees. Mots-cles: tranchee induite, ponceaux doubles, ponceaux rectangulaires, modeelisation numerique, remblais eleve, effet d'arche du sol. [Traduit par la Redaction], Introduction Twin culverts are often preferred to meet the hydraulic and environmental requirements of watercourse crossings; however, little is known about the earth pressures they experience when buried under high [...]

A new approach for real-time mass spectrometric analysis and identification of intermediates in confined, pressurized vessels is presented. The high-pressure reaction media is depressurized, mixed with a solvent, and fed directly to the atmospheric pressure electrospray ionization source of a tandem mass spectrometer. The method was applied to track product evolution for the dehydration of hydroxenin monoacetate, a commercially, important vitamin A precursor, and for the hydrogenation of 5-norbomene-2-carbonitrile with Pd/CaC[O.sub.3] as catalyst. Faster access but comparable results as by conventional offline methods were obtained in every case.

When columns packed with very fine particles are operated at high mobile phase velocities, the friction of the mobile phase percolating through the column bed generates heat. This heat dissipates along and across the column and axial and radial temperature gradients appear. The wall region of the column tends to be cooler than its center, and due to the influence of temperature on the mobile phase viscosity and on the equilibrium constant of analytes, the band velocity is not constant across the column. This radial heterogeneity of the temperature distribution across the column contributes to band broadening. This phenomenon was investigated assuming a cylindrically symmetrical column and using the general dispersion theory of Aris, which relates the height equivalent to the theoretical plate (HETP) contribution due to a radial heterogeneity of the column to the radial distribution of the linear velocities of a compound peak and to the radial distribution of its apparent dispersion coefficients in the column bed. The former is known from the temperature gradient across the column, the temperature dependencies of the mobile phase viscosity, and the retention factor of the compound. The latter is derived from the known expression of the transverse reduced HETP equation for the column. The values of the HETP calculated with the Aris model and a classical HETP equation were compared to those measured on a 2.1 x 50 mm Acqnity BEH-[C.sub.18] column, run at flow rates of 0.6, 0.95, 1.30, and 1.65 mL/min, with pure acetonitrile as the mobile phase and naphtho[2,3a]pyrene as the retained compound. These two sets of data are in generally good agreement, although the experimental values of the HETP tend to increase faster with increasing mobile phase velocity than the calculated values.

The effects of above-ambient pressure on ion mobility on resolving power, resolution, and ion current were investigated using a small, stand-alone ion mobility spectrometer (IMS). This work demonstrates the first example of ion mobility spectrometry at pressures above ambient. Ion mobility spectra of chemical warfare agent (CWA) stimulant dimethyl methylphosphonate (DMMP) and several other standard compounds are shown for super-ambient conditions. The IMS was operated at pressures from 700 to 4560 Torr. An optimal resolving power was obtained at a specific voltage as a function of pressure, with higher optimal resolving powers obtained at higher voltages, as predicted from standard IMS theory. At high pressures, however, resolving power did not increase as much as theory predicted, presumably due to ion clustering. Nevertheless, an increase in pressure was found to improve resolution in IMS. One example where high pressure improved resolution was the separation of cyclohexylamine ([K.sub.0] = 1.83) and 2-hexanone ([K.sub.0] = 1.86) (where [K.sub.0] is the reduced mobility value). The product ions of these two compounds could not be separated at ambient pressure but could be nearly baseline separated when the pressure of the buffer gas was raised to 2280 Torr. Total ion current was also examined at pressures from ambient up to 4560 Torr. Total ion current, when investigated with pressure, was found to reach a maximum, initially rising with increased pressure.

Matrix-assisted laser desorption ionization (MALDI) allows for the mass spectrometric (MS) analysis of thermally labile, non-volatile biomolecules. However, some residual analyte fragmentation typically accompanies the phase transition from the condensed to the gas phase and following plume expansion, even under optimized conditions. In-source decay (ISD) and post-source decay (PSD) MALDI MS are two techniques that make use of these phenomena and that can provide useful structural information by producing characteristic fragment ions of the analyte compounds. In orthogonal extracting time-of-flight mass spectrometry (o-TOF-MS), the pressure of the cooling gas in the ion source has a strong influence on the extent of analyte ion fragmentation. We investigated the effect of this parameter on pepride and oligosaccharide fragmentation by examining a range of pressures (from 0.05-1.8 mbar) in combination with seven different buffer gases (He, Ne, Ar, [N.sub.2], C[O.sub.2], C[H.sub.3], isobutane). Ions were generated by ultraviolet (UV) and/or by infrared (IR) MALDI. The influence of the ion extraction voltage on the analyte fragmentation also was investigated for a selected set of gas parameters. We observed that individual fragment ions exhibit characteristic fragment yield-pressure dependencies that can be classified into three groups. Type I ions resemble species that are also found in MALDI PSD MS analysis, while type II ions resemble typical ISD fragments. The yield-pressure relationship of type III ions suggests that these are the result of a combination of both processes. Comparing the yields of fragmentation for the different buffer gases reveals a correlation between their internal degrees of freedom and their collisional cooling efficiency. Changing the buffer gas pressure and/or extraction field provides an easy means to influence analyte ion fragmentation and to switch from the primary production of one type of fragment species to another. The method can therefore facilitate the structural characterization of MALDI-generated ions.

An instrument based on the Poiseuille flow principle capable of measuring solution viscosities at high pressures has been modified to observe UV-absorbent analytes in order to allow for the simultaneous measurement of analyte diffusivity. A capillary time-of-flight (CTOF) instrument was used to measure the viscosity of acetonitrile-water mixtures in all decade volume percent increments and the corresponding diffusion coefficients of small aromatic molecules in these solvent mixtures from atmospheric pressure to 2000 bar (~30 000 psi) at 25[degrees]C. The instrument works by utilizing a relatively small pressure drop (< 100 bar) across a fused-silica capillary which has both the inlet and outlet pressurized so that the average column pressure can be significantly elevated (up to 2000 bar). Measurements with this instrument agree with highpressure viscosity data collected previously using a CTOF viscometer, as well as with literature values obtained with falling-body viscometers of the Bridgman design. It has been further determined that, for the small molecules included in this study, trends in solute diffusivity with respect to pressure follow the predictions of the Stokes-Einstein equation when the solvent viscosity is corrected as a function of pressure. Because the instrument described herein determines viscosity and diffusivity independently, the effect of pressure on analyte hydrodynamic radius can also be monitored. An analysis of ultrahigh pressure liquid chromatography (UHPLC) data was performed using the pressure-corrected diffusion coefficient of hydroquinone to demonstrate the effect of this phenomenon on the analysis of chromatographic performance.

Recent studies have shown that high pressure (P) induces the metallization of the [Fe.sup.2+]--O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS) to low-spin (LS) transition of Fe in silicate and oxide phases at the deep planetary interiors. Hematite ([Fe.sub.2][O.sub.3]) is an important magnetic carrier mineral for deciphering planetary magnetism and a proxy for Fe in the planetary interiors. Here, we present synchrotron Mossbauer spectroscopy and X-ray diffraction combined with ab initio calculations for [Fe.sub.2][O.sub.3] revealing the destruction of magnetic ordering at the hematite [right arrow] [Rh.sub.2][O.sub.3]-II type (RhII) transition at 70 GPa and 300 K, and then the revival of magnetic ordering at the RhII [right arrow] postperovskite (PPv) transition after laser heating at 73 GPa. At the latter transition, at least half of [Fe.sup.3+] ions transform from LS to HS and [Fe.sub.2][O.sub.3] changes from a semiconductor to a metal. This result demonstrates that some magnetic carrier minerals may experience a complex sequence of magnetic ordering changes during impact rather than a monotonic demagnetization. Also local Fe enrichment at Earth's core-mantle boundary will lead to changes in the electronic structure and spin state of Fe in silicate PPv. If the ultra-low-velocity zones are composed of Fe-enriched silicate PPv and/or the basaltic materials are accumulated at the lowermost mantle, high electrical conductivity of these regions will play an important role for the electromagnetic coupling between the mantle and the core. spin ordering | electrical conductivity | high pressure | phase transition

A non-contact measurement method, namely an electrostatic probe, for particle charging characteristics determination is introduced in the paper. Using the probe, the charging trends of the pulverized bituminous coal in a dense phase pneumatic conveying system at low pressure were investigated for gas superficial velocities in a range of 6-10 m/s and particle concentrations in a range of 128-230 kg/[m.sup.3]. The observations indicated that increasing the coal particles concentration leads to an increase in charge level of the pulverized coal particles and then a decrease, and a peak of the charge level is experienced in the range of 150-160 kg/[m.sup.3]. The charges carried by the coal particles increase with the increase of gas superficial velocity in the pipeline, and then reach saturation values. Index Terms--Particle charging, electrostatic probe, pneumatic transport system, gas-solid two-phase flows.

We tested the hypothesis that lymphatics would exhibit myogenic constrictions and dilations to intraluminal pressure changes. Collecting lymphatic vessels were isolated from rat mesentery, cannulated, and pressurized for in vitro study. The lymphatic diameter responses to controlled intraluminal pressure steps of different magnitudes were tested in the absence and presence of the inflammatory mediator substance P, which is known to enhance lymphatic contractility. Myogenic constriction, defined as a time-dependent decrease in end-diastolic diameter over a 1-to 2-rain period following pressure elevation (after initial distension), was observed in the majority of rat mesenteric lymphatic vessels in vitro and occurred over a relatively wide pressure range (1-15 cm[H.sub.2]O). Myogenic dilation, a time-dependent rise in end-diastolic diameter following pressure reduction, was observed in over half the vessels equilibrated at a low baseline pressure. Myogenic constrictions were independent of the cardiac-like and time-dependent compensatory decline in end-systolic diameter and increase in amplitude observed in almost all vessels following pressure elevation. Substance P increased the percentage of vessels exhibiting myogenic constriction, the magnitude and rate of constriction, and the pressure range over which constriction occurred. Our results demonstrate that myogenic responses occur in collecting lymphatic vessels and suggest that the response may aid in preventing vessel overdistension during inflammation/edema. lymphatic contraction; lymphatic contractility; substance P; inflammation

The infrared reflectance of iron was studied using high-pressure synchrotron radiation methods up to 50 GPa at room temperature in a diamond anvil cell of 1000-8000 [cm.sup.-1] (1.25-10[micro]m). The magnitude of the reflectivity shows a weak pressure dependence up to the transition from the body centered cubic ([alpha]) to hexagonal close packed ([epsilon]) phase transition, where a discontinuous change in both the slope and magnitude of the reflectivity was observed. Reflectance spectra were corrected for diamond absorption and treated with a Kramers-Kronig analysis to extract the optical constants; the emissivity of iron was derived from Kirchoff's law. The pressure and wavelength dependence of the emissivity is characterized by an empirical function for 1.5-1.9 [micro]m; this wavelength range is useful for spectroradiometric temperature measurements from 1000 K up to ~2500 K. [alpha]-Fe is a nonideal emitter; however, [epsilon]-Fe behaves as an almost perfect greybody in the infrared up to the highest pressures of the measurements. Temperature measurements based on the spectroradiometry of iron samples should take into account the wavelength dependent emissivity below the [alpha]-[epsilon] phase transition at ~13 GPa. OCIS codes: 260.3060, 160.3900.

Gold as a hydrogen-sensing electrode for in situ measurement of dissolved [H.sub.2] in aqueous solutions under extreme conditions is reported. The dissolved [H.sub.2] sensor, constructed with a Au-based sensing element and coupled with a YSZ/HgO/Hg electrode, is well suited for determining dissolved [H.sub.2] concentrations of aqueous fluids at elevated temperatures and pressures. The Au electrode is made of Au wire mounted in a quartz bar, which can be pressurized and heated in the high-pressure and -temperature conditions. The Au--YSZ sensor has been tested for its potential response to the concentrations of dissolved [H.sub.2] in fluids by using a flow-through reactor at high temperatures up to 400 [degrees]C and pressures to 38 MPa. Good sensitivity and linear response between the hydrogen concentrations in the fluids and the [H.sub.2] sensor potentials are reported for hydrogen gas in the concentration range of 0.1-0.001 M [H.sub.2] in aqueous fluids at temperatures up to 340 [degrees]C and 30 MPa. Nernstian response of the cell potential to dissolved [H.sub.2] in fluids was determined at 340 [degrees]C and 30 MPa, described as follows: [DELTA]E = 0.9444 + 0. 0603 log [m.sub.H2] The experimental results indicate that the Au--YSZ/HgO/Hg cell can be used to measure the solubility of [H.sub.2] in aqueous fluid at temperatures and pressures near to the critical state of water. Thus, this type of Au hydrogen sensor could be easily used for in situ measurement of [H.sub.2] in hydrothermal fluids in a high-pressure vessel, or at midocean ridge, due to its structure of compression resistance.

Laser-induced breakdown spectroscopy (LIBS) has been identified as an analytical chemistry technique suitable for field use. We use double pulse LIBS to detect five analytes (sodium, manganese, calcium, magnesium, and potassium) that are of key importance in understanding the chemistry of deep ocean hydrothermal vent fluids as well as mixtures of vent fluids and seawater. The high pressure aqueous environment of the deep ocean is simulated in the laboratory, and the key double pulse experimental parameters (laser pulse energies, gate delay time, and interpulse delay time) are studied at pressures up to 2.76 x [10.sup.7] Pa. Each element is found to have a unique optimal set of parameters for detection. For all pressures and energies, a short ([less than or equal to]100ns) gate delay is necessary. As pressure increases, a shorter interpulse delay is needed and the double pulse conditions effectively become single pulse for both the 1.38 x [10.sup.7] Pa and the 2.76 x [10.sup.7] Pa conditions tested. Calibration curves reveal the limits of detection of the elements (5000ppmMg, 500ppmK, 500ppmCa, 1000ppmMn, and 50ppmNa) in aqueous solutions at 2.76 x [10.sup.7] Pa for the experimental setup used. When compared to our previous single pulse LIBS work for Ca, Mn, and Na, the use of double pulse LIBS for analyte detection in high pressure aqueous solutions did not improve the limits of detection. OCIS codes: 140.3440, 140.0140, 010.4450, 300.0300, 300.6365.

The ability of oceanographers to make sustained measurements of ocean processes is limited by the number of available sensors for long-term in situ analysis. In recent years, laser-induced breakdown spectroscopy (LIBS) has been identified as a viable technique to develop into an oceanic chemical sensor. We performed single pulse laser-induced breakdown spectroscopy of high pressure bulk aqueous solutions to detect three analytes (sodium, manganese, and calcium) that are of key importance in hydrothermal vent fluids, an ocean environment that would greatly benefit from the development of an oceanic LIBS sensor. The interrelationship of the key experimental parameters, pulse energy and gate delay, for a range of pressures up to 2.76 x [10.sup.7] Pa, is studied. A minimal effect of pressure on the peak intensity is observed. A short gate delay (less than 200 ns) must be used at all pressures. The ability to use a relatively low laser pulse energy (less than [approximately equal to] 60 mJ) for detection of analytes at high pressure is also established. Na, Mn, and Ca are detectable at pressures up to 2.76 x [10.sup.7] Pa at 50, 500, and 50 ppm, respectively, using an Echelle spectrometer. OCIS codes: 140.3440, 140.0140, 010.4450, 300.0300, 300.6365.

Soil nailing has been widely used in many places in the world in the last two decades because of its technical and economical advantages. The nail--soil interface shear strength is an important parameter in soil nail design. This parameter is governed by a number of factors, among which the influence of the overburden pressure (or soil depth) is the most controversial. There are differing views concerning the effect of overburden on the nail--soil interface shear strength. In order to examine the influence of the overburden pressure, a series of laboratory pullout tests on soil nails installed in compacted completely decomposed granite fill have been conducted using two pullout boxes. Numerical simulations have also been carried out and the results are compared with the pullout test data. The procedures of the pullout tests and new features of the pullout boxes used are briefly described. Changes of the vertical stress in soil close to the nail throughout the course of soil nail installation and pullout are presented and discussed in detail. It is observed from the results of this study that the installation process of soil nail induced significant vertical stress changes in soil around the soil nails, and that the soil nail pullout shear resistance is independent of the overburden pressure (or soil depth). CE Database subject headings: Soil nailing; Shear resistance; Fills; Soil compaction; Shear strength; Soil pressure.

The finite element method has been used to predict the creep rupture parameter, C*-Integral for single and double-edge cracks in eight annular rotating discs under constant angular velocity with and without internal pressure. In this study, a new dimensionless creeping crack configuration factor, Q* has been introduced. Power law creeping finite element analyses have been performed and the results are presented in the form of Q* for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations and have been determined from evidence presented in the open literature. The extensive range of Q* obtained from the analyses are then used to obtain equivalent prediction equations using a statistical multiple nonlinear regression model. The predictive equations for Q*, can also be used easily to calculate the C*-Integral values for extensive range of geometric parameters. The C*-Integral values obtained from predictive equations were also compared with those obtained from reference stress method (RSM). Finally, creep zone growth behavior was studied in the component during transient time. Keywords: Radial cracks, annular discs, constant angular velocity, internal pressure, creep zone, INTRODUCTION In spite of wide ranging applications of rotating discs, relatively very little information on the resulting stress intensity factor is available and for C*-Integral there is not any comprehensive [...]

Essential enhancement of right emission ability of europium molybdate--[Eu.sub.2][(Mo[O.sub.4]).sub.3] (EMO) crystals has been achieved by combined application of high pressure (9GPa) and heat treatment (a procedure was repeated from 3 to 25 times for different samples). Multifold increase in light emission of EMO single crystals can be achieved, without deterioration of the optical transparency of the material. Simultaneously the light emission spectra change substantially. Nature of this phenomenon is explained by the modifications of the crystal field caused by structural transformations induced by the treatments. These modifications of the crystal fields bring to increase in probability of light emission optical transitions between 4f sublevels of europium ions. Index Terms--Annealing, europium compounds, luminescence, pressure effects, scintillation detectors.

This paper first describes the current state of analysis for the response of unreinforced concrete masonry walls subjected to lateral uniform pressure. The formulation is based on the initial elastic response, the subsequent initiation of cracks and the nonlinear rocking response, and the eventual large displacement and potential collapse. The necessary equations are developed for these phases in the form of a resistance function. The paper then incorporates membrane retrofit materials to strengthen the wall's resistance to lateral pressure, and develops the necessary resistance function equations. In blast tests, membrane retrofit unreinforced masonry walls have experienced severe cracking and large displacements without collapse. This is of high interest to the Department of Defense, the protection of diplomatic facilities, and the construction industry impacted by hurricanes and other high wind events. The paper concludes with examples that demonstrate application of membrane retrofits indeed increase the resistance of the wall to lateral pressure. DOI: 10.1061/(ASCE)0887-3828(2008)22:3(131) CE Database subject headings: Walls; Masonry; Lateral pressure; Blast loads; Lateral pressure.

We have measured the equilibrium constant for the denaturation transition of the engineered fluorescein-binding lipocalin FluA as a function of pressure and temperature, taking advantage of the fact that the ligand's fluorescence is almost fully quenched when complexed with the folded protein, but reversibly reappears on denaturation. From the equilibrium constant as a function of pressure and temperature all of the involved thermodynamic parameters of protein folding, in particular the changes in entropy and volume, compressibility, thermal expansion, and specific heat, were deduced in a global fitting procedure. Assuming that these parameters are independent of temperature and pressure, we can demonstrate from the ratio of [DELTA][beta], [DELTA] [[alpha]sup.2], [DELTA] [C.sup.p] that the phase diagram of protein folding assumes an elliptic shape. Furthermore, we can show that the thermodynamic condition for such an elliptic phase diagram is related to the degree of correlation between the fluctuations of the changes in volume and enthalpy at the phase boundary. For the protein investigated this correlation is low, as generally expected for highly degenerate systems. Our study suggests that the elliptic phase diagram is a consequence of the inherent conformational disorder of proteins and that it may be viewed as the thermodynamic manifestation of the high degeneracy of conformational energies that is characteristic for this class of macromolecules. anticalin | denaturation | engineering | folding | thermodynamics

Local tissue pressure is higher in chronic pancreatitis than in the normal pancreas. We reported recently that pressure application induces synthesis of extracellular matrix (ECM) and cytokines in pancreatic stellate cells (PSCs) and that epigallocatechin gallate (EGCG), a potent antioxidant, inhibits the transformation of PSCs from quiescent to activated phenotype and ethanol-induced synthesis of ECM and cytokines in PSCs. These results suggest that oxidative stress and reactive oxygen species (ROS) are important in PSC activation. The aim of this study was to clarify the effects of ROS on activation and functions of pressure-stimulated PSCs. We used freshly isolated rat PSCs and culture-activated PSCs. Pressure was applied on rat cultured PSCs by adding compressed helium gas into a pressure-loading apparatus. PSCs were cultured with or without antioxidants (EGCG and N-acetyl cysteine) under normal or elevated pressure. Externally applied high pressure (80 mmHg) resulted in a gradual decrease of superoxide dismutase activity in PSCs and increased intracellular ROS generation as early as 30 s, reaching a peak level at 1 h. Antioxidants significantly inhibited ROS generation. Pressure increased the expression levels of a-smooth muscle actin, [[alpha].sub.1](I)-procollagen, and TGF-[beta]1 in PSCs. EGCG suppressed these alterations, abolished pressure-induced phosphorylation of p38 MAPK, and suppressed pressure-induced PSC transformation to activated phenotype. Our results indicated that ROS is a key player in pressure-induced PSC activation and ECM synthesis. Antioxidants could be potentially effective against the development of pancreatic fibrosis in patients with chronic pancreatitis. antioxidants; pancreatic fibrosis

The saturation aging tensile stiffness (SATS) test has been developed to quantify the moisture damage of a range of U.K. asphalt mixtures. In order to combine the effects of moisture and aging, the test is undertaken at an elevated temperature and pressure in the presence of moisture. This paper describes a procedure developed to investigate in detail the effects of aging, pressure, and moisture damage on results from the SATS test. An aging factor has been determined that captures the increase in stiffness modulus due to hardening that occurs at the elevated temperature and pressure. This factor ranges from 1.38 for a dry specimen to approximately 1.2 for a fully saturated specimen. A pressure factor has been determined that captures decreases in stiffness modulus due to pressure. Results show that the pressure factor is lower for the asphalt containing the basic aggregate, indicating a greater sensitivity to pressure compared to the mixture containing the acidic aggregate. The depressurization temperature in the SATS test protocol was reduced from 85 to 30[degrees]C to minimize this effect. A moisture factor was calculated, which is a measure of the moisture sensitivity of the asphalt mixture. Results showed that the moisture factor was significantly lower for the asphalt containing the acidic aggregate, indicating greater moisture sensitivity. DOI: 10.1061/(ASCE)0733-947X(2007) 133:11 (618) CE Database subject headings: Aging; Asphalts; Stiffness; Saturation; Moisture; Aggregates.

The turbomachinery component of interest in this paper, the pocket damper seal, has the dual purpose of limiting leakage and providing an additional source of damping at the seal location. The rotordynamic coefficients of these seals (primarily the direct stiffness and damping) are highly dependent on the leakage rates through the seals and the pressures in the seals' cavities. This paper presents both numerical predictions and experimentally obtained results for the leakage and the cavity pressures of pocket damper seals operating at high pressures. The seals were tested with air, at pressures up to 1000 psi (6.92 MPa), as the working fluid. Earlier flow-prediction models were modified and used to obtain theoretical reference values for both mass flow rates and pressures. Leakage and static pressure measurements on straight-through and diverging-clearance configurations of eight-bladed and twelve-bladed seals were used for code validation and for calculation of seal discharge coefficients. Higher than expected leakage rates were measured in the case of the twelve-bladed seal while the leakage rates for the eight-bladed seals were predicted with reasonable accuracy. Differences in the axial pitch lengths of the cavities and the blade profiles of the seals are used to explain the discrepancy in the case of the twelve-bladed seal The analysis code used also predicted the static cavity pressures reasonably well Tests conducted on a six-bladed pocket damper seal to further investigate the effect of blade profile supported the results of the eight-bladed and twelve-bladed seal tests and matched theoretical predictions with satisfactory accuracy. [DOI: 10.1115/1.2720871] Keywords: pocket damper seal leakage, cavity pressure, rotordynamics, turbomachinery

The influence of the pressure ratio and the diaphragm location on the flow from open-ended shock tubes is investigated. In contrast to previous studies, in which attention was focused on the discharge of the shock wave from the shock tube, we consider also the influence of the contact discontinuity and the expansion fan. It is found that if the pressure ratio is large enough to lead to supersonic flow behind the contact discontinuity, the flow at the open end relaxes from the conditions behind the contact discontinuity to sonic conditions once the tail of the expansion fan arrives at the open end. Theory indicates that the time scale over which the flow relaxes to sonic conditions is nearly independent of the initial Mach number. Also, the time scale is much longer than that required by the acceleration of subsonic conditions behind the contact discontinuity to sonic conditions. The relaxation process is shown to influence the evolution of the Mach-disk shock, the barrel shock, and the reflected shock wave in an underexpanded jet.

Methane hydrate, equilibrated at P, T conditions within the hydrate stability field, was rapidly depressurized to 1.0 or 2.0 MPa and maintained at isobaric conditions outside its stability field, while the extent and rate of hydrate dissociation was measured at fixed, externally maintained temperatures between 250 and 288 K. The dissociation rate decreases with increasing pressure at a given temperature. Dissociation rates at 1.0 MPa parallel the complex, reproducible T-dependence previously observed between 250 and 272 K at 0.1 MPa. The lowest rates were observed near 268 K, such that >50% of the sample can persist for more than two weeks at 0.1 MPa to more than a month at 1 and 2 MPa. Varying the pressure stepwise in a single experiment increased or decreased the dissociation rate in proportion to the rates observed in the isobaric experiments, similar to the rate reversibility previously observed with stepwise changes in temperature at 0.1 MPa. At fixed P, T conditions, the rate of methane hydrate dissociation decreases monotonically with time, never achieving a steady rate. The relationship between time (t) and the extent of hydrate dissociation is empirically described by: Evolved gas (%) = A x [t.sup.B] (l) where the pre-exponential term A ranges from 0 to 16% [S.sup.-B] and the exponent B is generally < 1. Based on fits of the dissociation results to Equation 1 for the full range of temperatures (204 to 289 K) and pressures (0.1 to 2.0 MPa) investigated, the derived parameters can be used to predict the methane evolution curves for pure, porous methane hydrate to within [+ or -] 5%. The effects of sample porosity and the presence of quartz sand and seawater on methane hydrate dissociation are also described using Equation 1.

The small-signal gain coefficient and the saturation intensity of a copper vapor laser have been measured for both 510.6- and 578.2-nm transitions through the implementation of a discharge driven oscillator-amplifier configuration. Pressure dependence of the gain and saturation property of the laser has been investigated. OCIS codes: 140.0140, 140.7300, 230.4910, 140.3280, 020.2070.

The local distributions of void fraction, interfacial frequency, and velocity have been measured in annular flow of R-134a through a wall-heated, high aspect ratio duct. High aspect ratio ducts provide superior optical access to tubes or irregular geometries. This work expands upon earlier experiments conducted with adiabatic flows in the same test section. Use of thin, transparent heater films on quartz windows provided sufficient electrical power capacity to produce the full range of two-phase conditions of interest. With wall vapor generation, the system pressure was varied from 0.9 to 2.4 MPa, thus allowing the investigation of flows with liquid-to-vapor density ratios covering the range of about 7 to 27, far less than studied in air-water and similar systems. There is evidence that for a given cross-sectional average void fraction, the local phase distributions can be different depending on whether the vapor phase is generated at the wall or upstream of the test section inlet. In wall-heated flows, local void fraction profiles measured across both the wide and narrow test section dimensions illustrate the profound effect that pressure has on the local flow structure; notably, increasing pressure appears to thin the wall-bounded liquid films and redistribute liquid toward the edges of the test section. This general trend is also manifested in the distributions of mean droplet diameter and interfacial area density, which are inferred from local measurements of void fraction, droplet frequency and velocity. At high pressure, the interfacial area density is increased due to the significant enhancement in droplet concentration. [DOI: 10.1115/1.1524583]

A cantilever skew plate was exposed to aerodynamic forces with a velocity exceeding its critical value and also simultaneously subjected to by an in-plane harmonic force to study its dynamic stability. When the aerodynamic pressure was increased beyond its critical value, the plate remained stable because of the effect of the in-plane harmonic force at specific amplitude and exciting frequencies. Therefore, the exciting frequency and amplitude of the in-plane harmonic force are both proved to be stabilizing. The increase in the aerodynamic pressure is a destabilizing factor. A plate with a larger skew angle is also found to be more stable.

Electrical pulses in a concentration gradient of KCl, in the absence of any external pressure, voltage or current, were spontaneously produced by a membrane derived from a tri-block copolypeptide containing poly (L-leucine) as an inner portion and poly (L-glutamic acid) as outer portions. Hysteresis was observed and the current-voltage curves of the membrane were sigmoidal at reduced KCl concentrations, indicating that the membrane can possess two distinct resistance states that are connected to alpha-helix and random-coil conformations of the poly (L-glutamic acid) chain.

The impact of endothelium-derived nitric oxide (EDNO) blockade on pressure regulated release renin (RR) was investigated in catheter-implanted foxhounds. Renal blood flow (RBF) and renal artery pressure (RAP) were measured after administration of NG-nitro-L-arginine methyl ester (L-NAME), an EDNO inhibitor. Increase in RAP alone was observed. Lessening of heart rate, RBF and RR occurred phase-by-phase, and lowering of RAP caused alterations in RR due to L-NAME pressure. Inhibition of RR by L-NAME frequently occurred at low pressures.

The Oksfjord area in the Caledonides of Norway records mineral thermobarometry of the increase in pressure during post-peak cooling. The numerous independently calibrated geothermometers, geobarometers and mineral equilibria quantify the three metamorphic stages. Fluid inclusions in cordierite, garnet and quartz are of three kinds, CO2 inclusion, N2 inclusions and mixed CO2-N2 inclusions. The composition and density characteristics of the inclusions present in the granulite facies rocks are compatible with the P-T conditions derived from geothermobarometry and mineral assemblages. During the metamorphic evolution from intermediate-P granule facies to the high-P granulite facies, the fluid inclusions are equilibrated according to density.

A study was conducted on activity-composition relationships in the Fe-Pt system at 1300 and 1400 degrees celcius (C), 1 atmosphere and 20 kilobars. In the alloy, the Fe activity coefficient was found to be best represented by log gamma-Fe = (1 - X(sub Fe))squared(B + C(4X(sub Fe) - 1)), where B = -3.579 and C = -0.151 at 1400 degrees C and B = -4.202 and C = -0.323 at 1300 C. In alloys with poor Fe, Fe partial molar volume was found to have a significant negative deviation from ideal values. In addition, as Fe content increased, volume composition relationships exhibited a positive deviation and will likely reach ideality.

Pressure and temperature EPR measurements conducted for a dichlorobis (1-phenyl-3,5-dimethyl pyrazole)copper (II) crystal elucidates the functional relation between exchange coupling and temperature as a consequence of the influence of pressure. The response of exchange coupling in this crystal to an increase in pressure is identical to the effect of a decrease in temperature on the exchange coupling, with the pressure effect dominating the temperature influence. The coupling constant J behaves as a function of temperature and decreases with decrease in temperature upon the application of a pressure to the crystal. Temperature and pressure also influence the Laude factor or gz-factor and the line width. Exchange coupling is ferromagnetic in the absence of pressure and antiferromagnetic when crystal is subjected to pressure.

The scaling of O2 ((super 1)delta) yields with specific energy deposition in He/O2 mixtures in flowing radio frequency (rf) was investigated. It was found that O2 ((super 1)delta) yield increased nearly linearly with specific energy deposition in O2 molecules upto a few eV per molecule.

N incorporation behaviors are investigated using a series of samples grown at different growth rates, As4/Ga ratios, and nitrogen fluxes within a growth temperature range from 420 to 560 degree C. The incorporation behavior of N in GaAsN grown at higher growth rates are found to be very different from that grown at lower growth rates.

Results reveal that the homotrimeric vesicular stomatitis virus G protein undergoes pressure-induced conformational change that preserves the fusion properties of the virus as seen in an increase in light scattering. This represents a 'fusion-intermediate state' and contain minor changes in secondary structure.

Raman spectroscopy, x-ray single crystal diffractometry, and scanning electron microscopy are used to study the graphitization of {100} and {111} faces of diamond crystals at high pressures and various temperatures. It was seen that the disoriented crystals grow as a result of diamond-graphite recrystallization through the liquid metal, whereas the oriented growth of graphite takes place at the surfaces of cracks, propagating from the inclusions in the {111} planes.

The results of an experimental and theoretical study on the feasibility of a barium low pressure discharge as a potential new light source are reported. The predicted efficacies of up to 100 lm/W were considerably higher than the measured values and the best positive column efficacy achieved was 50 lm/W in a sealed yttria lined quartz tube with 5 Torr argon operating at 400 mA at 760 degrees C.

Laminar dc plasma jets are attractive for precisely controlled plasma-material processing. The design of a novel non-transferred plasma torch enabled the switching between turbulent and laminar plasma flows by simply changing the plasma generation parameters. Images of the plasma flows generated at different conditions are presented. Index Terms--DC plasma, high speed video camera, plasma stability.

Streamers appear in gases, liquids, and solids due to impact ionization in high electric fields near streamer tips. Dynamically adaptive mesh enables high resolution of sharp streamer fronts with a large dynamic range and a minimum number of computational cells. We present results of computational experiments utilizing dynamically adaptive Cartesian mesh for multiscale resolution of streamers near curved electrodes in 2-D and 3-D geometries. Index Terms--Adaptive Cartesian mesh, high pressure gas breakdown, streamer simulation.

It is requested that steam generator tubes with defects exceeding 40% of wall thickness in depth should be plugged to sustain all postulated loads with appropriate margin. This critical defect size has been determined based on a concept of plastic instability, however, which is known to be too conservative for some locations and types of defects. The application of this concept may even cause premature retirement of steam generator tubes. In reality, a reliable structural integrity estimation for steam generator tubes containing a defect has received increasing attention. Although several guidelines have been developed and used for assessing defect containing tubes, most of these guidelines are focused on stress corrosion cracking or wall-thinning phenomena. Because some of steam generator tubes fail due to fretting and so on, specific integrity estimation schemes for relevant defects are required. In this paper, more than a hundred three-dimensional finite element analyses of steam generator tubes under internal pressure condition are carried out to simulate the failure behavior of steam generator tubes with specific defect configurations: elliptical wear-type, tapered wedge-type, and flat wear-type defects. After investigating the effect of key parameters such as defect depth, defect length, and wrap or tapered angle on equivalent stress across the ligament thickness, burst pressure estimation equations are proposed in relation to material strengths. Predicted burst pressures agreeded well with the corresponding experimental data, so the proposed equations can be used to assess the structural integrity of steam generator tubes with wear-type defects. [DOI: 10.1115/1.2937741] Keywords: burst pressure, plastic limit pressure, steam generator tube, wear-type defects