Demonstrating the Impact of a Distributed Leadership Approach in Higher Education

ERIC Educational Resources Information Center

Jones, Sandra; Harvey, Marina; Hamilton, Jillian; Bevacqua, John; Egea, Kathy; McKenzie, Jo

2017-01-01

Higher education is under pressure to advance from a singular focus on assessment of outputs (measurements) to encompass the impact (influence) of initiatives across all aspects of academic endeavour (research, learning and teaching, and leadership). This paper focuses on the implications of this shift for leadership in higher education.…

Buckling of pressure-loaded, long, shear deformable, cylindrical laminated shells

NASA Astrophysics Data System (ADS)

Anastasiadis, John S.; Simitses, George J.

A higher-order shell theory was developed (kinematic relations, constitutive relations, equilibrium equations and boundary conditions), which includes initial geometric imperfections and transverse shear effects for a laminated cylindrical shell under the action of pressure, axial compression and in-plane shear. Through the perturbation technique, buckling equations are derived for the corresponding 'perfect geometry' symmetric laminated configuration. Critical pressures are computed for very long cylinders for several stacking sequences, several radius-to-total-thickness ratios, three lamina materials (boron/epoxy, graphite/epoxy, and Kevlar/epoxy), and three shell theories: classical, first-order shear deformable and higher- (third-)order shear deformable. The results provide valuable information concerning the applicability (accurate prediction of buckling pressures) of the various shell theories.

MESOSCALE MODELING OF DEFLAGRATION-INDUCED DECONSOLIDATION IN POLYMER-BONDED EXPLOSIVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Springer, H K; Glascoe, E A; Reaugh, J E

Initially undamaged polymer-bonded explosives can transition from conductive burning to more violent convective burning via rapid deconsolidation at higher pressures. The pressure-dependent infiltration of cracks and pores, i.e., damage, by product gases at the burn-front is a key step in the transition to convective burning. However, the relative influence of pre-existing damage and the evolution of deflagration-induced damage during the transition to convective burning is not well understood. The objective of this study is to investigate the role of microstructure and initial pressurization on deconsolidation. We performed simulations using the multi-physics hydrocode, ALE3D. HMX-Viton A served as our model explosive.more » A Prout-Tompkins chemical kinetic model, Vielle's Law pressure-dependent burning, Gruneisen equation-of-state, and simplified strength model were used for the HMX. The propensity for deconsolidation increased with increasing defect size and decreasing initial pressurization, as measured by the increase in burning surface area. These studies are important because they enable the development of continuum-scale damage models and the design of inherently safer explosives.« less

Germination and growth of wheat in simulated Martian atmospheres

NASA Technical Reports Server (NTRS)

Schwartzkopf, Steven H.; Mancinelli, Rocco L.

1991-01-01

One design for a manned Mars base incorporates a bioregenerative life support system based upon growing higher plants at a low atmospheric pressure in a greenhouse on the Martian surface. To determine the concept's feasibility, the germination and initial growth of wheat (Triticum aestivum) was evaluated at low atmospheric pressures in simulated Martian atmosphere (SMA) and in SMA supplemented with oxygen. Total atmospheric pressures ranged from 10 to 1013 mb. No seeds germinated in pure SMA, regardless of atmospheric pressure. In SMA plus oxygen at 60 mb total pressure, germination and growth occurred but were lower than in the earth atmosphere controls.

Shock experiments on maskelynite-bearing anorthosite

NASA Technical Reports Server (NTRS)

Lambert, P.; Grieve, R. A. F.

1984-01-01

A series of shock recovery experiments over 9.9-60.4 GPa have been carried out on naturally shocked anorthosite from the Mistastin impact structure in Labrador consisting primarily of diaplectic plagioclase glass or maskelynite, An(50), and pyroxene. Petrographic observations of the experimental products indicate that the component minerals and diaplectic glasses generally retained their initial character throughout, the only exception being the increase in fracturing which occurred in the 9.9 GPa shot. Reshocking at pressures higher than the initial shock tends to lower the refractive index of maskelynite. The increase in refractive index of maskelynite reshocked to pressures lower than the initial pressure is interpreted as due to shock densification of the diaplectic glass above the Hugoniot elastic limit and below the mixed phase regime. The data suggest that the low-high-low density transition of maskelynite occurs about 8 GPa below that of the crystal of corresponding composition.

On the mechanical stability of the body-centered cubic phase and the emergence of a metastable cI16 phase in classical hard sphere solids

NASA Astrophysics Data System (ADS)

Warshavsky, Vadim B.; Ford, David M.; Monson, Peter A.

2018-01-01

The stability of the body-centered cubic (bcc) solid phase of classical hard spheres is of intrinsic interest and is also relevant to the development of perturbation theories for bcc solids of other model systems. Using canonical ensemble Monte Carlo, we simulated systems initialized in a perfect bcc lattice at various densities in the solid region. We observed that the systems rapidly evolved into one of four structures that then persisted for the duration of the simulation. Remarkably, one of these structures was identified as cI16, a cubic crystalline structure with 16 particles in the unit cell, which has recently been observed experimentally in lithium and sodium solids at high pressures. The other three structures do not exhibit crystalline order but are characterized by common patterns in the radial distribution function and bond-orientational order parameter distribution; we refer to them as bcc-di, with i ranging from 1 to 3. We found similar outcomes when employing any of the three single occupancy cell (SOC) restrictions commonly used in the literature. We also ran long constant-pressure simulations with box shape fluctuations initiated from bcc and cI16 initial configurations. At lower pressures, all the systems evolved to defective face-centered cubic (fcc) or hexagonal close-packed (hcp) structures. At higher pressures, most of the systems initiated as bcc evolved to cI16 with some evolving to defective fcc/hcp. High pressure systems initiated from cI16 remained in that structure. We computed the chemical potential of cI16 using the Einstein crystal reference method and found that it is higher than that of fcc by ˜0.5kT-2.5kT over the pressure range studied, with the difference increasing with pressure. We find that the undistorted bcc solid, even with constant-volume and SOC restrictions applied, is so mechanically unstable that it is unsuitable for consideration as a metastable phase or as a reference system for studying bcc phases of other systems. On the other hand, cI16 is a mechanically stable structure that can spontaneously emerge from a bcc starting point but it is thermodynamically metastable relative to fcc or hcp.

The Nature of Teacher Leadership in a Boston Pilot School

ERIC Educational Resources Information Center

Chesson, Laura S.

2011-01-01

As the pressure on schools to meet higher and higher expectations with less and less resources increases, educators seek to explore school models which are centered on reforms that increased the likelihood of meeting this challenge. One reform initiative which has received much attention is the utilization of teacher leadership to improve school…

Pressure Injury Knowledge in Critical Care Nurses.

PubMed

Miller, Donna M; Neelon, Lisa; Kish-Smith, Kathleen; Whitney, Laura; Burant, Christopher J

The purpose of this study was to identify pressure injury knowledge in critical care nurses related to prevention and staging following multimodal education initiatives. Postintervention descriptive study. The sample comprised 32 RNs employed in medical intensive care/coronary intensive care or surgical intensive care units. The study setting was a 237-bed Veterans Affairs acute care hospital in the Midwestern United States. Critical care RNs were asked to participate in this project over a 3-week period following a multimodal 2-year education initiative. Nurses completed the paper version of the 72-item Pieper-Zulkowski Pressure Ulcer Knowledge Test (PZ-PUKT) to determine pressure injury knowledge level. Calculated mean cumulative scores and subscores for items related to prevention and staging, respectively. Pearson correlations were used to examine associations between nursing staff characteristics and the PZ-PUKT prevention and staging scores. The cumulative score on the PZ-PUKT was 51.66 (72%); nurses with 5 to 10 years' experience had a higher mean score than nurses with experiences of 20 years or more (mean ± SD = 54.25 ± 4.37 vs 49.5 ± 7.12), but the difference was not statistically significant. Nurses scored higher on the staging system-related items as compared to the prevention-related items (81% vs 70%). Nurses achieved higher staging subscale scores if they were younger (r =-0.41, P < .05), had less experience (r =-0.43, P < .05), and if they worked in the medical intensive care unit (r = 0.37, P < .05). Study findings indicate gaps in knowledge related to pressure injury practice; participants had greater knowledge of staging rather than prevention. Cumulative and subscale findings can be used to direct educational efforts needed to improve and maintain an effective pressure injury prevention program.

Measurements of Free-Space Oscillating Pressures Near Propellers at Flight Mach Numbers to 0.72

NASA Technical Reports Server (NTRS)

Kurbjun, Max C; Vogeley, Arthur W

1958-01-01

In the course of a short flight program initiated to check the theory of Garrick and Watkins (NACA rep. 1198), a series of measurements at three stations were made of the oscillating pressures near a tapered-blade plan-form propeller and rectangular-blade plan form propeller at flight Mach numbers up to 0.72. In contradiction to the results for the propeller studied in NACA rep. 1198, the oscillating pressures in the plane ahead of the propeller were found to be higher than those immediately behind the propeller. Factors such as variation in torque and thrust distribution, since the blades of the present investigation were operating above their design forward speed, may account for this contradiction. The effect of blade plan form shows that a tapered-blade plan-form propeller will produce lower sound-pressure levels than a rectangular-blade plan-form propeller for the low blade-passage harmonics (the frequencies where structural considerations are important) and produce higher sound-pressure levels for the higher blade-passage harmonics (frequencies where passenger comfort is important).

Improved hydrostatic pressure sample injection by tilting the microchip towards the disposable miniaturized CE device.

PubMed

Wang, Wei; Zhou, Fang; Zhao, Liang; Zhang, Jian-Rong; Zhu, Jun-Jie

2008-02-01

A simple method of hydrostatic pressure sample injection towards a disposable microchip CE device was developed. The liquid level in the sample reservoir was higher than that in the sample waste reservoir (SWR) by tilting microchip and hydrostatic pressure was generated, the sample was driven to pass through injection channel into SWR. After sample loading, the microchip was levelled for separation under applied high separation voltage. Effects of tilted angle, initial liquid height and injection duration on electrophoresis were investigated. With enough injection duration, the injection result was little affected by tilted angle and initial liquid heights in the reservoirs. Injection duration for obtaining a stable sample plug was mainly dependent on the tilted angle rather than the initial height of liquid. Experimental results were consistent with theoretical prediction. Fluorescence observation and electrochemical detection of dopamine and catechol were employed to verify the feasibility of tilted microchip hydrostatic pressure injection. Good reproducibility of this injection method was obtained. Because the instrumentation was simplified and no additional hardware was needed in this technology, the proposed method would be potentially useful in disposable devices.

The Pressure-Induced Polymorphic Transformations in Fluconazole.

PubMed

Gorkovenko, Ekaterina A; Kichanov, Sergey E; Kozlenko, Denis P; Belushkin, Alexandr V; Wąsicki, Jan; Nawrocik, Wojciech; Mielcarek, Jadwiga; Dubrovinsky, Leonid S; Lathe, Christian; Savenko, Boris N

2015-12-01

The structural properties and Raman spectra of fluconazole have been studied by means of X-ray diffraction and Raman spectroscopy at pressures up to 2.5 and 5.5 GPa, respectively. At a pressure of 0.8 GPa, a polymorphic phase transition from the initial form I to a new triclinic form VIII has been observed. At higher pressure of P = 3.2 GPa, possible transformation into another new polymorphic form IX has been detected. The unit cell parameters and volumes, and vibration modes as functions of pressure have been obtained for the different forms of fluconazole. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Surface instabilities in shock loaded granular media

NASA Astrophysics Data System (ADS)

Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

2017-12-01

The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to initiate instabilities in a range of situations involving the explosive dispersion of particles.

A pressure ulcer and fall rate quality composite index for acute care units: A measure development study.

PubMed

Boyle, Diane K; Jayawardhana, Ananda; Burman, Mary E; Dunton, Nancy E; Staggs, Vincent S; Bergquist-Beringer, Sandra; Gajewski, Byron J

2016-11-01

Composite indices are single measures that combine the strengths of two or more individual measures and provide broader, easy-to-use measures for evaluation of provider performance and comparisons across units and hospitals to support quality improvement. The study objective was to develop a unit-level inpatient composite nursing care quality performance index-the Pressure Ulcer and Fall Rate Quality Composite Index. Two-phase measure development study. 5144 patient care units in 857 United States hospitals participating in the National Database of Nursing Quality Indictors ® during the year 2013. The Pressure Ulcer and Fall Rate Quality Composite Index was developed in two phases. In Phase 1 the formula was generated using a utility function and generalized penalty analysis. Experts with experience in healthcare quality measurement provided the point of indicator equivalence. In Phase 2 initial validity evidence was gathered based on hypothesized relationships between the Pressure Ulcer and Fall Rate Quality Composite Index and other variables using two-level (unit, hospital) hierarchical linear mixed modeling. The Pressure Ulcer and Fall Rate Quality Composite Index=100-PUR-FR, where PUR is pressure ulcer rate and FR is total fall rate. Higher scores indicate better quality. Bland-Altman plots demonstrated agreement between pairs of experts and provided evidence for inter-rater reliability of the formula. The validation process demonstrated that higher registered nurse skill mix, higher percent of registered nurses with a baccalaureate in nursing or higher degree, higher percent of registered nurses with national specialty certification, and lower percent of hours supplied by agency staff were significantly associated with higher Pressure Ulcer and Fall Rate Quality Composite Index scores. Higher percentages of unit patients at risk for a hospital-acquired pressure ulcer and higher unit rates of physical restraint use were not associated with higher Pressure Ulcer and Fall Rate Quality Composite Index scores. The Pressure Ulcer and Fall Rate Quality Composite Index is a step toward providing a more holistic perspective of unit level nursing quality than individual measures and may help nurses nursing administrators obtain a broader view of which patient care units are the higher and lower performers. Further study is needed to examine the usability of the Pressure Ulcer and Fall Rate Quality Composite Index. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

A PRESSURE ULCER AND FALL RATE QUALITY COMPOSITE INDEX FOR ACUTE CARE UNITS: A MEASURE DEVELOPMENT STUDY

PubMed Central

Jayawardhana, Ananda; Burman, Mary E.; Dunton, Nancy E.; Staggs, Vincent S.; Bergquist-Beringer, Sandra; Gajewski, Byron J.

2016-01-01

Background Composite indices are single measures that combine the strengths of two or more individual measures and provide broader, easy-to-use measures for evaluation of provider performance and comparisons across units and hospitals to support quality improvement. Objective The study objective was to develop a unit-level inpatient composite nursing care quality performance index – the Pressure Ulcer and Fall Rate Quality Composite Index. Design Two-phase measure development study. Settings 5,144 patient care units in 857 United States hospitals participating in the National Database of Nursing Quality Indictors® during the year 2013. Methods The Pressure Ulcer and Fall Rate Quality Composite Index was developed in two phases. In Phase 1 the formula was generated using a utility function and generalized penalty analysis. Experts with experience in healthcare quality measurement provided the point of indicator equivalence. In Phase 2 initial validity evidence was gathered based on hypothesized relationships between the Pressure Ulcer and Fall Rate Quality Composite Index and other variables using two-level (unit, hospital) hierarchical linear mixed modeling. Results The Pressure Ulcer and Fall Rate Quality Composite Index = 100 − PUR − FR, where PUR is pressure ulcer rate and FR is total fall rate. Higher scores indicate better quality. Bland-Altman plots demonstrated agreement between pairs of experts and provided evidence for inter-rater reliability of the formula. The validation process demonstrated that higher registered nurse skill mix, higher percent of registered nurses with a baccalaureate in nursing or higher degree, higher percent of registered nurses with national specialty certification, and lower percent of hours supplied by agency staff were significantly associated with higher Pressure Ulcer and Fall Rate Quality Composite Index scores. Higher percentages of unit patients at risk for a hospital-acquired pressure ulcer and higher unit rates of physical restraint use were not associated with higher Pressure Ulcer and Fall Rate Quality Composite Index scores. Conclusions The Pressure Ulcer and Fall Rate Quality Composite Index is a step toward providing a more holistic perspective of unit level nursing quality than individual measures and may help nurses nursing administrators obtain a broader view of which patient care units are the higher and lower performers. Further study is needed to examine the usability of the Pressure Ulcer and Fall Rate Quality Composite Index. PMID:27607602

Numerical research on the lateral global buckling characteristics of a high temperature and pressure pipeline with two initial imperfections

PubMed Central

Liu, Wenbin; Liu, Aimin

2018-01-01

With the exploitation of offshore oil and gas gradually moving to deep water, higher temperature differences and pressure differences are applied to the pipeline system, making the global buckling of the pipeline more serious. For unburied deep-water pipelines, the lateral buckling is the major buckling form. The initial imperfections widely exist in the pipeline system due to manufacture defects or the influence of uneven seabed, and the distribution and geometry features of initial imperfections are random. They can be divided into two kinds based on shape: single-arch imperfections and double-arch imperfections. This paper analyzed the global buckling process of a pipeline with 2 initial imperfections by using a numerical simulation method and revealed how the ratio of the initial imperfection’s space length to the imperfection’s wavelength and the combination of imperfections affects the buckling process. The results show that a pipeline with 2 initial imperfections may suffer the superposition of global buckling. The growth ratios of buckling displacement, axial force and bending moment in the superposition zone are several times larger than no buckling superposition pipeline. The ratio of the initial imperfection’s space length to the imperfection’s wavelength decides whether a pipeline suffers buckling superposition. The potential failure point of pipeline exhibiting buckling superposition is as same as the no buckling superposition pipeline, but the failure risk of pipeline exhibiting buckling superposition is much higher. The shape and direction of two nearby imperfections also affects the failure risk of pipeline exhibiting global buckling superposition. The failure risk of pipeline with two double-arch imperfections is higher than pipeline with two single-arch imperfections. PMID:29554123

Innovation Diffusion Model in Higher Education: Case Study of E-Learning Diffusion

ERIC Educational Resources Information Center

Buc, Sanjana; Divjak, Blaženka

2015-01-01

The diffusion of innovation (DOI) is critical for any organization and especially nowadays for higher education institutions (HEIs) in the light of vast pressure of emerging educational technologies as well as of the demand of economy and society. DOI takes into account the initial and the implementation phase. The conceptual model of DOI in…

Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen / Liquid Methane Main Engine

NASA Technical Reports Server (NTRS)

Melcher, John C.; Morehead, Robert L.

2014-01-01

The project Morpheus liquid oxygen (LOX) / liquid methane (LCH4) main engine is a Johnson Space Center (JSC) designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. The engine met or exceeded all performance requirements without experiencing any in- ight failures, but the engine exhibited acoustic-coupled combustion instabilities during sea-level ground-based testing. First tangential (1T), rst radial (1R), 1T1R, and higher order modes were triggered by conditions during the Morpheus vehicle derived low chamber pressure startup sequence. The instability was never observed to initiate during mainstage, even at low power levels. Ground-interaction acoustics aggravated the instability in vehicle tests. Analysis of more than 200 hot re tests on the Morpheus vehicle and Stennis Space Center (SSC) test stand showed a relationship between ignition stability and injector/chamber pressure. The instability had the distinct characteristic of initiating at high relative injection pressure drop at low chamber pressure during the start sequence. Data analysis suggests that the two-phase density during engine start results in a high injection velocity, possibly triggering the instabilities predicted by the Hewitt stability curves. Engine ignition instability was successfully mitigated via a higher-chamber pressure start sequence (e.g., 50% power level vs 30%) and operational propellant start temperature limits that maintained \\cold LOX" and \\warm methane" at the engine inlet. The main engine successfully demonstrated 4:1 throttling without chugging during mainstage, but chug instabilities were observed during some engine shutdown sequences at low injector pressure drop, especially during vehicle landing.

A Comparison of Young Star Properties with Local Galactic Environment for LEGUS/LITTLE THINGS Dwarf Irregular Galaxies

NASA Astrophysics Data System (ADS)

Hunter, Deidre A.; Adamo, Angela; Elmegreen, Bruce G.; Gallardo, Samavarti; Lee, Janice C.; Cook, David O.; Thilker, David; Kayitesi, Bridget; Kim, Hwihyun; Kahre, Lauren; Ubeda, Leonardo; Bright, Stacey N.; Ryon, Jenna E.; Calzetti, Daniela; Tosi, Monica; Grasha, Kathryn; Messa, Matteo; Fumagalli, Michele; Dale, Daniel A.; Sabbi, Elena; Cignoni, Michele; Smith, Linda J.; Gouliermis, Dimitrios M.; Grebel, Eva K.; Aloisi, Alessandra; Whitmore, Bradley C.; Chandar, Rupali; Johnson, Kelsey E.

2018-07-01

We have explored the role environmental factors play in determining characteristics of young stellar objects in nearby dwarf irregular and blue compact dwarf galaxies. Star clusters are characterized by concentrations, masses, and formation rates; OB associations by mass and mass surface density; O stars by their numbers and near-ultraviolet absolute magnitudes; and H II regions by Hα surface brightnesses. These characteristics are compared to surrounding galactic pressure, stellar mass density, H I surface density, and star formation rate (SFR) surface density. We find no trend of cluster characteristics with environmental properties, implying that larger-scale effects are more important in determining cluster characteristics or that rapid dynamical evolution erases any memory of the initial conditions. On the other hand, the most massive OB associations are found at higher pressure and H I surface density, and there is a trend of higher H II region Hα surface brightness with higher pressure, suggesting that a higher concentration of massive stars and gas is found preferentially in regions of higher pressure. At low pressures we find massive stars but not bound clusters and OB associations. We do not find evidence for an increase of cluster formation efficiency as a function of SFR density. However, there is an increase in the ratio of the number of clusters to the number of O stars with increasing pressure, perhaps reflecting an increase in clustering properties with SFR.

Temperature and initial curvature effects in low-density panel flutter

NASA Technical Reports Server (NTRS)

Resende, Hugo B.

1992-01-01

The panel flutter phenomenon is studied assuming free-molecule flow. This kind of analysis is relevant in the case of hypersonic flight vehicles traveling at high altitudes, especially in the leeward portion of the vehicle. In these conditions the aerodynamic shear can be expected to be considerably larger than the pressure at a given point, so that the effects of such a loading are incorporated into the structural model. Both the pressure and shear loadings are functions of the panel temperature, which can lead to great variations on the location of the stability boundaries for parametric studies. Different locations can, however, be 'collapsed' onto one another by using as ordinate an appropriately normalized dynamic pressure parameter. This procedure works better for higher values of the panel temperature for a fixed undisturbed flow temperature. Finally, the behavior of the system is studied when the panel has some initial curvature. This leads to the conclusion that it may be unrealistic to try to distinguish between a parabolic or sinusoidal initial shape.

Plasma Assisted Combustion

DTIC Science & Technology

2007-02-28

these pulses was uniform. Dependence of the energy contribution on pressure is showed in the Figure 3.5. It is clearly seen that for the pressure of...note that water–ions kinetics is more important than kinetics of initial substances– ions because water has higher proton affinity energy than... pulsed discharge. 4.3.2 Kinetic model To calculate the densities of active particles, one has to determine electron energy dis- tribution function (EEDF

Evaluation program for secondary spacecraft cells. Initial evaluation tests of General Electric Company standard and teflonated negative electrode 20.0 ampere-hour, nickel-cadmium spacecraft cells with auxiliary electrodes

NASA Technical Reports Server (NTRS)

1974-01-01

The standard plate cells exhibited higher average end-of-charge (EOC) voltages than the cells with teflonated negative plates; they also delivered a higher capacity output in ampere hours following these charges. All the cells reached a pressure of 20 psia before reaching the voltage limit of 1.550 volts during the pressure versus capacity test. The average ampere hours in and voltages at this pressure were 33.6 and 1.505 volts respectively for the teflonated negative plate cells and 35.5 and 1.523 volts for the standard plate cells. All cells exhibited pressure decay in the range of 1 to 7 psia during the last 30 minutes of the 1-hour open circuit stand. Average capacity out for the teflonated and standard negative plate cells was 29.4 and 29.9 ampere hours respectively.

Blueberry polyphenol oxidase: Characterization and the kinetics of thermal and high pressure activation and inactivation.

PubMed

Terefe, Netsanet Shiferaw; Delon, Antoine; Buckow, Roman; Versteeg, Cornelis

2015-12-01

Partially purified blueberry polyphenol oxidase (PPO) in Mcllvaine buffer (pH=3.6, typical pH of blueberry juice) was subjected to processing at isothermal-isobaric conditions at temperatures from 30 to 80 °C and pressure from 0.1 to 700 MPa. High pressure processing at 30-50 °C at all pressures studied caused irreversible PPO activity increase with a maximum of 6.1 fold increase at 500 MPa and 30 °C. Treatments at mild pressure-mild temperature conditions (0.1-400 MPa, 60 °C) also caused up to 3 fold PPO activity increase. Initial activity increase followed by a decrease occurred at relatively high pressure-mild temperature (400-600 MPa, 60 °C) and mild pressure-high temperature (0.1-400 MPa, 70-80 °C) combinations. At temperatures higher than 76 °C, monotonic decrease in PPO activity occurred at 0.1 MPa and pressures higher than 500 MPa. The activation/inactivation kinetics of the enzyme was successfully modelled assuming consecutive reactions in series with activation followed by inactivation. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Electric utility acid fuel cell stack technology advancement

NASA Astrophysics Data System (ADS)

Congdon, J. V.; Goller, G. J.; Greising, G. J.; Obrien, J. J.; Randall, S. A.; Sandelli, G. J.; Breault, R. D.; Austin, G. W.; Bopse, S.; Coykendall, R. D.

1984-11-01

The principal effort under this program was directed at the fuel cell stack technology required to accomplish the initial feasibility demonstrations of increased cell stack operating pressures and temperatures, increased cell active area, incorporation of the ribbed substrate cell configuration at the bove conditions, and the introduction of higher performance electrocatalysts. The program results were successful with the primary accomplishments being: (1) fabrication of 10 sq ft ribbed substrate, cell components including higher performing electrocatalysts; (2) assembly of a 10 sq ft, 30-cell short stack; and (3) initial test of this stack at 120 psia and 405 F. These accomplishments demonstrate the feasibility of fabricating and handling large area cells using materials and processes that are oriented to low cost manufacture. An additional accomplishment under the program was the testing of two 3.7 sq ft short stacks at 12 psia/405 F to 5400 and 4500 hours respectively. These tests demonstrate the durability of the components and the cell stack configuration to a nominal 5000 hours at the higher pressure and temperature condition planned for the next electric utility power plant.

Subcritical hydrothermal liquefaction of cattle manure to bio-oil: Effects of conversion parameters on bio-oil yield and characterization of bio-oil.

PubMed

Yin, Sudong; Dolan, Ryan; Harris, Matt; Tan, Zhongchao

2010-05-01

In this study, cattle manure was converted to bio-oil by subcritical hydrothermal liquefaction in the presence of NaOH. The effects of conversion temperature, process gas, initial conversion pressure, residence time and mass ratio of cattle manure to water on the bio-oil yield were studied. The bio-oil was characterized in terms of elemental composition, higher heating value, ultraviolet-visible (UV/Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Results showed that the bio-oil yield depended on the conversion temperature and the process gas. Higher initial conversion pressure, longer residence time and larger mass ratio of cattle manure to water, however, had negative impacts on the bio-oil yield. The higher heating value of bio-oil was 35.53MJ/kg on average. The major non-polar components of bio-oil were toluene, ethyl benzene and xylene, which are components of crude oil, gasoline and diesel. Copyright 2010 Elsevier Ltd. All rights reserved.

Electric utility acid fuel cell stack technology advancement

NASA Technical Reports Server (NTRS)

Congdon, J. V.; Goller, G. J.; Greising, G. J.; Obrien, J. J.; Randall, S. A.; Sandelli, G. J.; Breault, R. D.; Austin, G. W.; Bopse, S.; Coykendall, R. D.

1984-01-01

The principal effort under this program was directed at the fuel cell stack technology required to accomplish the initial feasibility demonstrations of increased cell stack operating pressures and temperatures, increased cell active area, incorporation of the ribbed substrate cell configuration at the bove conditions, and the introduction of higher performance electrocatalysts. The program results were successful with the primary accomplishments being: (1) fabrication of 10 sq ft ribbed substrate, cell components including higher performing electrocatalysts; (2) assembly of a 10 sq ft, 30-cell short stack; and (3) initial test of this stack at 120 psia and 405 F. These accomplishments demonstrate the feasibility of fabricating and handling large area cells using materials and processes that are oriented to low cost manufacture. An additional accomplishment under the program was the testing of two 3.7 sq ft short stacks at 12 psia/405 F to 5400 and 4500 hours respectively. These tests demonstrate the durability of the components and the cell stack configuration to a nominal 5000 hours at the higher pressure and temperature condition planned for the next electric utility power plant.

Aluminosilicate melts and glasses at 1 to 3 GPa: Temperature and pressure effects on recovered structural and density changes

USGS Publications Warehouse

Bista, S; Stebbins, Jonathan; Hankins, William B.; Sisson, Thomas W.

2015-01-01

In the pressure range in the Earth’s mantle where many basaltic magmas are generated (1 to 3 GPa) (Stolper et al. 1981), increases in the coordination numbers of the network-forming cations in aluminosilicate melts have generally been considered to be minor, although effects on silicon and particularly on aluminum coordination in non-bridging oxygen-rich glasses from the higher, 5 to 12 GPa range, are now well known. Most high-precision measurements of network cation coordination in such samples have been made by spectroscopy (notably 27Al and 29Si NMR) on glasses quenched from high-temperature, high-pressure melts synthesized in solid-media apparatuses and decompressed to room temperature and 1 bar pressure. There are several effects that could lead to the underestimation of the extent of actual structural (and density) changes in high-pressure/temperature melts from such data. For non-bridging oxygen-rich sodium and calcium aluminosilicate compositions in the 1 to 3 GPa range, we show here that glasses annealed near to their glass transition temperatures systematically record higher recovered increases in aluminum coordination and in density than samples quenched from high-temperature melts. In the piston-cylinder apparatus used, rates of cooling through the glass transition are measured as very similar for both higher and lower initial temperatures, indicating that fictive temperature effects are not the likely explanation of these differences. Instead, transient decreases in melt pressure during thermal quenching, which may be especially large for high initial run temperatures, of as much as 0.5 to 1 GPa, may be responsible. As a result, the equilibrium proportion of high-coordinated Al in this pressure range may be 50 to 90% greater than previously estimated, reaching mean coordination numbers (e.g., 4.5) that are probably high enough to significantly affect melt properties. New data on jadeite (NaAlSi2O6) glass confirm that aluminum coordination increase with pressure is inhibited in compositions low in non-bridging O atoms.

Invasibility of a nutrient-poor pasture through resident and non-resident herbs is controlled by litter, gap size and propagule pressure.

PubMed

Eckstein, R Lutz; Ruch, Diana; Otte, Annette; Donath, Tobias W

2012-01-01

Since inference concerning the relative effects of propagule pressure, biotic interactions, site conditions and species traits on the invasibility of plant communities is limited, we carried out a field experiment to study the role of these factors for absolute and relative seedling emergence in three resident and three non-resident confamilial herb species on a nutrient-poor temperate pasture. We set up a factorial field experiment with two levels each of the factors litter cover (0 and 400 g m(-2)), gap size (0.01 and 0.1 m(2)) and propagule pressure (5 and 50 seeds) and documented soil temperature, soil water content and relative light availability. Recruitment was recorded in spring and autumn 2010 and in spring 2011 to cover initial seedling emergence, establishment after summer drought and final establishment after the first winter. Litter alleviated temperature and moisture conditions and had positive effects on proportional and absolute seedling emergence during all phases of recruitment. Large gaps presented competition-free space with high light availability but showed higher temperature amplitudes and lower soil moisture. Proportional and absolute seedling recruitment was significantly higher in large than in small gaps. In contrast, propagule pressure facilitated absolute seedling emergence but had no effects on proportional emergence or the chance for successful colonisation. Despite significantly higher initial seedling emergence of resident than non-resident species, seed mass and other species-specific traits may be better predictors for idiosyncratic variation in seedling establishment than status. Our data support the fluctuating resource hypothesis and demonstrate that the reserve effect of seeds may facilitate seedling emergence. The direct comparison of propagule pressure with other environmental factors showed that propagule pressure affects absolute seedling abundance, which may be crucial for species that depend on other individuals for sexual reproduction. However, propagule batch size did not significantly affect the chance for successful colonisation of disturbed plots.

Comparison of Efficacy and Tolerance of Automatic Continuous Positive Airway Pressure Devices With the Optimum Continuous Positive Airway Pressure.

PubMed

Tommi, George; Aronow, Wilbert S; Sheehan, John C; McCleay, Matthew T; Meyers, Patrick G

Patients diagnosed with obstructive sleep apnea syndrome were randomly placed on automatic continuous positive airway pressure (ACPAP) for 2 hours followed by manual titration for the rest of the night. One hundred sixty-one patients entered the study, with at least 50 patients titrated with each of 3 ACPAP devices. The optimum continuous positive airway pressure (CPAP) was defined as the lowest pressure with an apnea-hypoxia index of ≤5/hr, which ranged from 4 cm to 18 cm. Success with ACPAP was approximately 60%-80% when the optimum CPAP was 4-6 cm but fell to below 30% if the optimum CPAP was ≥8 cm (P = 0.001). Average ACPAP ranged from 2 to 10 cm below the optimum level if the optimum CPAP was ≥8 cm. Patients who responded to a low CPAP but deteriorated on higher pressures failed to respond to any of the automatic devices. We recommend that CPAP titration be performed manually before initiation of ACPAP in patients with obstructive sleep apnea. The basal pressure for ACPAP should be the optimum pressure obtained by manual titration. Limits on the upper level of ACPAP may be necessary for patients who deteriorate on higher positive pressures.

Retrocalcaneal bursitis but not Achilles tendinopathy is characterized by increased pressure in the retrocalcaneal bursa.

PubMed

Lohrer, Heinz; Nauck, Tanja

2014-03-01

We questioned whether different forms of Achilles tendon overuse injuries can be differentiated by retrocalcaneal bursa pressure measurement. Retrocalcaneal bursa pressure was determined by using invasive pressure measurement in patients suffering from retrocalcaneal bursitis (n=13) or Achilles tendinopathy (n=15), respectively. Standardized measurements were taken with the subject lying prone. Initially, the foot and ankle was in a spontaneous, unsupported position. Then passive dorsiflexion was induced by an increasing pressure which was applied in five defined steps against the plantar forefoot. Mean pressures found in unloaded position were 30.5 (SD 28.9) mmHg in retrocalcaneal bursitis and -9.9 (SD 17.2) mmHg in Achilles tendinopathy (p<0.001). A stepwise increase in passive ankle dorsiflexion was associated with increasing pressure values in both groups. The differences were p=0.009 to 0.035 when dorsiflexion was initiated with 10, 20, 30, and 40N, respectively. Dorsiflexion induced by 50N load resulted in a mean pressure of 113.7 (SD 124.9) mmHg for retrocalcaneal bursitis and 32.5 (SD 48.9) mmHg for Achilles tendinopathy (p=0,051). Higher retrocalcaneal bursa pressure values were found in patients suffering from chronic retrocalcaneal bursitis. This result supports the hypothesis that retrocalcaneal bursa hypertension leads to an impingement lesion of the corresponding anterior Achilles tendon. Copyright © 2013 Elsevier Ltd. All rights reserved.

High Temperature Electrolysis Pressurized Experiment Design, Operation, and Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

J.E. O'Brien; X. Zhang; G.K. Housley

2012-09-01

A new facility has been developed at the Idaho National Laboratory for pressurized testing of solid oxide electrolysis stacks. Pressurized operation is envisioned for large-scale hydrogen production plants, yielding higher overall efficiencies when the hydrogen product is to be delivered at elevated pressure for tank storage or pipelines. Pressurized operation also supports higher mass flow rates of the process gases with smaller components. The test stand can accommodate planar cells with dimensions up to 8.5 cm x 8.5 cm and stacks of up to 25 cells. It is also suitable for testing other cell and stack geometries including tubular cells.more » The pressure boundary for these tests is a water-cooled spool-piece pressure vessel designed for operation up to 5 MPa. Pressurized operation of a ten-cell internally manifolded solid oxide electrolysis stack has been successfully demonstrated up 1.5 MPa. The stack is internally manifolded and operates in cross-flow with an inverted-U flow pattern. Feed-throughs for gas inlets/outlets, power, and instrumentation are all located in the bottom flange. The entire spool piece, with the exception of the bottom flange, can be lifted to allow access to the internal furnace and test fixture. Lifting is accomplished with a motorized threaded drive mechanism attached to a rigid structural frame. Stack mechanical compression is accomplished using springs that are located inside of the pressure boundary, but outside of the hot zone. Initial stack heatup and performance characterization occurs at ambient pressure followed by lowering and sealing of the pressure vessel and subsequent pressurization. Pressure equalization between the anode and cathode sides of the cells and the stack surroundings is ensured by combining all of the process gases downstream of the stack. Steady pressure is maintained by means of a backpressure regulator and a digital pressure controller. A full description of the pressurized test apparatus is provided in this report. Results of initial testing showed the expected increase in open-cell voltage associated with elevated pressure. However, stack performance in terms of area-specific resistance was enhanced at elevated pressure due to better gas diffusion through the porous electrodes of the cells. Some issues such as cracked cells and seals were encountered during testing. Full resolution of these issues will require additional testing to identify the optimum test configurations and protocols.« less

Heat exchangers made of polymer-bonded La(Fe,Si)13

NASA Astrophysics Data System (ADS)

Skokov, K. P.; Karpenkov, D. Yu.; Kuz'min, M. D.; Radulov, I. A.; Gottschall, T.; Kaeswurm, B.; Fries, M.; Gutfleisch, O.

2014-05-01

We report on magnetocaloric properties of polymer-bonded La(Fe,Si)13 heat exchangers with respect to the grain size of the powder used and the pressure applied for compaction of plates. Quite remarkably, it was found that the values of the adiabatic temperature change of polymer-bonded plates are 10% higher than in the initial bulk material. A critical value of the pressure applied during the compaction was found. Exceeding this value leads to a drastic reduction of the magnetocaloric effect due to cracking and comminution of the initial 50-100 μm grains down to 1-10 μm fragments. Compacting the LaFe11.6Si1.4 powder with 5 wt. % of silver epoxy under an optimal pressure of 0.1 GPa resulted in the production of 0.6 mm-thick plates. These plates were subsequently stacked and glued together into a simple porous heat exchanger with straight 0.6 mm-width channels.

Initial comparison of single cylinder Stirling engine computer model predictions with test results

NASA Technical Reports Server (NTRS)

Tew, R. C., Jr.; Thieme, L. G.; Miao, D.

1979-01-01

A NASA developed digital computer code for a Stirling engine, modelling the performance of a single cylinder rhombic drive ground performance unit (GPU), is presented and its predictions are compared to test results. The GPU engine incorporates eight regenerator/cooler units and the engine working space is modelled by thirteen control volumes. The model calculates indicated power and efficiency for a given engine speed, mean pressure, heater and expansion space metal temperatures and cooler water inlet temperature and flow rate. Comparison of predicted and observed powers implies that the reference pressure drop calculations underestimate actual pressure drop, possibly due to oil contamination in the regenerator/cooler units, methane contamination in the working gas or the underestimation of mechanical loss. For a working gas of hydrogen, the predicted values of brake power are from 0 to 6% higher than experimental values, and brake efficiency is 6 to 16% higher, while for helium the predicted brake power and efficiency are 2 to 15% higher than the experimental.

Cardiovascular responses of men and women to lower body negative pressure

NASA Technical Reports Server (NTRS)

Montgomery, L. D.; Kirk, P. J.; Payne, P. A.; Gerber, R. L.; Newton, S. D.; Williams, B. A.

1977-01-01

Changes in blood flow and blood redistribution were measured by impedance plethysmography in the pelvic and leg regions of six male and four female subjects during three 5-min exposures to -20, -40, and -60 mm Hg lower body negative pressure (LBNP). Female subjects demonstrated significantly higher mean heart rate and lower leg blood flow indices than the male subjects during the recumbent control periods. Men had slightly higher mean resting systolic and diastolic blood pressures and higher mean control pelvic blood indices. Women demonstrated significantly less blood pooling in the legs and slightly less in the pelvic region than the men. All of the 18 tests with male subjects at -60 mm Hg were completed without initial signs of syncope, while only two of the tests with women were completed successfully without the subject exhibiting presyncopal conditions. Results indicate that impedance plethysmography can be used to measure segmental cardiovascular responses during LBNP and that females may be less tolerant to -60 mm Hg LBNP than males.

Temperature and pressure influence on explosion pressures of closed vessel propane-air deflagrations.

PubMed

Razus, Domnina; Brinzea, Venera; Mitu, Maria; Oancea, Dumitru

2010-02-15

An experimental study on pressure evolution during closed vessel explosions of propane-air mixtures was performed, for systems with various initial concentrations and pressures ([C(3)H(8)]=2.50-6.20 vol.%, p(0)=0.3-1.2 bar). The explosion pressures and explosion times were measured in a spherical vessel (Phi=10 cm), at various initial temperatures (T(0)=298-423 K) and in a cylindrical vessel (Phi=10 cm; h=15 cm), at ambient initial temperature. The experimental values of explosion pressures are examined against literature values and compared to adiabatic explosion pressures, computed by assuming chemical equilibrium within the flame front. The influence of initial pressure, initial temperature and fuel concentration on explosion pressures and explosion times are discussed. At constant temperature and fuel/oxygen ratio, the explosion pressures are linear functions of total initial pressure, as reported for other fuel-air mixtures. At constant initial pressure and composition, both the measured and calculated (adiabatic) explosion pressures are linear functions of reciprocal value of initial temperature. Such correlations are extremely useful for predicting the explosion pressures of flammable mixtures at elevated temperatures and/or pressures, when direct measurements are not available.

Local Limit Phenomena, Flow Compression, and Fuel Cracking Effects in High-Speed Turbulent Flames

DTIC Science & Technology

2015-06-01

e.g. local extinction and re- ignition , interactions between flow compression and fast-reaction induced dilatation (reaction compression ), and to...time as a function of initial temperature in constant-pressure auto - ignition , and (b) the S-curves of perfectly stirred reactors (PSRs), for n...mechanism. The reduction covered auto - ignition and perfectly stirred reactors for equivalence ratio range of 0.5~1.5, initial temperature higher than

Effects of high-pressure extruding pretreatment on MSW upgrading and hydrolysis enhancement.

PubMed

Xu, Shuang; Kong, Xin; Liu, Jianguo; Zhao, Ke; Zhao, Guangqi; Bahdolla, Amanjol

2016-12-01

High-pressure extruding (HPE) is an efficient technology used to separate municipal solid waste (MSW) into wet (biodegradable) and dry (combustible) fractions. Effects of pressure, 10, 20, 30, and 40MPa on quality upgrading of the MSW and hydrolysis of the wet fraction were examined. TS of the dry fraction increased from 48.5% to 59.4% when the extruding pressure increased from 10 to 40MPa, meanwhile the biochemical methane potential (BMP) of the wet fraction extruded under 40MPa was 674mL CH 4 /g·VS, 33% higher than that of the organic fraction of the MSW (OFMSW) control. Furthermore, in the initial stage of hydrolysis experiment, the extruded wet fractions had lower pH and higher COD, volatile fatty acids (VFAs) and COD/VFA than those of the OFMSW control. The results confirmed that HPE upgraded the MSW and enhanced hydrolysis of the wet fractions. However, high extruding pressure as 40MPa aggravated the excessive acidification of the wet fractions. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Relationship Between Preoperative and Primary Care Blood Pressure Among Veterans Presenting from Home for Surgery. Is There Evidence for Anesthesiologist-Initiated Blood Pressure Referral?

PubMed Central

Schonberger, Robert B.; Burg, Matthew M.; Holt, Natalie; Lukens, Carrie L.; Dai, Feng; Brandt, Cynthia

2011-01-01

Background American College of Cardiology/American Heart Association guidelines describe the perioperative evaluation as “a unique opportunity to identify patients with hypertension,” however factors such as anticipatory stress or medication noncompliance may induce a bias toward higher blood pressure, leaving clinicians unsure about how to interpret preoperative hypertension. Information describing the relationship between preoperative intake blood pressure and primary care measurements could help anesthesiologists make primary care referrals for improved blood pressure control in an evidence-based fashion. We hypothesized that the preoperative examination provides a useful basis for initiating primary care blood pressure referral. Methods We analyzed retrospective data on 2807 patients who arrived from home for surgery and who were subsequently evaluated within 6 months after surgery in the primary care center of the same institution. After descriptive analysis, we conducted multiple linear regression analysis to identify day-of-surgery (DOS) factors associated with subsequent primary care blood pressure. We calculated the sensitivity, specificity, and positive and negative predictive value of different blood pressure referral thresholds using both a single-measurement and a two-stage screen incorporating recent preoperative and DOS measurements for identifying patients with subsequently elevated primary care blood pressure. Results DOS systolic blood pressure (SBP) was higher than subsequent primary care SBP by a mean bias of 5.5mmHg (95% limits of agreement +43.8 to −32.8). DOS diastolic blood pressure (DBP) was higher than subsequent primary care DBP by a mean bias of 1.5mmHg (95% limits of agreement +13.0 to −10.0). Linear regression of DOS factors explained 19% of the variability in primary care SBP and 29% of the variability in DBP. Accounting for the observed bias, a two-stage SBP referral screen requiring preoperative clinic SBP≥140mmHg and DOS SBP≥146mmHg had 95.9% estimated specificity (95% CI 94.4 to 97.0) for identifying subsequent primary care SBP≥140mmHg and estimated sensitivity of 26.8% (95% CI 22.0 to 32.0). A similarly high specificity using a single DOS SBP required a threshold SBP≥160mmHg, for which estimated specificity was 95.2% (95% CI 94.2 to 96.1). For DBP, a presenting DOS DBP≥92mmHg had 95.7% specificity (95% CI 94.8 to 96.4) for subsequent primary care DBP≥90mmHg with a sensitivity of 18.8% (95% CI 14.4 to 24.0). Conclusion A small bias toward higher DOS blood pressures relative to subsequent primary care measurements was observed. DOS factors predicted only a small proportion of the observed variation. Accounting for the observed bias, a two-stage SBP threshold and a single-reading DBP threshold were highly specific though insensitive for identifying subsequent primary care blood pressure elevation. PMID:22075017

Intracranial pressure after subarachnoid hemorrhage.

PubMed

Zoerle, Tommaso; Lombardo, Alessandra; Colombo, Angelo; Longhi, Luca; Zanier, Elisa R; Rampini, Paolo; Stocchetti, Nino

2015-01-01

To describe mean intracranial pressure after aneurysmal subarachnoid hemorrhage, to identify clinical factors associated with increased mean intracranial pressure, and to explore the relationship between mean intracranial pressure and outcome. Analysis of a prospectively collected observational database. Neuroscience ICU of an academic hospital. One hundred sixteen patients with subarachnoid hemorrhage and intracranial pressure monitoring. None. Episodes of intracranial pressure greater than 20 mm Hg lasting at least 5 minutes and the mean intracranial pressure for every 12-hour interval were analyzed. The highest mean intracranial pressure was analyzed in relation to demographic characteristics, acute neurologic status, initial radiological findings, aneurysm treatment, clinical vasospasm, and ischemic lesion. Mortality and 6-month outcome (evaluated using a dichotomized Glasgow Outcome Scale) were also introduced in multivariable logistic models. Eighty-one percent of patients had at least one episode of high intracranial pressure and 36% had a highest mean intracranial pressure more than 20 mm Hg. The number of patients with high intracranial pressure peaked 3 days after subarachnoid hemorrhage and declined after day 7. Highest mean intracranial pressure greater than 20 mm Hg was significantly associated with initial neurologic status, aneurysmal rebleeding, amount of blood on CT scan, and ischemic lesion within 72 hours from subarachnoid hemorrhage. Patients with highest mean intracranial pressure greater than 20 mm Hg had significantly higher mortality. When death, vegetative state, and severe disability at 6 months were pooled, however, intracranial pressure was not an independent predictor of unfavorable outcome. High intracranial pressure is a common complication in the first week after subarachnoid hemorrhage in severe cases admitted to ICU. Mean intracranial pressure is associated with the severity of early brain injury and with mortality.

MAGMIX: a basic program to calculate viscosities of interacting magmas of differing composition, temperature, and water content

USGS Publications Warehouse

Frost, T.P.; Lindsay, J.R.

1988-01-01

MAGMIX is a BASIC program designed to predict viscosities at thermal equilibrium of interacting magmas of differing compositions, initial temperatures, crystallinities, crystal sizes, and water content for any mixing proportion between end members. From the viscosities of the end members at thermal equilibrium, it is possible to predict the styles of magma interaction expected for different initial conditions. The program is designed for modeling the type of magma interaction between hypersthenenormative magmas at upper crustal conditions. Utilization of the program to model magma interaction at pressures higher than 200 MPa would require modification of the program to account for the effects of pressure on heat of fusion and magma density. ?? 1988.

Pressure-Relief Features of Fixed and Autotitrating Continuous Positive Airway Pressure May Impair Their Efficacy: Evaluation with a Respiratory Bench Model

PubMed Central

Zhu, Kaixian; Aouf, Sami; Roisman, Gabriel; Escourrou, Pierre

2016-01-01

Study Objectives: Pressure-relief features are aimed at improving the patient's comfort during continuous positive airway pressure (CPAP) treatment for obstructive sleep apnea. The objective of this study was to determine the effect of these therapy features on fixed CPAP and autotitrating CPAP (APAP) treatment efficacy. Methods: Seven pressure-relief features applied by three CPAP devices were included in our study (Remstar Auto: C-Flex 3, C-Flex+ 3, A-Flex 3, P-Flex; AirSense 10: EPR 3; Prisma 20A: SoftPAP 2 and 3). In fixed CPAP, the devices were subjected to a 10-min bench-simulated obstructive apnea sequence (initial apnea-hypopnea index, AHI = 60/h) with and without pressure-relief features. In APAP, the sequence was lengthened to 4.2 h (initial AHI = 58.6/h). The residual AHI and mean/median pressure were compared with and without pressure-relief features. Results: Compared to conventional CPAP, where pressure was adjusted to be just sufficient to control the simulated obstructive events, C-Flex+ 3, P-Flex, and EPR 3 failed to normalize the breathing flow and did not reduce the AHI. The mean pressures with the three features, respectively, were 1.8, 2.6, and 2.6 cmH2O lower than the conventional CPAP. Compared to conventional APAP, similar levels of control were observed with pressure-relief features, apart from P-Flex where the delivered mean pressure was lower and residual AHI greater. The device-reported mean/median pressures in APAP with A-Flex 3, P-Flex, EPR 3, and SoftPAP 3 were higher than that measured on the bench. Conclusions: Pressure-relief features may attenuate CPAP efficacy if not adjusted for at the time of their introduction. In clinical practice, efficacy can be ensured by increasing the therapeutic pressure delivered by fixed CPAP or by enabling the pressure-relief features prior to initial pressure titration. Device-reported pressures in APAP devices with pressure relief activated may overstate delivered pressures. Citation: Zhu K, Aouf S, Roisman G, Escourrou P. Pressure-relief features of fixed and autotitrating continuous positive airway pressure may impair their efficacy: evaluation with a respiratory bench model. J Clin Sleep Med 2016;12(3):385–392. PMID:26564383

Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

DOE PAGES

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; ...

2014-11-07

High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Smtype→ dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GP and a temperaturemore » of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Furthermore, our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.« less

Magnetic and magnetocaloric properties of Ni-Mn-Cr-Sn Heusler alloys under the effects of hydrostatic pressure

NASA Astrophysics Data System (ADS)

Pandey, Sudip; Us Saleheen, Ahmad; Quetz, Abdiel; Chen, Jing-Han; Aryal, Anil; Dubenko, Igor; Stadler, Shane; Ali, Naushad

2018-05-01

The magnetic, thermal, and magnetocaloric properties of Ni45Mn43CrSn11 Heusler alloy have been investigated using differential scanning calorimetry and magnetization with hydrostatic pressure measurements. A shift in the martensitic transition temperature (TM) to higher temperatures was observed with the application of pressure. The application of pressure stabilizes the martensitic state and demonstrated that pressure can be a parameter used to control and tune the martensitic transition temperature (the temperature where the largest magnetocaloric effect is observed). The magnetic entropy change significantly decreases from 33 J/kg K to 16 J/kg K under the application of a hydrostatic pressure of 0.95 GPa. The critical field of the direct metamagnetic transition increases, whereas the initial susceptibility (dM/dH) in the low magnetic field region drastically decreases with increasing pressure. The relevant parameters that affect the magnetocaloric properties are discussed.

First-principles study of the elastic and thermodynamic properties of CaSiO(3) perovskite.

PubMed

Liu, Z J; Sun, X W; Chen, Q F; Cai, L C; Wu, H Y; Ge, S H

2007-06-20

The thermodynamic and elastic properties of CaSiO(3) perovskite are investigated at high pressures and temperatures using the plane wave pseudopotential method within the local density approximation. The athermal elastic moduli of CaSiO(3) perovskite are calculated as a function of pressure up to 200 GPa. The calculated results are in excellent agreement with available experimental data at high pressure, and compare favourably with other pseudopotential predictions over the pressure regime studied. It is also found that the elastic anisotropy drops rapidly with the increase of pressure initially, and then decreases more slowly at higher pressures. The thermodynamic properties of CaSiO(3) perovskite are predicted using the quasi-harmonic Debye model for the first time; the heat capacity and the thermal expansion coefficient agree with the observed values at ambient conditions and the other calculations at high pressures and temperatures.

Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.

High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Smtype→ dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GP and a temperaturemore » of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Furthermore, our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.« less

Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

NASA Astrophysics Data System (ADS)

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; Vohra, Yogesh K.

2014-10-01

High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Sm-type → dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GPa and a temperature of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.

Pressurized chemical-looping combustion of coal with an iron ore-based oxygen carrier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Rui; Song, Min; Zhang, Shuai

2010-06-15

Chemical-looping combustion (CLC) is a new combustion technology with inherent separation of CO{sub 2}. Most of the previous investigations on CLC of solid fuels were conducted under atmospheric pressure. A pressurized CLC combined cycle (PCLC-CC) system is proposed as a promising coal combustion technology with potential higher system efficiency, higher fuel conversion, and lower cost for CO{sub 2} sequestration. In this study pressurized CLC of coal with Companhia Valedo Rio Doce (CVRD) iron ore was investigated in a laboratory fixed bed reactor. CVRD iron ore particles were exposed alternately to reduction by 0.4 g of Chinese Xuzhou bituminous coal gasifiedmore » with 87.2% steam/N{sub 2} mixture and oxidation with 5% O{sub 2} in N{sub 2} at 970 C. The operating pressure was varied between 0.1 MPa and 0.6 MPa. First, control experiments of steam coal gasification over quartz sand were performed. H{sub 2} and CO{sub 2} are the major components of the gasification products, and the operating pressure influences the gas composition. Higher concentrations of CO{sub 2} and lower fractions of CO, CH{sub 4}, and H{sub 2} during the reduction process with CVRD iron ore was achieved under higher pressures. The effects of pressure on the coal gasification rate in the presence of the oxygen carrier were different for pyrolysis and char gasification. The pressurized condition suppresses the initial coal pyrolysis process while it also enhances coal char gasification and reduction with iron ore in steam, and thus improves the overall reaction rate of CLC. The oxidation rates and variation of oxygen carrier conversion are higher at elevated pressures reflecting higher reduction level in the previous reduction period. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analyses show that particles become porous after experiments but maintain structure and size after several cycles. Agglomeration was not observed in this study. An EDX analysis demonstrates that there is very little coal ash deposited on the oxygen carrier particles but no appreciable crystalline phases change as verified by X-ray diffraction (XRD) analysis. Overall, the limited pressurized CLC experiments carried out in the present work suggest that PCLC of coal is promising and further investigations are necessary. (author)« less

Growth mechanism and internal structure of vertically aligned single-walled carbon nanotubes.

PubMed

Einarsson, Erik; Kadowaki, Masayuki; Ogura, Kazuaki; Okawa, Jun; Xiang, Rong; Zhang, Zhengyi; Yamamoto, Takahisa; Ikuhara, Yuichi; Maruyama, Shigeo

2008-11-01

An in situ optical absorbance technique was used to monitor the growth of vertically aligned single-walled carbon nanotubes (VA-SWNTs) at various temperatures and pressures. The effects of the growth temperature and ethanol pressure on the initial growth rate and catalyst lifetime were investigated. It was found that the ideal pressure for VA-SWNT synthesis changes with the growth temperature, shifting toward higher pressure as the growth temperature increases. It was also found that the growth reaction is first-order below this ideal pressure. Additionally, the internal structure of the VA-SWNT film was observed at different depths into the film by transmission electron microscopy. The absence of large bundles was confirmed, and little change in the structure was observed to a depth of approximately 1 microm.

Using plastic instability to validate and test the strength law of a material under pressure

NASA Astrophysics Data System (ADS)

Bolis, Cyril; Counilh, Denis; Savale, Brice

2015-09-01

In dynamical experiments (pressures higher than 10 GPa, strain rate around 104-106 s-1), metals are classically described using an equation of state and a strength law which is usually set using data from compression or traction tests at low pressure (few MPa) and low strain rates (less than 103 s-1). In consequence, it needs to be extrapolated during dynamical experiments. Classical shock experiments do not allow a fine validation of the stress law due to the interaction with the equation of state. To achieve this aim, we propose to use a dedicated experiment. We started from the works of Barnes et al. (1974 and 1980) where plastic instabilities initiated by a sinusoidal perturbation at the surface of the metal develop with the pressure. We adapted this principle to a new shape of initial perturbation and realized several experiments. We will present the setup and its use on a simple material: gold. We will detail how the interpretation of the experiments, coupled with previous characterization experiments helps us to test the strength lax of this material at high pressure and high strain rate.

Microfluidic Valves Made From Polymerized Polyethylene Glycol Diacrylate

PubMed Central

Rogers, Chad I.; Oxborrow, Joseph B.; Anderson, Ryan R.; Tsai, Long-Fang; Nordin, Gregory P.; Woolley, Adam T.

2013-01-01

Pneumatically actuated, non-elastomeric membrane valves fabricated from polymerized polyethylene glycol diacrylate (poly-PEGDA) have been characterized for temporal response, valve closure, and long-term durability. A ~100 ms valve opening time and a ~20 ms closure time offer valve operation as fast as 8 Hz with potential for further improvement. Comparison of circular and rectangular valve geometries indicates that the surface area for membrane interaction in the valve region is important for valve performance. After initial fabrication, the fluid pressure required to open a closed circular valve is ~50 kPa higher than the control pressure holding the valve closed. However, after ~1000 actuations to reconfigure polymer chains and increase elasticity in the membrane, the fluid pressure required to open a valve becomes the same as the control pressure holding the valve closed. After these initial conditioning actuations, poly-PEGDA valves show considerable robustness with no change in effective operation after 115,000 actuations. Such valves constructed from non-adsorptive poly-PEGDA could also find use as pumps, for application in small volume assays interfaced with biosensors or impedance detection, for example. PMID:24357897

Classification of the nonlinear dynamics and bifurcation structure of ultrasound contrast agents excited at higher multiples of their resonance frequency

NASA Astrophysics Data System (ADS)

Sojahrood, Amin Jafari; Kolios, Michael C.

2012-07-01

Through numerical simulation of the Hoff model we show that when ultrasound contrast agents (UCAs) are excited at frequencies which are close to integer (m>2) multiples of their natural resonance frequency, the bifurcation structure of the UCA oscillations as a function of pressure may be characterized by 3 general distinct regions. The UCA behavior starts with initial period one oscillations which undergoes a saddle node bifurcation to m coexisting attractors for an acoustic pressure above a threshold, P. Further increasing the pressure above a second threshold P, is followed by a sudden transition to period 1 oscillations.

Getting used to academic public speaking: global self-esteem predicts habituation in blood pressure response to repeated thesis presentations.

PubMed

Elfering, Achim; Grebner, Simone

2012-06-01

Global self-esteem was tested to predict quicker cardiovascular adaptation during stressful oral thesis presentation and faster habituation from the first to the second and third thesis presentations. Nineteen graduate students initially rated their global self-esteem and afterwards orally presented their theses proposals in 20-min presentations to their thesis supervisor and peers. A second and third presentation of the revised thesis concepts took place at 4-weeks intervals. Ambulatory blood pressure and heart rate were assessed repeatedly during the presentations. Post-talk self ratings of stressfulness indicated presentations to be a strong public speaking stressor. One hundred and thirty-eight measurements of systolic (SBP), diastolic blood pressure (DBP), and heart rate (HR) showed a significant adaptation (decrease) during presentations. There was an overall mean level decrease from the first to the second, and the second to the third presentations in HR, but not in SBP and DBP. However, habituation in SBP and DBP across three presentations was significantly faster (p < .05) in those participants who initially reported higher levels of global self-esteem. Higher global self-esteem did not foster adaptation within the presentations. Self-esteem is discussed as an important individual resource that allows successful coping with recurring evaluative threats.

Self-contained small utility system

DOEpatents

Labinov, Solomon D.; Sand, James R.

1995-01-01

A method and apparatus is disclosed to provide a fuel efficient source of readily converted energy to an isolated or remote energy consumption facility. External heat from any of a large variety of sources is converted to an electrical, mechanical, heat or cooling form of energy. A polyatomic working fluid energized by external heat sources is dissociated to a higher gaseous energy state for expansion through a turbine prime mover. The working fluid discharge from the turbine prime mover is routed to a recouperative heat exchanger for exothermic recombination reaction heat transfer to working fluid discharged from the compressor segment of the thermodynaic cycle discharge. The heated compressor discharge fluid is thereafter further heated by the external heat source to the initial higher energy state. Under the pressure at the turbine outlet, the working fluid goes out from a recouperative heat exchanger to a superheated vapor heat exchanger where it is cooled by ambient medium down to an initial temperature of condensation. Thereafter, the working fluid is condensed to a complete liquid state in a condenser cooled by an external medium. This liquid is expanded isenthalpically down to the lowest pressure of the cycle. Under this pressure, the working fluid is evaporated to the superheated vapor state of the inlet of a compressor.

Fluid Pressures at the Shoe-Floor-Contaminant Interface During Slips: Effects of Tread & Implications on Slip Severity

PubMed Central

Beschorner, Kurt E.; Albert, Devon L.; Chambers, April J.; Redfern, Mark S.

2018-01-01

Previous research on slip and fall accidents has suggested that pressurized fluid between the shoe and floor is responsible for initiating slips yet this effect has not been verified experimentally. This study aimed to 1) measure hydrodynamic pressures during slipping for treaded and untreaded conditions; 2) determine the effects of fluid pressure on slip severity; and 3) quantify how fluid pressures vary with instantaneous resultant slipping speed, position on the shoe surface, and throughout the progression of the slip. Eighteen subjects walked on known dry and unexpected slippery floors, while wearing treaded and untreaded shoes. Fluid pressure sensors, embedded in the floor, recorded hydrodynamic pressures during slipping. The maximum fluid pressures (mean+/−standard deviation) were significantly higher for the untreaded conditions (124 +/−75 kPa) than the treaded conditions (1.1 +/−0.29 kPa). Maximum fluid pressures were positively correlated with peak slipping speed (r = 0.87), suggesting that higher fluid pressures, which are associated with untreaded conditions, resulted in more severe slips. Instantaneous resultant slipping speed and position of sensor relative to the shoe sole and walking direction explained 41% of the fluid pressure variability. Fluid pressures were primarily observed for untreaded conditions. This study confirms that fluid pressures are relevant to slipping events, consistent with fluid dynamics theory (i.e. the Reynolds equation), and can be modified with shoe tread design. The results suggest that the occurrence and severity of unexpected slips can be reduced by designing shoes/floors that reduce underfoot fluid pressures. PMID:24267270

Mechanical ventilation management during extracorporeal membrane oxygenation for acute respiratory distress syndrome: a retrospective international multicenter study.

PubMed

Schmidt, Matthieu; Stewart, Claire; Bailey, Michael; Nieszkowska, Ania; Kelly, Joshua; Murphy, Lorna; Pilcher, David; Cooper, D James; Scheinkestel, Carlos; Pellegrino, Vincent; Forrest, Paul; Combes, Alain; Hodgson, Carol

2015-03-01

To describe mechanical ventilation settings in adult patients treated for an acute respiratory distress syndrome with extracorporeal membrane oxygenation and assess the potential impact of mechanical ventilation settings on ICU mortality. Retrospective observational study. Three international high-volume extracorporeal membrane oxygenation centers. A total of 168 patients treated with extracorporeal membrane oxygenation for severe acute respiratory distress syndrome from January 2007 to January 2013. We analyzed the association between mechanical ventilation settings (i.e. plateau pressure, tidal volume, and positive end-expiratory pressure) on ICU mortality using multivariable logistic regression model and Cox-proportional hazards model. We obtained detailed demographic, clinical, daily mechanical ventilation settings and ICU outcome data. One hundred sixty-eight patients (41 ± 14 years old; PaO2/FIO2 67 ± 19 mm Hg) fulfilled our inclusion criteria. Median duration of extracorporeal membrane oxygenation and ICU stay were 10 days (6-18 d) and 28 days (16-42 d), respectively. Lower positive end-expiratory pressure levels and significantly lower plateau pressures during extracorporeal membrane oxygenation were used in the French center than in both Australian centers (23.9 ± 1.4 vs 27.6 ± 3.7 and 27.8 ± 3.6; p < 0.0001). Overall ICU mortality was 29%. Lower positive end-expiratory pressure levels (until day 7) and lower delivered tidal volume after 3 days on extracorporeal membrane oxygenation were associated with significantly higher mortality (p < 0.05). In multivariate analysis, higher positive end-expiratory pressure levels during the first 3 days of extracorporeal membrane oxygenation support were associated with lower mortality (odds ratio, 0.75; 95% CI, 0.64-0.88; p = 0.0006). Other independent predictors of ICU mortality included time between ICU admission and extracorporeal membrane oxygenation initiation, plateau pressure greater than 30 cm H2O before extracorporeal membrane oxygenation initiation, and lactate level on day 3 of extracorporeal membrane oxygenation support. Protective mechanical ventilation strategies were routinely used in high-volume extracorporeal membrane oxygenation centers. However, higher positive end-expiratory pressure levels during the first 3 days on extracorporeal membrane oxygenation support were independently associated with improved survival. Further prospective trials on the optimal mechanical ventilation strategy during extracorporeal membrane oxygenation support are warranted.

Effect of ultrasonic cavitation on measurement of sound pressure using hydrophone

NASA Astrophysics Data System (ADS)

Thanh Nguyen, Tam; Asakura, Yoshiyuki; Okada, Nagaya; Koda, Shinobu; Yasuda, Keiji

2017-07-01

Effect of ultrasonic cavitation on sound pressure at the fundamental, second harmonic, and first ultraharmonic frequencies was investigated from low to high ultrasonic intensities. The driving frequencies were 22, 304, and 488 kHz. Sound pressure was measured using a needle-type hydrophone and ultrasonic cavitation was estimated from the broadband integrated pressure (BIP). With increasing square root of electric power applied to a transducer, the sound pressure at the fundamental frequency linearly increased initially, dropped at approximately the electric power of cavitation inception, and afterward increased again. The sound pressure at the second harmonic frequency was detected just below the electric power of cavitation inception. The first ultraharmonic component appeared at around the electric power of cavitation inception at 304 and 488 kHz. However, at 22 kHz, the first ultraharmonic component appeared at a higher electric power than that of cavitation inception.

Effect of propellant deformation on ignition and combustion processes in solid propellant cracks

NASA Technical Reports Server (NTRS)

Kumar, M.; Kuo, K. K.

1980-01-01

A comprehensive theoretical model was formulated to study the development of convective burning in a solid propellant crack which continually deforms due to burning and pressure loading. In the theoretical model, the effect of interrelated structural deformation and combustion processes was taken into account by considering (1) transient, one dimensional mass, momentum, and energy conservation equations in the gas phase; (2) a transient, one dimensional heat conduction equation in the solid phase; and (3) quasi-static deformation of the two dimensional, linear viscoelastic propellant crack caused by pressure loading. Partial closures may generate substantial local pressure peaks along the crack, implying a strong coupling between chamber pressurization, crack combustion, and propellant deformation, especially when the cracks are narrow and the chamber pressurization rates high. The maximum pressure in the crack cavity is generally higher than that in the chamber. The initial flame-spreading process is not affected by propellant deformation.

An experimental study of high-pressure droplet combustion

NASA Technical Reports Server (NTRS)

Norton, Chris M.; Litchford, Ron J.; Jeng, San-Mou

1990-01-01

The results are presented of an experimental study on suspended n-heptane droplet combustion in air for reduced pressures up to P(r) = 2.305. Transition to fully transient heat-up through the critical state is demonstrated above a threshold pressure corresponding to P(r) of roughly 1.4. A silhouette imaging technique resolves the droplet surface for reduced pressures up to about P(r) roughly 0.63, but soot formation conceals the surface at higher pressures. Images of the soot plumes do not show any sudden change in behavior indicative of critical transition. Mean burning rate constants are computed from the d-squared variation law using measured effective droplet diameters at ignition and measured burn times, and corrected burning times are computed for an effective initial droplet diameter. The results show that the burning rates increase as the fuel critical pressure is approached and decrease as the pressure exceeds the fuel critical pressure. Corrected burning times show inverse behavior.

Associations between ventilator settings during extracorporeal membrane oxygenation for refractory hypoxemia and outcome in patients with acute respiratory distress syndrome: a pooled individual patient data analysis : Mechanical ventilation during ECMO.

PubMed

Serpa Neto, Ary; Schmidt, Matthieu; Azevedo, Luciano C P; Bein, Thomas; Brochard, Laurent; Beutel, Gernot; Combes, Alain; Costa, Eduardo L V; Hodgson, Carol; Lindskov, Christian; Lubnow, Matthias; Lueck, Catherina; Michaels, Andrew J; Paiva, Jose-Artur; Park, Marcelo; Pesenti, Antonio; Pham, Tài; Quintel, Michael; Marco Ranieri, V; Ried, Michael; Roncon-Albuquerque, Roberto; Slutsky, Arthur S; Takeda, Shinhiro; Terragni, Pier Paolo; Vejen, Marie; Weber-Carstens, Steffen; Welte, Tobias; Gama de Abreu, Marcelo; Pelosi, Paolo; Schultz, Marcus J

2016-11-01

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for patients with acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate associations between ventilatory settings during ECMO for refractory hypoxemia and outcome in ARDS patients. In this individual patient data meta-analysis of observational studies in adult ARDS patients receiving ECMO for refractory hypoxemia, a time-dependent frailty model was used to determine which ventilator settings in the first 3 days of ECMO had an independent association with in-hospital mortality. Nine studies including 545 patients were included. Initiation of ECMO was accompanied by significant decreases in tidal volume size, positive end-expiratory pressure (PEEP), plateau pressure, and driving pressure (plateau pressure - PEEP) levels, and respiratory rate and minute ventilation, and resulted in higher PaO 2 /FiO 2 , higher arterial pH and lower PaCO 2 levels. Higher age, male gender and lower body mass index were independently associated with mortality. Driving pressure was the only ventilatory parameter during ECMO that showed an independent association with in-hospital mortality [adjusted HR, 1.06 (95 % CI, 1.03-1.10)]. In this series of ARDS patients receiving ECMO for refractory hypoxemia, driving pressure during ECMO was the only ventilator setting that showed an independent association with in-hospital mortality.

Effect of skim milk treated with high hydrostatic pressure on permeate flux and fouling during ultrafiltration.

PubMed

Leu, Mathilde; Marciniak, Alice; Chamberland, Julien; Pouliot, Yves; Bazinet, Laurent; Doyen, Alain

2017-09-01

Ultrafiltration (UF) is largely used in the dairy industry to generate milk and whey protein concentrate for standardization of milk or production of dairy ingredients. Recently, it was demonstrated that high hydrostatic pressure (HHP) extended the shelf life of milk and improved rennet coagulation and cheese yield. Pressurization also modified casein micelle size distribution and promoted aggregation of whey proteins. These changes are likely to affect UF performance. Consequently, this study determined the effect of skim milk pressurization (300 and 600 MPa, 5 min) on UF performance in terms of permeate flux decline and fouling. The effect of HHP on milk proteins was first studied and UF was performed in total recycle mode at different transmembrane pressures to determine optimal UF operational parameters and to evaluate the effect of pressurization on critical and limiting fluxes. Ultrafiltration was also performed in concentration mode at a transmembrane pressure of 345 kPa for 130 or 140 min to evaluate the decline of permeate flux and to determine fouling resistances. It was observed that average casein micelle size decreased by 32 and 38%, whereas β-lactoglobulin denaturation reached 30 and 70% at 300 and 600 MPa, respectively. These results were directly related to UF performance because initial permeate fluxes in total recycle mode decreased by 25% at 300 and 600 MPa compared with nonpressurized milk, critical flux, and limiting flux, which were lower during UF of milk treated with HHP. During UF in concentration mode, initial permeate fluxes were 30% lower at 300 and 600 MPa compared with the control, but the total flux decline was higher for nonpressurized milk (62%) compared with pressure-treated milk (30%). Fouling resistances were similar, whatever the treatment, except at 600 MPa where irreversible fouling was higher. Characterization of the fouling layer showed that caseins and β-lactoglobulin were mainly involved in membrane fouling after UF of pressure-treated milk. Our results demonstrate that HHP treatment of skim milk drastically decreased UF performance. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Pressurized Testing of Solid Oxide Electrolysis Stacks with Advanced Electrode-Supported Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. E. O'Brien; X. Zhang; G. K. Housley

2012-06-01

A new facility has been developed at the Idaho National Laboratory for pressurized testing of solid oxide electrolysis stacks. Pressurized operation is envisioned for large-scale hydrogen production plants, yielding higher overall efficiencies when the hydrogen product is to be delivered at elevated pressure for tank storage or pipelines. Pressurized operation also supports higher mass flow rates of the process gases with smaller components. The test stand can accommodate cell dimensions up to 8.5 cm x 8.5 cm and stacks of up to 25 cells. The pressure boundary for these tests is a water-cooled spool-piece pressure vessel designed for operation upmore » to 5 MPa. The stack is internally manifolded and operates in cross-flow with an inverted-U flow pattern. Feed-throughs for gas inlets/outlets, power, and instrumentation are all located in the bottom flange. The entire spool piece, with the exception of the bottom flange, can be lifted to allow access to the internal furnace and test fixture. Lifting is accomplished with a motorized threaded drive mechanism attached to a rigid structural frame. Stack mechanical compression is accomplished using springs that are located inside of the pressure boundary, but outside of the hot zone. Initial stack heatup and performance characterization occurs at ambient pressure followed by lowering and sealing of the pressure vessel and subsequent pressurization. Pressure equalization between the anode and cathode sides of the cells and the stack surroundings is ensured by combining all of the process gases downstream of the stack. Steady pressure is maintained by means of a backpressure regulator and a digital pressure controller. A full description of the pressurized test apparatus is provided in this paper.« less

Initiation of Positive Streamers near Uncharged Ice Hydrometeors in the Thundercloud Field

NASA Astrophysics Data System (ADS)

Babich, L. P.; Bochkov, E. I.

2018-05-01

Since the threshold electric field required for breakdown of air is much higher than the maximum field strength measured in thunderstorm clouds, the problem of lightning initiation still remains unsolved. According to the popular hypothesis, lightning can be initiated by a streamer discharge in the field enhanced near a hydrometeor. To verify the adequacy of this hypothesis, the development of a positive streamer propagating along the thunderstorm electric field in the vicinity of an ice needle at an air pressure corresponding to an altitude of 5 km (which is typical of the lightning initiation conditions) was simulated numerically. The hydrometeor dimensions are determined at which streamers can be initiated at different strengths of the thunderstorm electric field.

Impact of rail pressure and biodiesel fueling on the particulate morphology and soot nanostructures from a common-rail turbocharged direct injection diesel engine

DOE PAGES

Ye, Peng; Vander Wal, Randy; Boehman, Andre L.; ...

2014-12-26

The effect of rail pressure and biodiesel fueling on the morphology of exhaust particulate agglomerates and the nanostructure of primary particles (soot) was investigated with a common-rail turbocharged direct injection diesel engine. The engine was operated at steady state on a dynamometer running at moderate speed with both low (30%) and medium–high (60%) fixed loads, and exhaust particulate was sampled for analysis. Ultra-low sulfur diesel and its 20% v/v blends with soybean methyl ester biodiesel were used. Fuel injection occurred in a single event around top dead center at three different injection pressures. Exhaust particulate samples were characterized with TEMmore » imaging, scanning mobility particle sizing, thermogravimetric analysis, Raman spectroscopy, and XRD analysis. Particulate morphology and oxidative reactivity were found to vary significantly with rail pressure and with biodiesel blend level. Higher biodiesel content led to increases in the primary particle size and oxidative reactivity but did not affect nanoscale disorder in the as-received samples. For particulates generated with higher injection pressures, the initial oxidative reactivity increased, but there was no detectable correlation with primary particle size or nanoscale disorder.« less

Impact of rail pressure and biodiesel fueling on the particulate morphology and soot nanostructures from a common-rail turbocharged direct injection diesel engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Peng; Vander Wal, Randy; Boehman, Andre L.

The effect of rail pressure and biodiesel fueling on the morphology of exhaust particulate agglomerates and the nanostructure of primary particles (soot) was investigated with a common-rail turbocharged direct injection diesel engine. The engine was operated at steady state on a dynamometer running at moderate speed with both low (30%) and medium–high (60%) fixed loads, and exhaust particulate was sampled for analysis. Ultra-low sulfur diesel and its 20% v/v blends with soybean methyl ester biodiesel were used. Fuel injection occurred in a single event around top dead center at three different injection pressures. Exhaust particulate samples were characterized with TEMmore » imaging, scanning mobility particle sizing, thermogravimetric analysis, Raman spectroscopy, and XRD analysis. Particulate morphology and oxidative reactivity were found to vary significantly with rail pressure and with biodiesel blend level. Higher biodiesel content led to increases in the primary particle size and oxidative reactivity but did not affect nanoscale disorder in the as-received samples. For particulates generated with higher injection pressures, the initial oxidative reactivity increased, but there was no detectable correlation with primary particle size or nanoscale disorder.« less

Transforming Traditions: A Study of Researchers in Higher Education

ERIC Educational Resources Information Center

Smith, Maria Jane

2012-01-01

This article reports on research initiated by the trade union for lecturers and researchers in the UK, the University and College Union (UCU), which examined the pressures, concerns and positive aspects of being a member of research staff at one UK university. The findings are presented from the premise that university researchers are caught…

Integrating Technologies into ''Authentic'' Assessment Design: An Affordances Approach

ERIC Educational Resources Information Center

Osborne, Richard; Dunne, Elisabeth; Farrand, Paul

2013-01-01

Current pressures in higher education around student employability are driving new initiatives for change. Assessment is also a topic of debate, as it is a key driver of student behaviour, yet often falls behind other metrics in national surveys. In addition, increasing focus on digital literacies is catalysing new appreciations of what emerging…

Aerothermal modeling. Executive summary

NASA Technical Reports Server (NTRS)

Kenworthy, M. K.; Correa, S. M.; Burrus, D. L.

1983-01-01

One of the significant ways in which the performance level of aircraft turbine engines has been improved is by the use of advanced materials and cooling concepts that allow a significant increase in turbine inlet temperature level, with attendant thermodynamic cycle benefits. Further cycle improvements have been achieved with higher pressure ratio compressors. The higher turbine inlet temperatures and compressor pressure ratios with corresponding higher temperature cooling air has created a very hostile environment for the hot section components. To provide the technology needed to reduce the hot section maintenance costs, NASA has initiated the Hot Section Technology (HOST) program. One key element of this overall program is the Aerothermal Modeling Program. The overall objective of his program is to evolve and validate improved analysis methods for use in the design of aircraft turbine engine combustors. The use of such combustor analysis capabilities can be expected to provide significant improvement in the life and durability characteristics of both combustor and turbine components.

A Posteriori Study of a DNS Database Describing Super critical Binary-Species Mixing

NASA Technical Reports Server (NTRS)

Bellan, Josette; Taskinoglu, Ezgi

2012-01-01

Currently, the modeling of supercritical-pressure flows through Large Eddy Simulation (LES) uses models derived for atmospheric-pressure flows. Those atmospheric-pressure flows do not exhibit the particularities of high densitygradient magnitude features observed both in experiments and simulations of supercritical-pressure flows in the case of two species mixing. To assess whether the current LES modeling is appropriate and if found not appropriate to propose higher-fidelity models, a LES a posteriori study has been conducted for a mixing layer that initially contains different species in the lower and upper streams, and where the initial pressure is larger than the critical pressure of either species. An initially-imposed vorticity perturbation promotes roll-up and a double pairing of four initial span-wise vortices into an ultimate vortex that reaches a transitional state. The LES equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equation set uses transport properties depending on the thermodynamic variables. Unlike all LES models to date, the differential equations contain, additional to the subgrid scale (SGS) fluxes, a new SGS term that is a pressure correction in the momentum equation. This additional term results from filtering of Direct Numerical Simulation (DNS) equations, and represents the gradient of the difference between the filtered pressure and the pressure computed from the filtered flow field. A previous a priori analysis, using a DNS database for the same configuration, found this term to be of leading order in the momentum equation, a fact traced to the existence of high-densitygradient magnitude regions that populated the entire flow; in the study, models were proposed for the SGS fluxes as well as this new term. In the present study, the previously proposed constantcoefficient SGS-flux models of the a priori investigation are tested a posteriori in LES, devoid of or including, the SGS pressure correction term. The present pressure-correction model is different from, and more accurate as well as less computationally intensive than that of the a priori study. The constant-coefficient SGS-flux models encompass the Smagorinsky (SMC), in conjunction with the Yoshizawa (YO) model for the trace, the Gradient (GRC) and the Scale Similarity (SSC) models, all exercised with the a priori study constant coefficients calibrated at the transitional state. The LES comparison is performed with the filtered- and-coarsened (FC) DNS, which represents an ideal LES solution. Expectably, an LES model devoid of SGS terms is shown to be considerably inferior to models containing SGS effects. Among models containing SGS effects, those including the pressure-correction term are substantially superior to those devoid of it. The sensitivity of the predictions to the initial conditions and grid size are also investigated. Thus, it has been discovered that, additional to the atmospheric-pressure models currently used, a new model is necessary to simulate supercritical-pressure flows. This model depends on the thermodynamic characteristics of the chemical species involved.

Sodium thiopental and mean arterial pressure during cardiopulmonary bypass.

PubMed

Dabbagh, Ali; Rajaei, Samira; Ahani, Mohammad Reza

2011-06-01

Sodium thiopental is known to have a number of cardiovascular effects, but injection into the cardiopulmonary bypass reservoir has not been studied. The effect of sodium thiopental on mean arterial blood pressure during cardiopulmonary bypass was assessed in 150 patients undergoing elective coronary artery bypass grafting. Sodium thiopental 3 mg · kg(-1) was administered via the cardiopulmonary bypass reservoir. Mean arterial pressure was recorded just before drug administration and at 15-sec intervals up to 120 sec afterwards. Compared to the baseline value, mean arterial pressure was significantly higher at 30, 45, 60, and 75 sec after drug administration, and it was significantly lower at 90, 105, and 120 sec. Sodium thiopental, in addition to its effects on myocardial tissue, acts initially as a potent vasopressor, and shortly after, as a potent vasodilator.

Mixing-model Sensitivity to Initial Conditions in Hydrodynamic Predictions

NASA Astrophysics Data System (ADS)

Bigelow, Josiah; Silva, Humberto; Truman, C. Randall; Vorobieff, Peter

2017-11-01

Amagat and Dalton mixing-models were studied to compare their thermodynamic prediction of shock states. Numerical simulations with the Sandia National Laboratories shock hydrodynamic code CTH modeled University of New Mexico (UNM) shock tube laboratory experiments shocking a 1:1 molar mixture of helium (He) and sulfur hexafluoride (SF6) . Five input parameters were varied for sensitivity analysis: driver section pressure, driver section density, test section pressure, test section density, and mixture ratio (mole fraction). We show via incremental Latin hypercube sampling (LHS) analysis that significant differences exist between Amagat and Dalton mixing-model predictions. The differences observed in predicted shock speeds, temperatures, and pressures grow more pronounced with higher shock speeds. Supported by NNSA Grant DE-0002913.

Effect of initial conditions on combustion generated loads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tieszen, S.R.

1991-01-01

This analytical study examines the effect of initial thermodynamic conditions on the loads generated by the combustion of homogeneous hydrogen-air-steam mixtures. The effect of initial temperature, pressure, hydrogen concentration, and steam concentration is evaluated for two cases, (1) constant volume and (2) constant initial pressure. For each case, the Adiabatic, Isochoric, Complete Combustion (AICC), Chapman-Jouguet (CJ), and normally reflected CJ pressures are calculated for a range of hydrogen and steam concentrations representative of the entire flammable regime. For detonation loads, pressure profiles and time-histories are also evaluated in one-dimensional Cartesian geometry. The results show that to a first approximation, themore » AICC and CJ pressures are directly proportional to the initial density. Increasing the hydrogen concentration up to stoichiometric concentrations significantly increases the AICC, CJ, and reflected CJ pressures. For the constant volume case, the AICC, CJ, and reflected CJ pressures increase with increasing hydrogen concentration on the rich side of stoichiometric concentrations. For the constant initial pressure case, the AICC, CJ and reflected CJ pressures decrease with increasing hydrogen concentration on the rich side of stoichiometric values. The addition of steam decreases the AICC, CJ and reflected CJ pressures for the constant initial pressure case, but increases them for the constant volume case. For detonations, the pressure time-histories can be normalized with the AICC pressure and the reverberation time for Cartesian geometry. 35 refs., 16 figs.« less

The relationships between air exposure, negative pressure, and hemolysis.

PubMed

Pohlmann, Joshua R; Toomasian, John M; Hampton, Claire E; Cook, Keith E; Annich, Gail M; Bartlett, Robert H

2009-01-01

The purpose of this study was to describe the hemolytic effects of both negative pressure and an air-blood interface independently and in combination in an in vitro static blood model. Samples of fresh ovine or human blood (5 ml) were subjected to a bubbling air interface (0-100 ml/min) or negative pressure (0-600 mm Hg) separately, or in combination, for controlled periods of time and analyzed for hemolysis. Neither negative pressure nor an air interface alone increased hemolysis. However, when air and negative pressure were combined, hemolysis increased as a function of negative pressure, the air interface, and time. Moreover, when blood samples were exposed to air before initiating the test, hemolysis was four to five times greater than samples not preexposed to air. When these experiments were repeated using freshly drawn human blood, the same phenomena were observed, but the hemolysis was significantly higher than that observed in sheep blood. In this model, hemolysis is caused by combined air and negative pressure and is unrelated to either factor alone.

How clarinettists articulate: The effect of blowing pressure and tonguing on initial and final transients.

PubMed

Li, Weicong; Almeida, André; Smith, John; Wolfe, Joe

2016-02-01

Articulation, including initial and final note transients, is important to tasteful music performance. Clarinettists' tongue-reed contact, the time variation of the blowing pressure P¯mouth, the mouthpiece pressure, the pressure in the instrument bore, and the radiated sound were measured for normal articulation, accents, sforzando, staccato, and for minimal attack, i.e., notes started very softly. All attacks include a phase when the amplitude of the fundamental increases exponentially, with rates r ∼1000 dB s(-1) controlled by varying both the rate of increase in P¯mouth and the timing of tongue release during this increase. Accented and sforzando notes have shorter attacks (r∼1300 dB s(-1)) than normal notes. P¯mouth reaches a higher peak value for accented and sforzando notes, followed by a steady decrease for accented notes or a rapid fall to a lower, nearly steady value for sforzando notes. Staccato notes are usually terminated by tongue contact, producing an exponential decrease in sound pressure with rates similar to those calculated from the bandwidths of the bore resonances: ∼400 dB s(-1). In all other cases, notes are stopped by decreasing P¯mouth. Notes played with different dynamics are qualitatively similar, but louder notes have larger P¯mouth and larger r.

Study of the laser-induced decomposition of energetic materials at static high-pressure by time-resolved absorption spectroscopy

NASA Astrophysics Data System (ADS)

Hebert, Philippe; Saint-Amans, Charles

2013-06-01

A detailed description of the reaction rates and mechanisms occurring in shock-induced decomposition of condensed explosives is very important to improve the predictive capabilities of shock-to-detonation transition models. However, direct measurements of such experimental data are difficult to perform during detonation experiments. By coupling pulsed laser ignition of an explosive in a diamond anvil cell (DAC) with time-resolved streak camera recording of transmitted light, it is possible to make direct observations of deflagration phenomena at detonation pressure. We have developed an experimental set-up that allows combustion front propagation rates and time-resolved absorption spectroscopy measurements. The decomposition reactions are initiated using a nanosecond YAG laser and their kinetics is followed by time-resolved absorption spectroscopy. The results obtained for two explosives, nitromethane (NM) and HMX are presented in this paper. For NM, a change in reactivity is clearly seen around 25 GPa. Below this pressure, the reaction products are essentially carbon residues whereas at higher pressure, a transient absorption feature is first observed and is followed by the formation of a white amorphous product. For HMX, the evolution of the absorption as a function of time indicates a multi-step reaction mechanism which is found to depend on both the initial pressure and the laser fluence.

Time course of blood pressure changes immediately after maximal exercise.

PubMed

Nakahara, H; Miyamoto, T; Nakanishi, Y; Kinoshita, H

2006-12-01

The aim of this study was to investigate the effect of exhaustive exercise on the time course of arterial blood pressure (BP) and heart rate (HR) during upright resting (inactive) and loadless pedaling (active) recovery from a bicycle exercise to exhaustion. The subjects were 11 healthy normotensive males. Systolic, diastolic and mean BP, and HR were recorded every 20 s for the initial 6 min of the recovery period. The time course of all BP measures during inactive and active recovery was characterized by a marked and sudden drop during the initial 20-s period, followed by a quick rise. This was followed by a gradual decline till the end of the recovery period. The time course of HR recovery, on the other hand, exhibited a smooth decline without the initial drop. With active recovery, the initial drop of diastolic and mean BP was less than the inactive recovery. After the 20 s period, the diastolic BP and HR were kept slightly higher with the active recovery than the inactive recovery. A sudden drop of the BP occurred at the initial recovery period of postcycle exercise to exhaustion though HR did not show such a change. The initial BP drop could be attenuated by the actively pedaling the cycle without load.

A systematic study of atmospheric pressure chemical vapor deposition growth of large-area monolayer graphene.

PubMed

Liu, Lixin; Zhou, Hailong; Cheng, Rui; Chen, Yu; Lin, Yung-Chen; Qu, Yongquan; Bai, Jingwei; Ivanov, Ivan A; Liu, Gang; Huang, Yu; Duan, Xiangfeng

2012-01-28

Graphene has attracted considerable interest as a potential material for future electronics. Although mechanical peel is known to produce high quality graphene flakes, practical applications require continuous graphene layers over a large area. The catalyst-assisted chemical vapor deposition (CVD) is a promising synthetic method to deliver wafer-sized graphene. Here we present a systematic study on the nucleation and growth of crystallized graphene domains in an atmospheric pressure chemical vapor deposition (APCVD) process. Parametric studies show that the mean size of the graphene domains increases with increasing growth temperature and CH 4 partial pressure, while the density of domains decreases with increasing growth temperature and is independent of the CH 4 partial pressure. Our studies show that nucleation of graphene domains on copper substrate is highly dependent on the initial annealing temperature. A two-step synthetic process with higher initial annealing temperature but lower growth temperature is developed to reduce domain density and achieve high quality full-surface coverage of monolayer graphene films. Electrical transport measurements demonstrate that the resulting graphene exhibits a high carrier mobility of up to 3000 cm 2 V -1 s -1 at room temperature.

Infrared Absorption Spectroscopy and Chemical Kinetics of Free Radicals, Final Technical Report

DOE R&D Accomplishments Database

Curl, Robert F.; Glass, Graham P.

2004-11-01

This research was directed at the detection, monitoring, and study of the chemical kinetic behavior by infrared absorption spectroscopy of small free radical species thought to be important intermediates in combustion. Work on the reaction of OH with acetaldehyde has been completed and published and work on the reaction of O({sup 1}D) with CH{sub 4} has been completed and submitted for publication. In the course of our investigation of branching ratios of the reactions of O({sup 1}D) with acetaldehyde and methane, we discovered that hot atom chemistry effects are not negligible at the gas pressures (13 Torr) initially used. Branching ratios of the reaction of O({sup 1}D) with CH{sub 4} have been measured at a tenfold higher He flow and fivefold higher pressure.

Improving the Quality of Higher Education in Central Europe: Approach Based on GAP Analysis

ERIC Educational Resources Information Center

Hrnciar, Miroslav; Madzík, Peter

2013-01-01

A growing social pressure on addressing the issues of quality in administration of educational institutions has resulted in various national and international initiatives focused on development of recommendations and procedures for assurance of quality of education. The topic is getting more urgent in the period of global recession when the…

High-resolution three-dimensional 19F-magnetic resonance imaging of rat lung in situ: evaluation of airway strain in the perfluorocarbon-filled lung.

PubMed

Weigel, Julia K; Steinmann, Daniel; Emerich, Philipp; Stahl, Claudius A; v Elverfeldt, Dominik; Guttmann, Josef

2011-02-01

Perfluorocarbons (PFC) are biologically and chemically inert fluids with high oxygen and CO(2) carrying capacities. Their use as liquid intrapulmonary gas carriers during liquid ventilation has been investigated. We established a method of high resolution 3D-(19)F-MRI of the totally PFC-filled lung. The goal of this study was to investigate longitudinal and circumferential airway strain in the setting of increasing airway pressures on 3D-(19)F-MR images of the PFC-filled lung. Sixteen female Wistar rats were euthanized and the liquid perfluorocarbon FC-84 instilled into their lungs. 3D-(19)F-MRI was performed at various intrapulmonary pressures. Measurements of bronchial length and cross-sectional area were obtained from transversal 2D images for each pressure range. Changes in bronchial area were used to determine circumferential strain, while longitudinal strain was calculated from changes in bronchial length. Our method of 3D-(19)F-MRI allowed clear visualization of the great bronchi. Longitudinal strain increased significantly up to 31.1 cmH(2)O. The greatest strain could be found in the range of low airway pressures. Circumferential strain increased strongly with the initial pressure rise, but showed no significant changes above 10.4 cmH(2)O. Longitudinal strain was generally higher in distal airways, while circumferential strain showed no difference. Analysis of mechanical characteristics showed that longitudinal and circumferential airway expansion occurred in an anisotropic fashion. Whereas longitudinal strain still increased with higher pressures, circumferential strain quickly reached a 'strain limit'. Longitudinal strain was higher in distal bronchi, as dense PFCs gravitate to dependent, in this case to dorso-basal parts of the lung, acting as liquid positive end expiratory pressure.

High Prevalence of Hypertension Among Collegiate Football Athletes

PubMed Central

Karpinos, Ashley Rowatt; Roumie, Christianne L.; Nian, Hui; Diamond, Alex B.; Rothman, Russell L.

2014-01-01

Background The prevalence of hypertension among collegiate football athletes is not well described. Methods and Results A retrospective cohort of all male athletes who participated in varsity athletics at a National Collegiate Athletic Association Division I university between 1999–2012 was examined through chart review. Mandatory annual preparticipation physical examinations included blood pressure, body mass index, medication use, and supplement use. Prevalence of hypertension was compared between football and non-football athletes. A mixed-effects linear regression model examined change in blood pressure over time. 636 collegiate athletes, including 323 football players, were identified. In the initial year of athletic participation, 19.2% of football athletes had hypertension and 61.9% had prehypertension. The prevalence of hypertension was higher among football athletes than non-football athletes in their initial (19.2% vs. 7.0%, P< 0.001) and final (19.2% vs. 10.2%, P=0.001) years of athletic participation. In adjusted analyses, the odds of hypertension was higher among football athletes in the initial year (AOR 2.28, 95% CI 1.21 to 4.30) but not the final year (AOR 1.25, 95% CI 0.69 to 2.28). Over the course of their collegiate career, football athletes had an annual decrease in systolic blood pressure (−0.82 mmHg, P=0.002), while non-football athletes did not (0.18 mmHg, P=0.58). Conclusions Hypertension and prehypertension were common among collegiate football athletes, and football athletes were more likely to have hypertension than male non-football athletes. This presents a potential cardiovascular risk in a young population of athletes. Strategies for increasing awareness, prevention and treatment are needed. PMID:24221829

New tip design and shock wave pattern of electrohydraulic probes for endoureteral lithotripsy.

PubMed

Vorreuther, R

1993-02-01

A new tip design of a 3.3F electrohydraulic probe for endoureteral lithotripsy was evaluated in comparison to a regular probe. The peak pressure, as well as the slope of the shock front, depend solely on the voltage. Increasing the capacity leads merely to broader pulses. A laser-like short high-pressure pulse has a greater impact on stone disintegration than a corresponding broader low-pressure pulse of the same energy. Using the regular probe, only positive pressures were obtained. Pressure distribution around the regular tip was approximately spherical, whereas the modified probe tip "beamed" the shock wave to a great extent. In addition, a negative-pressure half-cycle was added to the initial positive peak pressure, which resulted in a higher maximal pressure amplitude. The directed shock wave had a greater depth of penetration into a model stone. Thus, the ability of the new probe to destroy harder stones especially should be greater. The trauma to the ureter was reduced when touching the wall tangentially. No difference in the effect of the two probes was seen when placing the probe directly on the mucosa.

High pressure studies of A2Mo3O12 negative thermal expansion materials (A2=Al2, Fe2, FeAl, AlGa)

NASA Astrophysics Data System (ADS)

Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong; Lind, Cora

2016-05-01

High pressure powder X-ray diffraction studies of several A2Mo3O12 materials (A2=Al2, Fe2, FeAl, and AlGa) were conducted up to 6-7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga2Mo3O12 suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations.

Static Longitudinal Stability of a Rocket Vehicle Having a Rear-Facing Step Ahead of the Stabilizing Fins

NASA Technical Reports Server (NTRS)

Keynton, Robert J.

1961-01-01

Tests were conducted at Mach numbers of 3.96 and 4.65 in the Langley Unitary Plan wind tunnel to determine the static longitudinal stability characteristics of a fin-stabilized rocket-vehicle configuration which had a rearward facing step located upstream of the fins. Two fin sizes and planforms, a delta and a clipped delta, were tested. The angle of attack was varied from 6 deg to -6 deg and the Reynolds number based on model 6 length was about 10 x 10. The configuration with the larger fins (clipped delta) had a center of pressure slightly rearward of and an initial normal-force-curve slope slightly higher than that of the configuration with the smaller fins (delta) as would be expected. Calculations of the stability parameters gave a slightly lower initial slope of the normal-force curve than measured data, probably because of boundary-layer separation ahead of the step. The calculated center of pressure agreed well with the measured data. Measured and calculated increments in the initial slope of the normal-force curve and in the center of pressure, due to changing fins, were in excellent agreement indicating that separated flow downstream of the step did not influence flow over the fins. This result was consistent with data from schlieren photographs.

Implosion-driven technique to create fast shockwaves in high-density gas

NASA Astrophysics Data System (ADS)

Serge, Matthew; Loiseau, Jason; Huneault, Justin; Szirti, Daniel; Higgins, Andrew; Tanguay, Vincent

2012-03-01

Pressurized tubes surrounded by either one or two layers (separated by a secondary tube) of sensitized nitromethane and encased in a thick-walled tube (the tamper) were imploded. The distance between the detonation wave in the explosive and shock wave in the innermost tube were measured (the standoff). A simple model based on hoop stress and acoustic interactions between the tubing was developed and used to predict the standoff distance. At low initial pressures (on the order of 7MPa), results indicate that the secondary tube and two layers of explosive did not prove to significantly increase the standoff. However, at higher pressures (on the order of 10 MPa), standoff was noticeably greater when the secondary tube was inserted between the pressurized tube and the tamper. The measured values are in reasonable agreement with the predictions of the model.

Performance of a green propellant thruster with discharge plasma

NASA Astrophysics Data System (ADS)

Shindo, Takahiro; Wada, Asato; Maeda, Hiroshi; Watanabe, Hiroki; Takegahara, Haruki

2017-02-01

A discharge plasma was applied to initiate the combustion of a hydroxylammonium nitrate-based propellant as a substitute for the catalysts that are typically employed. The resulting thrust and thrust-to-power ratio during short interval firing tests as well as the chamber pressure with a single pulse discharge were evaluated. A 1.5-s firing test generated a maximum thrust of 322 mN along with a thrust-to-power ratio of 0.95 mN/W. During the single-pulse discharge trials, pulsed discharge capacitor energies of 5.4, 10.8, and 16.4 J were assessed, and the maximum chamber pressure was found to increase as the energy was raised. The maximum chamber pressures varied widely between experimental trials, and a 16.4-J energy value resulted in the highest chamber pressure of over 1 MPaG. The time spans between the pulsed discharge and the peak chamber pressure were in the range of 1-2 ms, representing a chamber pressure increase rate much higher than those obtained with standard catalysts.

Temperature and seeding effects on the precipitation of scorodite from sulfate solutions under atmospheric-pressure conditions

NASA Astrophysics Data System (ADS)

Singhania, Shalabh; Wang, Qiankun; Filippou, Dimitrios; Demopoulos, George P.

2005-06-01

Arsenic is a major contaminant in the nonferrous extractive metallurgy. In the past 20 years, many studies have shown that it can be precipitated as relatively stable crystalline scorodite (FeAsO4·2H2O) by precipitation under ambient or elevated pressures. In the present study, an extensive program of scorodite precipitation tests under ambient pressure has shown that the rate of scorodite formation increases dramatically by a small increase in temperature from 85 °C to 100 °C. The beneficial effects of temperature are attributed to the higher thermodynamic stability of scorodite at elevated temperatures, but also to higher rates of secondary nuclei formation and crystal growth. In any case, irrespective of the precipitation temperature, the leachability of all scorodite precipitates observed in toxicity characterization leaching procedure (TCLP) tests is below 5 mg/L As. Another parameter examined in this study was seeding. It was observed that the higher the initial concentration of seed, the faster the precipitation. Precipitation of well-crystallized scorodite can be effected equally well on heterogeneous seed such as hematite (Fe2O3) or gypsum (CaSO4·2H2O) added externally or formed in situ.

Effects of densification of precursor pellets on microstructures and critical current properties of YBCO melt-textured bulks

NASA Astrophysics Data System (ADS)

Setoyama, Yui; Shimoyama, Jun-ichi; Motoki, Takanori; Kishio, Kohji; Awaji, Satoshi; Kon, Koichi; Ichikawa, Naoki; Inamori, Satoshi; Naito, Kyogo

2016-12-01

Effects of densification of precursor disks on the density of residual voids and critical current properties for YBCO melt-textured bulk superconductors were systematically investigated. Six YBCO bulks were prepared from precursor pellets with different initial particle sizes of YBa2Cu3Oy (Y123) powder and applied pressures for pelletization. It was revealed that use of finer Y123 powder and consolidation using cold-isostatic-pressing (CIP) with higher pressures result in reduction of residual voids at inner regions of bulks and enhance Jc especially under low fields below the second peak.

Technology development for deployable aerodynamic decelerators at Mars

NASA Astrophysics Data System (ADS)

Masciarelli, James P.

2002-01-01

Parachutes used for Mars landing missions are only certified for deployment at Mars behind blunt bodies flying at low angles of attack, Mach numbers up to 2.2, and dynamic pressures of up to 800 Pa. NASA is currently studying entry vehicle concepts for future robotic missions to Mars that would require parachutes to be deployed at higher Mach numbers and dynamic pressures. This paper demonstrates the need for expanding the parachute deployment envelope, and describes a three-phase technology development activity that has been initiated to address the need. The end result of the technology development program will be a aerodynamic decelerator system that can be deployed at Mach numbers of up to 3.1 and dynamic pressures of up to 1400 Pa. .

Technology Development for Deployable Aerodynamic Decelerators at Mars

NASA Technical Reports Server (NTRS)

Masciarelli, James P.

2002-01-01

Parachutes used for Mars landing missions are only certified for deployment at Mars behind blunt bodies flying at low angles of attack, Mach numbers up to 2.2, and dynamic pressures of up to 800 Pa. NASA is currently studying entry vehicle concepts for future robotic missions to Mars that would require parachutes to be deployed at higher Mach numbers and dynamic pressures. This paper demonstrates the need for expanding the parachute deployment envelope, and describes a three-phase technology development activity that has been initiated to address the need. The end result of the technology development program will be a aerodynamic decelerator system that can be deployed at Mach numbers of up to 3.1 and dynamic pressures of up to 1400 Pa.

Super-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Chen, Lee Chuin; Rahman, Md Matiur; Hiraoka, Kenzo

2013-03-01

Super-atmospheric pressure chemical ionization (APCI) mass spectrometry was performed using a commercial mass spectrometer by pressurizing the ion source with compressed air up to 7 atm. Similar to typical APCI source, reactant ions in the experiment were generated with corona discharge using a needle electrode. Although a higher needle potential was necessary to initiate the corona discharge, discharge current and detected ion signal were stable at all tested pressures. A Roots booster pump with variable pumping speed was installed between the evacuation port of the mass spectrometer and the original rough pumps to maintain a same pressure in the first pumping stage of the mass spectrometer regardless of ion source pressure. Measurement of gaseous methamphetamine and research department explosive showed an increase in ion intensity with the ion source pressure until an optimum pressure at around 4-5 atm. Beyond 5 atm, the ion intensity decreased with further increase of pressure, likely due to greater ion losses inside the ion transport capillary. For benzene, it was found that besides molecular ion and protonated species, ion due to [M + 2H](+) which was not so common in APCI, was also observed with high ion abundance under super-atmospheric pressure condition. Copyright © 2013 John Wiley & Sons, Ltd.

Equivalence of Nasal and Oronasal Masks during Initial CPAP Titration for Obstructive Sleep Apnea Syndrome

PubMed Central

Teo, Ming; Amis, Terence; Lee, Sharon; Falland, Karina; Lambert, Stephen; Wheatley, John

2011-01-01

Study Objective: Continuous positive airway pressure (CPAP) titration studies are commonly performed using a nasal mask but some patients may prefer a full-face or oronasal mask. There is little evidence regarding the equivalence of different mask interfaces used to initiate treatment. We hypothesized that oronasal breathing when using an oronasal mask increases upper airway collapsibility and that a higher pressure may be required to maintain airway patency. We also assessed patient preferences for the 2 mask interfaces. Design: Prospective, randomized, cross-over design with 2 consecutive CPAP titration nights. Setting: Accredited laboratory in a university hospital. Patients or Participants: Twenty-four treatment-naive subjects with obstructive sleep apnea syndrome and respiratory disturbance index of greater than 15 events per hour. Interventions: CPAP titration was performed using an auto-titrating machine with randomization to a nasal or oronasal mask, followed by a second titration night using the alternate mask style. Measurements and Results: There was no significant difference in the mean pressures determined between nasal and oronasal masks, although 43% of subjects had nasal-to-oronasal mask-pressure differences of 2 cm H2O or more. Residual respiratory events, arousals, and measured leak were all greater with the oronasal mask. Seventy-nine percent of subjects preferred the nasal mask. Conclusions: Patients with obstructive sleep apnea syndrome can generally switch between nasal and oronasal masks without changing machine pressure, although there are individual differences that may be clinically significant. Measured leak is greater with the oronasal mask. Most patients with obstructive sleep apnea syndrome prefer a nasal mask as the interface for initiation of CPAP. Clinical Trial Registration: Australian New Zealand Clinical Trials Registry (ANZCTR). ACTRN: ACTRN12611000243910. URL: http://www.ANZCTR.org.au/ACTRN12611000243910.aspx Citation: Teo M; Amis T; Lee S; Falland K; Lambert S; Wheatley J. Equivalence of nasal and oronasal masks during initial CPAP titration for obstructive sleep apnea syndrome. SLEEP 2011;34(7):951-955. PMID:21731145

The Pieper-Zulkowski pressure ulcer knowledge test.

PubMed

Pieper, Barbara; Zulkowski, Karen

2014-09-01

To describe the development and initial testing of the Pieper-Zulkowski Pressure Ulcer Knowledge Test (PZ-PUKT). Cross-sectional, instrument testing. Hospital association pressure ulcer educational program conference. Pressure ulcer research and guidelines from the last 5 years were examined for test item content. The initial PZ-PUKT had 115 items; response options were "true," "false," and "don't know." Registered nurses (N = 108) were randomly divided into 2 groups to take either the 60 prevention/risk and staging items or the 55 wound description items. Analyses of these responses resulted in 72 items, which were administered in total to a second cohort of 98 nurses for reliability. Cronbach's α was .80 for the 72-item PZ-PUKT. Cronbach's α values for the subscales were as follows: staging, .67; wound description, .64; and prevention/risk, .56. The mean correct scores were as follows: total, 80%; prevention, 77%; staging, 86%; and wound description, 77%. Nurses with wound care certification scored significantly higher on the PZ-PUKT than did nurses with other clinical certifications or with nurses who lacked certification. The PZ-PUKT has updated content about pressure ulcer prevention/risk, staging, and wound description. Reliability values are highest for the total test. Further use of the instrument in diverse settings will add to reliability testing and may provide direction for determination of a passing cutoff score.

Equivalence of nasal and oronasal masks during initial CPAP titration for obstructive sleep apnea syndrome.

PubMed

Teo, Ming; Amis, Terence; Lee, Sharon; Falland, Karina; Lambert, Stephen; Wheatley, John

2011-07-01

Continuous positive airway pressure (CPAP) titration studies are commonly performed using a nasal mask but some patients may prefer a full-face or oronasal mask. There is little evidence regarding the equivalence of different mask interfaces used to initiate treatment. We hypothesized that oronasal breathing when using an oronasal mask increases upper airway collapsibility and that a higher pressure may be required to maintain airway patency. We also assessed patient preferences for the 2 mask interfaces. Prospective, randomized, cross-over design with 2 consecutive CPAP titration nights. Accredited laboratory in a university hospital. Twenty-four treatment-naive subjects with obstructive sleep apnea syndrome and respiratory disturbance index of greater than 15 events per hour. CPAP titration was performed using an auto-titrating machine with randomization to a nasal or oronasal mask, followed by a second titration night using the alternate mask style. There was no significant difference in the mean pressures determined between nasal and oronasal masks, although 43% of subjects had nasal-to-oronasal mask-pressure differences of 2 cm H(2)O or more. Residual respiratory events, arousals, and measured leak were all greater with the oronasal mask. Seventy-nine percent of subjects preferred the nasal mask. Patients with obstructive sleep apnea syndrome can generally switch between nasal and oronasal masks without changing machine pressure, although there are individual differences that may be clinically significant. Measured leak is greater with the oronasal mask. Most patients with obstructive sleep apnea syndrome prefer a nasal mask as the interface for initiation of CPAP. Australian New Zealand Clinical Trials Registry (ANZCTR). ACTRN: ACTRN12611000243910. URL: http://www.ANZCTR.org.au/ACTRN12611000243910.aspx

Decrepitation and crack healing of fluid inclusions in San Carlos olivine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wanamaker, B.J.; Wong, Tengfong; Evans, B.

1990-09-10

Fluid inclusions break, or decrepitate, when the fluid pressure exceeds the least principal lithostatic stress by a critical amount. After decrepitation, excess fluid pressure is relaxed, resulting in crack arrest; subsequently, crack healing may occur. The authors developed a linear elastic fracture mechanics model to analyze new data on decrepitation and crack arrest in San Carlos Olivine, compared the model with previous fluid inclusion investigations, and used it to interpret some natural decrepitation microstructures. The common experimental observation that smaller inclusions may sustain higher internal fluid pressures without decrepitating may be rationalized by assuming that flaws associated with the inclusionmore » scale with the inclusion size. According to the model, the length of the crack formed by decrepitation depends on the lithostatic pressure at the initiation of cracking, the initial sizes of the flaw and the inclusion, and the critical stress intensity factor. Further experiments show that microcracks in San Carlos olivine heal within several days at 1,280 to 1,400{degree}C; healing rates depend on the crack geometry, temperature, and chemistry of the buffering gas. The regression distance of the crack tip during healing can be related to time through a power law with exponent n = 0.6. Chemical changes which become apparent after extremely long heat-treatments significantly affect the healing rates. Many of the inclusions in the San Carlos xenoliths stretched, decrepitated, and finally healed during uplift. The crack arrest model indicates that completely healed cracks had an initial fluid pressure of the order of 1 GPa. Using the crack arrest model and the healing kinetics, they estimate the ascent rate of these xenoliths to be between 0.001 and 0.1 m/s.« less

Effect of increased pressure during pulsatile pump perfusion of deceased donor kidneys in transplantation.

PubMed

Patel, S K; Pankewycz, O G; Weber-Shrikant, E; Zachariah, M; Kohli, R; Nader, N D; Laftavi, M R

2012-09-01

Pulsatile pump perfusion of potential kidneys for transplantation is known to decrease the rate of delayed graft function (DGF) and improve their 1-year survival. Flow and resistance parameters are often used to determine the suitability of kidneys for transplantation. Kidneys with low flow rates are often subjected to higher pressures to improve flow. This study evaluated the effect of higher pump pressures on posttransplant renal function. We performed a retrospective analysis of 73 deceased donor kidneys preserved using pump perfusion (LifePort) at our center between May 2006 and September 2009. We calculated the mean pump pressure (MP) for the duration of perfusion of each kidney, using systolic pressure (SP) and diastolic pressure (DP) readings with the following formula: (MP = DP + 1/3 (SP - DP). The kidneys were divided into a low (LP; n = 49) and a high-pressure group (HP; n = 24) based on a MP cutoff value of 23 mm Hg. The two groups were then compared for differences in perfusion dynamics and primary endpoints including DGF and 1-year graft survival. Statistical analysis was performed using paired Student t test and chi-square analysis. The two groups were comparable for donor age, extended criteria, sensitization, and cold ischemic times. They differed significantly in higher initial (0.65 ± 0.4 versus 0.4 ± 0.2, P = .01), average (0.25 ± 0.08 versus 0.18 ± 0.06, P = .0006), and terminal resistance (0.21 ± 0.07 versus 0.17 ± 0.06, P = .008) of HP versus LP kidneys. Flow rates were comparable between the two groups. DGF was higher in HP kidneys (75% versus 40%, P = .006) with similar 1-year graft survival (87.5% versus 89%, P = .7). Perfusate flow through a kidney can be improved by increasing pressure settings to overcome elevated resistance. This maneuver was not associated with a lower rate of DGF after transplantation. One-year graft survival remained unaffected. Copyright © 2012 Elsevier Inc. All rights reserved.

Pressure effects on the thermal stability of SiC fibers

NASA Technical Reports Server (NTRS)

Jaskowiak, Martha H.; Dicarlo, James A.

1986-01-01

Commercially available polymer derived SiC fibers were treated at temperatures from 1000 to 2200 C in vacuum and argon gas pressure of 1 and 1360 atm. Effects of gas pressure on the thermal stability of the fibers were determined through property comparison between the pressure treated fibers and vacuum treated fibers. Investigation of the thermal stability included studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 1360 atm argon gas treatment was found to shift the onset of fiber weight loss from 1200 to above 1500 C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high pressure treatments. Additional heat treatment in 1 atm argon of the fibers initially treated at 1360 atm argon caused further weight loss and tensile strength degradation, thus indicating that high pressure inert gas conditions would be effective only in delaying fiber strength degradation. However, if the high gas pressure could be maintained throughout composite fabrication, then the composites could be processed at higher temperatures.

The Relationships between Air Exposure, Negative Pressure and Hemolysis

PubMed Central

Pohlmann, Joshua R.; Toomasian, John M.; Hampton, Claire E.; Cook, Keith E.; Annich, Gail M.; Bartlett, Robert H.

2013-01-01

The purpose of this study was to describe the hemolytic effects of both negative pressure and an air-blood interface independently and in combination in an in-vitro static blood model. Samples of fresh ovine or human blood (5 mL) were subjected to a bubbling air interface (0–100 mL/min) or negative pressure (0–600 mmHg) separately, or in combination, for controlled periods of time, and analyzed for hemolysis. Neither negative pressure nor an air interface alone increased hemolysis. However, when air and negative pressure were combined, hemolysis increased as a function of negative pressure, the air interface, and time. Moreover, when blood samples were exposed to air prior to initiating the test, hemolysis was 4–5 times greater than samples not pre-exposed to air. When these experiments were repeated using freshly drawn human blood the same phenomena were observed, but the hemolysis was significantly higher than that observed in sheep blood. In this model, hemolysis is caused by combined air and negative pressure and is unrelated to either factor alone. PMID:19730004

Thermodynamic Calculations of Hydrogen-Oxygen Detonation Parameters for Various Initial Pressures

NASA Technical Reports Server (NTRS)

Bollinger, Loren E.; Edse, Rudolph

1961-01-01

Composition, temperature, pressure and density behind a stable detonation wave and its propagation rate have been calculated for seven hydrogen-oxygen mixture at 1, 5, 25 and 100 atm initial pressure, and at an initial temperature of 40C. For stoichiometric mixtures that calculations also include an initial temperature of 200C. According to these calculations the detonation velocities of hydrogen-oxygen mixtures increase with increasing initial pressure, but decrease slightly when the initial temperature is raised from 40 to 200 C. The calculated detonation velocities agree satisfactorily with values determined experimentally. These values will be published in the near future.

Temperature and pressure influence on maximum rates of pressure rise during explosions of propane-air mixtures in a spherical vessel.

PubMed

Razus, D; Brinzea, V; Mitu, M; Movileanu, C; Oancea, D

2011-06-15

The maximum rates of pressure rise during closed vessel explosions of propane-air mixtures are reported, for systems with various initial concentrations, pressures and temperatures ([C(3)H(8)]=2.50-6.20 vol.%, p(0)=0.3-1.3 bar; T(0)=298-423 K). Experiments were performed in a spherical vessel (Φ=10 cm) with central ignition. The deflagration (severity) index K(G), calculated from experimental values of maximum rates of pressure rise is examined against the adiabatic deflagration index, K(G, ad), computed from normal burning velocities and peak explosion pressures. At constant temperature and fuel/oxygen ratio, both the maximum rates of pressure rise and the deflagration indices are linear functions of total initial pressure, as reported for other fuel-air mixtures. At constant initial pressure and composition, the maximum rates of pressure rise and deflagration indices are slightly influenced by the initial temperature; some influence of the initial temperature on maximum rates of pressure rise is observed only for propane-air mixtures far from stoichiometric composition. The differentiated temperature influence on the normal burning velocities and the peak explosion pressures might explain this behaviour. Copyright © 2011 Elsevier B.V. All rights reserved.

[Blood pressure and sleep apnoea hypopnoea syndrome in workers. STOP-Bang test versus Epworth test].

PubMed

Vicente-Herrero, M T; Capdevila-García, L; Bellido-Cambrón, M C; Ramírez-Iñiguez de la Torre, M V; Lladosa-Marco, S

OSAHS is associated with an increased risk of cardiovascular disease and stroke. Arterial hypertension is a key risk factor to consider due to its impact on health. Cross-sectional study carried out on Spanish public service workers. The nocturnal apnoea risk using the Epworth and STOP-Bang questionnaires and their influence on the mean values of blood pressure are assessed. The detection of OSAHS using the Epworth test and, particularly with the STOP-Bang shows a significant relationship with the mean values of blood pressure, with differences between both questionnaires. The Epworth and STOP-Bang questionnaires are useful for the initial detection of OSAHS and a higher prevalence of high blood pressure. Both can be used in screening procedures in occupational health. Copyright © 2017 SEH-LELHA. Publicado por Elsevier España, S.L.U. All rights reserved.

Extracellular Polymeric Matrix Production and Relaxation under Fluid Shear and Mechanical Pressure in Staphylococcus aureus Biofilms.

PubMed

Hou, Jiapeng; Veeregowda, Deepak H; van de Belt-Gritter, Betsy; Busscher, Henk J; van der Mei, Henny C

2017-10-20

The viscoelasticity of a biofilm's EPS (extracellular-polymeric-substance) matrix conveys protection against mechanical challenges, but adaptive responses of biofilm inhabitants to produce EPS are not well known. Here, we compare the response of a biofilm of an EPS producing (ATCC 12600) and non-EPS producing (5298) Staphylococcus aureus strain to fluid shear and mechanical challenge. Confocal-Laser-Scanning-Microscopy confirmed absence of calcofluorwhite-stainable EPS in biofilms of S. aureus 5298. ATR-FTIR spectroscopy combined with tribometry indicated that the polysaccharide production per bacterium in the initial adhering layer was higher during growth at high shear than at low shear and this increased EPS production extended to entire biofilms, as indicated by tribometrically measured coefficients of friction (CoF). CoFs of biofilms grown under high fluid shear were higher than when grown under low shear, likely due to wash-off of polysaccharides. Measurement of a biofilm's CoF implies application of mechanical pressure that yielded an immediate increase in polysaccharide band area of S. aureus ATCC 12600 biofilms due to their compression that decreased after relieving pressure to the level observed prior to mechanical pressure. For biofilms grown under high shear, this coincided with a higher %whiteness in Optical-Coherence-Tomography-images indicative of water outflow, returning back into the biofilm during stress relaxation. Biofilms grown under low shear however, were stimulated during tribometry to produce EPS, also after stress relieve. Knowledge of factors that govern EPS production and water flow in biofilms will allow better control of biofilms under mechanical challenge and understanding of the barrier properties of biofilms toward antimicrobial penetration. IMPORTANCE Adaptive responses of biofilm inhabitants in nature to environmental challenges such as fluid shear and mechanical pressure, often involve EPS production with the aim of protecting biofilm inhabitants. EPS can assist biofilm bacteria to remain attached or impede antimicrobial penetration. The tribochemist is a recently introduced instrument, allowing to study initially adhering bacteria to a Germanium crystal using ATR-FTIR spectroscopy, while simultaneously allowing measurement of the coefficient of friction of a biofilm, serving as an indicator of the EPS content of a biofilm. EPS production can be stimulated by both fluid shear during growth and mechanical pressure, while increased EPS production can continue after pressure relaxation of the biofilm. Since EPS is pivotal in the protection of biofilm inhabitants against mechanical and chemical challenges, knowledge the factors that make biofilm inhabitants decide to produce EPS as provided in this study, are important for the development of biofilm control measures. Copyright © 2017 American Society for Microbiology.

Observations over Hurricanes from the Ozone Monitoring Instrument

NASA Technical Reports Server (NTRS)

Joiner, J.; Vasilkov, A.; Yang, K.; Bhartia, P. K.

2006-01-01

There is an apparent inconsistency between the total column ozone derived from the total ozone mapping spectrometer (TOMS) and aircraft observations within the eye region of tropical cyclones. The higher spectral resolution, coverage, and sampling of the ozone monitoring instrument (OMI) on NASA s Aura satellite as compared with TOMS allows for improved ozone retrievals by including estimates of cloud pressure derived simultaneously using the effects of rotational Raman scattering. The retrieved cloud pressures from OM1 are more appropriate than the climatological cloud-top pressures based on infrared measurements used in the TOMS and initial OM1 algorithms. We find that total ozone within the eye of hurricane Katrina is significantly overestimated when we use climatological cloud pressures. Using OMI-retrieved cloud pressures, total ozone in the eye is similar to that in the surrounding area. The corrected total ozone is in better agreement with aircraft measurements that imply relatively small or negligible amounts of stratospheric intrusion into the eye region of tropical cyclones.

Influence of slope steepness, foot position and turn phase on plantar pressure distribution during giant slalom alpine ski racing

PubMed Central

Falda-Buscaiot, Thomas; Hintzy, Frédérique; Rougier, Patrice; Lacouture, Patrick; Coulmy, Nicolas

2017-01-01

The purpose of this study was to investigate the evolution of ground reaction force during alpine skiing turns. Specifically, this study investigated how turn phases and slope steepness affected the whole foot normal GRF pattern while performing giant slalom turns in a race-like setting. Moreover, the outside foot was divided into different plantar regions to see whether those parameters affected the plantar pressure distribution. Eleven skiers performed one giant slalom course at race intensity. Runs were recorded synchronously using a video camera in the frontal plane and pressure insoles under both feet’s plantar surface. Turns were divided according to kinematic criteria into four consecutive phases: initiation, steering1, steering2 and completion; both steering phases being separated by the gate passage. Component of the averaged Ground Reaction Force normal to the ski’s surface(nGRF¯, /BW), and Pressure Time Integral relative to the entire foot surface (relPTI, %) parameters were calculated for each turn phases based on plantar pressure data. Results indicated that nGRF¯ under the total foot surface differed significantly depending on the slope (higher in steep sections vs. flat sections), and the turn phase (higher during steering2 vs. three other phases), although such modifications were observable only on the outside foot. Moreover, nGRF¯ under the outside foot was significantly greater than under the inside foot.RelPTI under different foot regions of the outside foot revealed a global shift from forefoot loading during initiation phase, toward heel loading during steering2 phase, but this was dependent on the slope studied. These results suggest a differentiated role played by each foot in alpine skiing turns: the outside foot has an active role in the turning process, while the inside foot may only play a role in stability. PMID:28472092

Clinical practices, complications, and mortality in neurological patients with acute severe hypertension: the Studying the Treatment of Acute hyperTension registry.

PubMed

Mayer, Stephan A; Kurtz, Pedro; Wyman, Allison; Sung, Gene Y; Multz, Alan S; Varon, Joseph; Granger, Christopher B; Kleinschmidt, Kurt; Lapointe, Marc; Peacock, W Frank; Katz, Jason N; Gore, Joel M; O'Neil, Brian; Anderson, Frederick A

2011-10-01

To determine the demographic and clinical features, hospital complications, and predictors of 90-day mortality in neurologic patients with acute severe hypertension. Studying the Treatment of Acute hyperTension (STAT) was a multicenter (n=25) observational registry of adult critical care patients with severe hypertension treated with intravenous therapy. Emergency department or intensive care unit. A qualifying blood pressure measurement>180 mm Hg systolic or >110 mm Hg diastolic (>140/90 mm Hg for subarachnoid hemorrhage) was required for inclusion in the STAT registry. Patients with a primary neurologic admission diagnosis were included in the present analysis. All patients were treated with at least one parenteral (bolus or continuous infusion) antihypertensive agent. Of 1,566 patients included in the STAT registry, 432 (28%) had a primary neurologic diagnosis. The most common diagnoses were subarachnoid hemorrhage (38%), intracerebral hemorrhage (31%), and acute ischemic stroke (18%). The most common initial drug was labetalol (48%), followed by nicardipine (15%), hydralazine (15%), and sodium nitroprusside (13%). Mortality at 90 days was substantially higher in neurologic than in non-neurologic patients (24% vs. 6%, p<.0001). Median initial blood pressure was 183/95 mm Hg and did not differ between survivors and nonsurvivors. In a multivariable analysis, neurologic patients who died experienced lower minimal blood pressure values (median 103/45 vs. 118/55 mm Hg, p<.0001) and were less likely to experience recurrent hypertension requiring intravenous treatment (29% vs. 51%, p=.0001) than those who survived. Mortality was also associated with an increased frequency of neurologic deterioration (32% vs. 10%, p<.0001). Neurologic emergencies account for approximately 30% of hospitalized patients with severe acute hypertension, and the majority of those who die. Mortality in hypertensive neurologic patients is associated with lower minimum blood pressure values, less rebound hypertension, and a higher frequency of neurologic deterioration. Excessive blood pressure reduction may contribute to poor outcome after severe brain injury.

Influence of slope steepness, foot position and turn phase on plantar pressure distribution during giant slalom alpine ski racing.

PubMed

Falda-Buscaiot, Thomas; Hintzy, Frédérique; Rougier, Patrice; Lacouture, Patrick; Coulmy, Nicolas

2017-01-01

The purpose of this study was to investigate the evolution of ground reaction force during alpine skiing turns. Specifically, this study investigated how turn phases and slope steepness affected the whole foot normal GRF pattern while performing giant slalom turns in a race-like setting. Moreover, the outside foot was divided into different plantar regions to see whether those parameters affected the plantar pressure distribution. Eleven skiers performed one giant slalom course at race intensity. Runs were recorded synchronously using a video camera in the frontal plane and pressure insoles under both feet's plantar surface. Turns were divided according to kinematic criteria into four consecutive phases: initiation, steering1, steering2 and completion; both steering phases being separated by the gate passage. Component of the averaged Ground Reaction Force normal to the ski's surface([Formula: see text], /BW), and Pressure Time Integral relative to the entire foot surface (relPTI, %) parameters were calculated for each turn phases based on plantar pressure data. Results indicated that [Formula: see text] under the total foot surface differed significantly depending on the slope (higher in steep sections vs. flat sections), and the turn phase (higher during steering2 vs. three other phases), although such modifications were observable only on the outside foot. Moreover, [Formula: see text] under the outside foot was significantly greater than under the inside foot.RelPTI under different foot regions of the outside foot revealed a global shift from forefoot loading during initiation phase, toward heel loading during steering2 phase, but this was dependent on the slope studied. These results suggest a differentiated role played by each foot in alpine skiing turns: the outside foot has an active role in the turning process, while the inside foot may only play a role in stability.

A phoenics model for the triaxial loading of an initially cylindrical mass of rate-type material with provisions for bulging and yield

NASA Technical Reports Server (NTRS)

French, K. W., Jr.

1986-01-01

This work traces the response of a granular material via the Ten Coefficient Truesdell rate-type constituitive model into the simplest meaningful loading: the triaxial test configuration. A functional relation has been posed for computing the rather peculiar relation between average applied stress and average porosity. Using that relation an attack has been mounted on the dilemma that exists between dynamic and constitutive use of the pressure variable; that is relating dynamic pressure, thermodynamic pressure, stress deviator and higher stress invariants. The resolution was as a linear superposition with a one-way feedback, in that while the dynamic component could not effect the constituitive component, the converse was not true since density appears in the momentum transport relation.

Surface electromyography and plantar pressure during walking in young adults with chronic ankle instability.

PubMed

Koldenhoven, Rachel M; Feger, Mark A; Fraser, John J; Saliba, Susan; Hertel, Jay

2016-04-01

Lateral ankle sprains are common and can manifest into chronic ankle instability (CAI) resulting in altered gait mechanics that may lead to subsequent ankle sprains. Our purpose was to simultaneously analyse muscle activation patterns and plantar pressure distribution during walking in young adults with and without CAI. Seventeen CAI and 17 healthy subjects walked on a treadmill at 4.8 km/h. Plantar pressure measures (pressure-time integral, peak pressure, time to peak pressure, contact area, contact time) of the entire foot and nine specific foot regions and medial-lateral location of centre of pressure (COP) were measured. Surface electromyography (EMG) root mean square (RMS) amplitudes throughout the entire stride cycle and area under RMS curve for 100 ms pre-initial contact (IC) and 200 ms post-IC for anterior tibialis, peroneus longus, medial gastrocnemius, and gluteus medius were collected. The CAI group demonstrated a more lateral COP throughout the stance phase (P < 0.001 and Cohen's d > 0.9 for all 10 comparisons) and significantly increased peak pressure (P = 0.025) and pressure-time integral (P = 0.049) under the lateral forefoot. The CAI group had lower anterior tibialis RMS areas (P < 0.001) and significantly higher peroneus longus, medial gastrocnemius, and gluteus medius RMS areas during 100 ms pre-IC (P < 0.003). The CAI group had higher gluteus medius sEMG amplitudes during the final 50 % of stance and first 25% of swing (P < 0.05). The CAI group had large lateral deviations of their COP location throughout the entire stance phase and increased gluteus medius muscle activation amplitude during late stance through early swing phase. III.

Effects of hydrostatic pressure on microbial alteration of sinking fecal pellets

NASA Astrophysics Data System (ADS)

Tamburini, Christian; Goutx, Madeleine; Guigue, Catherine; Garel, Marc; Lefèvre, Dominique; Charrière, Bruno; Sempéré, Richard; Pepa, Stéphane; Peterson, Michael L.; Wakeham, Stuart; Lee, Cindy

2009-08-01

We used a new experimental device called PASS (PArticle Sinking Simulator) during MedFlux to simulate changes in in situ hydrostatic pressure that particles experience sinking from mesopelagic to bathypelagic depths. Particles, largely fecal pellets, were collected at 200 m using a settling velocity NetTrap (SV NetTrap) in Ligurian Sea in April 2006 and incubated in high-pressure bottles (HPBs) of the PASS system under both atmospheric and continuously increasing pressure conditions, simulating the pressure change experienced at a sinking rate of 200 m d -1. Chemical changes over time were evaluated by measuring particulate organic carbon (POC), carbohydrates, transparent exopolymer particles (TEP), amino acids, lipids, and chloropigments, as well as dissolved organic carbon (DOC) and dissolved carbohydrates. Microbial changes were evaluated microscopically, using diamidinophenylindole (DAPI) stain for total cell counts and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) for phylogenetic distinctions. Concentrations (normalized to POC) of particulate chloropigments, carbohydrates and TEP decreased under both sets of incubation conditions, although less under the increasing pressure regime than under atmospheric conditions. By contrast, dissolved carbohydrates (normalized to DOC) were higher after incubation and significantly higher under atmospheric conditions, suggesting they were produced at the expense of the particulate fraction. POC-normalized particulate wax/steryl esters increased only under pressure, suggesting biochemical responses of prokaryotes to the increasing pressure regime. The prokaryotic community initially consisted of 43% Bacteria, 12% Crenarchaea and 11% Euryarchaea. After incubation, Bacteria dominated (˜90%) the prokaryote community in all cases, with γ- Proteobacteria comprising the greatest fraction, followed by the Cytophaga-Flavobacter cluster and α -Proteobacteria group. Using the PASS system, we obtained chemical and microbial evidence that degradation by prokaryotes associated with fecal pellets sinking through mesopelagic waters is limited by the increasing pressure they experience.

Effects of high shock pressures and pore morphology on hot spot mechanisms in HMX

NASA Astrophysics Data System (ADS)

Springer, H. K.; Tarver, C. M.; Bastea, S.

2017-01-01

The shock initiation and detonation behavior of heterogeneous solid explosives is governed by its microstructure and reactive properties. New additive manufacturing techniques offer unprecedented control of explosive microstructures previously impossible, enabling us to develop novel explosives with tailored shock sensitivity and detonation properties. Since microstructure-performance relationships are not well established for explosives, there is little material design guidance for these manufacturing techniques. In this study, we explore the effects of high shock pressures (15-38 GPa) with long shock durations and different pore morphologies on hot spot mechanisms in HMX. HMX is chosen as the model material because we have experimental data on many of the chemical-thermal-mechanical properties required for pore collapse simulations. Our simulations are performed using the multi-physics arbitrary Lagrangian Eulerian finite element hydrocode, ALE3D, with Cheetah-based models for the unreacted and the product equation-of-states. We use a temperature-dependent specific heat with the unreacted equation-of-state and a temperature-dependent viscosity model to ensure accurate shock temperatures for subsequent chemistry. The Lindemann Law model is used for shock melting in HMX. In contrast to previous pore collapse studies at lower shock pressures (≤10 GPa) in HMX and shorter post-collapse burning times, our calculations show that shock melting occurs above 15 GPa due to higher bulk heating and a prominent elongated ("jet-like") hot spot region forms at later times. The combination of the elongated, post-collapse hot spot region and the higher bulk heating with increasing pressure dramatically increases the growth rate of reaction. Our calculations show that the reaction rate, dF/dt, increases with increasing shock pressure. We decompose the reaction rate into ignition ((dF/dt)ig) and growth ((dF/dt)gr) phases to better analyze our results. We define the ignition phase to primarily include pore collapse and growth phase to primarily include post-collapse grain burning. We are able to track late-time, post-collapse burning due to the unique loading conditions employed in these calculations. We find that (dF/dt)gr > (dF/dt)ig for all pressures considered. (dF/dt)gr changes more significantly from 25 to 38 GPa (from 0.05/µs to >10-100/µs) than from 15 to 25 GPa (from 0.005/µs to 0.05/µs). There is a three order-of-magnitude difference in the reaction from 15 to 38 GPa just after pore collapse. This is qualitatively consistent with fitting the (macroscopic) Ignition and Growth model to high pressure shock initiation data, where much larger reaction fractions are needed to capture the early stages of reaction. Calculated burn rates demonstrate better agreement with data at intermediate times in the growth phase for 15 to 25 GPa and late times for 30 GPa then at any time in the growth phase for 38 GPa. Our calculations are much higher than burn rate data at the earliest times in the growth phase for all pressures, which may reflect the higher localized pressures and temperatures just after pore collapse in the ignition phase. Our calculations with spherical, conical, and elliptical pores show that the influence of morphology on reaction rate is pressure dependent and the most influential pore shapes at lower pressures aren't the same at higher pressures in the regime studied. Altogether these studies provide the basis for developing microstructure-aware models that can be used to design new explosives with optimal performance-safety characteristics. Such models can be used to guide additive manufacturing of explosives and fully exploit their disruptive nature.

Basic aerodynamic research facility for comparative studies of flow diagnostic techniques

NASA Technical Reports Server (NTRS)

Jones, Gregory S.; Gartrell, Luther R.; Stainback, P. Calvin

1987-01-01

Current flow diagnostic research efforts are focusing on higher order flow field data bases, such as those generated by laser velocimetry (LV), hot-wire anemometry, and multi-hole pressure probes. Recent low-speed comparisons of results obtained with LV and hot wires have revealed strengths and weaknesses of each instrument. A seeding study will be initiated to determine particulate tracking ability.

Prevalence and incidence studies of pressure ulcers in two long-term care facilities in Canada.

PubMed

Davis, C M; Caseby, N G

2001-11-01

A study was initiated to determine the prevalence and incidence of pressure ulcers in two long-term care facilities in Canada, one with 95 residents and the other with 92 residents. The prevalence study was conducted at both facilities on a single day. The incidence study was completed after 41 and 42 days, respectively, at each facility. Data were collected on demographics, medical information, and possible contributing factors. Each resident was assessed for the presence of a pressure ulcer. Each ulcer was staged and anatomical location was noted. The prevalence of pressure ulcers in the two long-term care facilities was 36.8% and 53.2%, respectively. The incidence of pressure ulcers in the two long-term care facilities was 11.7% and 11.6%, respectively. In conclusion, the pressure ulcer prevalence is higher than published figures for the long-term care setting. However, a pressure ulcer incidence of less than 12% in each facility suggests an equal and acceptable level of nursing care in both facilities. The disparity of pressure ulcer prevalence between the two facilities may be explained by a difference of case mix.

Relevance of impacter shape to nonvisible damage and residual tensile strength of a thick graphite/epoxy laminate

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.

1991-01-01

A study was made to determine the relevance of impacter shape to nonvisible damage and tensile residual strength of a 36 mm thick graphite/epoxy motor case. The shapes of the impacters were as follows: 12.7 mm and 25.4 mm diameter hemispheres, a sharp corner, and a 6.3 mm diameter bolt-like rod. The investigation revealed that damage initiated when the contact pressure exceeded a critical level. However, the damage was not visible on the surface until an even higher pressure was exceeded. The impact energy to initiate damage or cause visible damage on the surface increased approximately with impacter diameter to the third power. The reduction in strength for nonvisible damage increased with increasing diameter, 9 and 30 percent for the 12.7 mm and 25.4 mm diameter hemispheres, respectively. The corner impacter made visible damage on the surface for even the smallest impact energy. The rod impacter acted like a punch and sliced through the composite. Even so, the critical level of pressure to initiate damage was the same for the rod and hemispherical impacters. Factors of safety for nonvisible damage increased with increasing kinetic energy of impact. The effects of impacter shape on impact force, damage size, damage visibility, and residual tensile strength were predicted quite well assuming Hertzian contact and using maximum stress criteria and a surface crack analysis.

Selective fibronectin adsorption against albumin and enhanced stem cell attachment on helium atmospheric pressure glow discharge treated titanium

NASA Astrophysics Data System (ADS)

Han, Inho; Vagaska, Barbora; Joo Park, Bong; Lee, Mi Hee; Jin Lee, Seung; Park, Jong-Chul

2011-06-01

Successful tissue integration of implanted medical devices depends on appropriate initial cellular response. In this study, the effect of helium atmospheric pressure glow discharge (He-APGD) treatment of titanium on selective protein adsorption and the initial attachment processes and focal adhesion formation of osteoprogenitor cells and stem cells were examined. Titanium disks were treated in a self-designed He-APGD system. Initial attachment of MC3T3-E1 mouse pre-osteoblasts and human mesenchymal stem cells (MSCs) was evaluated by MTT assay and plasma membrane staining followed by morphometric analysis. Fibronectin adsorption was investigated by Enzyme-Linked ImmunoSorbant Assay. MSCs cell attachment to treated and non-treated titanium disks coated with different proteins was verified also in serum-free culture. Organization of actin cytoskeleton and focal adhesions was evaluated microscopically. He-APGD treatment effectively modified the titanium surfaces by creating a super-hydrophilic surface, which promoted selectively higher adsorption of fibronectin, a protein of critical importance for cell/biomaterial interaction. In two different types of cells, the He-APGD treatment enhanced the number of attaching cells as well as their attachment area. Moreover, cells had higher organization of actin cytoskeleton and focal adhesions. Faster acceptance of the material by the progenitor cells in the early phases of tissue integration after the implantation may significantly reduce the overall healing time; therefore, titanium treatment with He-APGD seems to be an effective method of surface modification of titanium for improving its tissue inductive properties.

Preventing Heel Pressure Ulcers: Sustained Quality Improvement Initiative in a Canadian Acute Care Facility.

PubMed

Hanna-Bull, Debbie

2016-01-01

The setting for this quality improvement initiative designed to reduce the prevalence of facility-acquired heel pressure ulcers was a regional, acute-care, 490-bed facility in Ontario, Canada, responsible for dialysis, vascular, and orthopedic surgery. An interdisciplinary skin and wound care team designed an evidence-based quality improvement initiative based on a systematic literature review and standardization of heel offloading methods. The prevalence of heel pressure ulcers was measured at baseline (immediately prior to implementation of initiative) and at 1 and 4 years following implementation. The prevalence of facility-acquired heel pressure ulcers was 5.8% when measured before project implementation. It was 4.2% at 1 year following implementation and 1.6% when measured at the end of the 4-year initiative. Outcomes demonstrate that the initiative resulted in a continuous and sustained reduction in facility-acquired heel pressure ulcer incidence over a 4-year period.

Pharmacologic Treatment of Hypertension in Adults Aged 60 Years or Older to Higher Versus Lower Blood Pressure Targets: A Clinical Practice Guideline From the American College of Physicians and the American Academy of Family Physicians.

PubMed

Qaseem, Amir; Wilt, Timothy J; Rich, Robert; Humphrey, Linda L; Frost, Jennifer; Forciea, Mary Ann

2017-03-21

The American College of Physicians (ACP) and the American Academy of Family Physicians (AAFP) jointly developed this guideline to present the evidence and provide clinical recommendations based on the benefits and harms of higher versus lower blood pressure targets for the treatment of hypertension in adults aged 60 years or older. This guideline is based on a systematic review of published randomized, controlled trials for primary outcomes and observational studies for harms only (identified through EMBASE, the Cochrane Database of Systematic Reviews, MEDLINE, and ClinicalTrials.gov), from database inception through January 2015. The MEDLINE search was updated through September 2016. Evaluated outcomes included all-cause mortality, morbidity and mortality related to stroke, major cardiac events (fatal and nonfatal myocardial infarction and sudden cardiac death), and harms. This guideline grades the evidence and recommendations using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) method. The target audience for this guideline includes all clinicians, and the target patient population includes all adults aged 60 years or older with hypertension. ACP and AAFP recommend that clinicians initiate treatment in adults aged 60 years or older with systolic blood pressure persistently at or above 150 mm Hg to achieve a target systolic blood pressure of less than 150 mm Hg to reduce the risk for mortality, stroke, and cardiac events. (Grade: strong recommendation, high-quality evidence). ACP and AAFP recommend that clinicians select the treatment goals for adults aged 60 years or older based on a periodic discussion of the benefits and harms of specific blood pressure targets with the patient. ACP and AAFP recommend that clinicians consider initiating or intensifying pharmacologic treatment in adults aged 60 years or older with a history of stroke or transient ischemic attack to achieve a target systolic blood pressure of less than 140 mm Hg to reduce the risk for recurrent stroke. (Grade: weak recommendation, moderate-quality evidence). ACP and AAFP recommend that clinicians select the treatment goals for adults aged 60 years or older based on a periodic discussion of the benefits and harms of specific blood pressure targets with the patient. ACP and AAFP recommend that clinicians consider initiating or intensifying pharmacologic treatment in some adults aged 60 years or older at high cardiovascular risk, based on individualized assessment, to achieve a target systolic blood pressure of less than 140 mm Hg to reduce the risk for stroke or cardiac events. (Grade: weak recommendation, low-quality evidence). ACP and AAFP recommend that clinicians select the treatment goals for adults aged 60 years or older based on a periodic discussion of the benefits and harms of specific blood pressure targets with the patient.

THE EFFECT OF HORMONE THERAPY ON MEAN BLOOD PRESSURE AND VISIT-TO-VISIT BLOOD PRESSURE VARIABILITY IN POSTMENOPAUSAL WOMEN: RESULTS FROM THE WOMEN’S HEALTH INITIATIVE RANDOMIZED CONTROLLED TRIALS

PubMed Central

Shimbo, Daichi; Wang, Lu; Lamonte, Michael J.; Allison, Matthew; Wellenius, Gregory A.; Bavry, Anthony A.; Martin, Lisa W.; Aragaki, Aaron; Newman, Jonathan D.; Swica, Yael; Rossouw, Jacques E.; Manson, JoAnn E.; Wassertheil-Smoller, Sylvia

2014-01-01

Objectives Mean and visit-to-visit variability (VVV) of blood pressure are associated with an increased cardiovascular disease risk. We examined the effect of hormone therapy on mean and VVV of blood pressure in postmenopausal women from the Women’s Health Initiative (WHI) randomized controlled trials. Methods Blood pressure was measured at baseline and annually in the two WHI hormone therapy trials in which 10,739 and 16,608 postmenopausal women were randomized to conjugated equine estrogens (CEE, 0.625 mg/day) or placebo, and CEE plus medroxyprogesterone acetate (MPA, 2.5 mg/day) or placebo, respectively. Results At the first annual visit (Year 1), mean systolic blood pressure was 1.04 mmHg (95% CI 0.58, 1.50) and 1.35 mmHg (95% CI 0.99, 1.72) higher in the CEE and CEE+MPA arms respectively compared to corresponding placebos. These effects remained stable after Year 1. CEE also increased VVV of systolic blood pressure (ratio of VVV in CEE vs. placebo, 1.03, P<0.001), whereas CEE+MPA did not (ratio of VVV in CEE+MPA vs. placebo, 1.01, P=0.20). After accounting for study drug adherence, the effects of CEE and CEE+MPA on mean systolic blood pressure increased at Year 1, and the differences in the CEE and CEE+MPA arms vs. placebos also continued to increase after Year 1. Further, both CEE and CEE+MPA significantly increased VVV of systolic blood pressure (ratio of VVV in CEE vs. placebo, 1.04, P<0.001; ratio of VVV in CEE+MPA vs. placebo, 1.05, P<0.001). Conclusions Among postmenopausal women, CEE and CEE+MPA at conventional doses increased mean and VVV of systolic blood pressure. PMID:24991872

Initial condition effect on pressure waves in an axisymmetric jet

NASA Technical Reports Server (NTRS)

Miles, Jeffrey H.; Raman, Ganesh

1988-01-01

A pair of microphones (separated axially by 5.08 cm and laterally by 1.3 cm) are placed on either side of the jet centerline to investigate coherent pressure fluctuations in an axisymmetric jet at Strouhal numbers less than unity. Auto-spectra, transfer-function, and coherence measurements are made for a tripped and untripped boundary layer initial condition. It was found that coherent acoustic pressure waves originating in the upstream plenum chamber propagate a greater distance downstream for the tripped initial condition than for the untripped initial condition. In addition, for the untripped initial condition the development of the coherent hydrodynamic pressure waves shifts downstream.

Under Pressure: Intraluminal Filling Pressures of Postpartum Hemorrhage Tamponade Balloons

PubMed Central

Antony, Kathleen M.; Racusin, Diana A.; Belfort, Michael A.; Dildy, Gary A.

2017-01-01

Objective Uterine tamponade by fluid-filled balloons is now an accepted method of controlling postpartum hemorrhage. Available tamponade balloons vary in design and material, which affects the filling attributes and volume at which they rupture. We aimed to characterize the filling capacity and pressure-volume relationship of various tamponade balloons. Study Design Balloons were filled with water ex vivo. Intraluminal pressure was measured incrementally (every 10 mL for the Foley balloons and every 50 mL for all other balloons). Balloons were filled until they ruptured or until 5,000 mL was reached. Results The Foley balloons had higher intraluminal pressures than the larger-volume balloons. The intraluminal pressure of the Sengstaken-Blakemore tube (gastric balloon) was initially high, but it decreased until shortly before rupture occurred. The Bakri intraluminal pressure steadily increased until rupture occurred at 2,850 mL. The condom catheter, BT-Cath, and ebb all had low intraluminal pressures. Both the BT-Cath and the ebb remained unruptured at 5,000 mL. Conclusion In the setting of acute hemorrhage, expeditious management is critical. Balloons that have a low intraluminal pressure-volume ratio may fill more rapidly, more easily, and to greater volumes. We found that the BT-Cath, the ebb, and the condom catheter all had low intraluminal pressures throughout filling. PMID:28497006

Space Shuttle Upgrade Liquid Oxygen Tank Thermal Stratification

NASA Technical Reports Server (NTRS)

Tunc, Gokturk; Wagner, Howard; Bayazitoglu, Yildiz

2001-01-01

In 1997, NASA initiated a study of a liquid oxygen and ethanol orbital maneuvering and reaction control system for space shuttle upgrades as well as other reusable launch vehicle applications. The pressure-fed system uses sub-cooled liquid oxygen at 2413.2 KPa (350 psia) stored passively using insulation. Thermal stratification builds up while the space shuttle is docked at the international space station. The venting from the space shuttle's liquid oxygen tank is not desired during this 96-hr time period. Once the shuttle undocks from the space station there could be a pressure collapse in the liquid oxygen tank caused by fluid mixing due to the thruster fU"ings . The thermal stratification and resulting pressure rise in the tank were examined by a computational fluid dynamic model. Since the heat transfer from the pressurant gas to the liquid will result in a decrease in tank pressure the final pressure after the 96 hours will be significantly less when the tank is pressurized with ambient temperature helium. Therefore, using helium at ambient temperature to pressurize the tank is preferred to pressurizing the tank with helium at the liquid oxygen temperature. The higher helium temperature will also result in less mass of helium to pressurize the tank.

High speed 2-dimensional temperature measurements of nanothermite composites: Probing thermal vs. Gas generation effects

NASA Astrophysics Data System (ADS)

Jacob, Rohit J.; Kline, Dylan J.; Zachariah, Michael R.

2018-03-01

This work investigates the reaction dynamics of metastable intermolecular composites through high speed spectrometry, pressure measurements, and high-speed color camera pyrometry. Eight mixtures including Al/CuO and Al/Fe2O3/xWO3 (x being the oxidizer mol. %) were reacted in a constant volume pressure cell as a means of tuning gas release and adiabatic temperature. A direct correlation between gas release, peak pressure, and pressurization rate was observed, but it did not correlate with temperature. When WO3 was varied as part of the stoichiometric oxidizer content, it was found that Al/Fe2O3/70% WO3 achieved the highest pressures and shortest burn time despite a fairly constant temperature between mixtures, suggesting an interplay between the endothermic Fe2O3 decomposition and the higher adiabatic flame temperature sustained by the Al/WO3 reaction in the composite. It is proposed that the lower ignition temperature of Al/WO3 leads to the initiation of the composite and its higher flame temperature enhances the gasification of Fe2O3, thus improving advection and propagation as part of a feedback loop that drives the reaction. Direct evidence of such gas release promoting reactivity was obtained through high speed pyrometry videos of the reaction. These results set the stage for nanoenergetic materials that can be tuned for specific applications through carefully chosen oxidizer mixtures.

Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

USGS Publications Warehouse

Safak, Ilgar; Warner, John C.; List, Jeffrey

2016-01-01

Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

Increased Jet Noise Due to a "Nominally Laminar" State of Nozzle Exit Boundary Layer

NASA Technical Reports Server (NTRS)

Zaman, K. B. M. Q.

2017-01-01

A set of 2-in. diameter nozzles is used to investigate the effect of varying exit boundary layer state on the radiated noise from high-subsonic jets. It is confirmed that nozzles involving turbulent boundary layers are the quietest while nozzles involving a "nominally laminar" boundary layer are loud especially on the high-frequency side of the sound pressure level spectrum. The latter boundary layer state involves a "Blasius-like" mean velocity profile but higher turbulence intensities compared to those in the turbulent state. The higher turbulence in the initial region of the jet shear layer leads to increased high-frequency noise. The results strongly suggest that an anomaly noted with subsonic jet noise databases in the literature is due to a similar effect of differences in the initial boundary layer state.

Increased Jet Noise Due to a "Nominally Laminar" State of Nozzle Exit Boundary Layer

NASA Technical Reports Server (NTRS)

Zaman, K. B. M. Q.

2017-01-01

A set of 2-inch diameter nozzles is used to investigate the effect of varying exit boundary layer state on the radiated noise from high-subsonic jets. It is confirmed that nozzles involving turbulent boundary layers are the quietest while nozzles involving a nominally-laminar boundary layer are loud especially on the high-frequency side of the sound pressure level spectrum. The latter boundary layer state involves a Blasius-like mean velocity profile but higher turbulence intensities compared to those in the turbulent state. The higher turbulence in the initial region of the jet shear layer leads to increased high-frequency noise. The results strongly suggest that an anomaly noted with subsonic jet noise databases in the literature is due to a similar effect of differences in the initial boundary layer state.

Effects of dopamine and dobutamine on isoflurane-induced hypotension in Hispaniolan Amazon parrots (Amazona ventralis).

PubMed

Schnellbacher, Rodney W; da Cunha, Anderson F; Beaufrère, Hugues; Queiroz, Patricia; Nevarez, Javier G; Tully, Thomas N

2012-07-01

To assess the effects of dopamine and dobutamine on the blood pressure of isoflurane-anesthetized Hispaniolan Amazon parrots (Amazona ventralis). 8 Hispaniolan Amazon parrots. A randomized crossover study was conducted. Each bird was anesthetized (anesthesia maintained by administration of 2.5% isoflurane in oxygen) and received 3 doses of each drug during a treatment period of 20 min/dose. Treatments were constant rate infusions (CRIs) of dobutamine (5, 10, and 15 μg/kg/min) and dopamine (5, 7, and 10 μg/kg/min). Direct systolic, diastolic, and mean arterial pressure measurements, heart rate, esophageal temperature, and end-tidal partial pressure of CO(2) were recorded throughout the treatment periods. Mean ± SD of the systolic, mean, and diastolic arterial blood pressures at time 0 (initiation of a CRI) were 132.9 ± 22.1 mm Hg, 116.9 ± 20.5 mm Hg, and 101.9 ± 22.0 mm Hg, respectively. Dopamine resulted in significantly higher values than did dobutamine for the measured variables, except for end-tidal partial pressure of CO(2). Post hoc multiple comparisons revealed that the changes in arterial blood pressure were significantly different 4 to 7 minutes after initiation of a CRI. Overall, dopamine at rates of 7 and 10 μg/kg/min and dobutamine at a rate of 15 μg/kg/min caused the greatest increases in arterial blood pressure. Dobutamine CRI at 5, 10, and 15 μg/kg/min and dopamine CRI at 5, 7, and 10 μg/kg/min may be useful in correcting severe hypotension in Hispaniolan Amazon parrots caused by anesthesia maintained with 2.5% isoflurane.

Hyperoxia is Associated with Increased Mortality in Patients Treated with Mild Therapeutic Hypothermia after Sudden Cardiac Arrest

PubMed Central

Janz, David R.; Hollenbeck, Ryan D.; Pollock, Jeremy S.; McPherson, John A.; Rice, Todd W.

2012-01-01

Objective To determine if higher levels of partial pressure of arterial oxygen are associated with in-hospital mortality and poor neurologic status at hospital discharge in patients treated with mild therapeutic hypothermia after sudden cardiac arrest. Design Retrospective analysis of a prospective cohort study Patients A total of 170 consecutive patients treated with therapeutic hypothermia in the cardiovascular care unit of an academic tertiary care hospital. Interventions None. Measurements and Main Results Of 170 patients, 77 (45.2%) survived to hospital discharge. Survivors had a significantly lower maximum partial pressure of arterial oxygen(198 mmHg, IQR 152.5–282) measured in the first 24 hours following cardiac arrest compared to nonsurvivors (254 mmHg, IQR 172–363, p = .022). A multivariable analysis including age, time to return of spontaneous circulation, the presence of shock, bystander CPR, and initial rhythm revealed that higher levels of the partial pressure of arterial oxygen were significantly associated with increased in-hospital mortality (odds ratio 1.439, 95% confidence interval 1.028–2.015, p = 0.034) and poor neurologic status at hospital discharge (odds ratio 1.485, 95% confidence interval 1.032–2.136, p = 0.033). Conclusions Higher levels of the maximum measured partial pressure of arterial oxygen are associated with increased in-hospital mortality and poor neurologic status on hospital discharge in patients treated with mild therapeutic hypothermia after sudden cardiac arrest. PMID:22971589

Redeposition of a straight-sided buckle under pressure.

PubMed

Colin, Jérôme; Coupeau, Christophe; Durinck, Julien; Cimetière, Alain; Grilhé, Jean

2014-03-01

The unilateral buckling of a stressed thin film on a substrate has been investigated theoretically in the framework of the Föppl-von Kármán theory of thin plates when an increasing overpressure is considered onto the upper free surface of the film. It is found that, depending on the initial stress in the film and overpressure, two scenarios of evolution may occur. The snap-through of the one-dimensional buckle leading to the full redeposition should take place for low values of the initial stress. When the initial stress exceeds a critical value, a partial redeposition of the buckle should proceed as the overpressure increases. A snap-through while the redeposition mechanism has taken place should also occur for higher values of the overpressure.

Fabrication and characterization of powder metallurgy tantalum components prepared by high compaction pressure technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Youngmoo; Agency for Defense Development, Yuseong, P.O. Box 35, Yuseong-gu, Daejeon 34186, Republic of Korea.; Lee, Dongju

2016-04-15

The present study has investigated the consolidation behaviors of tantalum powders during compaction and sintering, and the characteristics of sintered components. For die compaction, the densification behaviors of the powders are simulated by finite element analyses based on the yield function proposed by Shima and Oyane. Accordingly, the green density distribution for coarser particles is predicted to be more uniform because they exhibits higher initial relative tap density owing to lower interparticle friction. It is also found that cold isostatic pressing is capable of producing higher dense compacts compared to the die pressing. However, unlike the compaction behavior, the sinteredmore » density of smaller particles is found to be higher than those of coarser ones owing to their higher specific surface area. The maximum sintered density was found to be 0.96 of theoretical density where smaller particles were pressed isostatically at 400 MPa followed by sintering at 2000 °C. Moreover, the effects of processing conditions on grain size and texture were also investigated. The average grain size of the sintered specimen is 30.29 μm and its texture is less than 2 times random intensity. Consequently, it is concluded that the higher pressure compaction technique is beneficial to produce high dense and texture-free tantalum components compared to hot pressing and spark plasma sintering. - Highlights: • Higher Ta density is obtained from higher pressure and sintering temperature. • High compaction method enables P/M Ta to achieve the density of 16.00 g·cm{sup −3}. • A P/M Ta component with fine microstructure and random orientation is developed.« less

Effect of fluid penetration on tensile failure during fracturing of an open-hole wellbore

NASA Astrophysics Data System (ADS)

Zeng, Fanhui; Cheng, Xiaozhao; Guo, Jianchun; Chen, Zhangxin; Tao, Liang; Liu, Xiaohua; Jiang, Qifeng; Xiang, Jianhua

2018-06-01

It is widely accepted that a fracture can be induced at a wellbore surface when the fluid pressure overcomes the rock tensile strength. However, few models of this phenomenon account for the fluid penetration effect. A rock is a typical permeable, porous medium, and the transmission of pressure from a wellbore to the surrounding rock temporally and spatially perturbs the effective stresses. In addition, these induced stresses influence the fracture initiation pressure. To gain a better understanding of the penetration effect on the initiation pressure of a permeable formation, a comprehensive formula is presented to study the effects of the in situ stresses, rock mechanical properties, injection rate, rock permeability, fluid viscosity, fluid compressibility and wellbore size on the magnitude of the initiation pressure during fracturing of an open-hole wellbore. In this context, the penetration effect is treated as a consequence of the interaction among these parameters by using Darcy’s law of radial flow. A fully coupled analytical procedure is developed to show how the fracturing fluid infiltrates the rock around the wellbore and considerably reduces the magnitude of the initiation pressure. Moreover, the calculation results are validated by hydraulic fracturing experiments in hydrostone. An exhaustive sensitivity study is performed, indicating that the local fluid pressure induced from a seepage effect strongly influences the fracture evolution. For permeable reservoirs, a low injection rate and a low viscosity of the injected fluid have a significant impact on the fracture initiation pressure. In this case, the Hubbert and Haimson equations to predict the fracture initiation pressure are not valid. The open-hole fracture initiation pressure increases with the fracturing fluid viscosity and fluid compressibility, while it decreases as the rock permeability, injection rate and wellbore size increase.

Muscular subaortic stenosis: the initial left ventricular inflow tract pressure as evidence of outflow tract obstruction.

PubMed

Wigle, E D; Auger, P; Marquis, Y

1966-10-15

Two types of intraventricular pressure differences within the left ventricle of man are described. The first is encountered in cases of muscular (or fibrous) subaortic stenosis, in which the outflow tract pressure distal to the stenosis (and proximal to the aortic valve) is low, whereas all pressures recorded in the left ventricle proximal to the stenosis, including that just inside the mitral valve (the initial inflow tract pressure) are high.The second type of intraventricular pressure difference may be recorded in patients without muscular subaortic stenosis when a heart catheter is advanced to the left ventricular wall in such a manner that it becomes imbedded or entrapped by cardiac muscle in systole. Such an entrapped catheter records a high intraventricular pressure that is believed to reflect intramyocardial tissue pressure, which normally exceeds intracavitary pressure. In such cases the initial inflow tract pressure is not high and is precisely equal to the outflow tract systolic pressure, i.e. both are recording intracavity pressure. This type of intramyocardial to intracavitary pressure difference may also be encountered in the left ventricle of dogs.The recent suggestion that intraventricular pressure differences in the left ventricle of cases of muscular subaortic stenosis are due to catheter entrapment by cardiac muscle is refuted by using the initial inflow tract pressure as the means of differentiation between the two types of intraventricular pressure differences outlined.

Parabolized Stability Equations analysis of nonlinear interactions with forced eigenmodes to control subsonic jet instabilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Itasse, Maxime, E-mail: Maxime.Itasse@onera.fr; Brazier, Jean-Philippe, E-mail: Jean-Philippe.Brazier@onera.fr; Léon, Olivier, E-mail: Olivier.Leon@onera.fr

2015-08-15

Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m{sub 1}, n{sub 1}), (m{sub 2}, n{sub 2}), such that the difference in azimuth and in frequencymore » matches the desired “target” mode (m{sub 1} − m{sub 2}, n{sub 1} − n{sub 2}). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes.« less

Numerical simulation on the powder propellant pickup characteristics of feeding system at high pressure

NASA Astrophysics Data System (ADS)

Sun, Haijun; Hu, Chunbo; Zhu, Xiaofei

2017-10-01

A numerical study of powder propellant pickup progress at high pressure was presented in this paper by using two-fluid model with kinetic theory of granular flow in the computational fluid dynamics software package ANSYS/Fluent. Simulations were conducted to evaluate the effects of initial pressure, initial powder packing rate and mean particle diameter on the flow characteristics in terms of velocity vector distribution, granular temperature, pressure drop, particle velocity and volume. The numerical results of pressure drop were also compared with experiments to verify the TFM model. The simulated results show that the pressure drop value increases as the initial pressure increases, and the granular temperature under the conditions of different initial pressures and packing rates is almost the same in the area of throttling orifice plate. While there is an appropriate value for particle size and packing rate to form a ;core-annulus; structure in powder box, and the time-averaged velocity vector distribution of solid phase is inordinate.

High-pressure infrared sepctra of alpha-quartz, coesite, stishovite and silica glass

NASA Technical Reports Server (NTRS)

Williams, Q.; Hemley, R. J.; Kruger, M. B.; Jeanloz, R.

1993-01-01

High-pressure infrared absorption spectra of alpha-quatz, coesite, stishovite, and SiO2 glass are consistent with the primary compression mechanism of the initially tetrahedrally bonded phases being the bending of the Si-O-Si angle at pressures less than 10-20 GPa. At higher pressures, up to 40 GPa, we observe a decline in the intensity of the infrared SiO4 asymmetric-stretching vibrations of all three phases, with an increase in the relative amplitude between 700 and 900/cm. This change in intensities is attributed to an increase in the average coordination number of silicon through extreme distortion of tetrahedra. At pressures above approximately 20 GPa, the low-pressure crystalline polymorphs gradually become amorphous, and the infrared spectra provide evidence for an increase in silicon coordination in these high-density amorphous phases. The pressure-amorphized samples prepared from quartz and coesite differ structurally both from each other and from silica glass that has been compressed, and the high pressure spectra indicate that these materials are considerably more disordered than stishovite under comparable pressure conditions. Average mode Grueneisen parameters calculated for quartz, stishovite and fused silica from both infrared and Raman spectra are compatible with the corresponding thermodynamic value of the Grueneisen parameter, however, that of coesite is significantly discrepant.

Rapid compression transforms interfacial monolayers of pulmonary surfactant.

PubMed

Crane, J M; Hall, S B

2001-04-01

Films of pulmonary surfactant in the lung are metastable at surface pressures well above the equilibrium spreading pressure of 45 mN/m but commonly collapse at that pressure when compressed in vitro. The studies reported here determined the effect of compression rate on the ability of monolayers containing extracted calf surfactant at 37 degrees C to maintain very high surface pressures on the continuous interface of a captive bubble. Increasing the rate from 2 A(2)/phospholipid/min (i.e., 3% of (initial area at 40 mN/m)/min) to 23%/s produced only transient increases to 48 mN/m. Above a threshold rate of 32%/s, however, surface pressures reached > 68 mN/m. After the rapid compression, static films maintained surface pressures within +/- 1 mN/m both at these maximum values and at lower pressures following expansion at < 5%/min to > or = 45 mN/m. Experiments with dimyristoyl phosphatidylcholine at 37 degrees C produced similar results. These findings indicate that compression at rates comparable to values in the lungs can transform at least some phospholipid monolayers from a form that collapses readily at the equilibrium spreading pressure to one that is metastable for prolonged periods at higher pressures. Our results also suggest that transformation of surfactant films can occur without refinement of their composition.

Equation of State and Electrical Conductivity of Helium at High Pressures and Temperatures

NASA Astrophysics Data System (ADS)

McWilliams, R. S.; Eggert, J. H.; Loubeyre, P.; Brygoo, S.; Collins, G.; Jeanloz, R.

2004-12-01

Helium, the second-most abundant element in the universe and giant planets, is expected to metallize at much higher pressures and temperatures than the most abundant element, hydrogen. The difference in chemical-bonding character, between insulator and metal, is expected to make hydrogen-helium mixtures immiscible throughout large fractions of planetary interiors, and therefore subject to gravitational separation contributing significantly to the internal dynamics of giant planets. Using laser-driven shock waves on samples pre-compressed in high-pressure cells, we have obtained the first measurements of optical reflectivity from the shock front in helium to pressures of 146 GPa. The reflectivity exceeds 5% above \\ensuremath{\\sim} 100 GPa, indicating high electrical conductivity. By varying the initial pressure (hence density) of the sample, we can access a much wider range of final pressure-temperature conditions than is possible in conventional Hugoniot experiments. Our work increases by nine-fold the pressure range of single-shock measurements, in comparison with gas-gun experiments, and yields results in agreement with the Saumon, Chabrier and Van Horn (1994) equation of state for helium. This changes the internal structures inferred for Jupiter-size planets, relative to models based on earlier equations of state (e. g., SESAME).

The Sooner, the Worse? Association between Earlier Age of Sexual Initiation and Worse Adolescent Health and Well-being Outcomes

PubMed Central

Osorio, Alfonso; Lopez-del Burgo, Cristina; Carlos, Silvia; de Irala, Jokin

2017-01-01

This cross-sectional study assesses the association between age of sexual initiation during adolescence and a selection of well-being outcomes regarding that first relationship. High-school adolescents from El Salvador (2,686) and from Peru (3,399) replied to a paper-pencil questionnaire. Those who were sexually initiated replied to several questions regarding their age at sexual initiation, condom use, satisfaction and reasons/circumstances for that sexual relationship. Approximately 19% of participants were sexually initiated (n = 1,179). After retaining participants with valid responses and with sexual initiation ages between 13 and 17, the final sample for this paper consisted of 996 sexually initiated participants (526 Salvadorians and 470 Peruvians). Multiple logistic regression analyses showed that those who initiated sex at earlier ages had worse outcomes compared to those who initiated at older ages. Specifically, they had lower odds of having used a condom, of having good memories of that experience and of having had that first relationship because they were in love. Conversely, they had higher odds of having had that first sexual relationship as a result of peer pressure (“Most of my friends already had sex”), because of partner pressure (“I was afraid to lose him/her,” “My partner told me he/she would leave me” or “I did not know how to say no to a person who insisted”), or as a consequence of different forms of impaired autonomy (“I was under the influence of alcohol or drugs” or “As a consequence of seeing sexual images”). Results show that sex at earlier ages is associated with worse adolescent health and well-being outcomes. PMID:28798715

Influence of temporal pressure constraint on the biomechanical organization of gait initiation made with or without an obstacle to clear.

PubMed

Yiou, Eric; Fourcade, Paul; Artico, Romain; Caderby, Teddy

2016-06-01

Many daily motor tasks have to be performed under a temporal pressure constraint. This study aimed to explore the influence of such constraint on motor performance and postural stability during gait initiation. Young healthy participants initiated gait at maximal velocity under two conditions of temporal pressure: in the low-pressure condition, gait was self-initiated (self-initiated condition, SI); in the high-pressure condition, it was initiated as soon as possible after an acoustic signal (reaction-time condition, RT). Gait was initiated with and without an environmental constraint in the form of an obstacle to be cleared placed in front of participants. Results showed that the duration of postural adjustments preceding swing heel-off ("anticipatory postural adjustments", APAs) was shorter, while their amplitude was larger in RT compared to SI. These larger APAs allowed the participants to reach equivalent postural stability and motor performance in both RT and SI. In addition, the duration of the execution phase of gait initiation increased greatly in the condition with an obstacle to be cleared (OBST) compared to the condition without an obstacle (NO OBST), thereby increasing lateral instability and thus involving larger mediolateral APA. Similar effects of temporal pressure were obtained in NO OBST and OBST. This study shows the adaptability of the postural system to temporal pressure in healthy young adults initiating gait. The outcome of this study may provide a basis for better understanding the aetiology of balance impairments with the risk of falling in frail populations while performing daily complex tasks involving a whole-body progression.

Bubble performance of a novel dissolved air flotation(DAF) unit.

PubMed

Chen, Fu-tai; Peng, Feng-xian; Wu, Xiao-qing; Luan, Zhao-kun

2004-01-01

ES-DAF, a novel DAF with low cost, high reliability and easy controllability, was studied. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied in detail by using a newly developed CCD imagination through a microscope. Compared with M-DAF under the same saturation pressure, ES-DAF can produce smaller bubble size and higher bubble volume concentration, especially in lower pressure. In addition, the bubble size decreases with the increase of reflux ratio or decrease of superficial air-water ratio. These results suggested that smaller bubbles will be formed when the initial number of nucleation sites increases by enhancing the turbulence intensity in the saturation system.

[Atrio-ventricular pressure difference associated with mitral valve motion].

PubMed

Wang, L M; Mori, H; Minezaki, K; Shinozaki, Y; Okino, H

1990-05-01

Pressure difference (PD) across the mitral valve was analyzed by a computer-aided catheter system in dogs. Positive PD (PPD) was consistently traced in the initial phase of rapid filling. While heart rate (HR) was below 100 beat/min, a negative PD (NPD) followed the above PPD. In the period between the NPD and the 2nd PPD due to atrial contraction, PD was kept at zero, while LA and LV pressures were gradually elevated by pulmonary venous return. As HR exceeded 100, 2 positive peaks of PD merged into M-shaped or mono-peaked PD. Through higher inflow resistance produced by artificial mitral stenosis, PPD peak decayed without NPD. In mitral regurgitation with an acute volume overload, all of the PD amplitudes were exaggerated. Thus the quick reversal of PD suggested the effect in blood filling process across the mitral valve.

Effect of captopril treatment on total and central vascular capacitance in dogs with chronic heart failure.

PubMed

Ogilvie, R I; Zborowska-Sluis, D

1994-09-01

Chronic rapid right ventricular pacing (RRVP) at 250 beats/min produces low cardiac output (CO) heart failure, marked reduction in total vascular capacitance, and a shift in volume centrally. The effect of converting enzyme inhibition with captopril on cardiac preload was investigated in this model of heart failure. Eight splenectomized dogs were treated with captopril (6.4 mg/kg daily) for 3 days before and 35 +/- 3 days (mean +/- SEM) after continuous RRVP was initiated and the outcome was compared with that of 5 untreated dogs subjected to RRVP for 32 +/- 3 days. Similar reductions in systemic arterial pressure (Psa) and CO and increases in right atrial pressure (Pra) and total peripheral resistance (TPR) were noted in both groups, however, pulmonary capillary wedge pressure (Ppcw) was higher in the untreated group (18.4 +/- 1.6 vs. 12.1 +/- 2.0 mm Hg). Total vascular compliance and capacitance was estimated from mean circulatory filling pressures (Pmcf) at different blood volumes (TBV) during transitory cardiac arrests with acetylcholine (ACh). Pmcf after chronic RRVP was higher in untreated animals (12.6 +/- 1.9 vs. 8.4 +/- 0.7 mm Hg) and compliance was lower (1.9 +/- 0.2 vs. 2.6 +/- 0.2 ml/mm Hg/kg). Total vascular capacitance at a Pmcf of 6 mm Hg was lower in untreated animals (50 +/- 6 vs. 68 +/- 3 ml/kg). Central vascular capacitance was also lower in untreated animals because Ppcw was higher and central blood volume (CBV) as a proportion of TBV was higher (21 +/- 3 vs. 15 +/- 2%). Four of 5 untreated and 1 of 8 treated dogs had severe ascites.(ABSTRACT TRUNCATED AT 250 WORDS)

Intermittent operation of ultra-low pressure ultrafiltration for decentralized drinking water treatment.

PubMed

Peter-Varbanets, Maryna; Gujer, Willi; Pronk, Wouter

2012-06-15

River water was treated by ultrafiltration at a relatively low transmembrane pressure (40 mbar). As observed before, flux stabilization occurred after several days of operation although no back-flushing or cross flow was applied. Interruptions in flux were applied by temporary offset of the transmembrane pressure. After restoration of the transmembrane pressure, the initial flux was higher than the stable flux level, and the flux recovery depended on the standstill time. Furthermore, if a short cross flow was applied after standstill, the flux was restored to an even higher level. In all cases, the flux decreased again during operation to reach finally the same stable level as before standstill. In order to evaluate the influence of intermittent operation as practiced for water treatment on a household level, daily interruptions of flux were applied. An optimum of total daily water production rate was obtained at 21 h of operation and 3 h of standstill per day. A model was developed which can describe the impact of intermittent operation on the flux depending on the duration of the standstill and operating periods. This enables the prediction of production capacity of the system operated intermittently. The flux increase during standstill could be explained by a relaxation and expansion of the biofouling layer, while the higher flux after forward-flushing was caused by this layer being partially sloughed off. Household water treatment with the process presented here will generally be operated on a discontinuous basis. The results show that such operation schemes do not compromise the permeability of the system, but actually lead to higher fluxes after standstill. Copyright © 2012 Elsevier Ltd. All rights reserved.

Economic and clinical benefit of collagenase ointment compared to a hydrogel dressing for pressure ulcer debridement in a long-term care setting.

PubMed

Waycaster, Curtis; Milne, Catherine

2013-06-01

The purpose of this study is to determine the cost-effectiveness of collagenase ointment relative to autolysis with a hydrogel dressing when debriding necrotic pressure ulcers in a long-term care setting. A Markov decision process model with 2 states (necrotic nonviable wound bed transitioning to a granulated viable wound bed) was developed using data derived from a prospective, randomized, 6-week, single-center trial of 27 institutionalized subjects with pressure ulcers that were ≥ 85% necrotic nonviable tissue. Direct medical costs from the payer perspective included study treatments, wound treatment supplies, and nursing time. Clinical benefit was measured as "granulation days" and was derived from the time-dependent debridement rates of the alternative products. The average cost per patient for 42 days of pressure ulcer care was $1,817 in 2012 for the collagenase group and $1,611 for the hydrogel group. Days spent with a granulated wound were 3.6 times higher for collagenase (23.4 vs 6.5) than with the hydrogel. The estimated cost per granulation day was > 3.2 times higher for hydrogel ($249) vs collagenase ($78). In this economic analysis based on a randomized, controlled clinical trial, collagenase ointment resulted in a faster time to complete debridement and was more cost-effective than hydrogel autolysis for pressure ulcers in a long-term care setting. Even though collagenase ointment has a higher acquisition cost than hydrogel, the clinical benefit offsets the initial cost difference, resulting in lower cost per granulation day to the nursing home over the course of the 42-day analysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, D.L.; Simonen, F.A.; Strosnider, J. Jr.

The VISA (Vessel Integrity Simulation Analysis) code was developed as part of the NRC staff evaluation of pressurized thermal shock. VISA uses Monte Carlo simulation to evaluate the failure probability of a pressurized water reactor (PWR) pressure vessel subjected to a pressure and thermal transient specified by the user. Linear elastic fracture mechanics are used to model crack initiation and propagation. parameters for initial crack size, copper content, initial RT/sub NDT/, fluence, crack-initiation fracture toughness, and arrest fracture toughness are treated as random variables. This report documents the version of VISA used in the NRC staff report (Policy Issue frommore » J.W. Dircks to NRC Commissioners, Enclosure A: NRC Staff Evaluation of Pressurized Thermal Shock, November 1982, SECY-82-465) and includes a user's guide for the code.« less

Associations between Potentially Modifiable Risk Factors and Alzheimer Disease: A Mendelian Randomization Study.

PubMed

Østergaard, Søren D; Mukherjee, Shubhabrata; Sharp, Stephen J; Proitsi, Petroula; Lotta, Luca A; Day, Felix; Perry, John R B; Boehme, Kevin L; Walter, Stefan; Kauwe, John S; Gibbons, Laura E; Larson, Eric B; Powell, John F; Langenberg, Claudia; Crane, Paul K; Wareham, Nicholas J; Scott, Robert A

2015-06-01

Potentially modifiable risk factors including obesity, diabetes, hypertension, and smoking are associated with Alzheimer disease (AD) and represent promising targets for intervention. However, the causality of these associations is unclear. We sought to assess the causal nature of these associations using Mendelian randomization (MR). We used SNPs associated with each risk factor as instrumental variables in MR analyses. We considered type 2 diabetes (T2D, NSNPs = 49), fasting glucose (NSNPs = 36), insulin resistance (NSNPs = 10), body mass index (BMI, NSNPs = 32), total cholesterol (NSNPs = 73), HDL-cholesterol (NSNPs = 71), LDL-cholesterol (NSNPs = 57), triglycerides (NSNPs = 39), systolic blood pressure (SBP, NSNPs = 24), smoking initiation (NSNPs = 1), smoking quantity (NSNPs = 3), university completion (NSNPs = 2), and years of education (NSNPs = 1). We calculated MR estimates of associations between each exposure and AD risk using an inverse-variance weighted approach, with summary statistics of SNP-AD associations from the International Genomics of Alzheimer's Project, comprising a total of 17,008 individuals with AD and 37,154 cognitively normal elderly controls. We found that genetically predicted higher SBP was associated with lower AD risk (odds ratio [OR] per standard deviation [15.4 mm Hg] of SBP [95% CI]: 0.75 [0.62-0.91]; p = 3.4 × 10(-3)). Genetically predicted higher SBP was also associated with a higher probability of taking antihypertensive medication (p = 6.7 × 10(-8)). Genetically predicted smoking quantity was associated with lower AD risk (OR per ten cigarettes per day [95% CI]: 0.67 [0.51-0.89]; p = 6.5 × 10(-3)), although we were unable to stratify by smoking history; genetically predicted smoking initiation was not associated with AD risk (OR = 0.70 [0.37, 1.33]; p = 0.28). We saw no evidence of causal associations between glycemic traits, T2D, BMI, or educational attainment and risk of AD (all p > 0.1). Potential limitations of this study include the small proportion of intermediate trait variance explained by genetic variants and other implicit limitations of MR analyses. Inherited lifetime exposure to higher SBP is associated with lower AD risk. These findings suggest that higher blood pressure--or some environmental exposure associated with higher blood pressure, such as use of antihypertensive medications--may reduce AD risk.

Joint reconstruction of the initial pressure and speed of sound distributions from combined photoacoustic and ultrasound tomography measurements

NASA Astrophysics Data System (ADS)

Matthews, Thomas P.; Anastasio, Mark A.

2017-12-01

The initial pressure and speed of sound (SOS) distributions cannot both be stably recovered from photoacoustic computed tomography (PACT) measurements alone. Adjunct ultrasound computed tomography (USCT) measurements can be employed to estimate the SOS distribution. Under the conventional image reconstruction approach for combined PACT/USCT systems, the SOS is estimated from the USCT measurements alone and the initial pressure is estimated from the PACT measurements by use of the previously estimated SOS. This approach ignores the acoustic information in the PACT measurements and may require many USCT measurements to accurately reconstruct the SOS. In this work, a joint reconstruction method where the SOS and initial pressure distributions are simultaneously estimated from combined PACT/USCT measurements is proposed. This approach allows accurate estimation of both the initial pressure distribution and the SOS distribution while requiring few USCT measurements.

Effect of a physical activity programme in the aquatic environment on haemodynamic constants in pregnant women.

PubMed

Vázquez-Lara, Juana María; Ruiz-Frutos, Carlos; Rodríguez-Díaz, Luciano; Ramírez-Rodrigo, Jesús; Villaverde-Gutiérrez, Carmen; Torres-Luque, Gema

2017-09-20

To evaluate the effect of a physical activity programme in the aquatic environment with immersion up to the neck, of six weeks duration, on haemodynamic constants in pregnant women. A six-week physical activity programme in the aquatic environment was carried out with a total of 46 pregnant women, who were distributed into an experimental group (n = 18), which participated in the programme, and a control group (n = 28), which followed routine care. In both groups different haemodynamic measurements were evaluated before and after the program. At the beginning of the programme the mean systolic blood pressure was similar between groups, but diastolic blood pressure was slightly higher in the experimental group. When the measurements at the last session were compared, arterial pressures (systolic, diastolic and mean) were significantly higher in the control group (p <.050). Similarly, the initial plasma volume values did not differ between groups, but after the intervention, the control group women showed a higher mean (p <.010). The fraction of sodium excretion (FENa) increased significantly in the experimental group, after the programme, with a mean three times higher (p <.050). Aldosterone plasma levels did not show significant differences between the groups in the different measurements. A programme of swimming and immersion exercises in pregnant women contributes to hydrosaline balance, preventing an excessive increase in usual plasma volume during pregnancy and in the activity of the renin-aldosterone axis. Copyright © 2017 Elsevier España, S.L.U. All rights reserved.

Glow plasma trigger for electron cyclotron resonance ion sources.

PubMed

Vodopianov, A V; Golubev, S V; Izotov, I V; Nikolaev, A G; Oks, E M; Savkin, K P; Yushkov, G Yu

2010-02-01

Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 micros and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10(12) cm(-3), required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T(e) approximately = 20 eV.

Early regimes of water capillary flow in slit silica nanochannels.

PubMed

Oyarzua, Elton; Walther, Jens H; Mejía, Andrés; Zambrano, Harvey A

2015-06-14

Molecular dynamics simulations are conducted to investigate the initial stages of spontaneous imbibition of water in slit silica nanochannels surrounded by air. An analysis is performed for the effects of nanoscopic confinement, initial conditions of liquid uptake and air pressurization on the dynamics of capillary filling. The results indicate that the nanoscale imbibition process is divided into three main flow regimes: an initial regime where the capillary force is balanced only by the inertial drag and characterized by a constant velocity and a plug flow profile. In this regime, the meniscus formation process plays a central role in the imbibition rate. Thereafter, a transitional regime takes place, in which, the force balance has significant contributions from both inertia and viscous friction. Subsequently, a regime wherein viscous forces dominate the capillary force balance is attained. Flow velocity profiles identify the passage from an inviscid flow to a developing Poiseuille flow. Gas density profiles ahead of the capillary front indicate a transient accumulation of air on the advancing meniscus. Furthermore, slower capillary filling rates computed for higher air pressures reveal a significant retarding effect of the gas displaced by the advancing meniscus.

Shock initiation of an ɛ-CL-20-estane formulation

NASA Astrophysics Data System (ADS)

Tarver, C. M.; Simpson, R. L.; Urtiew, P. A.

1996-05-01

The shock sensitivity of a pressed solid explosive formulation, LX-19, containing 95.2% by weight epsilon phase 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW) and 4.8% Estane binder, was determined using the wedge test and embedded manganin pressure gauge techniques. This formulation was shown to be slightly more sensitive than LX-14, which contains 95.5% HMX and 4.5% Estane binder. The measured pressure histories for LX-19 were very similar to those obtained using several HMX-inert binder formulations. An Ignition and Growth reactive flow model for LX-19 was developed which differed from those for HMX-inert binder formulations only by a 25% higher hot spot growth rate.

Simplified Two-Time Step Method for Calculating Combustion and Emission Rates of Jet-A and Methane Fuel With and Without Water Injection

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2005-01-01

A simplified kinetic scheme for Jet-A, and methane fuels with water injection was developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) or even simple FORTRAN codes. The two time step method is either an initial time averaged value (step one) or an instantaneous value (step two). The switch is based on the water concentration in moles/cc of 1x10(exp -20). The results presented here results in a correlation that gives the chemical kinetic time as two separate functions. This two time step method is used as opposed to a one step time averaged method previously developed to determine the chemical kinetic time with increased accuracy. The first time averaged step is used at the initial times for smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, initial water to fuel mass ratio, temperature, and pressure. The second instantaneous step, to be used with higher water concentrations, gives the chemical kinetic time as a function of instantaneous fuel and water mole concentration, pressure and temperature (T4). The simple correlations would then be compared to the turbulent mixing times to determine the limiting rates of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide and NOx are obtained for Jet-A fuel and methane with and without water injection to water mass loadings of 2/1 water to fuel. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentrations of carbon monoxide and nitrogen oxide as functions of overall equivalence ratio, water to fuel mass ratio, pressure and temperature (T3). The temperature of the gas entering the turbine (T4) was also correlated as a function of the initial combustor temperature (T3), equivalence ratio, water to fuel mass ratio, and pressure.

[Association between higher blood pressure level in children and adult blood pressure: 17 years follow-up results].

PubMed

Mu, Jian-Jun; Liu, Zhi-Quan; Yang, Jun; Ren, Jie; Liu, Wei-Min; Xu, Xiang-Lin; Xiong, Su-E

2008-03-01

Essential hypertension may begin at childhood. The aim of this study is to identify the risk factors of hypertension and detect the evolvement tracking of blood pressure in childhood. In this study, we followed up blood pressure changes in 4623 school children (6 - 15 years-old) from 1987 to 2005 in Hanzhong rural area. A total of 152 children were grouped to higher blood pressure group [systolic blood pressure (P(SBP)) >or= 75(th) (P(75))] and 140 children grouped to normal blood pressure group [P(SBP) < 50(th) (P(50))] and their blood pressure were re-measure 18-years later. The total follow-up rate was 70.2%. Follow-up blood pressure was significantly higher in higher blood pressure group at baseline than that in normal blood pressure group at baseline (P < 0.05). The hypertension rate at follow up was significantly higher in higher blood pressure group at baseline than that in normal blood pressure group at baseline (28.0% vs. 4.1%, P < 0.01). The risk for hypertension was 6.88 greater in higher blood pressure group at baseline than that in normal blood pressure group at baseline. Higher blood pressure at childhood is a risk of developing hypertension at adulthood.

How does low temperature coupled with different pressures affect initiation mechanisms and subsequent decompositions in nitramine explosive HMX?

PubMed

Wu, Qiong; Xiong, Guolin; Zhu, Weihua; Xiao, Heming

2015-09-21

We have performed ab initio molecular dynamics simulations to study coupling effects of temperature (534-873 K) and pressure (1-20 GPa) on the initiation mechanisms and subsequent chemical decompositions of nitramine explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). A new initiation decomposition mechanism of HMX was found to be the unimolecular C-H bond breaking, and this mechanism was independent of the coupling effects of different temperatures and pressures. The formed hydrogen radicals could promote subsequent decompositions of HMX. Subsequent decompositions were very sensitive to the pressure at low temperatures (534 and 608 K), while the temperature became the foremost factor that affected the decomposition at a high temperature (873 K) instead of the pressure. Our study may provide a new insight into understanding the coupling effects of the temperature and pressure on the initiation decomposition mechanisms of nitramine explosives.

Tension responses to rapid pressure release in glycerinated rabbit muscle fibers.

PubMed Central

Fortune, N S; Geeves, M A; Ranatunga, K W

1991-01-01

We have previously shown that the isometric tension of a fully calcium-activated skinned rabbit psoas muscle fiber is reversibly depressed by increased hydrostatic pressure. We report here the characterization of tension transients induced by a rapid (less than 1-ms) release of increased pressure at 12 degrees C. The tension transient consists of three clear phases, an initial further decrease of tension in phase with pressure change followed by two phases of tension increase back to the level recorded at ambient pressure. The mean reciprocal relaxation time for phase 2 (1/tau 2) was approximately 17 s-1 and that for phase 3 (1/tau 3) was 3 s-1. The presence of 20 mM inorganic phosphate markedly increased 1/tau 2 to approximately 52 s-1 and decreased 1/tau 3 to approximately 1.7 s-1. These observations are interpreted in terms of a pressure-sensitive transition between two attached crossbridge states of low (or zero) and higher force. This is compatible with the pressure-sensitive isomerization of actomyosin previously observed in solution. The results presented allow us to propose a coupling between a specific pressure-sensitive isomerization of purified actomyosin, the phosphate release step of the ATPase pathway, and the force-generating event of the cross-bridge cycle. PMID:1871140

Three-dimensional finite analysis of acetabular contact pressure and contact area during normal walking.

PubMed

Wang, Guangye; Huang, Wenjun; Song, Qi; Liang, Jinfeng

2017-11-01

This study aims to analyze the contact areas and pressure distributions between the femoral head and mortar during normal walking using a three-dimensional finite element model (3D-FEM). Computed tomography (CT) scanning technology and a computer image processing system were used to establish the 3D-FEM. The acetabular mortar model was used to simulate the pressures during 32 consecutive normal walking phases and the contact areas at different phases were calculated. The distribution of the pressure peak values during the 32 consecutive normal walking phases was bimodal, which reached the peak (4.2 Mpa) at the initial phase where the contact area was significantly higher than that at the stepping phase. The sites that always kept contact were concentrated on the acetabular top and leaned inwards, while the anterior and posterior acetabular horns had no pressure concentration. The pressure distributions of acetabular cartilage at different phases were significantly different, the zone of increased pressure at the support phase distributed at the acetabular top area, while that at the stepping phase distributed in the inside of acetabular cartilage. The zones of increased contact pressure and the distributions of acetabular contact areas had important significance towards clinical researches, and could indicate the inductive factors of acetabular osteoarthritis. Copyright © 2016. Published by Elsevier Taiwan.

Study on the mode-transition of nanosecond-pulsed dielectric barrier discharge between uniform and filamentary by controlling pressures and pulse repetition frequencies

NASA Astrophysics Data System (ADS)

Yu, S.; Pei, X.; Hasnain, Q.; Nie, L.; Lu, X.

2016-02-01

In this paper, we investigate the temporally resolved evolution of the nanosecond pulsed dielectric barrier discharge (DBD) in a moderate 6 mm discharge gap under various pressures and pulse repetition frequencies (PRFs) by intensified charge-coupled device (ICCD) images, using dry air and its components oxygen and nitrogen. It is found that the pressures are very different when the mode transits between uniform and filamentary in air, oxygen, and nitrogen. The PRFs can also obviously affect the mode-transition. The transition mechanism in the pulsed DBD is not Townsend-to-Streamer, which is dominant in the traditional alternating-voltage DBD. The pulsed DBD in a uniform mode develops in the form of plane ionization wave due to overlap of primary avalanches, while the increase in pressure disturbs the overlap and discharge develops in streamer, corresponding to the filamentary mode. Increasing the initial electron density by pre-ionization may contribute to discharge uniformity at higher pressures. We also found that the dependence of homogeneity upon PRF is a non-monotonic one.

The influence of low and high pressure levels during negative-pressure wound therapy on wound contraction and fluid evacuation.

PubMed

Borgquist, Ola; Ingemansson, Richard; Malmsjö, Malin

2011-02-01

Negative-pressure wound therapy promotes healing by drainage of excessive fluid and debris and by mechanical deformation of the wound. The most commonly used negative pressure, -125 mmHg, may cause pain and ischemia, and the pressure often needs to be reduced. The aim of the present study was to examine wound contraction and fluid removal at different levels of negative pressure. Peripheral wounds were created in 70-kg pigs. The immediate effects of negative-pressure wound therapy (-10 to -175 mmHg) on wound contraction and fluid removal were studied in eight pigs. The long-term effects on wound contraction were studied in eight additional pigs during 72 hours of negative-pressure wound therapy at -75 mmHg. Wound contraction and fluid removal increased gradually with increasing levels of negative pressure until reaching a steady state. Maximum wound contraction was observed at -75 mmHg. When negative-pressure wound therapy was discontinued, after 72 hours of therapy, the wound surface area was smaller than before therapy. Maximum wound fluid removal was observed at -125 mmHg. Negative-pressure wound therapy facilitates drainage of wound fluid and exudates and results in mechanical deformation of the wound edge tissue, which is known to stimulate granulation tissue formation. Maximum wound contraction is achieved already at -75 mmHg, and this may be a suitable pressure for most wounds. In wounds with large volumes of exudate, higher pressure levels may be needed for the initial treatment period.

Effects of Gas Pressure on the Failure Characteristics of Coal

NASA Astrophysics Data System (ADS)

Xie, Guangxiang; Yin, Zhiqiang; Wang, Lei; Hu, Zuxiang; Zhu, Chuanqi

2017-07-01

Several experiments were conducted using self-developed equipment for visual gas-solid coupling mechanics. The raw coal specimens were stored in a container filled with gas (99% CH4) under different initial gas pressure conditions (0.0, 0.5, 1.0, and 1.5 MPa) for 24 h prior to testing. Then, the specimens were tested in a rock-testing machine, and the mechanical properties, surface deformation and failure modes were recorded using strain gauges, an acoustic emission (AE) system and a camera. An analysis of the fractals of fragments and dissipated energy was performed to understand the changes observed in the stress-strain and crack propagation behaviour of the gas-containing coal specimens. The results demonstrate that increased gas pressure leads to a reduction in the uniaxial compression strength (UCS) of gas-containing coal and the critical dilatancy stress. The AE, surface deformation and fractal analysis results show that the failure mode changes during the gas state. Interestingly, a higher initial gas pressure will cause the damaged cracks and failure of the gas-containing coal samples to become severe. The dissipated energy characteristic in the failure process of a gas-containing coal sample is analysed using a combination of fractal theory and energy principles. Using the theory of fracture mechanics, based on theoretical analyses and calculations, the stress intensity factor of crack tips increases as the gas pressure increases, which is the main cause of the reduction in the UCS and critical dilatancy stress and explains the influence of gas in coal failure. More serious failure is created in gas-containing coal under a high gas pressure and low exterior load.

Pressure Ulcers in Elderly Hip Fracture Patients Across the Continuum of Care

PubMed Central

Baumgarten, Mona; Margolis, David J.; Orwig, Denise L.; Shardell, Michelle D.; Hawkes, William G.; Langenberg, Patricia; Palmer, Mary H.; Jones, Patricia S.; McArdle, Patrick F.; Sterling, Robert; Kinosian, Bruce P.; Rich, Shayna E.; Sowinski, Janice; Magaziner, Jay

2012-01-01

Objectives The aim of this study was to identify care settings associated with increased pressure ulcer risk among elderly hip fracture patients in the post-fracture period. Design Prospective cohort study. Setting Nine hospitals that participate in the Baltimore Hip Studies network and 105 postacute facilities to which patients from these hospitals were discharged. Participants Hip fracture patients age ≥65 years who underwent surgery for hip fracture. Measurements A full-body skin examination was conducted at baseline (as soon as possible after hospital admission) and repeated on alternating days for 21 days. Patients were deemed to have an acquired pressure ulcer (APU) if they developed ≥1 new pressure ulcers stage 2 or higher following hospital admission. Results Among 658 study participants, the APU cumulative incidence at 32 days after initial hospital admission was 36.1% (standard error 2.5%). Compared to home, the adjusted APU incidence rate was highest during the initial acute hospital stay (relative rate [RR] 2.2, 95% confidence interval [CI] 1.3–3.7) and during re-admission to the acute hospital (RR 2.2, 95% CI 1.1–4.2). The relative rates in rehabilitation and nursing home settings were 1.4 (95% CI 0.8–2.3) and 1.3 (95% CI 0.8–2.1), respectively. Conclusion Approximately one-third of hip fracture patients developed an APU during the study period. The rate was highest in the acute setting, a finding that is significant in light of Medicare’s policy of not reimbursing hospitals for the treatment of hospital-acquired pressure ulcers. Hip fracture patients constitute an important group to target for pressure ulcer prevention in hospitals. PMID:19484841

A randomized comparison of the i-gel with the self-pressurized air-Q intubating laryngeal airway in children.

PubMed

Kim, Min-Soo; Lee, Jae Hoon; Han, Sang Won; Im, Young Jae; Kang, Hyo Jong; Lee, Jeong-Rim

2015-04-01

Supraglottic airway devices with noninflatable cuff have advantages in omitting the cuff pressure monitoring and reducing potential pharyngolaryngeal complications. Typical devices without cuff inflation available in children are the i-gel and the self-pressurized air-Q intubating laryngeal airway (air-Q SP). To date, there is no comparative study between these devices in pediatric patients. The purpose of this randomized study was to compare the i-gel(™) and the self-pressurized air-Q(™) intubating laryngeal airway (air-Q SP) in children undergoing general anesthesia. Eighty children, 1-108 months of age, 7-30 kg of weight, and scheduled for elective surgery in which supraglottic airway devices would be suitable for airway management, were randomly assigned to either the i-gel or the air-Q SP. Oropharyngeal leak pressure and fiberoptic view were assessed three times as follows: after insertion and fixation of the device, 10 min after initial assessment, and after completion of surgery. We also assessed insertion parameters and complications. Insertion of the i-gel was regarded as significantly easier compared to the air-Q SP (P = 0.04). Compared to the air-Q SP group, the i-gel group had significantly higher oropharyngeal leak pressures at all measurement points and significantly lower frequencies of gastric insufflation at 10 min after initial assessment and completion of surgery. The air-Q SP group had better fiberoptic views than the i-gel group at all measurement points. Our results showed that the i-gel had easier insertion and better sealing function, and the air-Q SP provided improved fiberoptic views in children requiring general anesthesia. © 2015 John Wiley & Sons Ltd.

Methane hydrate synthesis from ice: Influence of pressurization and ethanol on optimizing formation rates and hydrate yield

USGS Publications Warehouse

Chen, Po-Chun.; Huang, Wuu-Liang; Stern, Laura A.

2010-01-01

Polycrystalline methane gas hydrate (MGH) was synthesized using an ice-seeding method to investigate the influence of pressurization and ethanol on the hydrate formation rate and gas yield of the resulting samples. When the reactor is pressurized with CH4 gas without external heating, methane hydrate can be formed from ice grains with yields up to 25% under otherwise static conditions. The rapid temperature rise caused by pressurization partially melts the granular ice, which reacts with methane to form hydrate rinds around the ice grains. The heat generated by the exothermic reaction of methane hydrate formation buffers the sample temperature near the melting point of ice for enough time to allow for continuous hydrate growth at high rates. Surprisingly, faster rates and higher yields of methane hydrate were found in runs with lower initial temperatures, slower rates of pressurization, higher porosity of the granular ice samples, or mixtures with sediments. The addition of ethanol also dramatically enhanced the formation of polycrystalline MGH. This study demonstrates that polycrystalline MGH with varied physical properties suitable for different laboratory tests can be manufactured by controlling synthesis procedures or parameters. Subsequent dissociation experiments using a gas collection apparatus and flowmeter confirmed high methane saturation (CH 4·2O, with n = 5.82 ± 0.03) in the MGH. Dissociation rates of the various samples synthesized at diverse conditions may be fitted to different rate laws, including zero and first order.

Simplified Two-Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydorgen/Oxygen

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2005-01-01

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two-time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (> 1 x 10(exp -20) moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/air fuel and for the H2/O2. A similar correlation is also developed using data from NASA s Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). High values of the regression coefficient R2 are obtained.

Summary of Simplified Two Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/Oxygen

NASA Technical Reports Server (NTRS)

Marek, C. John; Molnar, Melissa

2005-01-01

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (greater than l x 10(exp -20)) moles per cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T(sub 4)). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/Air fuel and for H2/O2. A similar correlation is also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T(sub 4)) as a function of overall fuel/air ratio, pressure and initial temperature (T(sub 3)). High values of the regression coefficient R squared are obtained.

Vascular Physiology according to Clinical Scenario in Patients with Acute Heart Failure: Evaluation using the Cardio-Ankle Vascular Index.

PubMed

Goto, Toshihiko; Wakami, Kazuaki; Mori, Kento; Kikuchi, Shohei; Fukuta, Hidekatsu; Ohte, Nobuyuki

2016-09-01

Increased aortic stiffness may be an important cause of acute heart failure (AHF). Clinical scenario (CS), which classifies the pathophysiology of AHF based on the initial systolic blood pressure (sBP), was proposed to provide the most appropriate therapy for AHF patients. In CS, elevated aortic stiffness, vascular failure, has been considered as a feature of patients categorized as CS1 (sBP > 140 mmHg at initial presentation). However, whether elevated aortic stiffness, vascular failure, is present in such patients has not been fully elucidated. Therefore, we assessed aortic stiffness in AHF patients using the cardio-ankle vascular index (CAVI), which is considered to be independent of instantaneous blood pressure. Sixty-four consecutive AHF patients (mean age, 70.6 ± 12.8 years; 39 men) were classified with CS, based on their initial sBP: CS1: sBP > 140 mmHg (n = 29); CS2: sBP 100-140 mmHg (n = 22); and CS3: sBP < 100 mmHg (n = 13). There were significant group differences in CAVI (CS1 vs. CS2 vs. CS3: 9.7 ± 1.4 vs. 8.4 ± 1.7 vs. 8.3 ± 1.7, p = 0.006, analysis of variance). CAVI was significantly higher in CS1 than in CS2 (p = 0.02) and CS3 (p = 0.04). CAVI did not significantly correlate with sBP at the time of measurement of CAVI (r = 0.24 and p = 0.06). Aortic stiffness assessed using blood pressure-independent methodology apparently increased in CS1 AHF patients. We conclude that vascular failure is a feature of CS1 AHF initiation.

Radiation damage characterization in reactor pressure vessel steels with nonlinear ultrasound

NASA Astrophysics Data System (ADS)

Matlack, K. H.; Kim, J.-Y.; Wall, J. J.; Qu, J.; Jacobs, L. J.

2014-02-01

Nuclear generation currently accounts for roughly 20% of the US baseload power generation. Yet, many US nuclear plants are entering their first period of life extension and older plants are currently undergoing assessment of technical basis to operate beyond 60 years. This means that critical components, such as the reactor pressure vessel (RPV), will be exposed to higher levels of radiation than they were originally intended to withstand. Radiation damage in reactor pressure vessel steels causes microstructural changes such as vacancy clusters, precipitates, dislocations, and interstitial loops that leave the material in an embrittled state. The development of a nondestructive evaluation technique to characterize the effect of radiation exposure on the properties of the RPV would allow estimation of the remaining integrity of the RPV with time. Recent research has shown that nonlinear ultrasound is sensitive to radiation damage. The physical effect monitored by nonlinear ultrasonic techniques is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave, arising from the interaction of the ultrasonic wave with microstructural features such as dislocations, precipitates, and their combinations. Current findings relating the measured acoustic nonlinearity parameter to increasing levels of neutron fluence for different representative RPV materials are presented.

High-precision measurements of the compressibility of chalcogenide glasses at a hydrostatic pressure up to 9 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brazhkin, V. V., E-mail: brazhkin@hppi.troitsk.ru; Bychkov, E.; Tsiok, O. B.

2016-08-15

The volumes of glassy germanium chalcogenides GeSe{sub 2}, GeS{sub 2}, Ge{sub 17}Se{sub 83}, and Ge{sub 8}Se{sub 92} are precisely measured at a hydrostatic pressure up to 8.5 GPa. The stoichiometric GeSe{sub 2} and GeS{sub 2} glasses exhibit elastic behavior in the pressure range up to 3 GPa, and their bulk modulus decreases at pressures higher than 2–2.5 GPa. At higher pressures, inelastic relaxation processes begin and their intensity is proportional to the logarithm of time. The relaxation rate for the GeSe{sub 2} glasses has a pronounced maximum at 3.5–4.5 GPa, which indicates the existence of several parallel structural transformation mechanisms.more » The nonstoichiometric glasses exhibit a diffuse transformation and inelastic behavior at pressures above 1–2 GPa. The maximum relaxation rate in these glasses is significantly lower than that in the stoichiometric GeSe{sub 2} glasses. All glasses are characterized by the “loss of memory” of history: after relaxation at a fixed pressure, the further increase in the pressure returns the volume to the compression curve obtained without a stop for relaxation. After pressure release, the residual densification in the stoichiometric glasses is about 7% and that in the Ge{sub 17}Se{sub 83} glasses is 1.5%. The volume of the Ge{sub 8}Se{sub 92} glass returns to its initial value within the limits of experimental error. As the pressure decreases, the effective bulk moduli of the Ge{sub 17}Se{sub 83} and Ge{sub 8}Se{sub 92} glasses coincide with the moduli after isobaric relaxation at the stage of increasing pressure, and the bulk modulus of the stoichiometric GeSe{sub 2} glass upon decreasing pressure noticeably exceeds the bulk modulus after isobaric relaxation at the stage of increasing pressure. Along with the reported data, our results can be used to draw conclusions regarding the diffuse transformations in glassy germanium chalcogenides during compression.« less

High-pressure anaerobic digestion up to 100 bar: influence of initial pressure on production kinetics and specific methane yields.

PubMed

Merkle, Wolfgang; Baer, Katharina; Haag, Nicola Leonard; Zielonka, Simon; Ortloff, Felix; Graf, Frank; Lemmer, Andreas

2017-02-01

To ensure an efficient use of biogas produced by anaerobic digestion, in some cases it would be advisable to upgrade the biogenic gases and inject them into the transnational gas grids. To investigate biogas production under high-pressure conditions up to 100 bar, new pressure batch methane reactors were developed for preliminary lab-scale experiments with a mixture of grass and maize silage hydrolysate. During this investigation, the effects of different initial pressures (1, 50 and 100 bar) on pressure increase, gas production and the specific methane yield using nitrogen as inert gas were determined. Based on the experimental findings increasing initial pressures alter neither significantly, further pressure increases nor pressure increase rates. All supplied organic acids were degraded and no measurable inhibition of the microorganisms was observed. The results show that methane reactors can be operated at operating pressures up to 100 bar without any negative effects on methane production.

Pressure ulcers in elderly patients with hip fracture across the continuum of care.

PubMed

Baumgarten, Mona; Margolis, David J; Orwig, Denise L; Shardell, Michelle D; Hawkes, William G; Langenberg, Patricia; Palmer, Mary H; Jones, Patricia S; McArdle, Patrick F; Sterling, Robert; Kinosian, Bruce P; Rich, Shayna E; Sowinski, Janice; Magaziner, Jay

2009-05-01

To identify care settings associated with greater pressure ulcer risk in elderly patients with hip fracture in the postfracture period. Prospective cohort study. Nine hospitals that participate in the Baltimore Hip Studies network and 105 postacute facilities to which patients from these hospitals were discharged. Hip fracture patients aged 65 and older who underwent surgery for hip fracture. A full-body skin examination was conducted at baseline (as soon as possible after hospital admission) and repeated on alternating days for 21 days. Patients were deemed to have an acquired pressure ulcer (APU) if they developed one or more new stage 2 or higher pressure ulcers after hospital admission. In 658 study participants, the APU cumulative incidence at 32 days after initial hospital admission was 36.1% (standard error 2.5%). The adjusted APU incidence rate was highest during the initial acute hospital stay (relative risk (RR)=2.2, 95% confidence interval (CI)=1.3-3.7) and during re-admission to the acute hospital (RR=2.2, 95% CI=1.1-4.2). The relative risks in rehabilitation and nursing home settings were 1.4 (95% CI=0.8-2.3) and 1.3 (95% CI=0.8-2.1), respectively. Approximately one-third of hip fracture patients developed an APU during the study period. The rate was highest in the acute setting, a finding that is significant in light of Medicare's policy of not reimbursing hospitals for the treatment of hospital-APUs. Hip fracture patients constitute an important group to target for pressure ulcer prevention in hospitals.

In Vitro Evaluation of Evacuated Blood Collection Tubes as a Closed-Suction Surgical Drain Reservoir.

PubMed

Heiser, Brian; Okrasinski, E B; Murray, Rebecca; McCord, Kelly

The initial negative pressures of evacuated blood collection tubes (EBCT) and their in vitro performance as a rigid closed-suction surgical drain (CSSD) reservoir has not been evaluated in the scientific literature despite being described in both human and veterinary texts and journals. The initial negative pressures of EBCT sized 3, 6, 10, and 15 mL were measured and the stability of the system monitored. The pressure-to-volume curve as either air or water was added and maximal filling volumes were measured. Evacuated blood collection tubes beyond the manufacture's expiration date were evaluated for initial negative pressures and maximal filling volumes. Initial negative pressure ranged from -214 mm Hg to -528 mm Hg for EBCT within the manufacturer's expiration date. Different pressure-to-volume curves were found for air versus water. Optimal negative pressures of CSSD are debated in the literature. Drain purpose and type of exudates are factors that should be considered when deciding which EBCT size to implement. Evacuated blood collection tubes have a range of negative pressures and pressure-to-volume curves similar to previously evaluated CSSD rigid reservoirs. Proper drain management and using EBCT within labeled expiration date are important to ensure that expected negative pressures are generated.

Can heart rate predict blood pressure response to anti-hypertensive drug therapy?

PubMed

Owens, P E; Lyons, S; O'Brien, E

1998-04-01

The use of heart rate in clinical practice is limited by its variability under measurement situations. The mean heart rate on ambulatory monitoring provides a more robust statistic for clinical use. We examined the relationship between mean heart rate on initial referral ambulatory blood pressure monitoring (ABPM) to the BP-lowering efficacy of the four main groups of anti-hypertensive medications, in a referral hypertensive population. Patients were retrospectively identified by review of the BP database, and data collected from the initial referral BP monitor off medication, and the subsequent ABPM after treatment with either beta-blockers, diuretics, calcium antagonists or angiotensin-converting enzyme (ACE) inhibitors. The change in mean arterial BP from the initial to the subsequent ABPM (ie, as a result of treatment) was correlated with the mean heart rate on the initial ABPM. A moderate association was found for initial daytime heart rate and BP response to beta-blockers (r = 0.24, P = 0.02), and ACE inhibitors (r = 0.14, P = 0.05). No such association was found for calcium antagonists or diuretics. When the groups were divided into those with a mean daytime heart rate <75 and > or =75 beats per min, BP reduction from beta-blocker and ACE inhibitor therapy was significantly greater in those patients with a higher daytime heart rate. We conclude that average daytime heart rate on pre-treatment ABPM can be useful as a predictor of BP response to beta-blockade or ACE inhibition.

Hypertonic 15% sodium pyruvate offers no initial resuscitation advantage compared with 8% hypertonic NACl in sheep with multiple hemorrhages.

PubMed

do Nascimento, Paulo; Vaid, Sumreen U; Hoskins, Stephen L; Espana, Jonathan M; Kinsky, Michael P; Kramer, George C

2007-05-01

Initial fluid resuscitation of hemorrhagic shock might be enhanced by the infusion of monocarboxylate-energy substrates. We evaluated hemodynamics, metabolism, and fluid dynamics for initial resuscitation of hemorrhage using small volume 15% sodium pyruvate solution (HPY) compared with osmotically matched 8% hypertonic saline (HS). Instrumented conscious sheep were hemorrhaged 25 mL/kg at time zero through 15 min (T0-T15) and 5 mL/kg for 5 min at T50 to T55 and T70 to T75. Fluid resuscitation from T30 to T180 was performed by a computer-controlled closed-loop system, which titrated infusion rate to a mean arterial pressure of 90 mmHg. Initial infusion was 4 mL/kg of either HPY or HS, followed by the administration of lactated Ringer. Both HPY and HS restored cardiac index similarly. The lactate/pyruvate ratio was used to assess metabolic debt and was significantly higher (T180), whereas oxygen delivery was significantly lower (T120) with HPY versus HS. Total fluid administered was similar, with 43.7 +/- 6.2 mL/kg for HPY and 39.4 +/- 6.8 mL/kg for HS. Plasma volume was similarly increased and approached baseline values for both groups. Initial resuscitation with small volume HPY offered no hemodynamic or metabolic advantage compared with small volume HS when the fluids were infused to an end point pressure.

Intralipid™ administration attenuates the hypotensive effects of acute intravenous amiodarone overdose in a swine model.

PubMed

Xanthos, Theodoros; Psichalakis, Nikolaos; Russell, David; Papalois, Apostolos; Koutsovasilis, Anastasios; Athanasopoulos, Dimitrios; Gkiokas, Georgios; Chalkias, Athanasios; Iacovidou, Nicoletta

2016-08-01

To investigate whether a lipid emulsion could counteract the hypotensive effects of amiodarone overdose after an acute intravenous administration and improve 4 h survival in an established model of swine cardiovascular research. Twenty pigs were intubated and instrumented to measure aortic pressures and central venous pressures (CVP). After allowing the animals to stabilize for 60 minutes, amiodarone overdose (1 mg/kg/min) was initiated for a maximum of 20 minutes. Afterwards, the animals were randomized into 2 groups. Group A (n = 10) received 0.9% Normal Saline (NS) and Group B (n = 10) received 20% Intralipid® (ILE). A bolus dose of 2 ml/kg in over 2 min time was initially administered in both groups followed by a 45 min infusion (0.2 ml/kg/min) of either NS or ILE. All animals survived the overdose and all animals survived the monitoring period of 4 hours. Systolic aortic pressure (SpthAorta) (6.90 vs 14.10 mmHg, P = .006) and mean arterial pressure (MAP) (6.10 vs 14.90 mmHg, P = .001) were higher in the ILE group 2 min after the bolus ILE infusion. This difference was maintained for 15 min after ILE infusion for both SpthAorta (7.85 vs 13.15 mmHg, P = .044) and MAP (7.85 vs 13.15 mmHg, P = .042). Animals that received ILE had higher CVP (11.6 vs 15.7 mmHg, P = .046), an effect which was attenuated 2 and 4 hours post administration. Animals receiving ILE were more acidotic (7.21 vs 7.38, P = .048) in the monitoring period compared to animals receiving NS. Intralipid attenuated the hypotensive effects of amiodarone toxicity for a period of 15 minutes compared to animals receiving NS. Copyright © 2016 Elsevier Inc. All rights reserved.

Interindividual differences in the clinical effectiveness of liraglutide in Type 2 diabetes: a real-world retrospective study conducted in Spain.

PubMed

Gomez-Peralta, F; Lecube, A; Fernández-Mariño, A; Alonso Troncoso, I; Morales, C; Morales-Pérez, F M; Guler, I; Cadarso-Suárez, C

2018-06-26

To study the response of clinical variables (HbA 1c , body weight, lipid profile and blood pressure) over 24 months of liraglutide treatment in a real-world clinical setting, and to describe the evolution of HbA 1c and body weight reduction in response to liraglutide treatment by employing generalized additive mixed models (GAMMs). We included people aged ≥ 18 years with Type 2 diabetes mellitus that initiated liraglutide treatment between November 2011 and May 2015. Demographic and clinical data were retrieved retrospectively over 24 months from electronic medical records with a median duration of observation of 7.0 (IQR 3.0-12.0) months. Individuals that initiated liraglutide therapy were obese (BMI 39.1 kg/m 2 ), with inadequate HbA 1c (68 mmol/mol [8.4%)], blood pressure and lipid levels. Upon liraglutide treatment, HbA 1c , body weight, mean systolic and diastolic blood pressure, and lipid levels decreased gradually. GAMMs demonstrated that longer treatment with liraglutide was a predictor of improved HbA 1c response, whereas higher baseline HbA 1c , longer Type 2 diabetes duration and treatment with insulin were predictors of worse HbA 1c response. Higher baseline weight, longer treatment with liraglutide and the interaction between metformin and time were predictors of improved weight response. In this real-world study, we showed the effectiveness of liraglutide in improving body weight, HbA 1c , mean systolic and diastolic blood pressure, and lipid levels. GAMMs indicated that baseline HbA 1c and weight, time of treatment with liraglutide, diabetes duration and the use of metformin or insulin are predictors of clinical response to liraglutide. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Liquid atomization in supersonic flows

NASA Astrophysics Data System (ADS)

Missoum, Azzedine

An experimental investigation of the atomization of a round liquid jet by coaxial, costream injection into a supersonic, Mach 1.5 air flow is reported. Extensive flow visualization was conducted using schlieren/shadowgraph, flash photography, and short duration (ns) laser imaging. The finer details of the jet were revealed when viewed under high magnification with the help of a microscope. The liquid and air pressures were varied individually. Photographic evidence indicates the presence of three regions within the liquid jet: a primary region enclosed by the first shock cell where the primary breakup occurs, a secondary region in which the jet is totally broken because of its interaction with the supersonic wave structure, and a third, subsonic region further downstream. It was found that the breakup mechanism of liquid jets in supersonic airstreams is quite complex. The breakup seems to be initiated by the growth of the turbulent structure on the liquid surface and the subsequent detachment of the three-dimensional structure as fine droplets by the intense shear at the liquid-gas interface. This seems to confirm the boundary layer stripping mechanism. The liquid jet expands into a bubble like formation as it interacts with the first set of waves. Higher liquid injection pressures resulted in higher initial spray angles. The liquid jet displayed a geometry strongly dependent on the pressure distribution resulting from the wave structure present in the supersonic jet. Droplet size and velocity distributions were measured by the P/DPA (Phase/Doppler Particle Analyzer) system. The Sauter Mean Diameter (SMD) was measured at several axial and radial locations at various liquid and air pressures. The SMD shows a decrease with increase in both the air-to-liquid mass flow ratio and the Weber number. The drop size decreased towards the outer edges of the jet. The results lead one to conclude that the coaxial, coflowing configuration is very attractive for atomizing scramjet liquid fuels.

Lack of nocturnal blood pressure fall in elderly bedridden hypertensive patients with cerebrovascular disease.

PubMed

Sasaki, Masato; Ando, Hitoshi; Fujimura, Akio

2012-02-01

To prevent recurrence of cerebrovascular disease (CVD), adequate control of blood pressure (BP) is extremely important for the treatment of hypertensive CVD patients. As absence of the nocturnal fall of BP by the expected 10-20% from daytime levels is reported to exaggerate target organ injury, 24-h ambulatory blood pressure monitoring (ABPM) was conducted, especially to obtain data during nighttime sleep. Forty-eight elderly bedridden chronic phase CVD hypertensive patients (assessed 1-3 mo after CVD accident) participated. As a group, nocturnal BP was higher than diurnal BP, whereas nocturnal pulse rate was lower than diurnal pulse rate. The nocturnal BP fall was blunted in most (∼90%) of the patients. These results suggest that to perform a rational drug treatment, it is essential to do 24-h ABPM before initiation of antihypertensive therapy in elderly bedridden hypertensive CVD patients.

Lower blood pressure and risk of cisplatin nephrotoxicity: a retrospective cohort study.

PubMed

Komaki, Kazumi; Kusaba, Tetsuro; Tanaka, Mai; Kado, Hiroshi; Shiotsu, Yayoi; Matsui, Masahiro; Shiozaki, Atsushi; Nakano, Hiroshi; Ishikawa, Takeshi; Fujiwara, Hitoshi; Konishi, Hideyuki; Itoh, Yoshito; Matoba, Satoaki; Tamagaki, Keiichi

2017-02-20

The pathophysiological mechanisms of cisplatin nephrotoxicity include the reduction of renal blood flow, as well as tubular epithelial cell toxicity. The objective of this study was to investigate the influence of lower blood pressure and decreased food intake on the incidence of cisplatin nephrotoxicity. We conducted a retrospective cohort study at a university hospital between 2011 and 2012. We identified hospitalized adult patients with head and neck cancer, esophageal cancer, or gastric cancer, who received intravenous cisplatin administration. The primary outcome was the incidence of cisplatin nephrotoxicity defined as the increase in serum creatinine after cisplatin administration more than 1.5 times from baseline. The study participants included 182 patients, in whom we observed a total of 442 cycles of cisplatin chemotherapy. The incidence of cisplatin nephrotoxicity was observed in 41 of 182 cycles with initial administration. Multivariate logistic regression analysis showed that systolic blood pressure was independently associated with cisplatin nephrotoxicity (adjusted odds ratio 0.75, 95% confidence interval 0.57 to 0.95 for each 10 mmHg). The use of renin-angiotensin system (RAS) inhibitors was also associated with cisplatin nephrotoxicity (3.39, 1.30 to 8.93). Among quartiles of systolic blood pressure in all cycles of chemotherapy, the incidence of nephrotoxicity in the lower blood pressure group was significantly higher than that in the higher blood pressure group for patients taking non-solid food (P = 0.037), while there was no significant difference for patients taking solid food (P = 0.67). Lower blood pressure and the use of RAS inhibitors were associated with the incidence of cisplatin nephrotoxicity, and lower blood pressure had a greater influence on nephrotoxicity in patients who could not take solid food. Discontinuation of antihypertensive medication including RAS inhibitors before cisplatin chemotherapy should be considered, which may be beneficial for patients with lower blood pressure.

Optimization of a heterogeneous catalytic hydrodynamic cavitation reactor performance in decolorization of Rhodamine B: application of scrap iron sheets.

PubMed

Basiri Parsa, Jalal; Ebrahimzadeh Zonouzian, Seyyed Alireza

2013-11-01

A low pressure pilot scale hydrodynamic cavitation (HC) reactor with 30 L volume, using fixed scrap iron sheets, as the heterogeneous catalyst, with no external source of H2O2 was devised to investigate the effects of operating parameters of the HC reactor performance. In situ generation of Fenton reagents suggested an induced advanced Fenton process (IAFP) to explain the enhancing effect of the used catalyst in the HC process. The reactor optimization was done based upon the extent of decolorization (ED) of aqueous solution of Rhodamine B (RhB). To have a perfect study on the pertinent parameters of the heterogeneous catalyzed HC reactor, the following cases as, the effects of scrap iron sheets, inlet pressure (2.4-5.8 bar), the distance between orifice plates and catalyst sheets (submerged and inline located orifice plates), back-pressure (2-6 bar), orifice plates type (4 various orifice plates), pH (2-10) and initial RhB concentration (2-14 mg L(-1)) have been investigated. The results showed that the highest cavitational yield can be obtained at pH 3 and initial dye concentration of 10 mg L(-1). Also, an increase in the inlet pressure would lead to an increase in the ED. In addition, it was found that using the deeper holes (thicker orifice plates) would lead to lower ED, and holes with larger diameter would lead to the higher ED in the same cross-sectional area, but in the same holes' diameters, higher cross-sectional area leads to the lower ED. The submerged operation mode showed a greater cavitational effects rather than the inline mode. Also, for the inline mode, the optimum value of 3 bar was obtained for the back-pressure condition in the system. Moreover, according to the analysis of changes in the UV-Vis spectra of RhB, both degradation of RhB chromophore structure and N-deethylation were occurred during the catalyzed HC process. Copyright © 2013 Elsevier B.V. All rights reserved.

Thermodynamic models for bounding pressurant mass requirements of cryogenic tanks

NASA Technical Reports Server (NTRS)

Vandresar, Neil T.; Haberbusch, Mark S.

1994-01-01

Thermodynamic models have been formulated to predict lower and upper bounds for the mass of pressurant gas required to pressurize a cryogenic tank and then expel liquid from the tank. Limiting conditions are based on either thermal equilibrium or zero energy exchange between the pressurant gas and initial tank contents. The models are independent of gravity level and allow specification of autogenous or non-condensible pressurants. Partial liquid fill levels may be specified for initial and final conditions. Model predictions are shown to successfully bound results from limited normal-gravity tests with condensable and non-condensable pressurant gases. Representative maximum collapse factor maps are presented for liquid hydrogen to show the effects of initial and final fill level on the range of pressurant gas requirements. Maximum collapse factors occur for partial expulsions with large final liquid fill fractions.

Parameter setting and analysis of a dynamic tubular SOFC model

NASA Astrophysics Data System (ADS)

Jiang, Wei; Fang, Ruixian; Khan, Jamil A.; Dougal, Roger A.

An improved one-dimensional dynamic model of a tubular SOFC stack capable of system simulation in the virtual test bed (VTB) simulation environment is presented in this paper. This model is based on the electrochemical and thermal modeling, accounting for the voltage losses and temperature dynamics. The modeling of an external reformer is also included in this study. A detailed parametric analysis of working conditions and cell configuration of the solid oxide fuel cell (SOFC) stack is the main focus of this paper. The following operating parameters are investigated: pressure ratio, temperature, mass flow rate, external reforming degree and stream to carbon (S/C) ratio. The cell geometric parameters studied include cell diameter and cell length. Elevated operating pressure improves the cell performance. Whereas, higher operating temperature decreases both the Nernst potential and the irreversible losses, resulting in an initial increase then a decrease in cell efficiency. It was found that a higher S/C ratio yields a lower H 2 concentration and partial pressure, which has a negative effect on the Nernst potential. Increased cell diameter is found to increase the power due to a larger activation area at the same time and due to longer current path length there is an increase in the ohmic loss. Increased length of the cell has the undesired affect of an increased pressure drop.

Effects of low-dye taping on plantar pressure pre and post exercise: an exploratory study.

PubMed

Nolan, Damien; Kennedy, Norelee

2009-04-21

Low-Dye taping is used for excessive pronation at the subtalar joint of the foot. Previous research has focused on the tape's immediate effect on plantar pressure. Its effectiveness following exercise has not been investigated. Peak plantar pressure distribution provides an indirect representation of subtalar joint kinematics. The objectives of the study were 1) To determine the effects of Low-Dye taping on peak plantar pressure immediately post-application. 2) To determine whether any initial effects are maintained following exercise. 12 asymptomatic subjects participated; each being screened for excessive pronation (navicular drop > 10 mm). Plantar pressure data was recorded, using the F-scan, at four intervals during the testing session: un-taped, baseline-taped, post-exercise session 1, and post-exercise session 2. Each exercise session consisted of a 10-minute walk at a normal pace. The foot was divided into 6 regions during data analysis. Repeated-measures analysis of variance (ANOVA) was used to assess regional pressure variations across the four testing conditions. Reduced lateral forefoot peak plantar pressure was the only significant difference immediately post tape application (p = 0.039). This effect was lost after 10 minutes of exercise (p = 0.036). Each exercise session resulted in significantly higher medial forefoot peak pressure compared to un-taped; (p = 0.015) and (p = 0.014) respectively, and baseline-taped; (p = 0.036) and (p = 0.015) respectively. Medial and lateral rearfoot values had also increased after the second session (p = 0.004), following their non-significant reduction at baseline-taped. A trend towards a medial-to-lateral shift in pressure present in the midfoot immediately following tape application was still present after 20 minutes of exercise. Low-Dye tape's initial effect of reduced lateral forefoot peak plantar pressure was lost after a 10-minute walk. However, the tape continued to have an effect on the medial forefoot after 20 minutes of exercise. Further studies with larger sample sizes are required to examine the important finding of the anti-pronatory trend present in the midfoot.

Optimized surgical treatment for normal pressure hydrocephalus: comparison between gravitational and differential pressure valves.

PubMed

Suchorska, B; Kunz, M; Schniepp, R; Jahn, K; Goetz, C; Tonn, J C; Peraud, A

2015-04-01

In idiopathic normal pressure hydrocephalus (NPH) ventriculoperitoneal (VP) shunt insertion is the method of choice to improve cardinal symptoms such as gait disturbance, urge incontinence and/or dementia. With reduced compliance, the brain of the elderly is prone for overdrainage complications. This was especially true with the use of differential pressure valve implantation. The present study compares clinical outcome and complication rates after VP shunt insertion with differential pressure valves in the early years and gravitational valves since 2005. The authors reviewed patients treated at our institution for NPH since 1995. Differential pressure valves were solely used in the initial years, while the treatment regimen changed to gravitational valves in 2005. Clinical improvement/surgical success rates as well as complications were compared between the two groups. Eighty-nine patients were enrolled for the present study. Mean age at the time of surgery was 73.5 ± 6.3 years. Male patients predominated with 73, compared with 16 female patients. Median follow-up time was 28 ± 26 months. Date of last follow-up was 1st October 2013. Forty-nine patients received a gravitational valve, while 40 were treated with differential pressure valves. In the gravitational group a significant improvement was observed after shunt insertion for gait disorder, cognitive impairment and urge incontinence (p < 0.0001, resp. p = 0.004), while a significant change in the differential pressure group was only seen for gait disorder (p = 0.03) but not for cognition or urinary incontinency (p > 0.05). The risk of hygroma as a sign of shunt overdrainage requiring surgical intervention was significantly higher in the differential pressure group (5 versus 0 in the gravitational group). Patients with NPH treated with gravitational valves in the present cohort showed a more profound improvement in their initial symptoms, including gait disorder, cognitive impairment and urinary incontinency without the risk of overdrainage complications requiring surgical intervention when compared with patients who received differential pressure valves in previous years.

Hydrothermal stability of SAPO-34 for refrigeration and air conditioning applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Haijun; Cui, Qun, E-mail: cuiqun@njtech.edu.cn; Wu, Juan

Graphical abstract: The SAPO-34 was synthesized by a hydrothermal method using diethylamine as a template. Water adsorption strength on SAPO-34 is between that on 13X and A type silica gel. During 100–400 Pa, the water uptake on SAPO-34 increases sensitively to pressure, and equilibrium water uptake reaches 0.35 kg/kg, 25% higher than 13X. SAPO-34 shows no significant reduced cyclic water uptake over 60 cycles. Most of the initial SAPO-34 phase is restored, while the regular cubic-like morphology is well maintained, and the specific surface area only decreases by 8.6%. - Highlights: • Water adsorption strength on SAPO-34 is between thatmore » on 13X and A type silica gel. During 100–400 Pa, the water uptake on SAPO-34 increases sensitively to pressure, and equilibrium water uptake reaches 0.35 kg/kg, 25% higher than 13X. • SAPO-34 with diethylamine as the template shows no significant reduced cyclic water uptake over 60 cycles, and most of the initial SAPO-34 phase is well maintained. • SAPO-34 has an excellent adsorption performance and a good hydrothermal stability, thus is promising for application in adsorption refrigeration. - Abstract: Hydrothermal stability is one of the crucial factors in applying SAPO-34 molecular sieve to adsorption refrigration. The SAPO-34 was synthesized by a hydrothermal method using diethylamine as a template. Both a vacuum gravimetric method and an intelligent gravimetric analyzer were applied to analyze the water adsorption performance of SAPO-34. Cyclic hydrothermal performance was determined on the modified simulation adsorption refrigeration test rig. Crystal phase, morphology, and porosity of SAPO-34 were characterized by X-ray diffraction, scanning electron microscopy, and N{sub 2} sorption, respectively. The results show that, water adsorption strength on SAPO-34 is between that on 13X and A type silica gel. During 100–400 Pa, the water uptake on SAPO-34 increases sensitively to pressure, and equilibrium water uptake reaches 0.35 kg/kg, 25% higher than 13X. SAPO-34 shows no significant reduced cyclic water uptake over 60 cycles. Most of the initial SAPO-34 phase is restored, while the regular cubic-like morphology is well maintained, and the specific surface area only decreases by 8.6%.« less

Glass Transition Temperature and Density Scaling in Cumene at Very High Pressure.

PubMed

Ransom, T C; Oliver, W F

2017-07-14

We present a new method that allows direct measurements of the glass transition temperature T_{g} at pressures up to 4.55 GPa in the glass-forming liquid cumene (isopropylbenzene). This new method uses a diamond anvil cell and can measure T_{g} at pressures of 10 GPa or greater. Measuring T_{g} at the glass→liquid transition involves monitoring the disappearance of pressure gradients initially present in the glass, but also takes advantage of the large increase in the volume expansion coefficient α_{p} at T_{g} as the supercooled or superpressed liquid is entered. Accurate T_{g}(P) values in cumene allow us to show that density scaling holds along this isochronous line up to pressures much higher than any previous study, corresponding to a density increase of 29%. Our results for cumene over this huge compression range yield ρ^{γ}/T=C, where C is a constant and where γ=4.77±0.02 for this nonassociated glass-forming system. Finally, high-pressure cumene viscosity data from the literature taken at much lower pressures and at several different temperatures, corresponding to a large dynamic range of nearly 13 orders of magnitude, are shown to superimpose on a plot of η vs ρ^{γ}/T for the same value of γ.

HPHT reservoir evolution: a case study from Jade and Judy fields, Central Graben, UK North Sea

NASA Astrophysics Data System (ADS)

di Primio, Rolando; Neumann, Volkmar

2008-09-01

3D basin modelling of a study area in Quadrant 30, UK North Sea was performed in order to elucidate the burial, thermal, pressure and hydrocarbon generation, migration and accumulation history in the Jurassic and Triassic high pressure high temperature sequences. Calibration data, including reservoir temperatures, pressures, petroleum compositional data, vitrinite reflectance profiles and published fluid inclusion data were used to constrain model predictions. The comparison of different pressure generating processes indicated that only when gas generation is taken into account as a pressure generating mechanism, both the predicted present day as well as palaeo-pressure evolution matches the available calibration data. Compositional modelling of hydrocarbon generation, migration and accumulation also reproduced present and palaeo bulk fluid properties such as the reservoir fluid gas to oil ratios. The reconstruction of the filling histories of both reservoirs indicates that both were first charged around 100 Ma ago and contained initially a two-phase system in which gas dominated volumetrically. Upon burial reservoir fluid composition evolved to higher GORs and became undersaturated as a function of increasing pore pressure up to the present day situation. Our results indicate that gas compositions must be taken into account when calculating the volumetric effect of gas generation on overpressure.

Blood pressure in firefighters, police officers, and other emergency responders.

PubMed

Kales, Stefanos N; Tsismenakis, Antonios J; Zhang, Chunbai; Soteriades, Elpidoforos S

2009-01-01

Elevated blood pressure is a major risk factor for cardiovascular morbidity and mortality. Increased risk begins in the prehypertensive range and increases further with higher pressures. The strenuous duties of emergency responders (firefighters, police officers, and emergency medical services (EMS) personnel) can interact with their personal risk profiles, including elevated blood pressure, to precipitate acute cardiovascular events. Approximately three-quarters of emergency responders have prehypertension or hypertension, a proportion which is expected to increase, based on the obesity epidemic. Elevated blood pressure is also inadequately controlled in these professionals and strongly linked to cardiovascular disease morbidity and mortality. Notably, the majority of incident cardiovascular disease events occur in responders who are initially prehypertensive or only mildly hypertensive and whose average premorbid blood pressures are in the range in which many physicians would hesitate to prescribe medications (140-146/88-92). Laws mandating public benefits for emergency responders with cardiovascular disease provide an additional rationale for aggressively controlling their blood pressure. This review provides a background on emergency responders, summarizes occupational risk factors for hypertension and the metabolic syndrome, their prevalence of elevated blood pressure, and evidence linking hypertension with adverse outcomes in these professions. Next, discrepancies between relatively outdated medical standards for emergency responders and current, evidence-based guidelines for blood pressure management in the general public are highlighted. Finally, a workplace-oriented approach for blood pressure control among emergency responders is proposed, based on the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.

A study on electrode gels for skin conductance measurements.

PubMed

Tronstad, Christian; Johnsen, Gorm Krogh; Grimnes, Sverre; Martinsen, Ørjan G

2010-10-01

Low-frequency skin conductance is used within several clinical applications and is mainly sensitive to sweating and the moisture content of the stratum corneum, but also how electrodes introduce changes in the electrical properties. Four electrode gels were investigated with regard to sorption characteristics and electrical properties. Skin conductance time series were collected from 18 test subjects during relaxation, exercise and recovery, wearing different pairs of electrodes contralaterally on the hypothenar and the T9 dermatome. Pressure test was applied on the T9 electrodes. Impedance frequency sweeps were taken on the T9 electrodes the same day and the next, parameterized to the Cole model. ANOVA on the initial skin conductance level change, exercise response amplitude, recovery offset and pressure-induced changes revealed significant differences among gel types. The wetter gels caused a higher positive level change, a greater response amplitude, larger recovery offset and greater pressure-induced artifacts compared to the solid gels. Sweating on the T9 site led to negative skin conductance responses for the wetter gels. Correlations were found between the desorption measurements and the initial skin conductance level change (hypothenar: R = 0.988 T9: R = 0.901) RM-ANOVA on the Cole parameters revealed a significant decrease in R(s) of the most resistive gel. Clinical implications are discussed.

Self-pressurization of a flightweight liquid hydrogen storage tank subjected to low heat flux

NASA Technical Reports Server (NTRS)

Hasan, M. M.; Lin, C. S.; Vandresar, N. T.

1991-01-01

Results are presented for an experimental investigation of self-pressurization and thermal stratification of a 4.89 cu m liquid hydrogen (LH2) storage tank subjected to low heat flux (0.35, 2.0, and 3.5 W/sq m) under normal gravity conditions. Tests were performed at fill levels of 83 to 84 percent (by volume). The LH2 tank was representative of future spacecraft tankage, having a low mass-to-volume ratio and high performance multilayer thermal insulation. Results show that the pressure rise rate and thermal stratification increase with increasing heat flux. At the lowest heat flux, the pressure rise rate is comparable to the homogenous rate, while at the highest heat flux, the rate is more than three times the homogeneous rate. It was found that initial conditions have a significant impact on the initial pressure rise rate. The quasi-steady pressure rise rates are nearly independent of the initial condition after an initial transient period has passed.

The role of propagule pressure, genetic diversity and microsite availability for Senecio vernalis invasion.

PubMed

Erfmeier, Alexandra; Hantsch, Lydia; Bruelheide, Helge

2013-01-01

Genetic diversity is supposed to support the colonization success of expanding species, in particular in situations where microsite availability is constrained. Addressing the role of genetic diversity in plant invasion experimentally requires its manipulation independent of propagule pressure. To assess the relative importance of these components for the invasion of Senecio vernalis, we created propagule mixtures of four levels of genotype diversity by combining seeds across remote populations, across proximate populations, within single populations and within seed families. In a first container experiment with constant Festuca rupicola density as matrix, genotype diversity was crossed with three levels of seed density. In a second experiment, we tested for effects of establishment limitation and genotype diversity by manipulating Festuca densities. Increasing genetic diversity had no effects on abundance and biomass of S. vernalis but positively affected the proportion of large individuals to small individuals. Mixtures composed from proximate populations had a significantly higher proportion of large individuals than mixtures composed from within seed families only. High propagule pressure increased emergence and establishment of S. vernalis but had no effect on individual growth performance. Establishment was favoured in containers with Festuca, but performance of surviving seedlings was higher in open soil treatments. For S. vernalis invasion, we found a shift in driving factors from density dependence to effects of genetic diversity across life stages. While initial abundance was mostly linked to the amount of seed input, genetic diversity, in contrast, affected later stages of colonization probably via sampling effects and seemed to contribute to filtering the genotypes that finally grew up. In consequence, when disentangling the mechanistic relationships of genetic diversity, seed density and microsite limitation in colonization of invasive plants, a clear differentiation between initial emergence and subsequent survival to juvenile and adult stages is required.

Explosion characteristics of LPG-air mixtures in closed vessels.

PubMed

Razus, Domnina; Brinzea, Venera; Mitu, Maria; Oancea, D

2009-06-15

The experimental study of explosive combustion of LPG (liquefied petroleum gas)-air mixtures at ambient initial temperature was performed in two closed vessels with central ignition, at various total initial pressures within 0.3-1.3bar and various fuel/air ratios, within the flammability limits. The transient pressure-time records were used to determine several explosion characteristics of LPG-air: the peak explosion pressure, the explosion time (the time necessary to reach the peak pressure), the maximum rate of pressure rise and the severity factor. All explosion parameters are strongly dependent on initial pressure of fuel-air mixture and on fuel/air ratio. The explosion characteristics of LPG-air mixtures are discussed in comparison with data referring to the main components of LPG: propane and butane, obtained in identical conditions.

Laser-Induced Fluorescence Measurements and Modeling of Nitric Oxide in Counterflow Diffusion Flames

NASA Technical Reports Server (NTRS)

Ravikrishna, Rayavarapu V.

2000-01-01

The feasibility of making quantitative nonintrusive NO concentration ([NO]) measurements in nonpremixed flames has been assessed by obtaining laser-induced fluorescence (LIF) measurements of [NO] in counterflow diffusion flames at atmospheric and higher pressures. Comparisons at atmospheric pressure between laser-saturated fluorescence (LSF) and linear LIF measurements in four diluted ethane-air counterflow diffusion flames with strain rates from 5 to 48/s yielded excellent agreement from fuel-lean to moderately fuel-rich conditions, thus indicating the utility of a model-based quenching correction technique, which was then extended to higher pressures. Quantitative LIF measurements of [NO] in three diluted methane-air counterflow diffusion flames with strain rates from 5 to 35/s were compared with OPPDIF model predictions using the GRI (version 2.11) chemical kinetic mechanism. The comparisons revealed that the GRI mechanism underpredicts prompt-NO by 30-50% at atmospheric pressure. Based on these measurements, a modified reaction rate coefficient for the prompt-NO initiation reaction was proposed which causes the predictions to match experimental data. Temperature measurements using thin filament pyrometry (TFP) in conjunction with a new calibration method utilizing a near-adiabatic H2-air Hencken burner gave very good comparisons with model predictions in these counterflow diffusion flames. Quantitative LIF measurements of [NO] were also obtained in four methane-air counterflow partially-premixed flames with fuel-side equivalence ratios (phi(sub B)) of 1.45, 1.6, 1.8 and 2.0. The measurements were in excellent agreement with model predictions when accounting for radiative heat loss. Spatial separation between regions dominated by the prompt and thermal NO mechanisms was observed in the phi(sub B) = 1.45 flame. The modified rate coefficient proposed earlier for the prompt-NO initiation reaction improved agreement between code predictions and measurements in the region where prompt-NO dominates. Finally, LIF measurements of NO were obtained in counterflow diffusion flames at 2 to 5 atm. Comparisons between [NO] measurements and predictions show that the GRI mechanism underpredicts prompt-NO by a factor of two to three at all pressures. In general, the results indicate a need for refinement of the CH chemistry, especially the pressure-dependent CH formation and destruction reactions.

Supercritical extraction of lycopene from tomato industrial wastes with ethane.

PubMed

Nobre, Beatriz P; Gouveia, Luisa; Matos, Patricia G S; Cristino, Ana F; Palavra, António F; Mendes, Rui L

2012-07-11

Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds) was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO₂ and a near critical mixture of ethane and propane). The recovery of all-E-lycopene increased with pressure, decreased with the increase of the particle size in the initial stages of the extraction and was not practically affected by the solvent superficial velocity. The effect of the temperature was more complex. When the temperature increased from 40 to 60 °C the recovery of all-E-lycopene increased from 80 to 90%. However, for a further increase to 80 °C, the recovery remained almost the same, indicating that some E-Z isomerization could have occurred, as well as some degradation of lycopene. The recovery of all-E-lycopene was almost the same for feed samples with different all-E-lycopene content. Furthermore, when a batch with a higher all-E-lycopene content was used, supercritical ethane and a near critical mixture of ethane and propane showed to be better solvents than supercritical CO₂ leading to a faster extraction with a higher recovery of the carotenoid.

Mechanical and biological behavior of ultrafine-grained Ti alloy aneurysm clip processed using high-pressure torsion.

PubMed

Um, Ho Yong; Park, Byung Ho; Ahn, Dong-Hyun; Abd El Aal, Mohamed Ibrahim; Park, Jaechan; Kim, Hyoung Seop

2017-04-01

Severe plastic deformation (SPD) has recently been advanced as the main process for fabricating bulk ultrafine grained or nanocrystalline metallic materials, which present much higher strength and better bio-compatibility than coarse-grained counterparts. Medical devices, such as aneurysm clips and dental implants, require high mechanical and biological performance (e.g., stiffness, yield strength, fatigue resistance, and bio-compatibility). These requirements match well the characteristics of SPD-processed materials. Typical aneurysm clips are made of a commercial Ti-6Al-4V alloy, which has higher yield strength than Ti. In this work, Ti and Ti-6Al-4V workpieces were processed by high-pressure torsion (HPT) to enhance their mechanical properties. Tensile tests and hardness tests were performed to evaluate their mechanical properties, and their microstructure was investigated. The hardness and yield stress of the HPT-processed Ti are comparable to those of the initial Ti-6Al-4V due to significantly refined microstructure. Finite element analyses for evaluating the opening performance of a specific geometry of the YASARGIL aneurysm clip were carried out using mechanical properties of the initial and HPT-processed Ti and Ti-6Al-4V. These results indicate that SPD-processed Ti could be a good candidate to substitute for Ti-6Al-4V in aneurysm clips. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of supercritical vapor explosions using thermal detonation wave theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shamoun, B.I.; Corradini, M.L.

The interaction of certain materials such as Al{sub 2}O{sub 3} with water results in vapor explosions with very high (supercritical) pressures and propagation velocities. A quasi-steady state analysis of supercritical detonation in one-dimensional multiphase flow was applied to analyze experimental data of the KROTOS (26-30) set of experiments conducted at the Joint Research Center at Ispra, Italy. In this work we have applied a new method of solution which allows for partial fragmentation of the fuel in the shock adiabatic thermodynamic model. This method uses known experiment values of the shock pressure and propagation velocity to estimate the initial mixingmore » conditions of the experiment. The fuel and coolant were both considered compressible in this analysis. In KROTOS 26, 28, 29, and 30 the measured values of the shock pressure by the experiment were found to be higher than 25, 50, 100, and 100 Mpa respectively. Using the above data for the wave velocity and our best estimate for the values of the pressure, the predicted minimum values of the fragmented mass of the fuel were found to be 0.026. 0.04, 0.057, and 0.068 kg respectively. The predicted values of the work output corresponding to the above fragmented masses of the fuel were found to be 40, 84, 126, and 150 kJ respectively, with predicted initial void fractions of 112%, 12.5%, 8%, and 6% respectively.« less

Circulatory Responses to Asphyxia Differ if the Asphyxia Occurs In Utero or Ex Utero in Near-Term Lambs

PubMed Central

Sobotka, Kristina S.; Morley, Colin; Ong, Tracey; Polglase, Graeme R.; Aridas, James D. S.; Miller, Suzanne L.; Schmölzer, Georg M.; Klingenberg, Claus; Moss, Timothy J. M.; Jenkin, Graham; Hooper, Stuart B.

2014-01-01

Background A cornerstone of neonatal resuscitation teaching suggests that a rapid vagal-mediated bradycardia is one of the first signs of perinatal compromise. As this understanding is based primarily on fetal studies, we investigated whether the heart rate and blood pressure response to total asphyxia is influenced by whether the animal is in utero or ex utero. Methods Fetal sheep were instrumented at ∼139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to ∼20 mmHg. Lambs were either completely submerged in amniotic fluid (in utero; n = 8) throughout the asphyxia or were delivered and then remained ex utero (ex utero; n = 8) throughout the asphyxia. Heart rate and arterial blood pressure were continuously recorded. Results Heart rate was higher in ex utero lambs than in utero lambs. Heart rates in in utero lambs rapidly decreased, while heart rates in ex utero lambs initially increased following cord occlusion (for ∼1.5 min) before they started to decrease. Mean arterial pressure initially increased then decreased in both groups. Conclusions Heart rate response to asphyxia was markedly different depending upon whether the lamb was in utero or ex utero. This indicates that the cardiovascular responses to perinatal asphyxia are significantly influenced by the newborn's local environment. As such, based solely on heart rate, the stage and severity of a perinatal asphyxic event may not be as accurate as previously assumed. PMID:25393411

Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs.

PubMed

Sobotka, Kristina S; Morley, Colin; Ong, Tracey; Polglase, Graeme R; Aridas, James D S; Miller, Suzanne L; Schmölzer, Georg M; Klingenberg, Claus; Moss, Timothy J M; Jenkin, Graham; Hooper, Stuart B

2014-01-01

A cornerstone of neonatal resuscitation teaching suggests that a rapid vagal-mediated bradycardia is one of the first signs of perinatal compromise. As this understanding is based primarily on fetal studies, we investigated whether the heart rate and blood pressure response to total asphyxia is influenced by whether the animal is in utero or ex utero. Fetal sheep were instrumented at ∼ 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to ∼ 20 mmHg. Lambs were either completely submerged in amniotic fluid (in utero; n = 8) throughout the asphyxia or were delivered and then remained ex utero (ex utero; n = 8) throughout the asphyxia. Heart rate and arterial blood pressure were continuously recorded. Heart rate was higher in ex utero lambs than in utero lambs. Heart rates in in utero lambs rapidly decreased, while heart rates in ex utero lambs initially increased following cord occlusion (for ∼ 1.5 min) before they started to decrease. Mean arterial pressure initially increased then decreased in both groups. Heart rate response to asphyxia was markedly different depending upon whether the lamb was in utero or ex utero. This indicates that the cardiovascular responses to perinatal asphyxia are significantly influenced by the newborn's local environment. As such, based solely on heart rate, the stage and severity of a perinatal asphyxic event may not be as accurate as previously assumed.

Optimal layout design of obstacles for panic evacuation using differential evolution

NASA Astrophysics Data System (ADS)

Zhao, Yongxiang; Li, Meifang; Lu, Xin; Tian, Lijun; Yu, Zhiyong; Huang, Kai; Wang, Yana; Li, Ting

2017-01-01

To improve the pedestrian outflow in panic situations by suitably placing an obstacle in front of the exit, it is vital to understand the physical mechanism behind the evacuation efficiency enhancement. In this paper, a robust differential evolution is firstly employed to optimize the geometrical parameters of different shaped obstacles in order to achieve an optimal evacuation efficiency. Moreover, it is found that all the geometrical parameters of obstacles could markedly influence the evacuation efficiency of pedestrians, and the best way for achieving an optimal pedestrian outflow is to slightly shift the obstacle from the center of the exit which is consistent with findings of extant literature. Most importantly, by analyzing the profiles of density, velocity and specific flow, as well as the spatial distribution of crowd pressure, we have proven that placing an obstacle in panic situations does not reduce or absorb the pressure in the region of exit, on the contrary, promotes the pressure to a much higher level, hence the physical mechanism behind the evacuation efficiency enhancement is not a pressure decrease in the region of exit, but a significant reduction of high density region by effective separation in space which finally causes the increasing of escape speed and evacuation outflow. Finally, it is clearly demonstrated that the panel-like obstacle is considerably more robust and stable than the pillar-like obstacle to guarantee the enhancement of evacuation efficiency under different initial pedestrian distributions, different initial crowd densities as well as different desired velocities.

Improving Weather Research and Forecasting Model Initial Conditions via Surface Pressure Analysis

DTIC Science & Technology

2015-09-01

Obsgrid) that creates input data for the Advanced Research version of the Weather Research and Forecasting model ( WRF -ARW) is modified to perform a...surface pressure objective analysis to allow surface analyses of other fields to be more fully utilized in the WRF -ARW initial conditions. Nested 27-, 9...of surface pressure unnecessarily limits the application of other surface analyses into the WRF initial conditions and contributes to the creation of

Aldosterone, cognitive function, and cerebral hemodynamics in hypertension and antihypertensive therapy.

PubMed

Hajjar, Ihab; Hart, Meaghan; Mack, Wendy; Lipsitz, Lewis A

2015-03-01

Animal studies suggest that the renin-angiotensin-aldosterone system is involved in neurocognitive function and the response to antihypertensive therapy. We investigated the impact of circulating aldosterone and renin activity on cognition and cerebral hemodynamics at baseline and after antihypertensive therapy for 1 year. Participants were older adults (n = 47; mean age = 71 years) enrolled in a clinical trial. Routine antihypertensive medications were replaced with the study regimen to achieve a blood pressure <140/90 mm Hg. Executive function, memory, cerebral hemodynamics (blood flow velocity), CO2 vasoreactivity (measured using transcranial Doppler ultrasonography), plasma renin activity, and aldosterone were measured at baseline and at 6 and 12 months after the initiation of treatment. At baseline, higher levels of circulating aldosterone were associated with lower blood flow velocity (β = -0.02; P = 0.03), lower CO2 vasoreactivity (β = -0.11; P = 0.007), and decreased autoregulation abilities (β = -0.09; P = 0.01). Those with higher levels of aldosterone at baseline demonstrated the greatest improvement in executive function (P = 0.014 for the aldosterone effect) and in CO2 vasoreactivity (P = 0.026 for the aldosterone effect) after 12 months of lowering blood pressure (<140/90 mm Hg). Plasma renin activity was not associated with any of the measures. Higher levels of aldosterone may be associated with decreased cerebrovascular function in hypertension. Those with higher aldosterone levels may benefit the most from lowering blood pressure. The role of aldosterone in brain health warrants further investigation in a larger trial. © American Journal of Hypertension, Ltd 2014. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Aldosterone, Cognitive Function, and Cerebral Hemodynamics in Hypertension and Antihypertensive Therapy

PubMed Central

Hart, Meaghan; Mack, Wendy; Lipsitz, Lewis A.

2015-01-01

BACKGROUND Animal studies suggest that the renin–angiotensin–aldosterone system is involved in neurocognitive function and the response to antihypertensive therapy. We investigated the impact of circulating aldosterone and renin activity on cognition and cerebral hemodynamics at baseline and after antihypertensive therapy for 1 year. METHODS Participants were older adults (n = 47; mean age = 71 years) enrolled in a clinical trial. Routine antihypertensive medications were replaced with the study regimen to achieve a blood pressure <140/90mm Hg. Executive function, memory, cerebral hemodynamics (blood flow velocity), CO2 vasoreactivity (measured using transcranial Doppler ultrasonography), plasma renin activity, and aldosterone were measured at baseline and at 6 and 12 months after the initiation of treatment. RESULTS At baseline, higher levels of circulating aldosterone were associated with lower blood flow velocity (β = −0.02; P = 0.03), lower CO2 vasoreactivity (β = −0.11; P = 0.007), and decreased autoregulation abilities (β = −0.09; P = 0.01). Those with higher levels of aldosterone at baseline demonstrated the greatest improvement in executive function (P = 0.014 for the aldosterone effect) and in CO2 vasoreactivity (P = 0.026 for the aldosterone effect) after 12 months of lowering blood pressure (<140/90mm Hg). Plasma renin activity was not associated with any of the measures. CONCLUSIONS Higher levels of aldosterone may be associated with decreased cerebrovascular function in hypertension. Those with higher aldosterone levels may benefit the most from lowering blood pressure. The role of aldosterone in brain health warrants further investigation in a larger trial. PMID:25213687

Effects of pressure rise on cw laser ablation of tissue

NASA Astrophysics Data System (ADS)

LeCarpentier, Gerald L.; Motamedi, Massoud; Welch, Ashley J.

1991-06-01

The objectives of this research were to identify mechanisms responsible for the initiation of continuous wave (cw) laser ablation of tissue and investigate the role of pressure in the ablation process. Porcine aorta samples were irradiated in a chamber pressurized from 1 X 10-4 to 12 atmospheres absolute pressure. Acrylic and Zn-Se windows in the experimental pressure chamber allowed video and infrared cameras to simultaneously record mechanical and thermal events associated with cw argon laser ablation of these samples. Video and thermal images of tissue slabs documented the explosive nature of cw laser ablation of soft biological media and revealed similar ablation threshold temperatures and ablation onset times under different environmental pressures; however, more violent initiation explosions with decreasing environmental pressures were observed. These results suggest that ablation initiates with thermal alterations in the mechanical strength of the tissue and proceeds with an explosion induced by the presence superheated liquid within the tissue.

Implications of Dynamic Pressure Transducer Mounting Variations on Measurements in Pyrotechnic Test Apparatus

NASA Technical Reports Server (NTRS)

Dibbern, Andreas; Crisafulli, Jeffrey; Hagopia, Michael; McDougle, Stephen H.; Saulsberry, Regor L.

2009-01-01

Accurate dynamic pressure measurements are often difficult to make within small pyrotechnic devices, and transducer mounting difficulties can cause data anomalies that lead to erroneous conclusions. Delayed initial pressure response followed by data ringing has been observed when using miniaturized pressure transducer mounting adapters required to interface transducers to small test chambers. This delayed pressure response and ringing, combined with a high data acquisition rate, has complicated data analysis. This paper compares the output signal characteristics from different pressure transducer mounting options, where the passage distance from the transducer face to the pyrotechnic chamber is varied in length and diameter. By analyzing the data and understating the associated system dynamics, a more realistic understanding of the actual dynamic pressure variations is achieved. Three pressure transducer mounting configurations (elongated, standard, and face/flush mount) were simultaneously tested using NASA standard initiators in closed volume pressure bombs. This paper also presents results of these pressure transducer mounting configurations as a result of a larger NASA Engineering and Safety Center pyrovalve test project. Results from these tests indicate the improved performance of using face/flush mounted pressure transducers in this application. This type of mounting improved initial pressure measurement response time by approximately 19 s over standard adapter mounting, eliminating most of the lag time; provided a near step-function type initial pressure increase; and greatly reduced data ringing in high data acquisition rate systems. The paper goes on to discuss other issues associated with the firing and instrumentation that are important for the tester to understand.

Dietary and urinary metabonomic factors possibly accounting for higher blood pressure of black compared with white Americans: results of International Collaborative Study on macro-/micronutrients and blood pressure.

PubMed

Stamler, Jeremiah; Brown, Ian J; Yap, Ivan K S; Chan, Queenie; Wijeyesekera, Anisha; Garcia-Perez, Isabel; Chadeau-Hyam, Marc; Ebbels, Timothy M D; De Iorio, Maria; Posma, Joram; Daviglus, Martha L; Carnethon, Mercedes; Holmes, Elaine; Nicholson, Jeremy K; Elliott, Paul

2013-12-01

Black compared with non-Hispanic white Americans have higher systolic and diastolic blood pressure and rates of prehypertension/hypertension. Reasons for these adverse findings remain obscure. Analyses here focused on relations of foods/nutrients/urinary metabolites and higher black blood pressure for 369 black compared with 1190 non-Hispanic white Americans aged 40 to 59 years from 8 population samples. Multiple linear regression, standardized data from four 24-hour dietary recalls per person, two 24-hour urine collections, and 8 blood pressure measurements were used to quantitate the role of foods, nutrients, and metabolites in higher black blood pressure. Compared with non-Hispanic white Americans, blacks' average systolic/diastolic pressure was higher by 4.7/3.4 mm Hg (men) and 9.0/4.8 mm Hg (women). Control for higher body mass index of black women reduced excess black systolic/diastolic pressure to 6.8/3.8 mm Hg. Lesser intake of vegetables, fruits, grains, vegetable protein, glutamic acid, starch, fiber, minerals, and potassium, and higher intake of processed meats, pork, eggs, and sugar-sweetened beverages, along with higher cholesterol and higher Na/K ratio, related to in higher black blood pressure. Control for 11 nutrient and 10 non-nutrient correlates reduced higher black systolic/diastolic pressure to 2.3/2.3 mm Hg (52% and 33% reduction in men) and to 5.3/2.8 mm Hg (21% and 27% reduction in women). Control for foods/urinary metabolites had little further influence on higher black blood pressure. Less favorable multiple nutrient intake by blacks than non-Hispanic white Americans accounted, at least in part, for higher black blood pressure. Improved dietary patterns can contribute to prevention/control of more adverse black blood pressure levels.

Impact of Magnetic Field on Pressures of Programmable Cerebrospinal Fluid Shunts: An Experimental Study.

PubMed

Altun, Idiris; Yuksel, Kasim Zafer; Mert, Tufan

2017-01-01

To investigate whether programmable cerebrospinal fluid (CSF) shunts are influenced by exposure to the magnetic field and to compare the effects of magnetic field in 4 different brands of programmable CSF shunts. This experimental study was performed in the laboratory using a novel design of magnetic field. Four types of programmable CSF shunts (Miethke®, Medtronic®, Sophysa® and Codman®Hakim®) were exposed to the magnetic field generated by an apparatus consisting of Helmholtz coil for 5 minutes. In every CSF shunt, initial pressures were adjusted to 110 mm H2O and pressures after exposure to magnetic field were noted. These measurements were implemented at frequencies of 5 Hz, 20 Hz, 30 Hz, 40 Hz, 60 Hz and 80 Hz. In each type, three shunts were utilized and evaluations were made twice for every shunt. At 5, 30, 40 and 60 Hz, Groups 1, 2 and 3 had significantly higher average pressures than Group 4. At 20 and 80 Hz, Groups 1 and 2 had notably different pressure values than Groups 3 and 4. Group 3 displayed the highest pressure, while Group 4 demonstrated the lowest pressure. Exposure to magnetic fields may affect the pressures of programmable CSF shunts. However, further controlled, clinical trials are warranted to elucidate the in-vivo effects of magnetic field exposure.

Effects of control parameters of three-point initiation on the formation of an explosively formed projectile with fins

NASA Astrophysics Data System (ADS)

Li, R.; Li, W. B.; Wang, X. M.; Li, W. B.

2018-03-01

The effects of the initiation diameter and synchronicity error on the formation of fins and stable-flight velocity of an explosively formed projectile (EFP) with three-point initiation are investigated. The pressure and area of the Mach wave acting on the metal liner at different initiation diameters are calculated employing the Whitham method. LS-DYNA software is used to investigate the asymmetric collision of detonation waves resulting from three-point initiation synchronicity error, the distortion characteristics of the liner resulting from the composite detonation waves, and the performance parameters of the EFP with fins. Results indicate that deviations of the Y-shaped high-pressure zone and central ultrahigh-pressure zone from the liner center can be attributed to the error of three-point initiation, which leads to the irregular formation of EFP fins. It is noted that the area of the Mach wave decreases, but the pressure of the Mach wave and the final speed and length-to-diameter ( L/ D) ratio of the EFP increase, benefiting the formation of the EFP fins, as the initiation diameter increases.

Xanthan production on polyurethane foam and its enhancement by air pressure pulsation.

PubMed

Zhang, Zhi-guo; Chen, Hong-zhang

2010-12-01

In this study, we evaluated the feasibility of solid-state fermentation (SSF) on polyurethane foam (PUF) for xanthan production. The effects of air pressure pulsation (APP) on biomass accumulation and final xanthan concentration were also studied. Under suitable conditions (15% inoculum, 0.5-cm (side length) PUF cubes, 15 mL medium per gram cubes and 4.5 cm bed depth), the broth was dispersed on the PUF as a film. When the initial glucose concentration in the media was low (20 and 40 g L⁻¹), there was no significant difference between the final xanthan concentration in static SSF and submerged fermentation (SMF). When high initial glucose concentrations (60 and 80 g L⁻¹) were used, the final gum concentrations in SSF were much higher than those in SMF. When the APP technique was applied in xanthan production with a medium containing a high glucose concentration (80 g L⁻¹), the oxygen consumption rate of Xanthomonas campestris was significantly enhanced at the later stages of fermentation, and both the biomass and xanthan concentration were improved. The results indicated that SSF on PUF is suitable for xanthan preparation, especially when the initial glucose concentration ranged from 60 to 80 g L⁻¹. Those results also demonstrated that APP technology can be used to enhance xanthan yields.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parkin, E. R.; Bicknell, G. V., E-mail: parkin@mso.anu.edu.au

Global three-dimensional magnetohydrodynamic (MHD) simulations of turbulent accretion disks are presented which start from fully equilibrium initial conditions in which the magnetic forces are accounted for and the induction equation is satisfied. The local linear theory of the magnetorotational instability (MRI) is used as a predictor of the growth of magnetic field perturbations in the global simulations. The linear growth estimates and global simulations diverge when nonlinear motions-perhaps triggered by the onset of turbulence-upset the velocity perturbations used to excite the MRI. The saturated state is found to be independent of the initially excited MRI mode, showing that once themore » disk has expelled the initially net flux field and settled into quasi-periodic oscillations in the toroidal magnetic flux, the dynamo cycle regulates the global saturation stress level. Furthermore, time-averaged measures of converged turbulence, such as the ratio of magnetic energies, are found to be in agreement with previous works. In particular, the globally averaged stress normalized to the gas pressure <{alpha}{sub P}>bar = 0.034, with notably higher values achieved for simulations with higher azimuthal resolution. Supplementary tests are performed using different numerical algorithms and resolutions. Convergence with resolution during the initial linear MRI growth phase is found for 23-35 cells per scale height (in the vertical direction).« less

An experimental study of evaporation waves in a superheated liquid

NASA Astrophysics Data System (ADS)

Hill, Larry G.

1990-01-01

Evaporation waves in superheated liquids are studied using a rapid-depressurization facility consisting of a vertical glass test cell situated beneath a large, low-pressure reservoir. The objective of this study is to learn more about the physical mechanisms of explosive boiling (of which an evaporation wave is a specific example), as well as properties of the flow it produces.The test cell is initially sealed from the reservoir by a foil diaphragm, and is partially filled with a volatile liquid (Refrigerant 12 or 114). An experiment is initiated by rupturing the diaphragm via a pneumatically driven cutter. The instrumentation consists of fast-response pressure measurements, high-speed motion pictures, and spark-illuminated still photographs. The liquid temperature is typically 20°C; the liquid superheat is controlled by setting the reservoir pressure to values between vacuum and 1 atm. The pressures subsequent to depressurization are very much less than the critical pressure, and the initial temperatures are sufficiently low that, although the test liquid is highly superheated, the superheat limit is not approached. Evaporation waves in which bubble nucleation within the liquid column is suppressed entirely are considered almost exclusively.When the diaphragm is ruptured, the liquid pressure drops to virtually the reservoir value within a few milliseconds. Provided that the liquid superheat so obtained is sufficiently high, the free surface then erupts in a process known as explosive boiling, which is characterized by violent, fine-scale fragmentation of the superheated liquid and extremely rapid evaporation. The explosive boiling process proceeds as a "wavefront" into the liquid column, producing a highspeed, two-phase flow that travels upward into the low-pressure reservoir, emptying the test cell in a few hundred milliseconds. The speed of the wavefront varies between 0.2 and 0.6 m/s, depending on run conditions; the corresponding two-phase flow varies between about 5 and 35 m/s.In the highest superheat case for the more volatile liquid (Refrigerant 12), explosive boiling usually initiates by the rapid formation of nucleation sites at random spots on the liquid free surface and at the glass/free-surface contact line. Boiling spreads to the remaining surface within 160 [...]. In the highest superheat case for the less volatile liquid (Refrigerant 114), nucleation begins only at the glass/free-surface contact line. Boiling then spreads radially inward toward the center. In the lower superheated cases for both liquids, nucleation begins at one or more sites on the glass/free-surface contact line, and propagates across the free surface.At the higher superheats, explosive boiling initiates within a few milliseconds from diaphragm burst, the same time scale as that of liquid depressurization. No distinction is made between the onset of nucleation and that of explosive boiling. However, if the reservoir pressure is raised above a certain approximate value, the onset of explosive boiling is delayed. During the delay period, relatively slow bubbling (initiated at one or more nucleation sites at the glass/free-surface contact line) occurs, and a cluster of bubbles forms in the vicinity of the initial site. The bubble cluster then "explodes," marking the transition to explosive boiling. The delay period increases significantly as the reservoir pressure is raised slightly further. Reservoir pressures corresponding to a delay period of order 100 ms define an approximate self-start threshold pressure, above which the transition to explosive boiling does not occur. Within about 10 ms of initiation, the wave reaches a quasi-steady condition in which the average wave speed, two-phase flow speed, and base and exit pressures are constant. However, the instantaneous propagation rate and the mechanisms that generate the mean flow are observed to be highly nonsteady. The wavefront appears to propagate by heterogeneous bubble nucleation at its leading edge, and any given region of the wavefront tends to propagate in surges associated with new nucleation and/or very fine-scale surface perturbations. Measurements of the instantaneous position of the upstream tip of the wavefront indicate that local velocity fluctuations are the same order as the mean velocity. The leading-edge bubble lifetimes and diameters are statistically distributed; mean values are of order 1 ms and 1 mm, respectively. The leading-edge bubbles are fragmented in violent "bursts" of aerosol. Bursts have a tendency to sweep over the leading-edge bubble layer in a wavelike manner: They are "large-scale structures" associated with the fragmentation of many bubbles.Fragmentation, rapid evaporation, flow acceleration, and pressure drop occur primarily within about 1 cm of the leading edge. Downstream of this region, the average speed and appearance of the flow are virtually constant. This developed flow is a highly nonuniform, two-phase spray containing streaklike structures. Its liquid phase is composed of drops (with a maximum diameter of about 100 [...]), as well as clusters and chains of bubbles (with a diameter of a few hundred microns). A thin liquid layer begins climbing the wall upon wave initiation. Its speed is a few m/s-significantly slower than that of the two-phase flow through the center. Exit pressure measurements indicate that the flow chokes for sufficiently low reservoir pressure; at higher reservoir pressures the flow is unchoked.The self-start threshold is not a propagation threshold, as waves are observed to propagate at somewhat lower superheats if started artificially. This is accomplished in Refrigerant 114 by "jump-starting" the wave, using the more volatile Refrigerant 12. For sufficiently high reservoir pressures, an "absolute" threshold is reached at which the quasi-steady rapid evaporation processes break down.Possible mechanisms for explosive boiling are discussed in light of the present results. While neither of the two previous schools of thought (interfacial instability hypotheses and the secondary nucleation hypothesis) are alone adequate to explain the observed behavior, there is evidence that both may play a role. It is here proposed that the bursting phenomenon and bubble nucleation at the wavefront leading edge are mutually interactive processes-bursting occurring as the violent breakup of interstitial bubble liquid, and nucleation (and fine-scale perturbations) being caused by burst-generated aerosol striking the leading-edge surface. It is not understood what role interfacial instability may play in the bursting process.An evaporation wave is analogous to a premixed flame in that both are classified as "weak deflagration" waves in gasdynamic theory. It is shown that using several approximations that are valid for the type of evaporation waves studied, the conservation equations (jump conditions) can be reduced to a single, simple expression in terms of readily measured and inferred properties.

Shock-adiabatic to quasi-isentropic compression of warm dense helium up to 150 GPa

NASA Astrophysics Data System (ADS)

Zheng, J.; Chen, Q. F.; Gu, Y. J.; Li, J. T.; Li, Z. G.; Li, C. J.; Chen, Z. Y.

2017-06-01

Multiple reverberation compression can achieve higher pressure, higher temperature, but lower entropy. It is available to provide an important validation for the elaborate and wider planetary models and simulate the inertial confinement fusion capsule implosion process. In the work, we have developed the thermodynamic and optical properties of helium from shock-adiabatic to quasi-isentropic compression by means of a multiple reverberation technique. By this technique, the initial dense gaseous helium was compressed to high pressure and high temperature and entered the warm dense matter (WDM) region. The experimental equation of state (EOS) of WDM helium in the pressure-density-temperature (P-ρ -T) range of 1 -150 GPa , 0.1 -1.1 g c m-3 , and 4600-24 000 K were measured. The optical radiations emanating from the WDM helium were recorded, and the particle velocity profiles detecting from the sample/window interface were obtained successfully up to 10 times compression. The optical radiation results imply that dense He has become rather opaque after the 2nd compression with a density of about 0.3 g c m-3 and a temperature of about 1 eV. The opaque states of helium under multiple compression were analyzed by the particle velocity measurements. The multiple compression technique could efficiently enhanced the density and the compressibility, and our multiple compression ratios (ηi=ρi/ρ0,i =1 -10 ) of helium are greatly improved from 3.5 to 43 based on initial precompressed density (ρ0) . For the relative compression ratio (ηi'=ρi/ρi -1) , it increases with pressure in the lower density regime and reversely decreases in the higher density regime, and a turning point occurs at the 3rd and 4th compression states under the different loading conditions. This nonmonotonic evolution of the compression is controlled by two factors, where the excitation of internal degrees of freedom results in the increasing compressibility and the repulsive interactions between the particles results in the decreasing compressibility at the onset of electron excitation and ionization. In the P-ρ -T contour with the experiments and the calculations, our multiple compression states from insulating to semiconducting fluid (from transparent to opaque fluid) are illustrated. Our results give an elaborate validation of EOS models and have applications for planetary and stellar opaque atmospheres.

Microparticle formation by platelets exposed to high gas pressures - An oxidative stress response.

PubMed

Bhullar, Jasjeet; Bhopale, Veena M; Yang, Ming; Sethuraman, Kinjal; Thom, Stephen R

2016-12-01

This investigation explored the mechanism for microparticles (MPs) production by human and murine platelets exposed to high pressures of inert gases. Results demonstrate that MPs production occurs via an oxidative stress response in a dose-dependent manner and follows the potency series N 2 >Ar>He. Gases with higher van der Waals volumes or polarizability such as SF 6 and N 2 O, or hydrostatic pressure, do not cause MPs production. Singlet O 2 is generated by N 2 , Ar and He, which is linked to NADPH oxidase (NOX) activity. Progression of oxidative stress involves activation of nitric oxide synthase (NOS) leading to S-nitrosylation of cytosolic actin. Exposure to gases enhances actin filament turnover and associations between short actin filaments, NOS, vasodilator-stimulated phosphoprotein (VASP), focal adhesion kinase (FAK) and Rac1. Inhibition of NOS or NOX by chemical inhibitors or using platelets from mice lacking NOS2 or the gp91phox component of NOX diminish generation of reactive species, enhanced actin polymerization and MP generation by high pressure gases. We conclude that by initiating a sequence of progressive oxidative stress responses high pressure gases cause platelets to generate MPs. Copyright © 2016 Elsevier Inc. All rights reserved.

Pressure-Induced Irreversible Phase Transition in the Energetic Material Urea Nitrate

NASA Astrophysics Data System (ADS)

Li, Shourui; Zou, Bo

2013-06-01

The behavior of energetic material Urea Nitrate ((NH2)2 COH+ . NO3-,UN) has been investigated up to the pressure of ~26 GPa. UN exhibits the typical supramolecular structure with uronium cation and nitrate anion held together by multiple hydrogen bonds in the layer. Both Raman and XRD data provide obvious evidence for the distorted phase transition in the pressure range ~9-15 GPa. Further analysis indicates phase II has Pc symmetry. The mechanism for the phase transition involves collapse of the initial 2D supramolecular structure to 3D hydrogen-bonded networks in phase Pc. Importantly, the transition is irreversible and leads to a large reduction in volume on release of pressure. The density in phase Pc has been increased by ~11.8% compared to the phase P21/ c under ambient conditions and therefore phase Pc is expected to have much higher detonation power. This study opens new opportunities for preparing energetic materials with high density combining supramolecular chemistry with high-pressure techniques. Corresponding author. E-mail: zoubo@jlu.edu.cn This work is supported by National Science Foundation of China (NSFC) (Nos. 91227202, and 21073071).

Methods of increasing thermal efficiency of steam and gas turbine plants

NASA Astrophysics Data System (ADS)

Vasserman, A. A.; Shutenko, M. A.

2017-11-01

Three new methods of increasing efficiency of turbine power plants are described. Increasing average temperature of heat supply in steam turbine plant by mixing steam after overheaters with products of combustion of natural gas in the oxygen. Development of this idea consists in maintaining steam temperature on the major part of expansion in the turbine at level, close to initial temperature. Increasing efficiency of gas turbine plant by way of regenerative heating of the air by gas after its expansion in high pressure turbine and before expansion in the low pressure turbine. Due to this temperature of air, entering combustion chamber, is increased and average temperature of heat supply is consequently increased. At the same time average temperature of heat removal is decreased. Increasing efficiency of combined cycle power plant by avoiding of heat transfer from gas to wet steam and transferring heat from gas to water and superheated steam only. Steam will be generated by multi stage throttling of the water from supercritical pressure and temperature close to critical, to the pressure slightly higher than condensation pressure. Throttling of the water and separation of the wet steam on saturated water and steam does not require complicated technical devices.

The effect of initial pressure on growth of FeNPs in amorphous carbon films

NASA Astrophysics Data System (ADS)

Mashayekhi, Fatemeh; Shafiekhani, Azizollah; Sebt, S. Ali; Darabi, Elham

2018-04-01

Iron nanoparticles in amorphous hydrogenated carbon films (FeNPs@a-C:H) were prepared with RF-sputtering and RFPECVD methods by acetylene gas and Fe target. In this paper, deposition and sputtering process were carried out under influence of different initial pressure gas. The morphology and roughness of surface of samples were studied by AFM technique and also TEM images show the exact size of FeNPs and encapsulated FeNPs@a-C:H. The localized surface plasmon resonance peak (LSPR) of FeNPs was studied using UV-vis absorption spectrum. The results show that the intensity and position of LSPR peak are increased by increasing initial pressure. Also, direct energy gap of samples obtained by Tauc law is decreased with respect to increasing initial pressure.

Protective Effects of the Launch/Entry Suit (LES) and the Liquid Cooling Garment(LCG) During Re-entry and Landing After Spaceflight

NASA Technical Reports Server (NTRS)

Perez, Sondra A.; Charles, John B.; Fortner, G. William; Hurst, Victor, IV; Meck, Janice V.

2002-01-01

Heart rate and arterial pressure were measured during shuttle re-entry, landing and initial standing in crewmembers with and without inflated anti-g suits and with and without liquid cooling garments (LCG). Preflight, three measurements were obtained seated, then standing. Prior to and during re-entry, arterial pressure and heart rate were measured every five minutes until wheels stop (WS). Then crewmembers initiated three seated and three standing measurements. In subjects without inflated anti-g suits, SBP and DBP were significantly lower during preflight standing (P = 0.006; P = 0.001 respectively) and at touchdown (TD) (P = 0.001; P = 0.003 respectively); standing SBP was significantly lower after WS. on-LeG users developed significantly higher heart rates during re-entry (P = 0.029, maxG; P = 0.05, TD; P = 0.02, post-WS seated; P = 0.01, post-WS standing) than LCG users. Our data suggest that the anti-g suit is effective, but the combined anti-g suit with LCG is more effective.

Initial Observations on the Burning of an Ethanol Droplet in Microgravity

NASA Technical Reports Server (NTRS)

Kazakov, Andrei; Urban, Bradley; Conley, Jordan; Dryer, Frederick L.; Ferkul, Paul (Technical Monitor)

1999-01-01

Combustion of liquid ethanol represents an important system both from fundamental and practical points of view, Ethanol is currently being used as an additive to gasoline in order to reduce carbon monoxide and particulate emissions as well as to improve the fuel octane rating. A detailed physical understanding of liquid ethanol combustion is therefore necessary to achieve an optimal performance of such fuel blends in practical conditions. Ethanol is also a relatively simple model compound suitable for investigation of important combustion characteristics typical of more complex fuels. In particular, ethanol has been proposed for studies of sooting behavior during droplet burning. The sooting nature of ethanol has pressure sensitivities similar to that of n-heptane, but shifted to a higher range of pressures (1-3 atm). Additionally, liquid ethanol is miscible with water produced during its combustion forming mixtures with azeotropic behavior, a phenomenon important for understanding multi-component, liquid fuel combustion. In this work, we present initial results obtained in a series of recent space-based experiments and develop a detailed model describing the burning of ethanol droplet in microgravity.

Critical oxide cluster size on Si(111)

NASA Astrophysics Data System (ADS)

Shklyaev, A. A.; Aono, M.; Suzuki, T.

1999-03-01

The initial stage of oxide growth and subsequent oxide decomposition on Si(111)-7×7 at temperatures between 350 and 720°C are studied with the optical second harmonic generation for O 2 pressures ( Pox) between 5×10 -9 and 4×10 -6 Torr. The obtained pressure dependencies of the initial oxide growth rate ( Rgr) and the subsequent oxide decomposition rate are associated with the cluster-forming nature of the oxidation process. For the model of oxide cluster nucleation and growth, a scaling relationship is derived among the critical oxide cluster size, i, and the experimentally measurable values of Rgr and Pox. The critical oxide cluster size, i, thus obtained from the kinetic data increases with temperature. This correlates with an increase of desorption channels and their rates in that the competition between growth and decomposition requires more stable oxide clusters, i.e. clusters with a larger critical size, for oxide to grow at higher temperatures. The increase of i with decreasing Pox is related with a decrease of Rgr: a decreased Rgr requires critical clusters with a longer lifetime, i.e. clusters with a larger size.

Nucleation and dynamic rupture on weakly stressed faults sustained by thermal pressurization

NASA Astrophysics Data System (ADS)

Schmitt, Stuart V.; Segall, Paul; Dunham, Eric M.

2015-11-01

Earthquake nucleation requires that the shear stress τ locally reaches a fault's static strength, fσeff, the product of the friction coefficient and effective normal stress. Once rupture initiates, shear heating-induced thermal pressurization can sustain rupture at much lower τ/σeff ratios, a stress condition believed to be the case during most earthquakes. This requires that earthquakes nucleate at heterogeneities. We model nucleation and dynamic rupture on faults in a 2-D elastic medium with rate/state friction and thermal pressurization, subjected to globally low τ but with local stress heterogeneities that permit nucleation. We examine end-member cases of either high-τ or low-σeff heterogeneities. We find that thermal pressurization can sustain slip at τ/σeff values as low as 0.13, compared to static friction of ˜0.7. Background τ (and, to lesser extent, heterogeneity width) controls whether ruptures arrest or are sustained, with extremely low values resulting in arrest. For a small range of background τ, sustained slip is pulse-like. Cessation of slip in a pulse tail can result from either diffusive restrengthening of σeff or a wave-mediated stopping phase that follows the rupture tip. Slightly larger background τ leads to sustained crack-like rupture. Thermal pressurization is stronger at high-τ heterogeneities, resulting in a lower background τ threshold for sustained rupture and potentially larger arresting ruptures. High-stress events also initiate with higher moment rate, although this may be difficult to observe in nature. For arresting ruptures, stress drops and the dependence of fracture energy on mean slip are both consistent with values inferred for small earthquakes.

Muscular Subaortic Stenosis

PubMed Central

Wigle, E. Douglas; Auger, Pierre; Marquis, Yves

1966-01-01

Two types of intraventricular pressure differences within the left ventricle of man are described. The first is encountered in cases of muscular (or fibrous) subaortic stenosis, in which the outflow tract pressure distal to the stenosis (and proximal to the aortic valve) is low, whereas all pressures recorded in the left ventricle proximal to the stenosis, including that just inside the mitral valve (the initial inflow tract pressure) are high. The second type of intraventricular pressure difference may be recorded in patients without muscular subaortic stenosis when a heart catheter is advanced to the left ventricular wall in such a manner that it becomes imbedded or entrapped by cardiac muscle in systole. Such an entrapped catheter records a high intraventricular pressure that is believed to reflect intramyocardial tissue pressure, which normally exceeds intracavitary pressure. In such cases the initial inflow tract pressure is not high and is precisely equal to the outflow tract systolic pressure, i.e. both are recording intracavity pressure. This type of intramyocardial to intracavitary pressure difference may also be encountered in the left ventricle of dogs. The recent suggestion that intraventricular pressure differences in the left ventricle of cases of muscular subaortic stenosis are due to catheter entrapment by cardiac muscle is refuted by using the initial inflow tract pressure as the means of differentiation between the two types of intraventricular pressure differences outlined. PMID:5951625

40 CFR 146.88 - Injection well operating requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection zone(s) so as to ensure that the injection does not initiate new fractures or propagate existing fractures in the injection zone(s). In no case may injection pressure initiate fractures...

40 CFR 146.88 - Injection well operating requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection zone(s) so as to ensure that the injection does not initiate new fractures or propagate existing fractures in the injection zone(s). In no case may injection pressure initiate fractures...

40 CFR 146.88 - Injection well operating requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection zone(s) so as to ensure that the injection does not initiate new fractures or propagate existing fractures in the injection zone(s). In no case may injection pressure initiate fractures...

40 CFR 146.88 - Injection well operating requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection zone(s) so as to ensure that the injection does not initiate new fractures or propagate existing fractures in the injection zone(s). In no case may injection pressure initiate fractures...

Soviet research on the transport of intense relativistic electron beams through high-pressure air

NASA Astrophysics Data System (ADS)

Wells, Nikita

1987-05-01

Soviet development of intense relativistic electron beams (IREB) through background air at pressures from 1/100 Torr to atmospheric is analyzed as reflected by Soviet open literature of the last 15 years. Important Soviet findings include: (1) the formation of a plasma channel created by an IREB propagating through background air and the effect of beam parameters upon the plasma channel parameters (and vice versa); (2) determination of the background air pressure for the optimum transport of IREB in two ranges, an ion focused regime at 0.06 to 0.09 Torr and a low pressure window at 1 Torr; (3) observation of current enhancement, whereby the IREB-induced current in plasma is higher than the initial beam current; and (4) the effect of resistive hose instability on IREB propagation. This research is characterized by absence of high energy experimentation. A conclusion of the research is that, for optimum beam transport through air, it is imperative to ensure conditions that allow full neutralization of the IREB's self-fields along the entire path of the beam's transport.

Lagrangian technique to calculate window interface velocity from shock velocity measurements: Application for quartz windows

DOE PAGES

McCoy, Chad A.; Knudson, Marcus D.

2017-08-24

Measurement of the window interface velocity is a common technique for investigating the dynamic response materials at high strain rates. However, these measurements are limited in pressure to the range where the window remains transparent. The most common window material for this application is lithium fluoride, which under single shock compression becomes opaque at ~200 GPa. To date, no other window material has been identified for use at higher pressures. Here, we present a Lagrangian technique to calculate the interface velocity from a continuously measured shock velocity, with application to quartz. The quartz shock front becomes reflective upon melt, atmore » ~100 GPa, enabling the use of velocity interferometry to continuously measure the shock velocity. This technique overlaps with the range of pressures accessible with LiF windows and extends the region where wave profile measurements are possible to pressures in excess of 2000 GPa. Lastly, we show through simulated data that the technique accurately reproduces the interface velocity within 20% of the initial state, and that the Lagrangian technique represents a significant improvement over a simple linear approximation.« less

Microplasma discharge vacuum ultraviolet photoionization source for atmospheric pressure ionization mass spectrometry.

PubMed

Symonds, Joshua M; Gann, Reuben N; Fernández, Facundo M; Orlando, Thomas M

2014-09-01

In this paper, we demonstrate the first use of an atmospheric pressure microplasma-based vacuum ultraviolet (VUV) photoionization source in atmospheric pressure mass spectrometry applications. The device is a robust, easy-to-operate microhollow cathode discharge (MHCD) that enables generation of VUV photons from Ne and Ne/H(2) gas mixtures. Photons were detected by excitation of a microchannel plate detector and by analysis of diagnostic sample ions using a mass spectrometer. Reactive ions, charged particles, and metastables produced in the discharge were blocked from entering the ionization region by means of a lithium fluoride window, and photoionization was performed in a nitrogen-purged environment. By reducing the output pressure of the MHCD, we observed heightened production of higher-energy photons, making the photoionization source more effective. The initial performance of the MHCD VUV source has been evaluated by ionizing model analytes such as acetone, azulene, benzene, dimethylaniline, and glycine, which were introduced in solid or liquid phase. These molecules represent species with both high and low proton affinities, and ionization energies ranging from 7.12 to 9.7 eV.

Lagrangian technique to calculate window interface velocity from shock velocity measurements: Application for quartz windows

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCoy, Chad A.; Knudson, Marcus D.

Measurement of the window interface velocity is a common technique for investigating the dynamic response materials at high strain rates. However, these measurements are limited in pressure to the range where the window remains transparent. The most common window material for this application is lithium fluoride, which under single shock compression becomes opaque at ~200 GPa. To date, no other window material has been identified for use at higher pressures. Here, we present a Lagrangian technique to calculate the interface velocity from a continuously measured shock velocity, with application to quartz. The quartz shock front becomes reflective upon melt, atmore » ~100 GPa, enabling the use of velocity interferometry to continuously measure the shock velocity. This technique overlaps with the range of pressures accessible with LiF windows and extends the region where wave profile measurements are possible to pressures in excess of 2000 GPa. Lastly, we show through simulated data that the technique accurately reproduces the interface velocity within 20% of the initial state, and that the Lagrangian technique represents a significant improvement over a simple linear approximation.« less

Local Sensitivity of Predicted CO 2 Injectivity and Plume Extent to Model Inputs for the FutureGen 2.0 site

DOE PAGES

Zhang, Z. Fred; White, Signe K.; Bonneville, Alain; ...

2014-12-31

Numerical simulations have been used for estimating CO2 injectivity, CO2 plume extent, pressure distribution, and Area of Review (AoR), and for the design of CO2 injection operations and monitoring network for the FutureGen project. The simulation results are affected by uncertainties associated with numerous input parameters, the conceptual model, initial and boundary conditions, and factors related to injection operations. Furthermore, the uncertainties in the simulation results also vary in space and time. The key need is to identify those uncertainties that critically impact the simulation results and quantify their impacts. We introduce an approach to determine the local sensitivity coefficientmore » (LSC), defined as the response of the output in percent, to rank the importance of model inputs on outputs. The uncertainty of an input with higher sensitivity has larger impacts on the output. The LSC is scalable by the error of an input parameter. The composite sensitivity of an output to a subset of inputs can be calculated by summing the individual LSC values. We propose a local sensitivity coefficient method and applied it to the FutureGen 2.0 Site in Morgan County, Illinois, USA, to investigate the sensitivity of input parameters and initial conditions. The conceptual model for the site consists of 31 layers, each of which has a unique set of input parameters. The sensitivity of 11 parameters for each layer and 7 inputs as initial conditions is then investigated. For CO2 injectivity and plume size, about half of the uncertainty is due to only 4 or 5 of the 348 inputs and 3/4 of the uncertainty is due to about 15 of the inputs. The initial conditions and the properties of the injection layer and its neighbour layers contribute to most of the sensitivity. Overall, the simulation outputs are very sensitive to only a small fraction of the inputs. However, the parameters that are important for controlling CO2 injectivity are not the same as those controlling the plume size. The three most sensitive inputs for injectivity were the horizontal permeability of Mt Simon 11 (the injection layer), the initial fracture-pressure gradient, and the residual aqueous saturation of Mt Simon 11, while those for the plume area were the initial salt concentration, the initial pressure, and the initial fracture-pressure gradient. The advantages of requiring only a single set of simulation results, scalability to the proper parameter errors, and easy calculation of the composite sensitivities make this approach very cost-effective for estimating AoR uncertainty and guiding cost-effective site characterization, injection well design, and monitoring network design for CO2 storage projects.« less

Rainfall thresholds for the initiation of debris flows at La Honda, California

USGS Publications Warehouse

Wilson, R.C.; Wieczorek, G.F.

1995-01-01

A simple numerical model, based on the physical analogy of a leaky barrel, can simulate significant features of the interaction between rainfall and shallow-hillslope pore pressures. The leaky-barrel-model threshold is consistent with, but slightly higher than, an earlier, purely empirical, threshold. The number of debris flows triggered by a storm can be related to the time and amount by which the leaky-barrel-model response exceeded the threshold during the storm. -from Authors

Modeling and simulation of pressure waves generated by nano-thermite reactions

NASA Astrophysics Data System (ADS)

Martirosyan, Karen S.; Zyskin, Maxim; Jenkins, Charles M.; (Yuki) Horie, Yasuyuki

2012-11-01

This paper reports the modeling of pressure waves from the explosive reaction of nano-thermites consisting of mixtures of nanosized aluminum and oxidizer granules. Such nanostructured thermites have higher energy density (up to 26 kJ/cm3) and can generate a transient pressure pulse four times larger than that from trinitrotoluene (TNT) based on volume equivalence. A plausible explanation for the high pressure generation is that the reaction times are much shorter than the time for a shock wave to propagate away from the reagents region so that all the reaction energy is dumped into the gaseous products almost instantaneously and thereby a strong shock wave is generated. The goal of the modeling is to characterize the gas dynamic behavior for thermite reactions in a cylindrical reaction chamber and to model the experimentally measured pressure histories. To simplify the details of the initial stage of the explosive reaction, it is assumed that the reaction generates a one dimensional shock wave into an air-filled cylinder and propagates down the tube in a self-similar mode. Experimental data for Al/Bi2O3 mixtures were used to validate the model with attention focused on the ratio of specific heats and the drag coefficient. Model predictions are in good agreement with the measured pressure histories.

Dynamic changes of the intraocular pressure and the pressure of cerebrospinal fluid in nonglaucomatous neurological patients.

PubMed

González-Camarena, Pedro Iván; San-Juan, Daniel; González-Olhovich, Irene; Rodríguez-Arévalo, David; Lozano-Elizondo, David; Trenado, Carlos; Anschel, David J

2017-03-01

To describe the dynamic changes of the intraocular pressure (IOP) and intracranial pressure (ICP) with normal or pathological values (intracranial hypertension) in nonglaucomatous neurological patients during lumbar punction (LP). Case-control study, prospective measurement of tonometry in both groups referred for LP. Intraocular pressure, ICP and translaminar pressure difference (TPD) were compared pre- and post-LP. Thirty-six patients (72 eyes) with mean age of 38.5 (16-64) years and BMI of 26.81 kg/m 2 were analysed. The initial mean ICP was 12.81 (± 6.6) mmHg. The mean TPD before and after the LP was 1.48 mmHg and 0.65 mmHg, respectively. The mean IOP of both eyes decreased to 0.8 mmHg post-LP in patients with pathological ICP (p = 0.0193) and normal ICP (p = 0.006). We found a statistically significant decrease of the IOP post-LP compared to the pre-LP in both groups, being higher in patients with pathological ICP. There were no significant differences of the IOP in patients with normal versus pathological ICP pre-LP/post-LP; neither was found a correlation between ICP and IOP. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Author Correction: Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of falling.

PubMed

Lee, James; Webb, Graham; Shortland, Adam P; Edwards, Rebecca; Wilce, Charlotte; Jones, Gareth D

2018-05-12

In the original publication, the article title was incorrectly published as 'Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of failing'. The correct title should read as 'Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of falling'.

On the low pressure shock initiation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine based plastic bonded explosives

NASA Astrophysics Data System (ADS)

Vandersall, Kevin S.; Tarver, Craig M.; Garcia, Frank; Chidester, Steven K.

2010-05-01

In large explosive and propellant charges, relatively low shock pressures on the order of 1-2 GPa impacting large volumes and lasting tens of microseconds can cause shock initiation of detonation. The pressure buildup process requires several centimeters of shock propagation before shock to detonation transition occurs. In this paper, experimentally measured run distances to detonation for lower input shock pressures are shown to be much longer than predicted by extrapolation of high shock pressure data. Run distance to detonation and embedded manganin gauge pressure histories are measured using large diameter charges of six octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) based plastic bonded explosives (PBX's): PBX 9404; LX-04; LX-07; LX-10; PBX 9501; and EDC37. The embedded gauge records show that the lower shock pressures create fewer and less energetic "hot spot" reaction sites, which consume the surrounding explosive particles at reduced reaction rates and cause longer distances to detonation. The experimental data is analyzed using the ignition and growth reactive flow model of shock initiation in solid explosives. Using minimum values of the degrees of compression required to ignite hot spot reactions, the previously determined high shock pressure ignition and growth model parameters for the six explosives accurately simulate the much longer run distances to detonation and much slower growths of pressure behind the shock fronts measured during the shock initiation of HMX PBX's at several low shock pressures.

Accessing Ultrahigh-Pressure, Quasi-Isentropic States of Matter

NASA Astrophysics Data System (ADS)

Lorenz, Thomas

2004-11-01

A new approach to materials science at extreme pressures has been developed on the OMEGA laser, using a ramped plasma piston drive. The laser drives a shock through a solid plastic reservoir that unloads at the rear free surface, expands across a vacuum gap, and stagnates on the metal sample under study. This produces a gently increasing ram pressure, compressing the sample nearly isentropically. The peak pressure on the sample, diagnosed with VISAR measurements, can be varied by adjusting the laser energy and pulse length, gap size, and reservoir density, and obeys a simple scaling relation. [1] This has been demonstrated at OMEGA at pressures of P = 0.1-2.0 Mbar in Al foils. [2] In an important application, using in-flight x-ray radiography, the material strength of solid-state samples at high pressure can be inferred by measuring the reductions in the growth rates (stabilization) of Rayleigh-Taylor (RT) unstable interfaces. The material strength is predicted to be as much as an order of magnitude higher at P ˜ 1 Mbar than at ambient pressures. Initial RT measurements testing this prediction in foils of Al and V will be shown. We also use TEM microscopy of recovered targets to show that the samples never melted, and the presence of pressure-induced structural defects. [3,4] Experimental designs based on this drive have been developed for the NIF laser, predicting that solid-state samples can be quasi-isentropically driven to pressures an order of magnitude higher than on Omega - accessing new regimes of dense, high-pressure matter. [5] [1] J. Edwards et al., Phys. Rev. Lett., 92, 075002 (2004). [2] K.T. Lorenz et al., submitted, J. Appl. Phys. (2004). [3] J. McNaney et al., in press, Met. Mat. Trans. 35A (2004). [4] E.M. Bringa et al., to be submitted, Nature (2004). [5] B.A. Remington et al., in press, Met. Mat. Trans. 35A (2004). This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Multivariate Formation Pressure Prediction with Seismic-derived Petrophysical Properties from Prestack AVO inversion and Poststack Seismic Motion Inversion

NASA Astrophysics Data System (ADS)

Yu, H.; Gu, H.

2017-12-01

A novel multivariate seismic formation pressure prediction methodology is presented, which incorporates high-resolution seismic velocity data from prestack AVO inversion, and petrophysical data (porosity and shale volume) derived from poststack seismic motion inversion. In contrast to traditional seismic formation prediction methods, the proposed methodology is based on a multivariate pressure prediction model and utilizes a trace-by-trace multivariate regression analysis on seismic-derived petrophysical properties to calibrate model parameters in order to make accurate predictions with higher resolution in both vertical and lateral directions. With prestack time migration velocity as initial velocity model, an AVO inversion was first applied to prestack dataset to obtain high-resolution seismic velocity with higher frequency that is to be used as the velocity input for seismic pressure prediction, and the density dataset to calculate accurate Overburden Pressure (OBP). Seismic Motion Inversion (SMI) is an inversion technique based on Markov Chain Monte Carlo simulation. Both structural variability and similarity of seismic waveform are used to incorporate well log data to characterize the variability of the property to be obtained. In this research, porosity and shale volume are first interpreted on well logs, and then combined with poststack seismic data using SMI to build porosity and shale volume datasets for seismic pressure prediction. A multivariate effective stress model is used to convert velocity, porosity and shale volume datasets to effective stress. After a thorough study of the regional stratigraphic and sedimentary characteristics, a regional normally compacted interval model is built, and then the coefficients in the multivariate prediction model are determined in a trace-by-trace multivariate regression analysis on the petrophysical data. The coefficients are used to convert velocity, porosity and shale volume datasets to effective stress and then to calculate formation pressure with OBP. Application of the proposed methodology to a research area in East China Sea has proved that the method can bridge the gap between seismic and well log pressure prediction and give predicted pressure values close to pressure meassurements from well testing.

Recording pressure ulcer risk assessment and incidence.

PubMed

Plaskitt, Anne; Heywood, Nicola; Arrowsmith, Michaela

2015-07-15

This article reports on the introduction of an innovative computer-based system developed to record and report pressure ulcer risk and incidence at an acute NHS trust. The system was introduced to ensure that all patients have an early pressure ulcer risk assessment, which prompts staff to initiate appropriate management if a pressure ulcer is detected, thereby preventing further patient harm. Initial findings suggest that this electronic process has helped to improve the timeliness and accuracy of data on pressure ulcer risk and incidence. In addition, it has resulted in a reduced number of reported hospital-acquired pressure ulcers.

Influence of intermittent pressure, fluid flow, and mixing on the regenerative properties of articular chondrocytes.

PubMed

Carver, S E; Heath, C A

1999-11-05

Equine articular chondrocytes, embedded within a polyglycolic acid nonwoven mesh, were cultured with various combinations of intermittent pressure, fluid flow, and mixing to examine the effects of different physical stimuli on neochondrogenesis from young cells. The cell/polymer constructs were cultured first in 125 ml spinner flasks for 1, 2, or 4 weeks and then in a perfusion system with intermittent pressure for a total of up to 6 weeks. Additional constructs were either cultured for all 6 weeks in the spinner flasks or for 1 week in spinners followed by 5 weeks in the perfusion system without intermittent pressure. Tissue constructs cultivated for 2 or 4 weeks in spinner flasks followed by perfusion with intermittent pressure had significantly higher concentrations of both sulfated glycosaminoglycan and collagen than constructs cultured entirely in spinners or almost entirely in the pressure/perfusion system. Initial cultivation in the spinner flasks, with turbulent mixing, enhanced both cell attachment and early development of the extracellular matrix. Subsequent culture with perfusion and intermittent pressure appeared to accelerate matrix formation. While the correlation was much stronger in the pressurized constructs, the compressive modulus was directly proportional to the concentration of sulfated glycosaminoglycan in all physically stressed constructs. Constructs that were not stressed beyond the 1-week seeding period lost mechanical integrity upon harvest, suggesting that physical stimulation, particularly with intermittent pressure, of immature tissue constructs during their development may contribute to their ultimate biomechanical functionality. Copyright 1999 John Wiley & Sons, Inc.

New Reduced Two-Time Step Method for Calculating Combustion and Emission Rates of Jet-A and Methane Fuel With and Without Water Injection

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2004-01-01

A simplified kinetic scheme for Jet-A, and methane fuels with water injection was developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) or even simple FORTRAN codes that are being developed at Glenn. The two time step method is either an initial time averaged value (step one) or an instantaneous value (step two). The switch is based on the water concentration in moles/cc of 1x10(exp -20). The results presented here results in a correlation that gives the chemical kinetic time as two separate functions. This two step method is used as opposed to a one step time averaged method previously developed to determine the chemical kinetic time with increased accuracy. The first time averaged step is used at the initial times for smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, initial water to fuel mass ratio, temperature, and pressure. The second instantaneous step, to be used with higher water concentrations, gives the chemical kinetic time as a function of instantaneous fuel and water mole concentration, pressure and temperature (T4). The simple correlations would then be compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates were then used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide and NOx were obtained for Jet-A fuel and methane with and without water injection to water mass loadings of 2/1 water to fuel. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentrations of carbon monoxide and nitrogen oxide as functions of overall equivalence ratio, water to fuel mass ratio, pressure and temperature (T3). The temperature of the gas entering the turbine (T4) was also correlated as a function of the initial combustor temperature (T3), equivalence ratio, water to fuel mass ratio, and pressure.

Non-isothermal infiltration and tracer transport experiments on large soil columns

NASA Astrophysics Data System (ADS)

Sobotkova, Martina; Snehota, Michal; Cejkova, Eva; Tesar, Miroslav

2016-04-01

Isothermal and non-isothermal infiltration experiments were carried out in the laboratory on large undisturbed soil columns (19 cm in diameter, 25 cm high) taken at the experimental catchments Roklan (Sumava Mountains, Czech Republic) and Uhlirska (Jizera Mountains, Czech republic). The aim of the study was twofold. The first goal was to obtain water flow and heat transport data for indirect parameter estimation of thermal and hydraulic properties of soils from two sites by inverse modelling. The second aim was to investigate the extent of impact of the temperature on saturated hydraulic conductivity (Ksat) and dispersity of solute transport. The temperature of infiltrating water in isothermal experiment (20 °C) was equal to the initial temperature of the sample. For non-isothermal experiment water temperature was 5°C, while the initial temperature of the sample was 20°C as in previous case. The experiment was started by flooding the sample surface. Then water level was maintained at constant level throughout the infiltration run using the optical sensor and peristaltic pump. Concentration pulse of deuterium was applied at the top of the soil sample, during the steady state flow. Initial pressure head in the sample was close to field capacity. Two tensiometers and two temperature sensors were inserted in the soil sample in two depths (9 and 15 cm below the top of the sample). Two additional temperature sensors monitored the temperature entering and leaving the samples. Water drained freely through the perforated plate at the bottom of sample by gravity. Inflow and outflow water flux densities, water pressure heads and soil temperatures were monitored continuously during experiments. Effluent was sampled in regular time intervals and samples were analysed for deuterium concentrations by laser spectroscopy to develop breakthrough curves. The outcome of experiments are the series of measured water fluxes, pressure heads and temperatures ready for inverse modelling by dual permeability. The saturated hydraulic conductivity of soil columns was higher in the case of higher temperature of flowing water. The change was however not proportional to Ksat change induced by temperature change of viscosity only.

Comparison of Pressure Changes by Head and Neck Position between High-Volume Low-Pressure and Taper-Shaped Cuffs: A Randomized Controlled Trial

PubMed Central

Komasawa, Nobuyasu; Mihara, Ryosuke; Imagawa, Kentaro; Hattori, Kazuo; Minami, Toshiaki

2015-01-01

The present study compared changes in cuff pressure by head and neck position between high-volume low-pressure (HVLP) and taper-shaped (taper) cuffs in a prospective randomized clinical trial. Methods. Forty patients were intubated using tracheal tubes with either HVLP (n = 20; HVLP group) or taper-shaped (n = 20; Taper group) cuffs. Initial cuff pressure was adjusted to 15, 20, or 25 cmH2O in the neutral position. Cuff pressure was evaluated after changing the head and neck positions to flexion, extension, and rotation. Results. Cuff pressure significantly increased with flexion in both HVLP and Taper groups at all initial cuff pressures. It significantly increased with extension in the HVLP group, but not in the Taper group. Cuff pressure did not significantly differ with rotation in either group and was significantly smaller in the Taper group during flexion and extension than in the HVLP group, regardless of initial cuff pressure. Conclusion. Cuff pressure changes with head and neck flexion and extension were smaller in the Taper group than in the HVLP group. Our results highlight the potential for taper cuffs to prevent excessive cuff pressure increases with positional changes in the head and neck. This trial is registered with UMIN000016119. PMID:26509152

High-pressure treatment for shelf-life extension and quality improvement of oysters cooked in a traditional Taiwanese oyster omelet.

PubMed

Lai, Kung-Ming; Chi, Hsin-Yi; Hsu, Kuo-Chiang

2010-01-01

Whole oysters were processed using high-pressure (HP) treatment at 250 and 300 MPa for 0 to 10 min and stored at 4 degrees Celsius for up to 28 days. HP-treated oysters and untreated oysters were evaluated for lipid oxidation, growth of microorganisms, and sensory characteristics after cooking at 160 degrees Celsius for 90 s. Microbial counts after HP treatment revealed that the bacterial load was initially reduced at all pressures. HP-treated oysters had significantly higher pH and moisture (P < 0.05) relative to control (untreated) oysters during storage. HP treatment increased lipid oxidation with unpleasant odor during storage compared with the control. HP treatment decreased redness but did not significantly affect the brightness and yellowness of cooked oysters. From tests of mechanical properties, 300 MPa-treated oysters after cooking had significantly increased toughness as measured by cutting force. HP-treated oysters after cooking received higher quality scores than did the control during the storage trial. Results indicated that 300 MPa for 2 min is the optimum HP treatment that results in oysters most acceptable for oyster omelets during storage at 4 degrees Celsius, and this treatment may extend the shelf life of these oysters to 21 days.

Laboratory hydraulic fracturing experiments in intact and pre-fractured rock

USGS Publications Warehouse

Zoback, M.D.; Rummel, F.; Jung, R.; Raleigh, C.B.

1977-01-01

Laboratory hydraulic fracturing experiments were conducted to investigate two factors which could influence the use of the hydrofrac technique for in-situ stress determinations; the possible dependence of the breakdown pressure upon the rate of borehole pressurization, and the influence of pre-existing cracks on the orientation of generated fractures. The experiments have shown that while the rate of borehole pressurization has a marked effect on breakdown pressures, the pressure at which hydraulic fractures initiate (and thus tensile strength) is independent of the rate of borehole pressurization when the effect of fluid penetration is negligible. Thus, the experiments indicate that use of breakdown pressures rather than fracture initiation pressures may lead to an erroneous estimate of tectonic stresses. A conceptual model is proposed to explain anomalously high breakdown pressures observed when fracturing with high viscosity fluids. In this model, initial fracture propagation is presumed to be stable due to large differences between the borehole pressure and that within the fracture. In samples which contained pre-existing fractures which were 'leaky' to water, we found it possible to generate hydraulic fractures oriented parallel to the direction of maximum compression if high viscosity drilling mud was used as the fracturing fluid. ?? 1977.

Potential improvements in turbofan engine fuel economy

NASA Technical Reports Server (NTRS)

Hines, R. W.; Gaffin, W. O.

1976-01-01

The method developed for initial evaluation of possible performance improvements in the NASA Aircraft Energy Efficiency Program, directed toward improving the fuel economy of turbofan engines, is outlined, and results of the evaluation of 100 candidate engine modifications are presented. The study indicates that fuel consumption improvements of as much as 5% may be possible in current JT3D, JT8D, and JT9D turbofan engines. Aerodynamic, thermodynamic, material, and structural advances are expected to yield fuel consumption improvements on the order of 10 to 15% in advanced turbofan engines, with the greatest improvement stemming from significantly higher cycle pressure ratios. Higher turbine temperature and fan bypass ratios are also expected to contribute to fuel conservation.

Stomach distension increases efferent muscle sympathetic nerve activity and blood pressure in healthy humans.

PubMed

Rossi, P; Andriesse, G I; Oey, P L; Wieneke, G H; Roelofs, J M; Akkermans, L M

1998-12-11

Although the enteric nervous system is usually described as a separate and independent entity, animal studies show that gastric distension causes a reflex increase in arterial pressure and a sympathetically mediated increase in heart rate and peripheral vascular resistance. To assess the influence of gastric distension on sympathetic outflow and blood pressure, we recorded muscle sympathetic nerve activity (MSNA) from the peroneal nerve by microneurography in eight healthy volunteers. The stomach was distended by means of a barostat, using a single staircase protocol by which pressure was increased by 2 mmHg every 3 min. Gastric sensory function was assessed at each distension step by using a visual analog scale (VAS) for sensations of fullness, nausea and pain. For comparison, we also performed a cold pressor test. The MSNA increased on barostat-induced gastric distension with an almost concomitant elevation of blood pressure. The increase in both was proportional to the intragastric pressure and both decreased towards initial values after the end of distension. Heart rate increased inconsistently and only at higher distension pressures that were associated with high VAS scores. The opposite was found for the cold pressor test. The results of this study confirm the existence of a functional relationship between gastrointestinal distension and cardiovascular function. Decrease in this gastrovascular response may play a role in postprandial hypotension in the elderly, since the MSNA responses to simulated microgravity decrease with age.

The evaluation of daily living activities, pressure sores and risk factors.

PubMed

Aydın, Gökçen; Mucuk, Salime

2015-01-01

This study was conducted to assess daily living activities, pressure sores and risk factors. This was a descriptive study. The study was conducted at a rehabilitation center with 188 individuals participating in the study. Data were collected with a questionnaire form, Activities of Daily Living Scale (ADLS), Instrumental Activities of Daily Living Scale (IADLS) and Braden Risk Assessment Scale (BRAS). Among the participants, 48.9% were dependent according to activities of daily living and 71.8% were dependent on instrumental activities of daily living. It was noted that 4.8% had pressure sores and 38.8% were at high risk. A strong and positive correlation was found among ADLS, IADLS, and BRAS scores (p < .001). Participants who had a low body mass index, had lived at the rehabilitation center for a long time, and were fed on regime 1 or 2, had a higher risk of developing pressure sores (p < .001). Individuals who were dependent according to ADLS and IADLS were at increased risk for the development of pressure sores. Individuals who are treated at rehabilitation centers should be periodically assessed in terms of risk. Pressure sore development can be prevented with appropriate nursing interventions. To reduce the risk of developing pressure sores, nurses should describe the individual's degree of dependency according to ADLS and IADLS and initiate preventive nursing care. © 2014 Association of Rehabilitation Nurses.

Experimental Studies on Dehydration Embrittlement of Serpentinized Peridotite and Effect of Pressure on Creep of Olivine

NASA Astrophysics Data System (ADS)

Xia, Gang

The origin of intermediate depth earthquakes has been debated for 90 years yet is still under active discussion. These earthquakes are localized in double seismic zones in descending lithosphere; both zones originate very close to oceanic trenches. A leading proposed initiation mechanism for these earthquakes since 1968 has been dehydration embrittlement of serpentine under stress. Despite the considerable evidence favoring this mechanism, a major argument against it has been that the lower seismic zone initiates at ˜40 km depth almost immediately below trenches and there does not appear to be a vehicle to carry water sufficiently deep to hydrate otherwise dry lithosphere. To directly address this problem, an experimental study has been carried out to investigate the minimum amount of serpentine that is required to trigger the dehydration embrittlement instability in serpentinized peridotite at high pressure (1-3 GPa) and temperature (720-750˚C). The results show that embrittlement occurs during dehydration of antigorite (the phase of serpentine stable at elevated pressure) in a wide range of compositions but both nearly dry peridotite and extensively altered peridotite are ductile. Fresh, unaltered, synthetic harzburgite and harzburgite with 4 vol% distributed antigorite are ductile, as are specimens with greater than 65% antigorite. Only compositions between 8 vol% and 65 vol% antigorite develop the instability. We suggest that very small degrees of serpentinization do not release sufficient H 2O to trigger the instability and that extensive serpentinization avoids the instability because soft, ductile, antigorite becomes the interconnected matrix with olivine and pyroxene existing only as isolated crystals. In that case, dehydration simply facilitates flow. These systematics suggest that small amounts of H2O transported down deep normal (bending) faults at trenches are sufficient to enable the instability in the lower seismic zones, thus providing additional support for dehydration embrittlement as the mechanism of intermediate-depth earthquakes. At the other end of the spectrum of serpentinization, these results are consistent with previous suggestions that extensive dehydration of altered subducting crust and mantle release copious amounts of H2O that rise to the surface of the descending slab and react with the cool mantle of the overlying plate to lead to extensive serpentinization, thereby explaining serpentine diapers in the forearc and lack of seismicity along the plate interface deeper than about 35 km. Another long-lived controversy in mantle geophysics involves the pressure dependence of creep in olivine, the most abundant and softest phase in unaltered mantle rocks. The pressure dependence of any thermodynamically-controlled phenomenon is commonly expressed as the activation volume, DeltaV*. Previous experimental investigations on the effect of pressure on creep in olivine have produced bimodal results. DeltaV* obtained from solid-medium (Griggs) and gas-medium (Paterson) deformation apparatus at relatively lower pressures is ˜15 cm3/mol or higher. In contrast, higher-pressure studies using multianvil apparatus at sites of synchrotron X-radiation (D-DIA apparatus) report a DeltaV* near zero. To decipher this enigma and to provide a much-needed calibration of stress in the D-DIA apparatus, I have conducted systematic experiments on a synthetic, iron-free, forsterite at 1200 ˚C and pressure between 1 and 2.5 GPa using the UCR 5 GPa modified Griggs apparatus, the only apparatus capable of performing these experiments. Our results show a robust DeltaV* value of 12 +/- 2 cm3/mol, indicating a fairly significant pressure dependence of creep in olivine to pressures of ˜3 GPa (approximately 100 km). In collaboration with other experimentalists, we plan to measure the DeltaV* for creep of this material over a pressure range of 2-8 GPa in the D-DIA apparatus to both calibrate stress measurement in the D-DIA and resolve the question of change in DeltaV* at higher pressures.

Negative Pressures and the First Water Siphon Taller than 10.33 Meters

PubMed Central

Vera, Francisco; Rivera, Rodrigo; Romero-Maltrana, Diego; Villanueva, Jaime

2016-01-01

A siphon is a device that is used to drain a container, with water rising inside a hose in the form of an inverted U and then going down towards a discharge point placed below the initial water level. The siphon is the first of a number of inventions of the ancients documented about 2.000 years ago by Hero of Alexandria in his treatise Pneumatics, and although the explanation given by Hero was essentially correct, there is nowadays a controversy about the underlying mechanism that explains the working of this device. Discussions concerning the physics of a siphon usually refer to concepts like absolute negative pressures, the strength of liquid’s cohesion and the possibility of a siphon working in vacuum or in the presence of bubbles. Torricelli understood the working principle of the barometer and the impossibility of pumping water out of wells deeper than 10.33 m. Following Torricelli’s ideas it would also not be possible to build a siphon that drives pure water to ascend higher than 10.33 m. In this work, we report the first siphon that drives water (with surfactant) to ascend higher than the Torricellian limit. Motivated by the rising of sap in trees, we built a 15.4 m siphon that shows that absolute negative pressures are not prohibited, that cohesion plays an important role in transmitting forces through a fluid, and that surfactants can help to the transport of water in a metastable regime of negative pressures. PMID:27054847

40 CFR 146.13 - Operating, monitoring and reporting requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... pressure in the injection zone during injection does not initiate new fractures or propagate existing fractures in the injection zone. In no case shall injection pressure initiate fractures in the confining...

40 CFR 146.13 - Operating, monitoring and reporting requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... pressure in the injection zone during injection does not initiate new fractures or propagate existing fractures in the injection zone. In no case shall injection pressure initiate fractures in the confining...

40 CFR 146.13 - Operating, monitoring and reporting requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... pressure in the injection zone during injection does not initiate new fractures or propagate existing fractures in the injection zone. In no case shall injection pressure initiate fractures in the confining...

40 CFR 146.13 - Operating, monitoring and reporting requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... pressure in the injection zone during injection does not initiate new fractures or propagate existing fractures in the injection zone. In no case shall injection pressure initiate fractures in the confining...

40 CFR 146.13 - Operating, monitoring and reporting requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... pressure in the injection zone during injection does not initiate new fractures or propagate existing fractures in the injection zone. In no case shall injection pressure initiate fractures in the confining...

High-pressure EPR spectroscopy studies of the E. coli lipopolysaccharide transport proteins LptA and LptC.

PubMed

Schultz, Kathryn M; Klug, Candice S

2017-12-01

The use of pressure is an advantageous approach to the study of protein structure and dynamics because it can shift the equilibrium populations of protein conformations toward higher energy states that are not of sufficient population to be observable at atmospheric pressure. Recently, the Hubbell group at the University of California, Los Angeles, reintroduced the application of high pressure to the study of proteins by electron paramagnetic resonance (EPR) spectroscopy. This methodology is possible using X-band EPR spectroscopy due to advances in pressure intensifiers, sample cells, and resonators. In addition to the commercial availability of the pressure generation and sample cells by Pressure Biosciences Inc., a five-loop-four-gap resonator required for the initial high pressure EPR spectroscopy experiments by the Hubbell group, and those reported here, was designed by James S. Hyde and built and modified at the National Biomedical EPR Center. With these technological advances, we determined the effect of pressure on the essential periplasmic lipopolysaccharide (LPS) transport protein from Escherichia coli , LptA, and one of its binding partners, LptC. LptA unfolds from the N-terminus to the C-terminus, binding of LPS does not appreciably stabilize the protein under pressure, and monomeric LptA unfolds somewhat more readily than oligomeric LptA upon pressurization to 2 kbar. LptC exhibits a fold and relative lack of stability upon LPS binding similar to LptA, yet adopts an altered, likely monomeric, folded conformation under pressure with only its C-terminus unraveling. The pressure-induced changes likely correlate with functional changes associated with binding and transport of LPS.

Hydroprocessing of rubber seed oil to renewable fuels

NASA Astrophysics Data System (ADS)

Tran, Tan Viet; Phung, Minh Tri

2017-09-01

Hydroprocessing of rubber seed oil (RSO) with various types of alumina-silica support catalyst was conducted at 400°C and a hydrogen partial pressure of 3.0 MPa in 3 hours. The effects of the alumina-silica and metal doping on alumina-silica on the conversion, and distribution of oil fraction products (initial boiling point (IBP) to 80°C, from 80-200°C, from 200-360°C and higher than 360°C boiling point) were investigated. Compared to the results obtained when using Mo@Al2O3-SiO2, hydroprocessing of RSO resulted in a higher conversion and much higher yield of the light fraction (BP <230°C). Both alumina-silica catalysts led to an improved conversion as well as a higher light fraction yield. Results show that hydroprocessing of RSO with metal doping on alumina-silica support was more efficient than that only Al2O3-SiO2.

Dynamic Asphaltene-Stearic Acid Competition at the Oil-Water Interface.

PubMed

Sauerer, Bastian; Stukan, Mikhail; Buiting, Jan; Abdallah, Wael; Andersen, Simon

2018-05-15

Interfacial tension (IFT) is one of the major parameters which govern the fluid flow in oil production and recovery. This paper investigates the interfacial activity of different natural surfactants found in crude oil. The main objective was to better understand the competition between carboxylic acids and asphaltenes on toluene/water interfaces. Dynamic IFT was measured for water-in-oil pendant drops contrary to most studies using oil-in-water drops. Stearic acid (SA) was used as model compound for surface-active carboxylic acids in crude. The influence of concentration of these species on dynamic IFT between model oil and deionized water was examined. The acid concentrations were of realistic values (total acid number 0.1 to 2 mg KOH/g oil) while asphaltene concentrations were low and set between 10 and 100 ppm. In mixtures, the initial surface pressure was entirely determined by the SA content while asphaltenes showed a slow initial diffusion to the interface followed by increased adsorption at longer times. The final surface pressure was higher for asphaltenes compared to SA, but for binaries, the final surface pressure was always lower than the sum of the individuals. At high SA concentration, surface pressures of mixtures were dominated entirely by the SA, although, Langmuir isotherm analysis shows that asphaltenes bind to the interface 200-250 times stronger than SA. The surface area/molecule for both SA and asphaltenes were found to be larger than the values reported in recent literature. Various approaches to dynamic surface adsorption were tested, showing that apparent diffusivity of asphaltenes is very low, in agreement with other works. Hence, the adsorption is apparently under barrier control. A possible hypothesis is that at the initial phase of the experiment and at lower concentration of asphaltenes, the interface is occupied by stearic acid molecules forming a dense layer of hydrocarbon chains that may repel the asphaltenes.

Detonation mode and frequency analysis under high loss conditions for stoichiometric propane-oxygen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Scott I.; Lee, Bok Jik; Shepherd, Joseph E.

In this paper, the propagation characteristics of galloping detonations were quantified with a high-time-resolution velocity diagnostic. Combustion waves were initiated in 30-m lengths of 4.1-mm inner diameter transparent tubing filled with stoichiometric propane–oxygen mixtures. Chemiluminescence from the resulting waves was imaged to determine the luminous wave front position and velocity every 83.3 μ. As the mixture initial pressure was decreased from 20 to 7 kPa, the wave was observed to become increasingly unsteady and transition from steady detonation to a galloping detonation. While wave velocities averaged over the full tube length smoothly decreased with initial pressure down to half ofmore » the Chapman–Jouguet detonation velocity (D CJ) at the quenching limit, the actual propagation mechanism was seen to be a galloping wave with a cycle period of approximately 1.0 ms, corresponding to a cycle length of 1.3–2.0 m or 317–488 tube diameters depending on the average wave speed. The long test section length of 7300 tube diameters allowed observation of up to 20 galloping cycles, allowing for statistical analysis of the wave dynamics. In the galloping regime, a bimodal velocity distribution was observed with peaks centered near 0.4 D CJ and 0.95 D CJ. Decreasing initial pressure increasingly favored the low velocity mode. Galloping frequencies ranged from 0.8 to 1.0 kHz and were insensitive to initial mixture pressure. Wave deflagration-to-detonation transition and detonation failure trajectories were found to be repeatable in a given test and also across different initial mixture pressures. The temporal duration of wave dwell at the low and high velocity modes during galloping was also quantified. It was found that the mean wave dwell duration in the low velocity mode was a weak function of initial mixture pressure, while the mean dwell time in the high velocity mode depended exponentially on initial mixture pressure. Analysis of the velocity histories using dynamical systems ideas demonstrated trajectories that varied from stable to limit cycles to aperiodic motion with decreasing initial pressure. Finally, the results indicate that galloping detonation is a persistent phenomenon at long tube lengths.« less

Detonation mode and frequency analysis under high loss conditions for stoichiometric propane-oxygen

DOE PAGES

Jackson, Scott I.; Lee, Bok Jik; Shepherd, Joseph E.

2016-03-24

In this paper, the propagation characteristics of galloping detonations were quantified with a high-time-resolution velocity diagnostic. Combustion waves were initiated in 30-m lengths of 4.1-mm inner diameter transparent tubing filled with stoichiometric propane–oxygen mixtures. Chemiluminescence from the resulting waves was imaged to determine the luminous wave front position and velocity every 83.3 μ. As the mixture initial pressure was decreased from 20 to 7 kPa, the wave was observed to become increasingly unsteady and transition from steady detonation to a galloping detonation. While wave velocities averaged over the full tube length smoothly decreased with initial pressure down to half ofmore » the Chapman–Jouguet detonation velocity (D CJ) at the quenching limit, the actual propagation mechanism was seen to be a galloping wave with a cycle period of approximately 1.0 ms, corresponding to a cycle length of 1.3–2.0 m or 317–488 tube diameters depending on the average wave speed. The long test section length of 7300 tube diameters allowed observation of up to 20 galloping cycles, allowing for statistical analysis of the wave dynamics. In the galloping regime, a bimodal velocity distribution was observed with peaks centered near 0.4 D CJ and 0.95 D CJ. Decreasing initial pressure increasingly favored the low velocity mode. Galloping frequencies ranged from 0.8 to 1.0 kHz and were insensitive to initial mixture pressure. Wave deflagration-to-detonation transition and detonation failure trajectories were found to be repeatable in a given test and also across different initial mixture pressures. The temporal duration of wave dwell at the low and high velocity modes during galloping was also quantified. It was found that the mean wave dwell duration in the low velocity mode was a weak function of initial mixture pressure, while the mean dwell time in the high velocity mode depended exponentially on initial mixture pressure. Analysis of the velocity histories using dynamical systems ideas demonstrated trajectories that varied from stable to limit cycles to aperiodic motion with decreasing initial pressure. Finally, the results indicate that galloping detonation is a persistent phenomenon at long tube lengths.« less

Endothelial protection: avoiding air bubble formation at the phacoemulsification tip.

PubMed

Kim, Eung Kweon; Cristol, Stephen M; Kang, Shin J; Edelhauser, Henry F; Yeon, Dong-Soo; Lee, Jae Bum

2002-03-01

To investigate the conditions under which bubbles form during phacoemulsification. Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea. In the first part of the study, the partial pressure of oxygen (pO(2)) was used as a surrogate measure for the partial pressure of air. Irrigation solutions packaged in glass and plastic containers were studied. A directly vented glass bottle was also tested. The pO(2) of the various irrigation solutions was measured as the containers were emptied. In the second part, phacoemulsification procedures were performed in rabbit eyes with different power settings and different irrigation solutions. Intracameral bubble formation during the procedure was recorded. Following the phacoemulsification procedures, the corneas were stained for F-actin and examined for endothelial injury. The initial pO(2) in irrigation solutions packaged in glass bottles was about half that at atmospheric levels; in solutions packaged in plastic, it was at atmospheric levels. As irrigation solutions were drained from the container, the pO(2) of the solution tended to rise toward atmospheric levels. The rate of pO(2) increase was markedly reduced by using a directly vented glass bottle. In the phacoemulsification procedures, bubble formation was most likely to occur with higher pO(2) and higher power settings. Observation of bubbles by the surgeon was highly correlated with endothelial damage. Keeping the pO(2) low reduced the risk of endothelial damage, especially at higher phacoemulsification powers. The packaging of irrigation solutions was the most important factor in controlling the initial pO(2) of the solution. The pO(2) can be minimized throughout a phacoemulsification procedure by using a directly vented glass bottle.

Ares I-X Post Flight Ignition Overpressure Review

NASA Technical Reports Server (NTRS)

Alvord, David A.

2010-01-01

Ignition Overpressure (IOP) is an unsteady fluid flow and acoustic phenomena caused by the rapid expansion of gas from the rocket nozzle within a ducted launching space resulting in an initially higher amplitude pressure wave. This wave is potentially dangerous to the structural integrity of the vehicle. An in-depth look at the IOP environments resulting from the Ares I-X Solid Rocket Booster configuration showed high correlation between the pre-flight predictions and post-flight analysis results. Correlation between the chamber pressure and IOP transients showed successful acoustic mitigation, containing the strongest IOP waves below the Mobile Launch Pad deck. The flight data allowed subsequent verification and validation of Ares I-X unsteady fluid ducted launcher predictions, computational fluid dynamic models, and strong correlation with historical Shuttle data.

A Wireless Lingual Feedback Device to Reduce Overpressures in Seated Posture: A Feasibility Study

PubMed Central

Chenu, Olivier; Vuillerme, Nicolas; Demongeot, Jacques; Payan, Yohan

2009-01-01

Background Pressure sores are localized injuries to the skin and underlying tissues and are mainly resulting from overpressure. Paraplegic peoples are particularly subjects to pressure sores because of long-time seated postures and sensory deprivation at the lower limbs. Methodology/Principal Findings Here we report outcomes of a feasibility trial involving a biofeedback system aimed at reducing buttock overpressure whilst an individual is seated. The system consists of (1) pressure sensors, (2) a laptop coupling sensors and actuator (3) a wireless Tongue Display Unit (TDU) consisting of a circuit embedded in a dental retainer with electrodes put in contact with the tongue. The principle consists in (1) detecting overpressures in people who are seated over long periods of time, (2) estimating a postural change that could reduce these overpressures and (3) communicating this change through directional information transmitted by the TDU.Twenty-four healthy subjects voluntarily participated in this study. Twelve healthy subjects initially formed the experimental group (EG) and were seated on a chair with the wireless TDU inside their mouth. They were asked to follow TDU orders that were randomly spread throughout the session. They were evaluated during two experimental sessions during which 20 electro-stimulations were sent. Twelve other subjects, added retrospectively, formed the control group (CG). These subjects participated in one session of the same experiment without any biofeedback.Three dependent variables were computed: (1) the ability of subjects to reach target posture (EG versus CG), (2) high pressure reductions after a biofeedback (EG versus CG) and (3) the level of these reductions relative to their initial values (EG only). Results show (1) that EG reached target postures in 90.2% of the trials, against 5,3% in the CG, (2) a significant reduction in overpressures in the EG compared to the CG and (3), for the EG, that the higher the initial pressures were, the more they were decreased. Conclusions/Significance The findings suggest that, in this trial, subjects were able to use a tongue tactile feedback system to reduce buttock overpressure while seated. Further evaluation of this system on paraplegic subjects remains to be done. PMID:19888336

Experimental analysis of quasi-static and dynamic fracture initiation toughness of gy4 armor steel material

NASA Astrophysics Data System (ADS)

Ren, Peng; Guo, Zitao

Quasi-static and dynamic fracture initiation toughness of gy4 armour steel material are investigated using three point bend specimen. The modified split Hopkinson pressure bar (SHPB) apparatus with digital image correlation (DIC) system is applied to dynamic loading experiments. Full-field deformation measurements are obtained by using DIC to elucidate on the strain fields associated with the mechanical response. A series of experiments are conducted at different strain rate ranging from 10-3 s-1 to 103 s-1, and the loading rate on the fracture initiation toughness is investigated. Specially, the scanning electron microscope imaging technique is used to investigate the fracture failure micromechanism of fracture surfaces. The gy4 armour steel material fracture toughness is found to be sensitive to strain rate and higher for dynamic loading as compared to quasi-static loading. This work is supported by National Nature Science Foundation under Grant 51509115.

Effect of Initiation Time of Hydrostatic Pressure Shock on Chromosome Set Doubling of Tetraploidization in Turbot Scophthalmus maximus.

PubMed

Zhu, Xiangping; Lin, Zhengmei; Wu, Zhihao; Li, Jiandong; You, Feng

2017-10-01

The objective of the study was to clarify the effects of initiation time on chromosome set doubling induced by hydrostatic pressure shock through nuclear phase fluorescent microscopy in turbot Scophthalmus maximus. The ratio of developmentally delayed embryo and chromosome counting was used to assess induction efficiency. For the embryos subjected to a pressure of 67.5 MPa for 6 min at prometaphase (A group), chromosomes recovered to the pre-treatment condition after 11-min recovering. The first nuclear division and cytokinesis proceeded normally. During the second cell cycle, chromosomes did not enter into metaphase after prometaphase, but spread around for about 13 min, then assembled together and formed a large nucleus without anaphase separation; the second nuclear division and cytokinesis was inhibited. The ratio of developmentally delayed embryo showed that the second mitosis of 78% A group embryo was inhibited. The result of chromosome counting showed that the tetraploidization rate of A group was 72%. For the embryos subjected to a pressure of 67.5 MPa for 6 min at anaphase (B group), chromosomes recovered to the pre-treatment condition after about 31-min recovering. Afterwards, one telophase nucleus formed without anaphase separation; the first nuclear division was inhibited. The time of the first cleavage furrow occurrence of B group embryos delayed 27 min compared with that of A group embryos. With the first cytokinesis proceeding normally, 81.3% B group embryos were at two-cell stage around the middle of the second cell cycle after treatment. Those embryos were one of the two blastomeres containing DNA and the other without DNA. The first nuclear division of those embryos was inhibited. During the third cell cycle after treatment, 65.2% of those abovementioned embryos were at four-cell stage, cytokinesis occurred in both blastomeres, and nuclear division only occurred in the blastomere containing DNA. Of those abovementioned embryos, 14.0% were at three-cell stage and cytokinesis only occurred in the blastomere containing DNA. The result of chromosome counting showed that the tetraploidization rate of B group was only 7%. To summarize what had been mentioned above, mechanisms on chromosome set doubling of tetraploid induction would be different with different initiation time of hydrostatic pressure treatment. Chromosome set doubling was mainly due to inhibition of the second mitosis when hydrostatic pressure treatment was performed at prometaphase. Otherwise, chromosome set doubling was mainly due to inhibition of the first nuclear division when hydrostatic pressure treatment was performed at anaphase. Induction efficiency of tetraploidization resulted from inhibition of the second cleavage was higher than which resulted from inhibition of the first nuclear division. This study was the first to reveal biological mechanisms on the two viewpoints of chromosome set doubling through effect of initiation time of hydrostatic pressure treatment on chromosome set doubling in tetraploid induction.

Self-Pressurization of a Flightweight, Liquid Hydrogen Tank: Simulation and Comparison with Experiments

NASA Technical Reports Server (NTRS)

Stewart, Mark E. M.; Moder, Jeffrey P.

2016-01-01

This paper presents ANSYS Fluent simulation results and analysis for self-pressurization of a flightweight, cryogenic, liquid hydrogen tank in 1-g. These results are compared with experimental data, in particular, pressure evolution and temperature measurements at a set of sensors. The simulations can be analyzed to identify and quantify heat flows in the tank. Heat flows change over time and influence the self-pressurization process. The initial rate of self-pressurization is sensitive to the initial temperature profile near the interface. Uncertainty in saturation pressure data and the accuracy of experimental measurements complicate simulation of self-pressurization. Numerical issues encountered, and their resolution, are also explained.

Expansion of high-temperature; high-pressure data set for coal gasification. Fifth quarterly report, September 28-December 28, 1985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solomon, P.R.; Serio, M.A.; Hamblen, D.G.

1985-01-01

During the fifth quarter, the gas mixing station for the high pressure reactor (HPR) system was completed. This station allows us to make reproducible binary mixtures of any two gases. It will be used for pyrolysis experiments in helium/nitrogen or oxygen/nitrogen and gasification experiments in helium/nitrogen or oxygen/nitrogen and gasification experiments in carbon dioxide/nitrogen. In addition, work began on modifications of the HPR system for high pressure (600 psig) operation. A limited amount of data was taken with the HPR system due to the modifications for the mixing station. However, the test plan experiments for pyrolysis in mixtures of heliummore » and nitrogen were completed. In general, there is a slightly higher yield of volatiles and lower yield of char as the helium content (heating rate) increases. A new technique for measuring char reactivity resulted from an Army SBIR program and was further developed under our other METC Contract. It has also been used to characterize chars generated under the current program. It was evident that the severity of the thermal treatment had a direct effect on char reactivity. In this regard, rapid heating to a relatively low temperature was most favorable while slow heating to a high temperature was least favorable. With regard to pressure effects on reactivity, our preliminary data indicated that higher pressures produce chars lower initial reactivity. A total of four experiments were done in the heated tube reactor (HTR) at 60 psig, 800/sup 0/C maximum tube temperature. The trends are the same as observed in the atmospheric pressure experiments for the same tube temperature and cold gas velocity. During the past quarter, a particle temperature (PT) model was under development for the high pressure entrained flow reactor (HPR). 5 refs., 5 figs.« less

Driving pressure and mechanical power: new targets for VILI prevention.

PubMed

Tonetti, Tommaso; Vasques, Francesco; Rapetti, Francesca; Maiolo, Giorgia; Collino, Francesca; Romitti, Federica; Camporota, Luigi; Cressoni, Massimo; Cadringher, Paolo; Quintel, Michael; Gattinoni, Luciano

2017-07-01

Several factors have been recognized as possible triggers of ventilator-induced lung injury (VILI). The first is pressure (thus the 'barotrauma'), then the volume (hence the 'volutrauma'), finally the cyclic opening-closing of the lung units ('atelectrauma'). Less attention has been paid to the respiratory rate and the flow, although both theoretical considerations and experimental evidence attribute them a significant role in the generation of VILI. The initial injury to the lung parenchyma is necessarily mechanical and it could manifest as an unphysiological distortion of the extracellular matrix and/or as micro-fractures in the hyaluronan, likely the most fragile polymer embedded in the matrix. The order of magnitude of the energy required to break a molecular bond between the hyaluronan and the associated protein is 1.12×10 -16 Joules (J), 70-90% higher than the average energy delivered by a single breath of 1L assuming a lung elastance of 10 cmH 2 O/L (0.5 J). With a normal statistical distribution of the bond strength some polymers will be exposed each cycle to an energy large enough to rupture. Both the extracellular matrix distortion and the polymer fractures lead to inflammatory increase of capillary permeability with edema if a pulmonary blood flow is sufficient. The mediation analysis of higher vs. lower tidal volume and PEEP studies suggests that the driving pressure, more than tidal volume, is the best predictor of VILI, as inferred by increased mortality. This is not surprising, as both tidal volume and respiratory system elastance (resulting in driving pressure) may independently contribute to the mortality. For the same elastance driving pressure is a predictor similar to plateau pressure or tidal volume. Driving pressure is one of the components of the mechanical power, which also includes respiratory rate, flow and PEEP. Finding the threshold for mechanical power would greatly simplify assessment and prevention of VILI.

Anchorage performance of a high-pressure pre-tightening resin anchor with a compressed grouting body

PubMed Central

Tian, Jiansheng; Hu, Li

2017-01-01

Supports for deep mine roadways located in soft surrounding rock face several problems: difficulty in applying pre-tightening force, low bearing capacity, and poor initial support. To solve these problems, this study proposes a high-pressure pre-tightening resin anchor with a compressed grouting body for use in soft and fractured rock surrounding a deep roadway. Using model experiments, we analyzed the anchorage performance of the proposed anchor and a conventional tensile-type anchor for three different values of the elastic modulus of the surrounding rock. The results showed that regardless of the surrounding rock type, the peak micro-strain (642–541) and displacement (6.09–6.5 mm) at the pull-out end of the proposed anchor were always smaller than the peak micro-strain (1433–1105) and displacement (8.77–9.2 mm) at the pull-out end of the conventional anchor. Furthermore, as the anchor’s pre-tightening force increased from 20 kN to 120 kN, the anchor’s strain remained concentrated over a length of 0.4 m from the bearing end. Compared with conventional tensile-type anchors, the proposed high-pressure pre-tightening resin anchor with a compressed grouting body has a higher ultimate bearing capacity, allows the grouting length to be decreased to 0.4 m, and provides initial support resistance. PMID:28196084

Energy balance during underwater implosion of ductile metallic cylinders.

PubMed

Chamberlin, Ryan E; Guzas, Emily L; Ambrico, Joseph M

2014-11-01

Energy-based metrics are developed and applied to a numerical test case of implosion of an underwater pressure vessel. The energy metrics provide estimates of the initial energy in the system (potential energy), the energy released into the fluid as a pressure pulse, the energy absorbed by the imploding structure, and the energy absorbed by air trapped within the imploding structure. The primary test case considered is the implosion of an aluminum cylinder [diameter: 2.54 cm (1 in.), length: 27.46 cm (10.81 in.)] that collapses flat in a mode-2 shape with minimal fracture. The test case indicates that the structure absorbs the majority (92%) of the initial energy in the system. Consequently, the energy emitted as a pressure pulse into the fluid is a small fraction, approximately 5%, of the initial energy. The energy absorbed by the structure and the energy emitted into the fluid are calculated for additional simulations of underwater pressure vessel implosions. For all cases investigated, there is minimal fracture in the collapse, the structure absorbs more than 80% of the initial energy of the system, and the released pressure pulse carries away less than 6% of the initial energy.

Initiation of Insensitive High Explosives Using Multiple Wave Interactions

NASA Astrophysics Data System (ADS)

Francois, Elizabeth; Burritt, Rosmary; Biss, Matt; Bowden, Patrick

2017-06-01

Insensitive High Explosives (IHEs) increase safety in many types of weapons. However, the safety comes at the cost of performance. Initiation of IHE requires large boosters and powerful detonators as well. Multipoint initiation is being utilized to exploit explosive wave interactions to create overdriven states, greatly facilitating the initiation of IHEs. This presentation will build from recent explosive experiments where the minimum spot size for single-point initiation in PBX 9502 was determined. Below this threshold, PBX 9502 could not be initiated. This was then expanded to three initiation points, which were smaller this threshold. Measurements of the velocity and pressure of the wave interactions were measured using Photon Doppler Velocimetry (PDV). Initiation was observed, and the resulting pressures at the double and triple points were found to be above the CJ state for PBX 9502. Based on these results, further tests were conducted to isolate and measure the longevity and pressure of this phenomenon using cut-back tests. All results will be presented and discussed.

Knee Osteoarthritis and Risk of Hypertension: A Longitudinal Cohort Study.

PubMed

Veronese, Nicola; Stubbs, Brendon; Solmi, Marco; Smith, Toby O; Noale, Marianna; Schofield, Patricia; Maggi, Stefania

2018-02-01

Although previous research has indicated an association between osteoarthritis (OA) and cardiovascular disease, it remains unclear whether people with OA are at greater risk of developing hypertension. The aim of this study was to answer this uncertainity. We used the data of the Osteoarthritis Initiative, an ongoing public and private longitudinal study including people at higher risk of OA or having knee OA. Knee OA was defined through radiological and clinical assessment. Incident hypertension was defined as a systolic blood pressure ≥140 mmHg and/or a diastolic value ≥90 mmHg. Multivariate Cox's regression analyses were constructed considering the presence of knee OA as the exposure and incident hypertension as the outcome during a 96-month follow-up interval. A total of 3558 people with normative blood pressure values at baseline were analyzed (1930 OA/1628 controls). Incidence of hypertension within the follow-up interval was significantly higher in people with knee OA than in those without (60/[1000 person-years] vs. 55/[1000 person-years]; p < 0.0001). After adjusting for 13 confounders, people with knee OA had a 13% higher chance of developing hypertension (hazard ratio = 1.13; 95% confidence interval: 1.01-1.26; p = 0.03). Propensity score analysis did not alter these conclusions. In conclusion, this is the first longitudinal data analysis to demonstrate that people with knee OA have a higher chance of developing hypertension than those without OA. Our data suggest that monitoring blood pressure and prescribing health promotion interventions may be warranted among people with OA to mitigate the potential onset and adverse consequences of hypertension.

Micromechanics of pressure-induced grain crushing in porous rocks

NASA Astrophysics Data System (ADS)

Davis, Daniel M.

1990-01-01

The hydrostatic compaction behavior of a suite of porous sandstones was investigated at confining pressures up to 600 MPa and constant pore pressures ranging up to 50 MPa. These five sandstones (Boise, Kayenta, St. Peter, Berea, and Weber) were selected because of their wide range of porosity (5-35%) and grain size (60-460 μm). We tested the law of effective stress for the porosity change as a function of pressure. Except for Weber sandstone (which has the lowest porosity and smallest grain size), the hydrostat of each sandstone shows an inflection point corresponding to a critical effective pressure beyond which an accelerated, irrecoverable compaction occurs. Our microstructural observations show that brittle grain crushing initiates at this critical pressure. We also observed distributed cleavage cracking in calcite and intensive kinking in mica. The critical pressures for grain crushing in our sandstones range from 75 to 380 MPa. In general, a sandstone with higher porosity and larger grain size has a critical pressure which is lower than that of a sandstone with lower porosity and smaller grain size. We formulate a Hertzian fracture model to analyze the micromechanics of grain crushing. Assuming that the solid grains have preexisting microcracks with dimensions which scale with grain size, we derive an expression for the critical pressure which depends on the porosity, grain size, and fracture toughness of the solid matrix. The theoretical prediction is in reasonable agreement with our experimental data as well as other data from soil and rock mechanics studies for which the critical pressures range over 3 orders of magnitude.

Undecompressed microbial populations from the deep sea.

PubMed Central

Jannasch, H J; Wirsen, C O; Taylor, C D

1976-01-01

Metabolic transformations of glutamate and Casamino Acids by natural microbial populations collected from deep waters (1,600 to 3,100 m) were studied in decompressed and undecompressed samples. Pressure-retaining sampling/incubation vessels and appropriate subsampling/incubation vessels and appropriate subsampling techniques permitted time course experiments. In all cases the metabolic activity in undecompressed samples was lower than it was when incubated at 1 atm. Surface water controls showed a reduced activity upon compression. The processes involving substrate incorporation into cell material were more pressure sensitive than was respiration. The low utilization of substrates, previously found by in situ incubations for up to 12 months, was confirmed and demonstrated to consist of an initial phase of activity, in the range of 5 to 60 times lower than the controls, followed by a stationary phase of virtually no substrate utilization. No barophilic growth response (higher rates at elevated pressure than at 1 atm) was recorded; all populations observed exhibition various degrees of barotolerance. Images PMID:791117

Jet plume injection and combustion system for internal combustion engines

DOEpatents

Oppenheim, A.K.; Maxson, J.A.; Hensinger, D.M.

1993-12-21

An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure. 24 figures.

Jet plume injection and combustion system for internal combustion engines

DOEpatents

Oppenheim, Antoni K.; Maxson, James A.; Hensinger, David M.

1993-01-01

An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.

Pain thresholds and tenderness in neck and head following acute whiplash injury: a prospective study.

PubMed

Kasch, H; Stengaard-Pedersen, K; Arendt-Nielsen, L; Staehelin Jensen, T

2001-04-01

OBJECTIVE OF THE INVESTIGATION: In a 6-month prospective study of 141 consecutive acute whiplash-injured participants, and 40 acute, ankle-injured controls, pain and tenderness in the neck/head, and at a distant control site, were measured. Muscle palpation and pressure algometry in five head/neck muscle-pairs were performed after 1 week and 1, 3 and 6 months after injury. Algometry was performed at a distant control site. Whiplash-injured patients had lowered pressure-pain-detection thresholds and higher palpation-score initially in the neck/head, but the groups were similar after 6 months, and the control site was not sensitized. Focal, but not generalized, sensitization to musculoskeletal structure is present until 3 months, but not 6 months, after whiplash injury, and probably does not play a major role in the development of late whiplash syndrome. Pressure algometry and palpation are useful clinical tools in the evaluation of neck and jaw pain in acute whiplash injury.

Foam relaxation in fractures and narrow channels

NASA Astrophysics Data System (ADS)

Lai, Ching-Yao; Rallabandi, Bhargav; Perazzo, Antonio; Stone, Howard A.

2017-11-01

Various applications, from foam manufacturing to hydraulic fracturing with foams, involve pressure-driven flow of foams in narrow channels. We report a combined experimental and theoretical study of this problem accounting for the compressible nature of the foam. In particular, in our experiments the foam is initially compressed in one channel and then upon flow into a second channel the compressed foam relaxes as it moves. A plug flow is observed in the tube and the pressure at the entrance of the tube is higher than the exit. We measure the volume collected at the exit of the tube, V, as a function of injection flow rate, tube length and diameter. Two scaling behaviors for V as a function of time are observed depending on whether foam compression is important or not. Our work may relate to foam fracturing, which saves water usage in hydraulic fracturing, more efficient enhanced oil recovery via foam injection, and various materials manufacturing processes involving pressure-driven flow foams.

Men pressured and forced into sexual experience.

PubMed

Struckman-Johnson, C; Struckman-Johnson, D

1994-02-01

A predominantly heterosexual sample of 204 college men were asked to report incidents of pressured or forced sexual touch or intercourse since age 16. About 34% indicated they had received coercive sexual contact: 24% from women, 4% from men, and 6% from both sexes. Contact involved only sexual touching for 12% and intercourse for 22%. Sexual contact was pressured in 88% of the 81 reported incidents by tactics of persuasion, intoxication, threat of love withdrawal, and bribery. In 12% of the incidents, sexual contact was forced through physical restraint, physical intimidation, threat of harm, or harm. Contact was initiated by an acquaintance or intimate in 77% of incidents. The negative emotional impact of male contact was rated significantly higher than the impact of female contact. Men with and without coercion experience did not differ, however, for scale scores on sexual esteem, depression, and preoccupation. Interviews with 10 subjects revealed complex reactions to coercive male and female contact, including doubts about one's sexuality, resentment of unexpected or forceful contact, and fear of telling others about the event.

[An investigation for standardized diagnosis and treatment of idiopathic normal-pressure hydrocephalus].

PubMed

Jiang, H J; Zhang, J M; Fu, W M; Zheng, Z; Luo, W; Zheng, Y X; Zhu, J M

2016-06-07

To investigate some important issues for diagnosis and treatment of idiopathic normal-pressure hydrocephalus (iNPH), such as standardized pre-operative assessment, initial pressure value of diverter pump, and pressure regulation during follow-up. Twenty six iNPH patients (21 males) who treated in Department of Neurosurgery of 2nd Affiliated Hospital of Zhejiang University School of Medicine from 2011 to 2015 were analyzed retrospectively. The average age was 60.5 year. The analysis focused on the treatment process of iNPH, initial pressure value of diverter pump, choice of diverter pump, and pressure regulation during follow-up. As a result, 24 cases (92.3%) had a good prognosis based on their imaging and clinical manifestations. Based on the literature and their clinical experiences, this department established a diagnosis and treatment procedure of iNPH and a pressure regulation procedure for the follow-up of iNPH. Moreover, it is proposed that choosing an anti-gravity diverter pump and making an initial pressure value 20 mmH2O less than pre-surgical cerebrospinal pressure may be beneficial for the prognosis. This standardized diagnosis and treatment procedure for iNPH is practical and effective.

May Measurement Month 2017: an analysis of blood pressure screening results worldwide.

PubMed

Beaney, Thomas; Schutte, Aletta E; Tomaszewski, Maciej; Ariti, Cono; Burrell, Louise M; Castillo, Rafael R; Charchar, Fadi J; Damasceno, Albertino; Kruger, Ruan; Lackland, Daniel T; Nilsson, Peter M; Prabhakaran, Dorairaj; Ramirez, Agustin J; Schlaich, Markus P; Wang, Jiguang; Weber, Michael A; Poulter, Neil R

2018-05-16

Increased blood pressure is the biggest contributor to the global burden of disease and mortality. Data suggest that less than half of the population with hypertension is aware of it. May Measurement Month was initiated to raise awareness of the importance of blood pressure and as a pragmatic interim solution to the shortfall in screening programmes. This cross-sectional survey included volunteer adults (≥18 years) who ideally had not had their blood pressures measured in the past year. Each participant had their blood pressure measured three times and received a a questionnaire about demographic, lifestyle, and environmental factors. The primary objective was to raise awareness of blood pressure, measured by number of countries involved, number of people screened, and number of people who have untreated or inadequately treated hypertension (defined as systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg, or both, or on the basis of receiving antihypertensive medication). Multiple imputation was used to estimate the mean of the second and third blood pressure readings if these were not recorded. Measures of association were analysed using linear mixed models. Data were collected from 1 201 570 individuals in 80 countries. After imputation, of the 1 128 635 individuals for whom a mean of the second and third readings was available, 393 924 (34·9%) individuals had hypertension. 153 905 (17·3%) of 888 616 individuals who were not receiving antihypertensive treatment were hypertensive, and 105 456 (46·3%) of the 227 721 individuals receiving treatment did not have controlled blood pressure. Significant differences in adjusted blood pressures and hypertension prevalence were apparent between regions. Adjusted blood pressure was higher in association with antihypertensive medication, diabetes, cerebrovascular disease, smoking, and alcohol consumption. Blood pressure was higher when measured on the right arm than on the left arm, and blood pressure was highest on Saturdays. Inexpensive global screening of blood pressure is achievable using volunteers and convenience sampling. Pending the set-up of systematic surveillance systems worldwide, MMM will be repeated annually to raise awareness of blood pressure. International Society of Hypertension, Centers for Disease Control and Prevention, Servier Pharmaceutical Co. Copyright © 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.

Resuscitation from severe hemorrhagic shock after traumatic brain injury using saline, shed blood, or a blood substitute.

PubMed

Gibson, Jeffrey B; Maxwell, Robert A; Schweitzer, John B; Fabian, Timothy C; Proctor, Kenneth G

2002-03-01

The original purpose of this study was to compare initial resuscitation of hemorrhagic hypotension after traumatic brain injury (TBI) with saline and shed blood. Based on those results, the protocol was modified and saline was compared to a blood substitute, diaspirin cross-linked hemoglobin (DCLHb). Two series of experiments were performed in anesthetized and mechanically ventilated (FiO2 = 0.4) pigs (35-45 kg). In Series 1, fluid percussion TBI (6-8 ATM) was followed by a 30% hemorrhage. At 120 min post-TBI, initial resuscitation consisted of either shed blood (n = 7) or a bolus of 3x shed blood volume as saline (n = 13). Saline supplements were then administered to all pigs to maintain a systolic arterial blood pressure (SAP) of >100 mmHg and a heart rate (HR) of <110 beats/min. In Series 2, TBI (4-5 ATM) was followed by a 35% hemorrhage. At 60 min post-TBI, initial resuscitation consisted of either 500 mL of DCLHb (n = 6) or 500 mL of saline (n = 5). This was followed by saline supplements to all pigs to maintain a SAP of >100 mmHg and a HR of <110 beats/min. In Series 1, most systemic markers of resuscitation (e.g., SAP, HR, cardiac output, filling pressures, lactate, etc.) were normalized, but there were 0/7 vs. 5/13 deaths within 5 h (P = 0.058) with blood vs. saline. At constant arterial O2 saturation (SaO2), mixed venous O2 saturation (SvO2), cerebral perfusion pressure (CPP), and cerebral venous O2 saturation (ScvO2) were all higher, intracranial pressure (ICP) was lower, and CO2 reactivity was preserved with blood vs. saline (all P < 0.05). In Series 2, SAP, ICP, CPP, and lactate were higher with DCLHb vs. saline (all P< 0.05). Cardiac output was lower even though filling pressure was markedly elevated with DCLHb vs. saline (both P< 0.05). Neither SvO2 nor cerebrovascular CO2 reactivity were improved, and ScvO2 was lower with DCLHb vs. saline (P < 0.05). All survived at least 72 h with neuropathologic changes that included sub-arachnoid hemorrhage, midline cerebellar necrosis, and diffuse axonal injury. These changes were similar with DCLHb vs. saline. Thus, whole blood was more effective than saline for resuscitation of TBI, whereas DCLHb was no more, and according to many variables, less effective than saline resuscitation. These experimental results are comparable to those in a recent multicenter trial using DCLHb for the treatment of severe traumatic shock. Further investigations in similar experimental models might provide some plausible explanations why DCLHb unexpectedly increased mortality in patients.

Circuit for detecting initial systole and dicrotic notch. [for monitoring arterial pressure

NASA Technical Reports Server (NTRS)

Gebben, V. D.; Webb, J. A., Jr. (Inventor)

1974-01-01

Circuitry is disclosed for processing an arterial pressure waveform to produce during any one cycle a pulse corresponding to the initial systole and a pulse corresponding to the dicrotic notch. In a first channel, an electrical analog of the arterial pressure waveform is filtered and then compared to the original waveform to produce an initial systole signal. In a second channel, the analog is differentiated, filtered, and fed through a gate controlled by pulses from the first channel to produce an electrical pulse corresponding to the dicrotic notch.

Simulated performance of biomass gasification based combined power and refrigeration plant for community scale application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chattopadhyay, S., E-mail: suman.mech09@gmail.com; Mondal, P., E-mail: mondal.pradip87@gmail.com; Ghosh, S., E-mail: sudipghosh.becollege@gmail.com

Thermal performance analysis and sizing of a biomass gasification based combined power and refrigeration plant (CPR) is reported in this study. The plant is capable of producing 100 kWe of electrical output while simultaneously producing a refrigeration effect, varying from 28-68 ton of refrigeration (TR). The topping gas turbine cycle is an indirectly heated all-air cycle. A combustor heat exchanger duplex (CHX) unit burns producer gas and transfer heat to air. This arrangement avoids complex gas cleaning requirements for the biomass-derived producer gas. The exhaust air of the topping GT is utilized to run a bottoming ammonia absorption refrigeration (AAR)more » cycle via a heat recovery steam generator (HRSG), steam produced in the HRSG supplying heat to the generator of the refrigeration cycle. Effects of major operating parameters like topping cycle pressure ratio (r{sub p}) and turbine inlet temperature (TIT) on the energetic performance of the plant are studied. Energetic performance of the plant is evaluated via energy efficiency, required biomass consumption and fuel energy savings ratio (FESR). The FESR calculation method is significant for indicating the savings in fuel of a combined power and process heat plant instead of separate plants for power and process heat. The study reveals that, topping cycle attains maximum power efficiency of 30%in pressure ratio range of 8-10. Up to a certain value of pressure ratio the required air flow rate through the GT unit decreases with increase in pressure ratio and then increases with further increase in pressure ratio. The capacity of refrigeration of the AAR unit initially decreases up to a certain value of topping GT cycle pressure ratio and then increases with further increase in pressure ratio. The FESR is found to be maximized at a pressure ratio of 9 (when TIT=1100°C), the maximum value being 53%. The FESR is higher for higher TIT. The heat exchanger sizing is also influenced by the topping cycle pressure ratio and GT-TIT.« less

Optimization of pressure settings during adaptive servo-ventilation support using real-time heart rate variability assessment: initial case report.

PubMed

Imamura, Teruhiko; Nitta, Daisuke; Kinugawa, Koichiro

2017-01-05

Adaptive servo-ventilation (ASV) therapy is a recent non-invasive positive pressure ventilation therapy that was developed for patients with heart failure (HF) refractory to optimal medical therapy. However, it is likely that ASV therapy at relatively higher pressure setting worsens some of the patients' prognosis compared with optimal medical therapy. Therefore, identification of optimal pressure settings of ASV therapy is warranted. We present the case of a 42-year-old male with HF, which was caused by dilated cardiomyopathy, who was admitted to our institution for evaluating his eligibility for heart transplantation. To identify the optimal pressure setting [peak end-expiratory pressure (PEEP) ramp test], we performed an ASV support test, during which the PEEP settings were set at levels ranging from 4 to 8 mmHg, and a heart rate variability (HRV) analysis using the MemCalc power spectral density method. Clinical parameters varied dramatically during the PEEP ramp test. Over incremental PEEP levels, pulmonary capillary wedge pressure, cardiac index and high-frequency level (reflecting parasympathetic activity) decreased; however, the low-frequency level increased along with increase in plasma noradrenaline concentrations. An inappropriately high PEEP setting may stimulate sympathetic nerve activity accompanied by decreased cardiac output. This was the first report on the PEEP ramp test during ASV therapy. Further research is warranted to determine whether use of optimal pressure settings using HRV analyses may improve the long-term prognosis of such patients.

High pressure processing's potential to inactivate norovirus and other fooodborne viruses

USDA-ARS?s Scientific Manuscript database

High pressure processing (HPP) can inactivate human norovirus. However, all viruses are not equally susceptible to HPP. Pressure treatment parameters such as required pressure levels, initial pressurization temperatures, and pressurization times substantially affect inactivation. How food matrix ...

Impact of different nasal masks on CPAP therapy for obstructive sleep apnea: a randomized comparative trial.

PubMed

Neuzeret, Pierre-Charles; Morin, Laurent

2017-11-01

Patient interface is important for the success of continuous positive airway pressure (CPAP), but few trials have examined the influence of mask choice on CPAP adherence. To compare the impact of different nasal masks on CPAP in patients with newly-diagnosed obstructive sleep apnea (OSA). OSA patients were randomized in a 2:3 ratio to receive CPAP via different first-line nasal masks: ResMed Mirage FX® (MFX) or control mask (Fisher & Paykel Zest ® , HC407 ® or Philips EasyLife ® ). Mask acceptance, CPAP compliance and Home Care Provider (HCP) interventions were compared between groups after 3 months of CPAP therapy using modified intent-to-treat (mITT; after exclusion of patients with mouth leaks during CPAP initiation) and on-treatment (OT; CPAP adherent) analyses. Of 285 randomized patients, 90 requiring a full-face mask were excluded, leaving 195 and 151 in the mITT and OT analyses, respectively. Mask acceptance rate was higher in the MFX versus control group (mITT: 79% vs 68%, P = 0.067; OT: 90% vs 76%, P = 0.022). CPAP compliance was higher (5.9 ± 1.8 vs 5.1 ± 1.6 h/night, P = 0.011) and nasal mask issue-related HCP visits lower (3% vs 17%, P = 0.006) in the MFX group. Nasal mask failures due to mask discomfort (5% vs 1%) or unintentional leakage (5% vs 0%) were higher in control vs MFX group. Mask acceptance was significantly associated with fewer mask leaks (P = 0.002) and higher pressure therapy (P = 0.042). This study highlights differences between nasal masks for CPAP delivery and shows that initial mask selection can influence adherence and healthcare utilization during CPAP. © 2016 ResMed Germany Inc. The Clinical Respiratory Journal published by John Wiley & Sons Ltd.

Relevance of impacter shape to nonvisible damage and residual tensile strength of a thick graphite/epoxy laminate

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1990-01-01

A study was made to determine the relevance of impacter shape to nonvisible damage and tensile residual strength of a 36 mm (1.4 in.) thick graphite/epoxy motor case. The shapes of the impacters were as follows: 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.) diameter hemispheres, a sharp corner, and a 6.3 mm (0.25 in.) diameter bolt-like rod. The investigation revealed that damage initiated when the contact pressure exceeded a critical level. However, the damage was not visible on the surface until an even higher pressure was exceeded. The damage on the surface consisted of a crater shaped like the impacter, and the damage below the surface consisted of broken fibers. The impact energy to initiate damage or cause visible damage on the surface increased approximately with impacter diameter to the third power. The reduction in strength for nonvisible damage increased with increasing diameter, 9 and 30 percent for the 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.) diameter hemispheres, respectively. The corner impacter made visible damage on the surface for even the smallest impact energy. The rod impacter acted like a punch and sliced through the composite. Even so, the critical level of pressure to initiate damage was the same for the rod and hemispherical impacters. Factors of safety for nonvisible damage increased with increasing kinetic energy of impact. The effects of impacter shape on impact force, damage size, damage visibility, and residual tensile strength were predicted quite well assuming Hertzian contact and using maximum stress criteria and a surface crack analysis.

A passive satellite deorbiting strategy for medium earth orbit using solar radiation pressure and the J2 effect

NASA Astrophysics Data System (ADS)

Lücking, Charlotte; Colombo, Camilla; McInnes, Colin R.

2012-08-01

The growing population of space debris poses a serious risk to the future of space flight. To effectively manage the increase of debris in orbit, end-of life disposal has become a key requirement for future missions. This poses a challenge for Medium Earth Orbit (MEO) spacecraft which require a large Δv to re-enter the atmosphere or reach the geostationary graveyard orbit. This paper further explores a passive strategy based on the joint effects of solar radiation pressure and the Earth's oblateness acting on a high area-to-mass-ratio object. The concept was previously presented as an analytical planar model. This paper uses a full 3D model to validate the analytical results numerically for equatorial circular orbits first, then investigating higher inclinations. It is shown that for higher inclinations the initial position of the Sun and right ascension of the ascending node become increasingly important. A region of very low required area-to-mass-ratio is identified in the parameter space of semi-major axis and inclination which occurs for altitudes below 10,000 km.

In-shoe plantar pressure distribution and lower extremity muscle activity patterns of backward compared to forward running on a treadmill.

PubMed

Sterzing, Thorsten; Frommhold, Clivia; Rosenbaum, Dieter

2016-05-01

Backward locomotion in humans occurs during leisure, rehabilitation, and competitive sports. Little is known about its general biomechanical characteristics and how it affects lower extremity loading as well as muscle coordination. Thus, the purpose of this research was to analyze in-shoe plantar pressure patterns and lower extremity muscle activity patterns for backward compared to forward running. On a treadmill, nineteen runners performed forward running at their individually preferred speed, followed by backward running at 70% of their self-selected forward speed. In-shoe plantar pressures of nine foot regions and muscular activity of nine lower extremity muscles were recorded simultaneously over a one-minute interval. Backward and forward running variables were averaged over the accumulated steps and compared with Wilcoxon-signed rank tests (p<.05). For backward compared to forward running, in-shoe plantar pressure distribution showed a load increase under metatarsal heads I and II, as well as under the medial midfoot. This was indicated by higher maximum forces and peak pressures, and by longer contact times. Muscle activity showed significantly higher mean amplitudes during backward running in the semitendinosus, rectus femoris, vastus lateralis, and gluteus medius during stance, and in the rectus femoris during swing phase, while significantly lower mean amplitudes were observed in the tibialis anterior during swing phase. Observations indicate plantar foot loading and muscle activity characteristics that are specific for the running direction. Thus, backward running may be used on purpose for certain rehabilitation tasks, aiming to strengthen respective lower extremity muscles. Furthermore, the findings are relevant for sport specific backward locomotion training. Finally, results provide an initial baseline for innovative athletic footwear development aiming to increase comfort and performance during backward running. Copyright © 2016 Elsevier B.V. All rights reserved.

Impact of process conditions on the density and durability of wheat, oat, canola, and barley straw briquettes

DOE PAGES

Tumuluru, J. S.; Tabil, L. G.; Song, Y.; ...

2014-10-01

The present study is to understand the impact of process conditions on the quality attributes of wheat oat, barley, and canola straw briquettes. Analysis of variance indicated that briquette moisture content and initial density immediately after compaction and final density after 2 weeks of storage are strong functions of feedstock moisture content and compression pressure, whereas durability rating is influenced by die temperature and feedstock moisture content. Briquettes produced at a low feedstock moisture content of 9 % (w.b.) yielded maximum densities >700 kg/m3 for wheat, oat, canola, and barley straws. Lower feedstock moisture content of <10 % (w.b.) andmore » higher die temperatures >110 °C and compression pressure >10 MPa minimized the briquette moisture content and maximized densities and durability rating based on surface plots observations. Optimal process conditions indicated that a low feedstock moisture content of about 9 % (w.b.), high die temperature of 120–130 °C, medium-to-large hammer mill screen sizes of about 24 to 31.75 mm, and low to high compression pressures of 7.5 to 12.5 MPa minimized briquette moisture content to <8 % (w.b.) and maximized density to >700 kg/m3. Durability rating >90 % is achievable at higher die temperatures of >123 °C, lower to medium feedstock moisture contents of 9 to 12 % (w.b.), low to high compression pressures of 7.5 to 12.5 MPa, and large hammer mill screen size of 31.75 mm, except for canola where a lower compression pressure of 7.5 to 8.5 MPa and a smaller hammer mill screen size of 19 mm for oat maximized the durability rating values.« less

Methyl mercury, but not inorganic mercury, associated with higher blood pressure during pregnancy.

PubMed

Wells, Ellen M; Herbstman, Julie B; Lin, Yu Hong; Hibbeln, Joseph R; Halden, Rolf U; Witter, Frank R; Goldman, Lynn R

2017-04-01

Prior studies addressing associations between mercury and blood pressure have produced inconsistent findings; some of this may result from measuring total instead of speciated mercury. This cross-sectional study of 263 pregnant women assessed total mercury, speciated mercury, selenium, and n-3 polyunsaturated fatty acids in umbilical cord blood and blood pressure during labor and delivery. Models with a) total mercury or b) methyl and inorganic mercury were evaluated. Regression models adjusted for maternal age, race/ethnicity, prepregnancy body mass index, neighborhood income, parity, smoking, n-3 fatty acids and selenium. Geometric mean total, methyl, and inorganic mercury concentrations were 1.40µg/L (95% confidence interval: 1.29, 1.52); 0.95µg/L (0.84, 1.07); and 0.13µg/L (0.10, 0.17), respectively. Elevated systolic BP, diastolic BP, and pulse pressure were found, respectively, in 11.4%, 6.8%, and 19.8% of mothers. In adjusted multivariable models, a one-tertile increase of methyl mercury was associated with 2.83mmHg (0.17, 5.50) higher systolic blood pressure and 2.99mmHg (0.91, 5.08) higher pulse pressure. In the same models, an increase of one tertile of inorganic mercury was associated with -1.18mmHg (-3.72, 1.35) lower systolic blood pressure and -2.51mmHg (-4.49, -0.53) lower pulse pressure. No associations were observed with diastolic pressure. There was a non-significant trend of higher total mercury with higher systolic blood pressure. We observed a significant association of higher methyl mercury with higher systolic and pulse pressure, yet higher inorganic mercury was significantly associated with lower pulse pressure. These results should be confirmed with larger, longitudinal studies. Copyright © 2017 Elsevier Inc. All rights reserved.

Does increasing pressure always accelerate the condensed material decay initiated through bimolecular reactions? A case of the thermal decomposition of TKX-50 at high pressures.

PubMed

Lu, Zhipeng; Zeng, Qun; Xue, Xianggui; Zhang, Zengming; Nie, Fude; Zhang, Chaoyang

2017-08-30

Performances and behaviors under high temperature-high pressure conditions are fundamentals for many materials. We study in the present work the pressure effect on the thermal decomposition of a new energetic ionic salt (EIS), TKX-50, by confining samples in a diamond anvil cell, using Raman spectroscopy measurements and ab initio simulations. As a result, we find a quadratic increase in decomposition temperature (T d ) of TKX-50 with increasing pressure (P) (T d = 6.28P 2 + 12.94P + 493.33, T d and P in K and GPa, respectively, and R 2 = 0.995) and the decomposition under various pressures initiated by an intermolecular H-transfer reaction (a bimolecular reaction). Surprisingly, this finding is contrary to a general observation about the pressure effect on the decomposition of common energetic materials (EMs) composed of neutral molecules: increasing pressure will impede the decomposition if it starts from a bimolecular reaction. Our results also demonstrate that increasing pressure impedes the H-transfer via the enhanced long-range electrostatic repulsion of H +δ H +δ of neighboring NH 3 OH + , with blue shifts of the intermolecular H-bonds. And the subsequent decomposition of the H-transferred intermediates is also suppressed, because the decomposition proceeds from a bimolecular reaction to a unimolecular one, which is generally prevented by compression. These two factors are the basic root for which the decomposition retarded with increasing pressure of TKX-50. Therefore, our finding breaks through the previously proposed concept that, for the condensed materials, increasing pressure will accelerate the thermal decomposition initiated by bimolecular reactions, and reveals a distinct mechanism of the pressure effect on thermal decomposition. That is to say, increasing pressure does not always promote the condensed material decay initiated through bimolecular reactions. Moreover, such a mechanism may be feasible to other EISs due to the similar intermolecular interactions.

Investigations of initial airtightness after non-anatomic resection of lung parenchyma using a thulium-doped laser with different optical fibres.

PubMed

Kirschbaum, Andreas; Höchsmann, N; Steinfeldt, T; Seyfer, P; Pehl, A; Bartsch, D K; Palade, E

2016-08-01

Lung metastases in healthy patients should be removed non-anatomically whenever possible. This can be done with a laser. Lung parenchyma can be cut very well, because of its high energy absorption at a wavelength of 1940 nm. A coagulation layer is created on the resected surface. It is not clear, whether this surface also needs to be sutured to ensure that it remains airtight even at higher ventilation pressures. It would be helpful, if suturing could be avoided, because the lung can become too puckered, especially with multiple resections, resulting in considerable restriction. We carried out our experiments on isolated and ventilated paracardiac lung lobes of pigs. Non-anatomic resection was carried out reproducibly using three different thulium laser fibres (230, 365 and 600 μm) at two different laser power levels (10 W, 30 W) and three different resection depths (0.5, 1.0 and 2.0 cm). Initial airtightness was investigated while ventilating at normal frequency. We also investigated the bursting pressures of the resected areas by increasing the inspiratory pressure. When 230- and 365-μm fibres were used with a power of 10 W, 70 % of samples were initially airtight up to a resection depth of 1 cm. This rate fell at depths of up to 2 cm. All resected surfaces remained airtight during ventilation when 600-μm fibres were used at both laser power levels (10 and 30 W). The bursting pressures achieved with 600-μm fibres were higher than with the other fibres used: 0.5 cm, 41.6 ± 3.2 mbar; 1 cm, 38.2 ± 2.5 mbar; 2 cm, 33.7 ± 4.8 mbar. As laser power and thickness of laser fibre increased, so the coagulation zone became thicker. With a 600-μm fibre, it measured 145.0 ± 8.2 μm with 10 W power and 315.5 ± 6.4 μm with 30 W power. Closure with sutures after non-anatomic resection of lung parenchyma is not necessary when a thulium laser is used provided a 600-μm fibre and adequate laser power (30 W) are employed. At deeper resection levels, the risk of cutting small segmental bronchi is considerably increased. They must always be closed with sutures.

Anticipatory Postural Control of Stability during Gait Initiation Over Obstacles of Different Height and Distance Made Under Reaction-Time and Self-Initiated Instructions.

PubMed

Yiou, Eric; Artico, Romain; Teyssedre, Claudine A; Labaune, Ombeline; Fourcade, Paul

2016-01-01

Despite the abundant literature on obstacle crossing in humans, the question of how the central nervous system (CNS) controls postural stability during gait initiation with the goal to clear an obstacle remains unclear. Stabilizing features of gait initiation include anticipatory postural adjustments (APAs) and lateral swing foot placement. To answer the above question, 14 participants initiated gait as fast as possible in three conditions of obstacle height, three conditions of obstacle distance and one obstacle-free (control) condition. Each of these conditions was performed with two levels of temporal pressure: reaction-time (high-pressure) and self-initiated (low-pressure) movements. A mechanical model of the body falling laterally under the influence of gravity and submitted to an elastic restoring force is proposed to assess the effect of initial (foot-off) center-of-mass position and velocity (or "initial center-of-mass set") on the stability at foot-contact. Results showed that the anticipatory peak of mediolateral (ML) center-of-pressure shift, the initial ML center-of-mass velocity and the duration of the swing phase, of gait initiation increased with obstacle height, but not with obstacle distance. These results suggest that ML APAs are scaled with swing duration in order to maintain an equivalent stability across experimental conditions. This statement is strengthened by the results obtained with the mechanical model, which showed how stability would be degraded if there was no adaptation of the initial center-of-mass set to swing duration. The anteroposterior (AP) component of APAs varied also according to obstacle height and distance, but in an opposite way to the ML component. Indeed, results showed that the anticipatory peak of backward center-of-pressure shift and the initial forward center-of-mass set decreased with obstacle height, probably in order to limit the risk to trip over the obstacle, while the forward center-of-mass velocity at foot-off increased with obstacle distance, allowing a further step to be taken. These effects of obstacle height and distance were globally similar under low and high-temporal pressure. Collectively, these findings imply that the CNS is able to predict the potential instability elicited by the obstacle clearance and that it scales the spatiotemporal parameters of APAs accordingly.

Anticipatory Postural Control of Stability during Gait Initiation Over Obstacles of Different Height and Distance Made Under Reaction-Time and Self-Initiated Instructions

PubMed Central

Yiou, Eric; Artico, Romain; Teyssedre, Claudine A.; Labaune, Ombeline; Fourcade, Paul

2016-01-01

Despite the abundant literature on obstacle crossing in humans, the question of how the central nervous system (CNS) controls postural stability during gait initiation with the goal to clear an obstacle remains unclear. Stabilizing features of gait initiation include anticipatory postural adjustments (APAs) and lateral swing foot placement. To answer the above question, 14 participants initiated gait as fast as possible in three conditions of obstacle height, three conditions of obstacle distance and one obstacle-free (control) condition. Each of these conditions was performed with two levels of temporal pressure: reaction-time (high-pressure) and self-initiated (low-pressure) movements. A mechanical model of the body falling laterally under the influence of gravity and submitted to an elastic restoring force is proposed to assess the effect of initial (foot-off) center-of-mass position and velocity (or “initial center-of-mass set”) on the stability at foot-contact. Results showed that the anticipatory peak of mediolateral (ML) center-of-pressure shift, the initial ML center-of-mass velocity and the duration of the swing phase, of gait initiation increased with obstacle height, but not with obstacle distance. These results suggest that ML APAs are scaled with swing duration in order to maintain an equivalent stability across experimental conditions. This statement is strengthened by the results obtained with the mechanical model, which showed how stability would be degraded if there was no adaptation of the initial center-of-mass set to swing duration. The anteroposterior (AP) component of APAs varied also according to obstacle height and distance, but in an opposite way to the ML component. Indeed, results showed that the anticipatory peak of backward center-of-pressure shift and the initial forward center-of-mass set decreased with obstacle height, probably in order to limit the risk to trip over the obstacle, while the forward center-of-mass velocity at foot-off increased with obstacle distance, allowing a further step to be taken. These effects of obstacle height and distance were globally similar under low and high-temporal pressure. Collectively, these findings imply that the CNS is able to predict the potential instability elicited by the obstacle clearance and that it scales the spatiotemporal parameters of APAs accordingly. PMID:27656138

Role of rpoS in the Development of Cell Envelope Resilience and Pressure Resistance in Stationary-Phase Escherichia coli▿

PubMed Central

Charoenwong, Duangkamol; Andrews, Simon; Mackey, Bernard

2011-01-01

This work investigated the role of rpoS in the development of increased cell envelope resilience and enhanced pressure resistance in stationary-phase cells of Escherichia coli. Loss of both colony-forming ability and membrane integrity, measured as uptake of propidium iodide (PI), occurred at lower pressures in E. coli BW3709 (rpoS) than in the parental strain (BW2952). The rpoS mutant also released much higher concentrations of protein under pressure than the parent. We propose that RpoS-regulated functions are responsible for the increase in membrane resilience as cells enter stationary phase and that this plays a major role in the development of pressure resistance. Strains from the Keio collection with mutations in two RpoS-regulated genes, cfa (cyclopropane fatty acyl phospholipid synthase) and osmB (outer membrane lipoprotein), were significantly more pressure sensitive and took up more PI than the parent strain, with cfa having the greatest effect. Mutations in the bolA morphogene and other RpoS-regulated lipoprotein genes (osmC, osmE, osmY, and ybaY) had no effect on pressure resistance. The cytoplasmic membranes of the rpoS mutant failed to reseal after pressure treatment, and strains with mutations in osmB and nlpI (new lipoprotein) were also somewhat impaired in the ability to reseal their membranes. The cfa mutant, though pressure sensitive, was unaffected in membrane resealing, implying that the initial transient permeabilization event is critical for loss of viability rather than the failure to reseal. The enhanced pressure sensitivity of polA, recA, and xthA mutants suggested that DNA may be a target of oxidative stress in pressure-treated cells. PMID:21705547

Role of rpoS in the development of cell envelope resilience and pressure resistance in stationary-phase Escherichia coli.

PubMed

Charoenwong, Duangkamol; Andrews, Simon; Mackey, Bernard

2011-08-01

This work investigated the role of rpoS in the development of increased cell envelope resilience and enhanced pressure resistance in stationary-phase cells of Escherichia coli. Loss of both colony-forming ability and membrane integrity, measured as uptake of propidium iodide (PI), occurred at lower pressures in E. coli BW3709 (rpoS) than in the parental strain (BW2952). The rpoS mutant also released much higher concentrations of protein under pressure than the parent. We propose that RpoS-regulated functions are responsible for the increase in membrane resilience as cells enter stationary phase and that this plays a major role in the development of pressure resistance. Strains from the Keio collection with mutations in two RpoS-regulated genes, cfa (cyclopropane fatty acyl phospholipid synthase) and osmB (outer membrane lipoprotein), were significantly more pressure sensitive and took up more PI than the parent strain, with cfa having the greatest effect. Mutations in the bolA morphogene and other RpoS-regulated lipoprotein genes (osmC, osmE, osmY, and ybaY) had no effect on pressure resistance. The cytoplasmic membranes of the rpoS mutant failed to reseal after pressure treatment, and strains with mutations in osmB and nlpI (new lipoprotein) were also somewhat impaired in the ability to reseal their membranes. The cfa mutant, though pressure sensitive, was unaffected in membrane resealing, implying that the initial transient permeabilization event is critical for loss of viability rather than the failure to reseal. The enhanced pressure sensitivity of polA, recA, and xthA mutants suggested that DNA may be a target of oxidative stress in pressure-treated cells.

Frequency of respiratory deterioration after immunisation in preterm infants.

PubMed

Hacking, Douglas F; Davis, Peter G; Wong, Ester; Wheeler, Kevin; McVernon, Jodie

2010-12-01

To determine the relationship between the initiation of respiratory support and the first routine immunisation of neonates at 2 months of age during primary hospitalisation. An historical cohort study design was used to study the neonatal factors associated with the initiation of respiratory support within 7 days of immunisation in a cohort of 7629 preterm and term infants admitted to the Neonatal Unit of the Royal Women's Hospital between 2001 and 2008. The 411 infants who received their first immunisations in hospital were both very preterm and of extremely low birth weight (ELBW, below 1000 g). Twenty-two infants experienced post-immunisation apnoea of sufficient severity to warrant the initiation of either intermittent positive pressure ventilation (two cases) or continuous positive airway pressure (20 cases). Infants exhibiting a respiratory deterioration following immunisation had a higher incidence of previous septicaemia (Odds ratio 2.5, 95% confidence interval 1.0, 6.1; P = 0.04) and received CPAP for a longer period prior to vaccination (P = 0.03). Apnoea following immunisation may be an aetiological factor in the requirement of respiratory support in a small number of preterm, ELBW infants particularly those with significant lung disease and those who have previously experienced septicaemia. © 2010 The Authors. Journal of Paediatrics and Child Health © 2010 Paediatrics and Child Health Division (Royal Australasian College of Physicians).

Pressure response of three-dimensional cyanide-bridged bimetallic magnets.

PubMed

Ohba, Masaaki; Kaneko, Wakako; Kitagawa, Susumu; Maeda, Takuho; Mito, Masaki

2008-04-02

Effects of pressure on the structures and magnetic properties of three types of 3-D cyanide-bridged bimetallic coordination polymer magnets, MnIICrIII ferrimagnet [Mn(en)]3[Cr(CN)6]2.4H2O (1; en = ethylenediamine), NiIICrIII ferromagnet [Ni(dipn)]3[Cr(CN)6]2.3H2O (2; dipn = N,N-di(3-aminopropyl)amine), and NiIIFeIII ferromagnet [Ni(dipn)]2[Ni(dipn)(H2O)][Fe(CN)6]2.11H2O (3), were systematically examined under hydrostatic pressure up to 19.8 GPa using a piston-cylinder-type pressure cell and a diamond anvil cell. The ferrimagnet 1 showed the reversible crystalline-to-amorphous-like phase change, and the magnetic phase transition temperature (TC) was reversibly changed from 69 K at 0 GPa to 126 K at 4.7 GPa. At higher pressure, the net magnetization was suppressed with increasing pressure, and the magnetic state at 19.8 GPa was assumed to be paramagnetic. The initial ferrimagnetic phase of 1 was not recovered after releasing the pressure from 19.8 GPa. The magnetic phase of 2 was reversibly converted between ferromagnetic and paramagnetic-like phase in the range 0

Water movement in glass bead porous media: 1. Experiments of capillary rise and hysteresis

NASA Astrophysics Data System (ADS)

Lu, T. X.; Biggar, J. W.; Nielsen, D. R.

1994-12-01

Experimental observations of capillary rise and hysteresis of water or ethanol in glass beads are presented to improve our understanding of those physical processes in porous media. The results provide evidence that capillary rise into porous media cannot be fully explained by a model of cylinders. They further demonstrate that the "Ink bottle" model does not provide an adequate explanation of hysteresis. Glass beads serving as a model for ideal soil are enclosed in a rectangular glass chamber model. A TV camera associated with a microscope was used to record the processes of capillary rise and drainage. It is clearly shown during capillary rise that the fluid exhibits a "jump" behavior at the neck of the pores in an initially dry profile or at the bottom of the water film in an initially wet profile. Under an initially dry condition, the jump initiates at the particle with smallest diameter. The jump process continues to higher elevations until at equilibrium the surface tensile force is balanced by the hydrostatic force. The wetting front at that time is readily observed as flat and saturated. Under an initially wet condition, capillary rise occurs as a water film thickening process associated with the jump process. Trapped air behind the wetting front renders the wetting front irregular and unsaturated. The capillary rise into an initially wet porous medium can be higher than that into an initially dry profile. During the drying process, large surface areas associated with the gas-liquid interface develop, allowing the porous medium to retain more water than during the wetting process at the same pressure. That mechanism explains better the hysteresis phenomenon in porous media in contrast to other mechanisms that now prevail.

Investigation of heavy current discharges with high initial gas density

NASA Astrophysics Data System (ADS)

Budin, A.; Bogomaz, A.; Kolikov, V.; Kuprin, A.; Leontiev, V.; Rutberg, Ph.; Shirokov, N.

1996-05-01

Piezoelectric pressure transducers, with noise immunity and time resolution of 0,5 μs were used to measure pulse pressures of 430 MPa along the axis of an electrical discharge channel. Initial concentration of He was 2,7ṡ1021cm-3, dI/dt=6ṡ1011 A/s, and Imax=560 kA. Shock waves with amplitudes exceeding the pressure along the axis, were detected by a pressure transducer on the wall of the discharge chamber. Typical shock velocities were 2ṡ4 km/s. Average pressure measurements along the discharge axis at different radii were used to estimate the current density distribution along the canal radius. The presence of the shock waves, promoting the additional hydrogen heating in the discharge chamber, has been registered during the discharge in hydrogen for Imax˜1 MA and an initial concentration of 1021cm-3.

[Impact of metabolic syndrome in the control of blood pressure and dyslipemia].

PubMed

Rodilla, Enrique; García, Luis; Merino, Consolación; Costa, José A; González, Carmen; Pascual, José M

2004-11-06

The objective of the study was to assess the influence of metabolic syndrome (MS) in the control of blood pressure (BP) and dyslipemia. A cross sectional study was performed with 1,320 (634 M and 686 F), 40.1 (13.3) years-old, BMI 29.8 (4.7) hypertensive non-diabetic patients. MS was diagnosed according to NCEP-ATP-III guidelines. Blood pressure control goal was BP < 140/90 mmHg. Coronary risk (CR) was calculated according to Framingham (low < 10%, intermediate 10-20% and high > 20% at 10 years). Goals of C-LDL levels were those of NCEP-ATP-III. 461 (35%) patients had MS and the remaining 859 became controls. Patients with MS had higher initial levels of hypertension and were receiving more antihypertensive drugs: 2.1 [1.3] vs. 1.7 [1.3]; p < 0.001), yet the average systolic and diastolic BP achieved and the degree of control was similar in both groups 53% vs. 52%; (p = ns). Patients with MS had higher CR at ten years than controls (10.7 [8.3] vs. 7.9 [6.8], p < 0.001) but achieved the C-LDL goals at fewer proportions than controls (57% vs. 74%; p < 0.001). In a regression analysis, patients with MS had 26% less probabilities of achieving both goals (p < 0.001). Hypertensive patients with MS have higher CR, and need more antihypertensive drugs to achieve the same BP goals. Yet it is more difficult for them to achieve LDL cholesterol goals. Patients with MS remain a target for cardiovascular prevention.

Relationship between inter-arm blood pressure difference and severity of coronary atherosclerosis.

PubMed

Park, Se-Jun; Son, Jung-Woo; Park, Sang-Min; Choi, Hyun-Hee; Hong, Kyung-Soon

2017-08-01

A greater inter-arm blood pressure difference (IABPD) is associated with atherosclerosis, but its association with coronary artery disease is unknown. We investigated the relationship between IABPD and coronary atherosclerosis. We retrospectively reviewed blood pressure (BP) data that was measured simultaneously in both arms of patients who underwent initial coronary angiography. Coronary atherosclerosis was assessed using the Gensini score, based on quantitative coronary angiography findings. To adjust for the effect of baseline BP, the percentages of systolic IABPD to higher mean BP (cIABPD sys ), diastolic IABPD to higher mean BP (cIABPD dia ), and mean IABPD to higher mean BP (cIABPD mean ) were calculated as BP-adjusted IABPDs. We examined the records of 816 patients (516 males, mean age: 65.5 ± 11.8 years). The mean Gensini score was 33.4 ± 30.4, and the median was 25. All cIAPBDs had positive correlations with the Gensini score (cIABPD sys : r = 0.208, p < 0.001; cIABPD dia : r = 0.123, p < 0.001; cIABPD mean : r = 0.120, p = 0.001). Multiple regression analysis indicated that cIABPD sys was associated with the Gensini score, independently of age, gender, smoking, diabetes, hypertension and dyslipidemia (B = 0.031, p < 0.001). The BP-adjusted IABPD parameters are related to the severity of coronary artery disease. Further studies should investigate the use of the IABPD to improve management of coronary atherosclerosis. Copyright © 2017. Published by Elsevier B.V.

Shape of initial portion of boundary of supersonic axisymmetric free jets at large jet pressure ratios

NASA Technical Reports Server (NTRS)

Love, Eugene S; Lee, Louise P

1958-01-01

Calculations have been made of the initial portion of the boundary of axisymmetric free jets exhausting at large pressure ratios from a conically divergent nozzle having a jet exit Mach number of 2.5 and a semidivergence angle of 15 degrees. The results of the calculations indicate the size and shape of the jet to be expected at large pressure ratios, the effects of ratio of specific heats, and the large initial inclinations of the boundary that are likely to be encountered by hypersonic vehicles at high altitude.

Flat-plate solar array project. Task 1: Silicon material. Investigation of the hydrochlorination of SiC14

NASA Technical Reports Server (NTRS)

Mui, J. Y. P.

1982-01-01

A two inch diameter stainless steel reactor was designed and built to operate at pressures up to 500 psig for the experimental studies on the hydrochlorination of SiCl4 and metallurgical grade (m.g.) silicon metal to SiHCl3. In order to clearly see the effect of pressure, the experiments were carried out at low reactor pressures of 73 psig and 150 psig, respectively. A large pressure effect on the hydrochlorination reaction was observed between the results of the low pressure experiments and the results of the high pressure experiments. In general, higher pressure produces a higher conversion of SiHCl3, but at a lower reaction rate. The effect of temperature on the reaction rate was studied at 73 psig. Higher reaction temperature gave a higher conversion and a higher reaction rate. Samples of the materials used to construct the hydrochlorination reactor were prepared for corrosion tests.

Reconstruction of initial pressure from limited view photoacoustic images using deep learning

NASA Astrophysics Data System (ADS)

Waibel, Dominik; Gröhl, Janek; Isensee, Fabian; Kirchner, Thomas; Maier-Hein, Klaus; Maier-Hein, Lena

2018-02-01

Quantification of tissue properties with photoacoustic (PA) imaging typically requires a highly accurate representation of the initial pressure distribution in tissue. Almost all PA scanners reconstruct the PA image only from a partial scan of the emitted sound waves. Especially handheld devices, which have become increasingly popular due to their versatility and ease of use, only provide limited view data because of their geometry. Owing to such limitations in hardware as well as to the acoustic attenuation in tissue, state-of-the-art reconstruction methods deliver only approximations of the initial pressure distribution. To overcome the limited view problem, we present a machine learning-based approach to the reconstruction of initial pressure from limited view PA data. Our method involves a fully convolutional deep neural network based on a U-Net-like architecture with pixel-wise regression loss on the acquired PA images. It is trained and validated on in silico data generated with Monte Carlo simulations. In an initial study we found an increase in accuracy over the state-of-the-art when reconstructing simulated linear-array scans of blood vessels.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simonen, F.A.; Johnson, K.I.; Liebetrau, A.M.

The VISA-II (Vessel Integrity Simulation Analysis code was originally developed as part of the NRC staff evaluation of pressurized thermal shock. VISA-II uses Monte Carlo simulation to evaluate the failure probability of a pressurized water reactor (PWR) pressure vessel subjected to a pressure and thermal transient specified by the user. Linear elastic fracture mechanics methods are used to model crack initiation and propagation. Parameters for initial crack size and location, copper content, initial reference temperature of the nil-ductility transition, fluence, crack-initiation fracture toughness, and arrest fracture toughness are treated as random variables. This report documents an upgraded version of themore » original VISA code as described in NUREG/CR-3384. Improvements include a treatment of cladding effects, a more general simulation of flaw size, shape and location, a simulation of inservice inspection, an updated simulation of the reference temperature of the nil-ductility transition, and treatment of vessels with multiple welds and initial flaws. The code has been extensively tested and verified and is written in FORTRAN for ease of installation on different computers. 38 refs., 25 figs.« less

Contribution of job strain, job status and marital status to laboratory and ambulatory blood pressure in patients with mild hypertension.

PubMed

Blumenthal, J A; Thyrum, E T; Siegel, W C

1995-02-01

The effects of job strain, occupational status, and marital status on blood pressure were evaluated in 99 men and women with mild hypertension. Blood pressure was measured during daily life at home and at work over 15 h of ambulatory blood pressure monitoring. On a separate day, blood pressure was measured in the laboratory during mental stress testing. As expected, during daily life, blood pressure was higher at work than at home. High job strain was associated with elevated systolic blood pressure among women, but not men. However, both men and women with high status occupations had significantly higher blood pressures during daily life and during laboratory mental stress testing. This was especially true for men, in that men with high job status had higher systolic blood pressures than low job status men. Marital status also was an important moderating variable, particularly for women, with married women having higher ambulatory blood pressures than single women. During mental stress testing, married persons had higher systolic blood pressures than unmarried individuals. These data suggest that occupational status and marital status may contribute even more than job strain to variations in blood pressure during daily life and laboratory testing.

Numerical Investigation of Magnetically Driven Isentropic Compression of Solid Aluminum Cylinders with a Semi-Analytical Code

NASA Astrophysics Data System (ADS)

Largent, Billy T.

The state of matter at extremely high pressures and densities is of fundamental interest to many branches of research, including planetary science, material science, condensed matter physics, and plasma physics. Matter with pressures, or energy densities, above 1 megabar (100 gigapascal) are defined as High Energy Density (HED) plasmas. They are directly relevant to the interiors of planets such as Earth and Jupiter and to the dense fuels in Inertial Confinement Fusion (ICF) experiments. To create HEDP conditions in laboratories, a sample may be compressed by a smoothly varying pressure ramp with minimal temperature increase, following the isentropic thermodynamic process. Isentropic compression of aluminum targets has been done using magnetic pressure produced by megaampere, pulsed power currents having 100 ns rise times. In this research project, magnetically driven, cylindrical isentropic compression has been numerically studied. In cylindrical geometry, material compression and pressure become higher than in planar geometry due to geometrical effects. Based on a semi-analytical model for the Magnetized Liner Inertial Fusion (MagLIF) concept, a code called "SA" was written to design cylindrical compression experiments on the 1.0 MA Zebra pulsed power generator at the Nevada Terawatt Facility (NTF). To test the physics models in the code, temporal progresses of rod compression and pressure were calculated with SA and compared with 1-D magnetohydrodynamic (MHD) codes. The MHD codes incorporated SESAME tables, for equation of state and resistivity, or the classical Spitzer model. A series of simulations were also run to find optimum rod diameters for 1.0 MA and 1.8 MA Zebra current pulses. For a 1.0 MA current peak and 95 ns rise time, a maximum compression of 2.35 ( 6.3 g/cm3) and a pressure of 900 GPa within a 100 mum radius were found for an initial diameter of 1.05 mm. For 1.8 MA peak simulations with the same rise time, the initial diameter of 1.3 mm was optimal with 3.32 ( 9.0 g/cm 3) compression.

Extraction of valuable metals by microwave discharge in crude oil

NASA Astrophysics Data System (ADS)

Lebedev, Yu A.; Averin, K. A.

2018-05-01

Microwave discharges in liquids are a new direction in the physics and chemistry of low temperature plasma. The article describes the results of experiments on the separation of metals from oil when a microwave discharge is created at atmospheric pressure in its volume. It is shown for the first time that the content of metals Al, Co, Cu, Fe, Mo, Ni, V, and Zn in a tree-like structure deposited on the microwave antenna is up to 10 times higher than their content in the initial substance.

Influence of structural parameters on the tendency of VVER-1000 reactor pressure vessel steel to temper embrittlement

NASA Astrophysics Data System (ADS)

Gurovich, B.; Kuleshova, E.; Zabusov, O.; Fedotova, S.; Frolov, A.; Saltykov, M.; Maltsev, D.

2013-04-01

In this paper the influence of structural parameters on the tendency of steels to reversible temper embrittlement was studied for assessment of performance properties of reactor pressure vessel steels with extended service life. It is shown that the growth of prior austenite grain size leads to an increase of the critical embrittlement temperature in the initial state. An embrittlement heat treatment at the temperature of maximum manifestation of temper embrittlement (480 °C) shifts critical embrittlement temperature to higher values due to the increase of the phosphorus concentration on grain boundaries. There is a correlation between phosphorus concentration on boundaries of primary austenite grains and the share of brittle intergranular fracture (that, in turn, depends on impact test temperature) in the fracture surfaces of the tested Charpy specimens.

Solid spherical glass particle impingement studies of plastic materials

NASA Technical Reports Server (NTRS)

Rao, P. V.; Young, S. G.; Buckley, D. H.

1983-01-01

Erosion experiments on polymethyl methacrylate (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE) were conducted with spherical glass beads impacting at normal incidence. Optical and scanning electron microscopic studies and surface profile measurements were made on specimens at predetermined test intervals. During the initial stage of damage to PMMA and polycarbonate, material expands or builds up above the original surface. However, this buildup disappears as testing progresses. Little or no buildup was observed on PTFE. PTFE is observed to be the most resistant material to erosion and PMMA the least. At low impact pressures, material removal mechanisms are believed to be similar to those for metallic materials. However, at higher pressures, surface melting is indicated at the center of impact. Deformation and fatigue appear to play major roles in the material removal process with possible melting or softening.

Expansion Rate Scaling and Energy Evolution in the Electron Diffusion Gauge Experiment.

NASA Astrophysics Data System (ADS)

Morrison, Kyle; Davidson, Ronald; Paul, Stephen; Jenkins, Thomas

2001-10-01

The expansion of the Electron Diffusion Gauge (EDG) pure electron plasma resulting from collisions with background neutral gas atoms is characterized by the pressure and magnetic field scalings of the profile expansion rate (d/dt) < r^2 >. The measured expansion rate in the higher pressure regime is found to be in good agreement with the classical estimate [ fracddt< r^2 > = frac2 NL e^2 ν_enm ω_c^2 (1+frac2TNL e^2). ] Expansion rate data is obtained for smaller initial plasmas (with outer diameter 1/4 of the trap wall diameter) generated with an improved filament installed in the EDG device, and the data is compared with previous results for larger-filament plasmas. The dynamic energy evolution of the plasma, including electrostatic energy and inferred temperature evolution for several of the measurements, is discussed.

The systolic blood pressure difference between arms and cardiovascular disease in the Framingham Heart Study.

PubMed

Weinberg, Ido; Gona, Philimon; O'Donnell, Christopher J; Jaff, Michael R; Murabito, Joanne M

2014-03-01

An increased interarm systolic blood pressure difference is an easily determined physical examination finding. The relationship between interarm systolic blood pressure difference and risk of future cardiovascular disease is uncertain. We described the prevalence and risk factor correlates of interarm systolic blood pressure difference in the Framingham Heart Study (FHS) original and offspring cohorts and examined the association between interarm systolic blood pressure difference and incident cardiovascular disease and all-cause mortality. An increased interarm systolic blood pressure difference was defined as ≥ 10 mm Hg using the average of initial and repeat blood pressure measurements obtained in both arms. Participants were followed through 2010 for incident cardiovascular disease events. Multivariable Cox proportional hazards regression analyses were performed to investigate the effect of interarm systolic blood pressure difference on incident cardiovascular disease. We examined 3390 (56.3% female) participants aged 40 years and older, free of cardiovascular disease at baseline, mean age of 61.1 years, who attended a FHS examination between 1991 and 1994 (original cohort) and from 1995 to 1998 (offspring cohort). The mean absolute interarm systolic blood pressure difference was 4.6 mm Hg (range 0-78). Increased interarm systolic blood pressure difference was present in 317 (9.4%) participants. The median follow-up time was 13.3 years, during which time 598 participants (17.6%) experienced a first cardiovascular event, including 83 (26.2%) participants with interarm systolic blood pressure difference ≥ 10 mm Hg. Compared with those with normal interarm systolic blood pressure difference, participants with an elevated interarm systolic blood pressure difference were older (63.0 years vs 60.9 years), had a greater prevalence of diabetes mellitus (13.3% vs 7.5%,), higher systolic blood pressure (136.3 mm Hg vs 129.3 mm Hg), and a higher total cholesterol level (212.1 mg/dL vs 206.5 mg/dL). Interarm systolic blood pressure difference was associated with a significantly increased hazard of incident cardiovascular events in the multivariable adjusted model (hazard ratio 1.38; 95% CI, 1.09-1.75). For each 1-SD-unit increase in absolute interarm systolic blood pressure difference, the hazard ratio for incident cardiovascular events was 1.07 (95% CI, 1.00-1.14) in the fully adjusted model. There was no such association with mortality (hazard ratio 1.02; 95% CI 0.76-1.38). In this community-based cohort, an interarm systolic blood pressure difference is common and associated with a significant increased risk for future cardiovascular events, even when the absolute difference in arm systolic blood pressure is modest. These findings support research to expand clinical use of this simple measurement. Copyright © 2014 Elsevier Inc. All rights reserved.

Evaluation of the effects of hospital visit stress on physiologic variables in dogs.

PubMed

Bragg, Ryan F; Bennett, Jennifer S; Cummings, Annelise; Quimby, Jessica M

2015-01-15

To evaluate differences in pulse rate, rectal temperature, respiratory rate, and systolic arterial blood pressure in dogs between the home and veterinary hospital environments. Prospective observational study. 30 client-owned healthy dogs. Study dogs had respiratory rate, pulse rate, rectal temperature, and systolic arterial blood pressure measured in their home environment. Dogs were then transported to the veterinary hospital, and measurements were repeated. Significant differences in blood pressure, rectal temperature, and pulse rate were observed between measurements obtained in the home and hospital environments. Mean blood pressure increased by 16% (95% confidence interval [CI], 8.8% to 24%), rectal temperature increased by < 1% (95% CI, 0.1% to 0.6%), and pulse rate increased by 11% (95% CI, 5.3% to 17.6%). The number of dogs panting in the hospital environment (19/30 [63%]) was significantly higher than the number of dogs panting in the home environment (5/30 [17%]) Results of the present study suggested that practitioners should consider stress from transportation and environmental change when canine patients have abnormalities of vital signs on initial examination, and the variables in question should be rechecked before a definitive diagnosis of medical illness is reached or extensive further workup is pursued.

Experimental investigation on circumferential and axial temperature gradient over fuel channel under LOCA

NASA Astrophysics Data System (ADS)

Yadav, Ashwini Kumar; kumar, Ravi; Gupta, Akhilesh; Chatterjee, Barun; Mukhopadhyay, Deb; Lele, H. G.

2014-06-01

In a nuclear reactor temperature rises drastically in fuel channels under loss of coolant accident due to failure of primary heat transportation system. Present investigation has been carried out to capture circumferential and axial temperature gradients during fully and partially voiding conditions in a fuel channel using 19 pin fuel element simulator. A series of experiments were carried out by supplying power to outer, middle and center rods of 19 pin fuel simulator in ratio of 1.4:1.1:1. The temperature at upper periphery of pressure tube (PT) was slightly higher than at bottom due to increase in local equivalent thermal conductivity from top to bottom of PT. To simulate fully voided conditions PT was pressurized at 2.0 MPa pressure with 17.5 kW power injection. Ballooning initiated from center and then propagates towards the ends and hence axial temperature difference has been observed along the length of PT. For asymmetric heating, upper eight rods of fuel simulator were activated and temperature difference up-to 250 °C has been observed from top to bottom periphery of PT. Such situation creates steep circumferential temperature gradient over PT and could lead to breaching of PT under high pressure.

Magnetic flux tailoring through Lenz lenses for ultrasmall samples: A new pathway to high-pressure nuclear magnetic resonance

PubMed Central

Meier, Thomas; Wang, Nan; Mager, Dario; Korvink, Jan G.; Petitgirard, Sylvain; Dubrovinsky, Leonid

2017-01-01

A new pathway to nuclear magnetic resonance (NMR) spectroscopy for picoliter-sized samples (including those kept in harsh and extreme environments, particularly in diamond anvil cells) is introduced, using inductively coupled broadband passive electromagnetic lenses, to locally amplify the magnetic field at the isolated sample, leading to an increase in sensitivity. The lenses are adopted for the geometrical restrictions imposed by a toroidal diamond indenter cell and yield signal-to-noise ratios at pressures as high as 72 GPa at initial sample volumes of only 230 pl. The corresponding levels of detection are found to be up to four orders of magnitude lower compared to formerly used solenoidal microcoils. Two-dimensional nutation experiments on long-chained alkanes, CnH2n+2 (n = 16 to 24), as well as homonuclear correlation spectroscopy on thymine, C5H6N2O2, were used to demonstrate the feasibility of this approach for higher-dimensional NMR experiments, with a spectral resolution of at least 2 parts per million. This approach opens up the field of ultrahigh-pressure sciences to one of the most versatile spectroscopic methods available in a pressure range unprecedented up to now. PMID:29230436

Magnetic flux tailoring through Lenz lenses for ultrasmall samples: A new pathway to high-pressure nuclear magnetic resonance.

PubMed

Meier, Thomas; Wang, Nan; Mager, Dario; Korvink, Jan G; Petitgirard, Sylvain; Dubrovinsky, Leonid

2017-12-01

A new pathway to nuclear magnetic resonance (NMR) spectroscopy for picoliter-sized samples (including those kept in harsh and extreme environments, particularly in diamond anvil cells) is introduced, using inductively coupled broadband passive electromagnetic lenses, to locally amplify the magnetic field at the isolated sample, leading to an increase in sensitivity. The lenses are adopted for the geometrical restrictions imposed by a toroidal diamond indenter cell and yield signal-to-noise ratios at pressures as high as 72 GPa at initial sample volumes of only 230 pl. The corresponding levels of detection are found to be up to four orders of magnitude lower compared to formerly used solenoidal microcoils. Two-dimensional nutation experiments on long-chained alkanes, C n H 2 n +2 ( n = 16 to 24), as well as homonuclear correlation spectroscopy on thymine, C 5 H 6 N 2 O 2 , were used to demonstrate the feasibility of this approach for higher-dimensional NMR experiments, with a spectral resolution of at least 2 parts per million. This approach opens up the field of ultrahigh-pressure sciences to one of the most versatile spectroscopic methods available in a pressure range unprecedented up to now.

Mechanical behavior and localized failure modes in a porous basalt from the Azores

NASA Astrophysics Data System (ADS)

Loaiza, S.; Fortin, J.; Schubnel, A.; Gueguen, Y.; Vinciguerra, S.; Moreira, M.

2012-10-01

Basaltic rocks are the main component of the oceanic upper crust, thus of potential interest for water and geothermal resources, storage of CO2 and volcanic edifice stability. In this work, we investigated experimentally the mechanical behavior and the failure modes of a porous basalt, with an initial connected porosity of 18%. Results were acquired under triaxial compression experiments at confining pressure in the range of 25-200 MPa on water saturated samples. In addition, a purely hydrostatic test was also performed to reach the pore collapse critical pressure P*. During hydrostatic loading, our results show that the permeability is highly pressure dependent, which suggests that the permeability is mainly controlled by pre-existing cracks. When the sample is deformed at pressure higher than the pore collapse pressure P*, some very small dilatancy develops due to microcracking, and an increase in permeability is observed. Under triaxial loading, two modes of deformation can be highlighted. At low confining pressure (Pc < 50 MPa), the samples are brittle and shear localization occurs. For confining pressure > 50 MPa, the stress-strain curves are characterized by strain hardening and volumetric compaction. Stress drops are also observed, suggesting that compaction may be localized. The presence of compaction bands is confirmed by our microstructure analysis. In addition, the mechanical data allows us to plot the full yield surface for this porous basalt, which follows an elliptic cap as previously observed in high porosity sandstones and limestones.

Effects of instant controlled pressure drop process on physical and sensory properties of puffed wheat snack.

PubMed

Yağcı, Sibel

2017-04-01

In this study, research on the development of a puffed wheat snack using the instant controlled pressure drop (DIC) process was carried out. Snack products were produced by expanding moistened wheat under various DIC processing conditions in order to obtain adequate puffing, followed by drying in a hot air dryer. The effects of operational variables such as wheat initial moisture content (11-23% w/w, wet basis), processing pressure (3-5 × 10 2 kPa) and processing time (3-11 min) on the physical (density, color and textural characteristics) and sensory properties of the product were investigated. The physical properties of the wheat snack were most affected by changes in processing pressure, followed by processing time and wheat moisture content. Increasing processing pressure and time often improved expansion and textural properties but led to darkening of the raw wheat color. The most acceptable snack in terms of physical properties was obtained at the lowest wheat moisture content. Sensory analysis suggested that consumer acceptability was optimal for wheat snacks produced at higher processing pressure, medium processing time and lower moisture content. The most desirable conditions for puffed wheat snack production using the DIC process were determined as 11% (w/w) of wheat moisture content, 5 × 10 2 kPa of processing pressure and 7 min of processing time. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Ramp compression of a metallic liner driven by a shaped 5 MA current on the SPHINX machine

NASA Astrophysics Data System (ADS)

D'Almeida, Thierry; Lassalle, Francis; Morell, Alain; Grunenwald, Julien; Zucchini, Frédéric; Loyen, Arnaud; Maysonnave, Thomas; Chuvatin, Alexandre

2013-06-01

SPHINX is a 6MA, 1- μs Linear Transformer Driver operated by the CEA Gramat (France) and primarily used for imploding Z-pinch loads for radiation effects studies. Among the options that are currently being considered for improving the generator performances, there is a compact Dynamic Load Current Amplifier (DLCM). A method for performing magnetic ramp compression experiments, without modifying the generator operation scheme, was developed using the DLCM to shape the initial current pulse. We present the overall experimental configuration chosen for these experiments, based on electrical and hydrodynamic simulations. Initial results obtained over a set of experiments on an aluminum cylindrical liner, ramp-compressed to a peak pressure of 23 GPa, are presented. Details of the electrical and Photonic Doppler Velocimetry (PDV) setups used to monitor and diagnose the ramp compression experiments are provided. Current profiles measured at various locations across the system, particularly the load current, agree with simulated current profile and demonstrate adequate pulse shaping by the DLCM. The liner inner free surface velocity measurements agree with the hydrocode results obtained using the measured load current as the input. Higher ramp pressure levels are foreseen in future experiments with an improved DLCM system.

Participation and cardiovascular risk reduction in a voluntary worksite nutrition and physical activity program

PubMed Central

Thorndike, Anne N.; Healey, Erica; Sonnenberg, Lillian; Regan, Susan

2010-01-01

Objective In a cohort of employees participating in a worksite nutrition and physical activity program, we compared program completion and changes in cardiovascular risk factors by baseline body mass index. Methods In 2007, 774 employees enrolled in a 10 week program at a hospital in Boston, MA. Program completion and change in weight, cholesterol, and blood pressure were compared between obese (BMI≥30), overweight (BMI=25–29.9), and normal weight (BMI<25) participants. Results At baseline, 63% were obese or overweight and had higher blood pressure and cholesterol compared to normal weight participants. Program completion was 82% and did not differ by BMI. Mean weight loss was 1.9 kg at end of program (p<0.001) and 0.4 kg at 1 year (p=0.002). At end of program, participants with BMI≥30 lost 3.0% body weight vs. 2.7% for BMI=25–29.9 and 1.7% for BMI<25 (p<0.001), but weight loss at 1 year did not differ by BMI. Mean cholesterol and blood pressure were lower at end of program and 1 year (p all <0.005) but did not differ by BMI. Conclusions Worksite programs can successfully initiate cardiovascular risk reduction among employees, but more intensive interventions are needed to make significant improvements in the health of higher risk obese employees. PMID:21130804

Automated Office Blood Pressure Measurement

PubMed Central

2018-01-01

Manual blood pressure (BP) recorded in routine clinical practice is relatively inaccurate and associated with higher readings compared to BP measured in research studies in accordance with standardized measurement guidelines. The increase in routine office BP is the result of several factors, especially the presence of office staff, which tends to make patients nervous and also allows for conversation to occur. With the disappearance of the mercury sphygmomanometer because of environmental concerns, there is greater use of oscillometric BP recorders, both in the office setting and elsewhere. Although oscillometric devices may reduce some aspects of observer BP measurement error in the clinical setting, they are still associated with higher BP readings, known as white coat hypertension (for diagnosis) or white coat effect (with treated hypertension). Now that fully automated sphygmomanometers are available which are capable of recording several readings with the patient resting quietly, there is no longer any need to have office staff present when BP is being recorded. Such readings are called automated office blood pressure (AOBP) and they are both more accurate than conventional manual office BP and not associated with the white coat phenomena. AOBP readings are also similar to the awake ambulatory BP and home BP, both of which are relatively good predictors of cardiovascular risk. The available evidence suggests that AOBP should now replace manual or electronic office BP readings when screening patients for hypertension and also after antihypertensive drug therapy is initiated. PMID:29625508

Stable Tearing and Buckling Responses of Unstiffened Aluminum Shells with Long Cracks

NASA Technical Reports Server (NTRS)

Starnes, James H., Jr.; Rose, Cheryl A.

1999-01-01

The results of an analytical and experimental study of the nonlinear response of thin, unstiffened, aluminum cylindrical shells with a long longitudinal crack are presented. The shells are analyzed with a nonlinear shell analysis code that accurately accounts for global and local structural response phenomena. Results are presented for internal pressure and for axial compression loads. The effect of initial crack length on the initiation of stable crack growth and unstable crack growth in typical shells subjected to internal pressure loads is predicted using geometrically nonlinear elastic-plastic finite element analyses and the crack-tip-opening angle (CTOA) fracture criterion. The results of these analyses and of the experiments indicate that the pressure required to initiate stable crack growth and unstable crack growth in a shell subjected to internal pressure loads decreases as the initial crack length increases. The effects of crack length on the prebuckling, buckling and postbuckling responses of typical shells subjected to axial compression loads are also described. For this loading condition, the crack length was not allowed to increase as the load was increased. The results of the analyses and of the experiments indicate that the initial buckling load and collapse load for a shell subjected to axial compression loads decrease as the initial crack length increases. Initial buckling causes general instability or collapse of a shell for shorter initial crack lengths. Initial buckling is a stable local response mode for longer initial crack lengths. This stable local buckling response is followed by a stable postbuckling response, which is followed by general or overall instability of the shell.

Stable Tearing and Buckling Responses of Unstiffened Aluminum Shells with Long Cracks

NASA Technical Reports Server (NTRS)

Starnes, James H., Jr.; Rose, Cheryl A.

1998-01-01

The results of an analytical and experimental study of the nonlinear response of thin, unstiffened, aluminum cylindrical shells with a long longitudinal crack are presented. The shells are analyzed with a nonlinear shell analysis code that accurately accounts for global and local structural response phenomena. Results are presented for internal pressure and for axial compression loads. The effect of initial crack length on the initiation of stable crack growth and unstable crack growth in typical shells subjected to internal pressure loads is predicted using geometrically nonlinear elastic-plastic finite element analyses and the crack-tip-opening angle (CTOA) fracture criterion. The results of these analyses and of the experiments indicate that the pressure required to initiate stable crack growth and unstable crack growth in a shell subjected to internal pressure loads decreases as the initial crack length increases. The effects of crack length on the prebuckling, buckling and postbuckling responses of typical shells subjected to axial compression loads are also described. For this loading condition, the crack length was not allowed to increase as the load was increased. The results of the analyses and of the experiments indicate that the initial buckling load and collapse load for a shell subjected to axial compression loads decrease as the initial crack length increases. Initial buckling causes general instability or collapse of a shell for shorter initial crack lengths. Initial buckling is a stable local response mode for longer initial crack lengths. This stable local buckling response is followed by a stable postbuckling response, which is followed by general or overall instability of the shell.

Extra-intracranial blood shunt mimicking aneurysm rupture: intracranial-pressure-controlled rabbit subarachnoid hemorrhage model.

PubMed

Marbacher, Serge; Sherif, Camillo; Neuschmelting, Volker; Schläppi, Janine-Ai; Takala, Jukka; Jakob, Stephan M; Fandino, Javier

2010-08-30

The achieved degree of delayed cerebral vasospasm (DCVS) in the rabbits most frequently applied cistern magna blood injection model is often mild. The aim of this study was to characterize and evaluate the feasibility of an experimental SAH technique that mimics pathophysiological mechanisms and triggers higher degrees of DCVS. SAH was induced by extracranial-intracranial (EC/IC) shunting of blood from the subclavian artery into the great cerebral cistern. Intracranial pressure (ICP), arterial blood pressure, heart rate, arterial blood gas analysis, and neurological status were monitored throughout the experiments. The magnitude of spasm was determined by comparison of pre-SAH (day 0) and post-SAH (day 3) angiograms and postmortem morphometric analysis of the basilar artery. A total of 13 experiments (SAH, n=11; controls, n=2) were performed. Two animals died after initiation of the EC/IC blood shunt in respiratory arrest. In SAH animals, ICP (baseline: 12+/-1 [mean+/-SD]; peak: 51+/-4; steady-state level: 15+/-2 mm Hg) rose to diastolic blood pressure levels (56+/-3 mm Hg) within 98+/-20s, and fell to a steady state within 186+/-41 s. SAH-induced vasoconstriction of the basilar artery was 53.1+/-2.8% on day 3 compared to baseline (P<0.05) and histology confirmed marked vasoconstriction. This novel technique of SAH induction closely mimics the pathophysiological sequelae of aneurysm rupture and triggers constant higher degrees of delayed cerebral vasospasm than previously described rabbit models. The severity of vasospasm attained offers a unique opportunity to evaluate future therapeutic treatment options. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air.

PubMed

Jain, Vishal; Visani, Anand; Srinivasan, R; Agarwal, Vivek

2018-03-01

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (∼0.28 W/cm 2 ) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (∼50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air

NASA Astrophysics Data System (ADS)

Jain, Vishal; Visani, Anand; Srinivasan, R.; Agarwal, Vivek

2018-03-01

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (˜0.28 W/cm2) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (˜50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

A combined field and numerical approach to understanding dilute pyroclastic density current dynamics and hazard potential: Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Brand, Brittany D.; Gravley, Darren M.; Clarke, Amanda B.; Lindsay, Jan M.; Bloomberg, Simon H.; Agustin-Flores, Javier; Németh, Károly

2014-04-01

The most dangerous and deadly hazards associated with phreatomagmatic eruptions in the Auckland Volcanic Field (AVF; Auckland, New Zealand) are those related to volcanic base surges - dilute, ground-hugging, particle laden currents with dynamic pressures capable of severe to complete structural damage. We use the well-exposed base surge deposits of the Maungataketake tuff ring (Manukau coast, Auckland), to reconstruct flow dynamics and destructive potential of base surges produced during the eruption. The initial base surge(s) snapped trees up to 0.5 m in diameter near their base as far as 0.7-0.9 km from the vent. Beyond this distance the trees were encapsulated and buried by the surge in growth position. Using the tree diameter and yield strength of the wood we calculate that dynamic pressures (Pdyn) in excess of 12-35 kPa are necessary to cause the observed damage. Next we develop a quantitative model for flow of and sedimentation from a radially-spreading, dilute pyroclastic density currents (PDCs) to determine the damage potential of the base surges produced during the early phases of the eruption and explore the implications of this potential on future eruptions in the region. We find that initial conditions with velocities on the order of 65 m s- 1, bulk density of 38 kg m- 3 and initial, near-vent current thicknesses of 60 m reproduce the field-based Pdyn estimates and runout distances. A sensitivity analysis revealed that lower initial bulk densities result in shorter run-out distances, more rapid deceleration of the current and lower dynamic pressures. Initial velocity does not have a strong influence on run-out distance, although higher initial velocity and slope slightly decrease runout distance due to higher rates of atmospheric entrainment. Using this model we determine that for base surges with runout distances of up to 4 km, complete destruction can be expected within 0.5 km from the vent, moderate destruction can be expected up to 2 km, but much less damage is expected up to the final runout distance of 4 km. For larger eruptions (base surge runout distance 4-6 km), Pdyn of > 35 kPa can be expected up to 2.5 km from source, ensuring complete destruction within this area. Moderate damage to reinforced structures and damage to weaker structures can be expected up to 6 km from source. In both cases hot ash may still cause damage due to igniting flammable materials in the distal-most regions of a base surge. This work illustrates our ability to combine field observations and numerical models to explore the depositional mechanisms, macroscale current dynamics, and potential impact of dilute PDCs. Thus, this approach may serve as a tool to understand the damage potential and extent of previous and potential future eruptions in the AVF.

In situ pore-pressure evolution during dynamic CPT measurements in soft sediments of the western Baltic Sea

NASA Astrophysics Data System (ADS)

Seifert, Annedore; Stegmann, Sylvia; Mörz, Tobias; Lange, Matthias; Wever, Thomas; Kopf, Achim

2008-08-01

We present in situ strength and pore-pressure measurements from 57 dynamic cone penetration tests in sediments of Mecklenburg ( n = 51), Eckernförde ( n = 2) and Gelting ( n = 4) bays, western Baltic Sea, characterised by thick mud layers and partially free microbial gas resulting from the degradation of organic material. In Mecklenburg and Eckernförde bays, sediment sampling by nine gravity cores served sedimentological characterisation, analyses of geotechnical properties, and laboratory shear tests. At selected localities, high-resolution echo-sounder profiles were acquired. Our aim was to deploy a dynamic cone penetrometer (CPT) to infer sediment shear strength and cohesion of the sea bottom as a function of fluid saturation. The results show very variable changes in pore pressure and sediment strength during the CPT deployments. The majority of the CPT measurements ( n = 54) show initially negative pore-pressure values during penetration, and a delayed response towards positive pressures thereafter. This so-called type B pore-pressure signal was recorded in all three bays, and is typically found in soft muds with high water contents and undrained shear strengths of 1.6-6.4 kPa. The type B signal is further affected by displacement of sediment and fluid upon penetration of the lance, skin effects during dynamic profiling, enhanced consolidation and strength of individual horizons, the presence of free gas, and a dilatory response of the sediment. In Mecklenburg Bay, the remaining small number of CPT measurements ( n = 3) show a well-defined peak in both pore pressure and cone resistance during penetration, i.e. an initial marked increase which is followed by exponential pore-pressure decay during dissipation. This so-called type A pore-pressure signal is associated with normally consolidated mud, with indurated clay layers showing significantly higher undrained shear strength (up to 19 kPa). In Eckernförde and Gelting bays pore-pressure response type B is exclusively found, while in Mecklenburg Bay types A and B were detected. Despite the striking similarities in incremental density increase and shear strength behaviour with depth, gas occurrence and subtle variations in the coarse-grained fraction cause distinct pore-pressure curves. Gaseous muds interbedded with silty and sandy layers are most common in the three bays, and the potential effect of free gas (i.e. undersaturated pore space) on in situ strength has to be explored further.

Racial discrimination associated with higher diastolic blood pressure in a sample of American Indian adults

PubMed Central

Thayer, Zaneta M.; Blair, Irene V.; Buchwald, Dedra S.; Manson, Spero M.

2017-01-01

Objectives Hypertension prevalence is high among American Indians (AIs). AIs experience a substantial burden of interpersonal racial discrimination, which in other populations has been associated with higher blood pressure. The purpose of this study is to understand whether racial discrimination experiences are associated with higher blood pressure in AIs. Materials and Methods We used the Everyday Discrimination Scale to evaluate the relationship between discrimination and measured blood pressure among 77 AIs from two reservation communities in the Northern Plains. We used multivariate linear regression to evaluate the association of racial discrimination with systolic and diastolic blood pressure, respectively. Racial discrimination, systolic blood pressure, and diastolic blood pressure were analyzed as continuous variables. All analyses adjusted for sex, waist circumference, age, posttraumatic stress disorder status, and education. Results We found that 61% of participants experienced discrimination that they attributed to their race or ancestry. Racial discrimination was associated with significantly higher diastolic blood pressure (β = 0.22, SE = 0.09, P = 0.02), and with a similar non-significant trend toward higher systolic blood pressure (β = 0.25, SE = 0.15, P = 0.09). Conclusion The results of this analysis suggest that racial discrimination may contribute to higher diastolic blood pressure within Native communities. These findings highlight one pathway through which the social environment can shape patterns of biology and health in AI and other socially and politically marginalized groups. PMID:28198537

Water infiltration in prewetted porous media: dynamic capillary pressure and Green-Ampt modeling

NASA Astrophysics Data System (ADS)

Hsu, S.; Hilpert, M.

2013-12-01

Recently, an experimental study has shown that the modified Green-Ampt (GA) model, which accounts for a velocity-dependent capillary pressure, can describe water infiltration in dry sand columns better than the classical GA model. Studies have also shown that the initial water content of prewetted porous media affects the dynamic capillary pressure during infiltration. In this study, we performed a series of downward water infiltration experiments in prewetted sand columns for four different initial water contents: 0%, 3.3%, 6.5%, and 13.8%. We also used three different ponding heights: 10 cm, 20 cm, and 40 cm. As expected, an increase in ponding height resulted in a monotonic increase in cumulative infiltration. However, we found anomalous behavior, in that the cumulative infiltration did not monotonically decrease as the initial water content increased. When modeling the experiments with the modified GA approach, we linked this anomalous behavior to the reduction factor in the model for dynamic capillary pressure that is a function of initial water content.

Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen/Liquid Methane Main Engine

NASA Technical Reports Server (NTRS)

Melcher, J. C.; Morehead, Robert L.

2014-01-01

The Project Morpheus liquid oxygen (LOX) / liquid methane rocket engines demonstrated acousticcoupled combustion instabilities during sea-level ground-based testing at the NASA Johnson Space Center (JSC) and Stennis Space Center (SSC). High-amplitude, 1T, 1R, 1T1R (and higher order) modes appear to be triggered by injector conditions. The instability occurred during the Morpheus-specific engine ignition/start sequence, and did demonstrate the capability to propagate into mainstage. However, the instability was never observed to initiate during mainstage, even at low power levels. The Morpheus main engine is a JSC-designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. Two different engine designs, named HD4 and HD5, and two different builds of the HD4 engine all demonstrated similar instability characteristics. Through the analysis of more than 200 hot fire tests on the Morpheus vehicle and SSC test stand, a relationship between ignition stability and injector/chamber pressure was developed. The instability has the distinct characteristic of initiating at high relative injection pressure drop (dP) at low chamber pressure (Pc); i.e., instabilities initiated at high dP/Pc at low Pc during the start sequence. The high dP/Pc during start results during the injector /chamber chill-in, and is enhanced by hydraulic flip in the injector orifice elements. Because of the fixed mixture ratio of the existing engine design (the main valves share a common actuator), it is not currently possible to determine if LOX or methane injector dP/Pc were individual contributors (i.e., LOX and methane dP/Pc typically trend in the same direction within a given test). The instability demonstrated initiation characteristic of starting at or shortly after methane injector chillin. Colder methane (e.g., sub-cooled) at the injector inlet prior to engine start was much more likely to result in an instability. A secondary effect of LOX sub-cooling was also possibly observed; greater LOX sub- cooling improved stability. Some tests demonstrated a low-amplitude 1L-1T instability prior to LOX injector chill-in. The Morpheus main engine also demonstrated chug instabilities during some engine shutdown sequences on the flight vehicle and SSC test stand. The chug instability was also infrequently observed during the startup sequence. The chug instabilities predictably initiated at low dP/Pc at low Pc. The chug instabilities were always self-limiting; startup chug instabilities terminated during throttle-up and shutdown chug instabilities decayed by shutdown termination.

Can high pressure I-II transitions in semiconductors be affected by plastic flow and nanocrystal precipitation in phase I?

NASA Astrophysics Data System (ADS)

Weinstein, B. A.; Lindberg, G. P.

Pressure-Raman spectroscopy in ZnSe and ZnTe single crystals reveals that Se and Te nano-crystals (NCs) precipitate in these II-VI hosts for pressures far below their I-II phase transitions. The inclusions are evident from the appearance and negative pressure-shift of the A1 Raman peaks of Se and Te (trigonal phase). The Se and Te NCs nucleate at dislocations and grain boundaries that arise from pressure-induced plastic flow. This produces chemical and structural inhomogeneities in the zincblende phase of the host. At substantially higher pressures, the I-II transition proceeds in the presence of these inhomogenities. This can affect the transition's onset pressure Pt and width ΔPt, and the occurrence of metastable phases along the transition path. Precipitation models in metals show that nucleation of inclusions depends on the Peierls stress τp and a parameter α related to the net free energy gained on nucleation. For favorable values of τp and α, NC precipitation at pressures below the I-II transition could occur in other compounds. We propose criteria to judge whether this is likely based on the observed ranges of τp in the hosts, and estimates of α derived from the cohesive energy densities of the NC materials. One finds trends that can serve as a useful guide, both to test the proposed criteria, and to decide when closer scrutiny of phase transition experiments is warranted, e.g., in powders where high dislocation densities are initially created

Assessing complexity of skin blood flow oscillations in response to locally applied heating and pressure in rats: Implications for pressure ulcer risk

NASA Astrophysics Data System (ADS)

Liao, Fuyuan; O'Brien, William D.; Jan, Yih-Kuen

2013-10-01

The objective of this study was to investigate the effects of local heating on the complexity of skin blood flow oscillations (BFO) under prolonged surface pressure in rats. Eleven Sprague-Dawley rats were studied: 7 rats underwent surface pressure with local heating (△t=10 °C) and 4 rats underwent pressure without heating. A pressure of 700 mmHg was applied to the right trochanter area of rats for 3 h. Skin blood flow was measured using laser Doppler flowmetry. The loading period was divided into nonoverlapping 30 min epochs. For each epoch, multifractal detrended fluctuation analysis (MDFA) was utilized to compute DFA coefficients and complexity of endothelial related metabolic, neurogenic, and myogenic frequencies of BFO. The results showed that under surface pressure, local heating led to a significant decrease in DFA coefficients of myogenic frequency during the initial epoch of loading period, a sustained decrease in complexity of myogenic frequency, and a significantly higher degree of complexity of metabolic frequency during the later phase of loading period. Surrogate tests showed that the reduction in complexity of myogenic frequency was associated with a loss of nonlinearity whereas increased complexity of metabolic frequency was associated with enhanced nonlinearity. Our results indicate that increased metabolic activity and decreased myogenic response due to local heating manifest themselves not only in magnitudes of metabolic and myogenic frequencies but also in their structural complexity. This study demonstrates the feasibility of using complexity analysis of BFO to monitor the ischemic status of weight-bearing skin and risk of pressure ulcers.

Experimental Investigation of Magnetic Superconducting and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures using Designer Diamond Anvils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maple, M. Brian; Jeffries, Jason R.; Ho, Pei-Chun

Pressure is often used as a controlled parameter for the investigation of condensed matter systems. In particular, pressure experiments can provide valuable information into the nature of superconductivity, magnetism, and the coexistence of these two phenomena. Some f-electron, heavy-fermion materials display interesting and novel behavior at moderately low pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require ultrahigh pressure techniques, techniques that generate significantly higher pressures than conventional methods, to sufficiently explore their important properties. To that end, we have been funded to develop an ultrahigh pressure diamond anvil cell facility at the Universitymore » of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena. Our goals for the first year of this grant were as follows: (a) set up and test a suitable refrigerator; (b) set up a laser and spectrometer fluorescence system to determine the pressure within the diamond anvil cell; (c) perform initial resistivity measurements at moderate pressures from room temperature to liquid helium temperatures ({approx}1K); (d) investigate f-electron materials within our current pressure capabilities to find candidate materials for high-pressure studies. During the past year, we have ordered almost all the components required to set up a diamond anvil cell facility at UCSD, we have received and implemented many of the components that have been ordered, we have performed low pressure research on several materials, and we have engaged in a collaborative effort with Sam Weir at Lawrence Livermore National Lab (LLNL) to investigate Au4V under ultrahigh pressure in a designer diamond anvil cell (dDAC). This report serves to highlight the progress we have made towards developing an ultrahigh pressure research facility at UCSD, the research performed in the past year, as well as future directions we plan to pursue.« less

Pre-ignition confinement and deflagration violence in LX-10 and PBX 9501

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tringe, J. W., E-mail: tringe2@llnl.gov; Glascoe, E. A.; McClelland, M. A.

In thermal explosions of the nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-based explosives LX-10 and PBX-9501, the pre-ignition spatial and temporal heating profile defines the ignition location. The ignition location then determines the extent of inertial confinement and the violence of the resulting deflagration. In this work, we present results of experiments in which ∼23 g cylinders of LX-10 and PBX 9501 in thin-walled aluminum confinement vessels were subjected to identical heating profiles but which presented starkly different energy release signatures. Post-explosion LX-10 containment vessels were completely fragmented, while the PBX 9501 vessels were merely ruptured. Flash x-ray radiography images show that the initiation locationmore » for the LX-10 is a few mm farther from the end caps of the vessel relative to the initiation location of PBX 9501. This difference increases deflagration confinement for LX-10 at the time of ignition and extends the pressurization time during which the deflagration front propagates in the explosive. The variation in the initiation location, in turn, is determined by the thermal boundary conditions, which differ for these two explosives because of the larger coefficient of thermal expansion and greater thermal stability of the Viton binder in LX-10 relative to the estane and bis(2,2-dinitropropyl) acetal/formal binder of the PBX 9501. The thermal profile and initiation location were modeled for LX-10 using the hydrodynamics and structures code ALE3D; results indicate temperatures in the vicinity of the ignition location in excess of 274 °C near the time of ignition. The conductive burn rates for these two explosives, as determined by flash x-ray radiography, are comparable in the range 0.1–0.2 mm/μs, somewhat faster than rates observed by strand burner experiments for explosives in the temperature range 150–180 °C and pressures up to 100 MPa. The thinnest-wall aluminum containment vessels presented here rupture at lower pressures, in the range 10 MPa, suggesting that moderately higher temperatures and pressures are present near the deflagration front. For these explosives, however the most important property for determining deflagration violence is the degree of inertial confinement.« less

Gas Pressure Monitored Iodide-Catalyzed Decomposition Kinetics of H[subscript 2]O[subscript 2]: Initial-Rate and Integrated-Rate Methods in the General Chemistry Lab

ERIC Educational Resources Information Center

Nyasulu, Frazier; Barlag, Rebecca

2010-01-01

The reaction kinetics of the iodide-catalyzed decomposition of [subscript 2]O[subscript 2] using the integrated-rate method is described. The method is based on the measurement of the total gas pressure using a datalogger and pressure sensor. This is a modification of a previously reported experiment based on the initial-rate approach. (Contains 2…

Comparison of pressure-controlled provocation discography using automated versus manual syringe pump manometry in patients with chronic low back pain.

PubMed

Derby, Richard; Lee, Sang Hoon; Lee, Jeong-Eun; Lee, Sang-Heon

2011-01-01

The study compares the rate of positive discograms using an automated versus a manual pressure-controlled injection devise and compares the pressure and volume values at various pressures and initial evoked pain and 6/10 or greater evoked pain. A retrospective study prospectively collected patient study data used in a prior prospective study and with prospectively collected data which is routinely collected per our institutional standardized audit protocol. Two custom-built disc manometers (automated injection speed control; manual injection speed control) were sequentially employed during provocation discography in 510 discs of 151 consecutive patients. Two hundred thirty-seven discs of 67 patients with chronic low back pain were evaluated using the automated manometer (automated group) and 273 discs of 84 patients were evaluated with a manual manometer (manual group). No significant differences in positive discogram rates were found between the automated and manual groups (32.1% vs 32.6% per disc, respectively, P>0.05). No significant differences in low-pressure positive discogram rates were found (16.0% vs 15.0% per disc, automated group versus manual group, respectively, P>0.05). However, there were significantly increased volumes and lower pressures at initial and "bad" pain provocation. The study results found equivalent positive discogram rates following a series of pressure-controlled discography using either an automated or manual pressure devise. There were, however significant increases in volume at both initial onset of evoked pain and at 6/10 pain when using the automated injection devise that may have caused the observed lower opening pressure and lower pressure values at initial evoked pain. Assuming increased volumes are innocuous, automated injection is inherently more controlled and may better reduce unintended and often unrecorded spurious high dynamic pressure peaks thereby reducing conscious and unconscious operator bias. Wiley Periodicals, Inc.

Acute microcirculatory response to nicotine in frog web.

PubMed

Horimoto, M; Koyama, T

1982-01-01

Acute effects of nicotine (NC) on the microcirculation of frog webs were studied by measuring the blood flow velocity in arterioles, and by determining the diameter of both arterioles and venules. Simultaneous recordings of the ventricular pressure and heart rate were obtained in order to compute the vascular resistance and to interpret the changes in microcirculation. The web of right hindlimb was immersed in a solution of NC (2.6 to 3.4 mg/ml) for 4 min. Blood flow velocity in web arterioles of left hindlimb was measured by means of a laser Doppler microscope. Internal diameters of web microvessels were determined using a micrometer on the ocular lens of the microscope. Mean flow velocity (MV) and pulsatile amplitude (PA) were calculated from the pulsatile flow-velocity contour for each vessel. Both MV and PA were increased after the immersion of the web in NC solution. Although the magnitude of the increment in MV was proportional to that in ventricular pressure, the vasodilation of both arterioles and venules and the flow rate in arterioles higher than the initial state continued even after the ventricular pressure had returned to the initial control value. Calculation of the relative change in vascular resistance in web arterioles following NC administration suggested a vasodilator response to NC. Furthermore, our results indicate that sufficient NC can be absorbed across the web epithelium to produce a systemic vascular response when the concentration of NC in the bathing solution is 2.6 mg/ml.

Effects of core retrieval, handling, and preservation on hydrate-bearing samples

NASA Astrophysics Data System (ADS)

Kneafsey, T. J.; Lu, H.; Winters, W. J.; Hunter, R. B.

2009-12-01

Recovery, preservation, storage, and transport of samples containing natural gas hydrate cause changes in the stress conditions, temperature, pressure, and hydrate saturation of samples. Sample handling at the ground surface and sample preservation, either by freezing in liquid nitrogen (LN) or repressurization using methane, provides additional time and driving forces for sample alteration. The extent to which these disturbances alter the properties of the hydrate bearing sediments (HBS) depend on specific sample handling techniques, as well as on the sample itself. HBS recovered during India’s National Gas Hydrate Program (NGHP) Expedition 01 and the 2007 BP Exploration Alaska - Department of Energy - U.S. Geological Survey (BP-DOE-USGS) Mount Elbert (ME) gas hydrate well on the Alaskan North Slope provide comparisons of sample alterations induced by multiple handling techniques. HBS samples from the NGHP and the ME projects were examined using x-ray computed tomography. Mount Elbert sand samples initially preserved in LN have non-uniform short “crack-like” low-density zones in the center that probably do not extend to the outside perimeter. Samples initially preserved by repressurization show fewer “crack-like” features and higher densities. Two samples were analyzed in detail by Lu and coworkers showing reduced hydrate saturations approaching the outer surface, while substantial hydrate remained in the central region. Non-pressure cored NGHP samples show relatively large altered regions approaching the core surface, while pressure-cored-liquid-nitrogen preserved samples have much less alteration.

Microstructure evolution and tensile properties of Zr-2.5 wt.% Nb pressure tubes processed from billets with different microstructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapoor, K.; Saratchandran, N.; Muralidharan, K.

1999-02-01

Pressurized heavy water reactors (PHWR) use zirconium-base alloys for their low neutron-absorption cross section, good mechanical strength, low irradiation creep, and high corrosion resistance in reactor atmospheres. Starting with identical ingots, billets having different microstructures were obtained by three different processing methods for fabrication of Zr-2.5 wt%Nb pressure tubes., The billets were further processed by hot extrusion and cold Pilger tube reducing to the finished product. Microstructural characterization was done at each stage of processing. The effects of the initial billet microstructure on the intermediate and final microstructure and mechanical property results were determined. It was found that the structuremore » at each stage and the final mechanical properties depend strongly on the initial billet microstructure. The structure at the final stage consists of elongated alpha zirconium grains with a network of metastable beta zirconium phase. Some of this metastable phase transforms into stable beta niobium during thermomechanical processing. Billets with quenched structure resulted in less beta niobium at the final stage. The air cooled billets resulted in a large amount of beta niobium. The tensile properties, especially the percentage elongation, were found to vary for the different methods. Higher percentage elongation was observed for billets having quenched structure. Extrusion and forging did not produce any characteristic differences in the properties. The results were used to select a process flow sheet which yields the desired mechanical properties with suitable microstructure in the final product.« less

Aspects of Supercritical Turbulence: Direct Numerical Simulation of O2/H2 and C7H16/N2 Temporal Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, J.; Okongo, N. A.; Harstad, K. G.; Hutt, John (Technical Monitor)

2002-01-01

Results from Direct Numerical Simulations of temporal, supercritical mixing layers for two species systems are analyzed to elucidate species-specific turbulence aspects. The two species systems, O2/H2 and C7HG16/N2, have different thermodynamic characteristics; thus, although the simulations are performed at similar reduced pressure (ratio of the pressure to the critical pressure), the former system is dose to mixture ideality and has a relatively high solubility with respect to the latter, which exhibits strong departures from mixture ideality Due to the specified, smaller initial density stratification, the C7H16/N2 layers display higher growth and increased global molecular mixing as well as larger turbulence levels. However, smaller density gradients at the transitional state for the O2/H2 system indicate that on a local basis, the layer exhibits an enhanced mixing, this being attributed to the increased solubility and to mixture ideality. These thermodynamic features are shown to affect the irreversible entropy production (i.e. the dissipation), which is larger for the O2/H2 layer and is primarily concentrated in high density-gradient magnitude regions that are distortions of the initial density stratification boundary. In contrast, the regions of largest dissipation in the C7H16/N2 layer are located in high density-gradient magnitude regions resulting from the mixing of the two fluids.

Understanding Combustion of H2/O2 Gases inside Nanobubbles Generated by Water Electrolysis Using Reactive Molecular Dynamic Simulations.

PubMed

Jain, S; Qiao, L

2018-06-21

This work explored the mechanism of spontaneous combustion of hydrogen-oxygen mixtures inside nanobubbles (which were generated by water electrolysis) using reactive molecular dynamic simulations based on the first-principles derived reactive force field ReaxFF. The effects of surface-assisted dissociation of H 2 and O 2 gases that produced H and O radicals were examined. Additionally, the ignition outcome and species evolution as a function of the initial system pressure (or bubble size) were studied. A significant amount of hydrogen peroxide (H 2 O 2 ), 6-140 times water (H 2 O), was observed in the combustion products. This was attributed to the low-temperature (∼300 K) and high-pressure (2-80 atm) conditions at which the chemical reactions were taking place. In addition, the rate of consumption of H 2 and O 2 molecules was found to increase with an increase in added H and O radical concentrations and initial system pressure. The rate at which heat was being lost from the combustion chamber (nanobubbles) was also compared to the rate at which heat was being released from the chemical reactions. Only a slight rise in the reaction temperature was observed (∼68 K), signifying that, at such small scales, heat losses dominate. The resulting chemistry was quite different from macroscopic combustion, which usually takes place at a much higher temperatures of above 1000 K.

Experimental study on a prototype of heat pipe solar water heater using refrigerant R134a as a transfer fluid

NASA Astrophysics Data System (ADS)

Sitepu, T.; Sembiring, J.; Ambarita, H.

2018-02-01

A prototype of a solar water heater by using refrigerant as a heat transfer fluid is investigated experimentally. The objective is to explore the characteristics and the performance of the prototype. To make heat transfer from the collector to the heated fluid effectively, refrigerant R134a is used as a transfer. In the experiments, the initial pressure inside the heat pipe is varied. The prototype is exposed to solar irradiation in a location in Medan city for three days of the experiment. Solar collector temperatures, solar radiation, water temperature, and ambient temperature are measured. The efficiency of the system is analyzed. The results show that temperature of the hot water increases as the initial pressure of the working fluid increase. However, the increasing is not linear, and there must exist an optimum initial pressure. For the case with the refrigerant pressure of 110 psi, the maximum hot water temperature and maximum thermal efficiency are 45.36oC and 53.23%, respectively. The main conclusion can be drawn here is that solar water heater by using refrigerant R134a should be operated at initial pressure 110 psi.

A study of fiber volume fraction effects in notched unidirectional SCS-6/Ti-15V-3Cr-3Al-3Sn composite. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Covey, Steven J.

1993-01-01

Notched unidirectional SCS-6/Ti-15-3 composite of three different fiber volume fractions (vf = 0.15, 0.37, and 0.41) was investigated for various room temperature microstructural and material properties including: fatigue crack initiation, fatigue crack growth, and fracture toughness. While the matrix hardness is similar for all fiber volume fractions, the fiber/matrix interfacial shear strength and matrix residual stress increases with fiber volume fraction. The composite fatigue crack initiation stress is shown to be matrix controlled and occurs when the net maximum matrix stress approaches the endurance limit stress of the matrix. A model is presented which includes residual stresses and presents the composite initiation stress as a function of fiber volume fraction. This model predicts a maximum composite initiation stress at vf approximately 0.15 which agrees with the experimental data. The applied composite stress levels were increased as necessary for continued crack growth. The applied Delta(K) values at crack arrest increase with fiber volume fraction by an amount better approximated using an energy based formulation rather than when scaled linear with modulus. After crack arrest, the crack growth rate exponents for vf37 and vf41 were much lower and toughness much higher, when compared to the unreinforced matrix, because of the bridged region which parades with the propagating fatigue crack. However, the vf15 material exhibited a higher crack growth rate exponent and lower toughness than the unreinforced matrix because once the bridged fibers nearest the crack mouth broke, the stress redistribution broke all bridged fibers, leaving an unbridged crack. Degraded, unbridged behavior is modeled using the residual stress state in the matrix ahead of the crack tip. Plastic zone sizes were directly measured using a metallographic technique and allow prediction of an effective matrix stress intensity which agrees with the fiber pressure model if residual stresses are considered. The sophisticated macro/micro finite element models of the 0.15 and 0.37 fiber volume fractions presented show good agreement with experimental data and the fiber pressure model when an estimated effective fiber/matrix debond length is used.

The incidence of pressure ulcer in patients on mechanical ventilation andeffects of selected risk factors on pressure ulcer development.

PubMed

Karayurt, Özgül; Akyol, Özay; Kılıçaslan, Necmiye; Akgün, Nuray; Sargın, Ümran; Kondakçı, Melike; Ekinci, Hanım; Sarı, Neslihan

2016-11-17

This study aimed to determine the incidence of pressure ulcers in patients on mechanical ventilation and selected risk factors likely to play a role in pressure ulcer development. The study included 110 patients recruited from an anesthesia critical care unit of a university hospital. Data were collected with a demographic and clinical characteristics form. The form was composed of questions about demographic characteristics and clinical features including diagnosis, duration of mechanical ventilation, general well-being, oxygenation, perfusion, and skin condition. The incidence of pressure ulcer was 15.5%. Duration of mechanical ventilation was longer and the body mass index was higher in patients developing pressure ulcers than in those without pressure ulcers. Additionally, 90.11% of patients with pressure ulcers had edema and 82.35% of patients with pressure ulcers received vasopressin. The patients with pressure ulcers had higher PH levels, lower PaO2 levels, higher PCO2 levels, lower SaO2 levels, and higher urine output. It can be recommended that nurses and other health professionals should be aware of factors playing a role in pressure ulcer development and should be able to conduct appropriate interventions to prevent pressure ulcers.

An Evaluation of Surgical Functional Reconstruction of the Foot Using Kinetic and Kinematic Systems: A Case Report.

PubMed

Jordán-Palomar, Elena Irene; Javierre, Etelvina; Rey-Vasalo, José; Alfaro-Santafé, Víctor; Gómez-Benito, María José

Most pedobarographic studies of microsurgical foot reconstruction have been retrospective. In the present study, we report the results from a prospective pedobarographic study of a patient after microsurgical reconstruction of her foot with a latissimus dorsi flap and a cutaneous paddle, with a 42-month follow-up period. We describe the foot reconstruction plan and the pedobarographic measurements and analyzed its functional outcome. The goal of the present study was to demonstrate that pedobarography could have a role in the treatment of foot reconstruction from a quantitative perspective. The pedobarographic measurements were recorded after the initial coverage surgery and 2 subsequent foot remodeling procedures. A total of 4 pedobarographic measurements and 2 gait analyses were recorded and compared for both the noninvolved foot and the injured foot. Furthermore, the progress of the reconstructed foot was critically evaluated using this method. Both static and dynamic patterns were compared at subsequent follow-up visits after the foot reconstruction. The values and progression of the foot shape, peak foot pressure (kPa), average foot pressure (kPa), total contact surface (cm 2 ), loading time (%), and step time (ms) were recorded. Initially, the pressure distribution of the reconstructed foot showed higher peak values at nonanatomic locations, revealing a greater ulceration risk. Over time, we found an improvement in the shape and values of these factors in the involved foot. To homogenize the pressure distribution and correct the imbalance between the 2 feet, patient-specific insoles were designed and fabricated. In our patient, pedobarography provided an objective, repeatable, and recordable method for the evaluation of the reconstructed foot. Pedobarography can therefore provide valuable insights into the prevention of pressure ulcers and optimization of rehabilitation. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Blood Pressure, Perfusion Pressure, and Open-Angle Glaucoma: The Los Angeles Latino Eye Study

PubMed Central

Memarzadeh, Farnaz; Ying-Lai, Mei; Chung, Jessica; Azen, Stanley P.

2010-01-01

Purpose. To examine the cross-sectional relationship between blood pressure, perfusion pressure, and prevalence of open angle glaucoma (OAG) in an adult Latino population. Methods. Participants aged 40 years and older (N = 6130) from the Los Angeles Latino Eye Study (LALES), a large, population-based study of self-identified adult Latinos, underwent an interviewer-administered questionnaire and a complete ocular and clinical examination. Logistic regression was used to evaluate the covariate-adjusted association of OAG with systolic, diastolic, and mean blood pressures and perfusion pressures. Covariates included age, intraocular pressure, history of glaucoma treatment including medications and surgery, and history of blood pressure and treatment of blood pressure including use of medications. Results. Low systolic (odds ratio [OR] = 2.5), diastolic (OR = 1.9), and mean (OR = 3.6) perfusion pressures and low diastolic blood pressure (OR = 1.9) were associated with a higher prevalence of OAG in LALES participants. Higher systolic blood pressure and mean arterial blood pressure were associated with a higher prevalence of OAG. There was no relationship between the prevalence of OAG and the presence of a history of cardiovascular disease. Conclusions. Low diastolic, systolic and mean perfusion pressures, low diastolic blood pressure, and high systolic and mean arterial blood pressures are associated with a higher prevalence of OAG in adult Latinos. PMID:20089880

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Sewram, V; Nair, J J; Nieuwoudt, T W; Leggott, N L; Shephard, G S

2000-11-03

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.

Determinants for adherence to continuous positive airway pressure therapy in obstructive sleep apnea

PubMed Central

Eriksen, Freja; Hansen, Rasmus Würgler; Erlandsen, Mogens; Thorup, Line; Damgård, Mette Bjerre; Kirkegaard, Martin Glümer; Hansen, Klavs Würgler

2017-01-01

Background Continuous positive airway pressure (CPAP) therapy is an efficacious treatment for patients diagnosed with obstructive sleep apnea (OSA). However, there are only few data on long-term adherence. The aim of this study is to quantify the extent of non-adherence and describe the clinical characteristics. Methods A retrospective study including 695 patients with newly diagnosed OSA and prescribed CPAP therapy within an inclusion period of 14 months. All patients were offered free of charge individually adjusted CPAP therapy. Data on comorbidity, medication, BMI and Epworth Sleepiness Score (ESS) were obtained by questionnaires and consultation with an otorhinolaryngeal specialist. Results The median follow-up time after initiating CPAP therapy was 3.0 (range 2.4–3.6) years. An adherence rate of 89% was found for severe OSA, 71% for moderate OSA and 55% for mild OSA. 18% initiated humidification. Patients adherent to CPAP had a significantly higher Body Mass Index (BMI), Apnea Hypopnea Index (AHI), Oxygen Desaturation Index (ODI) and ESS compared to non-adherent patients. Furthermore, adherence was associated with a higher frequency of observed interrupted breathing, a less frequent use of hypnotic drugs, fewer smokers, and they were more often offered humidification. Age, gender and comorbidity were not significantly associated with adherence. In a Cox model only AHI (Hazard Ratio (HR) 0.963, p < 0.001), ESS (HR 0.939, p = 0.001) and smoking (HR 1.576, p = 0.022) were independently associated with CPAP non-adherence. Conclusions The severity of OSA, subjective daytime sleepiness and smoking status are independently related to adherence to CPAP therapy. PMID:29253872

Ventless pressure control of two-phase propellant tanks in microgravity.

PubMed

Kassemi, Mohammad; Panzarella, Charles H

2004-11-01

This work studies pressurization and pressure control of a large liquid hydrogen storage tank. A finite element model is developed that couples a lumped thermodynamic formulation for the vapor region with a complete solution of the Navier-Stokes and energy equations for the flow and temperature fields in the liquid. Numerical results show that buoyancy effects are strong, even in microgravity, and can reposition a vapor bubble that is initially at the center of the tank to a region near the tank wall in a relatively short time. Long-term tank pressurization with the vapor bubble at the tank wall shows that after an initial transient lasting about a week, the final rate of pressure increase agrees with a purely thermodynamic analysis of the entire tank. However, the final pressure levels are quite different from thermodynamic predictions. Numerical results also show that there is significant thermal stratification in the liquid due to the effects of natural convection. A subcooled jet is used to provide simultaneous cooling and mixing in order to bring the tank pressure back down to its initial value. Three different jet speeds are examined. Although the lowest jet speed is ineffective at controlling the pressure because of insufficient penetration into the liquid region, the highest jet speed is shown to be quite effective at disrupting thermal stratification and reducing the tank pressure in reasonable time.

Ventless pressure control of two-phase propellant tanks in microgravity

NASA Technical Reports Server (NTRS)

Kassemi, Mohammad; Panzarella, Charles H.

2004-01-01

This work studies pressurization and pressure control of a large liquid hydrogen storage tank. A finite element model is developed that couples a lumped thermodynamic formulation for the vapor region with a complete solution of the Navier-Stokes and energy equations for the flow and temperature fields in the liquid. Numerical results show that buoyancy effects are strong, even in microgravity, and can reposition a vapor bubble that is initially at the center of the tank to a region near the tank wall in a relatively short time. Long-term tank pressurization with the vapor bubble at the tank wall shows that after an initial transient lasting about a week, the final rate of pressure increase agrees with a purely thermodynamic analysis of the entire tank. However, the final pressure levels are quite different from thermodynamic predictions. Numerical results also show that there is significant thermal stratification in the liquid due to the effects of natural convection. A subcooled jet is used to provide simultaneous cooling and mixing in order to bring the tank pressure back down to its initial value. Three different jet speeds are examined. Although the lowest jet speed is ineffective at controlling the pressure because of insufficient penetration into the liquid region, the highest jet speed is shown to be quite effective at disrupting thermal stratification and reducing the tank pressure in reasonable time.

Mechanism of sand slide - cold lahar induced by extreme rainfall

NASA Astrophysics Data System (ADS)

Fukuoka, Hiroshi; Yamada, Masumi; Dok, Atitkagna

2014-05-01

Along with the increasing frequencies of extreme rainfall events in almost every where on the earth, shallow slide - debris flow, i.e. cold lahars running long distance often occurs and claims downslope residents lives. In the midnight of 15 October 2013, Typhoon Wilpha attacked the Izu-Oshima, a active volcanic Island and the extreme rainfall of more than 800 mm / 24 hours was recorded. This downpour of more than 80 mm/hr lasted 4 hours at its peak and caused a number of cold lahars. The initial stage of those lahars was shallow slides of surface black volcanic ash deposits, containing mostly fine sands. The thickness was only 50 cm - 1 m. In the reconnaissance investigation, author found that the sliding surface was the boundary of two separate volcanic ash layers between the black and yellow colored and apparently showing contrast of permeability and hardness. Permeability contrast may have contributed to generation of excess pore pressure on the border and trigger the slide. Then, the unconsolidated, unpacked mass was easily fluidized and transformed into mud flows, that which volcanologists call cold lahars. Seismometers installed for monitoring the active volcano's activities, succeeded to detect many tremors events. Many are spikes but 5 larger and longer events were extracted. They lasted 2 -3 minutes and if we assume that this tremors reflects the runout movement, then we can calculate the mean velocity of the lahars. Estimated velocity was 45 - 60 km/h, which is much higher than the average speed 30 - 40 km/h of debris flows observed in Japan. Flume tests of volcanic ash flows by the Forestry and Forest Products Research Institute showed the wet volcanic ash can run at higher speed than other materials. The two tremor records were compare d with the local residents witnessed and confirmed by newspaper reported that the reach of the lahar was observed at the exact time when tremor ends. We took the black volcanic ash and conducted ring shear tests to reveal the mechanism of rapid motion. In the undrained or partially drained tests under pore water pressure test, monotonic loading of shear stress, and constant shear speed conditions, we found that immediately after failure takes place, a big excess pore pressure was generated and accelerating motions had stated in all cases. The reduced shear resistance thereafter was maintained because of the lasting high pore pressure. Even in the partially-drained test, we found once the pore pressure reached almost same with the normal stress and then gradually decreased due to dissipation. Those tests apparently shows that the high mobility and high acceleration of the motion are expected and this could be the key mechanism of the fluidization of initial shallow slides into sand flows, i.e., cold lahars. In the past ring shear test series on volcanic materials from fluidized landslides at El Picaccho of El Salvador, Mt Aso of Kumamto Prefecture, and Nagari Tandikat near Padang, Indonesia, show very similar trends. In all those cases, we expected serious grain crushing during shear, contributed to the generation of excess pore pressure, because those material are deposited recently (in geological time) and suffered no big overburden pressure which means no consolidation and no serious grain crushing ever before. So those volcanic materials are generally susceptible to crushing and expect high mobility when slides are initiated under fully saturated condition.

Under Pressure: Financial Effect of the Hospital-Acquired Conditions Initiative-A Statewide Analysis of Pressure Ulcer Development and Payment.

PubMed

Meddings, Jennifer; Reichert, Heidi; Rogers, Mary A M; Hofer, Timothy P; McMahon, Laurence F; Grazier, Kyle L

2015-07-01

To assess the financial effect of the 2008 Hospital-Acquired Conditions Initiative (HACI) pressure ulcer payment changes on Medicare, other payers, and hospitals. Retrospective before-and-after study of all-payer statewide administrative data for more than 2.4 million annual adult discharges in 2007 and 2009 using the Healthcare Cost and Utilization Project State Inpatient Datasets for California. How often and by how much the 2008 payment changes for pressure ulcers affected hospital payment was assessed. Nonfederal acute care California hospitals (N = 311). Adults discharged from acute-care hospitals. Pressure ulcer rates and hospital payment changes. Hospital-acquired pressure ulcer rates were low in 2007 (0.28%) and 2009 (0.27%); present-on-admission pressure ulcer rates increased from 2.3% in 2007 to 3.0% in 2009. According to clinical stage of pressure ulcer (available in 2009), hospital-acquired Stage III and IV ulcers occurred in 603 discharges (0.02%); 60,244 discharges (2.42%) contained other pressure ulcer diagnoses. Payment removal for Stage III and IV hospital-acquired ulcers reduced payment in 75 (0.003%) discharges, for a statewide payment decrease of $310,444 (0.001%) for all payers and $199,238 (0.001%) for Medicare. For all other pressure ulcers, the Hospital-Acquired Conditions Initiative reduced hospital payment in 20,246 (0.81%) cases (including 18,953 cases with present-on-admission ulcers), reducing statewide payment by $62,538,586 (0.21%) for all payers and $47,237,984 (0.32%) for Medicare. The total financial effect of the 2008 payment changes for pressure ulcers was negligible. Most payment decreases occurred by removal of comorbidity payments for present-on-admission pressure ulcers other than Stages III and IV. The removal of payment for hospital-acquired Stage III and IV ulcers by implementation of the HACI policy was 1/200th that of the removal of payment for other types of pressure ulcers that occurred in implementation of the Hospital-Acquired Conditions Initiative. © 2015, Copyright the Authors Journal compilation © 2015, The American Geriatrics Society.

The optimal pressure for initial flush with UW solution in heart procurement.

PubMed

Mohara, Jun; Tsutsumi, Hirofumi; Takeyoshi, Izumi; Tokumine, Masahiko; Aizaki, Masahiro; Ishikawa, Susumu; Matsumoto, Koshi; Morishita, Yasuo

2002-03-01

University of Wisconsin (UW) solution is widely used in organ preservation. Some investigators have reported that high pressure during initial flush with UW solution may induce vasoconstriction and endothelial damage, because of its high potassium content and high viscosity. However, using lower pressure during the initial flush may lead to irregular distribution of the solution and incomplete flushing of blood components from coronary vascular beds. This experimental study evaluated the effects of a range of initial flush pressures during heart procurement, followed by orthotopic transplantation of the graft after 12 hours of preservation. Twelve pairs of adult mongrel dogs, weighing 9 to 14 kg, formed the recipient-donor combinations. After determining hemodynamic status by measuring cardiac output, left ventricular pressure (LVP), and maximum positive and negative change in LVP (+/-LVdP/dt), donor hearts were excised. Coronary vascular beds were flushed with 4 degrees C UW solution at a pressure of 60 mm Hg in the low-pressure group (n = 6) and at 120 mm Hg in the high-pressure group (n = 6). After 12 hours of cold preservation, orthotopic transplantation was performed using cardiopulmonary bypass (CPB). The hemodynamics of the transplanted graft were assessed by comparing recovery rates (%) from donor hearts 2 hours after weaning from CPB. Endothelin-1 (ET-1) levels were measured in the blood obtained from the coronary sinus 30 minutes after reperfusion. The transplanted grafts were then harvested for histologic study and measurement of adenosine triphosphate (ATP) content. Cardiac output, LVP, LVdP/dt and myocardial tissue ATP content were significantly better (p < 0.05) in the high-pressure group than in the low-pressure group. We found no significant differences in ET-1 levels between the groups. Transmission electron microscopic findings revealed that degeneration of the mitochondria was less extensive in the high-pressure group than in the low-pressure group. We observed no obvious ultrastructural damage to the endothelial cells in either group. When using UW solution in heart procurement, high pressure is better to completely wash out the blood components and distribute the solution.

{Linking permeability and mechanical damage for basalt from Mt Etna Volcano, Italy}

NASA Astrophysics Data System (ADS)

Faoro, I.; Vinciguerra, S.; Marone, C.; Elsworth, D.

2009-04-01

Volcanic edifices, such as Mt. Etna volcano (Italy), are affected from repeated episodes of pressurisation due to magma emplacement from deep reservoirs to shallow depths. This mechanism pressurizes the large aquifers within the edifice and increases the level of crack damage within the rocks of the edifice over extended periods of times. In order to improve our understanding of the complex coupling between circulating fluids and the development of crack damage, we performed flow-through tests using cylindrical cores of Etna Basalt (Etna, Italy) to evaluate permeabilty changes as a function of approach to failure under non-hydrostatic stresses at confining pressures from 5 to 60 MPa. Samples were loaded to failure by increasing increments of axial stress or by cyclic stresses of increasing amplitude. Both intact samples and pre-drilled samples (1.18mm) were tested. Under hydrostatic stresses, the permeability values of the intact sample decrease linearly with the increments of pressure and range between 5.2*10-17 m2and 1.5*10-17m2Under non-hydrostatic conditions, at low deviatoric stresses from (up to 18 MPa), the permeability values ranged between 5.5*10-17 m2and 4*10-17m2 and tended to completely recover the initial value each time the sample was unloaded, indicating an elastic regime. At higher deviatoric stresses (up to 60 MPa) the permeability values range between 2*10-17 m2 and 0.6*10-17m2. We hypothesize that from 5MPa to 40MPa axial stress, anelastic deformation mechanisms start to occur, with progressive pore collapse and opening of microfractures, resulting in a change of permeability. Under incremental uniaxial cyclic loading up to peak stresses of 160 MPa permeability decreases up to 2 orders of magnitude from initial values of 1*10-15 m2 to 2*10-14m2 Higher initial permeability values are related to the presence of an open fracture in the sample. We interpreted the reduction as a result of progressive closure of the voids space, as the axial load is incremented. Overall it is shown that permeability on Etna basalt rocks is strongly dependent on the loading conditions. Ongoing work is expected to elucidate the mechanisms relating increasing damage mechanical damage to changes of permeability.

Particle behavior and char burnout mechanisms under pressurized combustion conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.

Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was tomore » provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.« less

Response of the arterial blood pressure of quadriplegic patients to treadmill gait training.

PubMed

Carvalho, D C L; Cliquet, A

2005-09-01

Blood pressure pattern was analyzed in 12 complete quadriplegics with chronic lesions after three months of treadmill gait training. Before training, blood pressure values were obtained at rest, during treadmill walking and during the recovery phase. Gait training was performed for 20 min twice a week for three months. Treadmill gait was achieved using neuromuscular electrical stimulation, assisted by partial body weight relief (30-50%). After training, blood pressure was evaluated at rest, during gait and during recovery phase. Before and after training, mean systolic blood pressures and heart rates increased significantly during gait compared to rest (94.16 +/- 5.15 to 105 +/- 5.22 mmHg and 74.27 +/- 10.09 to 106.23 +/- 17.31 bpm, respectively), and blood pressure decreased significantly in the recovery phase (86.66 +/- 9.84 and 57.5 +/- 8.66 mmHg, respectively). After three months of training, systolic blood pressure became higher at rest (94.16 +/- 5.15 mmHg before training and 100 +/- 8.52 mmHg after training; P < 0.05) and during gait exercise (105 +/- 5.22 mmHg before and 110 +/- 7.38 mmHg after training; P < 0.05) when compared to the initial values, with no changes in heart rate. No changes occurred in blood pressure during the recovery phase, with the lower values being maintained. A drop in systolic pressure from 105 +/- 5.22 to 86.66 +/- 9.84 mmHg before training and from 110 +/- 7.38 to 90 +/- 7.38 mmHg after training was noticed immediately after exercise, thus resulting in hypotensive symptoms when chronic quadriplegics reach the sitting position from the upright position.

Active and Inactive Leg Hemodynamics during Sequential Single-Leg Interval Cycling.

PubMed

Gordon, Nicole; Abbiss, Chris R; Ihsan, Mohammed; Maiorana, Andrew J; Peiffer, Jeremiah J

2018-06-01

Leg order during sequential single-leg cycling (i.e., exercising both legs independently within a single session) may affect local muscular responses potentially influencing adaptations. This study examined the cardiovascular and skeletal muscle hemodynamic responses during double-leg and sequential single-leg cycling. Ten young healthy adults (28 ± 6 yr) completed six 1-min double-leg intervals interspersed with 1 min of passive recovery and, on a separate occasion, 12 (six with one leg followed by six with the other leg) 1-min single-leg intervals interspersed with 1 min of passive recovery. Oxygen consumption, heart rate, blood pressure, muscle oxygenation, muscle blood volume, and power output were measured throughout each session. Oxygen consumption, heart rate, and power output were not different between sets of single-leg intervals, but the average of both sets was lower than the double-leg intervals. Mean arterial pressure was higher during double-leg compared with sequential single-leg intervals (115 ± 9 vs 104 ± 9 mm Hg, P < 0.05) and higher during the initial compared with second set of single-leg intervals (108 ± 10 vs 101 ± 10 mm Hg, P < 0.05). The increase in muscle blood volume from baseline was similar between the active single leg and the double leg (267 ± 150 vs 214 ± 169 μM·cm, P = 0.26). The pattern of change in muscle blood volume from the initial to second set of intervals was significantly different (P < 0.05) when the leg was active in the initial (-52.3% ± 111.6%) compared with second set (65.1% ± 152.9%). These data indicate that the order in which each leg performs sequential single-leg cycling influences the local hemodynamic responses, with the inactive muscle influencing the stimulus experienced by the contralateral leg.

Racial discrimination associated with higher diastolic blood pressure in a sample of American Indian adults.

PubMed

Thayer, Zaneta M; Blair, Irene V; Buchwald, Dedra S; Manson, Spero M

2017-05-01

Hypertension prevalence is high among American Indians (AIs). AIs experience a substantial burden of interpersonal racial discrimination, which in other populations has been associated with higher blood pressure. The purpose of this study is to understand whether racial discrimination experiences are associated with higher blood pressure in AIs. We used the Everyday Discrimination Scale to evaluate the relationship between discrimination and measured blood pressure among 77 AIs from two reservation communities in the Northern Plains. We used multivariate linear regression to evaluate the association of racial discrimination with systolic and diastolic blood pressure, respectively. Racial discrimination, systolic blood pressure, and diastolic blood pressure were analyzed as continuous variables. All analyses adjusted for sex, waist circumference, age, posttraumatic stress disorder status, and education. We found that 61% of participants experienced discrimination that they attributed to their race or ancestry. Racial discrimination was associated with significantly higher diastolic blood pressure (β = 0.22, SE = 0.09, p = .02), and with a similar non-significant trend toward higher systolic blood pressure (β = 0.25, SE = 0.15, p = .09). The results of this analysis suggest that racial discrimination may contribute to higher diastolic blood pressure within Native communities. These findings highlight one pathway through which the social environment can shape patterns of biology and health in AI and other socially and politically marginalized groups. © 2017 Wiley Periodicals, Inc.

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel.

PubMed

Yang, Zixuan; Kan, Bo; Li, Jinxu; Qiao, Lijie; Volinsky, Alex A; Su, Yanjing

2017-11-14

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance.

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel

PubMed Central

Yang, Zixuan; Kan, Bo; Li, Jinxu; Su, Yanjing; Qiao, Lijie; Volinsky, Alex A.

2017-01-01

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance. PMID:29135912

Hydrogen gas storage in fluorinated ultramicroporous tunnel crystal

NASA Astrophysics Data System (ADS)

Kataoka, Keisuke; Katagiri, Toshimasa

2012-07-01

We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder.We report hydrogen storage at an ordinary pressure due to a bottle-neck effect of an ultramicroporous crystal. Stored hydrogen was kept at an ordinary pressure below -110 °C. The amounts of stored hydrogen gas linearly correlated with the initial pressures. These phenomena suggested the ultramicroporous tunnels worked as a molecular gas cylinder. Electronic supplementary information (ESI) available. CCDC 246922. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30940h

White-Coat Hypertension: When Blood Pressure Rises at the Doctor's Office

MedlinePlus

... blood pressure rises at the doctor's office My blood pressure is always higher in the doctor's office than it is at home. ... coat hypertension. White coat hypertension occurs when the blood pressure readings at your doctor's office are higher than ...

The Edgecombe County (NC) High Blood Pressure Control Program: II. Barriers to the use of medical care among hypertensives.

PubMed Central

James, S A; Wagner, E H; Strogatz, D S; Beresford, S A; Kleinbaum, D G; Williams, C A; Cutchin, L M; Ibrahim, M A

1984-01-01

As the initial step in a five-year project to improve control of high blood pressure in Edgecombe County, North Carolina, a survey was conducted in 1980 to determine the prevalence of hypertension and to identify factors which might constitute barriers to the use of medical care by hypertensives. This report summarizes the findings for the 539 hypertensives identified through the baseline survey. In general, Black hypertensives reported more access problems than Whites. Within race, however, males and females differed very little on selected measures of potential access to medical care. Among women, lower scores on potential access were strongly associated with being untreated, whereas for men, concerns about the safety of anti-hypertensive drug therapy were associated with being unaware. On a summary measure of the actual use of medical care in response to symptoms, both male and female treated hypertensives scored higher than their untreated counterparts. The implications of these and other findings for community-based blood pressure control activities are discussed. PMID:6711721

Using second-sound shock waves to probe the intrinsic critical velocity of liquid helium II

NASA Technical Reports Server (NTRS)

Turner, T. N.

1983-01-01

A critical velocity truly intrinsic to liquid helium II is experimentally sought in the bulk fluid far from the apparatus walls. Termed the 'fundamental critical velocity,' it necessarily is caused by mutual interactions which operate between the two fluid components and which are activated at large relative velocities. It is argued that flow induced by second-sound shock waves provides the ideal means by which to activate and isolate the fundamental critical velocity from other extraneous fluid-wall interactions. Experimentally it is found that large-amplitude second-sound shock waves initiate a breakdown in the superfluidity of helium II, which is dramatically manifested as a limit to the maximum attainable shock strength. This breakdown is shown to be caused by a fundamental critical velocity. Secondary effects include boiling for ambient pressures near the saturated vapor pressure or the formation of helium I boundary layers at higher ambient pressures. When compared to the intrinsic critical velocity discovered in highly restricted geometries, the shock-induced critical velocity displays a similar temperature dependence and is the same order of magnitude.

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams.

PubMed

Feng, Chao-Hui; Drummond, Liana; Zhang, Zhi-Hang; Sun, Da-Wen

2013-10-01

The effects of agitation (1002 rpm), different pressure reduction rates (60 and 100 mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20°C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6°C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P>0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60 mbar/min (not statistically significant, P>0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality. Copyright © 2013 Elsevier Ltd. All rights reserved.

Production of ZrC Matrix for Use in Gas Fast Reactor Composite Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevamurthy, Gokul; Knight, Travis W.; Roberts, Elwyn

2007-07-01

Zirconium carbide is being considered as a candidate for inert matrix material in composite nuclear fuel for Gas fast reactors due to its favorable characteristics. ZrC can be produced by the direct reaction of pure zirconium and graphite powders. Such a reaction is exothermic in nature. The reaction is self sustaining once initial ignition has been achieved. The heat released during the reaction is high enough to complete the reaction and achieve partial sintering without any external pressure applied. External heat source is required to achieve ignition of the reactants and maintain the temperature close to the adiabatic temperature tomore » achieve higher levels of sintering. External pressure is also a driving force for sintering. In the experiments described, cylindrical compacts of ZrC were produced by direct combustion reaction. External induction heating combined with varying amounts of external applied pressure was employed to achieve varying degrees of density/porosity. The effect of reactant particle size on the product characteristics was also studied. The samples were characterized for density/porosity, composition and microstructure. (authors)« less

Flow measurements in two cambered vane diffusers with different passage widths

NASA Astrophysics Data System (ADS)

Stein, W.; Rautenberg, M.

1985-03-01

To investigate the influence of the vaneless space between impeller exit and the diffuser vanes, detailed flow measurements in two diffusers with the same vane geometry but different passage width are compared. The three-dimensional character of the flow changes between impeller exit and the entry to the two dimensional vanes depending on the shape of the shroud. After initial measurements with a constant area vaneless space, the width of the vaned diffuser was later on reduced by 10 percent. The compressor maps show increases in overall pressure rise and efficiency with the width reduction. To get further details of the flow field, measurements of the static pressure distribution at hub and shroud have been performed at several operation points for both diffusers. At the same points, the flow angle and total pressure distribution between hub and shroud upstream and downstream of the vanes have been measured with probes. The maximum efficiency of the narrow diffuser is nearly 2 percent higher than for the wide diffuser. The measurements give further details to explain this improvement.

Ignitability test method and apparatus

NASA Technical Reports Server (NTRS)

Bement, Laurence J. (Inventor); Bailey, James W. (Inventor); Schimmel, Morry L. (Inventor)

1989-01-01

An apparatus for testing ignitability of an initiator includes a body with a central cavity, initiator holder for holding the initiator over the central cavity of the body, an ignition material holder disposed in the central cavity of the body and a cavity facing the initiator holder which receives a measured quantity of ignition material to be ignited by the initiator and a chamber in communication with the cavity of the ignition material holder and the central cavity of the body. A measuring system for analyzing pressure characteristics is generated by ignition material by the initiator. The measuring system includes at least one transducer coupled to an oscillograph for recording pressure traces generated by ignition.

Ignitability test method and apparatus

NASA Technical Reports Server (NTRS)

Bement, Laurence J. (Inventor); Bailey, James W. (Inventor); Schimmel, Morry L. (Inventor)

1991-01-01

An apparatus for testing ignitability of an initiator includes a body having a central cavity, an initiator holder for holding the initiator over the central cavity of the body, an ignition material holder disposed in the central cavity of the body and having a cavity facing the initiator holder which receives a measured quantity of ignition material to be ignited by the initiator. It contains a chamber in communication with the cavity of the ignition material and the central cavity of the body, and a measuring system for analyzing pressure characteristics generated by ignition of the ignition material by the initiator. The measuring system includes at least one transducer coupled with an oscillograph for recording pressure traces generated by ignition.

Quantification of in situ pore pressure and stress in regions of low frequency earthquakes and anomalously low seismic velocity at the Nankai Trough

NASA Astrophysics Data System (ADS)

Kitajima, H.; Saffer, D. M.

2012-12-01

Recent seismic reflection and ocean bottom seismometer (OBS) studies reveal broad regions of low seismic velocity along the megathrust plate boundary of the Nankai subduction zone offshore SW Japan. These low velocity zones (LVZ's) extend to ~55 km from the trench, corresponding to depths of >~10 km below sea floor. Elevated pore pressure has been invoked as one potential cause of both the LVZ's and very low frequency earthquakes (VLFE) in the outer forearc. Here, we estimate the in-situ pore fluid pressure and stress state within these LVZ's by combining P-wave velocities (Vp) obtained from seismic reflection and OBS data with well-constrained empirical relations between (1) P-wave velocity and porosity; and (2) porosity and effective mean and differential stresses, defined by triaxial deformation tests on drill core samples of the incoming oceanic sediment. We used cores of Lower Shikoku Basin (LSB) hemipelagic mudstone (322-C0011B-19R-5, initial porosity of 43%), and Middle Shikoku Basin (MSB) tuffaceous sandstone (333-C0011D-51X-2, initial porosity of 46%) that have been recovered from IODP Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Site C0011 (~20 km seaward from the deformation front). Samples were loaded under a range of different stress paths including isotropic loading, triaxial compression, and triaxial extension. During the tests, all pressures, axial displacement, and pore volume change were continuously monitored; and ultrasonic velocity and permeability were measured at regular intervals. The relationship between Vp and porosity for LSB mudstone is independent of stress path, and is well fit by an empirical function derived by Hoffman and Tobin [2004] for LSB sediments sampled by drilling along Muroto transect, located ~150 km southwest of the NanTroSEIZE study area. The MSB sandstone exhibits slightly higher P-wave velocity than LSB mudstone at a given porosity. Based on our experimental results, and assuming that the sediments in the LVZ's are at shear failure defined by a critical state stress condition, we estimate that effective vertical stress in the LVZ ranges from 15 MPa at 13 km landward of the trench, to 41 MPa at a distance of 55 km. The maximum horizontal effective stress ranges from 41-124 MPa over this region. Excess pore fluid pressure ranges from 15-81 MPa, corresponding to modified pore pressure ratios, λ* of 0.44-0.73. If LVZ is composed dominantly of sandstones, both the effective vertical and horizontal stresses would be lower, and the excess pore pressure would be higher, with pore pressure ratios λ* = 0.31-0.90. Our results suggest that the sediments have been loaded under poorly drained conditions, and that pore fluids support ≥~53-91 % of the overburden stress along the base of the accretionary wedge across the outer forearc. The low effective stress should lead to a mechanically weak plate boundary, and is spatially correlated with well-located low-frequency earthquakes in the outer accretionary wedge. The heterogeneous distribution of inferred pore pressure also suggests that fluid sources and drainage are localized and possibly transient.

Experimental Analysis of the Role of Fluid Transport Properties in Fluid-Induced Fracture Initiation and Propagation

NASA Astrophysics Data System (ADS)

Boutt, D.; McPherson, B. J.; Cook, B. K.; Goodwin, L. B.; Williams, J. R.; Lee, M. Y.; Patteson, R.

2003-12-01

It is well known that pore fluid pressure fundamentally influences a rock's mechanical response to stress. However, most measures of the mechanical behavior of rock (e.g. shear strength, Young's modulus) do not incorporate, either explicitly or implicitly, pore fluid pressure or transport properties of rock. Current empirical and theoretical criteria that define the amount of stress a given body of rock can support before fracturing also lack a direct connection between fluid transport and mechanical properties. Our research goal is to use laboratory experimental results to elucidate correlations between rock transport properties and fracture behavior under idealized loading conditions. In strongly coupled fluid-solid systems the evolution of the solid framework is influenced by the fluid and vice versa. These couplings often result in changes of the bulk material properties (i.e. permeability and failure strength) with respect to the fluid's ability to move through the solid and the solids ability to transmit momentum. Feedbacks between fluid and solid framework ultimately play key roles in understanding the spatial and temporal evolution of the coupled fluid-solid system. Discretely coupled models of fluid and solid mechanics were developed a priori to design an experimental approach for testing the role of fluid transport parameters in rock fracture. The experimental approach consists of first loading a fluid saturated cylindrical rock specimen under hydrostatic conditions and then applying a differential stress such that the maximum stress is perpendicular to the cylinder long axis. At the beginning of the test the minimum stress and the fluid pressure are dropped at the same time such that the resulting difference in the initial fluid pressure and the final fluid pressure is greater than the final minimum stress. These loading conditions should produce a fluid driven tensile fracture that is perpendicular to the cylinder long axis. Initial analyses using numerical simulations with similar boundary conditions suggest that resulting fracture propagation rates and fracture spacing are controlled by the rocks hydraulic diffusivity. Modeled rocks with higher permeability had fractures with larger apertures, more localized deformation, and greater fracture spacing. Intuitively, these results are consistent with permeability controlling the time required for pressure to come to equilibrium with the new boundary conditions. Finally, more general goals of this research include using these core-scale experimental data and discrete simulation results to calibrate larger-scale, more traditional continuum models of geologic deformation.

The Superheat Phenomenon in the Combustion of Magnesium Particles

NASA Technical Reports Server (NTRS)

Shafirovich, E. IA.; Goldshleger, U. I.

1992-01-01

Magnesium is known to be a likely fuel for engines that could work in the CO2 atmospheres of Mars and Venus. The present paper reports temperature measurements of magnesium samples during combustion in CO2. The burning sample temperature increases with the decrease in the initial size. The temperature of the 1-mm samples is 300-400 K higher than the boiling point of magnesium. The stability of the superheated drop is explained by the presence of a porous shell on the surface. An attempt has been made to describe vaporization on the superheated drop by the Knudsen-Langmuir equation. During combustion at high-pressure fragment ejection of the flame is observed in high-speed motion pictures. This phenomenon is shown to be connected with the drop superheat. The repeated fracture of the outer shell formed in the flame ensures the complete burnout of metal particles at high pressure.

Radiation Pressure Cooling as a Quantum Dynamical Process

NASA Astrophysics Data System (ADS)

He, Bing; Yang, Liu; Lin, Qing; Xiao, Min

2017-06-01

One of the most fundamental problems in optomechanical cooling is how small the thermal phonon number of a mechanical oscillator can be achieved under the radiation pressure of a proper cavity field. Different from previous theoretical predictions, which were based on an optomechanical system's time-independent steady states, we treat such cooling as a dynamical process of driving the mechanical oscillator from its initial thermal state, due to its thermal equilibrium with the environment, to a stabilized quantum state of higher purity. We find that the stabilized thermal phonon number left in the end actually depends on how fast the cooling process could be. The cooling speed is decided by an effective optomechanical coupling intensity, which constitutes an essential parameter for cooling, in addition to the sideband resolution parameter that has been considered in other theoretical studies. The limiting thermal phonon number that any cooling process cannot surpass exhibits a discontinuous jump across a certain value of the parameter.

Immediate effects of 33 to 180 rad/min (60)Co exposure on performance and blood pressure in monkeys. Topical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruner, A.

1976-09-01

Four groups of monkeys received 1000 rads (60)Co at 33, 50, 75, or 180 rad/min wholebody irradiation while performing a delayed matching-to-sample task. Systematic dose rate effects were observed on performance and blood pressure within the initial 20 min postirradiation. The incidence and severity of performance decrement (PD) increased with higher dose rate. The appearance of postirradiation hypotension was systematically delayed and its rate of fall prolonged as dose rate was lower. The hypotension likewise appeared less deep with lower dose rate exposure. Based on the calculated cumulative dose absorbed at the time of symptom appearance two coactive thresholds weremore » proposed to exist: a total dose threshold of approximately 300 rads (midbody measurement), and a dose rate threshold of about 25 rad/min.« less

Regression analysis of traction characteristics of traction fluids

NASA Technical Reports Server (NTRS)

Loewenthal, S. H.; Rohn, D. A.

1983-01-01

Traction data for Santotrac 50 and TDF-88 over a wide range of operating conditions were analyzed. An eight term correlation equation to predict the maximum traction coefficient and a six term correlation equation to predict the initial slope of the traction curve were developed. The slope correlation was corrected for size effect considering the compliance of the disks. The effects of different operating conditions on the traction performance of each traction fluid were studied. Both fluids exhibited a loss in traction with increases in spin, but the losses with the TDF-88 fluid were not as severe as those with Santotrac 50. Overall, both fluids exhibited similar performance, showing an increase in traction with contact pressure up to about 2.0 GPa, and a reduction in traction with higher surface speeds up to about 100 m/sec. The apparent stiffness of the traction contact, that is, film disk combination, increases with contact pressure and decreases with speed.

The prevalence of hypertension in the Indian population of Durban.

PubMed

Seedat, Y K; Seedat, M A; Reddy, K

1978-07-01

In a random house-to-house study of 1 000 Indians the prevalence of essential hypertension according to the World Health Organization (WHO) criteria was 19% (females 22%; males 15%). The study revealed that the prevalence of hypertension was higher than in published data from India. Ethnicity in our study caused a significant variation in prevalence. Prevalence was lower than in our urban Zulu study. Blood pressure rose with age, but there was a greater rise in systolic than in diastolic blood pressure. Prevalence in males and females under 40 years were equal. There was an association between hypertension and diabetes mellitus. More effective screening and therapeutic programmes should be initiated in the Indian population because of the high prevalence of hypertension which may lead to complications if untreated, and because 58% of the hypertensive subjects were untreated or had discontinued therapy.

Mineback Stimulation Research Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.R.

The Mineback Stimulation Research Program is a systematic study of hydraulic fracturing and the parameters which influence or control fracture geometry or behavior. Fractures are created near a tunnel complex at DOE's Nevada Test Site and are monitored, instrumented, and mined back to observe the effect of treatment, rock and reservoir properties on the fractures. An initial experiment to measure width and pressure in a hydraulic fracture was completed in FY 1983. The test showed that pressure drops along fractures are much larger than predicted, with the result that fractures are shorter, higher, and wider than present models estimate. Themore » cause of this is the complex morphology of hydraulic fractures, including a hierarchy of roughnesses, multiple stranding, and corners, such as the offsets which occur when natural fractures are intersected. A test to study flow behavior in hydraulic fractures with proppant is proposed for FY 1984. 7 figures.« less

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model.

PubMed

Park, Marcelo; Mendes, Pedro Vitale; Costa, Eduardo Leite Vieira; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Azevedo, Luciano Cesar Pontes

2016-01-01

The aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure. The factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested. Oxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL). In conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin.

"Deflategate": Time, Temperature, and Moisture Effects on Football Pressure

NASA Astrophysics Data System (ADS)

Blumenthal, Jack; Beljak, Lauren; Macatangay, Dahlia-Marie; Helmuth-Malone, Lilly; McWilliams, Catharina; Raptis, Sofia

2016-09-01

In a recent paper in TPT, DiLisi and Rarick used the National Football League "Deflategate" controversy to introduce to physics students the physics of a bouncing ball. In this paper, we measure and analyze the environmental effects of time, ambient temperature, and moisture on the internal pressure of an NFL football. We focus on the rate of pressure recovery that occurs when a cold football (either wet or dry) is returned to the warm locker room environment where the pressure was initially measured. Both studies stem from the so-called NFL "Deflategate" controversy in which footballs that initially met a minimum internal pressure requirement were rechecked at halftime of the AFC Championship game, and in some cases were reported to have fallen below the minimum pressure requirement. The question is whether the pressure changes were due to environmental exposure or rather to some air being released from the balls, or both.

Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization

NASA Technical Reports Server (NTRS)

Rinker, Martin; Krueger, Ronald; Ratcliffe, James

2013-01-01

The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed.

Parental body mass index and blood pressure are associated with higher body mass index and blood pressure in their adult offspring: a cross-sectional study in a resource-limited setting in northern Peru.

PubMed

Carrillo-Larco, Rodrigo M; Bernabé-Ortiz, Antonio; Sal Y Rosas, Víctor G; Sacksteder, Katherine A; Diez-Canseco, Francisco; Cárdenas, María K; Gilman, Robert H; Miranda, J Jaime

2018-05-01

High body mass index (BMI) and blood pressure (BP) are major contributors to the high burden of non-communicable diseases in adulthood. Individual high-risk and population approaches for prevention require newer strategies to target these risk factors and focusing on the family to introduce prevention initiatives appears as a promising scenario. Characterisation of the relationship between BMI and BP among the adult members of a given family merits evaluation. We conducted a secondary analysis of an implementation study in Tumbes, Peru, benefiting from data derived from families with at least one adult offspring. The exposures of interest were the BMI, systolic BP (SBP) and diastolic BP (DBP) of the mother and father. The outcomes were the BMI, SBP and DBP of the offspring. Mixed-effects linear regression models were conducted. The mean age of the offspring, mothers and fathers was 29 (SD: 9.5), 54 (SD: 11.8) and 59 (SD: 11.6) years, respectively. Father's BMI was associated with a quarter-point increase in offspring BMI, regardless of the sex of the offspring. Mother's BMI had a similar effect on the BMI of her sons, but had no significant effect on her daughters'. Mother's SBP was associated with almost one-tenth of mmHg increase in the SBP of the adult offspring. There was no evidence of an association for DBP. In families with adult members, the higher the parents' BMI and SBP, the higher their adult offspring's levels will be. © 2018 The Authors. Tropical Medicine & International Health Published by John Wiley & Sons Ltd.

A Free-flight Wind Tunnel for Aerodynamic Testing at Hypersonic Speeds

NASA Technical Reports Server (NTRS)

Seiff, Alvin

1954-01-01

The supersonic free-flight wind tunnel is a facility at the Ames Laboratory of the NACA in which aerodynamic test models are gun-launched at high speed and directed upstream through the test section of a supersonic wind tunnel. In this way, test Mach numbers up to 10 have been attained and indications are that still higher speeds will be realized. An advantage of this technique is that the air and model temperatures simulate those of flight through the atmosphere. Also the Reynolds numbers are high. Aerodynamic measurements are made from photographic observation of the model flight. Instruments and techniques have been developed for measuring the following aerodynamic properties: drag, initial lift-curve slope, initial pitching-moment-curve slope, center of pressure, skin friction, boundary-layer transition, damping in roll, and aileron effectiveness. (author)

Obstructive Sleep Apnoea and Atrial Fibrillation

PubMed Central

Zhang, Ling; Hou, Yuemei; Po, Sunny S

2015-01-01

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia and is associated with significant morbidity and mortality. Obstructive sleep apnoea (OSA) is common among patients with AF. Growing evidence suggests that OSA is associated with the initiation and maintenance of AF. This association is independent of obesity, body mass index and hypertension. OSA not only promotes initiation of AF but also has a significant negative impact on the treatment of AF. Patients with untreated OSA have a higher AF recurrence rate with drug therapy, electrical cardioversion and catheter ablation. Treatment with continuous positive airway pressure (CPAP) has been shown to improve AF control in patients with OSA. In this article, we will review and discuss the pathophysiological mechanisms of OSA that may predispose OSA patients to AF as well as the standard and emerging therapies for patients with both OSA and AF. PMID:26835094

Dental hard tissue modification and removal using sealed transverse excited atmospheric-pressure lasers operating at lambda=9.6 and 10.6 um

NASA Astrophysics Data System (ADS)

Fried, Daniel; Ragadio, Jerome N.; Akrivou, Maria; Featherstone, John D.; Murray, Michael W.; Dickenson, Kevin M.

2001-04-01

Pulsed CO2 lasers have been shown to be effective for both removal and modification of dental hard tissue for the treatment of dental caries. In this study, sealed transverse excited atmospheric pressure (TEA) laser systems optimally tuned to the highly absorbed 9.6 micrometers wavelength were investigated for application on dental hard tissue. Conventional TEA lasers produce an initial high energy spike at the beginning of the laser pulse of submicrosecond duration followed by a long tail of about 1 - 4 microsecond(s) . The pulse duration is well matched to the 1 - 2 microsecond(s) thermal relaxation time of the deposited laser energy at 9.6 micrometers and effectively heats the enamel to the temperatures required for surface modification at absorbed fluences of less than 0.5 J/cm2. Thus, the heat deposition in the tooth and the corresponding risk of pulpal necrosis from excessive heat accumulation is minimized. At higher fluences, the high peak power of the laser pulse rapidly initiates a plasma that markedly reduces the ablation rate and efficiency, severely limiting applicability for hard tissue ablation. By lengthening the laser pulse to reduce the energy distributed in the initial high energy spike, the plasma threshold can be raised sufficiently to increase the ablation rate by an order of magnitude. This results in a practical and efficient CO2 laser system for caries ablation and surface modification.

Experiments and modeling of variably permeable carbonate reservoir samples in contact with CO₂-acidified brines

DOE PAGES

Smith, Megan M.; Hao, Yue; Mason, Harris E.; ...

2014-12-31

Reactive experiments were performed to expose sample cores from the Arbuckle carbonate reservoir to CO₂-acidified brine under reservoir temperature and pressure conditions. The samples consisted of dolomite with varying quantities of calcite and silica/chert. The timescales of monitored pressure decline across each sample in response to CO₂ exposure, as well as the amount of and nature of dissolution features, varied widely among these three experiments. For all samples cores, the experimentally measured initial permeability was at least one order of magnitude or more lower than the values estimated from downhole methods. Nondestructive X-ray computed tomography (XRCT) imaging revealed dissolution featuresmore » including “wormholes,” removal of fracture-filling crystals, and widening of pre-existing pore spaces. In the injection zone sample, multiple fractures may have contributed to the high initial permeability of this core and restricted the distribution of CO₂-induced mineral dissolution. In contrast, the pre-existing porosity of the baffle zone sample was much lower and less connected, leading to a lower initial permeability and contributing to the development of a single dissolution channel. While calcite may make up only a small percentage of the overall sample composition, its location and the effects of its dissolution have an outsized effect on permeability responses to CO₂ exposure. The XRCT data presented here are informative for building the model domain for numerical simulations of these experiments but require calibration by higher resolution means to confidently evaluate different porosity-permeability relationships.« less

Short communication: Effects of high-pressure processing on the inactivity of Cronobacter sakazakii in whole milk and skim milk samples.

PubMed

Jiao, Rui; Gao, Jina; Li, Yinxiang; Zhang, Xiyan; Zhang, Maofeng; Ye, Yingwang; Wu, Qingping; Fan, Hongying

2016-10-01

Powdered infant formula is considered as the main transmission vehicle for Cronobacter sakazakii infections including meningitis, septicemia, and necrotizing enterocolitis. The effects of high-pressure processing treatment on inactivation of C. sakazakii ranging from 100 to 400 MPa for 3.0, 5.0, and 7.0 min in whole milk and skim milk were studied. Significant differences in inactivation of C. sakazakii were observed in milk samples under different pressures for 3 to 7 min compared with untreated samples, and C. sakazakii was not detected after 400 MPa for 3 min. The lethality rates of C. sakazakii cells in whole and skim milk with an initial level of 10(4) cfu/mL after 100 and 200 MPa treatments were not significantly different, but relatively higher lethality rates were found in whole milk after 300 MPa treatment than in skim milk. Finally, the scanning electron micrographs indicated that cellular envelope and intracellular damage of C. sakazakii cells were apparent after 300 and 400 MPa for 5.0 min compared with the untreated cells, and a progressive increase of injured cells with increased pressure treatment was found. It was concluded that C. sakazakii was sensitive to high-pressure processing treatment and that high-pressure processing treatment with 400 MPa for 3.0 min can be used to control C. sakazakii contamination in milk samples. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Relaxation limit of a compressible gas-liquid model with well-reservoir interaction

NASA Astrophysics Data System (ADS)

Solem, Susanne; Evje, Steinar

2017-02-01

This paper deals with the relaxation limit of a two-phase compressible gas-liquid model which contains a pressure-dependent well-reservoir interaction term of the form q (P_r - P) where q>0 is the rate of the pressure-dependent influx/efflux of gas, P is the (unknown) wellbore pressure, and P_r is the (known) surrounding reservoir pressure. The model can be used to study gas-kick flow scenarios relevant for various wellbore operations. One extreme case is when the wellbore pressure P is largely dictated by the surrounding reservoir pressure P_r. Formally, this model is obtained by deriving the limiting system as the relaxation parameter q in the full model tends to infinity. The main purpose of this work is to understand to what extent this case can be represented by a well-defined mathematical model for a fixed global time T>0. Well-posedness of the full model has been obtained in Evje (SIAM J Math Anal 45(2):518-546, 2013). However, as the estimates for the full model are dependent on the relaxation parameter q, new estimates must be obtained for the equilibrium model to ensure existence of solutions. By means of appropriate a priori assumptions and some restrictions on the model parameters, necessary estimates (low order and higher order) are obtained. These estimates that depend on the global time T together with smallness assumptions on the initial data are then used to obtain existence of solutions in suitable Sobolev spaces.

Initiation of Gaseous Detonation by Conical Projectiles

NASA Astrophysics Data System (ADS)

Verreault, Jimmy

Initiation and stabilization of detonation by hypersonic conical projectiles launched into combustible gas mixtures is investigated. This phenomenon must be understood for the design and optimization of specific hypersonic propulsion devices, such as the oblique detonation wave engine and the ram accelerator. The criteria for detonation initiation by a projectile is also related to fundamental aspects of detonation research, such as the requirement for direct initiation of a detonation by a blast wave. Experimental results of this problem also offer useful references for validation of numerical and theoretical modeling. Projectiles with cone half angles varying from 15° to 60° were launched into stoichiometric mixtures of hydrogen/oxygen with 70% argon dilution at initial pressures between 10 and 200 kPa. The projectiles were launched from a combustion-driven gas gun at velocities up to 2.2 km/s (corresponding to 133% of the Chapman Jouguet velocity). Pictures of the flowfields generated by the projectiles were taken via Schlieren photography. Five combustion regimes were observed about the projectile ranging from prompt and delayed oblique detonation wave formation, combustion instabilities, a wave splitting, and an inert shock wave. Two types of transition from the prompt oblique detonation wave regime to the inert shock regime were observed. The first (the delayed oblique detonation wave regime) showed an inert shock attached to the tip of the projectile followed by a sharp kink at the onset of an oblique detonation wave; this regime occurred by decreasing the cone angle at high mixture pressures. The second (the combustion instabilities regime) exhibited large density gradients due to combustion ignition and quenching phenomena; this regime occurred by decreasing the mixture pressure at large cone angles. A number of theoretical models were considered to predict critical conditions for the initiation of oblique detonations. The Lee-Vasiljev model agreed qualitatively well with the experimental results for relatively blunt projectiles (cone half-angle larger than 35°) and low mixture pressures (lower than 100 kPa). The trend of the critical Damköhler number calculated along the projectile cone surface was similar to that of the experimental results for slender cones (cone half-angles lower 35°) and high mixture pressures (higher than 100 kPa). Steady 2D simulations of reacting flows over finite wedges using the method of characteristics with a one-step Arrhenius chemical reaction model reproduced the three regimes observed for direct initiation of a detonation: the subcritical, critical and supercritical regimes. It is shown that in order for a 2D wedge to be equivalent to the problem of blast initiation of a detonation (which is the essence of the Lee-Vasiljev model), the Mach number normal to the oblique shock needs to be greater than 50 and the wedge angle has to be smaller than 30°. Simulations of reacting flows over semi-infinite wedges and cones were validated with CFD results. Excellent agreement was reached between the angle of overdriven oblique detonations obtained from the simulations and those from a polar analysis. For wedge or cone angles equal or lower than the minimum angle for which an oblique detonation is attached (according to the polar analysis), a Chapman-Jouguet oblique detonation was initiated. In the conical configuration, the curvature around the cone axis allowed an oblique detonation to be self-sustained at an angle less than without the curvature effect. At larger activation energies, the initiation process of an oblique detonation wave at the tip of a semi-infinite wedge or cone was identified. Unsteady 2D computational simulations were also conducted and showed the cellular structure of an oblique detonation wave. Instabilities in the form of transverse shock waves along the oblique detonation front arise for large activation energies.

Enhanced alveolar growth and remodeling in Guinea pigs raised at high altitude.

PubMed

Hsia, Connie C W; Carbayo, Juan J Polo; Yan, Xiao; Bellotto, Dennis J

2005-05-12

To examine the effects of chronic high altitude (HA) exposure on lung structure during somatic maturation, we raised male weanling guinea pigs at HA (3800m) for 1, 3, or 6 months, while their respective male littermates were simultaneously raised at low altitude (LA, 1200m). Under anaesthesia, airway pressure was measured at different lung volumes. The right lung was fixed at a constant airway pressure for morphometric analysis under light and electron microscopy. In animals raised at HA for 1 month, lung volume, alveolar surface area and alveolar-capillary blood volume (V(c)) were elevated above LA control values. Following 3-6 months of HA exposure, increases in lung volume and alveolar surface area persisted while the initial increase in V(c) normalized. Additional adaptation occurred, including a higher epithelial cell volume, septal tissue volume and capillary surface area, a lower alveolar duct volume and lower harmonic mean diffusion barrier resulting in higher membrane and lung diffusing capacities. These data demonstrate enhanced alveolar septal growth and progressive acinar remodeling during chronic HA exposure with long-term augmentation of alveolar dimensions as well as functional compensation in lung compliance and diffusive gas transport.

High pressure studies of A{sub 2}Mo{sub 3}O{sub 12} negative thermal expansion materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, AlGa)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong

2016-05-15

High pressure powder X-ray diffraction studies of several A{sub 2}Mo{sub 3}O{sub 12} materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, and AlGa) were conducted up to 6–7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversiblemore » on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga{sub 2}Mo{sub 3}O{sub 12} suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • The high pressure behavior of A{sub 2}Mo{sub 3}O{sub 12} (A=Al, Fe, (AlGa), (AlFe)) was studied. • All compounds undergo the same sequence of pressure-induced phase transitions. • The phase transition pressures correlate with the average size of the A-site cation. • All transitions were reversible with hysteresis. • Previously studied Ga{sub 2}Mo{sub 3}O{sub 12} undergoes the same sequence of transitions.« less

Biofilm-induced calcium carbonate precipitation: application in the subsurface

NASA Astrophysics Data System (ADS)

Phillips, A. J.; Eldring, J.; Lauchnor, E.; Hiebert, R.; Gerlach, R.; Mitchell, A. C.; Esposito, R.; Cunningham, A. B.; Spangler, L.

2012-12-01

We have investigated mitigation strategies for sealing high permeability regions, like fractures, in the subsurface. This technology has the potential to, for example, improve the long-term security of geologically-stored carbon dioxide (CO2) by sealing fractures in cap rocks or to mitigate leakage pathways to prevent contamination of overlying aquifers from hydraulic fracturing fluids. Sealing technologies using low-viscosity fluids are advantageous since they potentially reduce the necessary injection pressures and increase the radius of influence around injection wells. In this technology, aqueous solutions and suspensions are used to promote microbially-induced mineral precipitation which can be applied in subsurface environments. To this end, a strategy was developed to twice seal a hydraulically fractured, 74 cm (2.4') diameter Boyles Sandstone core, collected in North-Central Alabama, with biofilm-induced calcium carbonate (CaCO3) precipitates under ambient pressures. Sporosarcina pasteurii biofilms were established and calcium and urea containing reagents were injected to promote saturation conditions favorable for CaCO3 precipitation followed by growth reagents to resuscitate the biofilm's ureolytic activity. Then, in order to evaluate this process at relevant deep subsurface pressures, a novel high pressure test vessel was developed to house the 74 cm diameter core under pressures as high as 96 bar (1,400 psi). After determining that no impact to the fracture permeability occurred due to increasing overburden pressure, the fractured core was sealed under subsurface relevant pressures relating to 457 meters (1,500 feet) below ground surface (44 bar (650 psi) overburden pressure). After fracture sealing under both ambient and subsurface relevant pressure conditions, the sandstone core withstood three times higher well bore pressure than during the initial fracturing event, which occurred prior to biofilm-induced CaCO3 mineralization. These studies suggest biofilm-induced CaCO3 precipitation technologies may potentially seal and strengthen high permeability regions or fractures (either natural or induced) in the subsurface. Novel high pressure test vessel to investigate biogeochemical processes under relevant subsurface scales and pressures.

Towards band structure and band offset engineering of monolayer Mo(1-x)W(x)S2 via Strain

NASA Astrophysics Data System (ADS)

Kim, Joon-Seok; Ahmad, Rafia; Pandey, Tribhuwan; Rai, Amritesh; Feng, Simin; Yang, Jing; Lin, Zhong; Terrones, Mauricio; Banerjee, Sanjay K.; Singh, Abhishek K.; Akinwande, Deji; Lin, Jung-Fu

2018-01-01

Semiconducting transition metal dichalcogenides (TMDs) demonstrate a wide range of optoelectronic properties due to their diverse elemental compositions, and are promising candidates for next-generation optoelectronics and energy harvesting devices. However, effective band offset engineering is required to implement practical structures with desirable functionalities. Here, we explore the pressure-induced band structure evolution of monolayer WS2 and Mo0.5W0.5S2 using hydrostatic compressive strain applied in a diamond anvil cell (DAC) apparatus and theoretical calculations, in order to study the modulation of band structure and explore the possibility of band alignment engineering through different compositions. Higher W composition in Mo(1-x)W(x)S2 contributes to a greater pressure-sensitivity of direct band gap opening, with a maximum value of 54 meV GPa-1 in WS2. Interestingly, while the conduction band minima (CBMs) remains largely unchanged after the rapid gap increase, valence band maxima (VBMs) significantly rise above the initial values. It is suggested that the pressure- and composition-engineering could introduce a wide variety of band alignments including type I, type II, and type III heterojunctions, and allow to construct precise structures with desirable functionalities. No structural transition is observed during the pressure experiments, implying the pressure could provide selective modulation of band offset.

[Pressure control in medical gas distribution systems].

PubMed

Bourgain, J L; Benayoun, L; Baguenard, P; Haré, G; Puizillout, J M; Billard, V

1997-01-01

To assess whether the pressure gauges at the downstream part of pressure regulators are accurate enough to ensure that pressure in O2 pipeline is always higher than in Air pipeline and that pressure in the latter is higher than pressure in N2O pipeline. A pressure difference of at least 0.4 bar between two medical gas supply systems is recommended to avoid the reflow of either N2O or Air into the O2 pipeline, through a faulty mixer or proportioning device. Prospective technical comparative study. Readings of 32 Bourdon gauges were compared with data obtained with a calibrated reference transducer. Two sets of measurements were performed at a one month interval. Pressure differences between Bourdon gauges and reference transducer were 8% (0.28 bar) in average for a theoretical maximal error less than 2.5%. During the first set of measurements, Air pressure was higher than O2 pressure in one place and N2O pressure higher than Air pressure in another. After an increase in the O2 pipeline pressure and careful setting of pressure regulators, this problem was not observed at the second set of measurements. Actual accuracy of Bourdon gauges was not convenient enough to ensure that O2 pressure was always above Air pressure. Regular controls of these pressure gauges are therefore essential. Replacement of the faulty Bourdon gauges by more accurate transducers should be considered. As an alternative, the increase in pressure difference between O2 and Air pipelines to at least 0.6 bar is recommended.

Blood pressure associated with sleep-disordered breathing in a population sample of children.

PubMed

Bixler, Edward O; Vgontzas, Alexandros N; Lin, Hung-Mo; Liao, Duanping; Calhoun, Susan; Fedok, Fred; Vlasic, Vukmir; Graff, Gavin

2008-11-01

The current criteria for sleep-disordered breathing (SDB) in children are not based on a clinically relevant outcome. The purpose of this study was to assess the association of blood pressure with SDB in a random sample of the local elementary school children (kindergarten through grade 5) using a 2-phased strategy. During phase 1, a brief questionnaire was completed for all of the children (N=5740) with a response rate of 78.5%. During phase 2, 700 randomly selected children from phase 1 with a response rate of 70.0% were assessed with a full polysomnograph and a history/physical, including an ECG; ear, nose, and throat; and pulmonary evaluation. We observed a significantly elevated systolic blood pressure associated with the apnea hypopnea index (AHI): AHI >or=1 (2.9 mm Hg); AHI >or=3 (7.1 mm Hg); and AHI >or=5 (12.9 mm Hg). The SDB and blood pressure association remained significant after adjusting for age, sex, race, body mass index percentile or waist circumference, sleep efficiency, percentage of rapid eye movement sleep, and snoring. In addition, older age, body mass index percentile, waist circumference, and snoring were significantly associated with blood pressure, independent of SDB. Based on these findings, our study suggests that SDB is significantly associated with higher levels of systolic blood pressure in children aged 5 to 12 years even after adjusting for the various confounding factors. Clinically, the data support the threshold of AHI >or=5 for the initiation of treatment for SDB. Additional research is indicated to assess the efficacy of SDB treatment on reducing blood pressure.

The Systolic Blood Pressure Difference Between Arms and Cardiovascular Disease in the Framingham Heart Study

PubMed Central

Weinberg, Ido; Gona, Philimon; O’Donnell, Christopher J.; Jaff, Michael R.; Murabito, Joanne M.

2014-01-01

Background An increased inter-arm systolic blood pressure difference is an easily determined physical examination finding. The relationship between inter-arm systolic blood pressure difference and risk of future cardiovascular disease is uncertain. We described the prevalence and risk factor correlates of inter-arm systolic blood pressure difference in the Framingham Heart Study (FHS) original and offspring cohorts and examined the association between inter-arm systolic blood pressure difference and incident cardiovascular disease and all-cause mortality. Methods An increased inter-arm systolic blood pressure difference was defined as ≥10mmHg using the average of initial and repeat blood pressure measurements obtained in both arms. Participants were followed through 2010 for incident cardiovascular disease events. Multivariable Cox proportional hazards regression analyses were performed to investigate the effect of inter-arm systolic blood pressure difference on incident cardiovascular disease. Results We examined 3,390 (56.3% female) participants aged 40 years and older, free of cardiovascular disease at baseline, mean age of 61.1 years, who attended a FHS examination between 1991 and 1994 (original cohort) and from 1995 to 1998 (offspring cohort). The mean absolute inter-arm systolic blood pressure difference was 4.6 mmHg (range 0 to 78). Increased inter-arm systolic blood pressure difference was present in 317 (9.4%) participants. The median follow-up time was 13.3 years, during which time 598 participants (17.6%) experienced a first cardiovascular event including 83 (26.2%) participants with inter-arm systolic blood pressure difference ≥10 mmHg. Compared to those with normal inter-arm systolic blood pressure difference, participants with an elevated inter-arm systolic blood pressure difference were older (63.0 years vs. 60.9 years), had a greater prevalence of diabetes mellitus (13.3% vs. 7.5%,), higher systolic blood pressure (136.3 mmHg vs. 129.3 mmHg), and a higher total cholesterol level (212.1 mg/dL vs. 206.5 mg/dL). Inter-arm systolic blood pressure difference was associated with a significantly increased hazard of incident cardiovascular events in the multivariable adjusted model (hazard ratio 1.38, 95% CI, 1.09 to 1.75). For each 1-standard deviation unit increase in absolute interarm systolic blood pressure difference, the hazard ratio for incident cardiovascular events was 1.07 (CI, 1.00 to 1.14) in the fully-adjusted model. There was no such association with mortality (hazard ratio 1.02, 95% CI 0.76 to 1.38). Conclusions In this community-based cohort, an inter-arm systolic blood pressure difference is common and associated with a significant increased risk for future cardiovascular events, even when the absolute difference in arm systolic blood pressure is modest. These findings support research to expand clinical use of this simple measurement. PMID:24287007

A mesoscopic reaction rate model for shock initiation of multi-component PBX explosives.

PubMed

Liu, Y R; Duan, Z P; Zhang, Z Y; Ou, Z C; Huang, F L

2016-11-05

The primary goal of this research is to develop a three-term mesoscopic reaction rate model that consists of a hot-spot ignition, a low-pressure slow burning and a high-pressure fast reaction terms for shock initiation of multi-component Plastic Bonded Explosives (PBX). Thereinto, based on the DZK hot-spot model for a single-component PBX explosive, the hot-spot ignition term as well as its reaction rate is obtained through a "mixing rule" of the explosive components; new expressions for both the low-pressure slow burning term and the high-pressure fast reaction term are also obtained by establishing the relationships between the reaction rate of the multi-component PBX explosive and that of its explosive components, based on the low-pressure slow burning term and the high-pressure fast reaction term of a mesoscopic reaction rate model. Furthermore, for verification, the new reaction rate model is incorporated into the DYNA2D code to simulate numerically the shock initiation process of the PBXC03 and the PBXC10 multi-component PBX explosives, and the numerical results of the pressure histories at different Lagrange locations in explosive are found to be in good agreements with previous experimental data. Copyright © 2016 Elsevier B.V. All rights reserved.

Computational modeling of the pressurization process in a NASP vehicle propellant tank experimental simulation

NASA Technical Reports Server (NTRS)

Sasmal, G. P.; Hochstein, J. I.; Wendl, M. C.; Hardy, T. L.

1991-01-01

A multidimensional computational model of the pressurization process in a slush hydrogen propellant storage tank was developed and its accuracy evaluated by comparison to experimental data measured for a 5 ft diameter spherical tank. The fluid mechanic, thermodynamic, and heat transfer processes within the ullage are represented by a finite-volume model. The model was shown to be in reasonable agreement with the experiment data. A parameter study was undertaken to examine the dependence of the pressurization process on initial ullage temperature distribution and pressurant mass flow rate. It is shown that for a given heat flux rate at the ullage boundary, the pressurization process is nearly independent of initial temperature distribution. Significant differences were identified between the ullage temperature and velocity fields predicted for pressurization of slush and those predicted for pressurization of liquid hydrogen. A simplified model of the pressurization process was constructed in search of a dimensionless characterization of the pressurization process. It is shown that the relationship derived from this simplified model collapses all of the pressure history data generated during this study into a single curve.

Aortic Baroreceptors Display Higher Mechanosensitivity than Carotid Baroreceptors.

PubMed

Lau, Eva On-Chai; Lo, Chun-Yin; Yao, Yifei; Mak, Arthur Fuk-Tat; Jiang, Liwen; Huang, Yu; Yao, Xiaoqiang

2016-01-01

Arterial baroreceptors are mechanical sensors that detect blood pressure changes. It has long been suggested that the two arterial baroreceptors, aortic and carotid baroreceptors, have different pressure sensitivities. However, there is no consensus as to which of the arterial baroreceptors are more sensitive to changes in blood pressure. In the present study, we employed independent methods to compare the pressure sensitivity of the two arterial baroreceptors. Firstly, pressure-activated action potential firing was measured by whole-cell current clamp with a high-speed pressure clamp system in primary cultured baroreceptor neurons. The results show that aortic depressor neurons possessed a higher percentage of mechano-sensitive neurons. Furthermore, aortic baroreceptor neurons show a lower pressure threshold than that of carotid baroreceptor neurons. Secondly, uniaxial stretching of baroreceptor neurons, that mimics the forces exerted on blood vessels, elicited a larger increase in intracellular Ca(2+) rise in aortic baroreceptor neurons than in carotid baroreceptor neurons. Thirdly, the pressure-induced action potential firing in the aortic depressor nerve recorded in vivo was also higher. The present study therefore provides for a basic physiological understanding on the pressure sensitivity of the two baroreceptor neurons and suggests that aortic baroreceptors have a higher pressure sensitivity than carotid baroreceptors.

Enabling CoO improvement thru green initiatives

NASA Astrophysics Data System (ADS)

Gross, Eric; Padmabandu, G. G.; Ujazdowski, Richard; Haran, Don; Lake, Matt; Mason, Eric; Gillespie, Walter

2015-03-01

Chipmakers continued pressure to drive down costs while increasing utilization requires development in all areas. Cymer's commitment to meeting customer's needs includes developing solutions that enable higher productivity as well as lowering cost of lightsource operation. Improvements in system power efficiency and predictability were deployed to chipmakers' in 2014 with release of our latest Master Oscillating gas chamber. In addition, Cymer has committed to reduced gas usage, completing development in methods to reduce Helium gas usage while maintaining superior bandwidth and wavelength stability. The latest developments in lowering cost of operations are paired with our advanced ETC controller in Cymer's XLR 700ix product.

Selection of Compositions in Ti-Cr-C-Steel, Ti-B, Ti-B-Me Systems and Establishing Synthesis Parameters for Obtaining Product by “SHS-Electrical Rolling”

NASA Astrophysics Data System (ADS)

Aslamazashvili, Zurab; Tavadze, Giorgi; Chikhradze, Mikheil; Namicheishvili, Teimuraz; Melashvili, Zaqaria

2017-12-01

For the production materials by the proposed Self-propagating High-Temperature Synthesis (SHS) - Electric Rolling method, there are no limitations in the length of the material and the width only depends on the length of rolls. The innovation method enables to carry out the process in nonstop regime, which is possible by merging energy consuming SHS method and Electrical Rolling. For realizing the process it is mandatory and sufficient, that initial components, after initiation by thermal pulse, could interaction with the heat emission, which itself ensures the self-propagation of synthesis front in lieu of heat transfer in the whole sample. Just after that process, the rolls instantly start rotation with the set speed to ensure the motion of material. This speed should be equal to the speed of propagation of synthesis front. The synthesized product in hot plastic condition is delivered to the rolls in nonstop regime, simultaneously, providing the current in deformation zone in order to compensate the energy loses. As a result by using the innovation SHS -Electrical Rolling technology we obtain long dimensional metal-ceramic product. In the presented paper optimal compositions of SHS chasms were selected in Ti-Cr-C-Steel, Ti-B and Ti-B-Me systems. For the selection of the compounds the thermodynamic analysis has been carried out which enabled to determine adiabatic temperature of synthesis theoretically and to determine balanced concentrations of synthesized product at synthesis temperature. Thermodynamic analysis also gave possibility to determine optimal compositions of chasms and define the conditions, which are important for correct realization of synthesis process. For obtaining non porous materials and product by SHS-Electrical Rolling, it is necessary to select synthesis and compacting parameters correctly. These parameters are the pressure and the time. In Ti-Cr-C-Steel, Ti-B and Ti-B-Me systems the high quality (nonporous or low porosity <2%) of materials and product is directly depended on the liquid phase content just after the passing of synthesis front in the sample. The more content of liquid phase provides the higher quality of material. The content of liquid phase itself depends on synthesis parameters: speed and temperature of synthesis. The higher the speed and temperature of synthesis we have, higher the content of liquid phase is formed. The speed and the temperature of synthesis depend on the Δρ relative density of sample formed from initial chasm, this mean it depends on the pressure of formation of the sample. The paper describes the results of determination of optimal pressures in Ti-Cr-C-Steel, Ti-B and Ti-B-Me systems. Their values are defined as 50-70 MPa, 180-220 MPa and 45-70 MPa.

Bio-syngas production from agro-industrial biomass residues by steam gasification.

PubMed

Pacioni, Tatiana Ramos; Soares, Diniara; Domenico, Michele Di; Rosa, Maria Fernanda; Moreira, Regina de Fátima Peralta Muniz; José, Humberto Jorge

2016-12-01

This study evaluated the steam gasification potential of three residues from Brazilian agro-industry by assessing their reaction kinetics and syngas production at temperatures from 650 to 850°C and a steam partial pressure range of 0.05 to 0.3bar. The transition temperature between kinetic control and diffusion control regimes was identified. Prior to the gasification tests, the raw biomasses, namely apple pomace, spent coffee grounds and sawdust, were pyrolyzed in a fixed-bed quartz tubular reactor under controlled conditions. Gasification tests were performed isothermally in a magnetic suspension thermobalance and the reaction products were analyzed by a gas chromatograph with TCD/FID detectors. According to the characterization results, the samples presented higher carbon and lower volatile matter contents than the biomasses. Nevertheless, all of the materials had high calorific value. Syngas production was influenced by both temperature and steam partial pressure. Higher concentrations of H 2 and CO were found in the conversion range of 50-80% and higher concentrations of CO 2 in conversions around 10%, for all the gasified biochars. The H 2 /CO decreased with increasing temperature, mainly in kinetic control regime, in the lower temperature range. The results indicate the gasification potential of Brazilian biomass residues and are an initial and important step in the development of gasification processes in Brazil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Initial medical management in acute type A aortic dissection patients with a thrombosed false lumen in the ascending aorta combining intramural hematoma and retrograde dissection from the descending to the ascending aorta.

PubMed

Sadamatsu, Kenji; Takase, Susumu; Sagara, Shuichiro; Ohe, Kensuke; Nishi, Jun-Ichiro; Tashiro, Hideki; Kosuga, Tomokazu; Yasunaga, Hiroshi

2018-05-01

The feasibility of medical management for select patients with acute type A aortic dissection has been reported from a few institutions. In this study, we retrospectively investigated the safety and feasibility of our conservative approach for patients with type A aortic dissection in daily practice. From January 2013 to December 2017, 131 consecutive patients were admitted to our institution for acute aortic dissection, including 58 patients of type A. Initial medical management was attempted in select patients who were clinically stable and had a thrombosed false lumen of the ascending aorta without ulcer-like projections in the ascending aorta. Except for nine patients contraindicated for surgery, urgent surgery was performed in 26 patients (SRG group), while 23 patients (MED group) were treated with the initial medical management. The maximum diameter of the ascending aorta was significantly larger in the SRG group than in the MED group. In the MED group, the heart rate and blood pressures were well-controlled at admission to the intensive-care unit, and the systolic blood pressure was further reduced at 24 h after. The in-hospital mortality rates of the MED and SRG groups were 0% and 15%, respectively. During the follow-up period, the survival rate was significantly higher in the MED group than in the SRG group, and the aortic event-free survival at one year was 80%. The initial medical management for select patients with a thrombosed false lumen in the ascending aorta was a safe and feasible strategy in real-world practice.

Genetic variation in renin predicts the effects of thiazide diuretics.

PubMed

Huang, Chin-Chou; Chung, Chia-Min; Hung, Shuen-Iu; Leu, Hsin-Bang; Wu, Tao-Cheng; Huang, Po-Hsun; Lin, Shing-Jong; Pan, Wen-Harn; Chen, Jaw-Wen

2011-08-01

While genetic variants of renin-angiotensin-aldosterone system (RAAS) may modify the blood pressure (BP) response to thiazide diuretics, there was no evidence of genetic variations in renin (REN) playing a role. This study aimed to address the potential effects of genetic variations of RAAS on the response to initial treatment of hydrochlorothiazide (HCTZ). We enrolled nondiabetic hypertensive patients with a systolic blood pressure (SBP) ≥140 or a diastolic blood pressure (DBP) ≥90mmHg, who were either previously untreated or unsatisfactorily treated. After lifestyle modification and diet instruction for 2weeks, 90 patients with persistently elevated BP were given HCTZ 50 mg every morning for 2 weeks. Single nucleotide polymorphism markers were selected from genes involving in RAAS, including rs7079 and rs699 of angiotensinogen, rs4293 and rs4353 of angiotensin-converting enzyme and rs1464816 and rs11240688 of REN. The patients were divided into three groups according to the SBP response after HCTZ. The upper 1/3 responders had older age (P=0·035), higher SBP (P=0·039), higher pulse pressure (P=0·006) and lower plasma REN activity (PRA) (P=0·020) when compared with the lower 1/3 responders. Renin rs11240688 CC polymorphism (β=9·931, corrected P=0·012), Log PRA (β=7·451, P=0·004) and baseline SBP (β=0·299, P=0·006) were the independent predictors for the BP lowering response. In addition to PRA, renin rs11240688 CC polymorphism may also independently predict the effect of HCTZ. © 2011 The Authors. European Journal of Clinical Investigation © 2011 Stichting European Society for Clinical Investigation Journal Foundation.

[Nocturnal hypoxic episodes and structural changes in left ventricular myocardium in patients with mild-to-moderate arterial hypertension].

PubMed

Zelveian, P A; Buniatian, M S; Oshchenkova, E V; Rogoza, A N; Sergakova, L M

2002-01-01

To study correlations between structural changes of the left ventricle (LV) in patients with mild and moderate arterial hypertension (AH) and severity of hypoxic night episodes. The examination of 50 patients (mean age 52 +/- 1 year) with mild and moderate hypertension included echocardiographic measurement of LV myocardial mass, calculation of LV myocardial mass index. LV hypertrophy was stated in the index 125 g/m2 for men and 110 g/m2 for women. 24-h monitoring of arterial pressure (TM-2425) and night monitoring of hemoglobin saturation of arterial blood with oxygen (SaO2) using pulsoxymeter NONIN 8500M were made. The data processing was performed with the use of original program ARM-SaO2. Dissaturation was stated if SaO2 fell by 4% and more compared to the previous stable level at initial SaO2 level above 90%. The patients were divided into two groups according to the number of dissaturation episodes: group 1 (more than 20 dissaturation episodes) and group 2 (less than 20 episodes). The groups were comparable by gender, duration of hypertension, body mass index, systolic and diastolic arterial pressure, heart rate. In group I, pulse arterial pressure, systolic arterial pressure load for 14 hours, day and night were significantly higher. Patients with dissaturation had a significantly higher LV myocardial mass and more frequent LV hypertrophy (128 +/- 6 and 106 +/- 5 g/m2 and 56 and 20%, respectively). The correlation and multifactor regression analysis showed a predictive value not only of the pressor parameters but also of indices of night hypoxia in relation to structural changes of LV myocardium. The presence of significant hypoxic episodes in sleep in AH patients indicates risk to develop structural changes of LV myocardium.

Localized bulging in an inflated cylindrical tube of arbitrary thickness - the effect of bending stiffness

NASA Astrophysics Data System (ADS)

Fu, Y. B.; Liu, J. L.; Francisco, G. S.

2016-05-01

We study localized bulging of a cylindrical hyperelastic tube of arbitrary thickness when it is subjected to the combined action of inflation and axial extension. It is shown that with the internal pressure P and resultant axial force F viewed as functions of the azimuthal stretch on the inner surface and the axial stretch, the bifurcation condition for the initiation of a localized bulge is that the Jacobian of the vector function (P , F) should vanish. This is established using the dynamical systems theory by first computing the eigenvalues of a certain eigenvalue problem governing incremental deformations, and then deriving the bifurcation condition explicitly. The bifurcation condition is valid for all loading conditions, and in the special case of fixed resultant axial force it gives the expected result that the initiation pressure for localized bulging is precisely the maximum pressure in uniform inflation. It is shown that even if localized bulging cannot take place when the axial force is fixed, it is still possible if the axial stretch is fixed instead. The explicit bifurcation condition also provides a means to quantify precisely the effect of bending stiffness on the initiation pressure. It is shown that the (approximate) membrane theory gives good predictions for the initiation pressure, with a relative error less than 5%, for thickness/radius ratios up to 0.67. A two-term asymptotic bifurcation condition for localized bulging that incorporates the effect of bending stiffness is proposed, and is shown to be capable of giving extremely accurate predictions for the initiation pressure for thickness/radius ratios up to as large as 1.2.

Thermodynamic Behavior in Decaying Compressible Turbulence with Initially Dominant Temperature Fluctuations

NASA Astrophysics Data System (ADS)

Cai, X. D.; O'Brien, Edward E.; Ladeinde, Foluso

1996-11-01

Direct numerical simulation of decaying, isotropic, compressible turbulence in three dimensions is used to examine the behavior of fluctuations in density, temperature, and pressure when the initial conditions include temperature fluctuations larger than pressure fluctuations. The numerical procedure is described elsewhere (Ladeinde, F. et al.,) Phys. Fluids 7(11), pp. 2848 (1995), the initial turbulence Mach number range is subsonic, 0.3 to 0.7, and, following Ghosh and Matthaeus(Ghosh, S. and Matthaeus, W. H. Phys. Fluids A, pp. 148 (1991)), the initial compressible turbulence is characterized as a: mostly solenoidal, b: random, or c: longitudinal. These cases represent, respectively, ratios of initial kinetic energy in the compressible modes to total initial kinetic energy, say \\chi_0, which are either a: very small, b: about 0.6, or c: near unity. Thermodynamic scalings at the lowest values of initial Mach number and \\chi0 follow the predictions of Zank and Matthaeus (Zank, G. P. and Matthaeus, W. H. Phys. Fluids A(3), pp. 69 (1991)), but not otherwise. The relationship between \\chi, Mach number, and compressible pressure predicted by Sarkar et al.(Sarkar, S. et al.,) J. Fluid Mech. 227, pp. 473 (1991) applies, on average, to all cases computed.

Pressure gradient passivation of carbonaceous material normally susceptible to spontaneous combustion

DOEpatents

Ochs, Thomas L.; Sands, William D.; Schroeder, Karl; Summers, Cathy A.; Utz, Bruce R.

2002-01-29

This invention is a process for the passivation or deactivation with respect to oxygen of a carbonaceous material by the exposure of the carbonaceous material to an oxygenated gas in which the oxygenated gas pressure is increased from a first pressure to a second pressure and then the pressure is changed to a third pressure. Preferably a cyclic process which comprises exposing the carbonaceous material to the gas at low pressure and increasing the pressure to a second higher pressure and then returning the pressure to a lower pressure is used. The cycle is repeated at least twice wherein the higher pressure may be increased after a selected number of cycles.

Pressure gradient passivation of carbonaceous material normally susceptible to spontaneous combustion

DOEpatents

Ochs, Thomas L.; Sands, William D.; Schroeder, Karl; Summers, Cathy A.; Utz, Bruce R.

2000-11-14

This invention is a process for the passivation or deactivation with resp to oxygen of a carbonaceous material by the exposure of the carbonaceous material to an oxygenated gas in which the oxygenated gas pressure is increased from a first pressure to a second pressure and then the pressure is changed to a third pressure. Preferably a cyclic process which comprises exposing the carbonaceous material to the gas at low pressure and increasing the pressure to a second higher pressure and then returning the pressure to a lower pressure is used. The cycle is repeated at least twice wherein the higher pressure may be increased after a selected number of cycles.

Effect of age on kinetics of nitric oxide release in rat aorta and pulmonary artery.

PubMed Central

Tschudi, M R; Barton, M; Bersinger, N A; Moreau, P; Cosentino, F; Noll, G; Malinski, T; Lüscher, T F

1996-01-01

Aging is an important determinant of vascular disease. Endothelium-derived nitric oxide (NO) is protective as a vasodilator and inhibitor of platelet function. This study was designed to directly measure effects of prolonged aging on endotheliai NO release in isolated blood vessels and to delineate differences between the systemic and pulmonary circulation. Aortas and pulmonary arteries from 5-6-mo-old (young), 18-19-mo-old (middle-aged), and 32-33-mo-old (old) normotensive female rats were used. Blood pressure and plasma estradiol-17beta (E2) remained unchanged. In isolated blood vessels, NO release was induced by the receptor-independent agonist calcium ionophore A23187 (10 micromol/liter) and measured in situ on the endothelial surface of vessels using a porphyrinic microsensor. In vessels suspended in organ chambers isometric tension was recorded. In the aorta, the initial rate of NO release and peak NO concentration were reduced in middle-aged and old rats (P < 0.0006 vs. young rats, n = 6). Furthermore, endothelium-dependent relaxations to calcium ionophore and acetylcholine (both 10(-10) - 10(-5) mol/liter) were also reduced in aortas from old as compared with young rats (n = 6, P < 0.05). The initial rate of NO release and peak NO concentration significantly correlated with maximal relaxation to calcium ionophore A23187 (correlation coefficients r - 0.916, P < 0.0018 and r = 0.961, P < 0.0001, respectively, n = 7). In pulmonary arteries, however, the initial rate of NO release as well as peak NO concentration did not decrease with age (n = 6 for each age group, NS). In both blood vessels, the NO release was unaffected by superoxide dismutase in all age groups (n = 6, NS). Thus, aging specifically reduces initial rate and peak concentrations of endothelial NO release from aorta but not pulmonary artery indicating reduced NO production. As arterial pressure did not change with aging, the chronic exposure of the aorta to higher pressure and/or pulsatility than in the pulmonary artery may be the cause. This appears important as NO plays a protective role by preventing vasoconstriction, thrombosis and atherosclerosis. PMID:8770860

[Ophthalmodynamometry in the diagnostics of Grave's ophthalmopathy].

PubMed

Harder, B; Jonas, J B

2007-11-01

Since endocrine orbitopathy is characterised by exophthalmos and increased orbital tissue pressure which may lead to a compression of and damage to the optic nerve, it was the purpose of this study to evaluate whether the increased orbital tissue pressure in endocrine orbitopathy is associated with an elevated central retinal vein pressure as estimated by ophthalmodynamometry, and whether the central retinal vein pressure changes in the course of the disease. The prospective clinical study included 7 patients (13 eyes) with endocrine orbitopathy. They were screened for the prevalence of a spontaneous pulsation of the central retinal vein. In case of a missing spontaneous pulse, the collapse pressure of the central retinal vein was estimated by a modified ophthalmodynamometry using a corneal contact lens associated ophthalmodynamometric device. A group of 122 patients (156 eyes) without orbital or retinal diseases served as control group. The frequency of a spontaneous pulse of the central retinal vein was significantly lower in the study group (1/13 or 8%) than in the control group (121/156 or 78% p<0.001; odds ratio: 41.5). The central retinal vein collapse pressure as determined by ophthalmodynamometry was significantly higher in the study group (22.7+/-19.5 arbitrary units) than in the control group (4.7+/-12.8 arbitrary units) (p=0.002). For one patient with 7 examinations during a follow-up of 16 months, the central retinal vein pressure increased from 17 arbitrary units to 56 units, and decreased to 14 to 19 arbitrary units after initiation of a systemic therapy and regression of the exophthalmos. Three years later a spontaneous pulsation of the central retinal vein was detectable. Ophthalmodynamometry may be a useful examination for the indirect assessment of the orbital tissue pressure in patients with endocrine orbitopathy.

New evidence on the importance of the renin-angiotensin system in the treatment of higher-risk patients with hypertension.

PubMed

Sleight, Peter; Yusuf, Salim

2003-09-01

We reviewed the drug treatment of hypertension in the light of recent trials. beta-Blockers and diuretics clearly reduce mortality, strokes, and coronary heart disease (CHD) in hypertension. Recent trials assessed whether newer agents that block the renin-angiotensin-aldosterone system, or calcium blockers, offer any additional advantage, or have benefits in high-risk individuals with conventionally 'normal' blood pressure. The recent ALLHAT study claimed no differences in CHD or mortality when chlorthalidone, amlodipine, and lisinopril were compared. However, the decrease in blood pressure was not the same with the three agents, and a substantial proportion of patients enrolled did not have clinical disease. In contrast, the LIFE study (comparing losartan and a beta-blocker) and the ANBP-2 study [comparing angiotensin-converting enzyme (ACE) inhibition and a diuretic] reduced blood pressure similarly, yet demonstrated benefits in favour of angiotensin II type 1 receptor blockers (ARBs) and ACE inhibitors. Other trials indicated similar advantages of ACE inhibitors or ARBs in patients with diabetic nephropathy. Among high-risk patients with initial blood pressure in the 'normal' range, ACE inhibitors significantly reduce clinical events (mortality, strokes, and myocardial infarction), despite modest decreases in blood pressure, suggesting that additional mechanisms are responsible. Recent results of the Prospective Studies Collaboration show lower risk, even in the normal blood pressure range; high-risk patients will benefit further from ACE inhibitors and ARBs (and beta-blockers after myocardial infarction). Data for other blood pressure decreasing agents are unavailable in such populations. We conclude that blood pressure decreasing per se is of clinical benefit, but drugs that block the renin-angiotensin system offer additional advantages. Drug choice is best determined by the patient's clinical condition.

High pressure does not counterbalance the advantages of open techniques over closed techniques during heated intraperitoneal chemotherapy with oxaliplatin.

PubMed

Facy, Olivier; Combier, Christophe; Poussier, Matthieu; Magnin, Guy; Ladoire, Sylvain; Ghiringhelli, François; Chauffert, B; Rat, Patrick; Ortega-Deballon, Pablo

2015-01-01

Heated intraperitoneal chemotherapy (HIPEC) treats residual microscopic disease after cytoreductive surgery. In experimental models, the open HIPEC technique has shown a higher and more homogenous concentration of platinum in the peritoneum than achieved using the closed technique. A 25-cm H2O pressure enhances the penetration of oxaliplatin. Because pressure is easier to set up with the closed technique, high pressure may counterbalance the drawbacks of this technique versus open HIPEC, and a higher pressure may induce a higher penetration. Because higher concentration does not mean deeper penetration, a study of tissues beneath the peritoneum is required. Finally, achieving a deeper penetration (and a higher concentration) raises the question of the passage of drugs through the surgical glove and the surgeon's safety. Four groups of pigs underwent HIPEC with oxaliplatin (150 mg/L) for 30 minutes in open isobaric pressure and pressure at 25 cm H2O, and closed pressure at 25 and 40 cm H2O. Systemic absorption and peritoneal mapping of the concentration of platinum were analyzed, as well as in the retroperitoneal tissue and the surgical gloves. Blood concentrations were higher in open groups. In the parietal surfaces, the concentrations were not different between the isobaric and the closed groups (47.08, 56.39, and 48.57 mg/kg, respectively), but were higher in the open high-pressure group (85.93 mg/kg). In the visceral surfaces, they were lower in the closed groups (3.2 and 3.05 mg/kg) than in the open groups (7.03 and 9.56 mg/kg). Platinum concentrations were similar in the deep retroperitoneal tissue when compared between isobaric and high-pressure procedures. No platin was detected in the internal aspect of the gloves. The use of high pressure during HIPEC does not counterbalance the drawbacks of closed techniques. The tissue concentration of oxaliplatin achieved with the open techniques is higher, even if high pressure is applied during a closed technique. Open 25 cm H2O HIPEC achieved the highest tissue penetration of oxaliplatin, but did not enhance the depth of oxaliplatin penetration. High pressure did not enhance the risk of HIPEC. Copyright © 2015 Elsevier Inc. All rights reserved.

In situ XRD Study of Ca2+ Saturated Montmorillonite (STX-1) Exposed to Anhydrous and Wet Supercritical Carbon Dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaef, Herbert T.; Ilton, Eugene S.; Qafoku, Odeta

2012-01-09

Reactions involving scCO2 and a calcium saturated dioctahedral smectite (Ca-STX-1) were examined by in situ high-pressure x-ray diffraction over a range of temperatures (50° to 100°C) and pressures (90, 125, and 180 bar) relevant to long term geologic storage of CO2. Exposure of Ca-STX-1 containing one water of hydration (1W) to anhydrous scCO2 at 50°C and 90 bar produced an immediate increase of ~0.8 Å in the d001 basal reflection that was sustained for the length of the experiment (~44 hours). Higher ordered basal reflections displayed similar shifts. Following depressurization, positions of basal reflections and FWHM values (d001) returned tomore » initial values, with no measurable modification to the clay structure or water content. Similar results were obtained for tests conducted at 50°C and higher pressures (125 and 180 bar). Exposure of Ca-STX-1 containing two waters of hydration (2W) to scCO2 resulted in a decrease in the d001 reflection from 14.48 Å to 12.52 Å, after pressurization, indicating a partial loss of interlayer water. In addition, the hydration state of the clay became more homogeneous during contact with anhydrous scCO2 and after depressurization. In the presence of scCO2 and water, the clay achieved a 3W hydration state, based on a d001 spacing of 18.8 Å. In contrast to scCO2, comparable testing with N2 gas indicated trivial changes in the d001 series regardless of hydration state (1W or 2W). In the presence of free water and N2, the basal spacing for the Ca-STX-1 expanded slightly, but remained in the 2W hydration state. These experiments indicate that scCO2 can intercalate hydrated clays, where the 1W hydrate state is stable when exposed to anhydrous scCO2 under conditions proposed for geologic storage of CO2. Consequently, clays can act as secondary CO2 traps where potential collapse or expansion of the interlayer spacing depends on the initial hydration state of the clay and scCO2.« less

The effect of male teenage passengers on male teenage drivers: findings from a driving simulator study

PubMed Central

Ouimet, Marie Claude; Pradhan, Anuj K.; Simons-Morton, Bruce G.; Divekar, Gautam; Mehranian, Hasmik; Fisher, Donald L.

2014-01-01

Studies have shown that teenage drivers are less attentive, more frequently exhibit risky driving behavior, and have a higher fatal crash risk in the presence of peers. The effects of direct peer pressure and conversation on young drivers have been examined. Little is known about the impact on driving performance of the presence of a non-interacting passenger and subtle modes of peer influence, such as perceived social norms. The goal of this study was to examine if teenagers would engage in more risky driving practices and be less attentive in the presence of a passenger (vs. driving alone) as well as with a risk-accepting (vs. risk-averse) passenger. A confederate portrayed the passenger's characteristics mainly by his non-verbal attitude. The relationship between driver characteristics and driving behavior in the presence of a passenger was also examined. Thirty-six male participants aged 16-17 years old were randomly assigned to drive with a risk-accepting or risk-averse passenger. Main outcomes included speed, headway, gap acceptance, eye glances at hazards, and horizontal eye movement. Driver characteristics such as tolerance of deviance, susceptibility to peer pressure, and self-esteem were measured. Compared to solo driving, the presence of a passenger was associated with significantly fewer eye glances at hazards and a trend for fewer horizontal eye movements. Contrary to the hypothesis, however, passenger presence was associated with a greater number of vehicles before initiating a left turn. Results also showed, contrary to the hypothesis, that participants with the risk-accepting passenger maintained significantly longer headway with the lead vehicle and engaged in more eye glances at hazards than participants with the risk-averse passenger. Finally, when driving with the passenger, earlier initiation of a left turn in a steady stream of oncoming vehicles was significantly associated with higher tolerance of deviance and susceptibility to peer pressure, while fewer eye glances at hazards was linked to lower self-esteem. While the results of this study were mixed, they suggest that the presence of a teenage passenger can affect some aspects of teenage driver behavior even in the absence of overt pressure and distraction. Results are discussed in relation to theoretical concepts of social influence and social facilitation models. PMID:23727554

Blast from pressurized carbon dioxide released into a vented atmospheric chamber

NASA Astrophysics Data System (ADS)

Hansen, P. M.; Gaathaug, A. V.; Bjerketvedt, D.; Vaagsaether, K.

2018-03-01

This study describes the blast from pressurized carbon dioxide (CO2) released from a high-pressure reservoir into an openly vented atmospheric chamber. Small-scale experiments with pure vapor and liquid/vapor mixtures were conducted and compared with simulations. A motivation was to investigate the effects of vent size and liquid content on the peak overpressure and impulse response in the atmospheric chamber. The comparison of vapor-phase CO2 test results with simulations showed good agreement. This numerical code described single-phase gas dynamics inside a closed chamber, but did not model any phase transitions. Hence, the simulations described a vapor-only test into an unvented chamber. Nevertheless, the simulations reproduced the incident shock wave, the shock reflections, and the jet release inside the atmospheric chamber. The rapid phase transition did not contribute to the initial shock strength in the current test geometry. The evaporation rate was too low to contribute to the measured peak overpressure that was in the range of 15-20 kPa. The simulation results produced a calculated peak overpressure of 12 kPa. The liquid tests showed a significantly higher impulse compared to tests with pure vapor. Reducing the vent opening from 0.1 to 0.01 m2 resulted in a slightly higher impulse calculated at 100 ms. The influence of the vent area on the calculated impulse was significant in the vapor-phase tests, but not so clear in the liquid/vapor mixture tests.

Participation and cardiovascular risk reduction in a voluntary worksite nutrition and physical activity program.

PubMed

Thorndike, Anne N; Healey, Erica; Sonnenberg, Lillian; Regan, Susan

2011-02-01

In a cohort of employees participating in a worksite nutrition and physical activity program, we compared program completion and changes in cardiovascular risk factors by baseline body mass index. In 2007, 774 employees enrolled in a 10 week program at a hospital in Boston, Massachusetts. Program completion and change in weight, cholesterol, and blood pressure were compared between obese (body mass index≥30), overweight (body mass index=25-29.9), and normal weight (body mass index<25) participants. At baseline, 63% were obese or overweight and had higher blood pressure and cholesterol compared to normal weight participants. Program completion was 82% and did not differ by body mass index. Mean weight loss was 1.9 kg at end of program (p<0.001) and 0.4 kg at 1 year (p=0.002). At end of program, participants with body mass index≥30 lost 3.0% body weight vs. 2.7% for body mass index=25-29.9 and 1.7% for body mass index<25 (p<0.001), but weight loss at 1 year did not differ by body mass index. Mean cholesterol and blood pressure were lower at end of program and 1 year (all, p<0.005) but did not differ by body mass index. Worksite programs can successfully initiate cardiovascular risk reduction among employees, but more intensive interventions are needed to make significant improvements in the health of higher risk obese employees. Copyright © 2010 Elsevier Inc. All rights reserved.

Automated Office Blood Pressure Measurement.

PubMed

Myers, Martin G

2018-04-01

Manual blood pressure (BP) recorded in routine clinical practice is relatively inaccurate and associated with higher readings compared to BP measured in research studies in accordance with standardized measurement guidelines. The increase in routine office BP is the result of several factors, especially the presence of office staff, which tends to make patients nervous and also allows for conversation to occur. With the disappearance of the mercury sphygmomanometer because of environmental concerns, there is greater use of oscillometric BP recorders, both in the office setting and elsewhere. Although oscillometric devices may reduce some aspects of observer BP measurement error in the clinical setting, they are still associated with higher BP readings, known as white coat hypertension (for diagnosis) or white coat effect (with treated hypertension). Now that fully automated sphygmomanometers are available which are capable of recording several readings with the patient resting quietly, there is no longer any need to have office staff present when BP is being recorded. Such readings are called automated office blood pressure (AOBP) and they are both more accurate than conventional manual office BP and not associated with the white coat phenomena. AOBP readings are also similar to the awake ambulatory BP and home BP, both of which are relatively good predictors of cardiovascular risk. The available evidence suggests that AOBP should now replace manual or electronic office BP readings when screening patients for hypertension and also after antihypertensive drug therapy is initiated. Copyright © 2018. The Korean Society of Cardiology.

Impact of High-Temperature, High-Pressure Synthesis Conditions on the Formation of the Grain Structure and Strength Properties of Intermetallic Ni3Al

NASA Astrophysics Data System (ADS)

Ovcharenko, V. E.; Ivanov, K. V.; Boyangin, E. N.; Krylova, T. A.; Pshenichnikov, A. P.

2018-01-01

The impact of the preliminary load on 3Ni+Al powder mixture and the impact of the duration of the delay in application of compacting pressure to synthesis product under the conditions of continuous heating of the mixture up to its self-ignition on the grain size and strength properties of the synthesized Ni3Al intermetallide material have been studied. The grain structure of the intermetallide synthesized under pressure was studied by means of metallography, transmission electron microscopy and EBSD analysis, with the dependence of ultimate tensile strength on the grain size in the synthesized intermetallide having been investigated at room temperature and at temperatures up to 1000°C. It is shown that an increase in the pressure preliminarily applied to the initial mixture compact results in reduced grain size of the final intermetallide, whereas an increase in pre-compaction time makes the grain size increased. A decrease in the grain size increases the ultimate tensile strength of the intermetallide. The maximum value of the ultimate tensile strength in the observed anomalous temperature dependence of this strength exhibits a shift by 200°C toward higher temperatures, and the ultimate strength of the synthesized intermetallide at 1000°C increases roughly two-fold.

The smooth transition from field emission to a self-sustained plasma in microscale electrode gaps at atmospheric pressure

NASA Astrophysics Data System (ADS)

Bilici, Mihai A.; Haase, John R.; Boyle, Calvin R.; Go, David B.; Sankaran, R. Mohan

2016-06-01

We report on the existence of a smooth transition from field emission to a self-sustained plasma in microscale electrode geometries at atmospheric pressure. This behavior, which is not found at macroscopic scales or low pressures, arises from the unique combination of large electric fields that are created in microscale dimensions to produce field-emitted electrons and the high pressures that lead to collisional ionization of the gas. Using a tip-to-plane electrode geometry, currents less than 10 μA are measured at onset voltages of ˜200 V for gaps less than 5 μm, and analysis of the current-voltage (I-V) relationship is found to follow Fowler-Nordheim behavior, confirming field emission. As the applied voltage is increased, gas breakdown occurs smoothly, initially resulting in the formation of a weak, partial-like glow and then a self-sustained glow discharge. Remarkably, this transition is essentially reversible, as no significant hysteresis is observed during forward and reverse voltage sweeps. In contrast, at larger electrode gaps, no field emission current is measured and gas breakdown occurs abruptly at higher voltages of ˜400 V, absent of any smooth transition from the pre-breakdown condition and is characterized only by glow discharge formation.

Change in singing voice production, objectively measured.

PubMed

Schutte, Harm K; Stark, James A; Miller, Donald G

2003-12-01

Although subglottal pressures in conversational speech are relatively easily measured and thus known, the higher values that sometimes occur in singing (especially in tenors) have received little attention in the literature. Still more unusual is the opportunity to measure a large-scale change over decades in the application of pressure in singing production. This study compares measurements of subglottal pressure in a tenor/singing teacher (JS) at two points in his career: in his early thirties, when he was a subject in HS's dissertation study on the efficiency of voice production; and recently, in his fifties, in connection with JS's forthcoming book on the history of the pedagogy of Bel Canto. Although a single case study, its points of special interest include the high values initially measured (up to 100 cm H2O) and the reduction of this figure by more than 50% in the maximal values of the recent measurements. The study compares these values with those of other singers in the same laboratory (both with esophageal balloon and directly, with a catheter passed through the glottis) and in the literature, as well as discusses in detail the problems pertaining to the measurement (repeatability, correcting for lung volume, etc.). As a sophisticated subject, JS makes some pertinent observations about the changes in his use of subglottal pressure.

Preliminary evidence of attenuated blood pressure reactivity to acute stress in adults following a recent marital separation.

PubMed

Grinberg, Austin M; O'Hara, Karey L; Sbarra, David A

2018-03-01

This study explores cardiovascular reactivity during an acute-stress task in a sample of recently separated adults. In a cross-sectional design, we examined the association between adults' subjective separation-related distress and changes in heart rate and blood pressure across the acute-stress laboratory paradigm in a sample of 133 (n = 49 men) recently separated adults. Heart rate (HR) and Blood pressure (BP) were recorded across a resting baseline period, a math stressor task, and a recovery period. Multilevel analyses revealed that adults who reported greater separation-related distress exhibited higher initial BP and a slower linear increase in BP across the study period. In addition, adults reporting greater separation-related distress evidenced significantly slower declines in diastolic blood pressure (DBP) following the acute-stress task. HR reactivity was not moderated by separation-related distress. In recently separated adults, preliminary evidence suggests that the context of the stressors may reveal differential patterns of problematic reactivity (exaggerated or blunted responding). Greater emotional intrusion and hyperactivity symptoms may index increased risk for blunted cardiovascular reactivity to general stressors. This pattern of reactivity is consistent with models of allostatic load that emphasise the deleterious effect of hyporesponsivity to environmental demands.

Simulations of supersonic highly under-expanded hydrogen jets

NASA Astrophysics Data System (ADS)

Miarnau Marin, Ana; Xiao, Cheng-Nian; Denner, Fabian; van Wachem, Berend

2017-11-01

The pressure drop across choke valves required to transport natural gas can be in the order of several hundred bars, leading to the development of supersonic under-expanded jets. When considering a real gas, the gas can cool upon expansion, a phenomenon which can be explained by the Joule-Thomson effect. This study compares the effects of using ideal and real gas equations of state, using a computational model in which hydrogen is released from a high-pressure tank, through a converging nozzle, into a chamber containing hydrogen at near-atmospheric conditions. The initial studies were carried out using an ideal gas assumption and nozzle pressure ratios of 10, 30 and 70 and the results were validated against existing literature. To account for the Joule-Thomson effect, ideal and real gas simulations were then carried out with a pressure ratio of 70. For the real gas model, the Peng-Robinson equation of state was chosen. At the nozzle exit, the ideal gas model underestimates the velocity and overestimates the temperature and density; as the flow expands, the flow properties are the same up to the Mach disk, at which point the ideal gas underestimates the Mach number and predicts a higher temperature and density than the Peng-Robinson model due to the absence of cooling.

Quantitative analysis of a frequency-domain nonlinearity indicator.

PubMed

Reichman, Brent O; Gee, Kent L; Neilsen, Tracianne B; Miller, Kyle G

2016-05-01

In this paper, quantitative understanding of a frequency-domain nonlinearity indicator is developed. The indicator is derived from an ensemble-averaged, frequency-domain version of the generalized Burgers equation, which can be rearranged in order to directly compare the effects of nonlinearity, absorption, and geometric spreading on the pressure spectrum level with frequency and distance. The nonlinear effect is calculated using pressure-squared-pressure quadspectrum. Further theoretical development has given an expression for the role of the normalized quadspectrum, referred to as Q/S by Morfey and Howell [AIAA J. 19, 986-992 (1981)], in the spatial rate of change of the pressure spectrum level. To explore this finding, an investigation of the change in level for initial sinusoids propagating as plane waves through inviscid and thermoviscous media has been conducted. The decibel change with distance, calculated through Q/S, captures the growth and decay of the harmonics and indicates that the most significant changes in level occur prior to sawtooth formation. At large distances, the inviscid case results in a spatial rate of change that is uniform across all harmonics. For thermoviscous media, large positive nonlinear gains are observed but offset by absorption, which leads to a greater overall negative spatial rate of change for higher harmonics.

Slugging Flow of Water Draining from the Bottom of a Non-Vented Container

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charles W. Solbrig

2010-06-01

Experiments were run to observe the behavior of water exiting through an orifice at the bottom of an non-vented container. Initially, the container is nearly full of water with a small air space on top. Once the orifice was uncovered, the slugging rate and the drain rate of the water leaving the container were measured. Upon initially opening the orifice, water drains out until the air pressure above the water reduces enough that the air pressure drop from inside to outside of the container supports the water column and the water stops flowing. Air then enters the container through themore » orifice forming a bubble, which grows until it detaches and bubbles through the water to reach the air space. Once the bubble enters, this added air increases the pressure in the air space enough to allow the water to start flowing out again. This cycle of flow out, flow stoppage, air inflow, and bubble breakoff continues over and over until the hole is closed or the container empties. This is referred to as the “slugging cycle.” A mechanism is proposed to describe the slugging cycle which is modeled analytically. This paper presents the description of the experiments, data obtained, the mechanistic model, and comparison of the model to the experimental data. The model predicts outflow rates close to experimental values. Flow rates from non-vented containers are more than 10 to 20 less than vented containers. The bubbles which must enter the container periodically to increase the internal air pressure stop the water flow momentarily so are responsible for this large decrease in flow rate. Swirl induced in the non-vented container causes the flow rates to increase by a factor of two. The flow rate out of a non-vented container is independent of water height which is in direct contrast to a vented container where the flow rate is proportional to the square root of the water height. The constant rate is due to the container pressure. The higher the water level, the lower the air pressure is in the container. This analytical model requires input of the bubble size. The volume recommended is the volume of a cylinder with the base of the orifice area and length of 3.3 cm. Slugging rate varies only a small amount falling in the range to 2 to 4 cycles/sec. Preliminary work with other containers indicates larger containers, larger orifices and nozzle exit shapes produce higher specific flow rates. The standard multiphase flow equations could not be used to analyze this situation because the two phases are not interpenetrating. Instead one phase must fully stop before the other can flow. Interpenetrating phases allow can pass one another each affecting the other with friction and virtual mass. An interesting observation: The negative air pressure in the container is observable. It equals the water height.« less

What Can We Learn from Hugoniot Temperature as a Function of Shock Velocity?

NASA Astrophysics Data System (ADS)

LI, M.; Jeanloz, R.

2015-12-01

Shock-wave experiments traditionally rely on impact techniques, whereby measured shock velocity (US) can be related to material velocity (up), determined from the impact velocity (= 2up for a symmetric impact), and resulting in the empirically observed linear US-up equation of state: US = c0 + s up. Modern experiments relying on laser-driven compression have the advantage of reaching higher pressures than laboratory impact experiments, but up is typically not determined; instead, Hugoniot temperature (TH) and shock velocity are more readily measured. Assuming a linear US-up equation of state and that the Grüneisen parameter has the volume dependence g(V) = g0 (V/V0), measurements of the Hugoniot temperature as a function of shock velocity provide constraints on the specific heat along the Hugoniot CVH(US) = V0 f(US)[c0 g0 TH - s US dTH/dUS]-1 where the Walsh-Christian (1955) function f(US) = - (US - c0)2 US/(V0 s c0) = TH dSH/dVH gives the entropy change along the Hugoniot (subscripts 0 and H indicate zero-pressure and Hugoniot states, respectively). In this sense, TH(US) measurements are similar to calorimetry experiments. If specific heat and Grüneisen parameter are determined independently (e.g., from wave-velocity measurements and experiments on porous samples), the TH(US) analog to the linear US-up equation of state is TH(US) = {T0 exp(g0 /s) - ò[V0 c0 f(x)/(s x CV)] exp[c0 g0 /(s x)] dx} exp[- c0 g0 /(s US)] where the integration is from x = c0 to x = US. In addition, experiments can be considered with: 1) different initial volume, as in a porous sample; 2) different initial internal energy, as in a sample heated at constant volume; and 3) different initial volume and internal energy, as in a sample initially heated at ambient pressure. From these four initial states, we get four different Hugoniot curves, and can also consider the effect of phase transition latent heat. Temperature as a function of shock velocity may thus be benefit the analysis of melting and other phase transitions with small volume change and finite latent heat.

Equation of state of fluid helium at high temperatures and densities

NASA Astrophysics Data System (ADS)

Cai, Lingcang; Chen, Qifeng; Gu, Yunjun; Zhang, Ying; Zhou, Xianming; Jing, Fuqian

2005-03-01

Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6, 1.2, and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer. It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data. The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K, i.e., the D ≈ u relation, D= C 0+λ u ( u<10 km/s, λ=1.32) in a low pressure region, is approximately parallel with the fitted D ≈ u (λ=1.36) of liquid helium from the experimental data of Nellis et al. Our calculations show that the Hugoniot parameter λ is independent of the initial density p{in0}. The D≈ u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates to about 18000 K and the ionization degree of the shocked gas helium reaches 10-3.

Effect of Loading Efficiency on the Process of Consolidation in Unsaturated Soils

NASA Astrophysics Data System (ADS)

Lo, W. C.; Lee, J. W.; Deng, J. H.; Liu, J. H.

2016-12-01

Loading efficiency is an undrained poroelastic coefficient that causes an increase in the pore pressure due to an increase in the compressive axial stress. In order to illustrate the importance of loading efficiency on the process of consolidation in unsaturated soils, we utilize two assumptions proposed by Biot (1941) and Terzaghi (1943) to formulate the initial conditions taking account of loading efficiency and without consideration of loading efficiency, respectively. In Biot's theory (1941), he suggested that water is not allowed to escape when the external loading is instantly applied on a porous medium. Accordingly, the soil texture sample is considered to be undrained, and the linearized increment of the fluid content is equal to zero. For this reason, water and air can sustain an external loading only partially at the moment it is imposed, leading to an immediate one-dimensional consolidation. On the contrary, Terzaghi (1943) posited that as the external loading is initially applied, it is entirely sustained by the pore fluid. Thus, the initial water and air pressures are equal to the stress of external loading. Numerical calculations of excess pore water pressure and total settlement were made for a soil with clay texture as an illustrative example. A comparative study shows that in the early stage of consolidation, the model of considering loading efficiency generates larger time-dependent total settlement and also has the highest value of excess pore water pressure initially. The physical cause behind this difference is that the initial conditions established from Biot's theory is much smaller, reflecting the soil skeleton to carry most of external load at the moment it is imposed. Our results indicate that, in terms of the initial conditions for water and air pressures, the loading efficiency must be taken into account in the early stage of consolidation.

Vapor pressure measured with inflatable plastic bag

NASA Technical Reports Server (NTRS)

1965-01-01

Deflated plastic bag in a vacuum chamber measures initial low vapor pressures of materials. The bag captures the test sample vapors and visual observation of the vapor-inflated bag under increasing external pressures yields pertinent data.

40 CFR 147.3107 - Mechanical integrity.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Oklahoma Indian Tribes § 147.3107 Mechanical integrity. (a) Monitoring of annulus pressure conducted pursuant to § 146.8(b)(1) shall be preceded by an initial pressure test. A positive gauge pressure on the casing/tubing annulus (filled with liquid) shall be maintained continuously. The pressure shall be...

40 CFR 147.3107 - Mechanical integrity.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Oklahoma Indian Tribes § 147.3107 Mechanical integrity. (a) Monitoring of annulus pressure conducted pursuant to § 146.8(b)(1) shall be preceded by an initial pressure test. A positive gauge pressure on the casing/tubing annulus (filled with liquid) shall be maintained continuously. The pressure shall be...

40 CFR 147.3107 - Mechanical integrity.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Oklahoma Indian Tribes § 147.3107 Mechanical integrity. (a) Monitoring of annulus pressure conducted pursuant to § 146.8(b)(1) shall be preceded by an initial pressure test. A positive gauge pressure on the casing/tubing annulus (filled with liquid) shall be maintained continuously. The pressure shall be...

40 CFR 147.3107 - Mechanical integrity.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Oklahoma Indian Tribes § 147.3107 Mechanical integrity. (a) Monitoring of annulus pressure conducted pursuant to § 146.8(b)(1) shall be preceded by an initial pressure test. A positive gauge pressure on the casing/tubing annulus (filled with liquid) shall be maintained continuously. The pressure shall be...

76 FR 33239 - High Pressure Steel Cylinders From the People's Republic of China; Initiation of Countervailing...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-08

... DEPARTMENT OF COMMERCE International Trade Administration [C-570-978] High Pressure Steel... countervailing duty (``CVD'') petition concerning imports of high pressure steel cylinders (``steel cylinders... of Antidumping Duties and Countervailing Duties on High Pressure Steel Cylinders from the People's...

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model

PubMed Central

Park, Marcelo; Mendes, Pedro Vitale; Costa, Eduardo Leite Vieira; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Azevedo, Luciano Cesar Pontes

2016-01-01

Objective The aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure. Methods The factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested. Results Oxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL). Conclusion In conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin. PMID:27096671

Systematic review: antihypertensive drug therapy in patients of African and South Asian ethnicity.

PubMed

Brewster, Lizzy M; van Montfrans, Gert A; Oehlers, Glenn P; Seedat, Yackoob K

2016-04-01

Despite the large differences in the epidemiology of hypertension across Europe, treatment strategies are similar for national populations of white European descent. However, hypertensive patients of African or South Asian ethnicity may require ethnic-specific approaches, as these population subgroups tend to have higher blood pressure at an earlier age that is more difficult to control, a higher occurrence of diabetes, and more target organ damage with earlier cardiovascular mortality. Therefore, we systematically reviewed the evidence on antihypertensive drug treatment in South Asian and African ethnicity patients. We used the Cochrane systematic review methodology to retrieve trials in electronic databases including CENTRAL, PubMed, and Embase from their inception through November 2015; and with handsearch. We retrieved 4596 reports that yielded 35 trials with 7 classes of antihypertensive drugs in 25,540 African ethnicity patients. Aside from the well-known blood pressure efficacy of calcium channel blockers and diuretics, with lesser effect of ACE inhibitors and beta-blockers, nebivolol was not more effective than placebo in reducing systolic blood pressure levels. Trials with morbidity and mortality outcomes indicated that lisinopril and losartan-based therapy were associated with a greater incidence of stroke and sudden death. Furthermore, 1581 reports yielded 16 randomized controlled trials with blood pressure outcomes in 1719 South Asian hypertensive patients. In contrast with the studies in African ethnicity patients, there were no significant differences in blood pressure lowering efficacy between drugs, and no trials available with mortality outcomes. In conclusion, in patients of African ethnicity, treatment initiated with ACE inhibitor or angiotensin II receptor blocker monotherapy was associated with adverse cardiovascular outcomes. We found no evidence of different efficacy of antihypertensive drugs in South Asians, but there is a need for trials with morbidity and mortality outcomes. Screening for cardiovascular risk at a younger age, treating hypertension at lower thresholds, and new delivery models to find, treat and follow hypertensives in the community may help reduce the excess cardiovascular mortality in these high-risk groups.

Irradiated ignition of solid materials in reduced pressure atmosphere with various oxygen concentrations for fire safety in space habitats

NASA Astrophysics Data System (ADS)

Nakamura, Y.; Aoki, A.

Effects of sub-atmospheric ambient pressure and oxygen content on irradiated ignition characteristics of solid combustibles were examined experimentally in order to elucidate the flammability and chance of fire in depressurized systems and give ideas for the fire safety and fire fighting strategies for such environments. Thin cellulosic paper was used as the solid combustible since cellulose is one of major organic compounds and flammables in the nature. Applied atmospheres consisted of inert gases (either CO 2 or N 2) and oxygen at various mixture ratios. Total ambient pressure ( P) was varied from 101 kPa (standard atmospheric pressure, P0) to 20 kPa. Ignition was initiated by external thermal radiation with CO 2 laser (10 W total; 21.3 W/cm 2 of the corresponding peak flux) onto the solid surface. Thermal degradation of the solid produced combustible gaseous products (e.g. CO, H 2, or other low weight of HCs) and these products mixed with ambient oxygen to form the combustible mixture over the solid. Heat transfer from the irradiated surface into the mixture accelerated the exothermic reaction in the gas phase and finally thermal runaway (ignition) was achieved. A digital video camera was used to analyze the ignition characteristics. Flammability maps in partial pressure of oxygen (ppO 2) and normalized ambient pressure ( P/ P0) plane were made to reveal the fire hazard in depressurized environments. Results showed that a wider flammable range was obtained in sub-atmospherics conditions. In middle pressure range (101-40 kPa), the required ppO 2 for ignition decreased almost linearly as the total pressure decreased, indicating that higher fire risk is expected. In lower pressure range (<40 kPa), the required partial pressure of oxygen increased dramatically, then ignition was eventually not achieved at pressures less than 20 kPa under the conditions studied here. The findings suggest that it might be difficult to satisfy safety in space agriculture since it has been reported that higher oxygen concentrations are preferable for plant growth in depressurized environments. Our results imply that there is an optimum pressure level to achieve less fire chance with acceptable plant growth. An increase of the flammable range in middle pressure level might be explained by following two effects: one is a physical effect, such as a weak convective thermal removal from ignitable domain (near the hot surface) to the ambient of atmosphere, and the other is chemical effect which causes so-called "explosion peninsula" as a result of depleting radical consumption due to third-body recombination reaction. Further studies are necessary to determine the controlling factor on the observed flammable trend in depressurized conditions.

Intramuscular pressure and torque during isometric, concentric and eccentric muscular activity

NASA Technical Reports Server (NTRS)

Styf, J.; Ballard, R.; Aratow, M.; Crenshaw, A.; Watenpaugh, D.; Hargens, A. R.

1995-01-01

Intramuscular pressures, electromyography (EMG) and torque generation during isometric, concentric and eccentric maximal isokinetic muscle activity were recorded in 10 healthy volunteers. Pressure and EMG activity were continuously and simultaneously measured side by side in the tibialis anterior and soleus muscles. Ankle joint torque and position were monitored continuously by an isokinetic dynamometer during plantar flexion and dorsiflexion of the foot. The increased force generation during eccentric muscular activity, compared with other muscular activity, was not accompanied by higher intramuscular pressure. Thus, this study demonstrated that eccentric muscular activity generated higher torque values for each increment of intramuscular pressure. Intramuscular pressures during antagonistic co-activation were significantly higher in the tibilis anterior muscle (42-46% of maximal agonistic activity) compared with the soleus muscle (12-29% of maximal agonistic activity) and was largely due to active recruitment of muscle fibers. In summary, eccentric muscular activity creates higher torque values with no additional increase of the intramuscular pressure compared with concentric and isometric muscular activity.

Microexplosions initiated by a microwave capillary torch on a metal surface at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritsinin, S. I.; Davydov, A. M.; Kossyi, I. A., E-mail: kossyi@fpl.gpi.ru

2015-07-15

The interaction of the plasma of a microwave capillary argon torch with a metal surface was studied experimentally. It is shown that the interaction of the plasma jet generated by the capillary plasma torch with the metal in atmospheric-pressure air leads to the initiation of microexplosions (sparks) on the metal surface. As a result, the initially smooth surface acquires a relief in the form of microtips and microcraters. The possibility of practical application of the observed phenomenon is discussed.

Frequency Modulation and Spatiotemporal Stability of the sCPG in Preterm Infants with RDS

PubMed Central

Barlow, Steven M.; Burch, Mimi; Venkatesan, Lalit; Harold, Meredith; Zimmerman, Emily

2012-01-01

The nonnutritive suck (NNS) is an observable and accessible motor behavior which is often used to make inference about brain development and pre-feeding skill in preterm and term infants. The purpose of this study was to model NNS burst compression pressure dynamics in the frequency and time domain among two groups of preterm infants, including those with respiratory distress syndrome (RDS, N = 15) and 17 healthy controls. Digitized samples of NNS compression pressure waveforms recorded at a 1-week interval were collected 15 minutes prior to a scheduled feed. Regression analysis and ANOVA revealed that healthy preterm infants produced longer NNS bursts and the mean burst initiation cycle frequencies were higher when compared to the RDS group. Moreover, the initial 5 cycles of the NNS burst manifest a frequency modulated (FM) segment which is a significant feature of the suck central pattern generator (sCPG), and differentially expressed in healthy and RDS infants. The NNS burst structure revealed significantly lower spatiotemporal index values for control versus RDS preterm infants during FM, and provides additional information on the microstructure of the sCPG which may be used to gauge the developmental status and progression of oromotor control systems among these fragile infants. PMID:22888359

Polytropic scaling of a flow Z-pinch

NASA Astrophysics Data System (ADS)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.; Weed, J. R.

2015-11-01

The ZaP Flow Z-Pinch project investigates the use of velocity shear to mitigate MHD instabilities. The ZaP-HD experiment produces 50 cm long pinches of varying radii. The power to the experiment is split between the plasma formation and acceleration process and the pinch assembly and compression process. Once the pinch is formed, low magnetic fluctuations indicate a quiescent, long-lived pinch. The split power supply allows more control of the pinch current than previous machine iterations, with a designed range from 50 to 150 kA. Radial force balance leads to the Bennett relation which indicates that as the pinch compresses due to increasing currents, the plasma pressure and/or linear density must change. Through ion spectroscopy and digital holographic interferometry coupled with magnetic measurements of the pinch current, the components of the Bennett relation can be fully measured. A scaling relation is then assumed to follow a polytrope as the pinch pressure, initially approximately 250 kPa, increases from an initially formed state to much higher values, approaching 100 MPa. A preliminary analysis of pinch scaling is shown corroborating with other diagnostics on the machine along with extrapolations to required currents for an HEDLP machine. This work is supported by grants from the U.S. Department of Energy and the U.S. National Nuclear Security Administration.

Microstructure evolution and tensile properties of Zr-2.5wt%Nb pressure tubes processed from billets with different microstructures

NASA Astrophysics Data System (ADS)

Kapoor, K.; Saratchandran, N.; Muralidharan, K.

1999-02-01

Starting with identical ingots, billets having different microstructures were obtained by three different processing methods for fabrication of Zr-2.5wt%Nb pressure tubes. The billets were further processed by hot extrusion and cold Pilger tube reducing to the finished product. Microstructural characterization was done at each stage of processing. The effects of the initial billet microstructure on the intermediate and final microstructure and mechanical property results were determined. It was found that the structure at each stage and the final mechanical properties depend strongly on the initial billet microstructure. The structure at the final stage consists of elongated alpha zirconium grains with a network of metastable beta zirconium phase. Some of this metastable phase transforms into stable beta niobium during thermomechanical processing. Billets with quenched structure resulted in less beta niobium at the final stage. The air cooled billets resulted in a large amount of beta niobium. The tensile properties, especially the percentage elongation, were found to vary for the different methods. Higher percentage elongation was observed for billets having quenched structure. Extrusion and forging did not produce any characteristic differences in the properties. The results were used to select a process flow sheet which yields the desired mechanical properties with suitable microstructure in the final product.

Elevation correction factor for absolute pressure measurements

NASA Technical Reports Server (NTRS)

Panek, Joseph W.; Sorrells, Mark R.

1996-01-01

With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

Modified femoral pressuriser generates a longer lasting high pressure during cement pressurisation

PubMed Central

2011-01-01

Background The strength of the cement-bone interface in hip arthroplasty is strongly related to cement penetration into the bone. A modified femoral pressuriser has been investigated, designed for closer fitting into the femoral opening to generate higher and more constant cement pressure compared to a commercial (conventional) design. Methods Femoral cementation was performed in 10 Sawbones® models, five using the modified pressuriser and five using a current commercial pressuriser as a control. Pressure during the cementation was recorded at the proximal and distal regions of the femoral implant. The peak pressure and the pressure-time curves were analysed by student's t-test and Two way ANOVA. Results The modified pressuriser showed significantly and substantially longer durations at higher cementation pressures and slightly, although not statistically, higher peak pressures compared to the conventional pressuriser. The modified pressuriser also produced more controlled cement leakage. Conclusion The modified pressuriser generates longer higher pressure durations in the femoral model. This design modification may enhance cement penetration into cancellous bone and could improve femoral cementation. PMID:22004662

Phase transformation dependence on initial plastic deformation mode in Si via nanoindentation

DOE PAGES

Wong, Sherman; Haberl, Bianca; Williams, James S.; ...

2016-09-30

Silicon in its diamond-cubic phase is known to phase transform to a technologically interesting mixture of the body-centred cubic and rhombohedral phases under nanoindentation pressure. In this study, we demonstrate that during plastic deformation the sample can traverse two distinct pathways, one that initially nucleates a phase transformation while the other initially nucleates crystalline defects. These two pathways remain distinct even after sufficient pressure is applied such that both deformation mechanisms are present within the sample. Here, it is further shown that the indents that initially nucleate a phase transformation generate larger, more uniform volumes of the phase transformed materialmore » than indents that initially nucleate crystalline defects.« less

A Microstructural Comparison of the Initial Growth of AIN and GaN Layers on Basal Plane Sapphire and SiC Substrates by Low Pressure Metalorganic Chemical Vapor Depositon

NASA Technical Reports Server (NTRS)

George, T.; Pike, W. T.; Khan, M. A.; Kuznia, J. N.; Chang-Chien, P.

1994-01-01

The initial growth by low pressure metalorganic chemical vapor deposition and subsequent thermal annealing of AIN and GaN epitaxial layers on SiC and sapphire substrates is examined using high resolution transmission electron microscopy and atomic force microscopy.

Evolution of Abnormally Low Pressure at Bravo Dome and its Implications for Carbon Capture and Storage (CCS)

NASA Astrophysics Data System (ADS)

Akhbari, D.; Hesse, M. A.

2015-12-01

Carbon capture and storage allows reductions of the rapidly rising CO2 from fossil fuel-based power generation, if large storage rates and capacities can be achieved. The injection of large fluid volumes at high rates leads to a build-up of pore-pressure in the storage formation that may induce seismicity and compromise the storage security. Many natural CO2 fields in midcontinent US, in contrast, are under-pressured rather than over-pressured suggesting that natural processes reduce initial over-pressures and generate significant under-pressures. The question is therefore to understand the sequence of process(es) that allow the initial over-pressure to be eliminated and the under-pressure to be maintained over geological periods of time. We therefore look into pressure evolution in Bravo Dome, one of the largest natural CO2 accumulations in North America, which stores 1.3 Gt of CO2. Bravo Dome is only 580-900 m deep and is divided into several compartments with near gas-static pressure (see Figure). The pre-production gas pressures in the two main compartments that account for 70% of the mass of CO2 stored at Bravo Dome are more than 6 MPa below hydrostatic pressure. Here we show that the under-pressure in the Bravo Dome CO2 reservoir is maintained by hydrological compartmentalization over millennial timescales and generated by a combination of processes including cooling, erosional unloading, limited leakage into overlying formations, and CO2 dissolution into brine. Herein, we introduce CO2 dissolution into brine as a new process that reduce gas pressure in a compartmentalized reservoir and our results suggest that it may contribute significantly to reduce the initial pressure build-up due to injection. Bravo Dome is the first documented case of pressure drop due to CO2 dissolution. To have an accurate prediction of pressure evolution in Bravo Dome, our models must include geomechanics and thermodynamics for the reservoir while they account for the pressure changes due to the CO2 dissolution.

The angiotensin II receptor type 1b is the primary sensor of intraluminal pressure in cerebral artery smooth muscle cells.

PubMed

Pires, Paulo W; Ko, Eun-A; Pritchard, Harry A T; Rudokas, Michael; Yamasaki, Evan; Earley, Scott

2017-07-15

The angiotensin II receptor type 1b (AT 1 R b ) is the primary sensor of intraluminal pressure in cerebral arteries. Pressure or membrane-stretch induced stimulation of AT 1 R b activates the TRPM4 channel and results in inward transient cation currents that depolarize smooth muscle cells, leading to vasoconstriction. Activation of either AT 1 R a or AT 1 R b with angiotensin II stimulates TRPM4 currents in cerebral artery myocytes and vasoconstriction of cerebral arteries. The expression of AT 1 R b mRNA is ∼30-fold higher than AT 1 R a in whole cerebral arteries and ∼45-fold higher in isolated cerebral artery smooth muscle cells. Higher levels of expression are likely to account for the obligatory role of AT 1 R b for pressure-induced vasoconstriction . ABSTRACT: Myogenic vasoconstriction, which reflects the intrinsic ability of smooth muscle cells to contract in response to increases in intraluminal pressure, is critically important for the autoregulation of blood flow. In smooth muscle cells from cerebral arteries, increasing intraluminal pressure engages a signalling cascade that stimulates cation influx through transient receptor potential (TRP) melastatin 4 (TRPM4) channels to cause membrane depolarization and vasoconstriction. Substantial evidence indicates that the angiotensin II receptor type 1 (AT 1 R) is inherently mechanosensitive and initiates this signalling pathway. Rodents express two types of AT 1 R - AT 1 R a and AT 1 R b - and conflicting studies provide support for either isoform as the primary sensor of intraluminal pressure in peripheral arteries. We hypothesized that mechanical activation of AT 1 R a increases TRPM4 currents to induce myogenic constriction of cerebral arteries. However, we found that development of myogenic tone was greater in arteries from AT 1 R a knockout animals compared with controls. In patch-clamp experiments using native cerebral arterial myocytes, membrane stretch-induced cation currents were blocked by the TRPM4 inhibitor 9-phenanthrol in both groups. Further, the AT 1 R blocker losartan (1 μm) diminished myogenic tone and blocked stretch-induced cation currents in cerebral arteries from both groups. Activation of AT 1 R with angiotensin II (30 nm) also increased TRPM4 currents in smooth muscle cells and constricted cerebral arteries from both groups. Expression of AT 1 R b mRNA was ∼30-fold greater than AT 1 R a in cerebral arteries, and knockdown of AT 1 R b selectively diminished myogenic constriction. We conclude that AT 1 R b , acting upstream of TRPM4 channels, is the primary sensor of intraluminal pressure in cerebral artery smooth muscle cells. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Different components of blood pressure are associated with increased risk of atherosclerotic cardiovascular disease versus heart failure in advanced chronic kidney disease

PubMed Central

Bansal, Nisha; McCulloch, Charles E.; Lin, Feng; Robinson-Cohen, Cassianne; Rahman, Mahboob; Kusek, John W.; Anderson, Amanda H.; Xie, Dawei; Townsend, Raymond R.; Lora, Claudia M.; Wright, Jackson; Go, Alan S.; Ojo, Akinlolu; Alper, Arnold; Lustigova, Eva; Cuevas, Magda; Kallem, Radhakrishna; Hsu, Chi-yuan

2016-01-01

Blood pressure is a modifiable risk for cardiovascular disease (CVD). Among hemodialysis patients, there is a U-shaped association between blood pressure and risk of death. However, few studies have examined the association between blood pressure and CVD in patients with stage 4 and 5 chronic kidney disease. Here we studied 1,795 Chronic Renal Insufficiency Cohort (CRIC) Study participants with estimated glomerular filtration rate under 30 ml/min/1.73 m2 and not on dialysis. The association of systolic (SBP), diastolic (DBP) and pulse pressure with risk of physician-adjudicated atherosclerotic CVD (stroke, myocardial infarction or peripheral arterial disease) and heart failure were tested using Cox regression adjusted for demographics, comorbidity and medications. There was a significant association with higher SBP (adjusted hazard ratio 2.04 [95% confidence interval: 1.46, 2.84]) for SBP over 140 vs under 120 mmHg, higher DBP (2.52 [1.54, 4.11]) for DBP over 90 vs under 80 mmHg and higher pulse pressure (2.67 [1.82, 3.92]) for pulse pressure over 68 vs under 51 mmHg with atherosclerotic CVD. For heart failure, there was a significant association with higher pulse pressure only (1.42 [1.05, 1.92]) for pulse pressure over 68 vs under 51 mmHg, but not for SBP or DBP. Thus, among participants with stage 4 and 5 chronic kidney disease, there was an independent association between higher SBP, DBP and pulse pressure with risk of atherosclerotic CVD, while only higher pulse pressure was independently associated with greater risk of heart failure. Further trials are needed to determine whether aggressive reduction of blood pressure reduces the risk of CVD events in patients with stage 4 and 5 chronic kidney disease. PMID:27717485

Cold Helium Pressurization for Liquid Oxygen / Liquid Methane Propulsion Systems: Fully-Integrated Initial Hot-Fire Test Results

NASA Technical Reports Server (NTRS)

Morehead, R. L.; Atwell, M. J.; Melcher, J. C.; Hurlbert, E. A.

2016-01-01

A prototype cold helium active pressurization system was incorporated into an existing liquid oxygen (LOX) / liquid methane (LCH4) prototype planetary lander and hot-fire tested to collect vehicle-level performance data. Results from this hot-fire test series were used to validate integrated models of the vehicle helium and propulsion systems and demonstrate system effectiveness for a throttling lander. Pressurization systems vary greatly in complexity and efficiency between vehicles, so a pressurization performance metric was also developed as a means to compare different active pressurization schemes. This implementation of an active repress system is an initial sizing draft. Refined implementations will be tested in the future, improving the general knowledge base for a cryogenic lander-based cold helium system.

76 FR 33213 - High Pressure Steel Cylinders from the People's Republic of China: Initiation of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-08

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-977)] High Pressure Steel... (``Department'') received a petition concerning imports of high pressure steel cylinders (``steel cylinders...\\ (``Petitioner''). See Petitions for the Imposition of Antidumping and Countervailing Duties: High Pressure Steel...

76 FR 59658 - High Pressure Steel Cylinders From the People's Republic of China: Postponement of Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-27

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-977] High Pressure Steel... (``Department'') initiated an antidumping duty investigation on high pressure steel cylinders from the People's... for this investigation is currently due no later than October 18, 2011. \\1\\ See High Pressure Steel...

Introducing the Pressure-Sensing Palatograph--The Next Frontier in Electropalatography

ERIC Educational Resources Information Center

Murdoch, Bruce; Goozee, Justine; Veidt, Martin; Scott, Dion; Meyers, Ian

2004-01-01

Primary Objective. To extend the capabilities of current electropalatography (EPG) systems by developing a pressure-sensing EPG system. An initial trial of a prototype pressure-sensing palate will be presented. Research Design. The processes involved in designing the pressure sensors are outlined, with Hall effect transistors being selected. These…

Study on Fluid-solid Coupling Mathematical Models and Numerical Simulation of Coal Containing Gas

NASA Astrophysics Data System (ADS)

Xu, Gang; Hao, Meng; Jin, Hongwei

2018-02-01

Based on coal seam gas migration theory under multi-physics field coupling effect, fluid-solid coupling model of coal seam gas was build using elastic mechanics, fluid mechanics in porous medium and effective stress principle. Gas seepage behavior under different original gas pressure was simulated. Results indicated that residual gas pressure, gas pressure gradient and gas low were bigger when original gas pressure was higher. Coal permeability distribution decreased exponentially when original gas pressure was lower than critical pressure. Coal permeability decreased rapidly first and then increased slowly when original pressure was higher than critical pressure.

A Nurse-Initiated Perioperative Pressure Injury Risk Assessment and Prevention Protocol.

PubMed

Meehan, Anita J; Beinlich, Nancy R; Hammonds, Tracy L

2016-12-01

Pressure injuries negatively affect patients physically, emotionally, and economically. Studies report that pressure injuries occur in 69% of inpatients who have undergone a surgical procedure while hospitalized. In 2012, we created a nurse-initiated, perioperative pressure injury risk assessment measure for our midwestern, urban, adult teaching hospital. We retrospectively applied the risk assessment to a random sample of 350 surgical patients which validated the measure. The prospective use of the risk assessment and prevention measures in 350 surgical patients resulted in a 60% reduction in pressure injuries compared with the retrospective group. Our findings support the use of a multipronged approach for the prevention of health care-associated pressure injuries in the surgical population, which includes assessment of risk, implementation of evidence-based prevention interventions for at-risk patients, and continuation of prevention beyond the perioperative setting to the nursing care unit. Copyright © 2016 AORN, Inc. Published by Elsevier Inc. All rights reserved.

An approach to constrained aerodynamic design with application to airfoils

NASA Technical Reports Server (NTRS)

Campbell, Richard L.

1992-01-01

An approach was developed for incorporating flow and geometric constraints into the Direct Iterative Surface Curvature (DISC) design method. In this approach, an initial target pressure distribution is developed using a set of control points. The chordwise locations and pressure levels of these points are initially estimated either from empirical relationships and observed characteristics of pressure distributions for a given class of airfoils or by fitting the points to an existing pressure distribution. These values are then automatically adjusted during the design process to satisfy the flow and geometric constraints. The flow constraints currently available are lift, wave drag, pitching moment, pressure gradient, and local pressure levels. The geometric constraint options include maximum thickness, local thickness, leading-edge radius, and a 'glove' constraint involving inner and outer bounding surfaces. This design method was also extended to include the successive constraint release (SCR) approach to constrained minimization.

The Collection of Ice in Jet A-1 Fuel Pipes

NASA Astrophysics Data System (ADS)

Maloney, Thomas C.

Ice collection and blockages in fuel systems have been of interest to the aerospace community since their discovery in the late 1950's when a B-52 crashed. A recent growth of interest was provoked by several incidents that occurred within the last few years. This study seeks to understand the underlying principles of ice growth in fuel flow systems. Tests were performed in a recirculated fuel system with a fuel tank that held approximately 115 gallons of Jet A-1 fuel and ice accumulation was observed in two removable test pipes. The setup was in an altitude chamber capable of -60 °F and the experiments involved full scale flow components. Initially, tests were done to better understand the system and variables that effected accumulation. First, initial conditions within the test pipes were varied. Next, pipe geometry, pipe surface properties, initial water content of the fuel and heat transfer from the fuel pipe were varied. As a result of the tests, observations were made about other effects involved in the study. The effects include: the result of sequentially run tests, the effect of the fuel on the freezing temperature of the entrained water, the effect of ice accumulation on pipe welds, and the effect of the test pipe entrance and exit flow conditions on ice accumulation. The results of initial tests were qualitative. Later quantitative tests were done to demonstrate the dependence of temperature, Reynolds number, and heat transfer on ice accumulation. Tests were quantified with a pressure increase across the pipe sections that was normalized by the expected theoretical initial pressure. As a result of these tests the effect of contamination in the fuel was revealed. For ease of reference, the initial tests were called "stage I" and the later tests were called "stage II". The results of stage I showed that accumulation of soft ice was greatest when a layer of hard ice had initially formed on the pipe surface. Stainless steel collected more ice than Teflon® and there was a lack of a preferential accumulation region downstream of a pipe bend. A greater heat transfer from the pipe increased ice accumulation for aluminum that was made rough with 80 grit sand paper, and for Teflon®. Water was shown to collect in the pipe system as the number of tests increased and the freeze temperature of either the hard or soft ice was about 0 °C. Finally, results of "stage I" tests showed that stainless steel pipe welds were a preferred sight for ice to accumulate. Repeatability was done first in stage II and the normalized pressure increase for two 3/42 un-insulated pipe tests were within 7%. Normalized pressure increase across a pipe was shown to increase as Reynolds number decreased. A 50% increase in Reynolds number led to a 40% decrease in characteristic normalized pressure increase (CNPI). Tests were done at three temperatures and ice accumulated the most at -11 °C. The CNPI at -11 °C was about three times greater than the CNPI at -7.4 °C and about sixty times greater than the CNPI at -19.4 C. A greater heat transfer from the fuel pipe increased ice accumulation. For the amount of time that the tests ran, the total normalized pressure increase was about .9 greater for an un-insulated pipe than for an insulated pipe. Contamination in the fuel increased the amount of soft ice that collected in the system. The CNPI for the more contaminated fuel was more than double the case with less contaminated fuel. Possible solutions for the prevention or decrease of ice accumulation in aircraft fuel systems based on the results of this study are insulated pipes, a change in the type of pipe material, a higher fuel flow rate and cleaner fuel. The fuel temperature could also be altered to avoid temperatures where the most ice accumulates.

Stable fetal hemodynamics measured by Doppler flow after initiation of anti-hypertensive treatment with methyldopa in pregnant women with diabetes.

PubMed

Pedersen, Berit Woetmann; Ringholm, Lene; Damm, Peter; Tabor, Ann; Søgaard, Kirsten; Hellmuth, Ellinor; Mathiesen, Elisabeth R

2016-01-01

To evaluate whether initiation of anti-hypertensive treatment with methyldopa affects fetal hemodynamics in women with pregestational diabetes. Prospective study of unselected singleton pregnant women with diabetes (seven type 1 and two type 2 diabetes), normal blood pressure and kidney function at pregnancy booking. Methyldopa treatment was initiated at blood pressure >135/85 mmHg and/or urinary albumin excretion (UAE) >300 mg/g creatinine. Pulsatility indices (PI) of the uterine, umbilical, middle cerebral arteries before and 1 week after initiation of methyldopa treatment (250 mg three times daily) was performed and the cerebro-placental ratio (CPR) was calculated. Methyldopa treatment was initiated at median 249 (range 192-260) gestational days, mainly due to gestational hypertension (n = 7). Blood pressure declined from 142 (112-156)/92 (76-103) mmHg before to 129 (108-144)/82 (75-90) mmHg after initiation of methyldopa treatment (p = 0.11 and 0.04 for systolic and diastolic blood pressure, respectively). There were no significant changes in the umbilical artery PI (0.82 (0.72-1.40) versus 0.87 (0.64-0.95), p = 0.62) or CPR (1.94 (0.96-2.33) versus 1.78 (1.44-2.76), (p = 0.73). Gestational age was 265 (240-270) d. Apgar scores were normal. Stable Doppler flow velocity waveforms were documented after initiation of methyldopa treatment for pregnancy-induced hypertensive disorders in this cohort of pregnant women with pregestational diabetes.

Diabetes and blood pressure (image)

MedlinePlus

People with diabetes have a higher risk for heart attacks and strokes. Your doctor or nurse should check your blood pressure ... People with diabetes have a higher risk for heart attacks and strokes. Your doctor or nurse should check your blood pressure ...

Initiation of Insensitive High Explosives Using Multiple Wave Interactions

NASA Astrophysics Data System (ADS)

Francois, Elizabeth

Insensitive High Explosives (IHEs) increase safety in many types of weapons. However, the safety comes at the cost of performance. Initiation of IHE requires large boosters and powerful detonators as well. Multipoint initiation is being utilized to exploit explosive wave interactions to create overdriven states, greatly facilitating the initiation of IHEs. This presentation will focus on recent explosive experiments where the minimum spot size for single-point initiation in PBX 9502 was determined. Below this threshold, PBX 9502 could not be initiated. This was then expanded to three initiation points, which were smaller this threshold. Measurements of the velocity and pressure of the wave interactions were measured using Photon Doppler Velocimetry (PDV). Initiation was observed, and the resulting pressures at the double and triple points were found to be above the CJ state for PBX 9502. Further testing will be performed using cutback experiments to isolate the overdriven state, and quantify the duration of the phenomenon.

Development of Scatterometer-Derived Surface Pressures

NASA Astrophysics Data System (ADS)

Hilburn, K. A.; Bourassa, M. A.; O'Brien, J. J.

2001-12-01

SeaWinds scatterometer-derived wind fields can be used to estimate surface pressure fields. The method to be used has been developed and tested with Seasat-A and NSCAT wind measurements. The method involves blending two dynamically consistent values of vorticity. Geostrophic relative vorticity is calculated from an initial guess surface pressure field (AVN analysis in this case). Relative vorticity is calculated from SeaWinds winds, adjusted to a geostrophic value, and then blended with the initial guess. An objective method applied minimizes the differences between the initial guess field and scatterometer field, subject to regularization. The long-term goal of this project is to derive research-quality pressure fields from the SeaWinds winds for the Southern Ocean from the Antarctic ice sheet to 30 deg S. The intermediate goal of this report involves generation of pressure fields over the northern hemisphere for testing purposes. Specifically, two issues need to be addressed. First, the most appropriate initial guess field will be determined: the pure AVN analysis or the previously assimilated pressure field. The independent comparison data to be used in answering this question will involve data near land, ship data, and ice data that were not included in the AVN analysis. Second, the smallest number of pressure observations required to anchor the assimilated field will be determined. This study will use Neumann (derivative) boundary conditions on the region of interest. Such boundary conditions only determine the solution to within a constant that must be determined by a number of anchoring points. The smallness of the number of anchoring points will demonstrate the viability of the general use of the scatterometer as a barometer over the oceans.

Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath

NASA Astrophysics Data System (ADS)

Rivera-Rivera, Luis A.; Wagner, Albert F.; Sewell, Thomas D.; Thompson, Donald L.

2015-01-01

Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is ˜100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane "simultaneously" colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed-phase densities.

Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivera-Rivera, Luis A.; Wagner, Albert F.; Sewell, Thomas D.

2015-01-07

Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is similar to 100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit withmore » the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane "simultaneously" colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed-phase densities. (C) 2015 AIP Publishing LLC.« less

Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath.

PubMed

Rivera-Rivera, Luis A; Wagner, Albert F; Sewell, Thomas D; Thompson, Donald L

2015-01-07

Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is ∼100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane "simultaneously" colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed-phase densities.

Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivera-Rivera, Luis A.; Sewell, Thomas D.; Thompson, Donald L.

2015-01-07

Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is ∼100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatzmore » function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane “simultaneously” colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed-phase densities.« less

Documentation of the Tonge-Ramesh Material Model for Release 2015-06-05-152756

DTIC Science & Technology

2015-10-01

crush curves showing pressure required to initiate pore collapse for pure hydrostatic loading as a function of distension for the 2 different granular...Illustration of the crush curves showing pressure required to initiate pore collapse for pure hydrostatic loading as a function of distension for the 2...is an additional yield surface that depends on only the hydrostatic pressure (p = −1/3tr(σ)). 13 It is defined by fφ(P, J GP , J) =  P Pc−P0

Direct observation of electrothermal instability structures on intensely Ohmically heated aluminum with current flowing in a surface skin layer

NASA Astrophysics Data System (ADS)

Awe, Thomas

2017-10-01

Implosions on the Z Facility assemble high-energy-density plasmas for radiation effects and ICF experiments, but achievable stagnation pressures and temperatures are degraded by the Magneto-Rayleigh-Taylor (MRT) instability. While the beryllium liners (tubes) used in Magnetized Liner Inertial Fusion (MagLIF) experiments are astonishingly smooth (10 to 50 nm RMS roughness), they also contain distributed micron-scale resistive inclusions, and large MRT amplitudes are observed. Early in the implosion, an electrothermal instability (ETI) may provide a perturbation which greatly exceeds the initial surface roughness of the liner. Resistive inhomogeneities drive nonuniform current density and Joule heating, resulting in locally higher temperature, and thus still higher resistivity. Such unstable temperature and pressure growth produce density perturbations which seed MRT. For MagLIF liners, ETI seeding of MRT has been inferred by evaluating late-time MRT, but a direct observation of ETI is not made. ETI is directly observed on the surface of 1.0-mm-diameter solid Al rods pulsed to 1 MA in 100 ns via high resolution gated optical imaging (2 ns temporal and 3 micron spatial resolution). Aluminum 6061 alloy rods, with micron-scale resistive inclusions, consistently first demonstrate overheating from distinct, 10-micron-scale, sub-eV spots, which 5-10 ns later merge into azimuthally stretched elliptical spots and discrete strata (40-100 microns wide by 10 microns tall). Axial plasma filaments form shortly thereafter. Surface plasma can be suppressed for rods coated with dielectric, enabling extended study of the evolution of stratified ETI structures, and experimental inference of ETI growth rates. This fundamentally new and highly 3-dimensional dataset informs ETI physics, including when the ETI seed of MRT may be initiated.

Changes in Energy Metabolism after Continuous Positive Airway Pressure for Obstructive Sleep Apnea.

PubMed

Tachikawa, Ryo; Ikeda, Kaori; Minami, Takuma; Matsumoto, Takeshi; Hamada, Satoshi; Murase, Kimihiko; Tanizawa, Kiminobu; Inouchi, Morito; Oga, Toru; Akamizu, Takashi; Mishima, Michiaki; Chin, Kazuo

2016-09-15

Disrupted energy homeostasis in obstructive sleep apnea (OSA) may lead to weight gain. Paradoxically, treating OSA with continuous positive airway pressure (CPAP) may also promote weight gain, although the underlying mechanism remains unclear. To explore the underlying mechanism by which patients with OSA gain weight after CPAP. A comprehensive assessment of energy metabolism was performed in 63 newly diagnosed OSA study participants (51 men; 60.8 ± 10.1 yr; apnea-hypopnea index >20 h(-1)) at baseline, CPAP initiation, and at a 3-month follow-up. Measurements included polysomnography, body weight, body composition, basal metabolic rate (BMR), hormones (norepinephrine, cortisol, leptin, ghrelin, insulin-like growth factor-1), dietary intake, eating behavior, and physical activity. BMR significantly decreased after CPAP (1,584 kcal/d at baseline, 1,561 kcal/d at CPAP initiation, and 1,508 kcal/d at follow-up; P < 0.001), whereas physical activity and total caloric intake did not significantly change. In multivariate regression, baseline apnea-hypopnea index, Δurine norepinephrine, and CPAP adherence were significant predictors of ΔBMR. The weight gainers had higher leptin levels, lower ghrelin levels, and higher eating behavior scores than the non-weight gainers, indicating a positive energy balance and disordered eating behavior among the weight gainers. Among the parameters related to energy metabolism, increased caloric intake was a particularly significant predictor of weight gain. Although a reduction in BMR after CPAP predisposes to a positive energy balance, dietary intake and eating behavior had greater impacts on weight change. These findings highlight the importance of lifestyle modifications combined with CPAP. Clinical trial registered with http://www.umin.ac.jp/english/ (UMIN000012639).

Oxygen dependency of germinating Brassica seeds

NASA Astrophysics Data System (ADS)

Park, Myoung Ryoul; Hasenstein, Karl H.

2016-02-01

Establishing plants in space, Moon or Mars requires adaptation to altered conditions, including reduced pressure and composition of atmospheres. To determine the oxygen requirements for seed germination, we imbibed Brassica rapa seeds under varying oxygen concentrations and profiled the transcription patterns of genes related to early metabolism such as starch degradation, glycolysis, and fermentation. We also analyzed the activity of lactate dehydrogenase (LDH) and alcohol dehydrogenase (ADH), and measured starch degradation. Partial oxygen pressure (pO2) greater than 10% resulted in normal germination (i.e., protrusion of radicle about 18 hours after imbibition) but lower pO2 delayed and reduced germination. Imbibition in an oxygen-free atmosphere for three days resulted in no germination but subsequent transfer to air initiated germination in 75% of the seeds and the root growth rate was transiently greater than in roots germinated under ambient pO2. In hypoxic seeds soluble sugars degraded faster but the content of starch after 24 h was higher than at ambient oxygen. Transcription of genes related to starch degradation, α-amylase (AMY) and Sucrose Synthase (SUS), was higher under ambient O2 than under hypoxia. Glycolysis and fermentation pathway-related genes, glucose phosphate isomerase (GPI), 6-phosphofructokinase (PFK), fructose 1,6-bisphosphate aldolase (ALD), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), pyruvate decarboxylase (PDC), LDH, and ADH, were induced by low pO2. The activity of LDH and ADH was the highest in anoxic seeds. Germination under low O2 conditions initiated ethanolic fermentation. Therefore, sufficient oxygen availability is important for germination before photosynthesis provides necessary oxygen and the determination of an oxygen carrying capacity is important for uniform growth in space conditions.

Low-cost thin-film absorber/evaporator for an absorption chiller. Final report, May 1992-April 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lowenstein, A.; Sibilia, M.

1993-04-01

The feasibility of making the absorber and evaporator of a small lithium-bromide absorption chiller from thin plastic films was studied. Tests were performed to measure (1) pressure limitations for a plastic thin-film heat exchanger, (2) flow pressure-drop characteristics, (3) air permeation rates across the plastic films, and (4) creep characteristics of the plastic films. Initial tests were performed on heat exchangers made of either low-density polyethylene (LDPE), high-density polyethylene (HDPE), or a LDPE/HDPE blend. While initial designs for the heat exchanger failed at internal pressures of only 5 to 6 psi, the final design could withstand pressures of 34 psi.

Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.

PubMed

Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

2010-03-01

Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure.

Effect of treatment pressure on treatment quality and bending properties of red pine lumber

Treesearch

Patricia K. Lebow; Stan T. Lebow; William J. Nelson

2010-01-01

Although higher treatment pressures have the potential to improve preservative penetration, higher pressures may possibly result in greater reduction in mechanical properties. The present study evaluated the effect of treatment pressure on the treatment quality and mechanical properties of red pine (Pinus resinosa Ait.) lumber. End-matched sections of red pine lumber...

Under Pressure: Financial Impact of the Hospital-Acquired Conditions Initiative. A Statewide Analysis of Pressure Ulcer Development and Payment

PubMed Central

Meddings, Jennifer A.; Reichert, Heidi; Rogers, Mary A. M.; Hofer, Timothy P.; McMahon, Laurence F.; Grazier, Kyle L.

2017-01-01

OBJECTIVE To assess the financial impact of the 2008 Hospital-Acquired Conditions Initiative’s pressure ulcer payment changes on Medicare and other payors. DESIGN, SETTING AND PARTICIPANTS Retrospective before-and-after study of all-payor statewide administrative data for >2.4 million annual adult discharges from 311 nonfederal acute-care California hospitals in 2007 and 2009, using the Healthcare Cost and Utilization Project State Inpatient Datasets. We assessed how often and by how much the 2008 payment changes for pressure ulcers affected hospital payment. MEASUREMENTS Pressure ulcer rates and hospital payment changes RESULTS Hospital-acquired pressure ulcer rates were very low (0.28%) in 2007 and 2009; present-on-admission pressure ulcer rates increased from 2.35% in 2007 to 3.00% in 2009. By clinical stage of pressure ulcer (available in 2009), hospital-acquired stage III–IV ulcers occurred in 603 discharges (0.02%); 60,244 discharges (2.42%) contained other pressure ulcer diagnoses. Payment removal for stage III–IV hospital-acquired ulcers reduced payment in 75 (0.003%) discharges for a statewide payment decrease of $310,444 (0.001%) for all payors and $199,238 (0.001%) for Medicare. For all other pressure ulcers, the Hospital-Acquired Conditions Initiative reduced hospital payment in 20,246 (0.81%) cases (including 18,953 cases with present-on-admission ulcers) reducing statewide payment by $62,538,586 (0.21%) for all payors and $47,237,984 (0.32%) for Medicare. CONCLUSION The total financial impact of the 2008 payment changes for pressure ulcers was negligible. Most payment decreases occurred by removal of comorbidity payments for present-on-admission pressure ulcers other than stages III–IV. The removal of payment for hospital-acquired stage III–IV ulcers was more than 200 times less than the removal of payment for other types of pressure ulcers that occurred in implementation of the Hospital-Acquired Conditions Initiative. PMID:26140454

Strain-dependent permeability of volcanic rocks.

NASA Astrophysics Data System (ADS)

Farquharson, Jamie; Heap, Michael; Baud, Patrick

2016-04-01

We explore permeability evolution during deformation of volcanic materials using a suite of rocks with varying compositions and physical properties (such as porosity ϕ). 40 mm × 20 mm cylindrical samples were made from a range of extrusive rocks, including andesites from Colima, Mexico (ϕ˜0.08; 0.18; 0.21), Kumamoto, Japan (ϕ˜0.13), and Ruapehu, New Zealand (ϕ˜0.15), and basalt from Mt Etna, Italy (ϕ˜0.04). Gas permeability of each sample was measured before and after triaxial deformation using a steady-state benchtop permeameter. To study the strain-dependence of permeability in volcanic rocks, we deformed samples to 2, 3, 4, 6, and 12 % axial strain at a constant strain rate of 10-5 s-1. Further, the influence of failure mode - dilatant or compactant - on permeability was assessed by repeating experiments at different confining pressures. During triaxial deformation, porosity change of the samples was monitored by a servo-controlled pore fluid pump. Below an initial porosity of ˜0.18, and at low confining pressures (≤ 20 MPa), we observe a dilatant failure mode (shear fracture formation). With increasing axial strain, stress is accommodated by fault sliding and the generation of ash-sized gouge between the fracture planes. In higher-porosity samples, or at relatively higher confining pressures (≥ 60 MPa), we observe compactant deformation characterised by a monotonous decrease in porosity with increasing axial strain. The relative permeability k' is given by the change in permeability divided by the initial reference state. When behaviour is dilatant, k' tends to be positive: permeability increases with progressive deformation. However, results suggest that after a threshold amount of strain, k' can decrease. k' always is negative (permeability decreases during deformation) when compaction is the dominant behaviour. Our results show that - in the absence of a sealing or healing process - the efficiency of a fault to transmit fluids is correlated to the degree of strain to which is subjected. Volcanic processes such as dome extrusion, which involve progressive strain on complex fault systems, have been seen to cause fault sliding and the prolific generation of fault gouge. Our results indicate that the permeability of these faults will tend to remain constant or increase during continued extrusion, allowing magmatic gases to readily outgas through permeable fault architectures despite the generation and accumulation of gouge. On the other hand, deeper regions of the edifice that will typically be compacting due to the relatively higher confining pressures, will exhibit a continuous decrease in permeability. The interplay between permeability-increasing and permeability-decreasing processes within the edifice is likely to influence outgassing and eruptive cycles at active volcanoes.

Factors associated with elevated plateau pressure in patients with acute lung injury receiving lower tidal volume ventilation.

PubMed

Prescott, Hallie C; Brower, Roy G; Cooke, Colin R; Phillips, Gary; O'Brien, James M

2013-03-01

Lung-protective ventilation with lower tidal volume and lower plateau pressure improves mortality in patients with acute lung injury and acute respiratory distress syndrome. We sought to determine the incidence of elevated plateau pressure in acute lung injury /acute respiratory distress syndrome patients receiving lower tidal volume ventilation and to determine the factors that predict elevated plateau pressure in these patients. We used data from 1398 participants in Acute Respiratory Distress Syndrome Network trials, who received lower tidal volume ventilation (≤ 6.5mL/kg predicted body weight). We considered patients with a plateau pressure greater than 30cm H2O and/or a tidal volume less than 5.5mL/kg predicted body weight on study day 1 to have "elevated plateau pressure." We used logistic regression to identify baseline clinical variables associated with elevated plateau pressure and to develop a model to predict elevated plateau pressure using a subset of 1,188 patients. We validated the model in the 210 patients not used for model development. Medical centers participating in Acute Respiratory Distress Syndrome Network clinical trials. None. Of the 1,398 patients in our study, 288 (20.6%) had elevated plateau pressure on day 1. Severity of illness indices and demographic factors (younger age, greater body mass index, and non-white race) were independently associated with elevated plateau pressure. The multivariable logistic regression model for predicting elevated plateau pressure had an area under the receiving operator characteristic curve of 0.71 for both the developmental and the validation subsets. acute lung injury patients receiving lower tidal volume ventilation often have a plateau pressure that exceeds Acute Respiratory Distress Syndrome Network goals. Race, body mass index, and severity of lung injury are each independently associated with elevated plateau pressure. Selecting a smaller initial tidal volume for non-white patients and patients with higher severity of illness may decrease the incidence of elevated plateau pressure. Prospective studies are needed to evaluate this approach.

A Trial of Wound Irrigation in the Initial Management of Open Fracture Wounds.

PubMed

Bhandari, Mohit; Jeray, Kyle J; Petrisor, Brad A; Devereaux, P J; Heels-Ansdell, Diane; Schemitsch, Emil H; Anglen, Jeff; Della Rocca, Gregory J; Jones, Clifford; Kreder, Hans; Liew, Susan; McKay, Paula; Papp, Steven; Sancheti, Parag; Sprague, Sheila; Stone, Trevor B; Sun, Xin; Tanner, Stephanie L; Tornetta, Paul; Tufescu, Ted; Walter, Stephen; Guyatt, Gordon H

2015-12-31

The management of open fractures requires wound irrigation and débridement to remove contaminants, but the effectiveness of various pressures and solutions for irrigation remains controversial. We investigated the effects of castile soap versus normal saline irrigation delivered by means of high, low, or very low irrigation pressure. In this study with a 2-by-3 factorial design, conducted at 41 clinical centers, we randomly assigned patients who had an open fracture of an extremity to undergo irrigation with one of three irrigation pressures (high pressure [>20 psi], low pressure [5 to 10 psi], or very low pressure [1 to 2 psi]) and one of two irrigation solutions (castile soap or normal saline). The primary end point was reoperation within 12 months after the index surgery for promotion of wound or bone healing or treatment of a wound infection. A total of 2551 patients underwent randomization, of whom 2447 were deemed eligible and included in the final analyses. Reoperation occurred in 109 of 826 patients (13.2%) in the high-pressure group, 103 of 809 (12.7%) in the low-pressure group, and 111 of 812 (13.7%) in the very-low-pressure group. Hazard ratios for the three pairwise comparisons were as follows: for low versus high pressure, 0.92 (95% confidence interval [CI], 0.70 to 1.20; P=0.53), for high versus very low pressure, 1.02 (95% CI, 0.78 to 1.33; P=0.89), and for low versus very low pressure, 0.93 (95% CI, 0.71 to 1.23; P=0.62). Reoperation occurred in 182 of 1229 patients (14.8%) in the soap group and in 141 of 1218 (11.6%) in the saline group (hazard ratio, 1.32, 95% CI, 1.06 to 1.66; P=0.01). The rates of reoperation were similar regardless of irrigation pressure, a finding that indicates that very low pressure is an acceptable, low-cost alternative for the irrigation of open fractures. The reoperation rate was higher in the soap group than in the saline group. (Funded by the Canadian Institutes of Health Research and others; FLOW ClinicalTrials.gov number, NCT00788398.).

Novel High Temperature Capacitive Pressure Sensor Utilizing SiC Integrated Circuit Twin Ring Oscillators

NASA Technical Reports Server (NTRS)

Scardelletti, M.; Neudeck, P.; Spry, D.; Meredith, R.; Jordan, J.; Prokop, N.; Krasowski, M.; Beheim, G.; Hunter, G.

2017-01-01

This paper describes initial development and testing of a novel high temperature capacitive pressure sensor system. The pressure sensor system consists of two 4H-SiC 11-stage ring oscillators and a SiCN capacitive pressure sensor. One oscillator has the capacitive pressure sensor fixed at one node in its feedback loop and varies as a function of pressure and temperature while the other provides a pressure-independent reference frequency which can be used to temperature compensate the output of the first oscillator. A two-day repeatability test was performed up to 500C on the oscillators and the oscillator fundamental frequency changed by only 1. The SiCN capacitive pressure sensor was characterized at room temperature from 0 to 300 psi. The sensor had an initial capacitance of 3.76 pF at 0 psi and 1.75 pF at 300 psi corresponding to a 54 change in capacitance. The integrated pressure sensor system was characterized from 0 to 300 psi in steps of 50 psi over a temperature range of 25 to 500C. The pressure sensor system sensitivity was 0.113 kHzpsi at 25C and 0.026 kHzpsi at 500C.

Thermally-driven Coupled THM Processes in Shales

NASA Astrophysics Data System (ADS)

Rutqvist, J.

2017-12-01

Temperature changes can trigger strongly coupled thermal-hydrological-mechanical (THM) processes in shales that are important to a number of subsurface energy applications, including geologic nuclear waste disposal and hydrocarbon extraction. These coupled processes include (1) direct pore-volume couplings, by thermal expansion of trapped pore-fluid that triggers instantaneous two-way couplings between pore fluid pressure and mechanical deformation, and (2) indirect couplings in terms of property changes, such as changes in mechanical stiffness, strength, and permeability. Direct pore-volume couplings have been studied in situ during borehole heating experiments in shale (or clay stone) formations at Mont Terri and Bure underground research laboratories in Switzerland and France. Typically, the temperature changes are accompanied with a rapid increase in pore pressure followed by a slower decrease towards initial (pre-heating) pore pressure. Coupled THM modeling of these heater tests shows that the pore pressure increases because the thermal expansion coefficient of the fluid is much higher than that of the porous clay stone. Such thermal pressurization induces fluid flow away from the pressurized area towards areas of lower pressure. The rate of pressure increase and magnitude of peak pressure depends on the rate of heating, pore-compressibility, and permeability of the shale. Modeling as well as laboratory experiments have shown that if the pore pressure increase is sufficiently large it could lead to fracturing of the shale or shear slip along pre-existing bedding planes. Another set of data and observations have been collected associated with studies related to concentrated heating and cooling of oil-shales and shale-gas formations. Heating may be used to enhance production from tight oil-shale, whereas thermal stimulation has been attempted for enhanced shale-gas extraction. Laboratory experiments on shale have shown that strength and elastic deformation modulus decreases with temperature while the rate creep deformations increase with temperature. Such temperature dependency also affects the well stability and zonal sealing across shale layers.

Chemical Compositional Analysis of Catalytic Hydroconversion Products of Heishan Coal Liquefaction Residue

PubMed Central

Wu, Yajun; Zhang, Shuangquan; Yang, Xiaoqin; Wei, Xianyong

2017-01-01

Liquefaction residue of Heishan bituminous coal (HLR) was subject to two hydroconversion reactions under 5 MPa initial pressure of hydrogen at 300°C for 3 h, without catalyst and with acid supported catalyst (ASC), respectively. The reaction products were analyzed with gas chromatography/mass spectrometer (GC/MS). The results show that 222 organic compounds were detected totally in the products and they can be divided into alkanes, aromatic hydrocarbons (AHCs), phenols, ketones, ethers, and other species (OSs). The yield of hydroconversion over the ASC is much higher than that without catalyst. The most abundant products are aromatic hydrocarbons in the reaction products from both catalytic and noncatalytic reactions of HLR. The yield of aromatic hydrocarbons in the reaction product from hydroconversion with the ACS is considerably higher than that from hydroconversion without a catalyst. PMID:28250770

Hemodynamic deterioration precedes onset of ventricular tachyarrhythmia after Heartmate II implantation.

PubMed

Yaksh, Ameeta; Kik, Charles; Knops, Paul; Zwiers, Korinne; van Ettinger, Maarten J B; Manintveld, Olivier C; de Wijs, Marcel C J; van der Kemp, Peter; Bogers, Ad J J C; de Groot, Natasja M S

2016-07-08

Early postoperative ventricular tachyarrhythmia (PoVT) after left ventricular assist device (LVAD) implantation are common and associated with higher mortality-rates. At present, there is no data on initiation of these PoVT and the role of alterations in cardiac hemodynamics. A LVAD was implanted in a patient with end-stage heart failure due to a ischemic cardiomyopathy. Alterations in cardiac rhythm and hemodynamics preceding PoVT-episodes during the first five postoperative days were examined by using continuous recordings of cardiac rhythm and various hemodynamic parameters. All PoVT (N=120) were monomorphic, most often preceded by short-long-short-sequences or regular SR and initiated by ventricular runs. Prior to PoVT, mean arterial pressure decreased; heart rate and ST-segments deviations increased. PoVT are caused by different underlying electrophysiological mechanisms. Yet, they are all monomorphic and preceded by hemodynamic deterioration due to myocardial ischemia.

Can Nor'wester events initiate stratospheric moistening?

NASA Astrophysics Data System (ADS)

Ganguly, Nandita D.; Chakraborty, Rohit; Maitra, Animesh

2017-11-01

The possibility of stratospheric moistening being initiated by deep convective Nor'wester events has been investigated over a period of three years spanning from 2013 to 2015 at a tropical location Kolkata, in India using radiosonde and satellite data. The back trajectories, instability indices, outgoing long wave radiation (OLR), convective available potential energy (CAPE), geopotential height maps, vertical pressure velocity, specific humidity, wind vectors and precipitable water vapour (PWV) have been examined to assess the convective activity prevailing over the atmosphere during these events. Increase in specific humidity, wind velocity at various levels of the lower atmosphere and CAPE values indicate an upwelling of moist air from the troposphere to lower stratosphere during Nor'westers. Decrease in OLR and large differences in the values of instability indices, relative humidity and precipitable water vapour during Nor'westers compared to normal convection also signify high intensity of convection and hence the possibility of higher stratospheric moistening during Nor'wester events.

Combined hydraulic and regenerative braking system

DOEpatents

Venkataperumal, R.R.; Mericle, G.E.

1979-08-09

A combined hydraulic and regenerative braking system and method for an electric vehicle is disclosed. The braking system is responsive to the applied hydraulic pressure in a brake line to control the braking of the vehicle to be completely hydraulic up to a first level of brake line pressure, to be partially hydraulic at a constant braking force and partially regenerative at a linearly increasing braking force from the first level of applied brake line pressure to a higher second level of brake line pressure, to be partially hydraulic at a linearly increasing braking force and partially regenerative at a linearly decreasing braking force from the second level of applied line pressure to a third and higher level of applied line pressure, and to be completely hydraulic at a linearly increasing braking force from the third level to all higher applied levels of line pressure.

Combined hydraulic and regenerative braking system

DOEpatents

Venkataperumal, Rama R.; Mericle, Gerald E.

1981-06-02

A combined hydraulic and regenerative braking system and method for an electric vehicle, with the braking system being responsive to the applied hydraulic pressure in a brake line to control the braking of the vehicle to be completely hydraulic up to a first level of brake line pressure, to be partially hydraulic at a constant braking force and partially regenerative at a linearly increasing braking force from the first level of applied brake line pressure to a higher second level of brake line pressure, to be partially hydraulic at a linearly increasing braking force and partially regenerative at a linearly decreasing braking force from the second level of applied line pressure to a third and higher level of applied line pressure, and to be completely hydraulic at a linearly increasing braking force from the third level to all higher applied levels of line pressure.

A Workflow for Subsurface Pressure Control in Geological CO2 Storage: Optimization of Brine Extraction

NASA Astrophysics Data System (ADS)

Birkholzer, J. T.; Gonzalez-Nicolas, A.; Cihan, A.

2017-12-01

Industrial-scale injection of CO2 into the subsurface increases the fluid pressure in the reservoir, sometimes to the point that the resulting stress increases must be properly controlled to prevent potential damaging impacts such as fault activation, leakage through abandoned wells, or caprock fracturing. Brine extraction is one approach for managing formation pressure, effective stress, and plume movement in response to CO2 injection. However, the management of the extracted brine adds cost to the carbon capture and sequestration operations; therefore optimizing (minimizing) the extraction volume of brine is of great importance. In this study, we apply an adaptive management approach that optimizes extraction rates of brine for pressure control in an integrated optimization framework involving site monitoring, model calibration, and optimization. We investigate the optimization performance as affected by initial site characterization data and introduction of newly acquired data during the injection phase. More accurate initial reservoir characterization data reduce the risk of pressure buildup damage with better estimations of initial extraction rates, which results in better control of pressure during the overall injection time periods. Results also show that low frequencies of model calibration and optimization with the new data, especially at early injection periods, may lead to optimization problems, either that pressure buildup constraints are violated or excessively high extraction rates are proposed. These optimization problems can be eliminated if more frequent data collection and model calibration are conducted, especially at early injection time periods. Approaches such as adaptive pressure management may constitute an effective tool to manage pressure buildup under uncertain and unknown reservoir conditions by minimizing the brine extraction volumes while not exceeding critical pressure buildups of the reservoir.

[Three-dimensional finite element analysis of maxillary anterior teeth retraction force system in light wire technique].

PubMed

Zhang, Xiangfeng; Wang, Chao; Xia, Xi; Deng, Feng; Zhang, Yi

2015-06-01

This study aims to construct a three-dimensional finite element model of a maxillary anterior teeth retraction force system in light wire technique and to investigate the difference of hydrostatic pressure and initial displacement of upper anterior teeth under different torque values of tip back bend. A geometric three-dimensional model of the maxillary bone, including all the upper teeth, was achieved via CT scan. To construct the force model system, lingual brackets and wire were constructed by using the Solidworks. Brackets software, and wire were assembled to the teeth. ANASYS was used to calculate the hydrostatic pressure and the initial displacement of maxillary anterior teeth under different tip-back bend moments of 15, 30, 45, 60, and 75 Nmm when the class II elastic force was 0.556 N. Hydrostatic pressure was concentrated in the root apices and cervical margin of upper anterior teeth. Distal tipping and relative intrusive displacement were observed. The hydrostatic pressure and initial displacement of upper canine were greater than in the central and lateral incisors. This hydrostatic pressure and initial intrusive displacement increased with an increase in tip-back bend moment. Lingual retraction force system of maxillary anterior teeth in light wire technique can be applied safely and controllably. The type and quantity of teeth movement can be controlled by the alteration of tip-back bend moment.