Pressure Collapse Research Articles

Mechanical ventilation in adult respiratory distress syndrome

Adult respiratory distress syndrome is characterized by a high mortality rate despite enormous progress in the technology of ventilators, improvement in the diagnostic tools and in pharmacological treatment. Mechanical ventilation, although necessary, is generally considered to be one of the main causes of further injury to diseased lungs, reducing the possibility of recovery (ventilatorinduced lung injury). Ventilator-induced lung injury is the consequence of a sustained increase in alveolar pressure (barotrauma), alveolar distension (volotrauma) or alveolar collapse and decollapse with cycling during inspiration and expiration (shear stress trauma). Experimental and clinical studies suggest that the optimal ventilatory treatment should combine the use of a reduced tidal volume with consequent permissive hypercapnia to reduce volotrauma, low inspiratory pressures to reduce barotrauma, and an adequate level of positive end-expiratory pressure to recruit as much collapsed lung parenchyma as possible to reduce shear stress trauma. However, because adult respiratory distress syndrome is a syndrome of different aetiologies, a general optimal ventilatory strategy applicable to patients with adult respiratory distress syndrome probably does not exist. Indeed, it would be better to tailor it taking into account the pathophysiology of individual patients and the primitive cause of the disease itself. Only a better knowledge of the patients' underlying pathophysiology in the different kinds of adult respiratory distress syndrome will help in tailoring the least damaging ventilation programme for each individual patient.

Pressure Collapse of Kondo Gap in Kondo Compound CeRhSb

The effect of pressure on the electrical resistivity of CeRhSb has been studied up to 80 kbar in order to elucidate the electronic Properties of CeRhSb at low temperature. It is found that the Kondo temperature increases with pressure and gap is quenched at P =80 kbar, showing a maximum around 30 kbar.

Unraveling the Mysteries of Proprietary Connections

The purpose of this article is to provide some insight into the potential users of proprietary connections and to facilitate a rational selection process and procurement procedure. First, it must be noted that the standard and commonly used API casing connections [short, round thread casing and coupling (STC); long, round thread casing and coupling (LTC); buttress thread casing and coupling (BTC)] and API tubing connection EUE-8R (external upset ends, eight round thread tubing and coupling) can provide reliable service for the vast majority of well drilled and completed. Proprietary connections can and have been misapplied at considerable expense; for example, 9 5/8 drilling (intermediate/protective) casing. API BTC works more than adequately in drilling-mud environments. There is no need to use a proprietary connection for such service. In fact, pin nose metal-to-metal seal proprietary connections in this type of service can be less reliable than the API BTC connection since the metal-to-metal seal is much more damage prone than the thread seal of API BTC. Also, very reliable leak resistance, even to gas, is obtained with tin plated BTC couplings.

Observation of transient cooling phenomenon in liquid helium by an optical measurement

Transient cooling of liquid Helium before the bubble formation is sustained bythe force balancing of the surface tension of liquid Helium and inner pressure of the superheat layer created nearby the heating surface. To observe the transient cooling phenomenon, the conventional thermometer measurement is not suitable technique because of response and sensitivity problem. For this reason, we have developed an optical observation technique instead which can respond within a few μsec. The observed data indicates that bubble formation phenomenon is triggered by the pressure collapse event in the superheat layer, and also liquid Helium can sustain no bubble cooling up to a few hundred μJ/cm 2 input energy.

Further study of high speed single free jets

AbstractExperiments to study the behaviour of a compressible free jet issuing from an axisymmetric convergent nozzle are reported. Detailed measurements of the mean flow field for subsonic, sonic and underexpanded sonic jets was made within the pressure ratio range of 1.13 to 4. The results show that the spread and decay rates of the jet vary significantly with pressure ratio. The results further indicate the radial velocity/total pressure collapse within the two-dimensional shear layer data. The underexpanded jet propagates to a greater distance downstream than the low speed jets; this leads to enhancement of the far field mixing.

Dynamics of coronary occlusion in the pathogenesis of myocardial infarction

In most coronary artery stenoses in humans, lumen size decreases in response to acute vasoconstriction, reduced aortic pressure or passive collapse. Because the effects of vasoconstriction and plaque rupture with thrombus formation are additive, in some cases total cessation of flow may result from only minimal obstruction by thrombus. This hypothesis was investigated with use of a previously developed model of the coronary circulation in which the pressure drop across and flow through an arterial stenosis were determined by standard hemodynamic equations. The vessel wall was assumed to be composed of pliable and rigid sections, as is the case in most st arterial stenoses in humans. The computer analysis was conducted for a rigid stenosis and for a dynamic stenosis in which proximal artery constriction and distal collapse were simulated. Plaque rupture with subsequent thrombus formation was simulated as a decrease in lumen area without effect on the arterial wall.Compared with a dynamic stenosis, a rigid stenosis required a significantly larger thrombus for vessel occlusion. Thrombus formation equal to the nonobstructed area of the lumen was required to occlude a rigid vessel; a 60% stenotic vessel required a 40% plaque rupture with thrombus formation for occlusion. However, for a dynamic stenosis, if vasoconstriction and passive collapse were simulated, small plaque ruptures led to vessel occlusion: a 60% stenotic vessel required only a 12% plaque rupture with thrombus formation for occlusion. This analysis indicates that even mild coronary lesions may be responsible for myocardial infarction, suggesting that vasomotion may be a very important element in the pathogenesis of most myocardial infarcts.

Normal-mode excitation from stellar collapse to a black hole: Odd-parity perturbations.

Odd-parity perturbations of stellar models are studied numerically, with an emphasis on the gravitational radiation produced during collapse to a black hole. The stellar models are produced by a May-White stellar collapse code using a polytropic equation of state. A wide range of collapse models are studied, ranging from stars without presure (dust collapse) to stars which collapse and then bounce at radii near the Schwarzschild radius. For all collapse models studied, the quasinormal modes (QNM's) of the black hole are excited to varying degrees after an initial, non-QNM transient wave form. Models with greater pressure collapse more slowly and generally emit a lower-amplitude ringing radiation. Furthermore, models with greater pressure are generally found to radiate less of their total gravitational energy from the normal-mode excitation than models with less pressure

Experimental studies at Karlsruhe and Oak Ridge of transplutonium metals and compounds under pressure

At Karlsruhe, the structural behavior of the first four transplutonium metals and two Bk-Cf alloys has been studied as a function of pressure in diamond anvil cells using X-ray diffraction. The sequence of structures exhibited as pressure is increased is d.h.c.p. → c.c.p. → orthorhombic. In addition a distorted c.c.p. phase is observed in americium, Bk 0.40Cf 0.60 and californium between the c.c.p. and orthorhombic phases. The volume collapse and transformation to the lower symmetry orthorhombic structure are indicative of the onset of delocalization of the 5f electrons in these materials. The highest delocalization pressure and largest volume collapse occur in curium metal, reflecting its stable half-filled 5f 7 electron configuration. Diamond anvil cells have also been used at Oak Ridge to contain AmI 3, CfBr 3 and CfCl 3 under pressure for investigation by absorption spectro-photometry. Both AmI 3 and CfBr 3 exhibit pressure-induced, irreversible phase transformations to the PuBr 3-type orthorhombic structure, a denser form of these compounds. Thus the driving force for these transformations is more efficient crystal packing. Both hexagonal (to 22 GPa) and orthorhombic (to 35 GPa) CfCl 3 exhibit only reversible spectral changes with pressure. This probably reflects their nearly identical room temperature and pressure (RTF) unit cell volumes. In both cases the spectra obtained are consistent with a continuous alteration of the RTF structure with pressure; physical compression seems to make a given f → f transition easier. Additional data are being sought to elucidate more completely the behavior of CfCl 3 under pressure.

Studies of Acylamino Acid Monolayers by π-A curves. I. Acylamino Acids with Alkyl Side Chain

Abstract In order to obtain some information regarding the behavior of amino acids at interfaces, the monolayers of N-acyl l-α-amino acids with alkyl side chains on water have been investigated by measuring the surface pressure vs. area curves at various temperatures. It has been found that N-octadecanoylglycine and N-octadecanoylalanine form the condensed monolayers over the whole surface pressure range measured, N-octadecanoylvaline forms the expanded monolayer at a lower surface pressure, and N-octadecanoylleucine and N-octadecanoylisoleucine collapse at high surface pressures. From the experimental results, it has been concluded that the amino acid residue with a long side chain occupies a large area at the air/water interface and interferes with the condensation of acylamino acid monolayer. It has also been found that the methyl esterification of amino acid residue makes the monolayer state unstable although it produces less significant effect than the increase in the alkyl chain length of amino acid residue.

Provincial Independence vs. National Rule: A Case Study of Szechwan in the 1920's and 1930's

For many reasons, including the importance of local geographic variation, twentieth century Chinese phenomena such as “warlordism” must be examined in individual sub-national cases. Szechwanese provincial militarists maintained a high degree of independence from outside control and stood aloof from central government politics from the end of the Northern Expedition until 1935. However, a combination of communist military pressure and provincial economic collapse finally induced Szechwan's leading militarist to seek Nanking's help. From early 1935, the National Government attempted to bring Szechwan within its sphere of military, economic, and political influence. In its struggle with entrenched provincial militarists, Nanking employed a complex set of reforms, at the heart of which were measures for the restricting of local administration and the extension of formal administrative control into local society. When the Sino-Japanese War Erupted in July 1937, however, Nanking had achieved only very partial success. The Nationalists' final peacetime opportunity to solve the modern dilemma of central vs. sub-national power in China had passed.

Provincial Independence vs. National Rule: A Case Study of Szechwan in the 1920's and 1930's

For many reasons, including the importance of local geographic variation, twentieth century Chinese phenomena such as “warlordism” must be examined in individual sub-national cases. Szechwanese provincial militarists maintained a high degree of independence from outside control and stood aloof from central government politics from the end of the Northern Expedition until 1935. However, a combination of communist military pressure and provincial economic collapse finally induced Szechwan's leading militarist to seek Nanking's help. From early 1935, the National Government attempted to bring Szechwan within its sphere of military, economic, and political influence. In its struggle with entrenched provincial militarists, Nanking employed a complex set of reforms, at the heart of which were measures for the restricting of local administration and the extension of formal administrative control into local society. When the Sino-Japanese War Erupted in July 1937, however, Nanking had achieved only very partial success. The Nationalists' final peacetime opportunity to solve the modern dilemma of central vs. sub-national power in China had passed.

Project Sterling: Subsurface phenomenology measurements near a decoupled nuclear event

The purpose of the Sterling event, a 380-ton nuclear explosion detonated in a spherical cavity, was to test the decoupling theory for nuclear explosives detonated in explosively generated cavities. Measurements of stress history, cavity pressure, and cavity collapse were attempted in the very close-in region between 17 and 52 meters from the cavity center; free-field measurements of particle velocity and acceleration were made in the immediate region between 52 and 660 meters as measured from the cavity center. Peak accelerations measured over this interval ranged from 150 to 0.2 g; peak velocities ranged from 0.13 to 0.01 m/sec. The assumption of cube-root scaling was used in the analysis of the reduced displacement potentials and their Fourier transforms to obtain a free-field decoupling ratio of about 100 for a frequency range near 10 Hz. Above 10 Hz, the decoupling ratio drops rapidly to about 20. These results are in reasonably good agreement with the decoupling theory.

Pressure collapse in oxygen storage under zero-G.

A mathematical study has identified the operating and design conditions that may lead to pressure collapse in a supercritical, cryogenic oxygen storage system. Pressure collapse is attributed to unexpected mixing of warmer and colder stored oxygen, and physical property behavior which leads to consequent loss of pressure is identified. The extent and seriousness of pressure losses are indicated by the results of numerical case studies based on a mathematical model of a 5-ft capacity, supercritical, cryogenic oxygen storage system. The capabilities of a simple on-off heater system to control pressure were determined as functions of operating pressure range and limit, withdrawal rate, heating rate, and heater and oxygen-withdrawal locations. An electric heater (or heaters) uniformly distributed over the inside surface of the tank would be much better than a heater in the center of the tank. A maximum operating pressure between 70 and 100 atm is desirable.

The Role of Thermal Instabilities in Star Formation

Thermal instabilities role in star formation, discussing intercloud medium, magnetic pressure and gravitational collapse

Underwater sounds of pinnipeds : Schevill, William E., William A. Watkins and Carleton Ray, 1963 Science, 141 (3575): 50–53

Marine mammals are repeatedly exposed to elevated extra-thoracic pressure and alveolar collapse during diving and readily experience alveolar expansion upon inhalation – a unique capability as compared to terrestrial mammals. How marine mammal lungs overcome the challenges of frequent alveolar collapse and recruitment remains unknown. Recent studies indicate that pinniped lung surfactant has more anti-adhesive components compared to terrestrial mammals, which would aid in alveolar opening. However, pulmonary surfactant composition has not yet been investigated in odontocetes, whose physiology and diving behavior differ from pinnipeds. The aim of this study was to investigate the phosphatidylcholine (PC) composition of lung surfactants from various marine mammals and compare these to a terrestrial mammal. We found an increase in anti-adhesive PC species in harp seal (Pagophilus groenlandicus) and California sea lion (Zalophus californianus) compared to dog (Canus lupus familiaris), as well as an increase in the fluidizing PCs 16:0/14:0 and 16:0/16:1 in pinnipeds compared to odontocetes. The harbor porpoise (a representative of the odontocetes) did not have higher levels of fluidizing PCs compared to dog. Our preliminary results support previous findings that pinnipeds may have adapted unique surfactant compositions that allow them to dive at high pressures for extended periods without adverse effects. Future studies will need to investigate the differences in other surfactant components to fully assess the surfactant composition in odontocetes.

Collapse of protein monolayers

Collapse phenomena in monolayers of two proteins (pepsin and bovine albumin) and one synthetic polypeptide (polyalanine) have been quantitatively examined. Up to moderate surface pressures (ca. 30 dynes cm. −1), the process appears to be reversible and to involve the expulsion from the surface of small segments of the polypeptide chain. At much higher pressures collapse is no longer reversible, and a coagulum is formed.

A Severe Reaction to Tetraethylammonium Chloride

TETRAETHYLAMMONIUM salts have been found to block efferent autonomic impulses at both the sympathetic and parasympathetic ganglions.1 , 2 Because of this action, the drug is being employed in a variety of clinical studies. The effect of tetraethylammonium ion in man has been described by Lyons and his associates,3 4 5 who have administered the drug over a thousand times with "very few serious effects." They make particular reference to the occasional profound fall in blood pressure and transient vascular collapse in patients with malignant hypertension who have received tetraethylammonium parenterally. Otherwise, there has been no report of a severe untoward reaction to this . . .

BLOOD PRESSURE MAINTENANCE IN SPINAL ANESTHESIA

A fall of blood pressure accompanies each spinal anesthesia. It is the one possible danger associated with this form of anesthesia and may cause death. Its low point is usually ten minutes after the injection, and most fatalities have occurred at that time. After fifteen minutes, one is working away from the danger point, not toward it as in other general anesthetics. Given a reliable method of holding up blood pressure for the first fifteen minutes, and modern spinal anesthesia in trained hands is free of danger. Epinephrin given intravenously is the only reliable drug in desperate cases of blood pressure collapse. Promptly and properly administered, it will hold every case until the body vasomotor tone is naturally restored. But the occasional near fatality which every user of spinal anesthetics has seen has resulted in the clinical trial of many drugs and measures to anticipate this blood pressure drop. Various