Internal Pressure Changes Research Articles

A Hormone Effecting Immobilization in Pupariating Fly Larvae

ABSTRACT The haemolymph of 1–2 h old (orange) puparia of Sarcophaga bullata contains a factor (PIF) which immobilizes mature fly larvae, most strongly 6–24 h before pupariation. It has all the properties of a protein: a mol. wt. of between 100000 and 300000 daltons, it is heat labile, non-dialysable, destroyed by trypsin, and precipitated by NH4SO4. It is possibly identical with the anterior retraction factor (ARF) because the activity of both always went hand in hand. Its action seems to be unspecific in cyclorrhaphous flies. Much about PIF has been learned from studying changes in internal haemolymph pressure of larvae injected with PIF before and during pupariation. Its function is probably to shut off muscular activity after the puparium is completed. It may also function in very small dosages at the beginning of pupariation when the activity of the larvae decreases.

Development of the Critical Gas Saturation

Introduction The critical or threshold gas saturation is a specific property of the porous medium and internal fluids. property of the porous medium and internal fluids. Compared with the experimental research on the subject, I the theory of gas saturation development to its critical value and the significance of this growth on reservoir performance have received little attention. For a volumetric reservoir - i.e., one with negligible water influx and negligible change of rock porosity with internal fluid pressure change, and with porosity with internal fluid pressure change, and with water production and expansion also considered zero - the usual procedure to compute gas saturation development is the material balance equation: Bo - Boi + Bg (Rsi- Rs) Np=------------------------ N,..............(1) Bo + Bg (Rp - Rs) with average reservoir pressure below the bubble-point pressure and Sg less than Sgc. In Eq. 1, 1 Np Rp = --- RsdNp.........................(2) Np 0 In words, only the solution gas has been produced, since the gas saturation remains insufficient for gas flow. The recovery percentage is obtained from the material balance equation; the gas saturation is obtained from the recovery percentage. Eq. 1 is an involved integral equation of a type unknown to me. Np is a self-dependent variable with the limit of the integral in the denominator - Eq. 2. In Ref. 2, Eq. 1 is not presented in the form shown but as a numerical solution procedure that simplifies the presentation. In fact, this numerical solution is an everyday affair for the practicing engineer. An alternative formula is presented. presented. JPT P. 907

Pressure dependence of polymer chain conformational parameters

Configurational statistics of chain molecules relates the average spatial configuration and the other configuration-dependent properties of a chain to the relative free energy AF of rotational isomers for each rotatable skeletal bond. The statistical weights uij = exp[ Mij/(RT)] are assigned to the pairs of conformations about adjoining bonds and are arranged as elements of statistical weight matrix’). The comparison of calculated and experimental values of configuration-dependent properties is the usual way for the assignment of statistical weights uij . Alternatively, uij can be determined from the conformational energy calculations for the compounds. Customarily, only the dependence of uij on temperature is assumed in conformational studies. For low molecular weight compounds there are many examples of the striking environmental (especially solvent) influence on conformational equilibria2). In configurational statistics this effect can be accounted for by introducing the solventdependent statistical weights uij . For example, the solvent effect on mean chain dimensions is simulated by a variation of some uij values’). It is common belief that the environmental effect on torsional potentials about single bonds and on the associated conformational free energies AF is important in polar systems only. However, there are also indications of the importance of the environmental effect on the conformational equilibria for nonpolar e.g. hydrocarbon molecule^^^^). One of the possible reasons for it is the modification of torsional potential in the condensed phase due to the different volumes of trans and gauche conformers’). In other words, the statistical weights for hydrocarbon chain molecules in the condensed phase are affected by changes of internal or external pressure or by changes of sample volume. In this paper the pressure variation of statistical weights of the polymethylene chain is estimated as a representative case of non-polar polymers.

Method of measuring low pressures within evacuated, sealed glass tubes

During the heating of evacuated and sealed glass tubes, small volumes of gas are usually evolved causing a pressure rise. A simple method of measuring these gas pressures by manometer without the necessity of opening the tube is described. The method requires that mercury and a small inner glass tube be sealed in the tube. Internal pressure changes occurring when an evacuated vitreous silica tube was heated up to 550°C are described. The maximum pressure reached in the tube was 2.5 torr.

Changes in internal pressure during puparium formation in flies

AbstractChanges in the internal pressure of fly larvae during puparium formation were measured by a method previously described. Two different types of pressure changes were recorded: (1) Reversible pulsations of various types corresponding to different kinds of muscular contractions, and (2) an irreversible increase of the pressure baseline caused by dimensional shrinkage and loss of elasticity of the cuticle, association with ultrastructural reorganization and sclerotization. The pressure pulses potentiated by neuromuscular activity are association with the initial stages of pupariation, immobilization, retraction of the anterior segments, and longitudinal body contraction, and can generate pressure peaks of up to 300 mm Hg. By contrast, the steady rise of the basic pressure during the final stages of pupariation is generated independently of muscular activity and is also independent of phenolic tanning. The basic pressure can reach levels of 100 mm Hg and is indispensable for the final rounding and smoothening of the ovoid puparium. Morphogenesis of the puparium thus can be understood as a result of a delicate concert between neuromuscular activity and structural changes in the integument.

Analysis of left ventricular behaviour in diastole by means of finite element method.

The human left ventricle in diastole can be modelled as a passive structure with incremental internal pressure change being considered as the load. Recent developments in engineering stress analysis provide techniques for predicting the behaviour of structures with complex geometry and material properties, as is the case with the left ventricle. That which is most appropriate is the finite element method which requires the use of a large digital computer. The ventricles of 2 patients have been studied during diastole, the geometries having been derived from cineangiographic data (biplane), and the pressure by means of catheter-tip manometers. Various descriptions of myocardial stress/strain relations have been assumed and applied to the left ventricular wall in order to obtain the best match between the calculated and observed deformation patterns. The manner in which the value and distribution of stiffness in the left ventricle influences the shape change can therefore be determined, and possible clinical implications deduced.

Lubricant Supply Characteristics of a Microporous Polymer

A moldable, polymeric microporous material for use as a lubricant reservoir for rolling element bearings has been studied to determine the parameters which control the rate of lubricant flow. A simplified theory is developed to predict flow rates resulting from body forces or from internal pressure changes. Experimental data and theory are in good agreement. Changes in temperature produce transient changes in flow rate due to an internal pressure change resulting from differential thermal expansion between the lubricant and the polymer matrix. The transience is followed by a steady flow rate due to body forces. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976

Measurement of CBF and carotid artery pressure compared with cerebral angiography in assessing collateral blood supply after carotid ligation.

Angiographic assessment of collateral circulation to the brain at the circle of Willis was compared with measurements of cerebral blood flow (CBF) and internal carotid artery pressure during temporary carotid clamping in the prediction of tolerance of unilateral carotid ligation as treatment for intracranial carotid aneurysms in 92 patients. From CBF studies it was predicted that a substantial number of patients (27%) would suffer severe cerebral ischemia if carotid ligation were carried out. No single angiographic feature provided this predictive information. Bilateral fetal type of posterior communication arteries were associated with significantly lower carotid artery back pressure on temporary carotid occlusion, and unilateral absence of posterior communicating arteries was related to llower CBF, but neither feature was associated with a signifiant reduction in the rate of successful carotid ligation. We believe that preliminary percutaneous digital corotid compression with electroencephalographic monitoring, followed by intraoperative measurement of the change in regional CBF and internal carotid artery pressure during temporary carotid clamping provides a safe method of selecting patients for carotid ligation. Carotid angiography with or without contralateral carotid compression is of little value in this respect.

Effects of size of fish, water temperature and water velocity on buoyancy alteration by fathead minnows, Pimephales promelas

1. 1. Fathead minnows (Pimephales promelas) alter buoyancy by changing swimbladder volume to compensate for changes in water velocity with the lowest buoyancy attained in faster water velocities. 2. 2. Extent of buoyancy adjustment is greater and rate of increase faster at 21 than at 4.5°C. 3. 3. Buoyancy is inversely related to water velocity. 4. 4. Compared to large fish, small fish make a lesser adjustment, have a higher internal pressure, and secrete gas faster during an increase in buoyancy. 5. 5. Gas secretion is used to increase swimbladder volume. 6. ]6. Changes in internal pressure occur during adjustment but do not influence the rate of adjustment.

Holographic Examination of a Composite Pressure Vessel

Abstract We have examined a composite pressure vessel using holographic interferometry. Interference patterns obtained from an internal pressure change show that there is an area of high shear strain in the knuckle area of the vessel that seems to correspond to the area of premature failure. We make several suggestions aimed at reducing the shear stress in the knuckle area.

Osmotic regulation in the marine alga, Codium decorticatum. I. Regulation of turgor pressure by control of ionic composition.

Codium decorticatum regulates its internal ionic composition and osmotic pressure in response to changes in external salinity. Over a salinity range of 23 to 37% (675 to 1120 mosmol/kg) Codium maintains a constant turgor pressure of 95 mosmol/kg (2.3 atm), observed as a constant difference between internal and external osmotic pressures. The changes in internal osmotic pressure are due to changes in intracellular inorganic ions. At 30 0/00 salinity the major intracellular ions are present in the following concentrations (mmol/kg cell H20): K+, 295; Na+, 255; Cl-, 450. At different salinities intracellular ion concentrations remain in constant proportion to the external ion concentrations, and thus the equilibrium potentials are approximately constant. The potential difference between the vacuole and seawater (-76 mV), whici is predominantly a K+ diffusion potential, is also constant with changing salinity. Comparison of the equilibrium potentials with the vacuole potential suggests that Cl- is actively absorbed and Na+ actively extruded, whereas K+ may be passively distributed between the vacuole and seawater. Turgor pressure does not change with environmental hydrostatic pressure, and increasing the external osmotic pressure with raffinose elicits a response similar to that obtained by increasing the salinity. These two results suggest that the stimulus for turgor regulation is a change in turgor pressure rather than a change in internal hydrostatic pressure or ion concentrations.

Comparative cardiac dynamic effects of dobutamine and isoproterenol in conscious instrumented dogs

The cardiac dynamic consequences were evaluated of constant infusions of dobutamine and isoproterenol at graded dose levels into conscious, healthy instrumented dogs. Measurements were made of simultaneous changes in left ventricular internal diameter, pressure, aortic pressure and rate of rise of left ventricular pressure (dP/dt), as well as the left ventricular electrogram. From these primary variables, derived variables were computed using programs in a minicomputer system. The data showed that, with increasing doses of dobutamine there were significant linear increases in all measured indexes of myocardial contractility, such as the rate of rise of left ventricular pressure at a developed isovolumic pressure of 40 mm Hg (dP/dt/P40), mean velocity of left ventricular fiber shortening, ejection fraction and stroke work. These changes in myocardial contractility occurred without changes in end-diastolic volume, mean aortic pressure or heart rate when dobutamine was infused in doses of 5 to 20 μg/kg per min. Isoproterenol also produced linear changes in indexes of myocardial contractility but in doses of 0.02 to 0.10 μg/kg per min, it produced a significantly higher heart rate at any given level of contractility than that produced by dobutamine. Cardiac minute work (heart rate × stroke work) was increased by both drugs. However, with infusions of isoproterenol the amount of cardiac minute work was significantly limited because of the changes in heart rate, whereas with dobutamine cardiac minute work could be increased to a higher level as a function of changes in myocardial contractility alone without changes in heart rate. These data suggest that dobutamine selectively increases myocardial contractility.

Adjustment of Buoyancy by Tadpole Madtom, Noturus gyrinus, and Black Bullhead, Ictalurus melas, in Response to a Change in Water Velocity

Tadopole madtom (Noturus gyrinus) and black bullhead (Ictalurus melas) adjusted buoyancy by altering swimbladder volume becoming less buoyant in current than in still. Extent of adjustment was dependent on size. Tadpole madtom adjusted buoyancy within 96–192 h but partial adjustment occurred within 12–48 h. Year 0 fish made a more rapid decrease in buoyancy than did year 1 or 2. As buoyancy was decreased year 0 and 1 tadpole madtom showed significant changes in internal pressure of swimbladder gases. Black bullhead secreted gases into the swimbladder to increase buoyancy while tadpole madtom showed no such ability.

Effects of axisymmetric loads on inflated non-linear membranes

This paper describes the effects of various external axisymmetric loads on pressurized hinged spherical membranes taking into account changes in internal pressure, volume, and temperature. “Exact” geometrical non-linearity along with generalized constitutive relations for a highly non-linearly clastic, isotropic, homogeneous, incompressible material are used in the analysis. The specialized case of a Hookean material is also treated. The non-linear equations of membrane equilibrium are derived in terms of additional finite displacements for the case of nonorthogonal curvilinear midsurface coordinates and are then specialized for the problem of an inflated hinged spherical membrane. The resulting two highly non-linear coupled second order differential equations are solved by means of a finite difference and Newton-Raphson iterative procedure. All results are presented in nondimensionalized graphical form.

Osmotic behavior of bacterial protoplasts: temperature effects.

Among protoplasts released from cells of Bacillus megaterium grown at 20, 30, or 37 C, osmotic swelling in NaCl solution at a given external osmotic pressure was greatest for protoplasts from cells grown at 20 C and least for protoplasts from cells grown at 37 C. Protoplasts from cells grown at lower temperaturs were also less stable to osmotic shock and lysed at higher external osmotic pressures than did protoplasts from cells grown at higher temperatures. But for cells grown at any one temperature, osmotic stabilization was itself temperature dependent so that the higher the ambient incubation temperature, the higher the osmotic pressure needed to prevent lysis of a given fraction of the input protoplast population. However, comparison of the osmotic stability of protoplasts from cells grown at different temperatures at various ambient incubation temperatures revealed that, except at 5 C where no differences were discerned, protoplasts from cells grown at lower temperatures still lysed at higher osmotic pressures than did those from cells grown at higher temperatures. The apparent internal osmolality (28 to 31 atm) did not vary significantly among whole cells from the three growth temperatures. Therefore, the observed differences in osmotic behavior could not be attributed to changes in internal osmotic pressure. Rather, it seemed likely that the differences were due to changes in membrane properties.

The Effect of Hydrostatic Pressure on the Yield Behavior of Thermoplastics

The effect of pressure on the yield behavior of polymeric solids was investigated at room temperature. Tests were carried out on samples of six thermoplastics; polycarbonate, polyvinyl chloride, polypropylene, polyethylene, nylon 6.6, and ABS plastics.An apparatus has been designed and constructed which allows the determination of the yield stress of a polymer specimen in thin-walled cylinder under internal pressure, while the sample is simultaneously subject to a hydrostatic external pressure. As the external pressure increases, the normal stress applied to the plane of the maximum shear stress in the thin-walled cylinder subjected to internal pressure changes from tension to compression.In the state of hydrostatic compression under high external pressure, the pressure dependence of yield stress fitted in well with Coulomb yield criterion. In the state of hydrostatic tension under low external pressure, the yield surface (the Mohr envelope for yielding) could not be explained by the Coulomb yield criterion.Furthermore, the deformation bands produced under hydrostatic pressure in polycarbonate have been examined by measuring the angles of bands after the load was removed. These bands were found to be inclined at 50° to the direction of the maximum principal stress. The angle of 50° was independent of hydrostatic pressure.

The immediate effect of changed perfusion pressure and the subsequent adaptation in the isolated ventricle of the marine gastropod [formula omitted][formula omitted], (Prosobranchia)

1. The isolated ventricle of Rapana thomasiana requires the pressure of internal perfusion if it is to beat spontaneously. 2. A change in internal perfusion pressure results in a change in the shape of the cardiac action potential.

An effect of histamine on the nictitating membrane of the cat: potentiation of the actions of adrenaline, noradrenaline and acetylcholine.

An effect of histamine on the nictitating membrane of the cat: potentiation of the actions of adrenaline, noradrenaline and acetylcholine.

Dynamic effects arising from high-speed solidification

Convective mass transfer occurs during solidification because of the difference in mass density between the participant solid and liquid phases. The relationship between interphase mass transfer and the mechanical behavior of a bounded system undergoing rapid solidification is developed from an analysis of the kinematics and dynamics of dendritic freezing. The kinematic analysis yields theoretical expressions for the displacement, velocity, and acceleration imparted to the center of mass of a constrained melt by the solidification-induced mass transfer, whereas the dynamical analysis relates the changes in external force and internal pressure with the accelerations of the solidifying body's mass center. These analyses reveal that a critical degree of supercooling exists, above which the dendrite velocity can increase without a concomitant increase in the acceleration of the center of mass, and that this condition coincides with the onset of cavitation in the specimen. Some new experiments, which provide quantitative information on the mechanical behavior of rapidly freezing bismuth melts, are then discussed. The results obtained from these experiments justify the major assumptions employed in the theory, and substantiate several of the theoretical predictions. Finally, a unified approach to solidification dynamics is presented in a discussion of the following effects: 1. (1) the emission of acoustical disturbances during solidification; 2. (2) the occurrence of an anomalous refinement in the as-cast grain size of nickel and cobalt specimens frozen from highly supercooled melts; 3. (3) the development of cavitation pits on the constrained surfaces of rapidly frozen transition metal specimens; 4. (4) the presence of pressure pulses both during and after rapid dendritic growth.

The Imaginal Ecdysis of Blowflies. Observations On the Hydrostatic Mechanisms Involved in Digging and Expansion

ABSTRACT The digging movements and the expansion process of newly emerged blowflies involve the production of positive internal pressures. During digging newly emerged blowflies produce a characteristic cycle of internal hydrostatic pressure changes which in Sarcophaga reach, at their maximum, 6 – 12 cm. of mercury. During expansion, two different pressure phenomena are detectable. First, there is a gradual rise and fall in the basic haemolymph pressure which reaches a maximum (of 6 cm. of mercury in Calliphora and 9-5 cm. in Sarcophaga) a few minutes after full wing extension and then falls to atmospheric pressure in the next 20 min. Secondly, superimposed on the basic rise there is a series of brief rhythmic pressure pulses which gradually decline and then cease about the time of full wing extension. Evidence obtained by blocking the proboscis or denervating the abdominal muscles of newly emerged flies indicates that the gradual rise in haemolymph pressure is attributable to air-swallowing and the pressure pulses to the performance of ‘muscular efforts’ (i.e. simultaneous contractions of both the ptilinal and abdominal muscles). The wing expansion of flies which have had their abdominal muscles denervated is abnormal, suggesting that at least some of these muscles play a part in bringing about normal expansion. After full wing extension has occurred (or after an operated fly has reached a point in the air-pumping cycle at which expansion would have occurred) ‘muscular efforts’ cease and digging movements can no longer be stimulated. This cessation is not due to the hardening of the cuticle and it is suggested that it is due to loss of the ability to excite the muscles concerned. Within a few days of emergence many (perhaps all) of the muscles concerned in the production of digging movements and ‘muscular efforts’ degenerate. Immediately after expansion flies eliminate large quantities of fluid via the anus. This appears to be correlated with the change from a combined hydrostatic and external skeleton to a hard exoskeleton.