Slight Increase In Pressure Research Articles

Experimental and numerical study on flow dynamics and universal characteristics of ventilated supercavities behind different cavitators

In this study, physical aspects of a ventilated supercavity behind different cavitator geometries such as the hydrodynamic characteristics, distribution of pressure within the cavity, hysteresis phenomenon, and gas leakage mechanism were qualitatively and quantitatively investigated using experimental and numerical methods. For the simulation and tunnel tests, we employed five cavitators, each with different angles (45°, 60°, 90°, 135°, and a 180° cavitator, commonly referred to as a disk cavitator), all sharing the same diameter. The results revealed that the drag force experienced on the cavitator decreased linearly with an increase in the ventilation rate, and a consistent trend was observed for all test cavitator angles. Through experimental measurements, a universal equation has been derived to predict the drag force exerted on a supercavitating vehicle employing a cavitator. In addition, the pressure distribution inside the supercavity was significantly influenced by the angle of the cavitator. The pressure kept almost unchanged in the first half of supercavity; a slight increase in pressure occurred in the remainder of the supercavity. Twin-vortex gas leakage mode was clearly observed. The distance between the two hollow vortices increased significantly, whereas the incline angle of these vortices and the horizontal line changed insignificantly.

Comparison of Normal Saline and Alkalinized 2% Lignocaine to Reduce Emergence Phenomenon and Post-Intubation Morbidities: A Prospective, Double-Blind, Randomized Study.

Endotracheal intubation for airway management in general anesthesia is associated with post-intubation morbidities due to tracheal mucosa injury caused by endotracheal tube (ETT) cuff. Nitrous oxide (N2O) diffuses into tracheal tube cuffs filled with air. The rate of diffusion of N2O through the membrane is proportional to its concentration gradient. High-volume low-pressure cuffs expand with only a slight increase in pressure until fully inflated. At this point, owing to the inelasticity of the material, the cuff pressure rises rapidly. This increased pressure can damage the tracheal mucosa. This phenomenon can be avoided, if we inflate the cuff with either a liquid or a gas mixture identical to the inspired gas and monitor the cuff pressure and volume at regular intervals. When lignocaine is used to inflate the ETT cuff, it diffuses to the underlying tracheal mucosa. Thus reducing local irritation and inflammation of the airway through its local anesthetic action. Alkalinization of lignocaine increases its rate of diffusion across the ETT cuff. It also reduces the dose of local anesthetic required to achieve the desired result. We sought to determine the benefits of filling the ETT cuff with alkalinized lignocaine 2% over normal saline, to prevent ETT-induced emergence phenomenon and reduce the incidence of post-intubation morbidities like sore throat, hoarseness, and nausea. This prospective, randomized, double-blind, and comparative study was done at a multispecialty hospital. A total of 120 individuals ofAmerican Society of Anesthesiologists (ASA) physical status 1 and 2, posted for surgery under general anesthesia, were randomly selected and divided into two groups: alkalinized 2% lignocaine group (group L) and normal saline group (group S). After induction of general anesthesia, the airway was secured with appropriate-sized ETT. The ETT cuff was inflated with either of the study media. Continuous cuff pressure monitoring was done to keep cuff pressure below 30 centimeters of water (cm of H2O), at all times. At extubation, the response was evaluated in terms of percentage change in heart rate (HR) and blood pressure from baseline, coughing, bucking, and restlessness. All the surgeries lasted more than two hours. Post-operatively, the patients were evaluated for sore throat and hoarseness, at regular intervals of up to 24 hours. ETT cuff pressure was initially less in group S, which rose to a significantly higher level at extubation, compared to group L (p <0.001). At extubation, there was a significant increase in HR and systolic blood pressure (SBP) from baseline, in group S than in group L (p <0.001 and p=0.001, respectively).The incidence of cough and restlessness was less in group L, compared to group S (p<0.001 and p=0.002, respectively). Mean extubation time and emergence time was more in group S than in group L (p<0.001). Post-operatively, the incidence and severity of sore throat were significantly higher in group S than in group L (p<0.001). Meanwhile, the incidence of hoarseness and nausea was comparable in the two groups. Continuous ETT cuff pressure monitoring helps to keep cuff pressure below tracheal mucosa capillary occlusion pressure. Filling the ETT cuff with alkalinized lignocaine further reduces extubation response and post-intubation morbidities.

Off-ball behavior in association football: A data-driven model to measure changes in individual defensive pressure

ABSTRACT This study describes an approach to evaluate the off-ball behaviour of attacking players in association football. The aim was to implement a defensive pressure model to examine an offensive player’s ability to create separation from a defender using 1411 high-intensity off-ball actions including 988 Deep Runs (DRs) DRs and 423 Change of Directions (CODs). Twenty-two official matches (14 competitive matches and 8 friendlies) of the German National Team were included in the research. To validate the effectiveness of the pressure model, each pass (n = 25,418) was evaluated for defensive pressure on the receiver at the moment of the pass and for the pass completion rate (R = −.34, p < .001). Next, after assessing the inter-rater reliability (Fleiss Kappa of 80 for DRs and 78 for CODs), three expert raters annotated all DRs and CODs that met the pre-set criteria. A time-series analysis of each DR and COD was calculated to the nearest 0.1 second, finding a slight increase in pressure from the start to the end of the off-ball actions as defenders re-established proximity to the attacker after separation was created. A linear mixed model using run type (DR or COD) as a fixed effect with the local maximum as a fixed effect on a continuous scale resulted in p < 0.001, d = 4.81, CI = 0.63 to 0.67 for the greatest decrease in pressure, p < 0.001, d = 0.143, CI = 9.18 to 10.61 for length of the longest decrease in pressure, and p < 0.001, d = 1.13, CI = 0.90 to 1.11 for the fastest rate of decrease in pressure. As these values pertain to the local maximum, situations with greater starting pressure on the attacker often led to greater subsequent decreases. Furthermore, there was a significant (p < .0001) difference between offensive and defensive positions and the number of off-ball actions. Results suggest the model can be applied to quantify and visualise the pressure exerted on non-ball-possessing players. This approach can be combined with other methods of match analysis, providing practitioners with new opportunities to measure tactical performance in football.

Numerical study of hot-gas ventilated supercavitating flow

This paper describes a numerical investigation of the characteristics of supercavitating flow using hot gas. The numerical results are validated through an experimental study under the same conditions at Chungnam National University Cavitation Tunnel. The temperature gradient, velocity profile, and pressure distribution inside the supercavity are investigated. The multiphase numerical study uses the volume of fluid method and the realizable k–ε turbulence model to solve the governing equations. The internal flow structure inside the hot-gas ventilated supercavity can be classified into three distinct regions: the hot-gas ventilation effect region, internal boundary layer, and reverse flow region. The pressure inside the supercavity remains unchanged in the region close to the cavitator, and does not depend on the temperature variation of the ventilation gas; however, a slight increase in pressure occurs in the region near the closure part of the supercavity with maximum increase of 18%. Moreover, the gas leakage mechanism of the hot-gas ventilated supercavity is found to be the twin-vortex tubes, which become a single-vortex tube as the free-stream velocity increases. The temperature distribution is concentrated in the hot-gas effect region. The hot-gas is observed to diffuse very quickly near the injection holes. The present article provides a better understanding of the fluid mechanism inside supercavities, and presents new results on the behavior of hot-gas ventilation. • Simulation of hot-gas ventilated supercavity (the highest temperature of 2773 K) is carried out. • The results reveal findings below. (1) Internal flow structure of the supercavity. (2) Pressure and temperature distributions inside the supercavity. (3) Hot-gas leakage mechanism through the twin-vortex tubes.

The influence of ClO− and acidity in the reaction between H2O2 and CuCl2

The potentially explosive reaction of hydrogen peroxide (H2O2) and copper chloride (CuCl2) was investigated. Pressure tests revealed that the reaction was strongly temperature - dependent and can easily undergo runaway reaction. Nevertheless, there was only a slight pressure increase at the low temperatures studied or when using low concentrations of CuCl2. Under the conditions generating the slight pressure increase, hypochlorite anions (ClO−) are generated and the acidity increases. As the reaction reaches completion, ClO− disappears, and the acidity decreases. Interestingly, the addition of phosphate buffer to maintain the weakly acid conditions led to a runaway reaction, and the use of basic ClO− promoted the exothermic reaction. Based on the results, acidity has a strong impact on the reaction behaviour.

Effects of a Small Increase in Carbon Dioxide Pressure during Fermentation on Wine Aroma.

The present study tested the effect of a slight increase in pressure (from 0 to 1 bar) during the fermentation on the wine aroma profile. Fermentations were carried out with a commercial dry yeast on Sangiovese juice in the absence of berry skins. The wine samples fermented under slight overpressure conditions were found to be significantly different from the control samples produced at atmospheric pressure in relation to several chemical compounds. Concentrations of many esters (i.e., isoamyl acetate, ethyl acetate, ethyl hexanoate, hexyl acetate, ethyl dodecanoate, and ethyl tetradecanoate), and acids (i.e., hexanoic acid, octanoic acid, and decanoic acid) increased, while concentrations of two acids (i.e., isobutyric and isovaleric acid) decreased. These differences, notably the higher concentration of esters, are usually associated with a more intense fruity attribute. Triangular sensory tests revealed that the significant chemical differences were also perceivable; hence, introducing a slight pressure increase during the alcoholic fermentation could be a useful tool in managing the aroma profile of wine.

Contrasting P-T-t paths from a Paleoproterozoic metamorphic orogen: Petrology, phase equilibria, zircon and monazite geochronology of metapelites from the Jiao-Liao-Ji belt, North China Craton

The Paleoproterozoic metapelites within the major collisional orogenic belts of the North China Craton are generally characterized by clockwise metamorphic P-T-t paths. Here we report the case where an isobaric cooling followed by a final decompression is defined from high grade metapelites in the Jingshan Group at the southern part of the Jiao-Liao-Ji belt. The earlier prograde trajectory is constrained to be considerable heating with slight pressure increase to the peak metamorphism of 7.9–9.2 kbar at 763–770 °C by integrated methods of petrology, geothermobarometry and P-T-X pseudosection, suggesting an anticlockwise P-T path. Zircon and monazite geochronology combined with previous data suggests that the prograde metamorphism probably commenced at 1.90–1.85 Ga, followed by a slow isobaric cooling at mid-crustal level during 1.85–1.80 Ga and a final exhumation to upper crustal level presumable at 1.60–1.70 Ga. The defined P-T-t path seems to contrast with previously reported clockwise P-T-t paths. In the light of available geological evidence and recent numerical modelling, these contrasting P-T-t paths are reconciled by a tentative geodynamic model in which orogenic collapse and hot exhumation of the orogenic root during 1.90–1.85 Ga resulted in isothermal decompression of the granulites with clockwise P-T paths and triggered the prograde metamorphism for those regions displaying anticlockwise P-T paths. The pressure increase in the prograde trajectory of anticlockwise P-T path may be related to the sinking of upper-middle crustal materials to compensate for the contemporaneous ascend of the hot orogenic root. Subsequently, rocks of these contrasting P-T paths experienced a common slow isobaric cooling during 1.85–1.80 Ga. The 1.95–1.90 Ga metamorphic ages that are common in the Paleoproterozoic khondalitic rocks elsewhere in the NCC are absent in our samples can be ascribed to the high-temperature metamorphism related to this orogenic collapse and subsequent slow cooling. Therefore, our new data further supports that the JLJB is a long-lived collisional orogenic belt with post-orogenic extension at 1.90–1.85 Ga and subsequent slow cooling during 1.85–1.80 Ga. Hence, this study provides new metamorphic constraint on the post-orogenic evolution of the JLJB and insights into the mechanism of generating contrasting P-T-t paths in regional metamorphic orogens.

A duality of timescales: Short-lived ultrahigh temperature metamorphism preserving a long-lived monazite growth history in the Grenvillian Musgrave–Albany–Fraser Orogen

In situ LA–ICP–MS U–Pb monazite geochronology from the eastern Musgrave Inlier, central Australia, suggests that high-T, suprasolidus conditions were maintained for >70Myr during the Grenvillian (c. 1220–1140Ma). Calculated phase equilibria modelling constrain peak metamorphic conditions to ∼900°C at 6.0–6.5kbar. Collectively, the P–T–t conditions reflect that high-T, low–P metamorphism was contemporaneous with similarly thermally extreme metamorphism in the west and central Musgrave Inlier, and therefore that regionally high geothermal gradients (140–150°C/kbar) prevailed across the entire terrane. However, despite an apparently long-lived history of monazite growth, the results of this study also find evidence for arguably shorter-lived, high-T to ultrahigh temperature metamorphism. Conceivably, the preservation of high-T major element compositions and relict Y+REE growth profiles in small (<500μm) garnet grains suggest that the rocks cooled relatively rapidly to sub-diffusive temperatures. At least initially the peak to retrograde P–T path was also isobaric, or experienced a slight increase in pressure. Grenvillian-aged metamorphism in the eastern Musgrave Inlier accordingly appears to also record the effects of a transient thermal anomaly. This likely developed in response to magmatic-loading and the advection of heat from syn-metamorphic magmatic rocks of the Pitjantjatjara Supersuite, which were emplaced at mid-lower crustal depths, within a longer-lived system characterised by deep-seated, mantle-driven regional metamorphism.

Osumilite–melt interactions in ultrahigh temperature granulites: phase equilibria modelling and implications for the P–T–t evolution of the Eastern Ghats Province, India

AbstractThe exposed residual crust in the Eastern Ghats Province records ultrahigh temperature (UHT) metamorphic conditions involving extensive crustal anatexis and melt loss. However, there is disagreement about the tectonic evolution of this late Mesoproterozoic–early Neoproterozoic orogen due to conflicting petrological, structural and geochronological interpretations. One of the petrological disputes in residual high Mg–Al granulites concerns the origin of fine‐grained mineral intergrowths comprising cordierite + K‐feldspar ± quartz ± biotite ± sillimanite ± plagioclase. These intergrowths wrap around porphyroblast phases and are interpreted to have formed by the breakdown of primary osumilite in the presence of melt trapped in the equilibration volume by the melt percolation threshold. The pressure (P)–temperature (T) evolution of four samples from three localities across the central Eastern Ghats Province is constrained using phase equilibria modelling in the chemical system Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3 (NCKFMASHTO). Results of the modelling are integrated with published geochronological results for these samples to show that the central Eastern Ghats Province followed a common P–T–t history. This history is characterized by peak UHT metamorphic conditions of 945–955 °C and 7.8–8.2 kbar followed by a slight increase in pressure and close‐to‐isobaric cooling to the conditions of the elevated solidus at 940–900 °C and 8.5–8.3 kbar. In common with other localities from the Eastern Ghats Province, the early development of cordierite before osumilite and the peak to immediate post‐peak retrograde reaction between osumilite and melt to produce the intergrowth features requires that the prograde evolution was one of contemporaneous increasing pressure with increasing temperature. This counter‐clockwise (CCW) evolution is evaluated for one sample using inverse phase equilibria modelling along a schematic P–T path of 150 °C kbar−1 starting from the low P–T end of the prograde P–T path as constrained by the phase equilibria modelling. The inverse modelling is executed by step‐wise down temperature reintegration of sufficient melt into the residual bulk chemical composition at the P–T point of the 1 mol.% melt isopleth at each step, representing the melt remaining on grain boundaries after each prograde drainage event, to reach the melt connectivity transition (MCT) of 7 mol.%. The procedure is repeated until a plausible protolith composition is recovered. The result demonstrates that clastic sedimentary rocks that followed a CCW P–T evolution could have produced the observed mineral assemblages and microstructures preserved in the central Eastern Ghats Province. This study also highlights the role of melt during UHT metamorphism, particularly its importance to both chemical and physical processes along the prograde and retrograde segments of the P–T path. These processes include: (i) an increase in diffusive length scales during the late prograde to peak evolution, creating equilibration volumes larger than a standard thin section; (ii) the development of retrograde mineral assemblages, which is facilitated if some melt is retained post‐peak; (iii) the presence of melt as a weakening mechanism and the advection of heat by melt, allowing the crust to thicken; and (iv) the effect of melt loss, which makes the deep crust both denser and stronger, and reduces heat production at depth, limiting crustal thickening and facilitating the transition to close‐to‐isobaric cooling.

The Cambrian metamorphic history of Tasmania: The Metapelites

The metamorphic complexes of Tasmania formed during the Cambrian (ca 510 Ma) as a result of rapid compression in a subduction zone setting followed by rapid exhumation, which brought various fault-bounded metamorphic complexes back to the surface in less than 5 Ma. The two highest grade complexes, the Franklin Metamorphic Complex, and the Port Davey Metamorphic Complex, experienced initial growth of metamorphic garnets at ∼560°C, ∼0.56 GPa. However, their subsequent metamorphic histories diverge, with the FMC displaying a marked increase in pressure (to 1.4 GPa at peak P/T), while the PDMC shows only a slight increase in pressure (to ∼0.7 GPa). Both complexes show only a minor increase in temperature (∼100°C) between initial garnet growth and peak metamorphic conditions. Rapid exhumation of these complexes can be accounted for by a slab-breakoff model. However, the difference in peak pressure between these complexes requires either continued subduction of the FMC while the PDMC had already begun its return towards the surface or that the subduction zone geometry resulted in significantly different pressures occurring contemporaneously within portions of the channel, which are not far removed from one another.

High-pressure study of the phase transition in the itinerant ferromagnetCoS2

Electrical resistivity and magnetic susceptibility measurements of the itinerant ferromagnet ${\mathrm{CoS}}_{2}$ at high pressures reveal that its magnetic ordering temperature is tuned to zero at a critical pressure 4.8 GPa, indicating the existence of a quantum-phase transition. The ambient pressure continuous magnetic-phase transition in ${\mathrm{CoS}}_{2}$ becomes first order on a very slight pressure increase, with a tricritical point probably located almost at ambient pressure. No deviations from Fermi-liquid behavior were found in the vicinity of the quantum-phase transition in ${\mathrm{CoS}}_{2}$, implying its strong first-order nature.

Phase equilibria and metamorphic evolution of glaucophane‐bearing UHP eclogites from the Western Dabieshan Terrane, Central China

AbstractGlaucophane‐bearing ultrahigh pressure (UHP) eclogites from the western Dabieshan terrane consist of garnet, omphacite, glaucophane, kyanite, epidote, phengite, quartz/coesite and rutile with or without talc and paragonite. Some garnet porphyroblasts exhibit a core–mantle zoning profile with slight increase in pyrope content and minor or slight decrease in grossular and a mantle–rim zoning profile characterized by a pronounced increase in pyrope and rapid decrease in grossular. Omphacite is usually zoned with a core–rim decrease in j(o) [=Na/(Ca + Na)]. Glaucophane occurs as porphyroblasts in some samples and contains inclusions of garnet, omphacite and epidote. Pseudosections calculated in the NCKMnFMASHO system for five representative samples, combined with petrographic observations suggest that the UHP eclogites record four stages of metamorphism. (i) The prograde stage, on the basis of modelling of garnet zoning and inclusions in garnet, involves P–T vectors dominated by heating with a slight increase in pressure, suggesting an early slow subduction process, and P–T vectors dominated by a pronounced increase in pressure and slight heating, pointing to a late fast subduction process. The prograde metamorphism is predominated by dehydration of glaucophane and, to a lesser extent, chlorite, epidote and paragonite, releasing ∼27 wt% water that was bound in the hydrous minerals. (ii) The peak stage is represented by garnet rim compositions with maximum pyrope and minimum grossular contents, and P–T conditions of 28.2–31.8 kbar and 605–613 °C, with the modelled peak‐stage mineral assemblage mostly involving garnet + omphacite + lawsonite + talc + phengite + coesite ± glaucophane ± kyanite. (iii) The early decompression stage is characterized by dehydration of lawsonite, releasing ∼70–90 wt% water bound in the peak mineral assemblages, which results in the growth of glaucophane, j(o) decrease in omphacite and formation of epidote. And, (iv) The late retrograde stage is characterized by the mineral assemblage of hornblendic amphibole + epidote + albite/oligoclase + quartz developed in the margins or strongly foliated domains of eclogite blocks due to fluid infiltration at P–T conditions of 5–10 kbar and 500–580 °C. The proposed metamorphic stages for the UHP eclogites are consistent with the petrological observations, but considerably different from those presented in the previous studies.

Systemic lupus erythematosus associated with vasculitic syndrome (Takayasu’s arteritis)

A 43-year-old woman reported pain in the right hypochondrium, which had started 3 years before and had been worsening for the past few days. Claudication in the superior and inferior limbs, diffuse myalgia, dyspnea, precordialgia followed by dizziness and visual turbidity were added to the clinical picture. In the physical examination bilateral carotid bruit was observed, abdominal aorta murmur and the decrease of the right radial and left pedis pulses and arterial hypertension with difference in the diastolic pressure between limbs >10 mmHg was also observed. On cardiac catheterisation with aortography, right coronary with proximal parietal irregularities, slight pressure increase in right chambers and pulmonary artery, preserved left ventricle contractility, competent valves, carotid and subclavian partial obstruction, severe narrowing of the abdominal aorta below the diaphragm (80%) and right renal artery significant stenosis were observed. Takayasu's arteritis (TA) diagnosis was established according to the ACR criteria based on the clinical symptomatology, on physical and image test findings. Two years later she presented malar rash, photosensitivity, nephropathy, leukopenia, lymphopenia and hemolytic anemia confirming the systemic lupus erythematosus (SLE) diagnosis. TA coexisting with SLE has rarely been reported.

Failure Initiation and Progression in Internally-Pressurized Elliptical Composite Cylinders

The article addresses the influences of the noncircular geometry and material orthotropy on the predictions of initial material failure, and the extent and spatial distribution of subsequent failures, within the walls of internally-pressurized laminated composite cylinders with elliptical cross sections. The work is focused on the potential for leakage through the cylinder walls due to the accumulation of matrix cracking and fiber breakage within the layers. The predictions are based on numerical analyses using the finite-element code STAGS. Three different graphite-epoxy lamination sequences, a quasi-isotropic, a circumferentially stiff, and an axially stiff lamination sequence, are considered to investigate the effects of material orthotropy. Three different failure criteria and several material degradation schemes are considered to determine the sensitivity of the predictions to these steps in the analyses. It is shown that the spatial location of and pressure level to produce the initial failure, which occurs in the form of matrix cracking, is highly dependent on the lamination sequence. The pattern of failure accumulation due to increased pressure levels following initial failure is also dependent on the lamination sequence. No leakage is predicted for pressures to the level to produce first fiber failure. However, leakage is predicted for just a slight increase in pressure beyond that pressure, and the leakage pressure level and location are virtually independent of lamination sequence. The location of the first matrix failure and the spatial pattern of subsequent failures are not overly sensitive to the failure criterion used or the details of material degradation scheme employed. The pressure levels to produce the first matrix and first fiber failures are dependent on the failure criterion used.

Pan-African subduction–collision event evidenced by high- P coronas in metanorites from the Agou massif (southern Togo)

The ultrabasic–basic complexes from SE Ghana and Togo to N Bénin are generally considered as an unique lithotectonic unit which may decorate the suture zone of the Pan-African collision belt. In the southern region of Togo, the Agou massif is one of these massifs mainly consisting of granulite-facies rocks. Metagabbronorites and metagabbros outcrop in the innermost part of the Agou Igneous complex (AIC), whereas in the outermost part, relict boudins of metagabbronorites are surrounded by related retrogressed rocks such as layered Grt-bearing amphibolites and amphibolites. The latter are intruded by leucocratic to melanocratic veins, including dykes of microgabbros. Post-solidus cooling of the metagabbronorites leads to the production of HT-MP granulites (M1 granulite stage: Opx1 + Cpx1 + Pl1 + Ilm ± Sil; T > 850 °C, P = 8 kbar). Following this, an evolution toward high- P coronitic granulites is indicated by early Cpx and Grt coronite developed around Opx1 and Pl1: (granulite 2 stage: Cpx2 ± Grt2 + Pl2 + Qtz + Sil + Rt: 770 °C, 10 kbar). Three successive stages of retrogression are then observed from (i) hornblende-granulite facies (700–750 °C, 9 kbar), (ii) to amphibolite facies (700 °C, 6–7 kbar) and (iii) finally greenschist facies conditions (550–500 °C, 3–4 kbar). The inferred P– T path defines an unusual anti-clockwise loop characterized by a slight pressure increase. According to their calc-alkaline signature and their metamorphic evolution, the granulites of Agou are derived from deep-seated basic intrusion equilibrated in the lower continental crust under MP-HT conditions and never experienced an early eclogite stage. This contrasts with granulites derived from eclogites that are also described in SW Togo. In order to explain the existence of two types of metabasites in Togo, we propose that the Agou massif corresponds to basic magmas emplaced and cooled at the base of an active continental margin (western part of the Benino-Nigerian shield) whereas the former eclogites reflect subduction of the passive margin of the west African Carton. During subduction process or at the transition from subduction to collision at c. 610 Ma, burial of the edge of the active margin in the subduction zone led to the formation of coronitic granulites. During the Pan-African orogeny at c. 580 Ma the coronitic granulites together with the eclogites were exhumed under amphibolite facies conditions.

Tapping-mode atomic force microscopy in fluid of hydrated extracellular matrix.

Fragments of native, hydrated rat tail tendon were imaged by tapping-mode atomic force microscopy while immersed in fluid. The specimens were soft and sensitive to the operating parameters, and with minimal imaging pressure the collagen fibrils appeared covered by irregular blobs or by filamentous material. A slight increase in pressure caused the underlying fibril surface to appear, with an evident D-period, gap- and overlap-zones and three intraperiod ridges. Fibrils often ran parallel and in phase, implying some coupling mechanism. Longitudinal subfibrils, 8-9 nm thick, occasionally appeared. The simultaneous acquisition of the "tapping amplitude" along with the usual "height" channel clearly confirmed the presence of longitudinal subfibrils, indicative of the inner architecture of the fibril.

P–T modelling of the andalusite–kyanite–andalusite sequence and related assemblages in high‐Al graphitic pelites. Prograde and retrograde paths in a late kyanite belt in the Variscan Iberia

AbstractThe exceptional andalusite–kyanite–andalusite sequence occurs in Al‐rich graphitic slates in a narrow pelite belt on the hangingwall of a ductile normal fault in NW Variscan Iberia. Early chiastolite is replaced by Ky–Ms–Pg aggregates, which are overgrown by pleochroic andalusite near granites intruded along the fault. Slates plot in AKFM above the chloritoid‐chlorite tie‐line. Their P–T grids are modelled with Thermocalc v2.7 and the 1998 databases in the NaKFMASH and KFMASH systems. The univariant reaction Ctd + And/Ky = St + Chl + Qtz + H2O ends at progressively lower pressure as F/FM increases and A/AFM decreases, shrinking the assemblage Cld–Ky–Chl, and opening a chlorite‐free Cld–Ky trivariant field on the low temperature reaction side. This modelling matches the observed absence of chlorite in high F/FM rocks, which is restricted to low pressure in the andalusite stability field.The P–T path deduced from modelling shows a first prograde event in the andalusite field followed by retrogression into the kyanite field, most likely coupled with a slight pressure increase. The final prograde evolution into the andalusite field can be explained by two different prograde paths. Granite intrusion caused the first prograde part of the path with andalusite growth. The subsequent thermal relaxation, together with aH2O decrease, generated the retrograde andalusite–kyanite transformation, plus chlorite consumption and chloritoid growth. This transformation could have been related to folding in the beginning, and aided later by downthrowing due to normal faulting. Heat supplied by syntectonic granite intrusion explains the isobaric part of the path in the late stages of evolution, causing the prograde andalusite growth after the assemblage St–Ky–Chl. Near postectonic granites, a prograde path with pressure decrease originated the assemblage St–And–Chl.

Influence of sputter gas and sputter pressure on the structure and magnetic properties of Co–Pt–Cr thin films (abstract)

The magnetic properties of high density recording media have been shown to be very sensitive to the film microstructure. We have investigated the influences of different sputter gases (Ar, Xe, Kr) and different sputter pressures (3 to 24 mTorr) on the microstructures and magnetic properties of CoPtCr/Cr thin films. The magnetic properties of the films (coercive field, Hc, coercive squareness, S*, and remanant moment, Mr) were determined using a vibrating sample magnetometer. The microstructures were examined by transmission electron microscopy and x-ray diffraction. For all three gases studied the microstructures and properties of the CoPtCr films were found to change with sputter pressure in similar manners. Films deposited at the lowest pressure consisted of well connected, equiaxed grains. With only a slight increase in pressure, the grains formed chains separated by small gaps. As the gas pressure increased further, the chains became better defined and the gaps between them widened. The coercive squareness and coercive field correlate with the film microstructures. S* decreased with increasing sputter gas pressure, and Hc first increased and then decreased. For all three sputter gases, Hc reached a maximum around 12 mTorr. Likewise, S* decreased quite slowly with increasing pressure up to 12 mTorr and then exhibited a sharp drop between 12 and 18 mTorr. From these results it appears that the sputter pressure, rather than the mass of the sputter gas, is most important for the microstructural development of the film. Likewise, the values of S* were found to be independent of the sputter gas. However, in spite of the similar microstructures, films deposited with Ar had higher values of Hc than films deposited with Xe or Kr, for all sputter pressures examined. The role of the sputter gas mass will be discussed.

The biomechanical characteristics of the middle ear system measured by a new method. II: Clinical application and normal material.

An instrument for measuring the pressure-volume relationship of the middle ear system was introduced earlier. This paper describes the practical application of the instrument and presents a normal material of 45 healthy young adults. Reflecting a slight increase in pressure in the ear canal during the measuring procedure, a series of curves is obtained, each representing a different position of the tympanic membrane. From these curves the zero curve is defined, representing the zero position of the drum. This curve is used to determine the variables of the pressure-volume relationship of the middle ear system: hysteresis, pressure range, Pec0, and compliance. The variables express objective and dynamic measures of the mechanical properties of the middle ear. The method had an acceptable repeatability and was found to be consistent with earlier investigations. It is easy to perform and causes the subject no discomfort. It is therefore considered useful for further investigation of middle ear physiology and pathophysiology.

The venomotor response to static muscular exercise.

The venous blood pressure response to static muscular exercise was studied in seven young normal subjects by the occluded-limb technique. A slight pressure increase was obtained during the first seconds of the contraction period. Then the pressure response subsided, and the control level was reached after 1/2-1 1/2 min despite sustained contraction. The response was of the same type as that elicited by a voluntary deep breath, but usually of lesser magnitude. It seems to differ from the response to dynamic muscular exercise, suggesting that a continuous stiffening of the capacitance vessels, to maintain a high venous response, is not needed to the same extent during static muscular exercise. In previous studies a similar pressure increase has been obtained during short-lasting static muscular exercise. The present study shows that this pressure increase is confined to the initial part of the contraction period. Observations made after administration of phenoxybenzamine and atropine indicate that the venomotor response is mediated through sympathetic adrenergic nerves.