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Maximum Pressure (maximum + pressure)
Selected AbstractsHigh-Si phengite, mineral chemistry and P,T evolution of ultra-high-pressure eclogites and calc-silicates from the Dabie Shan, eastern ChinaGEOLOGICAL JOURNAL, Issue 3-4 2000Robert Schmid Abstract A suite of coesite,eclogites and associated calc-silicate rocks from the ultra-high-pressure (UHP) belt in the Dabie Shan (eastern China) was investigated petrologically. Field relations and the presence of UHP minerals such as coesite, omphacite and high-Si phengite in the eclogites and the enclosing calc-silicates testify to a common metamorphic evolution for these two lithologies. Except for one sample, all bear phengite with unusually high silica contents (Si up to 3.7 per formula unit). Phengite occupies various textural positions indicating that different metamorphic stages are reflected by these white micas, which correlate with distinct mineral zonation patterns. Using the latest thermobarometric calibrations for eclogite-facies rocks, maximum pressure,temperature (P,T) conditions of 40,48 kbar at <,750°C were estimated for the peak-metamorphic mineral assemblages. These P,T conditions were calculated for both eclogitic garnet porphyroblasts with diffusion-controlled zoning as well as garnet porphyroblasts with prograde growth zonation patterns. Most samples were affected by a strong retrograde overprint mainly under eclogite- and amphibolite-facies conditions. Thermobarometry using mineral sets from different textural positions reveals cooling and decompression of the UHP rocks down to <,20 kbar at <,600°C for the bulk of the samples. Decompression and heating indicated by a few samples is interpreted to result from mineral chemical disequilibrium or late thermal influence. These new data show that subduction of continental crust in the Dabie Shan was deeper than previously thought, and also that some cooling and decompression took place at upper-mantle depths. Copyright © 2000 John Wiley & Sons, Ltd. [source] Simulation of high velocity concrete fragmentation using SPH/MLSPHINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2003T. Rabczuk Abstract The simulation of concrete fragmentation under explosive loading by a meshfree Lagrangian method, the smooth particle hydrodynamics method (SPH) is described. Two improvements regarding the completeness of the SPH-method are examined, first a normalization developed by Johnson and Beissel (NSPH) and second a moving least square (MLS) approach as modified by Scheffer (MLSPH). The SPH-Code is implemented in FORTRAN 90 and parallelized with MPI. A macroscopic constitutive law with isotropic damage for fracture and fragmentation for concrete is implemented in the SPH-Code. It is shown that the SPH-method is able to simulate the fracture and fragmentation of concrete slabs under contact detonation. The numerical results from the different SPH-methods are compared with the data from tests. The good agreement between calculation and experiment suggests that the SPH-program can predict the correct maximum pressure as well as the damage of the concrete slabs. Finally the fragment distributions of the tests and the numerical calculations are compared. Copyright © 2003 John Wiley & Sons, Ltd. [source] The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North PoleINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2003Richard I. Cullather Abstract A comparison of National Centers for Environmental Prediction,National Center for Atmospheric Research reanalysis six-hourly sea-level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950,91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin,Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence of the semiannual variation over time is highly variable. Dynamically, this progression of the annual cycle may be attributed to the transfer of atmospheric mass from Eurasia and into the Canadian Archipelago in spring and the reverse condition in autumn. Over the central Arctic Basin, springtime pressure increases result from an enhanced poleward mass transport from Eurasia. An increase of equatorward transport over the Canadian Archipelago in May and June results in central Arctic pressure decreases into summer. A less distinct temporal separation between the poleward Canadian transport and the equatorward Eurasian transport results in the weaker second pressure maximum in autumn. On interannual time-scales, atmospheric mass over the central Arctic is exchanged with the storm track centres of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea-level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific. Copyright © 2003 Royal Meteorological Society [source] Analysis of an unconventional cycle as a new comparison standard for practical heat engines: the circular/elliptical cycle in T,S diagramINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2004Bahri Sahin Abstract An unconventional cycle analysis in the T,S diagram has been carried out and the cycle characteristics such as thermal efficiency, work density (defined as the ratio of the network output to the maximum volume in the cycle), maximum volume and maximum pressure are determined. The obtained results for the unconventional cycle are compared with those of the Carnot cycle. It is proposed that the analysed unconventional cycle may be used as a better comparison standard than the Carnot cycle for practical heat engines when both size and thermal efficiency are considered. Copyright © 2004 John Wiley & Sons, Ltd. [source] A preliminary study on bladder-assisted rotomolding of thermoplastic polymer compositesADVANCES IN POLYMER TECHNOLOGY, Issue 1 2007A. Salomi Abstract In this preliminary work, a new process is examined for manufacturing hollow parts from continuous fiber-reinforced thermoplastic polymer. The new process combines the basic idea of bag forming (or bladder-assisted forming) with the rotation of the mold for the processing of thermoplastic matrix composites. A pressurized membrane is used to compact the composite on the inner wall of a mold, which is placed inside a forced convection oven. The mold is removed from the oven for the cooling stage. The process was initially developed by using a thermoplastic pre-preg obtained using yarns of commingled E-glass fibers with isotactic polypropylene (iPP). A preliminary characterization of the thermoplastic composite showed that the material can be consolidated with pressures as low as 0.01 MPa, which is readily achievable with the process of this study. The design of the mold and membrane was carried out on the basis of both structural analysis of the aluminum shell and thermal analysis of the mold. The mold thickness is of great importance with respect to both the maximum pressure allowed in the process and the overall cycle time. Molding was performed on stacks of three and six layers of yarn, varying the applied pressure between 0.01 and 0.05 MPa and maximum temperature of the internal air between 185°C and 215°C. The composite shells obtained under different processing conditions were characterized in terms of physical and mechanical properties. Mechanical properties comparable with those obtained by compression molding and vacuum bagging were obtained. The maximum values obtained are 12.1 GPa and 290 MPa for the flexural modulus and the flexural strength, respectively. Furthermore, the results obtained show that mechanical properties improve with increasing the pressure during the cycle and with the maximum temperature used in the process. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:21,32, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20085 [source] The formation of eclogite facies metatroctolites and a general petrogenetic grid in Na2O,CaO,FeO,MgO,Al2O3,SiO2,H2O (NCFMASH)JOURNAL OF METAMORPHIC GEOLOGY, Issue 9 2002G. Rebay Abstract Eclogite facies metatroctolites from a variety of Western Alps localities (Voltri, Monviso, Lanzo, Allalin, Zermat,Saas, etc.) that preserve textural evidence of their original form as bimineralic olivine-plagioclase rocks are considered in terms of calculated mineral equilibria in the system Na2O-CaO-FeO-MgO-Al2O3 -SiO2 -H2O (NCFMASH). Pseudosections, based on a new petrogenetic grid for NCFMASH presented here, are used to unravel the metamorphic history of the metatroctolites, considering the rocks to consist of different composition microdomains corresponding to the original olivine and plagioclase grains. On the basis that the preservation of the mineral assemblage in each microdomain will tend to be from where on a rock's P,T path the metamorphic fluid phase is used up via rehydration reactions, P,T pseudosections contoured for water content, and P,T path-MH2O (amount of water) pseudosections, are used to examine fluid behaviour in each microdomain. We show that the different microdomains are likely to preserve their mineral assemblages from different places on the P,T path. For the olivine microdomain, the diagnostic mineral assemblage is chloritoid + talc (+ garnet + omphacite). The preservation of this assemblage, in the light of the closed system P,T path-MH2O relationships, implies that the microdomain loses its metamorphic fluid as it starts to decompress, and, in the absence of subsequent hydration, the high pressure mineral assemblage is then preserved. In the plagioclase microdomain, the diagnostic assemblage is epidote (or zoisite) + kyanite + quartz suggesting a lower pressure (of about 2 GPa) than for the olivine microdomain. In the light of P,T path-MH2O relationships, development of this assemblage implies breakdown of lawsonite across the lawsonite breakdown reaction, regardless of the maximum pressure reached. It is likely that the plagioclase microdomain was mainly fluid-absent prior to lawsonite breakdown, only becoming fluid-present across the reaction, then immediately becoming fluid-absent again. [source] Geochemical constraints of the eclogite and granulite facies metamorphism as recognized in the Raobazhai complex from North Dabie Shan, ChinaJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2001Y. L. Xiao Abstract A combined study of major and trace elements, fluid inclusions and oxygen isotopes has been carried out on garnet pyroxenite from the Raobazhai complex in the North Dabie Terrane (NDT). Well-preserved compositional zoning with Na decreasing and Ca and Mg increasing from the core to rim of pyroxene in the garnet pyroxenite indicates eclogite facies metamorphism at the peak metamorphic stage and subsequent granulite facies metamorphism during uplift. A P,T path with substantial heating (from c. 750 to 900 °C) after the maximum pressure reveals a different uplift history compared with most other eclogites in the South Dabie Terrane (SDT). Fluid inclusion data can be correlated with the metamorphic grade: the fluid regime during the peak metamorphism (eclogite facies) was dominated by N2 -bearing NaCl-rich solutions, whereas it changed into CO2 -dominated fluids during the granulite facies retrograde metamorphism. At a late retrograde metamorphic stage, probably after amphibolite facies metamorphism, some external low-salinity fluids were involved. In situ UV-laser oxygen isotope analysis was undertaken on a 7 mm garnet, and impure pyroxene, amphibole and plagioclase. The nearly homogeneous oxygen isotopic composition (,18OVSMOW = c. 6.7,) in the garnet porphyroblast indicates closed fluid system conditions during garnet growth. However, isotopic fractionations between retrograde phases (amphibole and plagioclase) and garnet show an oxygen isotopic disequilibrium, indicating retrograde fluid,rock interactions. Unusual MORB-like rare earth element (REE) patterns for whole rock of the garnet pyroxenite contrast with most ultra-high-pressure (UHP) eclogites in the Dabie-Sulu area. However, the age-corrected initial ,Nd(t) is ,,2.9, which indicates that the protolith of the garnet pyroxenite was derived from an enriched mantle rather than from a MORB source. Combined with the present data of oxygen isotopic compositions and the characteristic N2 content in the fluid inclusions, we suggest that the protolith of the garnet pyroxenite from Raobazhai formed in an enriched mantle fragment, which has been exposed to the surface prior to the Triassic metamorphism. [source] One-dimensional thermal modelling of Acadian metamorphism in southern Vermont, USAJOURNAL OF METAMORPHIC GEOLOGY, Issue 6 2000T. R. Armstrong One-dimensional thermal (1DT) modelling of an Acadian (Devonian) tectonothermal regime in southern Vermont, USA, used measured metamorphic pressures and temperatures and estimated metamorphic cooling ages based on published thermobarometric and geochronological studies to constrain thermal and tectonic input parameters. The area modelled lies within the Vermont Sequence of the Acadian orogen and includes: (i) a western domain containing garnet-grade pre-Silurian metasedimentary and metavolcanic rocks from the eastern flank of an Acadian composite dome structure (Rayponda,Sadawga Dome); and (ii) an eastern domain containing similar, but staurolite- or kyanite-grade, rocks from the western flank of a second dome structure (Athens Dome), approximately 10 km farther east. Using reasonable input parameters based on regional geological, petrological and geochronological constraints, the thermal modelling produced plausible P,T paths, and temperature,time (T ,t) and pressure,time (P,t) curves. Information extracted from P,T ,t modelling includes values of maximum temperature and pressure on the P,T paths, pressure at maximum temperature, predicted Ar closure ages for hornblende, muscovite and K-feldspar, and integrated exhumation and cooling rates for segments of the cooling history. The results from thermal modelling are consistent with independently obtained pressure, temperature and Ar cooling age data on regional metamorphism in southern Vermont. Modelling results provide some important bounding limits on the physical conditions during regional metamorphism, and indicate that the pressure contemporaneous with the attainment of peak temperature was probably as much as 2.5 kbar lower than the actual maximum pressure experienced by rocks along various particle paths. In addition, differences in peak metamorphic grade (garnet-grade versus staurolite-grade or kyanite-grade) and peak temperature for rocks initially loaded to similar crustal depths, differences in calculated exhumation rates, and differences in 40Ar/39Ar closure ages are likely to have been consequences of variations in the duration of isobaric heating (or ,crustal residence periods') and tectonic unroofing rates. Modelling results are consistent with a regional structural model that suggests west to east younging of specific Acadian deformational events, and therefore diachroneity of attainment of peak metamorphic conditions and subsequent 40Ar/39Ar closure during cooling. Modelling is consistent with the proposition that regional variations in timing and peak conditions of metamorphism are the result of the variable depths to which rocks were loaded by an eastward-thickening thrust-nappe pile rooted to the east (New Hampshire Sequence), as well as by diachronous structural processes within the lower plate rocks of the Vermont Sequence. [source] Fast analysis in liquid chromatography using small particle size and high pressureJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2006Dao T.-T. Abstract In order to enhance chromatographic performances in terms of efficiency and rapidity, LC has recently evolved in the development of short columns packed with small particles (sub-2 ,m) working at high pressures (>400 bar). This approach has been described 30 years ago according to the fundamental chromatographic equations. However, systems and columns compatible with such high pressures have been introduced in the market in 2004 only. Advantages of small particles working at high pressure will be discussed in terms of sensitivity, efficiency, resolution, and analysis time. Potential problems encountered with high pressure in terms of frictional heating and solvent compressibility will also be discussed even if systems working at a maximum pressure of 1000 bar are not influenced by these parameters and give reliable and reproducible results. Several applications will highlight the potential and interest of this new technology. [source] High pressure structure of Tb2Ti2O7 pyrochlore at cryogenic temperaturesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007Ravhi S. Kumar Abstract The structure of Tb2Ti2O7 pyrochlore was investigated at high pressures up to 24 GPa at cryogenic temperatures down to 6.5 K using angular dispersive X-ray diffraction with synchrotron radiation at HPCAT, Advanced Photon Source. The cell parameters were obtained by performing full profile Rietveld refinements of the diffraction data. The equation of state is obtained at low temperatures by fitting the pressure-volume data to a second order Birch Murnaghan eqation and a bulk modulus value of 168(4) GPa is obtained. The results show persistance of the pyrochlore structure up to the maximum pressure studied in the experiment and further indicate that pressure induces solely magnetic ordering which do not involve crystal symmetry changes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hazard ratings for organic peroxidesPROCESS SAFETY PROGRESS, Issue 2 2008Yih-Shing Duh Abstract Nine of commercially available organic peroxides were assessed with differential scanning calorimeter (DSC) and adiabatic calorimeters. These organic peroxides are cumene hydroperoxide (CHP), di- tert -butyl peroxide (DTBP), methyl-ethyl-ketone peroxide (MEKPO), tert -butyl hydroperoxide (TBHP), benzoyl peroxide (BPO), hydrogen peroxide, lauroyl peroxide (LPO), tert -butyl peroxybenzoate (TBPBZ), and dicumyl peroxide (DCPO). Exothermic onset temperatures, self-heat temperature and pressure rates, and heats of decomposition were measured and assessed. Adiabatic runaway reaction characteristics were determined by using ARC (accelerating rate calorimeter) and VSP2 (vent sizing package). Incompatibility, tests with several potential contaminants, was made using DSC, VSP2, and microcalorimeter. An incompatibility rating was developed using onset temperature, lowering of the onset temperature, heat of decomposition, maximum self-heat rate, adiabatic temperature rise, maximum pressure of decomposition, and maximum pressure rising rate, etc. © 2008 American Institute of Chemical Engineers Process Saf Prog 2008 [source] Urodynamic evaluation of fesoterodine metabolite, doxazosin and their combination in a rat model of partial urethral obstructionBJU INTERNATIONAL, Issue 2 2010Claudius Füllhase OBJECTIVE To evaluate the urodynamic effects of fesoterodine, a new antimuscarinic agent, alone and combined with doxazosin, in a rat model of partial urethral obstruction (PUO), as 35,83% of men with bladder outlet obstruction (BOO) secondary to benign prostatic hyperplasia (BPH) have overactive bladder (OAB) syndrome, and as the combination of ,1 -adrenoceptor- and muscarinic-receptor antagonists has been proposed to be beneficial for these patients. MATERIALS AND METHODS Thirty-seven male Sprague-Dawley rats (250 g) had surgically induced PUO; 2 weeks later they were evaluated by cystometry with no anaesthesia or any restraint. After a 1-h period either 5-hydroxymethyl tolterodine (5-HMT, the active metabolite of fesoterodine, previously known as SPM 7605), doxazosin or a combination of both, was given intravenously (0.1 mg/kg body weight), and cystometry was continued for another 45 min. Fifteen healthy, age-matched rats served as a control. RESULTS At 2 weeks after surgery the obstructed rats had an greater bladder weight, threshold pressure (TP) and micturition frequency (MF), and lower bladder capacity (BCap) and micturition volume (MV) than the controls. 5-HMT did not cause urinary retention in obstructed rats, but decreased TP, maximum pressure (MP), spontaneous bladder activity (SA) and, paradoxically, increased MF. Doxazosin alone decreased TP, MP, MF and increased BCap and MV. 5-HMT and doxazosin together did not depress the ability to empty the bladder, and showed decreased TP, MP and SA. CONCLUSIONS 5-HMT, alone and in combination, did not impair the voiding ability in obstructed rats. Doxazosin counteracted some of the ,negative' effects of 5-HMT in this model (increase of MF) and did not attenuate the ,positive' effects (decrease of bladder SA). In this model, the combination of 5-HMT and doxazosin appeared to be urodynamically safe and well tolerated. [source] 78 Use of a rabbit model to investigate the feasibility of using an innervated neosphincter transplant for the treatment of stress urinary incontinence.BJU INTERNATIONAL, Issue 2006A.D. SHAFTON Aim:, To examine the feasibility of using an innervated smooth muscle wrap as a neosphincter in a rabbit model of urinary incontinence. Methods:, Rabbits were rendered incontinent surgically by lesion of the proximal urethral wall to the level of the submucosa (n = 20). In twelve animals a strip of dartos smooth muscle was wrapped around the lesioned urethra to create a new urethral sphincter and stimulating electrodes were inserted into the muscle. After a recovery period of at least one-week cystometrograms were established for control (urethra intact), lesioned and lesion plus neosphincter animals. Results:, Infusion of saline into the bladder of control animals caused a slow rise in bladder pressure until, at approximately 20,30 ml, there was an increase in pressure that rose steeply and was associated with bladder emptying. The threshold for this reflex emptying was 2,3 cm H2O, and the maximum pressure during the reflex was 6,15 cm H2O. After the bladder emptied, the pressure dropped to 0,2 cm H2O. In rabbits with lesioned sphincters, it was not possible to obtain a normal cystometrogram because there was leakage of fluid from the urethral opening before a volume and pressure sufficient to elicit a reflex was achieved. The loss of the majority of fluid often occurred without a significant pressure increase, that is, there was no true emptying reflex. Similar results were observed in animals in which the urethra had been lesioned and implanted with the smooth muscle neosphincter. Prior to electrical stimulation of the neosphincter, with constant current pulses at 2 Hz, substantial leak occurred at 11.4 ± 2.5 ml, whereas during stimulation voiding occurred at 17.8 ± 1.4 ml. At void or emptying, the peak pressure was 6.1 ± 0.1 cm H20 in control, 0.7 ± 0.2 in operated but not stimulated and 3.5 ± 0.6 in the same animals during stimulation. A satisfactory improvement of continence was observed for a period of up to 6½ months postsurgery. At the end of the study, histological examination confirmed the neosphincter to be both healthy and viable. Conclusion:, Smooth muscles of the dartos display contractile properties which make them suitable for use as transplantable sphincters. A smooth muscle neosphincter, controlled by electrical stimulation, can restore continence after urethral damage. [source] The relationship between birth weight and feeding maturation in preterm infantsACTA PAEDIATRICA, Issue 2 2009Brian H Wrotniak Abstract Aim: To report changes in ingestive behaviour from 35 to 40 weeks post-conceptual age and examine the association between birth weight and feeding maturation in preterm infants. Methods: One hundred and four preterm infants born 24 to 34 weeks gestational age were studied. Feeding maturation was assessed as the change from 35 to 40 weeks post-conceptual age in the number of sucks over 5 min, sucking bursts, sucks per burst, time between bursts and maximum pressure during a suck (Pmax). The association between birth weight and each sucking behaviour was examined after adjusting for potential confounders. Results: Significant changes in feeding maturation occurred between 35 and 40 weeks. Birth weight was positively associated with change in Pmax and change in number of sucks per burst for extremely premature infants born 24 to <29 weeks gestational age but not for very premature infants born ,29 to 34 weeks. The association between birth weight and change in Pmax for extremely premature infants remained significant after adjustment (adjusted beta = 0.128 mmHg increase in change in maximum sucking pressure per every 1 g of birth weight, 95% CI = 0.017, 0.239, p = 0.03). Conclusion: Birth weight is positively associated with maturation in maximum sucking pressure among infants born extremely premature. [source] Pressures generated in vitro during Stabident intraosseous injectionsINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2005J. M. Whitworth Abstract Aim, To test the hypothesis that the Stabident intraosseous injection is a potentially high-pressure technique, which carries serious risks of anaesthetic cartridge failure. Methodology, A standard Astra dental syringe was modified to measure the internal pressure of local anaesthetic cartridges during injection. Intra-cartridge pressures were measured at 1 s intervals during slow (approximately 15 s) and rapid (<10 s) injections of 2% Xylocaine with 1 : 80 000 adrenaline (0.25 cartridge volumes) into air (no tissue resistance), or into freshly prepared Stabident perforation sites in the anterior mandible of freshly culled young and old sheep (against tissue resistance). Each injection was repeated 10 times over 3 days. Absolute maximum pressures generated by each category of injection, mean pressures at 1 s intervals in each series of injections, and standard deviations were calculated. Curves of mean maximum intra-cartridge pressure development with time were plotted for slow and rapid injections, and one-way anova (P < 0.05) conducted to determine significant differences between categories of injection. Results, Pressures created when injecting into air were less than those needed to inject into tissue (P < 0.001). Fast injection produced greater intra-cartridge pressures than slow delivery (P < 0.05). Injection pressures rose more quickly and to higher levels in small, young sheep mandibles than in larger, old sheep mandibles. The absolute maximum intra-cartridge pressure developed during the study was 3.31 MPa which is less than that needed to fracture glass cartridges. Conclusions, Stabident intraosseous injection conducted in accordance with the manufacturer's instructions does not present a serious risk of dangerous pressure build-up in local anaesthetic cartridges. [source] Cold subduction and the formation of lawsonite eclogite , constraints from prograde evolution of eclogitized pillow lava from CorsicaJOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2010E. J. K. RAVNA Abstract A new discovery of lawsonite eclogite is presented from the Lancône glaucophanites within the Schistes Lustrés nappe at Défilé du Lancône in Alpine Corsica. The fine-grained eclogitized pillow lava and inter-pillow matrix are extremely fresh, showing very little evidence of retrograde alteration. Peak assemblages in both the massive pillows and weakly foliated inter-pillow matrix consist of zoned idiomorphic Mg-poor (<0.8 wt% MgO) garnet + omphacite + lawsonite + chlorite + titanite. A local overprint by the lower grade assemblage glaucophane + albite with partial resorption of omphacite and garnet is locally observed. Garnet porphyroblasts in the massive pillows are Mn rich, and show a regular prograde growth-type zoning with a Mn-rich core. In the inter-pillow matrix garnet is less manganiferous, and shows a mutual variation in Ca and Fe with Fe enrichment toward the rim. Some garnet from this rock type shows complex zoning patterns indicating a coalescence of several smaller crystallites. Matrix omphacite in both rock types is zoned with a rimward increase in XJd, locally with cores of relict augite. Numerous inclusions of clinopyroxene, lawsonite, chlorite and titanite are encapsulated within garnet in both rock types, and albite, quartz and hornblende are also found included in garnet from the inter-pillow matrix. Inclusions of clinopyroxene commonly have augitic cores and omphacitic rims. The inter-pillow matrix contains cross-cutting omphacite-rich veinlets with zoned omphacite, Si-rich phengite (Si = 3.54 apfu), ferroglaucophane, actinolite and hematite. These veinlets are seen fracturing idiomorphic garnet, apparently without any secondary effects. Pseudosections of matrix compositions for the massive pillows, the inter-pillow matrix and the cross-cutting veinlets indicate similar P,T conditions with maximum pressures of 1.9,2.6 GPa at temperatures of 335,420 °C. The inclusion suite found in garnet from the inter-pillow matrix apparently formed at pressures below 0.6,0.7 GPa. Retrogression during initial decompression of the studied rocks is only very local. Late veinlets of albite + glaucophane, without breakdown of lawsonite, indicate that the rocks remained in a cold environment during exhumation, resulting in a hairpin-shaped P,T path. [source] The determination of membrane transport parameters with the cell pressure probe: theory suggests that unstirred layers have significant impactPLANT CELL & ENVIRONMENT, Issue 12 2005MELVIN T. TYREE ABSTRACT A simulation model was written to compute the time-kinetics of turgor pressure, P, change in Chara corallina during cell pressure probe experiments. The model allowed for the contribution of a membrane plus zero, one, or two unstirred layers of any desired thickness. The hypothesis that a cell with an unstirred layer is a composite membrane that will follow the same kind of kinetics with or without unstirred layers was tested. Typical ,osmotic pulse' experiments yield biphasic curves with minimum or maximum pressures, Pmin(max), at time tmin(max) and a solute exponential decay with halftime . These observed data were then used to compute composite membrane properties, namely the parameters Lp = the hydraulic conductance, , = reflection coefficient and Ps = solute permeability using theoretical equations. Using the simulation model, it was possible to fit an experimental data set to the same values of Pmin(max), tmin(max) and incorporating different, likely values of unstirred layer thickness, where each thickness requires a unique set of plasmalemma membrane values of Lp, , and Ps. We conclude that it is not possible to compute plasmalemma membrane properties from cell pressure probe experiments without independent knowledge of the unstirred layer thickness. [source] | |||||||||||||||||||