Changes In Hydrostatic Pressure Research Articles

Influence of Early Hydration Process on the Hydrostatic Pressure Change of Cement Pastes at Different Temperatures.

In cementing operations, a rapid decrease in the hydrostatic pressure of cement paste is one of the main causes of early gas channeling. In response to this issue, tests were conducted on the variation in the hydrostatic pressure of cement paste over time at different temperatures (30 °C-180 °C), and it was found that the curve of its rapid decrease time point with temperature change conforms to the Boltzmann function. The relationship between the early hydration process and the microstructure of paste at 90 and 150 °C, as well as the changes in hydrostatic pressure, was studied using X-ray powder diffraction, thermogravimetry, and scanning electron microscopy. The results show that the hydrostatic pressure curve of the paste shows a trend of first stabilization and then rapidly decreasing at medium and low temperatures (30 and 90 °C). At high temperatures (150 °C), the pressure curve initially increases until stabilization, enters a stable period, and finally rapidly decreases. In the early stage of hydration induction, there is a large amount of free water between hydration products, and the hydrostatic pressure of the paste remains stable. In the process of hydrostatic pressure reduction, the microstructure of the paste develops from the particle hydration products to a "gel framework", which isolates the pressure transfer of part of the free water. During the acceleration period of hydration, the hydration products enhance the "framework" and reduce the porosity of the paste, completely cutting off the transmission of water pressure, resulting in a rapid decrease in the hydrostatic pressure of the paste. A method for predicting the rapid decrease in hydrostatic pressure of the paste was proposed using the hydration reaction process.

Coupling analysis of multi-annular temperature and pressure gradients in oil and gas wells considering fluid thermodynamic properties

A coupled prediction model for temperature and pressure is developed for the annulus of multiple casings to prevent damaging the integrity of oil and gas wells due to annular pressures. The complex structure of the oil and gas well requires dividing the calculation of the annular pressure into three stages based on the annulus level. The annular temperature and pressure gradients of the wellbore are then studied. The hydrostatic pressure changes of the annular fluid at different temperatures, pressures, and well depths are analyzed considering the influence of the isobaric expansion coefficient and isothermal compression coefficient in annular fluids. The pressure gradients of annular fluids A, B, and C with production time and well depth are discussed along with the deformation of production casings. Results show that the annular fluid density and hydrostatic pressure decrease with the increase of temperature, while they will increase with the increase of annular pressure. The annular pressure increases first and then decreases from the bottom of the well to the wellhead. The annular pressure increases the fastest in the early production stages.

Determining Which Hydrostatic Pressure Regimes Promote Osteogenesis in Human Mesenchymal Stem Cells.

Compressive loading of bone causes hydrostatic pressure changes which have been proposed as an osteogenic differentiation stimulus for mesenchymal stem cells (hMSCs). We hypothesised that hMSCs are adapted to differentiate only in response to cyclic hydrostatic pressures above critical thresholds of magnitude and frequency which correspond to physiological levels of anabolic bone loading. Using a pneumatic-hydrostatic bioreactor, we applied hydrostatic pressure regimes to human hMSCs in 3D collagen hydrogel cultures for 1h/day over 28days to determine which levels of pressure and frequency stimulated osteogenesis in vitro. Stimulation of the 3D cultures with 0-280kPa cyclic hydrostatic pressure at 1Hz resulted in up to 75% mineralisation in the hydrogel (without exogenous growth factors), whilst static culture or variations of the regime with either constant high pressure (280kPa, 0Hz), low-frequency (0.05Hz, 280kPa) or low-magnitude (70kPa, 1Hz) stimulation had no osteogenic effects (< 2% mineralisation). Nuclear translocation of YAP was observed following cyclic hydrostatic pressure in mature MLO-A5 osteoblasts but not in hMSCs, suggesting that cyclic hydrostatic pressure activates different mechanotransduction pathways in undifferentiated stem cells and committed osteoblasts. Hydrostatic pressure is a potent stimulus for differentiating MSC into highly active osteoblasts and may therefore be a versatile tool for translational cell engineering. We have demonstrated that there are minimum levels of force and frequency needed to trigger osteogenesis, i.e. a pressure 'switch', which corresponds to the physiological forces experienced by cells in their native mesenchymal niche. The mechanotransduction mechanisms underpinning these effects are the subject of further study.

Quality changes in high hydrostatic pressure treated enriched tomato sauce.

Use of high hydrostatic pressure (HHP) with reduced processing times is gaining traction in the food industry as an alternative to conventional thermal treatment. In order to enhance functional benefits while minimizing processing losses, functionalized products are being developed with such novel techniques. In this study, changes in quality parameters for HHP treated enriched tomato sauce were evaluated, with the aim to assess its viability as an alternative to conventional thermal treatment methods. HHP treatments at 500 MPa, 30 °C/50 °C significantly increased the total phenolic and lycopene content of the sauce samples, achieving 6.7% and 7.5% improvements over conventionally treated samples. The antioxidant capacity of the HHP-treated samples was also found to match or be better than conventionally treated samples. Furthermore, a T2 relaxation time study revealed that pressure-temperature processing treatments were effective in maintaining the structural integrity of water molecules. Microbiological analyses revealed that 500 MPa/50 °C 5 min treatment can offer 8 logs reduction colony formation, matching the results of conventional thermal treatment. Combined pressure-temperature treatments improve results, reduce time consumption. 500 MPa/50 °C treatments provided retention of quality parameters and significant reduction in microbial activity. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Variations in fluid chemical potential induce fibroblast mechano-response in 3D hydrogels

Mechanical deformation of skin creates variations in fluid chemical potential, leading to local changes in hydrostatic and osmotic pressure, whose effects on mechanobiology remain poorly understood. To study these effects, we investigate the specific influences of hydrostatic and osmotic pressure on primary human dermal fibroblasts in three-dimensional hydrogel culture models. Cyclic hydrostatic pressure and hyperosmotic stress enhanced the percentage of cells expressing the proliferation marker Ki67 in both collagen and PEG-based hydrogels. Osmotic pressure also activated the p38 MAPK stress response pathway and increased the expression of the osmoresponsive genes PRSS35 and NFAT5. When cells were cultured in two-dimension (2D), no change in proliferation was observed with either hydrostatic or osmotic pressure. Furthermore, basal, and osmotic pressure-induced expression of osmoresponsive genes differed in 2D culture versus 3D hydrogels, highlighting the role of dimensionality in skin cell mechanotransduction and stressing the importance of 3D tissue-like models that better replicate in vivo conditions. Overall, these results indicate that fluid chemical potential changes affect dermal fibroblast mechanobiology, which has implications for skin function and for tissue regeneration strategies.

New insight into groundwater 4He ages based on Ne isotopic equilibrium in Jianghan Plain, Central China

The change of hydrostatic pressure caused by the fluctuation of groundwater table in the aquifer will lead to the partial dissolution of excess 4He gas, resulting in the isotope imbalance of 3He/4He-4He. The dissolved Ne in groundwater is mainly derived from the atmosphere, and its isotopic composition can correct the isotopic imbalance of 3He/4He-4He. We collected thirty-eight groundwater samples from the second aquifer of the Jianghan Plain, and the isotopic concentrations and ratios of He and Ne were measured. 21Ne/22Ne-20Ne/22Ne illustration is proposed to estimate the shares of atmospheric and mantle components. The 21Ne content and isotopic ratios of atmospheric and mantle components are used to estimate a calculated Ne content. The difference between the calculated Ne content and the measured Ne content (∆Ne) is used to evaluate the percentage of error estimated“excess air”. The accumulation of crustal 4He is corrected with the measured 4He content and the percentage of error estimated “excess air”. We found the maximum percentage of error estimated “excess air” was 7.57 % occurring in the groundwater samples from the second aquifer of Jianghan Plain, and the disequilibrium of 3He/4He-4He led to overestimation of the share of mantle He. The percentage of mantle He in total dissolved components is reassessed and range from 0.03 % to 0.74 %, indicating the mantle component is minor. The reassessed 4He ages (1.79 ka to 21.90 ka) were uniformly older than those estimated by traditional method which only use the measured 3He/4He ratio to distinguish the crust 4He (1.28 ka to 18.74 ka). 4He age is significantly underestimated up to 47.05 %.

Elevated hydrostatic pressure enhances the potential for microbially mediated carbon sequestration at the sediment–water interface in a deep-water reservoir by modulating functional genes and metabolic pathways

Microbially mediated carbon cycling is essential for the production of refractory dissolved organic carbon and subsequent formation of stable carbon sinks at the sediment–water interface (SWI) in aquatic ecosystems, such as lakes. It remains unclear how this process is influenced by hydrostatic pressure changes due to water level fluctuation in deep-water reservoirs. Here, a microcosm simulation experiment was carried out to decipher the response of microbially mediated carbon cycling to various hydrostatic pressures (i.e., 0.1 MPa [atmospheric pressure], 0.2 MPa, 0.5 MPa, 0.7 MPa) at the SWI in Jinpen Reservoir, Shaanxi Province, China. The response mechanisms of microbial community structure, functional gene abundance, and metabolic pathway activity associated with carbon cycling were explored by metagenomics and metabolomics. Results showed that the number of microbial species in sediment samples increased with elevating pressure. The relative abundance of archaea also increased from 0.2% to 0.4% as a consequence of pressure elevation, accompanied by 0.17% and 0.03% decrease in bacteria and fungi, respectively. In contrast with low pressures, high pressures allowed the microbial communities to form a more closely connected network, which maintained more complex interspecies interactions and greater system stability. High pressures additionally improved the abundances of specific functional genes (e.g., ALDO, ACO, sdhA, and sdhC) in carbon metabolic pathways, promoted carbon fixation by the reductive pentose phosphate (Calvin) and citrate cycles, and hindered methanogenesis. Piezophilic taxa (e.g., Gammaproteobacteria, Alphaproteobacteria, Bacteroidetes) and genes (e.g., ompH, asd) were identified among carbon cycling-associated microbial communities. The piezophilic genes, which were mainly present in the Proteobacteria phylum, increased first and then decreased in abundance with elevating pressure. The findings indicate that elevated hydrostatic pressure contributes to carbon sequestration at the SWI in deep-water reservoirs by changing carbon cycling-associated microbial species, as well as relevant functional genes and metabolic pathways.Graphical

Thermal recovery test for determining the thermal conductivity of the soil

This paper presents a new in-situ experimental procedure for determining a thermal conductivity of soil, as one of the thermophysical properties necessary for dimensioning vertical buried heat exchangers of geothermal heat pumps. The proposed method, called the thermal recovery test, is based on the assumption that there is a direct analogy between the hydrodynamic process of filling (recovery) the well with water from a porous aquifer after its partial or complete discharging and the process of establishment of thermal equilibrium in an infinite medium previously disturbed by a line heat sink (source). Apart from presentation the theoretical background of these two phenomena, the display of the identical theoretical logarithmic character of the change of hydrostatic pressure and soil temperature, description of the experimental procedure, the experimental results of three performed experiments are also presented. Additionally, results for the experimentally obtained values of the thermal conductivity of the soil are compared with those obtained from the thermal response test, and the advantages and drawbacks of the new thermal recovery test method are analyzed.

Linking Biogeochemical and Hydrodynamic Processes to Model Methane Fluxes in Shallow, Tropical Floodplain Lakes

AbstractFloodplains lakes are abundant in the Amazon basin and are important methane sources to the atmosphere. Existing biogeochemical models require modifications and inclusion of hydrodynamic processes operative in shallow, warm waters to be applied to these aquatic ecosystems. We modified a 1‐dimensional process‐based, lake biogeochemical model and combined a 3‐dimensional hydrodynamic model to suit Amazon floodplains. We evaluated the combined model's performance simulating methane concentrations and fluxes and several related processes in the open lake and an embayment of a well‐studied Amazon lake. Parameters for calibration were selected through sensitivity tests using a machine learning‐based algorithm, classification, and regression trees. Comparison between simulated and measured fluxes indicate generally good agreement in seasonal patterns and magnitudes. Comparisons of near‐surface concentrations varied with no clear patterns. Simulations of methane concentrations at near‐surface and near‐bottom, and diffusive emissions are most sensitive to carbon mineralization rate, Q10 factors for methanogenesis and oxidation, and methane oxidation potential. Modeled rates of planktonic photosynthesis were generally lower than measurements, though simulated planktonic respiration was often similar to measurements. Simulated rates of methane oxidation were considerably lower, with a few exceptions, than measurements of methane oxidation in oxic water of the lake. Improvements of results of the linked hydrodynamic‐biogeochemical model will result from inclusion of advective transport, use of parameter values appropriate for tropical waters, especially for methane oxidation and photosynthesis, and addition of changes in hydrostatic pressure to model of ebullition.

Development of new colloid osmotic pressure measurement method using ultrafiltration membrane during cardiopulmonary bypass

Background: Clinical practice of measuring colloid osmotic pressure (COP) was abandoned after correcting hypoosmolarity did not improve overall patient outcomes. However, the use of albumin and colloidal solutions has contributed to maintaining intraoperative and postoperative fluid balance at lower levels. Reduced perioperative fluid balance is consistently reported to have positive effects on clinical outcomes. Priming solutions for cardiopulmonary bypass typically include colloids; however, the optimal type of priming solution has not yet been determined. Stricter COP management may further improve postoperative courses. To achieve this, the widespread adoption of a measurement method suitable for COP monitoring during cardiopulmonary bypass is required. Methods: A test circuit was made which measured COP using an ultrafiltration membrane method based on the changes in hydrostatic pressure that occurs across a semipermeable membrane. We then compared the measurements obtained using this method with colloidal osmometer measurements. Results: COP measurements were obtained for a total of 100 tests (10 times each for 10 test solutions). The evaluation parameters included simultaneous reproducibility, correlation with the colloid osmometer, and measurement time. The results demonstrated high accuracy of the ultrafiltration membrane method, simultaneous reproducibility within 3%, a high positive correlation with the colloid osmometer (correlation coefficient: R2 = 0.99; p &lt; 0.01), and equal time required for measurement. Conclusion: Measuring COP using ultrafiltration membranes solves problems within existing measurement methods. Although further improvements in the method are necessary, it has implications for future research and clinical applications.

Impact of height difference between coronary ostium and location of intracoronary pressure sensor on fractional flow reserve measurements

Abstract Background Fractional flow reserve (FFR) is the most verified index to date in invasively evaluating lesion-specific myocardial ischemia. During FFR measurements, distal coronary pressure (Pd) can be influenced by hydrostatic pressure change resulted from the height difference (HD) between coronary ostium and location of distal pressure sensor. We aimed to investigate the impact of aorto-coronary HD on FFR measurement in each coronary artery. Methods We retrospectively analyzed 257 patients who underwent FFR measurement and coronary computed tomography angiography (CCTA) within a year. HD was measured by CCTA as the vertical distance between coronary ostium and a matched point of distal coronary pressure sensor identified on coronary angiography. Results The location of Pd sensor was higher in left anterior descending artery (LAD) (-4.47±1.33cm), whereas lower in left circumflex artery (LCX) (2.54±1.05cm) and right coronary artery (RCA) (2.05±1.25cm) than the coronary ostium. Compared with the original FFR values, corrected FFR by HD was higher in LAD (0.79±0.09, 0.82±0.09, P&amp;lt;0.05) and tended to be lower in LCX and RCA (0.87±0.07, 0.85±0.08, p=0.21; 0.87±0.10, 0.86±0.10, p=0.49, respectively). Based on FFR cut-off value of 0.8, the concordance rate between the FFR and corrected FFR was 77.8%, 92.5%, and 100% in LAD, LCX, and RCA, respectively. Conclusion During FFR measurements, HD between coronary ostium and distal pressure sensor may affect interpretation of disease severity and FFR-guided treatment decision of coronary artery disease.

Abstract 18245: ViTrack™ : A Computer Vision Technology for Continuous Blood Pressure and Advanced Cardio Hemodynamics

Introduction: There is an unmet need for a wearable device for accurate and continuous non-invasive blood pressure (BP) and other cardio-hemodynamic parameters in real-world situations. Methods: To address the need, we have developed ViTrack™, a wrist wearable optomechanical sensor capable of 3D contact sensing at the microscale. ViTrack, based on a fundamentally new method, utilizes pressure-dependent spatiotemporal skin displacement to directly measure beat-to-beat SBP and DBP. ViTrack also measures heart rate and respiratory parameters, and advanced hemodynamic parameters. In real-world settings, patient activities such as body or arm movements introduce motion artifacts that interfere with BP measurement. To address this, ViTrack’s 3D imaging system has been enhanced with advanced computer vision and AI/ML techniques to ensure precise and consistent measurements, regardless of patient movement or wrist position relative to the heart (hydrostatic pressure change). Methods: We have built a minimum viable product. Animal studies (n = 12) showed that the device correlates well (R2 value = 0.958) with invasive arterial pressure (IAP). In outpatient settings, in more than 120 subjects, both male and female, with a wide range of BP (86-180 SBP; 60-110 DBP), when compared to the auscultatory method, ViTrack measures BP in accordance with FDA standards (Association for the Advancement of Medical Instrumentation [AAMI] standard: mean offset &lt; 5mmHg; standard deviation &lt;8 mmHg). Subsequently, in unconstrained patients (n=14), we compared the ViTrack continuously over 2 hours against IAP in real-life ICU conditions. The arm with ViTrack was unconstrained, while the opposite arm was constrained because of the IAP line. With the implementation of the computer vision and AI/ML algorithms, when beat-to-beat measures were averaged across 20 seconds and compared to IAP, ViTrack demonstrated excellent accuracy for both DBP (mean error = -1.37 mmHg [SD = 3.8 mmHg]) and SBP (mean error = -2.69 mmHg [SD = 5.99 mmHg]). Conclusions: Studies show that ViTrack, a wearable device, can accurately and continuously measure BP in real-world settings. The technology could disrupt the way we measure and manage BP. A multi-center trial is further validating the technology.

A snap-through instability of cell adhesion under perturbations in hydrostatic pressure

The balance between stress and adhesion governs many behaviors of adherent cells such as cell migration. In certain microenvironments such as that of a tumor, variations in hydrostatic pressure be substantial compared to cell-generated stresses. These variations can affect stress-activated ion channels whose activation can in turn affect cell volume and adhesion. To study these effects, we developed a theoretical model to relate changes in hydrostatic pressure to the morphology and volume of adherent cells. The model predicted the bistability of cell morphology (i.e., a snap-through instability) under hydrostatic pressure for certain ranges of adhesion energy density. This snap-through instability can enable cells to spontaneously detach from their environment, and may have bearing on migration and metastasis.

Monitoring pressure changes in the inner ear induced by middle ear pressure therapy with an EFET01 device in guinea pigs

Background As a low-cost, portable, handheld air pressure generation tool not requiring a ventilation tube, the EFET01 device has shown clinical effectiveness for intractable Ménière’s disease (MD) patients in Japan. However, no animal studies have investigated changes in inner ear pressure (PI) when applying this device. Objective To determine the PI properties in response to middle ear pressure therapy (MEPT) induced by the EFET01 in guinea pigs. Material and Methods In seven healthy guinea pigs, bi-phasic pressure pulses from −5 to 12 cm H2O were delivered to the external ear canal and transmitted to the middle and inner ear cavities with an intact tympanic membrane. Hydrostatic pressure change in the inner ear perilymphatic compartment was measured by a servo-controlled micropipette system. Results From eight successful ears, pressure changes in the middle ear slightly decreased and were instantly transferred to the inner ear. The EFET01 produces a bi-phasic positive/negative pressure pulse, which is approximately twice as large as the monophasic pressure pulse. Conclusion Our study clarified the EFET01’s ability to transmit pressure and verified its effectiveness in MD patients as observed in clinical studies. Significance The PI properties in guinea pig response to MEPT with the EFET01 device were investigated.

Time-domain floater stress analysis for a floating wind turbine

There are increasing focuses on developing cost-effective floating wind turbines, for which efficient stress analysis methods are needed for floater structural design. Most of the today's studies focus on global analysis methods in which the floater is assumed as a rigid body or multiple rigid bodies and the stress distributions in the floater cannot be directly obtained. As part of the COWI Fonden funded EMULF project, a summary about the methodology, the numerical modeling procedure and the verification for stress response analysis of a semi-submersible floater for a 15MW wind turbine is presented. This analysis procedure includes the regeneration of the hydrodynamic pressure loads on the external wet surface of the floater due to wave diffraction, radiation and hydrostatic pressure change, and the application of these pressure loads, together with the time-varying gravity due motions, the inertial loads and the forces/moments at the boundaries (i.e. tower bottom and mooring line fairleads) of the floater to obtain the deformation and the stresses of the floater in the time domain. The analysis procedure is implemented in a developed MATLAB code and the DNV software package. The importance of the different hydrodynamic pressure components was discussed considering representative sea states. A verification of the obtained stress time series and statistics using this method against the regeneration from a linear frequency-domain approach was made considering irregular wave actions only, and a very good agreement was obtained. The developed methodology can provide an efficient solution for structural design analysis of floating wind turbines.

Four-Point Impedance and Utricular Dysfunction Is Associated with Postoperative Dizziness after Cochlear Implantation.

Postimplantation dizziness is common, affecting approximately 50% of patients. Theories for dizziness include utricular inflammation, endolymphatic hydrops, and loss of perilymph. Four-point impedance (4PI) is a novel impedance measurement in cochlear implantation that shows potential to predict hearing loss, inflammation, and fibrotic tissue response. Here, we associate 4PI with dizziness after implantation and explore the link with utricular function. Subjective visual vertical (SVV) as a measure of utricular function was recorded preoperatively as a baseline. 4PI was measured immediately postinsertion. Ongoing follow-up was performed at 1 day, 1 week, and 1 month, postoperatively. At each follow-up, 4PI, SVV, and the patients' subjective experience of dizziness were assessed. Thirty-eight adults were recruited. One-day 4PI was significantly higher in patients dizzy within the next week (254 Ω vs 171 Ω, p = 0.015). The optimum threshold on receiver operating characteristic curve was 190 Ω, above which patients had 10 times greater odds of developing dizziness (Fisher exact test, OR = 9.95, p = 0.0092). This suggests that 4PI varies with changes in the intracochlear environment resulting in dizziness, such as inflammation or hydrops. SVV significantly deviated away from the operated ear at 1 day (fixed effect estimate = 2.6°, p ≤ 0.0001) and 1 week (fixed effect estimate 2.7°, p ≤ 0.001). One-day 4PI is a potentially useful marker for detecting postoperative dizziness after cochlear implantation. Of the current theories for postoperative dizziness, inflammation might explain the findings seen here, as would changes in hydrostatic pressure. Future research should focus on detecting and exploring these labyrinthine changes in further detail.

Noninvasive Estimation of Tumor Interstitial Fluid Pressure from Subharmonic Scattering of Ultrasound Contrast Microbubbles

The noninvasive estimation of interstitial fluid pressure (IFP) using ultrasound contrast agent (UCA) microbubbles as pressure sensors will provide tumor treatments and efficacy assessments with a promising tool. This study aimed to verify the efficacy of the optimal acoustic pressure in vitro in the prediction of tumor IFPs based on UCA microbubbles' subharmonic scattering. A customized ultrasound scanner was used to generate subharmonic signals from microbubbles' nonlinear oscillations, and the optimal acoustic pressure was determined in vitro when the subharmonic amplitude reached the most sensitive to hydrostatic pressure changes. This optimal acoustic pressure was then applied to predict IFPs in tumor-bearing mouse models, which were further compared with the reference IFPs measured using a standard tissue fluid pressure monitor. An inverse linear relationship and good correlation (r = -0.853, p < 0.001) existed between the subharmonic amplitude and tumor IFPs at the optimal acoustic pressure of 555 kPa, and pressure sensitivity was 1.019 dB/mmHg. No statistical differences were found between the pressures measured by the standard device and those estimated via the subharmonic amplitude, as confirmed by cross-validation (mean absolute errors from 2.00 to 3.09 mmHg, p > 0.05). Our findings demonstrated that in vitro optimized acoustic parameters for UCA microbubbles' subharmonic scattering can be applied for the noninvasive estimation of tumor IFPs.

10 clinical tips for advancing patient safety when using syringe pump systems for microinfusion intravenous drug therapy.

10 clinical tips for advancing patient safety when using syringe pump systems for microinfusion intravenous drug therapy.

Improving barocaloric properties by tailoring transition hysteresis in Mn3CuSnN antiperovskites

The magnetically frustrated manganese nitride antiperovskite family displays significant changes of entropy under changes in hydrostatic pressure near a first-order antiferromagnetic to paramagnetic phase transition that can be useful for the emerging field of solid-state barocaloric cooling. In previous studies, the transition hysteresis has significantly reduced the reversible barocaloric effects (BCE). Here we show that the transition hysteresis can be tailored through quaternary alloying in the Mn3CuSnN system. We find the magnitude of hysteresis is minimised when Cu and Sn are equiatomic (x = 0.5) reaching values far less than previously found for Mn3 AN ( Pd, Ni, Ga, Zn), whilst retaining entropy changes of the same order of magnitude. These results demonstrate that reversible BCE are achievable for p < 100 MPa in the Mn3(A, B)N family and suggest routes to modify the transition properties in compounds of the same family.

Effects of Hydrostatic-Pressure on Muscle Contraction: A Look Back on Some Experimental Findings.

Findings from experiments that used hydrostatic pressure changes to analyse the process of skeletal muscle contraction are re-examined. The force in resting muscle is insensitive to an increase in hydrostatic pressure from 0.1 MPa (atmospheric) to 10 MPa, as also found for force in rubber-like elastic filaments. The force in rigour muscle rises with increased pressure, as shown experimentally for normal elastic fibres (e.g., glass, collagen, keratin, etc.). In submaximal active contractions, high pressure leads to tension potentiation. The force in maximally activated muscle decreases with increased pressure: the extent of this force decrease in maximal active muscle is sensitive to the concentration of products of ATP hydrolysis (Pi-inorganic phosphate and ADP-adenosine diphosphate) in the medium. When the increased hydrostatic pressure is rapidly decreased, the force recovered to the atmospheric level in all cases. Thus, the resting muscle force remained the same: the force in the rigour muscle decreased in one phase and that in active muscle increased in two phases. The rate of rise of active force on rapid pressure release increased with the concentration of Pi in the medium, indicating that it is coupled to the Pi release step in the ATPase-driven crossbridge cycle in muscle. Pressure experiments on intact muscle illustrate possible underlying mechanisms of tension potentiation and causes of muscle fatigue.