Onset Pressure Research Articles

Microstructure evolution in high-pressure phase transformations of CrFeNi and CoCrFeMnNi alloys

The extraordinary dynamics of microstructures, such as various dislocations, stacking faults, twinning, and polymorphism transformations, dominate the mechanical performance of high-entropy alloys. To reveal the phase transformation kinetics, we precisely detect the microstructure evolution in CoCrFeMnNi high-entropy alloy (HEA) and CrFeNi medium-entropy alloy (MEA) subjected to high-pressure compression using in situ angular-dispersive synchrotron X-ray diffraction. We find that controlling the initial microstructural state using cold-rolling can significantly reduce the stacking fault energy of CoCrFeMnNi and CrFeNi alloys, which results in lower onset pressures for phase transformations. The microstructure-induced stacking-fault energy reduction facilitates the formation of twins, which can act as nucleation sites for hexagonal close-packed (HCP) phase formation and recrystallization. The microstructure evolution-driven deviatoric deformation mechanism of CoCrFeMnNi HEA and CrFeNi MEA under quasi-hydrostatic compression is explored. Beyond the FCC phase, twinning in the HCP phase of CoCrFeMnNi alloy under high pressure is observed for the first time. This implies that the deformation mechanism of CoCrFeMnNi HEAs in the HCP phase is dominated by twinning-induced plasticity, which is verified using transmission electron microscopy.

Evaluation of a Triage Checklist for Mild COVID-19 Outpatients in Predicting Subsequent Emergency Department Visits and Hospitalization during the Isolation Period: A Single-Center Retrospective Study.

Managing mild illness in COVID-19 and predicting progression to severe disease are concerning issues. Here, we investigated the outcomes of Japanese patients with mild COVID-19, and identified triage risk factors for further hospitalization and emergency department (ED) visits at a single tertiary hospital. A triage checklist with 30 factors was used. Patients recommended for isolation were followed up for 10 days for subsequent ED visits or hospital admission. Overall, 338 patients (median age, 44.0; 45% women) visited the clinic 5.0 days (median) after symptom onset. Thirty-six patients were immediately hospitalized following triage; others were isolated. In total, 72 non-hospitalized patients visited the ED during their isolation, and 30 were hospitalized after evaluation for oxygen desaturation. The median ED visit and hospitalization durations after symptom onset were 5.0 and 8.0 days, respectively. The checklist factors associated with hospitalization during isolation were age > 50 years, body mass index > 25 kg/m2, hypertension, tachycardia with pulse rate > 100/min or blood pressure > 135 mmHg at triage, and >3-day delay in hospital visit after symptom onset. No patients died. Altogether, 80% of patients with mild COVID-19 could be safely isolated at home. Age, BMI, underlying hypertension, date after symptom onset, tachycardia, and systolic blood pressure at triage might be related to later hospitalization.

The hard-core effect on PC-SAFT to model asphaltene precipitation in petroleum reservoir fluids

In this work, a hard-core version of the Perturbed Chain-Association Fluid Theory Equation of State (PC-SAFT EoS) is proposed and used to predict upper asphaltene onset pressures (AOPs), bubble points (BPs), and precipitated asphaltene amounts for eighteen real petroleum reservoir fluids around the world. As a result, for the same assumed asphaltene molecular weight (MW) value, this hard-core PC-SAFT model predicts lower AOPs than the other two PC-SAFT versions here tested, including the original version of PC-SAFT. The AOPs and precipitated asphaltene amounts are found to be directly related to the asphaltene MW values used for each PC-SAFT model. The hard-core PC-SAFT model here presented is the PC-SAFT version that requires the lowest asphaltene MWs and predicts the lowest precipitated asphaltene amounts for the eighteen fluids modeled.

A Comparison between the Perturbed-Chain Statistical Associating Fluid Theory Equation of State and Machine Learning Modeling Approaches in Asphaltene Onset Pressure and Bubble Point Pressure Prediction during Gas Injection.

Predicting asphaltene onset pressure (AOP) and bubble point pressure (Pb) is essential for optimization of gas injection for enhanced oil recovery. Pressure-Volume-Temperature or PVT studies along with equations of state (EoSs) are widely used to predict AOP and Pb. However, PVT experiments are costly and time-consuming. The perturbed-chain statistical associating fluid theory or PC-SAFT is a sophisticated EoS used for prediction of the AOP and Pb. However, this method is computationally complex and has high data requirements. Hence, developing precise and reliable smart models for prediction of the AOP and Pb is inevitable. In this paper, we used machine learning (ML) methods to develop predictive tools for the estimation of the AOP and Pb using experimental data (AOP data set: 170 samples; Pb data set: 146 samples). Extra trees (ET), support vector machine (SVM), decision tree, and k-nearest neighbors ML methods were used. Reservoir temperature, reservoir pressure, SARA fraction, API gravity, gas–oil ratio, fluid molecular weight, monophasic composition, and composition of gas injection are considered as input data. The ET (R2: 0.793, RMSE: 7.5) and the SVM models (R2: 0.988, RMSE: 0.76) attained more reliable results for estimation of the AOP and Pb, respectively. Generally, the accuracy of the PC-SAFT model is higher than that of the AI/ML models. However, our results confirm that the AI/ML approach is an acceptable alternative for the PC-SAFT model when we face lack of data and/or complex mathematical equations. The developed smart models are accurate and fast and produce reliable results with lower data requirements.

Calculating adsorption isotherms using the two-phase thermodynamic method and molecular dynamics simulations

We describe the calculation of adsorption isotherms from molecular dynamics simulations based on the two-phase thermodynamic (2PT) model. The 2PT model developed for bulk fluid phases treats the gas-like components as hard spheres (HSs), which correctly recovers the limiting behaviors of unconfined fluids. We showed that this treatment, however, does not always lead to the correct zero-loading behavior in strongly confining systems. For methane adsorption into zeolite MFI, the HS reference state underestimates entropy by up to 20% at low loadings and leads to an order-of-magnitude increase in the adsorption onset pressure. To fix these issues, we propose the use of ideal adsorbed gas (IAG) as the gas reference model, the properties of which can be computed using the Widom insertion method on an empty adsorbent. We further describe three routes to compute adsorption isotherms from the Helmholtz free energy at different loadings. Comparing against established Monte Carlo (MC) methods, we found that the adsorption isotherms obtained using the IAG reference state agrees to within 40%, which corresponds to deviations of <5% in adsorption free energy. The isotherms calculated using the HS reference state underestimate the adsorption uptake at low to medium loadings in strongly confining systems, but its accuracy improves at higher loadings and as the pore size increases relative to the sorbate diameter. The methods described here provide an alternative approach for computing adsorption isotherms when MC simulations in an open ensemble are undesirable and enable a direct comparison of computed adsorption thermodynamics with experiments.

Drainage of pancreatic fluid collections in acute pancreatitis: A comprehensive overview

Moderately severe and severe acute pancreatitis is characterized by local and systemic complications. Systemic complications predominate the early phase of acute pancreatitis while local complications are important in the late phase of the disease. Necrotic fluid collections represent the most important local complication. Drainage of these collections is indicated in the setting of infection, persistent or new onset organ failure, compressive or pressure symptoms, and intraabdominal hypertension. Percutaneous, endoscopic, and minimally invasive surgical drainage represents the various methods of drainage with each having its own advantages and disadvantages. These methods are often complementary. In this minireview, we discuss the indications, timing, and techniques of drainage of pancreatic fluid collections with focus on percutaneous catheter drainage. We also discuss the novel methods and techniques to improve the outcomes of percutaneous catheter drainage.

Experimental investigation and thermodynamic modeling of asphaltene precipitation during pressure depletion and gas injection at HPHT conditions in live oil using PC-SAFT EoS

Due to the high costs associated with asphaltene precipitation and deposition, the study of this flow assurance problem has always been a major issue in the petroleum industry. We studied the asphaltene phase behavior in four Iranian live oil samples. First, asphaltene onset pressure and the amounts of the precipitated asphaltene during pressure depletion and gas injection at high-pressure high-temperature (HPHT) conditions were measured, experimentally. Then, thermodynamic modeling of asphaltene precipitation was performed using the perturbed chain form of the statistical associating fluid theory (PC-SAFT). In previous researches, PC-SAFT equation of state (EoS) along with the standard method of characterization was applied to light crude oil having low asphaltene content only, while in this work, three of the samples were heavy oil with high asphaltene content. To perform the thermodynamic modeling, the oil samples were characterized by two different methods. In the first method, the adjustable parameters of the model, which are the aromaticity of aromatics + resins and the aromaticity of asphaltene, were adjusted separately. In the second method, both of the parameters of the model were tuned simultaneously, as one of the novelties of this research. Then the amounts of precipitated asphaltene were modeled using the aforementioned characterization methods, and the results were compared to the experimental data. According to the results, simultaneous adjustment of the model parameters in the heavy oil samples could improve the average absolute deviation (AAD) by 5% - 12%. However, no remarkable improvement was observed for the light oil sample. For two of the oil samples, the proposed model showed a good agreement with the experimental data as the calculated AAD were 14% and 26%. For the other oil samples, the trend of the experimental data was predicted by the model, but the values of the experimental data could not be matched. We were able to solve this problem by introducing a confidence factor for experimentally measured data. By considering this weight factor, in one of the samples, the AAD was reduced by about 70% and reached 24%, and in other oil sample, the error decreased by 90% and reached 31%.

Development of a Downhole Measurement System for Phase Behavior of Reservoir Crude Oils and Retrograde Condensates

This article reviews the scientific findings that were integrated into a downhole prototype to measure hydrocarbon phase behavior. While laboratory measurements of bubble point pressure (Pb), asphaltene onset pressure (AOP), and dewpoint pressure (Pd) are well established and have been extensively studied, such measurements of reservoir crude oils are novel downhole due to their operational, hydraulic, and interpretational complexities. Furthermore, such laboratory measurements typically take several hours to complete and can only be carried out by skilled personnel. For the downhole measurement, novel science and understanding were developed to reduce the measurement time to minutes and to automate the workflow. This article reviews the science and technology that enabled these downhole measurements to be made rapidly and provides field examples of how sampling is optimized and quality is validated in real time.

COURSE OF PREECLAMPSIA IN CHRONIC KIDNEY DISEASE (CKD)

Objective: The aim of the study is to analyze the incidence and characteristics of PE in patients (pts) with CKD. Design and method: A retrospective analysis of 60 case histories of pregnant women with CKD 1–4 stages followed in the nephrology center for pregnant women from 2018–2021 was carried out. 20 of them developed PE: CKD 1 – 7/23 (30,4%), CKD 2 – 3/10 (30%), CKD 3 – 7/23 (30,4%), CKD 4 – 3/4 (75%), then the course of their pregnancy was analyzed. Indicators of proteinuria (PU) and blood pressure (BP) were assessed at the time of the first visit to the center and further, at the time of PE. Results: In the group of pts with PE and CKD (n = 20), the mean age was 29.3 (± 6) years. The causes of CKD were: glomerulonephritis - 13 (65%); tubulointerstitial nephritis 2 (10%); aHUS 2 (10%) and one each - polycystic kidney disease, diabetic nephropathy, APS-associated nephropathy. The mean term of gestation at the time of first visit to the dedicated center was 15.5 weeks. The mean RU was 1.4 (± 0.8) g/l. Arterial hypertension had 9 pts.The mean BP at the first visit was: SBP 129 (± 15)/DBP 85 (± 10) mm. Hg. PE before 34 weeks of gestation developed in 13 (65%) pts, and the mean term for the development of PE was 31.8 weeks [24; 38]. The mean BP at the moment of PE was 139 (± 16.6)/89 (± 10) mm Hg, so in 45% (n = 9) of cases, BP did not meet the criteria for PE. The majority of women showed an increase in PU 3,6 ± 2,9 g/l. The mean value of the sFLT1/PLGF ratio in PE was 135, that for a given gestational term (31.8 weeks) corresponds to severe ischemic damage to the placenta. Conclusions: We believe that the main features of PE in pts with CKD are its earlier onset and lower blood pressure values than those provided by modern criteria for PE. In this regard, it is important to monitor the angiogenic coefficient in dynamics in pregnant women with CKD.

Effect of Wettability on Vacuum-Driven Bubble Nucleation

Nucleation is the formation of a new phase that has the ability to irreversibly and spontaneously grow into a large-sized nucleus within the body of a metastable parent phase. In this experimental work, the effect of wettability on the incipiation of vacuum-driven bubble nucleation, boiling, and the consequent rate of evaporative cooling are studied. One hydrophilic (untreated), and three hydrophobic (chlorinated polydimethylsiloxane, chlorinated fluoroalkylmethylsiloxane and (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane) glass vials of different wettabilities were filled with degassed deionized water and exposed to a controlled vacuum inside a transparent desiccator. The vacuum was increased by 34 mbar abs. (1 inHg rel.) steps with 15-min waiting period to observe bubble nucleation. The average onset pressures for gas/vapor bubble nucleation in CM, CF, and HT vials were 911 ± 30, 911 ± 34, and 925 ± 17 mbar abs., respectively. Bubble nucleation was not observed in hydrophilic vial even at 65 mbar abs. pressure. During the vacuum boiling at 65 mbar abs., the average temperatures of water in hydrophilic, CM, CF, and HT vials reduced from room temperature (~22.5 °C) to 15.2 ± 0.9, 13.1 ± 0.9, 12.9 ± 0.5, and 11.2 ± 0.3 °C, respectively. The results of this study show that the wettability of the container surface has a strong influence on the onset vacuum for vapor/gas bubble nucleation, rate of vacuum boiling, and evaporative cooling. These findings are expected to be useful to develop wettability-based vacuum boiling technologies.

Theoretical Studies of Furan and Thiophene Nanothreads: Structures, Cycloaddition Barriers, and Activation Volumes.

This theoretical study examines the formation, structure, and stability of two of the most ordered nanothreads produced yet, those derived from furan and thiophene. The energetic consequences and activation barriers of the first two steps of oligomerization via a Diels-Alder mechanism were examined. The ca. 20 GPa difference in the synthetic pressures (lower for furan) is explainable in terms of the greater loss of aromaticity by the thiophene. The effects of pressure on the reaction profiles, operating through a volume decrease along the reaction coordinate, are illustrated. The interesting option of polymerization proceeding in one or two directions opens up the possibility of polymers with opposing, cumulative dipole moments. The computed activation volumes are consistently more negative for furan, in accordance with the lower onset pressure of furan polymerization. The energetics of three ordered polymer structures were examined. The syn polymer, with all O/S atoms on the same side, if not allowed to distort, is at a high energy relative to the other two due to the O/S lone pair repulsion, understandably greater for S than for O at the 2.8/2.6 Å separation. Set free, the syn isomers curve or arch in two- or three-dimensional (helical) ways, whose energetics are traced in detail. The syn polymer can also stabilize itself by twisting into zig-zag or helical energy minima. The release of strain in a linear thread as the pressure is relaxed to 1 atm, with consequent thread curving, is a likely mechanism for the observed loss of the crystalline order in the polymer as it is returned to ambient pressure.

Optimization of Synthetic Vocal Fold Models for Glottal Closure.

Synthetic, self-oscillating models of the human vocal folds are used to study the complex and inter-related flow, structure, and acoustical aspects of voice production. The vocal folds typically collide during each cycle, thereby creating a brief period of glottal closure that has important implications for flow, acoustic, and motion-related outcomes. Many previous synthetic models, however, have been limited by incomplete glottal closure during vibration. In this study, a low-fidelity, two-dimensional, multilayer finite element model of vocal fold flow-induced vibration was coupled with a custom genetic algorithm optimization code to determine geometric and material characteristics that would be expected to yield physiologically-realistic frequency and closed quotient values. The optimization process yielded computational models that vibrated with favorable frequency and closed quotient characteristics. A tradeoff was observed between frequency and closed quotient. A synthetic, self-oscillating vocal fold model with geometric and material properties informed by the simulation outcomes was fabricated and tested for onset pressure, oscillation frequency, and closed quotient. The synthetic model successfully vibrated at a realistic frequency and exhibited a nonzero closed quotient. The methodology described in this study provides potential direction for fabricating synthetic models using isotropic silicone materials that can be designed to vibrate with physiologically-realistic frequencies and closed quotient values. The results also show the potential for a low-fidelity model optimization approach to be used to tune synthetic vocal fold model characteristics for specific vibratory outcomes.

Effects of Supplemental Oxygen on Cardiovascular and Respiratory Interactions by Extended Partial Directed Coherence in Idiopathic Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic and restrictive disease characterized by fibrosis and inflammatory changes in lung tissue producing a reduction in diffusion capacity and leading to exertional chronic arterial hypoxemia and dyspnea. Furthermore, clinically, supplemental oxygen (SupplO2) has been prescribed to IPF patients to improve symptoms. However, the evidence about the benefits or disadvantages of oxygen supplementation is not conclusive. In addition, the impact of SupplO2 on the autonomic nervous system (ANS) regulation in respiratory diseases needs to be evaluated. In this study the interactions between cardiovascular and respiratory systems in IPF patients, during ambient air (AA) and SupplO2 breathing, are compared to those from a matched healthy group. Interactions were estimated by time series of successive beat-to-beat intervals (BBI), respiratory amplitude (RESP) at BBI onset, arterial systolic (SYS) and diastolic (DIA) blood pressures. The paper explores the Granger causality (GC) between systems in the frequency domain by the extended partial directed coherence (ePDC), considering instantaneous effects. Also, traditional linear and nonlinear markers as power in low (LF) and high frequency (HF) bands, symbolic dynamic indices as well as arterial baroreflex, were calculated. The results showed that for IPF during AA phase: 1) mean BBI and power of BBI-HF band, as well as mean respiratory frequency were significantly lower (p < 0.05) and higher (p < 0.001), respectively, indicating a strong sympathetic influence, and 2) the RESP SYS interaction was characterized by Mayer waves and diminished RESP BBI, i.e., decreased respiratory sinus arrhythmia. In contrast, during short-term SupplO2 phase: 1) oxygen might produce a negative influence on the systolic blood pressure variability, 2) the arterial baroreflex reduced significantly (p < 0.01) and 3) reduction of RSA reflected by RESP BBI with simultaneous increase of Traube-Hering waves in RESP SYS (p < 0.001), reflected increased sympathetic modulation to the vessels. The results gathered in this study may be helpful in the management of the administration of SupplO2.

Theory-directed discovery of high-temperature superconductivity in clathrate hydrides at high pressure

Theory-directed discovery of high-temperature superconductivity in clathrate hydrides at high pressure

Effects of hydrostaticity and Mn-substitution on dolomite stability at high pressure

Abstract Studying the structural evolution of the dolomite group at high pressure is crucial for constraining the deep carbon cycle and mantle dynamics. Here we collected high-pressure laser Raman spectra of natural Mg-dolomite CaMg(CO3)2 and Mn-dolomite kutnohorite Ca1.11Mn0.89(CO3)2 samples up to 56 GPa at room temperature in a diamond-anvil cell (DAC) using helium and neon as a pressure-transmitting medium (PTM), respectively. Using helium or neon can ensure samples stay under relatively hydrostatic conditions over the investigated pressure range, resembling the hydrostatic conditions of the deep mantle. Phase transitions in CaMg(CO3)2 were observed at 36.1(25) GPa in helium and 35.2(10) GPa in neon PTM from dolomite-II to -III, respectively. Moreover, the onset pressure of Mn-dolomite Ca1.11Mn0.89(CO3)2-III occurs at 23−25 GPa, about 10 GPa lower than that of Mg-dolomite-III, suggesting that cation substitution could significantly change the onset pressure of the phase transitions in the dolomite group. These results provide new insights into deep carbon carriers within the Earth’s mantle.

Predictors of stroke favorable functional outcome in Guinea, results from the Conakry stroke registry

Low- to middle-income countries (LMICs) now bear most of the stroke burden. In LMICs, stroke epidemiology and health care systems are different from HICs. Therefore, a high-income country (HIC)-based predictive model may not correspond to the LMIC stroke context. Identify the impact of modifiable variables in acute stroke management in Conakry, Guinea as potential predictors of favorable stroke outcome. Data were extracted from the Conakry stroke registry that includes 1018 patients. A logistic regression model was built to predict favorable stroke outcomes, defined as mRS 0–2. Age, admission NIHSS score, mean arterial blood pressure and capillary glycemia were chosen as covariates. Delay to brain CT imaging under 24 h from symptom onset, fever, presence of sores and abnormal lung auscultation were included as factors. NIHSS score on admission, age and ischemic stroke were included in the null model as nuisance parameters to determine the contribution of modifiable variables to predict stroke favorable outcome. Lower admission NIHSS, brain CT imaging within 24 h of symptoms onset and lower mean arterial blood pressure emerged as a significant positive predictors of favorable stroke outcome with respective odd ratios (OR) of 1.35 [1.28–1.43], 2.1 [1.16–3.8] and 1.01 [1.01–1.04]. The presence of fever or sores impacted negatively stroke favorable outcomes with OR of 0.3 [0.1–0.85] and 0.25 [0.14–0.45]. The area under receiver operating characteristic curves (AUC) of the model was 0.86. This model explained 44.5% of the variability of the favorable stroke outcome with 10.2% of the variability explained by the modifiable variables when admission NIHSS, and ischemic stroke were included in the null model as nuisance parameter. In the Conakry stroke registry, using a logistic regression to predict stroke favorable outcome, five variables that led to an AUC of 0.86: admission NIHSS, early brain CT imaging, fever, sores and mean blood pressure. This paves the way for future public health interventions to test whether modulating amendable variables leads to increased favorable stroke outcomes in LMICs.

CO2 Adsorption Enhanced by Tuning the Layer Charge in a Clay Mineral.

Due to the compact two-dimensional interlayer pore space and the high density of interlayer molecular adsorption sites, clay minerals are competitive adsorption materials for carbon dioxide capture. We demonstrate that with a decreasing interlayer surface charge in a clay mineral, the adsorption capacity for CO2 increases, while the pressure threshold for adsorption and swelling in response to CO2 decreases. Synthetic nickel-exchanged fluorohectorite was investigated with three different layer charges varying from 0.3 to 0.7 per formula unit of Si4O10F2. We associate the mechanism for the higher CO2 adsorption with more accessible space and adsorption sites for CO2 within the interlayers. The low onset pressure for the lower-charge clay is attributed to weaker cohesion due to the attractive electrostatic forces between the layers. The excess adsorption capacity of the clay is measured to be 8.6, 6.5, and 4.5 wt % for the lowest, intermediate, and highest layer charges, respectively. Upon release of CO2, the highest-layer charge clay retains significantly more CO2. This pressure hysteresis is related to the same cohesion mechanism, where CO2 is first released from the edges of the particles thereby closing exit paths and trapping the molecules in the center of the clay particles.

Performance evaluation and improvement of PC-SAFT equation of state for the asphaltene precipitation modeling during mixing with various fluid types

One of the significant problems of the upstream flow assurance community is precipitation or deposition of asphaltene that leads to affect the economics of oil production seriously. Knowledge of asphaltene onset pressure (AOP) and amount of asphaltene precipitation in the change of temperature, pressure, and composition is the essential information for preventing this problem. Recent studies have shown that thermodynamic models based on the solubility nature of asphaltenes using an equation of state (EOS) are the most effective approach to asphaltene behavior modeling. In this research, the common version of the SAFT equation, known as the Perturbed Chain form of Statistical Association Fluid Theory (PC-SAFT) EOS without using association terms, has been employed and evaluated during the pure gas and other fluid types injection or mixing. In the case of pure gas injection (single components, for instance, N2 or CO2 injection), the model results have shown that using the reference values of the PC-SAFT parameters (m, σ, ε/k), those are reported in the literature, may not predict the weight percentage of the asphaltene precipitation accurately. It will be shown that considering these parameters as the adjustable variables can improve the model prediction for the asphaltene precipitation behavior. Furthermore, a new methodology has been suggested to characterize the injection fluid while its SARA (Saturates-Aromatics-Resins-Asphaltenes) analysis is not reported. This methodology is established in accordant with the material balance concept; in fact, the distribution of SARA fractions for the injection fluid will be estimated from the characterized crude oil. Six systems of crude oil and injection fluid, including pure N2, pure methane, pure CO2, wet gas, and liquid condensate, have been taken under study to evaluate the accuracy and flexibility of the proposed methodology by comparing to the available asphaltene experimental data.

Tuning the onset pressure of pressure-induced phase transition in indium phosphide by extrinsic doping

In-situ angle-dispersive X-ray diffraction (ADXRD) and Raman scattering were carried out to delineate the phase transitions under pressure in p-type zinc-doped indium phosphide (InP:Zn) at ambient temperature. The ADXRD measurements with pressure up to 17.3(2) GPa reveal that InP:Zn transforms from zinc-blende (ZB) to rock-salt (RS) structure in a pressure range of 8.1(2) - 8.6(1) GPa. The Raman scattering measurements indicate that the phase transition proceeds continuously over a wide range of pressure and reaches completion at the highest pressure applied (14.5(2) GPa) with significant metallization, as suggested by the disappearance of the transverse optical (TO) and longitudinal optical (LO) modes. In contrast, originally absent at ambient pressure, additional Raman shift of Zn local vibrational modes (LVMs), appeared at 276 cm-1 and 420.7(1) cm-1 within the pressure range of 2.2(1) up to 10.1(2) GPa, which can be attributed to Zn3P2 and VPZnInVP LO modes, respectively. The zero-pressure isothermal bulk moduli and its first order pressure derivatives for the zinc-blende InP:Zn are 79.44(2) GPa and 3.92(1), respectively. A total enthalpy change of about 45.45 KJ•mole-1 was derived for the ZB to RS structure transformation occurring at the pressure of 8.6(1) GPa. The present results suggest that diffusion of Zn in InP:Zn may have been governed by the modified substitution and interstitial (S–I) mechanism. Moreover, comparisons on the pressure-dependent behaviors in InP:Zn, InP:S, and InP:Fe extrinsically doped systems revealed that the exact type of the defects introduced into the lattice upon doping may have played crucial roles in the pressure-induced phase transitions.

Timing is everything: snoring onset and blood pressure trajectories in pregnancy.

Timing is everything: snoring onset and blood pressure trajectories in pregnancy.