DAM BREACH ANALYSIS AND PARAMETER SENSITIVITY ANALYSIS ALONG A RIVER REACH USING HECRAS

A dam break is a low-probability, high risk catastrophe event that is extremely destructive and has a substantial negative socio-economic impact on downstream and nearby areas. Simulating dam breach and analyzing flood propagation downstream from those events is vital for identifying and minimizing the risks associated downstream of dam location. This study is intended to anlayse the effect of overtopping failure of dam for two scenario  (a) base-case scenario (scenario with average value of dam breach parameters from their range) and (b) worst case scenario (the breach with largest geometry, shortest formation time and highest peak outflow magnitude). Further, a hydrodyanmic modelling is perfomed to  investigate  the sensitivity analysis (local and global) of five dam breach parameters (dam breach elevation, dam breach width, breach formation time, weir coefficient, trigger failure elevation) on breach outflow in a proposed hydropower project located in Nepal. Aeronautical Reconnaissance Coverage Geographic Information System (ArcGIS), Hydraulic Engineering Center River Analysis System (HEC-RAS) and OriginPro 2022b are utilized to analyse the effect of  dam breach and parameter sensitivity. Generation of outflow hydrograph shows that worst case scenario has devasting effect downstream with innudation of 1047 of househols and 50.83 kilometers of roads. The breach velocty was recorded as 15.16 m/s and 20.85 m/s for base and worst case respectively. The minimum depth and maximum depth of flooding downstream from dam location was found to be 24.51 m and 73.6 m for base case and 47.43 m and 106.75 m for worst case. Due to backwater effect at Bheri river, peak flow at 14 km downstream from dam reduces significantly to 124852.57 m3/s and 244204.41 m3/s for base and worst case respectively. From local sensitivty analysis it has been found that, dam breach elevation is more sensitive and triggering failure elevation is less sensitive for peak outflow hydrograph. Whereas, dam breach width seems more sensitive and TFE seems least sensitive for peak outflow using Monte Carlo Simulation for gloal sensitivity

Postpartum Care Services during the Fourth Stage of Labour in Bharatpur Hospital of Nepal

Background: Postnatal care is an important part of maternal care, as serious and life-threatening complications can occur in the postpartum period. So, this study was conducted to assess the level of postpartum care services during the fourth stage of labour in the maternity ward of Bharatpur hospital in the Chitwan district of Nepal. Methods: Cross-sectional hospital-based study was done among women admitted in the maternity ward for vaginal delivery in Bhartapur hospital in Chitwan. Total 218 sample size derived by using the formula; n= N/1+N (e²). A set of data collection tool was developed, pretested and finalized. Part-1 of the tool was related to socio-demographic features of respondents, Part-2 and 3 of the tool was used as a checklist to assess institutional characteristics and level of postpartum care services respectively. The structured checklist had twenty-two items including twelve critical steps. The purpose of the study explained to the respondents; verbal informed consent obtained from respondents and ethical approval from the Institutional review committee of Chitwan Medical College. Results: The significant association observed between postpartum care during the fourth stage of labour and residence of mothers (p=0.021). Conclusions: Postpartum care in Bharatpur hospital is poor and there is an urgent need to develop plans and programs to enhance the capacity of staffs and health institutions to provide postpartum care according to the WHO recommendation guideline.  

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

First-principles study of self-diffusion and viscous flow in diopside (CaMgSi \u3csub\u3e2\u3c/sub\u3eO \u3csub\u3e6\u3c/sub\u3e) liquid

We have carried out equilibrium molecular dynamics simulations of CaMgSi O (diopside) liquid as a function of pressure (up to 150 GPa) and temperature (2200 to 6000 K) using density functional theory. Self-diffusion of Mg/Ca atoms decouples most from that of framework (Si/O) atoms at 2200 K and zero pressure, and all diffusivities become increasingly similar as temperature and pressure increase. The predicted temperature variations of all transport coefficients at zero pressure closely follow the Arrhenian law with activation energies of 107 to 161 kJ/mol. However, their pressure variations show significant deviations from the Arrhenius behavior. Along the 3000 K isotherm, the Si and O self-diffusivities show non-monotonic variations up to 20 GPa and then rapidly decrease upon further compression. The melt viscosity also shows a weak anomaly in the low-pressure regime before it starts to increase rapidly with pressure. Our results agree favorably with experimental observations of low-pressure non-uniform variations of Si and O self-diffusivities and viscosity. The predicted complex dynamical behavior requires pressure-volume dependent activation volumes and can be associated with structural changes occurring on compression. 2

First-principles simulations of MgO tilt grain boundary: Structure and vacancy formation at high pressure

Three {n10}/[001] tilt grain boundaries (n = 2, 3, and 4) of MgO were studied as a function of pressure from first principles within density functional theory. Our results show that the physical properties of the grain boundary are very distinct from the bulk properties. The predicted symmetric boundary containing well-defined dislocation pipes at zero pressure transforms to asymmetric boundaries with denser structures at higher pressures. The asymmetric boundary structure stable at 50 GPa can be associated with a shear in the boundary plane, whereas the asymmetric boundary structure stable at 100 GPa can be associated with an additional shear in the direction perpendicular to the boundary plane. Unlike in the bulk, several nonequivalent sites exist for vacancy formation in the boundary regions, and the calculated Schottky defect formation enthalpy varies among different boundaries with the {310} and {410} boundary values at zero pressure being similar to the bulk value. Pressure increasingly stabilizes the boundary vacancies relative to the bulk thereby causing an enhancement in the vacancy concentration, which is further enhanced due to high-binding energy for cation-anion vacancy pairs in the interfacial regions. Also, the grain boundary was shown to induce electronic states in the band gap below the conduction band, which can trap the electrons inside the free space at the interface. Additional states with strong electron localization character appear at the boundary in the presence of the vacancies. Our results are expected to be useful to understand how grain boundaries can serve as primary storage sites for defects and high-diffusion pathways

First-principles simulations of native point defects and ionic diffusion in high-pressure polymorphs of silica

Several native point defects including vacancies, interstitials, and their complexes were studied in high-pressure polymorphs of silica (stishovite, CaCl2, α -PbO2, and pyrite types) up to 200 GPa within density-functional theory. The formation enthalpies of the individual defects strongly depend on atomic chemical potentials and the Fermi level. Their values were shown to increase by a factor of 2 over the entire pressure range studied with large differences in some cases between different phases. The Schottky defects are energetically most favorable at zero pressure whereas O-Frenkel pairs become systematically more favorable at pressures higher than 20 GPa. The activation enthalpies of ionic migrations obtained by the nudged-elastic-band method suggest that the interstitial mechanisms are favored over the vacancy hoping mechanisms. The geometric and electronic structures of defects and migrating ions vary largely among different types of defects. In particular, the O defects introduce localized electronic states. These structures remain qualitatively unchanged with compression showing similar trends among different polymorphs. © 2009 The American Physical Society

Ab initio investigations of native and protonic point defects in Mg\u3csub\u3e2\u3c/sub\u3eSiO\u3csub\u3e4\u3c/sub\u3e polymorphs under high pressure

Density functional theory simulations were carried out to study the formation and migration energetics and geometric structures of the native point defects and protons in Mg SiO polymorphs (namely, forsterite, wadsleyite and ringwoodite) up to 30 GPa pressure. The energetic favorability of the vacancy and interstitial defects was shown to strongly depend on the atomic and electron chemical potentials. Among the charge-balanced defects studied, the Mg -Frenkel defects are energetically most favorable in forsterite whereas the MgO pseudo-Schottky defects are energetically most favorable in wadsleyite and ringwoodite. Our results for the ion migration enthalpies calculated using the nudged-elastic-band technique suggest that the Mg migration is easiest in forsterite and ringwoodite whereas Si migration is easiest in wadsleyite. The proton incorporations at the interstitial and vacant cationic sites were investigated. In the extrinsic limit, the proton incorporation is energetically most favorable at V ″″ site for up to three protons. Addition of one more proton prefers to go to V ″ site. In the intrinsic limit, however, the interstitial and Mg-vacancy sites remain the most favorable. The predicted barrier for the interstitial-to-interstitial proton migration is smaller than that for the magnesium vacancy-to-interstitial migration, and among three phases ringwoodite has the lowest barrier. The effects of proton incorporation on the transition pressure and pressure-volume equation of state were shown to be significant. 2 4 Si Mg 2

First-principles simulations of thermodynamical and structural properties of liquid Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e under pressure

First-principles molecular dynamics simulations within local density approximation were carried out for liquid alumina over a pressure range from 0 to 150 GPa at 3000, 4000, and 6000 K. Liquid alumina is more compressible and less dense than solid alumina, and the density difference between two phases decreases with compression with a density crossover occurring around 90 GPa at 3000 K. The calculated thermodynamic properties including specific heat, thermal expansion coefficient, and Grüneisen parameter are strongly pressure dependent. The liquid structure is more sensitive to compression than temperature: mean Al-O and O-Al coordination numbers which remain nearly unchanged on isochoric heating increase from 5.2 and 3.4, respectively, at 0 GPa to 6.8 and 4.5, respectively, at 150 GPa along 3000 K isotherm. Coordination environments consist of various species with low-coordination species (three- and four-coordinated Al atoms) disappearing and high-coordination species (six- and seven-coordinated Al atoms) appearing as the liquid is compressed. We also analyze the structure in terms of bond distances and bond angles. © 2011 American Physical Society

First-principles prediction of pressure-enhanced defect segregation and migration at MgO grain boundaries

Understanding the ability of grain boundaries to accommodate point defects and enhance diffusion rates in mantle materials represents an important but challenging problem. Extant experimental studies and recent computational efforts are mainly limited to the ambient pressure. Here, we investigate this problem for MgO at the atomistic level by performing first-principles simulations, based on density functional theory, of the {310)}/[001] tilt grain boundary in MgO at pressures up to 100 GPa. Our results show that native defects and impurities (Ca, Al, and proton modeled here) favorably segregate to the boundary, with the segregation considerably increasing with pressure. They also imply that grain boundary diffusion is easier, and more anisotropic and complex than bulk (lattice) diffusion: The calculated migration enthalpies for host ions and impurities at the grain boundary are smaller than the bulk values, more so at higher pressures with their values being as low as ~1.5 eV at 100 GPa compared to the bulk values of ~4 eV. Thus demonstrated high-defect activity of grain boundaries in MgO-a major phase of Earth\u27s lower mantle is expected to be relevant to our understanding of mantle rheology and geochemical process