Unusual Pressure Research Articles

Wave induced stress profile on a paired column semisubmersible hull formation for column reinforcement

A study into reinforcing the hull of the recently developed paired column semisubmersible platform has been carried out by understanding the stress profile around its columns from hydrodynamic interaction during survival and extreme weather conditions in the Gulf of Mexico. The conceptualization of this hull system is to enable dry-tree technology on semisubmersibles for deep-sea exploration. Its hydrodynamic response behaviour has been confirmed to be compatible with this technology, although its size and high steel requirement are of major disadvantage. Preliminary CFD study has showed an unusual flow behaviour within and around the hull due to its unique column arrangement. This behaviour creates an unusual hydrodynamic pressure profile on the hull, dominated by the wave parameters. Numerical models were developed using ANSYS and AQWA to compute the stress distribution on the columns from this unique uneven hydrodynamic pressure. The boundary conditions for the FE-model were formulated using hydrostatic stiffness theories and hydrodynamic response plots developed in Orcaflex. The results have showed high stress concentration on the inner columns. For operating conditions (low wave amplitude), the wave propagating direction was observed to have little or no effect on the column stress distribution. Significant effect of the wave propagating angle was observed as its amplitude gradually increases. Results for topside and deck mass effect on the stress distribution on the columns also suggested high stress distribution around the joint area of the inner columns for extreme and survival weather conditions, irrespective of the flow orientation.

Finite-strain Landau theory applied to the high-pressure phase transition of lead titanate

Standard Landau theory coupled to infinitesimal strain allows a concise description of the temperature-driven ferroelectric tetragonal-to-cubic phase transition in ${\mathrm{PbTiO}}_{3}$ at ambient pressure. Unfortunately, it fails to cover its high-pressure counterpart at ambient temperature. For example, the experimental transition pressure is vastly underestimated, and neither the change from first to second order with increasing pressure nor the unusual pressure dependence of the tetragonal unit cell parameters observed in experiment are reproduced. Here we demonstrate that a combination of density functional theory and a recently constructed finite-strain extension of Landau theory provides a natural mechanism for resolving these discrepancies between theory and experiment. Our approach also allows us to determine the full tetragonal-cubic phase boundary in the $(P,T)$ plane including an estimate of the tricritical point. We show that a careful analysis of the thermal elastic baseline is an essential ingredient to the success of this theory.

Knowledge regarding Danger Signs of Pregnancy among Antenatal Mothers

Pregnancy is the most beautiful phase in a women's life. It brings about emotional and physiological changes as well as poses extra demands on the body. Sometimes, a pregnant woman may experience some signs and symptoms which signal danger. The danger signs in pregnancy include vaginal spotting or bleeding at any time, leaking of fluid from the vagina, unusual abdominal pain, cramping, pelvic pressure, or persistent backache, persistent nausea and vomiting, especially in the second and third trimester. The other danger signs in pregnancy are persistent headache or blurred vision, marked swelling of the ankles and especially of hands and face, painful or burning urination, foul-smelling vaginal discharge, chills or fever, feeling very tired, and decreased fetal movements in the third trimester. A descriptive study of 50 antenatal mothers attending outpatient department was performed. Interviews were conducted at Arpana hospital, Karnal, using a structured knowledge questionnaire. Findings of the study revealed that across the samples, majority of the antenatal mothers belong to 22–25 years 27 (54%), Hindu religion 38 (76%), rural community 27(54%). Majority of antenatal mothers had graduation and above level of education 21(42%) and 42(80%) were housewife. The result showed 58% of the antenatal mothers had good level of knowledge regarding danger signs of pregnancy followed by 30% of the antenatal mothers had average level of knowledge and only 12% had very good level of knowledge regarding danger signs of pregnancy.

The variation of fetal heart rhythm towards delivery

In this paper, we investigate the variation of the fetal heart rate as we approach delivery. The fetal heart rate is affected by several factors, including the uterine contractions, the amount of oxygen in blood, the sex of the fetus, etc. We isolate specific biochemical markers or other measurable characteristics and compare plots expressing the average fetal heart rate versus the time remaining until the delivery, for subjects with different values in these characteristics. Our motivation is to study the effect of different values, related to a biochemical marker or characteristic, on the heart rate of the fetus. One important observation that came out from this study is the increased discriminating power presented between different groups of subjects, appearing in the time period before the delivery, where the heart works under unusual pressure. In some cases, even though the average fetal heart rate associated to each group can not be discriminated during the early stages, the differentiation becomes possible before delivery, since the group that is expected to react better under pressure achieves to keep the heart rate in higher levels.

DISCOVERY OF A POSSIBLE COOL WHITE DWARF COMPANION FROM THE AllWISE MOTION SURVEY

ABSTRACT We present optical and near-infrared spectroscopy of WISEA J061543.91−124726.8, which we rediscovered as a high motion object in the AllWISE survey. The spectra of this object are unusual; while the red optical (λ > 7000 Å) and near-infrared spectra exhibit characteristic TiO, VO, and H2O bands of a late-M dwarf, the blue portion of its optical spectrum shows a significant excess of emission relative to late-M-type templates. The excess emission is relatively featureless, with the exception of a prominent and very broad Na i D doublet. We find that no single, ordinary star can reproduce these spectral characteristics. The most likely explanation is an unresolved binary system of an M7 dwarf and a cool white dwarf. The flux of a cool white dwarf drops in the optical red and near-infrared, due to collision-induced absorption, thus allowing the flux of a late-M dwarf to show through. This scenario, however, does not explain the Na D feature, which is unlike that of any known white dwarf, but which could perhaps be explained via unusual abundance or pressure conditions.

Comment on “Evolution of high-pressure mafic granulites and pelitic gneisses from NE Madagascar: Tectonic implications”. Tectonophysics, 662, 219–242 (2015) by Ishwar-Kumar et al.

Determining the possible tectonic regimes active during the Neoproterozoic is crucial for the knowledge of the evolution of the super-continent Gondwana. In Madagascar, that occupies a key position in Gondwana, there is an on-going debate regarding the location of possible suture zones and the implications in terms of paleo-geography. Recognizing high-pressure to ultra-high pressure conditions in mafic rocks is commonly viewed as a strong argument for paleo-subduction zones. Ishwar-Kumar et al. (2015) report unusual high pressure conditions (24kbar) in Neoproterozoic to Cambrian rocks from North-Central Madagascar (Andriamena Complex). They propose a geodynamic model in which exhumation of the high pressure terranes from up to ~80km to ~40km occurred via vertical extrusion during the collision of various crustal blocks after subduction and closure of an oceanic domain during the formation of Gondwana in the late Neoproterozoic to Cambrian. We question this model and in particular the (ultra-)high pressure conditions reported, because their estimation is based on a misinterpretation of the petrography and inaccurate thermodynamic modeling for the crucial metabasite sample. The authors suggest that garnet-quartz coronas around orthopyroxene and ilmenite coexist with clinopyroxene. The postulated garnet-clinopyroxene-quartz assemblage is interpreted to document an eclogite facies overprint. However, the presence of abundant plagioclase in the sample and the lack of high jadeite content in clinopyroxene clearly refute the postulated eclogite facies conditions. According to the presented photographs clinopyroxene is part of the rock matrix. We therefore suggest that the sample represents a common two-pyroxene granulite, formed at mid- to low-pressure granulite facies conditions of >700°C and <6kbar, consistent with PT data of former studies for the Andriamena Complex. Garnet-quartz-bearing coronas produced at the expense of the granulite-facies assemblage could have been produced during isobaric cooling. Although a subduction zone may have been active during this period of time in Madagascar, this interpretation is not justified by the data presented by Ishwar-Kumar et al. (2015).

Lattice dynamics and high-pressure Raman scattering studies of CoTeMoO6 crystal

We have performed lattice dynamics calculations for CoTeMoO6 telluromolybdate and proposed assignment of modes to respective vibrations of atoms in the unit cell. We have also performed pressure-dependent Raman scattering studies that revealed unusual negative pressure dependence of the highest wavenumber modes. We provide explanation of this behavior based on strongly layered nature of CoTeMoO6 crystal. High-pressure data also indicate weak compressibility of the TeO4 groups associated with large changes in the MoOTe bridges. The spectra remain qualitatively the same up to 6.3GPa but some very subtle changes in the spectra have been observed near 2.6–3.0GPa that might indicate onset of a very subtle structural transformation in the studied crystal.

Unusual idiopathic normal pressure hydrocephalus patient with marked asymmetric and upper body parkinsonism

Asymmetry of parkinsonian symptoms is strong evidence toward the diagnosis of Parkinson's disease (PD). Lower body parkinsonism is characteristic in idiopathic normal pressure hydrocephalus (INPH). We report an unusual INPH patient with marked asymmetric and upper body parkinsonism. An 83-year-old man presented with gait impairment and asymmetric clumsiness of movement. According to the Unified Parkinson's Disease Rating Scale (UPDRS), the motor subscore was 12 in the left limb and 8 in the right. The score was 14 for both the upper and lower body. After the cerebrospinal fluid tap test (CSFTT), he showed marked improvement in the upper body score. A loss of asymmetry of parkinsonian signs, with greater improvement in the left limb, was presented. Fluorinated N-3-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)-nortropane (F-18 FP-CIT) positron emission tomography (PET) imaging was normal. In the differential diagnosis of elderly patients presenting with parkinsonism compatible with PD, we might need to consider a diagnosis of INPH.

Quantum Critical Behavior and Superconductivity in new multi-site Cerium Heavy Fermion Compound Ce3PtIn11

We discuss the results of thermodynamic and transport measurements at ambient and under hydrostatic pressure of the recently discovered heavy fermion superconductor Ce3PtIn11. At p = 0 superconductivity emerges in the complex antiferromagnetic state below Tc = 0.32 K. Both phenomena coexist in a wide range of the p — T phase diagram. The critical pressure where TN → 0 and Tc is maximum equals pc = 1.3 GPa. Here, the resistivity follows ρ(T) α Tn with n = 0.90±0.05 suggesting a local moment-type of quantum critical point. The presence of a maximum structure in the susceptibility and the unusual pressure dependence of Tc hint to an understanding of properties of Ce3PtIn11 in the view of distinct different Kondo screened sublattices. Therefore, we analyze the magnetic entropy Smag within the spin-1/2 Kondo model while accounting for the fact that Ce3PtIn11 unit cell possesses two inequivalent Ce-sites, Ce1 and Ce2. We employ an extreme case scenario of non-interacting sublattices where the Ce1-sublattice is paramagnetic and only Ce2-sublattice orders magnetically and discussed its consequences.

CFD Modelling and Validation of Newtonian and Non-Newtonian Fluids in Curved Conduits

CFD modelling of drag reduction agents (also called Flow Improvers) polymer additives dissolved in a newtonian solvent (UTP tap Water) was carried out in a curved conduit, A 7 equation Reynolds stress set of equations was used to simulate this flow. The purpose of this simulation is validate experimental results that show unusual pressure drop behaviour. CFD experiments show that there is pressure build-up near the end of the curved conduit due to severe centrifugal forces produced by the fluid, confirming the validity of the experimental results.

The Rate and Molecular Spectrum of Spontaneous Mutations in the GC-Rich Multichromosome Genome of Burkholderia cenocepacia.

Spontaneous mutations are ultimately essential for evolutionary change and are also the root cause of many diseases. However, until recently, both biological and technical barriers have prevented detailed analyses of mutation profiles, constraining our understanding of the mutation process to a few model organisms and leaving major gaps in our understanding of the role of genome content and structure on mutation. Here, we present a genome-wide view of the molecular mutation spectrum in Burkholderia cenocepacia, a clinically relevant pathogen with high %GC content and multiple chromosomes. We find that B. cenocepacia has low genome-wide mutation rates with insertion-deletion mutations biased toward deletions, consistent with the idea that deletion pressure reduces prokaryotic genome sizes. Unlike prior studies of other organisms, mutations in B. cenocepacia are not AT biased, which suggests that at least some genomes with high %GC content experience unusual base-substitution mutation pressure. Importantly, we also observe variation in both the rates and spectra of mutations among chromosomes and elevated G:C > T:A transversions in late-replicating regions. Thus, although some patterns of mutation appear to be highly conserved across cellular life, others vary between species and even between chromosomes of the same species, potentially influencing the evolution of nucleotide composition and genome architecture.

Transitions in pressure collapsed clathrate hydrates.

Type II clathrate hydrates (CHs), or ice clathrates, are inclusion compounds in which a hydrogen-bonded cage-like structure of H2O accommodates molecules of suitable size, known as "guest molecules". CHs have similar local geometrical arrangements of the hydrogen-bonded water network as ice and both are known to collapse to amorphous states on isothermal pressurization at temperatures below about 140 K. Moreover, the collapsed CH states undergo a glass, or glass-like, transition at 140 K on heating at 1 GPa, which is identical to that of collapsed ice, or high density amorphous ice. Here we use thermal conductivity and dielectric measurements to study the transition behavior of two type II CHs with tetrahydrofuran and 1,3 dioxolane, respectively, as guest molecules. After their collapsed states have been heated to well above the glass transition at 1 GPa, we find transitions corresponding to the high to low density amorphous ice transition of ice with only slightly shifted temperature-pressure (T-p) coordinates compared to those of pure water. Thus, collapsed CHs show the same transition behaviors as cold water, which provide the basis for the model that explains the unusual temperature and pressure behaviors of water's properties in terms of two distinct types of liquid water. Collapsed CHs are, however, more stable than collapsed ice and can therefore be studied in a wider T-p interval. The results suggest sluggish homogenizing and phase separation processes, which affect the transition behaviors of collapsed CHs.

Dissociation of 1,1,1-trifluoroethane is an intrinsic RRKM process: classical trajectories and successful master equation modeling.

Rate constants for thermal decomposition of 1,1,1-trifluoroethane (CH3CF3) in the high-temperature falloff region were previously reported to have an unusual pressure dependence that could not be explained by Rice-Ramsperger-Kassel-Marcus (RRKM) theory in combination with unimolecular master equation analysis. This study investigates the dynamics of the CH3CF3 dissociation and the energy transfer of CH3CF3 in collisions with Ar and Kr by classical trajectory calculations on a global potential energy surface constructed from a large number of quantum chemical calculations. The simulations showed that the ensemble-averaged CH3CF3 populations decay with single exponential profiles that have rate constants close to those predicted by RRKM theory, indicating that the microcanonical ensemble is maintained during decomposition. The trajectory calculation also indicated that a significant portion of the HF product is formed in its vibrationally excited state. Such observation motivated this study to correct some of the reported rate constants for the CH3CF3 decomposition. With the correction applied, the experimental rate constants were well reproduced by the RRKM/master equation calculation using the collisional energy transfer parameters that were also obtained from trajectory calculations. Overall, the title reaction is demonstrated to be another successful example of RRKM/master equation modeling.

Thermal decomposition of 1,1,1-trifluoroethane revisited.

1,1,1-Trifluoroethane (CH3CF3) has been frequently used as a chemical thermometer or an internal standard in shock tube studies to determine relative rates of chemical reactions. The rate constants for the thermal decomposition of CH3CF3 were recently reported to have anomalous pressure dependence in the high-temperature falloff region. In the present study, the kinetics of the CH3CF3 decomposition were reinvestigated using shock tube/laser absorption (ST/LA) spectroscopy and single-pulse shock tube (SPST) methods over the temperature range 1163-1831 K at pressures from 95 to 290 kPa. The present rate constants are 2-3 times smaller than those reported in previous single-pulse experiments performed at near high-pressure limit conditions. The recommended rate constant expression, k = 5.71 × 10(46)T(-9.341) exp(-47073 K/T) s(-1), was obtained over the temperature range 1000-1600 K with uncertainties of ±40% at temperatures below 1300 K and ±32% at 1600 K. The rate constants at the high-temperature region showed clear falloff behavior and were in good agreement with recent high-temperature experiments. The falloff rate constants could not be reproduced by a standard RRKM/master-equation model; this study provides additional evidence for the unusual pressure dependence previously reported for this reaction. Additionally, the rate constants for the decomposition of 1,1-difluoroethylene (CH2CF2) were determined over the temperature range 1650-2059 K at pressures of 100 and 205 kPa, and were reproduced by the RRKM/master-equation calculation with an average downward energy transfer of 900 cm(-1).

Prediction of natural gas flow through chokes using support vector machine algorithm

In oil and gas fields, it is a common practice to flow liquid and gas mixtures through choke valves. In general, different types of primary valves are employed to control pressure and flow rate when the producing well directs the natural gas to the processing equipment. In this case, the valve normally is affected by elevated levels of flow (or velocity) as well as solid materials suspended in the gas phase (e.g., fine sand and other debris). Both surface and subsurface chokes may be installed to regulate flow rates and to protect the porous medium and surface facilities from unusual pressure instabilities.In this study a reliable, novel, computer based predictive model using Least-Squares Support Vector Machine (LSSVM) algorithm is applied to predict choke flow coefficient in both nozzle and orifice type chokes in subsonic natural gas flow conditions. The average absolute relative deviation of the proposed model from reported data for nozzle-type and orifice-type choke are nearly 0.25% and 0.15% and the squared correlation coefficient is around 0.9961 and 0.9982 respectively.

Migration of High-Pressure Air during Gas Well Drilling in the Appalachian Basin

AbstractWe present the details of a numerical model simulating the migration of pressurized air used for pneumatic drilling of a well in an aquifer. We used an incident that occurred in West Virginia during June 2012 as a basis for making the simulations realistic. We developed a 3D conceptual model using the multipurpose model TOUGH2 to simulate the events during this incident. Input parameters for the model were obtained from field measurements, and a number of reasonable assumptions were made for other parameters. Our results showed that compressed air from a drilling well is capable of creating a high pressure gradient in groundwater at hundreds of meters from the drill hole, even if the air leakage from the drilling well occurs in a confined aquifer, and even if the leakage duration is only 2 h. Therefore, one way to prevent the pressure buildup in the surrounding aquifers is through emplacement of observation wells before drilling, which would alert the drillers to any unusual pressure buildup insid...

An Evidence of Esophageal Decompensation in Patients With Achalasia in the View of Its Subtype: A Retrospective Study

Background/AimsAchalasia is a primary motility disorder of esophagus. Many parameters represent esophageal function and morphologic changes, but their interrelationship is not yet established. We hypothesized that esophageal body would need to generate unusual pressure to empty the food bolus through the non-relaxing lower esophageal sphincter in patients with achalasia; therefore, higher is the residual lower esophageal sphincter pressure, greater would be the contraction pressure in the esophageal body in these patients. To verify the hypothesis, correlations among parameters from esophageal manometry, esophagography and esophageal transit study had been investigated.MethodsA retrospective review of 34 patients was conducted. Resting lower esophageal sphincter pressure and contraction pressure of esophageal body were obtained from conventional esophageal manometry. Diameter of esophageal body was measured from barium column under esophagography. Radionuclide imaging was performed to assess the esophageal transit, designated as R30, which was the residual radioactivity at 30 seconds after ingesting radioactive isotope.ResultsIn vigorous achalasia group, contraction pressure of esophageal body was negatively correlated to dilated diameter of esophageal body (P = 0.025, correlation coefficient = -0.596). Esophageal transit was more delayed as dimensions of esophageal body increased in classic achalasia group (P = 0.039, correlation coefficient = 0.627).ConclusionsDiameter of esophageal body in classic achalasia was relatively wider than that of vigorous achalasia group and the degree of delayed esophageal transit was proportionate to the luminal widening. Patients with vigorous achalasia had narrower esophageal lumen and relatively shorter transit time than that of classic achalasia group. Proper peristalsis is not present in achalasia patients but remaining neuromuscular activity in vigorous achalasia patients might have caused the luminal narrowing and shorter transit time.

Molecular-level Insight into Unusual Low Pressure CO2 Affinity in Pillared Metal–Organic Frameworks

Fundamental insight into how low pressure adsorption properties are affected by chemical functionalization is critical to the development of next-generation porous materials for postcombustion CO2 capture. In this work, we present a systematic approach to understanding low pressure CO2 affinity in isostructural metal-organic frameworks (MOFs) using molecular simulations and apply it to obtain quantitative, molecular-level insight into interesting experimental low pressure adsorption trends in a series of pillared MOFs. Our experimental results show that increasing the number of nonpolar functional groups on the benzene dicarboxylate (BDC) linker in the pillared DMOF-1 [Zn2(BDC)2(DABCO)] structure is an effective way to tune the CO2 Henry's coefficient in this isostructural series. These findings are contrary to the common scenario where polar functional groups induce the greatest increase in low pressure affinity through polarization of the CO2 molecule. Instead, MOFs in this isostructural series containing nitro, hydroxyl, fluorine, chlorine, and bromine functional groups result in little increase to the low pressure CO2 affinity. Strong agreement between simulated and experimental Henry's coefficient values is obtained from simulations on representative structures, and a powerful yet simple approach involving the analysis of the simulated heats of adsorption, adsorbate density distributions, and minimum energy 0 K binding sites is presented to elucidate the intermolecular interactions governing these interesting trends. Through a combined experimental and simulation approach, we demonstrate how subtle, structure-specific differences in CO2 affinity induced by functionalization can be understood at the molecular-level through classical simulations. This work also illustrates how structure-property relationships resulting from chemical functionalization can be very specific to the topology and electrostatic environment in the structure of interest. Given the excellent agreement between experiments and simulation, predicted CO2 selectivities over N2, CH4, and CO are also investigated to demonstrate that methyl groups also provide the greatest increase in CO2 selectivity relative to the other functional groups. These results indicate that methyl ligand functionalization may be a promising approach for creating both water stable and CO2 selective variations of other MOFs for various industrial applications.

Analysis of 2010-flood causes, nature and magnitude in the Khyber Pakhtunkhwa, Pakistan

This article attempts to analyse the nature, magnitude and causes of 2010 disastrous flood that seriously affected the province of Khyber Pakhtunkhwa (KPK), Pakistan. Pakistan is famous for its summer floods, but the flood of 2010 is considered to be the century’s worst. It has broken all the previous records in terms of discharge, damages and amount of rainfall occurred. Most of the meteorological stations have received rainfall above normal. Data for this study were collected both from primary and secondary sources. A total 150 questionnaires were filled in from the flood victims. However, secondary data were obtained from the Pakistan Meteorology Department, Flood Forecasting and Warning Centre, Federal Flood Commission, Provincial Disaster Management Authority, National Disaster Management Authority, Surface Water Hydrology Department and Provincial Irrigation and Drainage Authority. The analysis reveals that heavy and prolonged rainfall for four consecutive days (27–30 July) was the major cause of 2010-flood. In addition to this, the development of unusual low pressure zone over the northern Pakistan, aggradations of river bed, rapid deforestation, ponding back of river by motorway, blocking of bridges by tree trunks and subsequent bursting of temporary dams have played their role in causing the disastrous flood in almost all the rivers of KPK. This has inflicted terrible damages to human lives, standing crops, housing, infrastructure and other properties.

High Pressure Structural Studies on Rare-Earth Sesquioxides

The Rare-Earth sesquioxides (RE2O3) exhibit interesting physical and chemical properties. Some of these oxides have tremendous technological applications. At ambient conditions, the RE2O3 systems exist in three polymorphic forms, namely: hexagonal A- type, monoclinic B- type, and cubic C- type. The structural stability of three RE2O3 systems: RE = Gd, Ho, Tm and the Tb4O7 system have been studied under high pressure. All the four systems exhibited interesting pressure induced phase transitions. Gd2O3 exhibited C-A transition at ∼ 12 GPa, whereas Ho2O3 and Tm2O3 exhibited C-B transition at pressures of 9.5 and 7 GPa respectively. Tb4O7 transformed from its cubic fluorite structure to probably the cotunnite phase at a relatively higher pressure of 27 GPa. The unusual large pressure stability of Tb4O7 was attributed to the presence of Tb4+ ions. The bulk moduli show systematic increase with higher cations, probably due to the enhanced influence of the 4f electron states and increased nature of covalency. However, the mechanisms of the structural transitions C-B-A with increased pressure and increased cation radii are yet to be understood.