Opposite Pressure Research Articles

Experimental investigation of the influence of drainage condition on change in saturation of sheared sand

This paper investigates the validity of the interpretation of results from testing saturated axisymmetric triaxial compression (ATC) sand specimens utilizing 3D synchrotron micro-computed tomography (SMT) to probe localized events that are completely missed or misinterpreted when analyzing ATC measurements based on global standard measurements. Drained and undrained experiments were conducted at low and high back pressures (BPs) coupled with multiple in situ 3D-SMT to acquire high-resolution scans of the specimens at different axial strains. Specimens tested under low BP exhibited a large pore air volume change, which was not detected by the pump system that represents standard volume measurement. The increase in air volume caused a significant reduction in the degree of saturation leading to a possible transition from saturated to partially saturated constitutive behavior. Undrained experiments exhibited a significant volume change contrary to the assumption of negligible volumetric strain for saturated undrained experiments. Air bubbles within the shear band for drained and undrained low BP specimens showed opposite capillary pressure responses, increased for drained and decreased for undrained cases, due to the variation in the mechanism by which each of the two experiments predominantly counters the volume expansion within the shear band.

Seismicity near Mayotte explained by interacting magma bodies: Insights from numerical modeling

Mayotte island experienced a large volcanic eruption 50 km offshore in 2018–2021, creating the submarine volcano “Fani Maoré”. The eruption was accompanied by intense seismicity at mantle depths (20–45 km), divided into a “proximal” and a “distal” cluster centered 10 and 30 km east from the island, respectively. Previous studies suggest that two separate magma reservoirs may lie at the top and bottom of the proximal cluster. Here, we assess whether two reservoirs are a mechanically viable explanation for the proximal cluster's truncated conical shape. We developed finite-element models of pressurized magma reservoirs in a 2D axisymmetric domain, modeling the reservoirs as compliant elastic ellipsoids embedded in an elastoplastic host rock. We find that, at these depths, extremely low friction is required to generate failure at realistically low reservoir pressures. This implies in turn that mechanical weakening must occur at these depths. The weakening could be induced by fractures or pore fluid overpressure in the volcanic system. We find that two superimposed reservoirs can generate a plastic domain between them, if they are spatially close enough. Several reservoir geometries (from spherical to sill-like) are plausible. A conical fracture domain is more likely to appear for reservoirs with opposite pressure loads (i.e. one inflating, one deflating). Given the geometrical match with the proximal seismicity cluster at Mayotte, we suggest that the shallower (Moho-depth) reservoir is inflating, creating a potential hazard for Mayotte island.

The effects of Stefan flow on the flow surrounding two closely spaced particles

The aim of the work was to study the effects of neighboring particles with uniform Stefan flow in particle–fluid flows. Particle-resolved numerical simulations were carried out for particles emitting a uniform Stefan flow into the bulk fluid. The bulk fluid was uniform and isothermal. The Stefan flow volume emitted from the two particles is equal, such that it represents idealized conditions of reacting particles. Particles were located in tandem arrangement and particle distances were varied between 1.1 and 10 particle diameters (1.1≤L/D≤10). Three particle Reynolds numbers were considered during the simulations (Re=2.3,7 and 14), which is similar to our previous studies. Three Stefan flow velocities were also considered during simulations to represent inward, outward, and no Stefan flow. The drag coefficient of the particles without Stefan flow showed that the results fit with previous studies on neighbor particle effects. When the particle distance is greater than 2.5 diameters (L/D>2.5), the effects of Stefan flow and neighboring particles are independent of each other. I.e. an outward Stefan flow decreases the drag coefficient (CD) while an inward Stefan flow increases it and the upstream particle experience a higher CD than the downstream particle. When L/D≤2.5, the effect of Stefan flow is dominant, such that equal and opposite pressure forces act on the particles, resulting in a repelling force between the two neighboring particles. The pressure force showed a large increase compared to the viscous force at these distances. The effect of Stefan flow is weakened at higher Reynolds numbers. A model was developed for the calculation of the drag coefficient. The model, which reproduce the results from the numerical simulations presented above, is a product of independent models that describe the effects of both neighboring particles and two distinguished effects of the Stefan flow.

Creep and ageing of granular materials under isotropic pressure

Single- and multi-stage isotropic creep tests including bender element and acoustic emission measurements are carried out to investigate the relationship between ageing and creep in dense silica sand. In the considered pressure range, the experimental results show an inversely proportional relationship between ageing and creep: the small-strain shear modulus increases with decreasing isotropic pressure,, while the axial creep strain and the acoustic emissions show the opposite pressure dependence. In the multi-stage creep test, the small-strain shear modulus increases monotonically, while the rates of axial strain, number of acoustic emissions and small-strain shear modulus decrease with time according to a power law. In the single-stage creep tests, the ageing and creep indicators initially evolve as in the multi-stage creep test, but then the small-strain shear modulus reaches a peak value and decreases with time thereafter. At the same time, the rates of axial strain, number of acoustic emissions and small-strain shear modulus deviate from the power law. A conceptual model assuming a time-dependent behaviour of the normal and shear forces at the particle contacts in order to explain the experimental observations qualitatively is proposed. Accordingly, an increase in small-strain shear modulus results from homogenisation of the force chains, while a decrease in small-strain shear modulus results from a temporary formation followed by a time-delayed collapse of strong force chains.

Asymmetric interactions between barley yellow dwarf virus -PAV and wheat dwarf virus in wheat.

The deciphering of the epidemiology of a plant virus has long been focused on the study of interactions between partners of one pathosystem. However, plants are exposed to numerous viruses which lead to frequent co-infection scenarios. This can change characteristics of virus-vector-host interactions and could impact the epidemiology of viral diseases. Barley yellow dwarf virus-PAV (BYDV-PAV; species: Luteovirus pavhordei; genus Luteovirus), wheat dwarf virus (WDV; genus Mastrevirus) and their respective vectors (BYDV-PAV: e.g. Rhopalosiphum padi and WDV: Psammotettix alienus) are commonly found in cereal fields. Wheat plants co-infected with BYDV-PAV and WDV have been reported from field surveys, although epidemiological outcomes of BYDV-PAV - WDV interactions in planta have not yet been studied. Experiments were carried out to evaluate and compare, through different competition scenarios (i.e. single- and co- (simultaneous and sequential) inoculations), the efficiency of BYDV-PAV and WDV to infect, to accumulate in and to be spread between wheat plants. Moreover, the impact of competition scenarios on the biological parameters of these two viruses was evaluated at different stages of the infection and with plants at different ages at inoculation. Results showed i) that these viruses achieve their infection cycle and their plant-to-plant transmission with different efficiencies and ii) BYDV-PAV - WDV interactions lead to different phenotypes ranging from antagonism to synergism. Finally, when these two viruses share a host, the nature and strength of virus-virus interactions varied depending on the order of virus arrival, stages of the infection cycle and plant age at inoculation. Precisely, the introduction (i.e. co- and sequential inoculation) and infection process (i.e. virus accumulation) of BYDV-PAV in a wheat benefit from the presence of WDV. For the latter, the sympatry with BYDV-PAV exerts opposite pressure on parameters involved in virus introduction (i.e. benefit during sequential inoculation) and spread (i.e. lower transmission efficiency and virus accumulation in co-infected plants). In the context of increased potential exposure of crops to insect vectors, this study participates in a better understanding of the impact of BYDV-PAV and WDV co-infections on biological and ecological parameters of the diseases induced by these viruses.

Molecular perspectives of interfacial properties of the hydrogen+water mixture in contact with silica or kerogen

Interfacial behaviours in multiphase systems containing H2 are crucial to underground H2 storage but are not well understood. Molecular dynamics simulations were carried out to investigate interfacial properties of the H2+H2O and H2+H2O+silica/kerogen systems over a broad range of temperatures (298 - 523 K) and pressures (1 - 160 MPa). The combination of the H2 model with the INTERFACE force field and TIP4P/2005 H2O model can accurately predict the experimental interfacial tensions (IFTs) of the H2+H2O mixture. The IFTs from simulations are also in accordance with predictions from density gradient theory combined with the PC-SAFT equation of state. In general, the IFT decreases with pressure and temperature. However, at relatively high temperatures and pressures, the IFTs increase with pressure. The opposite pressure influence on IFTs can be explained by the inversion of the sign of the relative adsorption of H2. The H2 enrichment in the interfacial regions was identified in density distributions. Meanwhile, the behaviours of contact angles (CAs) in the H2+H2O+silica system are noticeably different from those in the H2+H2O+kerogen system. The H2O CAs for the H2+H2O+silica and H2+H2O+kerogen systems increase with pressure and decrease with temperature. However, the influence of temperature and pressure on these CAs is less pronounced for the H2+H2O+silica system at low temperatures. The behaviours of CAs were understood based on the variations of IFTs in the H2+H2O system (fluid-fluid interaction) and adhesion tensions (fluid-solid interaction). Furthermore, the analysis of the atomic density distributions indicates that the presence of H2 in between the H2O and the silica/kerogen is almost negligible. Nevertheless, the adsorption of H2O on the silica outside the H2O is strong, while less H2O adsorption is seen on the kerogen.

Casing Leak Repair Allows Continued Hydraulic Fracturing

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 212933, “Casing Leak Repair To Continue Hydraulic Fracture Stimulation,” by Gaston Oscar Ciminari, Gonzalo Cabo, SPE, and German Rimondi, Pluspetrol, et al. The paper has not been peer reviewed. _ The authors introduce a successful alternative for repairing casing failures on an unconventional well that allows hydraulic fracture continuity to accomplish the original fracturing plan, considering well-integrity conditions throughout the entirety of well production life as the main intervention objective. The resulting well production was higher than the expected estimated ultimate recovery (EUR) for the landing zone. Introduction In December 2020, during the execution of hydraulic fracturing on a three-well pad in the Vaca Muerta unconventional shale reservoir, an annular communication suddenly occurred in one of the wells. This event took place during the execution of the ninth fracturing stage of 33 planned. After a thorough pressure analysis of this event and verification that all pressure barriers were correct and in place, it was decided to stop fracturing treatments in this well and complete pending fracturing stages in the other two wells of the pad until the problem was well understood and a solution was found. Diagnostics The initial good condition of the well barrier was verified by a positive casing-integrity test (CIT) at 13,000 psi before the first fracturing pump. Maximum treatment pressure was kept under the CIT pressure, with an acceptable safety factor margin maintaining the well with annular communication, and was continuously pressure monitored. Once the fracturing fleet finished the intervention and left the pad, the engineering focus of the completion was oriented to determine the location and geometric characteristics of the casing leak. It was decided to start from the simplest to most-complex diagnostics interventions. The diagnostics interventions, and their results, are detailed in the complete paper. A bullheading pumping test was executed, and an increase in Section B pressure was observed. This showed clear communication between both sections. During circulation tests, it was observed that, by reducing pressure in Section B, Section A pressure response followed the pressure trend; opposite pressure changes in Section A, however, did not reflect on Section B pressure changes. Based on flow-test behavior, it was believed that a casing mechanical failure with a flow area of 0.044 in.2, equivalent to a 0.23-in. orifice, was the reason for the annular communication. With the aid of a coiled tubing (CT) unit and a bottomhole assembly (BHA) principally conformed with a multiple-set mechanical packer, it was possible to apply testing pressure below and above the packer seals at different depths to confirm the casing-leak position. A unique failure was located in the zone between 998 and 1002 m. A casing joint was located at 999.5 m; thus, it was assumed that a mechanical problem existed on this casing-joint connection. A wireline BHA composed of an injection-logging tool and a temperature sensor was used to reduce the zone of uncertainty. As a result of this log, the failure zone was located between 999.4 and 1000.4 m. The failure evidently was near the joint but not in it. Immediately after well-fluid changeout, the real-time downhole camera was run on wireline and showed what appeared to be a small hole 1 ft over the casing joint.

Opposite pressure impact on electron–phonon coupling in Eu2+ and Ce3+ doped AlN

This paper analyzes the influence of pressure on electron–lattice interactions in the 5d excited states of Ce3+ and Eu2+ in the AlN host based on pressure-dependent photoluminescence and photoluminescence excitation spectra.

Simultaneous Positive and Negative Pressure Control Using Disturbance Observer Compensating Coupled Disturbance Dynamics

This letter introduces a simultaneous positive and negative pressure controller for a pneumatic pump. For precise position or force control of the pneumatic soft actuator, the pressure from the source has to be regulated. When the positive and negative pressures are regulated, coupled dynamics caused by the pressure change affect the controller performance. In other words, changes in the positive or negative pressure concurrently act as disturbances in the opposite pressure controller. Therefore, a disturbance observer is designed to compensate for the coupled pressure dynamics. A nominal model of the system is obtained based on the output-error model used in the MATLAB System Identification Toolbox. A simulation study is also performed to design a controller when the demand for the positive and negative pressures varies. Finally, a verification of the effectiveness of the controller is done through a series of experiments. In the step response test, the maximum pressure error of the positive and negative pressure was reduced from 0.159 to 0.152 kPa and from 0.3297 to 0.2334 kPa with the disturbance observer. Where positive and negative pressures change at the same time, the root mean square of the positive and negative pressure error decreased from 0.9701 to 0.4457 kPa and from 0.9848 to 0.4634 kPa applying the proposed pressure controller.

Study of interfacial properties of water + methane + oil three-phase systems by a simple molecular simulation protocol

A straightforward molecular simulation protocol has been proposed to study the interfacial properties of the three-phase fluid systems. With this protocol, the interfctcial tension (IFT) can be calculated based on the pressure tensor of the entire simulation box of the two-phase systems split from the three-phase system without calculating the debatable pressure tensor profile. Water + methane + oil (decane, hexadecane, and toluene) three-phase systems was studied at different temperatures (323–423 K) and pressures (up to around 20 MPa). Reasonable agreement was found among the results obtained from molecular simulation, density gradient theory with the cubic-plus-association equation of state, and available experimental data in the literature. The IFT of the aqueous phase + vapor phase in the three-phase systems is smaller than the IFT in water + methane two-phase systems. Importantly, the reduction of IFT of aqueous phase + vapor phase in the three-phase systems containing decane or hexadecane is moderate while that in the three-phase systems containing toluene is significant, which can be explained by the stronger enrichment of toluene in the interfacial region in contrast to that of decane or hexadecane. Meanwhile, methane accumulates in the interfacial region of the aqueous phase + decane/hexadecane-rich phase in the three-phase systems, which causes the reduction of IFT with pressure while the opposite pressure effect was reported in the water + decane/hexadecane two-phase systems. The interfacial properties of the oil-rich phase + vapor phase in the three-phase systems are hardly affected by water due to the small amount of dissolved water. Furthermore, the calculated spreading coefficient of different types of oil in contact with water + methane under three-phase conditions follows this order: toluene > decane > hexadecane.

Pressure-assisted electrokinetic injection for the stacking of biogenic amines gives enhancement factor up to 1000 in CE with UV detection.

Pressure-assisted electrokinetic injection (PAEKI) was applied for stacking of positively charged biogenic amines (BAs) to improve the sensitivity of capillary electrophoresis (CE). It is well known that the essential step for PAEKI is finding a stationary state of the running buffer such that the movement of the running buffer due to electroosmotic flow (EOF) is counterbalanced by external pressure in the opposite direction of the EOF under a given electric field. In order to find the balance point systematically and integrally, we studied the velocity of the whole BGE in the capillary by the impetus of opposite direction pressure (-0.1 to -0.6 psi), and the velocity of EOF with different voltages. According to the two sets of linear data, the EOF of CE coupled with PAEKI could be counterbalanced at the opposite direction pressure (-0.1 psi) and voltage (7.8 kV). In this study, the injection time was extended up to 0.35 min for all BAs and 0.70 min for the direct ultraviolet (UV) detection of BAs. Compared with hydrodynamic injection (HDI), the enrichment factors for sample injection times of 0.35 min and 0.70 min were 480-fold and 970-fold, respectively. The limits of detection (LODs) (S/N = 3) of indirect and direct UV detection were respectively 8.7-24.3 nmol L-1 and 0.4-4.5 nmol L-1, which reaches the sensitivity of high-performance liquid chromatography-mass spectrophotometry (HPLC-MS). With appropriate sample dilution, PAEKI can be used in the analysis of BAs in chicken.

Pressure-driven evolution of structural distortions in RCrO3 perovskites: The curious case of LaCrO3

The pressure dependence of octahedral distortions in rare-earth (R) orthochromites (RCrO3) has been studied using Raman scattering technique to probe the origin of the structural transition from orthorhombic Pnma to rhombohedral R3‾c phase in LaCrO3. The pressure-induced changes in the octahedral tilt modes demonstrate that tilt distortion is suppressed in LaCrO3 and is enhanced in the remaining members of the RCrO3 family. This crossover between the two opposite pressure behaviours occurs at a critical R-ion radius of 1.20 Å. We attempt to establish the relationship between this unusual crossover and compressibility at Cr- and R-sites by probing Raman phonon modes sensitive to the mean bond strength of Cr–O, and R–O, respectively. Finally, we study the bond length splitting of both CrO6 and RO12 polyhedra to ascertain the role of polyhedral self-distortion in determining the pressure dependent structural transition in the orthochromites.

High-pressure insulating phase of Mo4O11 with collapsed volume

We investigated the effect of pressure on the crystal structure and transport properties of the Magn\'eli phase \ensuremath{\eta}-${\mathrm{Mo}}_{4}{\mathrm{O}}_{11}$, which at ambient pressure undergoes two successive charge-density-wave (CDW) transitions at ${T}_{\mathrm{CDW}\text{\ensuremath{-}}1}\ensuremath{\approx}105\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{CDW}\text{\ensuremath{-}}2}\ensuremath{\approx}30\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, respectively. We find that \ensuremath{\eta}-${\mathrm{Mo}}_{4}{\mathrm{O}}_{11}$ exhibits a structural phase transition from the low-pressure monoclinic $P{2}_{1}/a$ phase to a high-pressure $P{2}_{1}$ phase at ${P}_{c}\ensuremath{\approx}3.5\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$. Around ${P}_{\mathrm{c}}$, the lattice parameters experience a sudden change with a large volume collapse of $\mathrm{\ensuremath{\Delta}}V/V=\ensuremath{-}8.1%$, while the room-temperature resistivity exhibits a sudden jump by two orders of magnitude, signaling a pressure-induced metal-to-insulator transition. For $P<{P}_{c}$, the high-pressure resistivity measurements revealed opposite pressure dependences of these two CDW transitions, i.e., ${T}_{\mathrm{CDW}\text{\ensuremath{-}}1}$ is enhanced gradually to \ensuremath{\sim}130 K while ${T}_{\mathrm{CDW}\text{\ensuremath{-}}2}$ is almost suppressed completely by the application of 2.6 GPa pressure. For $P\ensuremath{\ge}{P}_{c}$, the temperature dependence of resistivity changes to an insulating-like behavior, but the activation energy is reduced gradually upon further increasing pressure. We have rationalized the insulating ground state of the high-pressure phase in terms of the structural modifications and charge redistribution based on the refinement of single-crystal x-ray diffraction data at 8.9 GPa.

Dual attenuation peaks revealing mesoscopic and microscopic fluid flow in partially oil-saturated Fontainebleau sandstones

SUMMARY We conducted stress–strain oscillation experiments on dry and partially oil-saturated Fontainebleau sandstone samples over the 1–2000 Hz band at different confining pressures to investigate the wave-induced fluid flow (WIFF) at mesoscopic and microscopic scales and their interaction. Three tested rock samples have similar porosity between 6 and 7 per cent and were partially saturated to different degrees with different oils. The measurement results exhibit a single or two attenuation peaks that are affected by the saturation degree, oil viscosity and confining pressure. One peak, exhibited by all samples, shifts to lower frequencies with increasing pressure, and is mainly attributed to grain contact- or microcrack-related squirt flow based on modelling of its characteristics and comparison with other experiment results for sandstones. The other peak is present at smaller frequencies and shifts to higher frequencies as the confining pressure increases, showing an opposite pressure dependence. This contrast is interpreted as the result of fluid flow patterns at different scales. We developed a dual-scale fluid flow model by incorporating the squirt flow effect into the patchy saturation model, which accounts for the interaction of WIFFs at microscopic and mesoscopic scales. This model provides a reasonable interpretation of the measurement results. Our broad-frequency-band measurements give physical evidence of WIFFs co-existing at two different scales, and combining with modelling results, it suggests that the WIFF mechanisms, related to pore microstructure and fluid distribution, interplay with each other and jointly control seismic attenuation and dispersion at reservoir conditions. These observations and modelling results are useful for quantitative seismic interpretation and reservoir characterization, specifically they have potential applications in time-lapse seismic analysis, fluid prediction and reservoir monitoring.

The opposite pressure dependence of electron temperature with respect to O2/Ar mixing ratio in an inductively coupled plasma

To observe the evolution of electron temperature and electron density when varying gas mixing ratio and pressure, the measurement of electron energy probability functions (EEPFs) and a kinetic simulation are performed in an O2/Ar inductively coupled plasma. When O2 gas is diluted to pure Ar plasma, the electron density significantly drops regardless of gas pressures and the reduction of electron density increases with gas pressure. This sudden drop of plasma density is due to various inelastic collisions between electrons and O2 molecules. However, the trend of electron temperature variation with respect to the ratio of O2 and Ar is opposite at low and high pressures. At low pressure (5 mTorr), the electron temperature decreases with the addition of O2 up to a 10% O2 ratio. With further addition of O2, the electron temperature increases gradually. On the other hand, at high pressures (25 and 80 mTorr), the electron temperature rises with addition of O2 up to a 10%–20% O2 ratio and then falls gradually with further addition of O2. Simulations show a similar variation of EEPFs to the EEPFs from experiments. In addition, we measured the EEPFs along axial positions and the variation of electron temperature with respect to the ratio of O2 and Ar is opposite at low and high pressures, regardless of spatial positions. This result indicates that the opposite trend of electron temperature variation is mainly affected by the gas mixing ratio and gas pressure.

Deprojecting galaxy-cluster cold fronts: evidence for bulk, magnetized spiral flows

ABSTRACT Tangential discontinuities known as cold fronts (CFs) are abundant in groups and clusters of galaxies (GCs). The relaxed, spiral-type CFs were initially thought to be isobaric, but a significant, $10{{\ \rm per\ cent}}$–$20{{\ \rm per\ cent}}$ jump in the thermal pressure Pt was reported when deprojected CFs were stacked, interpreted as missing Pt below the CFs (i.e. at smaller radii r) due to a locally enhanced non-thermal pressure Pnt. We report a significant (∼4.3σ) deprojected jump in Pt across a single sharp CF in the Centaurus cluster. Additional seven CFs are deprojected in the GCs A2029, A2142, A2204, and Centaurus, all found to be consistent (stacked: ∼1.9σ) with similar pressure jumps. Combining our sample with high quality deprojected CFs from the literature indicates pressure jumps at significance levels ranging between 2.7σ and 5.0σ, depending on assumptions. Our nominal results are consistent with Pnt ≃ (0.1–0.3)Pt just below the CF. We test different deprojection and analysis methods to confirm that our results are robust, and show that without careful deprojection, an opposite pressure trend may incorrectly be inferred. Analysing all available deprojected data, we also find: (i) small variations around the mean density and temperature CF contrast q within each GC, monotonically increasing with the GC mass M200 as $q\propto M_{200}^{0.23\pm 0.04}$; (ii) hydrostatic mass discontinuities indicating fast bulk tangential flows below all deprojected CFs, with a mean Mach number ∼0.76; and (iii) the newly deprojected CFs are consistent (stacked: ∼2.9σ) with a $1.25^{+0.09}_{-0.08}$ metallicity drop across the CF. These findings suggest that GCs quite generally harbour extended spiral flows.

Migration flows in the European Union - perspectives on the integration of the migrants

The consequences of the EU flows of migration recorded before the pandemic COVID - 19 indicated different expectations for the destination countries based on the need to harmonize two opposite European pressure vectors: one vector is to reduce the negative demographic trends and the other is to create better conditions for all persons to participate to social security and welfare mechanism. Adoption of the rates of migrants reflected a mechanism that requires deepening and reconsidering the dimensions of the social and economic inclusion integrative process of the migrants. Thus, given the diversity of the various approaches at the European level to achieve a balance in demographic policies perspective the article highlights the costs and benefits of an endurance process that aims inclusion of migrants at the local level. Complementary, the social and economic inclusion of migrants is a significant challenge for the Member States of the European Union, meaning that the article analyzes the importance of different indicators favorable to positively integrate the migrants. In this respect, the article outlines the progress, the recent measures implemented and the results recorded by the destination countries which are targeted by the migration flows and the best practices recorded so far. It also summarizes the main directions of valorization and dissemination of policies, strategies, and measures taken for the integration of the migrants in the European Union Member States. Social and economic inclusion at the local level of this category of vulnerable people indicates multiple challenges but also creates significant opportunities aimed to test and validate the fundamental European system articulated by the principles of justice, freedom, and security.

Finite element analysis of a composite piston for a diesel aircraft engine

The article presents calculations of thermal and mechanical loads of the piston, consisting of two parts: steel and aluminum. The calculations were made using FEM in the Abaqus software. The piston is characterized by a split construction and was equipped with a cooling oil channel. The piston will be used in an aircraft diesel engine characterized by opposite piston movement. The presented geometry of the piston is the next of the ones being developed earlier and contains preliminary assumptions as to the size and main geometrical dimensions. The thermal boundary conditions of the simulation tests assumed defined areas of heat reception surface and heating of the piston by defining a temperature map on its crown. The results of these studies were presented in the form of temperature distribution and heat flux on the surface of the tested element. The strength boundary conditions assumed a mechanical load in the form of pressure resulting from the pressure in the combustion chamber applied to the piston crown surface and the opposite pressure defined on the support at the surface of contact between the piston and the piston pin. The results of these tests were presented in the form of stress distribution on the surface of the tested element. As a result of the analyses carried out, the results constituting the basis for further modernization of the piston geometry were obtained.

Direct Numerical Simulation of Seawater Desalination Based on Ion Concentration Polarization.

The problem of water shortage needs to be solved urgently. The membrane-embedded microchannel structure based on the ion concentration polarization (ICP) desalination effect is a potential portable desalination device with low energy consumption and high efficiency. The electroosmotic flow in the microchannel of the cation exchange membrane and the desalination effect of the system are numerically analyzed. The results show that when the horizontal electric field intensity is 2 kV/m and the transmembrane voltage is 400 mV, the desalting efficiency reaches 97.3%. When the electric field strength increases to 20 kV/m, the desalination efficiency is reduced by 2%. In terms of fluid motion, under the action of the transmembrane voltage, two reverse eddy currents are formed on the surface of the membrane due to the opposite electric field and pressure difference on both sides of the membrane, forming a pumping effect. The electromotive force in the channel exhibits significant pressure-flow characteristics with a slip boundary at a speed approximately six times that of a non-membrane microchannel.

Negative and Positive Selection Pressure During Sexual Transmission of Transmitted Founder HIV-1.

Sexual transmission of HIV-1 consists of processes that exert either positive or negative selection pressure on the virus. The sum of these selection pressures lead to the transmission of only one specific HIV-1 strain, termed the transmitted founder virus. Different dendritic cell subsets are abundantly present at mucosal sites and, interestingly, these DC subsets exert opposite pressure on viral selection during sexual transmission. In this review we describe receptors and cellular compartments in DCs that are involved in HIV-1 communication leading to either viral restriction by the host or further dissemination to establish a long-lived reservoir. We discuss the current understanding of host antiretroviral restriction factors against HIV-1 and specifically against the HIV-1 transmitted founder virus. We will also discuss potential clinical implications for exploiting these intrinsic restriction factors in developing novel therapeutic targets. A better understanding of these processes might help in developing strategies against HIV-1 infections by targeting dendritic cells.