First-principles calculations using first-principles calculations have been performed to investigate the structural, elastic, and electronic properties of chalcogenide perovskite CaZrS
3
under ...different pressures. The calculated structural parameters and elastic constants show a good agreement with the other theoretical values. The details of pressure dependences of the structural parameters and elastic constants are also presented and discussed. According to our calculation, we found that the deformation resistances along the axial direction are stronger than the deformation resistances in shape. It is also found, the elastic constant C
11
is always bigger than the C
33
at the same pressure, showing that it is easier to compress along the
c
-axis than along the
a
-axis. For the calculated results of the pressure dependence of the electronic band structure, the total density of states and partial density of states of orthorhombic CaZrS
3
. We found that the band gap decreases with the pressure, which provide some additional information about these chalcopyrite semiconductors under pressure to fundamental material physics.
Persistent excessive sympathetic activation greatly contributes to the pathogenesis of chronic heart failure (CHF) and hypertension. Cardiac sympathetic afferent reflex (CSAR) is a sympathoexcitatory ...reflex with positive feedback characteristics. Humoral factors such as bradykinin, adenosine and reactive oxygen species produced in myocardium due to myocardial ischaemia stimulate cardiac sympathetic afferents and thereby reflexly increase sympathetic activity and blood pressure. The CSAR is enhanced in myocardial ischaemia, CHF and hypertension. The enhanced CSAR at least partially contributes to the sympathetic activation and pathogenesis of these diseases. Nucleus of the solitary tract (NTS), hypothalamic paraventricular nucleus (PVN) and rostral ventrolateral medulla are the most important central sites involved in the modulation and integration of the CSAR. Angiotensin II, AT1 receptors and NAD(P)H oxidase‐derived superoxide anions pathway in the PVN are mainly responsible for the enhanced CSAR in CHF and hypertension. Central angiotensin‐(1‐7), nitric oxide, endothelin, intermedin, hydrogen peroxide and several other signal molecules are involved in regulating CSAR. Blockade of the CSAR shows beneficial effects in CHF and hypertension. This review focuses on the anatomical and physiological basis of the CSAR, the interaction of CSAR with baroreflex and chemoreflex, and the role of enhanced CSAR in the pathogenesis of CHF and hypertension.
Excessive sympathetic activity contributes to the pathogenesis of hypertension and the progression of the related organ damage. Adipose afferent reflex (AAR) is a sympatho‐excitatory reflex that the ...afferent activity from white adipose tissue (WAT) increases sympathetic outflow and blood pressure. Hypothalamic paraventricular nucleus (PVN or PVH) is one of the central sites in the control of the AAR, and ionotropic glutamate receptors in the nucleus mediate the AAR. The AAR is enhanced in obesity and obesity hypertension. Enhanced WAT afferent activity and AAR contribute to the excessive sympathetic activation and hypertension in obesity. Blockage of the AAR attenuates the excessive sympathetic activity and hypertension. Leptin may be one of sensors in the WAT for the AAR, and is involved in the enhanced AAR in obesity and hypertension. This review focuses on the neuroanatomical basis and physiological functions of the AAR, and the important role of the enhanced AAR in the pathogenesis of obesity hypertension.
Stem cells play a critical role in bone regeneration. Multiple populations of skeletal stem cells have been identified in long bone, while their identity and functions in alveolar bone remain ...unclear. Here, we identified a quiescent leptin receptor–expressing (LepR+) cell population that contributed to intramembranous bone formation. Interestingly, these LepR+ cells became activated in response to tooth extraction and generated the majority of the newly formed bone in extraction sockets. In addition, genetic ablation of LepR+ cells attenuated extraction socket healing. The parabiosis experiments revealed that the LepR+ cells in the healing sockets were derived from resident tissue rather than peripheral blood circulation. Further studies on the mechanism suggested that these LepR+ cells were responsive to parathyroid hormone/parathyroid hormone 1 receptor (PTH/PTH1R) signaling. Collectively, we demonstrate that LepR+ cells, a postnatal skeletal stem cell population, are essential for alveolar bone regeneration of extraction sockets.
Clustering of earthquake magnitudes is still actively debated, compared to well-established spatial and temporal clustering. Magnitude clustering is not currently implemented in earthquake ...forecasting but would be important if larger magnitude events are more likely to be followed by similar sized events. Here we show statistically significant magnitude clustering present in many different field and laboratory catalogs at a wide range of spatial scales (mm to 1000 km). It is universal in field catalogs across fault types and tectonic/induced settings, while laboratory results are unaffected by loading protocol or rock types and show temporal stability. The absence of clustering can be imposed by a global tensile stress, although clustering still occurs when isolating to triggered event pairs or spatial patches where shear stress dominates. Magnitude clustering is most prominent at short time and distance scales and modeling indicates >20% repeating magnitudes in some cases, implying it can help to narrow physical mechanisms for seismogenesis.
Large peridotite massifs are scattered along the 1500km length of the Yarlung-Zangbo Suture Zone (southern Tibet, China), the major suture between Asia and Greater India. Diamonds occur in the ...peridotites and chromitites of several massifs, together with an extensive suite of trace phases that indicate extremely low fO sub(2) (SiC, nitrides, carbides, native elements) and/or ultrahigh pressures (UHP) (diamond, TiO sub(2) II, coesite, possible stishovite). New physical and isotopic (C, N) studies of the diamonds indicate that they are natural, crystallized in a disequilibrium, high-T environment, and spent only a short time at mantle temperatures before exhumation and cooling. These constraints are difficult to reconcile with previous models for the history of the diamond-bearing rocks. Possible evidence for metamorphism in or near the upper part of the Transition Zone includes the following: (1) chromite (in disseminated, nodular and massive chromitites) containing exsolved pyroxenes and coesite, suggesting inversion from a high-P polymorph of chromite; (2) microstructural studies suggesting that the chromitites recrystallized from fine-grained, highly deformed mixtures of wadsleyite and an octahedral polymorph of chromite; (3) a new cubic Mg-silicate, with the space group of ringwoodite but an inverse-spinel structure (all Si in octahedral coordination); (4) harzburgites with coarsely vermicular symplectites of opx + Cr-Al spinel plus or minus cpx; reconstructions suggest that these are the breakdown products of majoritic garnets, with estimated minimum pressures to>13GPa. Evidence for a shallow pre-metamorphic origin for the chromitites and peridotites includes the following: (1) trace-element data showing that the chromitites are typical of suprasubduction-zone (SSZ) chromitites formed by magma mixing or mingling, consistent with Hf-isotope data from magmatic (375Ma) zircons in the chromitites; (2) the composition of the new cubic Mg-silicate, which suggests a low-P origin as antigorite, subsequently dehydrated; (3) the peridotites themselves, which carry the trace element signature of metasomatism in an SSZ environment, a signature that must have been imposed before the incorporation of the UHP and low-fO sub(2) phases. A proposed P-T-t path involves the original formation of chromitites in mantle-wedge harzburgites, subduction of these harzburgites at c. 375Ma, residence in the upper Transition Zone for >200 Myr, and rapid exhumation at c. 170-150Ma or 130-120Ma. Os-isotope data suggest that the subducted mantle consisted of previously depleted subcontinental lithosphere, dragged down by a subducting oceanic slab. Thermomechanical modeling shows that roll-back of a (much later) subducting slab would produce a high-velocity channelized upwelling that could exhume the buoyant harzburgites (and their chromitites) from the Transition Zone in<10 Myr. This rapid upwelling, which may explain some characteristics of the diamonds, appears to have brought some massifs to the surface in forearc or back-arc basins, where they provided a basement for oceanic crust. This model can reconcile many apparently contradictory petrological and geological datasets. It also defines an important, previously unrecognized geodynamic process that may have operated along other large suture zones such as the Urals.
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•Load transfer in nanocomposites is governed by the interface strength.•Investigated the interface strength of CNT–epoxy composites using pull-out tests and MD.•The work reveals that ...the ISS is governed by the geometry of the CNT.•The cut-off distance of the L-J has a marginal effect on ISS.•Incorporation of an end cap in the pull-out test leads to a greater pull-out peaks.
In this work, we investigate the interfacial mechanical characteristics of carbon nanotube (CNT) reinforced epoxy composite using molecular dynamics (MD) simulations. The MD simulations were carried out by developing two pull-out models; namely, the displacement-load model and the velocity-load model. The second-generation force field – polymer consistent force field (PCFF) – is used in the current MD simulations. The effects of various parameters, such as epoxy density, length and diameter of a CNT, the CNT–epoxy interfacial thickness, LJ cut-off distance and capping conditions of a CNT on the interfacial mechanical characteristics have also been investigated and discussed. The results from the present pull-out model, which are validated with earlier studies, reveal that (i) the interfacial shear strength (ISS) of the CNT-reinforced epoxy composite is improved with the increase in the epoxy density, (ii) the ISS of the CNT-reinforced epoxy composite decreases with the increase in the values of length and diameter of a CNT, and the thickness of CNT–epoxy matrix interface, (iii) the LJ cut-off distance has marginal effect on the ISS and the pull-out force of CNT, and (iv) incorporation of an end cap in the simulations results high initial pull-out peaks, which well correlate with the experimental findings.
•A joint distribution model was established.•The method of combining finite element analysis and wind tunnel testing.•The combination of mixed uniform design and the GBDT algorithm.
Heliostats are a ...kind of reflection devices in solar power tower plants, and are generally arranged in flat and open areas, with independent column structure. Because the angle needs to be adjusted continuously during the use, heliostats are subject to large wind load and their support structure is prone to wind-induced fatigue. In this work, a joint distribution model was established according to the law of heliostat tracking the sun and combining with the data on wind direction and wind speed at the local meteorological station. The mixed uniform design method was used to design the research conditions, and Ansys Workbench and nCode Design Life software were coupled to combine the finite element analysis with the wind tunnel test of the heliostat structure, so as to analyze the wind-induced fatigue of the heliostat support structure. The GBDT algorithm was adopted to fit the fatigue life in typical working condition, estimate its fatigue life and analyze the law. In this work, the fatigue analysis of the heliostat support structure was conducted through a combination of mixed uniform design and finite element analysis, so as to reduce the test conditions, improve the test efficiency and estimate the fatigue life, and provide a basis for engineering design.
Crater Structure Behind Reconnection Front Huang, S. Y.; Xiong, Q. Y.; Yuan, Z. G. ...
Geophysical research letters,
16 March 2024, Letnik:
51, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Magnetic reconnection is the physical process that converts the energy from the fields to the plasmas in space, astrophysical and laboratory plasmas. The Reconnection front (RF) is the structure ...generated in the reconnection outflow region and participates in the energy release budget. Here, we first report a novel crater structure of magnetic field behind the RF, which is well supported by both the in‐situ observations from the Magnetospheric Multiscale mission and kinetic particle‐in‐cell simulations. The theoretical explanations from the simulations suggests that the formation of the crater structure is possibly due to that high‐speed outflow electron jet from inner electron diffusion region constantly strikes the RF. From another perspective, the crater structure is the continuous impact of the electron jet. Our results can establish a new understanding of the RF and energy conversion during magnetic reconnection.
Plain Language Summary
Magnetic reconnection is a natural process in space environments, astrophysical settings, and laboratories, where energy from magnetic fields is transformed into the energy of various particles. One crucial structure in this process is called the reconnection front (RF), which plays a big role in how energy is released. In our study, we have discovered something interesting: a unique crater‐like structure behind the RF. We found evidence for this in observations from the Magnetospheric Multiscale mission and computer simulations that study the behavior of particles in magnetic reconnection. Our simulations suggest that this crater shape happens because electrons have the high‐speed outflow and form current jets. It is like the electrons poured out from the inner electron diffusion region, hitting a speed bump. Another way to think about it is that this crater is formed by the continuous impact of fast‐outflowing electron jets. Understanding this crater structure helps us better grasp how the RF works and how energy changes during magnetic reconnection. Our research finds and tries to explain a new piece of the puzzle in understanding the mysteries of space and plasmas in the magnetic reconnection process.
Key Points
A novel crater structure is first verified behind the Reconnection front (RF) by both Magnetospheric Multiscale observations and particle‐in‐cell simulations
The formation of the crater structure appears to be associated with the high‐speed electron jets from inner electron diffusion region
A possible scenario that electron outflow constantly strikes the RF and then causes the formation of the crater structure
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