► A model for concrete in FRP-confined steel tubular columns is presented. ► The behavior of the steel tube under biaxial loading is rigorously represented. ► The proposed model provides accurate ...predictions of experimental results.
Concrete-filled steel tubes (CFTs) are widely used as columns in many structural systems. In CFTs, degradation in steel confinement, strength and ductility can result from inelastic outward local buckling. To overcome this deficiency of CFTs, external confinement of CFTs with an FRP jacket has been explored in recent studies. This paper presents a theoretical model in an incremental–iterative form for circular FRP-confined CFTs (CCFTs) under monotonic axial compression, with the focus being on the stress–strain behavior of the confined concrete. The proposed stress–strain model for concrete in CCFTs is based on the same approach as that commonly adopted by existing models for FRP-confined concrete and includes three components: (a) an active-confinement model; (b) a lateral strain equation; and (c) equations for determining the total confining pressure from the steel tube and the FRP jacket. It is shown that the lateral dilation behavior of concrete in CCFTs differs significantly from that of FRP-confined concrete in the initial stage because the former experiences more severe micro-cracking than the latter in the initial stage of loading; this difference is reflected in the proposed model. In general, the predictions of the proposed model are in close agreement with existing test results. The proposed model provides a useful tool for a parametric study on the stress–strain behavior of confined concrete in CCFTs to produce results for the formulation of simple stress–strain model in closed-form expressions for design use.
Poly(vinyl alcohol) (PVA)-xanthan gum (XG) hydrogel, which possesses good reusable absorption properties, has been prepared by the freezing–thawing method. Hydrogels prepared with different ratios ...compositions are characterized using Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscope (SEM), and examined in terms of their swelling behavior, mechanical, rheological and adsorption properties. The results show that a shift in the major signals of FTIR for OH absorption, and with varied intensities in the FTIR spectra andmore and more wrinkles observed in SEM indicated cross-linked interaction by the polymers. All the features of the PVA-XG hydrogel are closely related to its rheological properties. The presence of XG visibly improves the swelling ratio of PVA-XG and reduces the compression properties of PVA-XG due to the formation of hydrogen bonds between the PVA and XG. PVA-XG-4 had the best adsorption of methylene blue (MB) dye, such enhancement in adsorption can be attributed to strong electrostatic attraction between XG and MB. The adsorption conformed to the second-order kinetic model and the adsorption process conformed to the Langmuir isotherm model. In addition, PVA-XG-4 exhibits a promising cycling absorption performance. The 1st and 5th cycle of dye removal for PVA-XG-4 reached to 92 and 80%, respectively. Provides basis for application in water treatment.
Some gamma-ray bursts (GRBs) have a tera-electron volt (TeV) afterglow, but the early onset of this has not been observed. We report observations with the Large High Altitude Air Shower Observatory ...(LHAASO) of the bright GRB 221009A, which serendipitously occurred within the instrument's field of view. More than 64,000 photons >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger and then rose to a peak ~10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle of ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.
Precision spectroscopy of molecular hydrogen can be used to test the quantum electrodynamics theory and determine the proton-to-electron mass ratio in a four-body system. Cavity-enhanced ...double-resonance spectroscopy is proposed to determine highly-excited rotation-vibration energies of HD with high precision. As a demonstration, the V-type comb-locked cavity-assisted double resonance (COCA-DR) spectroscopy of HD is measured by pumping the P(1) (2-0) line and probing the R(1) line in the same overtone band. The sum value of the two transition frequencies is determined to be 426 889 423 917 (26) kHz, representing a new test of theoretical calculations.
A rectangular filtering dielectric resonator antenna (FDRA) with low profile, wide bandwidth, and high gain is first investigated in this communication. It is fed by a microstrip-coupled slot from ...bottom, with open stub of the microstrip feedline elaborately designed to provide two radiation nulls at band edges for a filtering function. A separation is introduced in the slot to provide a good suppression level in lower stopband, while two parasitic strips are parallelly added to the microstrip feedline to offer good suppression in the upper stopband, and consequently, a compact FDRA with a quasi-elliptic bandpass response is obtained without involving specific filtering circuits. Based on the design, a modified DRA fed by a pair of separated slots is proposed to further enhance the gain by ~4 dB. A prototype operating at 5 GHz has been fabricated and measured for demonstration. The reflection coefficient, the radiation pattern, and the antenna gain are studied, and reasonable agreement between the measured and simulated results is observed. The prototype has a 10-dB impedance bandwidth of 20.3%, an average gain of 9.05 dBi within passband, and an out-of-band suppression level of more than 25 dB within a wide stopband.
Depression is associated with alterations in corticostriatal reward circuitry. One pathophysiological pathway that may drive these changes is inflammation. Biomarkers of inflammation (for example, ...cytokines and C-reactive protein (CRP)) are reliably elevated in depressed patients. Moreover, administration of inflammatory stimuli reduces neural activity and dopamine release in reward-related brain regions in association with reduced motivation and anhedonia. Accordingly, we examined whether increased inflammation in depression affects corticostriatal reward circuitry to lead to deficits in motivation and goal-directed motor behavior. Resting-state functional magnetic resonance imaging was conducted on 48 medically stable, unmedicated outpatients with major depression. Whole-brain, voxel-wise functional connectivity was examined as a function of CRP using seeds for subdivisions of the ventral and dorsal striatum associated with motivation and motor control. Increased CRP was associated with decreased connectivity between ventral striatum and ventromedial prefrontal cortex (vmPFC) (corrected P<0.05), which in turn correlated with increased anhedonia (R=-0.47, P=0.001). Increased CRP similarly predicted decreased dorsal striatal to vmPFC and presupplementary motor area connectivity, which correlated with decreased motor speed (R=0.31 to 0.45, P<0.05) and increased psychomotor slowing (R=-0.35, P=0.015). Of note, mediation analyses revealed that these effects of CRP on connectivity mediated significant relationships between CRP and anhedonia and motor slowing. Finally, connectivity between striatum and vmPFC was associated with increased plasma interleukin (IL)-6, IL-1beta and IL-1 receptor antagonist (R=-0.33 to -0.36, P<0.05). These findings suggest that decreased corticostriatal connectivity may serve as a target for anti-inflammatory or pro-dopaminergic treatment strategies to improve motivational and motor deficits in patients with increased inflammation, including depression.
► This is the first study of CH4, CO2 and N2O concentrations in soil down to 300cm. ► The distinct differences were found in greenhouse gas concentration profiles. ► CO2 concentrations were ...relatively high in the warm and moist maize growing season. ► No clear seasonal patterns were found for concentration profiles of CH4 and N2O. ► Temporary increases were most pronounced for N2O (e.g. nitrogen fertilization).
Agricultural soils are main sources and sinks of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The source–sink function depends on soil characteristics, climate and management. Emission measurements usually quantify the net result of production, consumption and transport of these gases in the soil; they do not provide information about the depth distributions of the concentrations of these gases in the soil. Here we report on concentrations of CO2, CH4 and N2O in air of 300cm deep soil profiles, at resolutions of 30–50cm, over a full year. Gas samples were taken weekly in a long-term field experiment with an irrigated winter wheat–summer maize double cropping system, and four fertilizer N application rates (0, 200, 400 and 600kgNha−1year−1). The results showed distinct differences in CH4, CO2 and N2O concentrations profiles with soil depth. The concentrations of CO2 in soil air increased with soil depth and showed a seasonal pattern with relatively high concentrations in the warm and moist maize growing season and relatively low concentrations in the winter-wheat growing season. In contrast, CH4 concentrations decreased with depth, and did not show a distinct seasonal cycle. Urea application did not have a large effect on CH4 or CO2 concentrations, neither in the topsoil nor the subsoil. Concentrations of N2O responded to N fertilizer application and irrigation. Application of fertilizer strongly increased grain and straw yields of both winter wheat and summer maize, relatively to the control, but differences in yield between the treatments N200, N400 and N600 were not statistically significant. However, it significantly increased mean N2O concentrations peaks at basically all soil depths. Interestingly, concentrations of N2O increased almost instantaneously in the whole soil profile, which indicates that the soil had a relatively high diffusivity, despite compacted subsoil layers.
In conclusion, the frequent measurements, at high depth resolutions, of concentrations of CH4, CO2 and N2O in soil air under a winter wheat–summer maize double crop rotation provide detailed insight into the production, consumption and transport of these gases in the soil. Concentrations of CH4, CO2 and N2O responded differently to management activities and weather conditions.
Growing evidence indicates that resistin-an obesity-related cytokine-is upregulated in breast cancer patients, yet its impact on breast cancer behavior remains to be ascertained. Similarly, Toll-like ...receptor 4 (TLR4) has been implicated in breast cancer progression, however, its clinically relevant endogenous ligand remains elusive. In this study, we observed that high serum resistin levels in breast cancer patients positively correlated with tumor stage, size and lymph node metastasis. These findings were replicated in animal models of breast cancer tumorigenesis and metastasis. Resistin was found to promote epithelial-mesenchymal transition and stemness in breast cancer cells-mechanisms critical to tumorigenesis and metastasis-through a TLR4/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/signal transducer and activator of transcription 3 (STAT3) signaling pathway and negated by TLR4-specific antibody and antagonist. These findings provide clear evidence that resistin is a clinically relevant endogenous ligand for TLR4, which promotes tumor progression via TLR4/NF-κB/STAT3 signaling, providing insights into a novel therapeutic target in breast cancer.
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