Torsional fretting and torsional sliding wear behaviors of CuNiAl against 42CrMo4 under dry condition

Many wear failures are caused by a combination of fretting wear and sliding wear. In this study, the torsional fretting and torsional sliding wear properties of CuNiAl against 42CrMo4 were comparatively investigated under dry condition using a flat on flat contact tester. Experimental results showed that the sliding friction coefficients declined more dramatically than the fretting friction coefficients when the normal load increased. The fretting wear rate was lower than the sliding wear rate, which was partly due to the solid lubrication effect of the wear debris and strain hardening of the worn surfaces. The dominant wear mechanisms for the fretting tests were oxidation, cracks and delamination, while for the sliding tests were abrasion combined with plastic deformation

Determination of 4 Kinds of β-Agonists Residues in Braised Meat by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS) method was developed for the determination of four β-agonists (terbutaline, clenbuterol, ractopamine, salbutamol) in braised meat. Samples were hydrolyzed by β-glucuronidase and cleaned up by an SLS solid phase extraction column. The separation was performed on a Thermo Hypersil Gold C18 column with a gradient elution of 0.1% formic acid water and acetonitrile as mobile phases, ESI+ was used for multiple response monitoring (MRM) and quantitative analysis by internal standard method. The linear relationship of the four β-agonists was good in the concentration range of 0.5 μg/L to 9.5 μg/L, and the correlation coefficient (r) was greater than 0.9988. The limit of detection (LOD) was 0.1 μg/kg, and the limit of quantitation (LOQ) was 0.3 μg/kg. The recoveries were 87.9%~113.7% and RSDs were 1.48%~9.32% at three spiked levels (1, 5 and 9 μg/kg). In a total of 162 batches of braised meat samples, one sample of braised pig’s trotter was found to contain 1.51 μg/kg of clenbuterol and 3.65 μg/kg of ractopamine. Additionally, another sample of braised lamb was found to contain 11.5 μg/kg of clenbuterol. The method is rapid and accurate, and can be used for qualitative and quantitative determination of four β-agonists (terbutaline, clenbuterol, ractopamine, salbutamol) in braised meat

Evaluation of Early Prognostic Factors of Mortality in Patients with Acute Pancreatitis: A Retrospective Study

Early and accurate assessment of severity in acute pancreatitis (AP) is of great importance to provide effective disease management and prevent mortality. In this study, we aim to evaluate early indicators that predict the mortality of AP. We retrospectively analyzed 24-hour clinical characteristics and laboratory data in 166 AP patients recruited between January 2014 and November 2015 in Baotou Central Hospital. In total, 18 patients did not survive the disease. Multivariate logistic regression showed that red cell distribution (RDW) (OR = 2.965, P=0.001) and creatinine (OR = 1.025, P=0.005) were early independent risk factors of AP mortality while albumin (OR = 0.920, P=0.032) levels reduced AP mortality. The corresponding optimal cut-off values were 14.45, 125.5, and 34.95, respectively. The positive predictive values of the AP mortality were 80.1%, 54.5%, and 69.5%. In combined measurement, the area under the curve of RDW, creatinine, and albumin was 0.964 (95% CI: 0.924 to 1.000, P<0.001). RDW ≥ 14.45%, creatinine ≥ 125.5 μmol/l, and albumin ≤ 34.95 g/l indicated a good predictive value for mortality in AP patients with a sensitivity of 100% and specificity of 64.2%. RDW, creatinine, and albumin may serve as early indicators for AP mortality which warrants further clinical investigation

Influence of surface topography on torsional fretting wear under flat-on-flat contact

Influence of surface topography on torsional fretting under flat-on-flat contact were investigated. Contact surfaces of the lower specimens were prepared by milling with different initial surface roughness while the upper specimens were polished. Results indicate that with the increase of surface roughness, friction torque and accumulated dissipated energy present a first increase and then decrease tendency and are higher when the texture is perpendicular to the relative movement direction. The wear volume and wear rate present increasing and decreasing tendencies separately for textures parallel and perpendicular to the relative movement direction, and they are higher when the texture is parallel to the relative movement direction. The results can provide guidance for the initial surface design to reduce fretting wear

The molecular dynamic simulation on impact and friction characters of nanofluids with many nanoparticles system

Impact and friction model of nanofluid for molecular dynamics simulation was built which consists of two Cu plates and Cu-Ar nanofluid. The Cu-Ar nanofluid model consisted of eight spherical copper nanoparticles with each particle diameter of 4 nm and argon atoms as base liquid. The Lennard-Jones potential function was adopted to deal with the interactions between atoms. Thus motion states and interaction of nanoparticles at different time through impact and friction process could be obtained and friction mechanism of nanofluids could be analyzed. In the friction process, nanoparticles showed motions of rotation and translation, but effected by the interactions of nanoparticles, the rotation of nanoparticles was trapped during the compression process. In this process, agglomeration of nanoparticles was very apparent, with the pressure increasing, the phenomenon became more prominent. The reunited nanoparticles would provide supporting efforts for the whole channel, and in the meantime reduced the contact between two friction surfaces, therefore, strengthened lubrication and decreased friction. In the condition of overlarge positive pressure, the nanoparticles would be crashed and formed particles on atomic level and strayed in base liquid

Emerging role of the calcium-activated, small conductance, SK3 K ⁺ channel in distal tubule function: Regulation by TRPV4

The Ca2+-activated, maxi-K (BK) K+ channel, with low Ca2+-binding affinity, is expressed in the distal tubule of the nephron and contributes to flow-dependent K+ secretion. In the present study we demonstrate that the Ca2+-activated, SK3 (KCa2.3) K + channel, with high Ca2+-binding affinity, is also expressed in the mouse kidney (RT-PCR, immunoblots). Immunohistochemical evaluations using tubule specific markers demonstrate significant expression of SK3 in the distal tubule and the entire collecting duct system, including the connecting tubule (CNT) and cortical collecting duct (CCD). In CNT and CCD, main sites for K+ secretion, the highest levels of expression were along the apical (luminal) cell membranes, including for both principal cells (PCs) and intercalated cells (ICs), posturing the channel for Ca2+- dependent K+ secretion. Fluorescent assessment of cell membrane potential in native, split-opened CCD, demonstrated that selective activation of the Ca2+-permeable TRPV4 channel, thereby inducing Ca2+ influx and elevating intracellular Ca2+ levels, activated both the SK3 channel and the BK channel leading to hyperpolarization of the cell membrane. The hyperpolarization response was decreased to a similar extent by either inhibition of SK3 channel with the selective SK antagonist, apamin, or by inhibition of the BK channel with the selective antagonist, iberiotoxin (IbTX). Addition of both inhibitors produced a further depolarization, indicating cooperative effects of the two channels on Vm. It is concluded that SK3 is functionally expressed in the distal nephron and collecting ducts where induction of TRPV4-mediated Ca2+ influx, leading to elevated intracellular Ca2+ levels, activates this high Ca2+- affinity K+ channel. Further, with sites of expression localized to the apical cell membrane, especially in the CNT and CCD, SK3 is poised to be a key pathway for Ca2+-dependent regulation of membrane potential and K+ secretion. © 2014 Berrout et al

Session Recommendation Algorithm Combining Item Transition Relations and Time-Order Information

Aiming at the problem that the existing graph neural network session recommendation algorithm ignores all kinds of auxiliary information, which leads to the inability to accurately model the session sequence, a session recommendation algorithm combining the item transition relations and time-order information (RTSR) is proposed. Firstly, the shortest path sequence between any two nodes is obtained by using the graph network structure, which is encoded as the item transition relations between corresponding items through the gated recurrent unit (GRU), and then the global dependency information of the session is captured from the perspective of the graph by combining the self-attention mechanism. At the same time, a lossless graph coding scheme is designed to alleviate the problem of information loss in the process of session graph coding. The scheme quantifies the time-order information in the session sequence reasonably, and takes it as the weight of the edges in the session graph, and then combines the gated graph sequence neural network to obtain the local dependency information of the session. Finally, with linear combination of global dependency information and local dependency information, and in combination with reverse position information,&nbsp; the user??s preference for item is finally generated, and the recommendation list is given. The performance comparison experiment with mainstream models such as SR-GNN, GC-SAN and GCE-GNN on the public benchmark datasets Gowalla and Diginetica shows that RTSR&nbsp; improves at least 6.13% and 1.58% in average reciprocal ranking respectively, and the recommendation accuracy is also improved accordingly

Research on Strut-and-Tie Models of Beam-Column Connections by Topology Optimization based on Moving Morphable Components

It is of great theoretical and practical significance to study the strut-and-tie models of beam-column connections. In this paper, an explicit topology optimization based on moving morphable components was used to analyze the strut-and-tie models, which overcomes the shortcomings of traditional implicit topology optimization. In this method, the problem of generating a suitable strut-and-tie model is transformed into an optimization problem with minimum compliance under volume constraints. The optimal topology is automatically generated by a set of components that can move, morph, intersect, and overlap, and then the reliable strut-and-tie models are formed. Through three examples of beam-column connections under three load conditions, the strut-and-tie models under single and multiple load cases were analyzed, and the feasibility, validity, and high efficiency of this method were verified