Local and global avalanches in a 2D sheared granular medium

We present the experimental and numerical studies of a 2D sheared amorphous material constituted of bidisperse photo-elastic disks. We analyze the statistics of avalanches during shear including the local and global fluctuations in energy and changes in particle positions and orientations. We find scale free distributions for these global and local avalanches denoted by power-laws whose cut-offs vary with inter-particle friction and packing fraction. Different exponents are found for these power-laws depending on the quantity from which variations are extracted. An asymmetry in time of the avalanche shapes is evidenced along with the fact that avalanches are mainly triggered from the shear bands. A simple relation independent from the intensity, is found between the number of local avalanches and the global avalanches they form. We also compare these experimental and numerical results for both local and global fluctuations to predictions from meanfield and depinning theories

tissue of rat adjuvant-induced arthritis

Triptolide has been clinically used to treat patients with rheumatoid arthritis, in which chemokine receptors play an important role in immune and inflammatory responses. To investigate the effect of triptolide on CCR5, we used complete Freund’s adjuvant to produce adjuvant-induced arthritis (AIA) in rats. Our data show that both CCR5 mRNA and protein levels in synovial tissue of rats with AIA are significantly higher than those in normal rats. Triptolide can significantly inhibit rat AIA-induced overexpression of CCR5 at both mRNA and protein levels. These results may contribute to better understanding of the therapeutic effects of triptolide in rheumatoid arthritis. Key words: triptolide, CCR5, adjuvant induced arthritis, rheumatoid arthriti

Determination of sunset yellow and tartrazine using silver and poly (L-cysteine) composite film modified glassy carbon electrode

Silver and poly(L-cysteine) composite film modified glassy carbon electrode (PLC/Ag/GCE) has been fabricated via cyclic voltammetry and used for investigation of the electrochemical behavior of sunset yellow (SY) and tartrazine (TT). A pair of anodic peak at 0.760 V (vs. Ag/AgCl) and cathodic peak at 0.701 V (vs. Ag/AgCl) for SY and an anodic peak at 1.013 V (vs. Ag/AgCl) of TT are observed in pH 4.5 phosphate buffer solution. Based on the two well-resolved anodic peaks of SY and TT, a novel electrochemical method has been successfully developed for simultaneous determination of SY and TT using differential pulse voltammetry. Under the optimized experimental conditions, the linear range for the determination of SY and TT are 5.00×10-7 –3.00×10-4 mol L-1 and 7.50×10-7–7.50×10-4 mol L-1, respectively with detection limits of 7.50×10-8 mol L-1 and 2.50×10-7 mol L-1, respectively. The proposed method has been applied for simultaneous determination SY and TT in beverage with satisfactory results

Performance of several simple, noninvasive models for assessing significant liver fibrosis in patients with chronic hepatitis B

Aim To compare the performance of several simple, noninvasive models comprising various serum markers in diagnosing significant liver fibrosis in the same sample of patients with chronic hepatitis B (CHB) with the same judgment standard. Methods A total of 308 patients with CHB who had undergone liver biopsy, laboratory tests, and liver stiffness measurement (LSM) at the Southwest Hospital, Chongqing, China between March 2010 and April 2014 were retrospectively studied. Receiver operating characteristic (ROC) curves and area under ROC curves (AUROCs) were used to analyze the results of the models, which incorporated ageplatelet (PLT) index (API model), aspartate transaminase (AST) to alanine aminotransferase (ALT) ratio (AAR model), AST to PLT ratio index (APRI model), γ-glutamyl transpeptidase (GGT) to PLT ratio index (GPRI model), GGT-PLT-albumin index (S index model), age-AST-PLT-ALT index (FIB-4 model), and age-AST-PLT-ALT-international normalized ratio index (Fibro-Q model). Results The AUROCs of the S index, GPRI, FIB-4, APRI, API, Fibro-Q, AAR, and LSM for predicting significant liver fibrosis were 0.726 (P < 0.001), 0.726 (P < 0.001), 0.621 (P = 0.001), 0.619 (P = 0.001), 0.580 (P = 0.033), 0.569 (P = 0.066), 0.495 (P = 0.886), and 0.757 (P < 0.001), respectively. The S index and GPRI had the highest correlation with histopathological scores (r = 0.373, P < 0.001; r = 0.372, P < 0.001, respectively) and LSM values (r = 0.516, P < 0.001; r = 0.513, P < 0.001, respectively). When LSM was combined with S index and GPRI, the AUROCs were 0.753 (P < 0.001) and 0.746 (P < 0.001), respectively. Conclusion S index and GPRI had the best diagnostic performance for significant liver fibrosis and were robust predictors of significant liver fibrosis in patients with CHB for whom transient elastography was unavailable

Numerical investigation on transverse heat transfer properties in cross section of full size Nb3Sn CICC ITER conductor

The contact mechanical characteristics in the cross section of the Nb3Sn cable are sensitive to the cryogenic cooling and cyclic transverse electromagnetic loads, which may affect the cable’s performance. In this paper, based on a proposed discrete dynamic model (DEM), where the contact heat transfer among strands and the convective heat transfer in liquid helium are taken into account, the cooling process under two heat transfer mechanisms is performed. Simulation results show that the temperature variation of Poloidal Field Insert Sample (PFIS) cable with time agrees well with the existing experimental results, and the role of contact heat transfer cannot be neglected during cryogenic cooling. It is obtained from the further analysis that the effect of contact heat transfer becomes more prominent with the decrease of mass flow rate of liquid helium, which leads to the stress status within cable changed significantly. With the temperature boundary condition imposed on the cable radial direction, the effective thermal conductivity (ETC) of cable can be obtained. It can be found that the ETC increases with increasing the transverse loads and is sensitive to the low temperature environment, while it is not affected by load cycles basically. These results may provide the guide for the design and application of the future CICC conductors

The scaling and dynamics of a projectile obliquely impacting a granular medium

In this paper, the dynamics of a spherical projectile obliquely impacting into a two-dimensional granular bed is numerically investigated using the discrete element method. The influences of projectile’s initial velocities and impacting angles are mainly considered. Numerical results show that the relationship between the final penetration depth and the initial impact velocity is very similar to that in the vertical-impact case. However, the dependence of the stopping time on the impact velocity of the projectile exhibits critical characteristics at different impact angles: the stopping time approximately increases linearly with the impact velocity for small impact angles but decreases in an exponential form for larger impact angles, which demonstrates the existence of two different regimes at low and high impact angles. When the impact angle is regarded as a parametric variable, a phenomenological force model at large impact angles is eventually proposed based on the simulation results, which can accurately describe the nature of the resistance force exerted on the projectile by the granular medium at different impact angels during the whole oblique-impact process. The degenerate model agrees well with the existing experimental results in the vertical-impact cases

Effect of variable particle stiffness on force propagation and mechanical response of a composite granular material

The force propagation and mechanical response are important for understanding the elasticity and deformation of a composite granular packings. In this paper, a 2D composite granular layers composed of particles with variable stiffness is proposed, and the effect of stiffness ratio between component particles on mechanical response is mainly considered. The results show that the decrease of stiffness ratio broadens the linear range of mechanical response and enhances the elasticity of the response in a composite granular system, showing a role similar with the friction in a monodisperse granular packings. Furthermore, a phase diagram for the crossover between a single-peaked and a double-peaked response is proposed, in which the critical stiffness ratio corresponding to the occurrence of the crossover decreases with the magnitude of external loading and increases with the friction. Finally, the microscopic mechanism of the crossover of the response is further discussed based on changes in contact network and force network