A relation between the ensemble average and the nearest particle statistics is derived. The relation accounts for interactions among all the particles, not only the nearest one, and can be used to ...study long-range particle interactions without the difficulty of a divergent integral. As an example, this relation is applied to calculate the particle sedimentation velocity to the first order of the particle volume fraction. Using the relation, an important particle–fluid–particle stress is introduced for general multiphase flows.
A generalization of the Lees-Edwards periodic boundary conditions (gLE-PBC) for molecular dynamics (MD) simulations is developed to allow for arbitrary deformations to be applied to the domain. The ...gLE-PBC domain remains a rectangular cuboid regardless of the applied deformation in contrast with the Lagrangian-rhomboid periodic boundary conditions (LR-PBC) where the domain deforms according to the applied deformation. The kinematics of gLE-PBC are validated against pure shear. The gLE-PBC method for interacting systems is then validated against the LR-PBC method and analytical solutions for a solid under isotropic compression, one-dimensional shearing, three-dimensional extension and shearing and for a liquid under Couette flow. Bulk physical properties extracted from the gLE-PBC simulations agree well with values calculated from equilibrium MD simulations. Three dimensional shearing and a deformation with a full velocity gradient matrix are also simulated, showing the range of problems gLE-PBC can explore.
Programmed cell death is essential for the development and maintenance of the immune system and its responses to exogenous and endogenous stimuli. Studies have demonstrated that in addition to ...caspase-dependent apoptosis, necrosis dependent on the kinases RIP1 and RIP3 (also called necroptosis) is a major programmed cell-death pathway in development and immunity. These two programmed cell-death pathways may suppress each other, and necroptosis also serves as an alternative when caspase-dependent apoptosis is inhibited or absent. Here we summarize recent advancements that have identified the molecular mechanisms that underlie necroptosis and explore the mechanisms that regulate the interplay between apoptosis and necroptosis.
Necrosis can be induced by stimulating death receptors with tumor necrosis factor (TNF) or other agonists; however, the underlying mechanism differentiating necrosis from apoptosis is largely ...unknown. We identified the protein kinase receptor-interacting protein 3 (RIP3) as a molecular switch between TNF-induced apoptosis and necrosis in NIH 3T3 cells and found that RIP3 was required for necrosis in other cells. RIP3 did not affect RIP1-mediated apoptosis but was required for RIP1-mediated necrosis and the enhancement of necrosis by the caspase inhibitor zVAD. By activating key enzymes of metabolic pathways, RIP3 regulates TNF-induced reactive oxygen species production, which partially accounts for RIP3's ability to promote necrosis. Our data suggest that modulation of energy metabolism in response to death stimuli has an important role in the choice between apoptosis and necrosis.
The role of water in degradation of nitroplasticizer (NP) was studied using a set of NP samples aged inside confined containers between room temperature and 70∘C with their water concentrations ...monitored during the aging course. For the first 42 days at the temperatures 55∘C and below, simple Fickian diffusion dominates the monotonic decreases of the water concentrations with time. After about 60–80 days depending on temperatures, diffusion alone can no longer explain the water decreases, despite no significant NP degradation detectable using the FTIR spectroscopy. Starting at about 80–160 days, also depending on temperatures, the measured water concentrations fluctuated around mean values that decrease with increasing temperature, and the onset of NP degradation was detected using FTIR and TGA. It was found that NP contains an irreducible amount of water on the order of a few hundred ppms, which decreases with increasing temperature. Pristine NP does not exist with a water concentration lower than this amount. The diffusivity, the irreducible amount of water in NP, and the mean water production rate due to NP degradation are calculated from the water concentrations of the first aging stage and the mean water concentrations during the onset of NP degradation. They all change with the temperature following Arrhenius laws with different prefactors and activation energies. This study shows that trace water formation is an intrinsic property of the NP while it ages with the mechanistic details to be resolved.
•Nitroplasticizer (NP) is frequently mixed with particles to enhance manufacturability and properties of the final product.•Degradation of NP is important to the stability of the final product.•This work studies the role of water in the NP degradation.
Many multiscale methods for granular materials use periodic computational domains to consider particle scale interactions and then calculate the stress to drive the continuum scale calculations. For ...problems involving large material deformations, the computation domain often needs to be reinitialized because of the distortion, causing the loss of the history information of the system. This work introduces an algorithm to accommodate a large deformation of the material while maintaining the computational domain cuboid to avoid the domain reinitialization during the computation. The algorithm uses a rotating frame of reference, in which the velocity gradient can be represented by an upper triangular matrix. The deformation caused by the upper triangular matrix is treated by the image system implied in the periodicity to maintain the computational domain cuboid. The effect from the rotation of the reference frame is considered using the inertial forces. Simulations of simple and pure shear motions are carried out to illustrate the algorithm.
•An algorithm is introduced to maintain periodic computational domain cuboid.•Domain reinitialization is avoided even for large deformations.•The algorithm uses a rotating frame of reference and considers inertia forces.
The 2014-2015 Ebola epidemic was considered to be the largest and most complex outbreak, which caused 11,310 reported deaths. The epidemic disease can cause a mental health crisis, however, there is ...only a small amount of scientific literature available related to this health issue so far. We evaluated the psychological symptoms of 161 participants including Ebola survivors and healthcare workers in Sierra Leone, analyzed the impact of job classification, education level on psychological status. We found that the order of total general severity index (GSI) scores from high to low was EVD survivors, SL medical staff, SL logistic staff, SL medical students, and Chinese medical staff. There were 5 dimensions (obsession-compulsion, anxiety, hostility, phobic anxiety, and paranoid ideation) extremely high in EVD survivors. GSI were associated with university education negatively. We believed our information is necessary to develop the comprehensive emergency response plan for emerging infectious disease outbreak.
A numerical scheme of computing quantities involving gradients of shape functions is introduced for the material point method (MPM), so that the quantities are continuous as material points move ...across cell boundaries. The noise and instability caused by cell crossing of the material points are then eliminated. In this scheme, the formulas used to compute these quantities can be expressed in the same forms as in the original material point method, but with the gradient of the shape function modified. For one-dimensional cases, the gradient of the shape function used in the generalized interpolation material point (GIMP) method is a special case of the modified gradient if the characteristic function of a material point is introduced.
The characteristic function of a material point is not otherwise needed in this scheme, therefore difficulties in tracking its evolution are avoided. Although the support of the modified gradient of a shape function is enlarged from the cell containing the material point to also include the immediate neighbor cells, all the non-local effects of a material point can be accounted for by two consecutive local operations. Therefore this scheme can be used in calculations with unstructured grids.
This scheme is proved to satisfy mass and momentum conservations exactly. The error in energy conservation is shown to be second order on both spatial and temporal discretizations. Although the error in energy conservation is the same order as that in the original material point method, numerical examples show that this scheme has significantly better energy conservation properties than those of the original material point method.
This study investigated the risk factors for epiretinal membrane (ERM) in eyes with primary rhegmatogenous retinal detachment (RRD) that received silicone oil (SO) tamponade.
This retrospective ...analysis included 1140 patients (1140 eyes) with RRD who underwent primary vitrectomy and SO tamponade. The prevalence of ERM was estimated and possible risk factors (eg, type 2 diabetes, proliferative vitreoretinopathy (PVR), SO tamponade time (SOTT), photocoagulation, vitreous haemorrhage, choroidal detachment, cryotherapy and retinal tear size) were analysed via multiple logistic regression.
The prevalence of ERM was 12.3% (140/1140), and the accuracy of preoperative ERM diagnosis was 40.5%. Multivariate logistic regression analysis showed that risk factors for ERM in eyes with SO tamponade included preoperative PVR (OR=4.336, 95% CI 2.533 to 7.424, p<0.001), type 2 diabetes (OR=3.996, 95% CI 2.013 to 7.932, p<0.001), photocoagulation energy (OR=1.785, 95% CI 1.306 to 2.439, p<0.001) and SOTT (OR=1.523, 95% CI 1.261 to 1.840, p<0.001). No statistically significant associations were observed between the incidence of ERM and other risk factors. Preoperative PVR showed the strongest association with risk of ERM. The risk of ERM was positively associated with SOTT, photocoagulation energy and preoperative PVR grade.
In eyes with RRD that received SO tamponade, the prevalence of ERM was 12.3%, while the accuracy of preoperative ERM diagnosis was low. Preoperative PVR, type 2 diabetes, photocoagulation energy and SOTT were the main risk factors for ERM.
PDF
