Projective Peridynamic Modeling of Hyperelastic Membranes With Contact.

Real-time simulation of hyperelastic membranes like cloth still faces a lot of challenges, such as hyperplasticity modeling and contact handling. In this study, we propose projective peridynamics that uses a local-global strategy to enable fast and robust simulation of hyperelastic membranes with contact. In the global step, we propose a semi-implicit strategy to linearize the governing equation for hyperelastic materials that are modeled with peridynamics. By decomposing the first Piola-Kirchhoff stress tensor into a positive and a negative part, successive substitutions can be taken to solve the nonlinear problems. Convergence is guaranteed by further addressing the overshooting problem. Since our global step solve requires no energy summation and dot product operations over the entire problem, it fits into GPU implementation perfectly. In the local step, we further present a GPU-friendly gradient descent method to prevent interpenetration by solving an optimization problem independently. Putting the global and local solves together, experiments show that our method is robust and efficient in simulating complex models of membranes involving hyperelastic materials and contact.

Highly Hierarchical Fibrillar Biogenic Silica with Mesoporous Structure Derived from the Perennial Plant Equisetum Fluviatile.

A new discovery of highly hierarchical fibrillar biogenic silica with mesoporous structure derived from the perennial plant Equisetum fluviatile was made. By removing the organic compounds through chemical and heat treatment, the biogenic silica skeleton can largely retained the original highly hierarchical structure of the plant stems. Infrared spectra, X-ray diffraction, and small-angle X-ray scattering, as well as nitrogen sorption analysis, were employed to characterize the crystalline phases, nanostructure, and porosity of the resulting material. Scanning electron microscopy and transmission electron microscopy investigation reveal that the biogenic silica are fibers with diameters of about 120-150 µm and lengths of more than a few centimeters. These fibers consist of smaller fasciculus with diameters of about 5-15 µm that are composed of three levels of particles with mass and surface fractal characteristics: primary particles on the order of 3-5 nm, secondary particles on the order of 9-12 nm, and tertiary particles on the order of 90-120 nm in size. It is also shown that the biogenic silica have mesoporous structure with an average pore size of 4-6 nm and a specific surface of 100-300 m2/g. Heat treatment at high temperature and residual K+ significantly affects the characteristics of the mesoporous structure of the biogenic silica, although it has little effect on the surface fractal structure of the secondary particles.

Pharmacokinetics of three proton pump inhibitors in Chinese subjects in relation to the CYP2C19 genotype.

OBJECTIVE: Omeprazole, lansoprazole and rabeprazole have been widely used as proton pump inhibitors (PPIs). They can be metabolized in the liver by CYP2C19, a polymorphic enzyme, and have a wide inter-individual variability with respect to drug response. In the investigation reported here, we examined the kinetic characteristics of the three PPIs in healthy Chinese subjects in relation to CYP2C19 genotype status. METHODS: Six homozygous extensive metabolizers (homEMs), six heterozygous extensive metabolizers (hetEMs) and six poor metabolizers (PMs) were recruited for the study from a total of 90 healthy Chinese volunteers whose CYP2C19 genotype status was determined by means of PCR-restriction fragment length polymorphism (RFLP). The study was had an open label, randomized, three-way crossover design. After a single oral dose of 40 mg omeprazole, 30 mg lansoprazole or 40 mg rabeprazole, plasma concentrations of the three PPIs were determined by HPLC. RESULTS: There were some differences for the area under the plasma concentration-time curve (AUC), the elimination half-life (t(1/2 ke)) and the maximum plasma concentration (c(max)) in the three groups. In the homEMs, hetEMs and PMs, the relative AUC(0-infinity) values were 1:2.8:7.5 for omeprazole, 1:1.7:4.0 for lansoprazole and 1:1.6:3.7 for rabeprazole, respectively; the relative t(1/2 ke) values were 1:1.02:1.65 for omeprazole, 1:1.08:2.39 for lansoprazole and 1:1.37:1.85 for rabeprazole, respectively; the relative c(max) values were 1:2.09:4.39 for omeprazole, 1:1.34:1.72 for lansoprazole, and 1:1.24:2.04 for rabeprazole, respectively. CONCLUSION: The pharmacokinetic characteristics of the three PPIs are significantly dependent on the CYP2C19 genotype status. These data indicate that individualized dose regimen of the three PPIs, based on identification of genotype, can be of great benefit for ensuring the reasonable use of these drugs.