Molecular Dynamics Simulation of the Crystal Nucleation and Growth Behavior of Methane Hydrate in the Presence of the Surface and Nanopores of Porous Sediment.

The behavior of hydrate formation in porous sediment has been widely studied because of its importance in the investigation of reservoirs and in the drilling of natural gas hydrate. However, it is difficult to understand the hydrate nucleation and growth mechanism on the surface and in the nanopores of porous media by experimental and numerical simulation methods. In this work, molecular dynamics simulations of the nucleation and growth of CH4 hydrate in the presence of the surface and nanopores of clay are carried out. The molecular configurations and microstructure properties are analyzed for systems containing one H2O hydrate layer (System A), three H2O hydrate layers (System B), and six H2O hydrate layers (System C) in both clay and the bulk solution. It is found that hydrate formation is more complex in porous media than in the pure bulk solution and that there is cooperativity between hydrate growth and molecular diffusion in clay nanopores. The hydroxylated edge sites of the clay surface could serve as a source of CH4 molecules to facilitate hydrate nucleation. The diffusion velocity of molecules is influenced by the growth of the hydrate that forms a block in the throats of the clay nanopore. Comparing hydrate growth in different clay pore sizes reveals that the pore size plays an important role in hydrate growth and molecular diffusion in clay. This simulation study provides the microscopic mechanism of hydrate nucleation and growth in porous media, which can be favorable for the investigation of the formation of natural gas hydrate in sediments.

[Therapeutic evaluation of He-wei Jie-gu (Chinese characters)Decoction on femoral intertrochanteric fracture after internal fixation in elderly: a randomized controlled trial].

OBJECTIVE: To observe the efficacy of He-wei Jie-gu (Chinese characters) decoction on femoral intertrochanteric fractures after internal fixation in elderly. METHODS: From January 2010 to January 2012, 90 elderly patients with osteoporotic intertrochanteric fracture were randomly divided into two groups. The patients in experimental group were treated with open reduction and internal fixation, He-wei Jie-gu decoction and Caltrate D in oral, including 18 males and 27 females with an average age of (77.8±11.3) years old ranging from 65 to 89 years old;the time from injured to operation was 2 to 9 days with an average of (6.6±2.1) days; according to Evans-Jensen classification, 17 cases were in type I, 8 in type II, 15 in type III, 3 in type IV, 2 in type V. Meanwhile, the patients in control group were treated with open reduction and internal fixation, Caltrate D in oral, including 16 males and 29 females with an average age of (81.2±9.6) years old ranging from 67 to 91 years old; the time from injury to operation was 2 to 10 days with an average of (6.8±2.6) days; according to Evans-Jensen classification, 15 cases were in type I, 10 in type II, 14 in type III, 4 in type W, 2 in type V. The VAS score, hip BMD value before and after treatment, fracture healing and the Harris function score after operation were recorded and compared. RESULTS: All patients were followed up from 3 to 9 months with an average of (5.6±2.8) months. Compared with the control group, the VAS score of the experimental group had an obviously reduction (F=98.138, P<0.01) after treatment; the hip BMD value at 3 months after treatment in the experimental group was higher than that of the control group (P<0.05); the fracture healing rate of the experimental group was higher than that of the control group (P<0.05); Harris score in 3 months of follow-up in the experimental group was higher than that of the control group (t=2.542, P<0.05); all the differences between two groups were statistically significant (P<0.05). CONCLUSION: He-wei Jie-gu decoction can reduce postoperative pain and increase bone mineral density after internal fixation of femoral intertrochanteric fracture in elderly, promote the fracture healing and functional recovery in the hip joint.

[Synaptic vesicle recycling and Alzheimer's disease].

Loss of synapses correlates well with cognitive decline in Alzheimer's disease (AD). However, the molecular mechanisms underlying the synaptic dysfunction and loss are not well understood. Synaptic vesicle (SV) recycling is a key process for synaptic transmission. A body of evidences suggested that malfunction or loss of the machinery for SV recycling occurred in AD, which could result in disruption of neuronal circuitry. In this article, we summarized the recent progress in the research of synaptic proteins for SV recycling and the pathological changes of some proteins in AD.