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BACKGROUND: Hemodialysis initiation using a central venous catheter (CVC) poses an increased risk of death. Conversion to an arterio-venous graft or fistula (AVF, AVG) improves outcomes. The relationship of primary dialysis access and timing of conversion from CVC to either AVF or AVG to all-cause mortality was investigated. METHODS: Two retrospective analyses in incident hemodialysis patients commencing treatment from January 2010 to December 2014 in dialysis clinics in the United States were conducted. Analysis 1 stratified as per access at initiation and those commencing with CVC were further stratified into (a) those that had a CVC, AVF, or AVG the entire year; (b) those that were converted to either AVF or AVG within either (i) the first or (ii) the second 6 months. Kaplan Meier analysis and Cox regression analysis were employed. Analysis 2 included all CVC patients investigating the relationship between access conversion time and mortality risk using a Cox proportional hazards model depicting the hazard ratio (HR) as a spline function over time. RESULTS: Two subsets from initial 78,871 patients were studied. In Analysis 1 both AVF (referent) and AVG [HR 1.12 (0.97 to 1.30)] associated with a better outcome than CVC [HR 1.55 (1.38 to 1.74)] during follow-up. Lower mortality risk was seen for early switch from a CVC to AV access within the first 6 months [HR = 1.04 (0.97-1.13)] compared to a later switch [HR = 1.23 (1.10-1.38)]. Analysis 2 indicated that a CVC to AVF switch resulted in improved survival. Analysis 2 indicated early conversion to confer a survival benefit for CVC to AVG switch. DISCUSSION AND CONCLUSION: AVF and AVG show a survival benefit over CVC. Early conversion from CVC to either access improves survival. This emphasizes the importance of early preparation for dialysis by creation of an AVF or AVG and to convert CVCs early.

Here, a novel aluminum-gallium-phosphate (GAHPO) metal-inorganic framework structure was prepared by hydrothermal method, and it was fully characterized by single crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy, and gravimetric analysis-differential scanning calorimeter (TG-DSC). Single crystal X-ray diffraction results show that GAHPO is attributed to the trigonal system and Rc3 space group. Al(Ga) O6 octahedra and PO4 tetrahedral structures is distorted to form one-dimensional chains, and then is stacked into three-dimensional metal-inorganic frameworks through hydrogen bonding. TG-DSC shows that GAHPO is of high thermal stability, with the initial decomposition temperature of 240 ²C. Compared with aluminum phosphate, the introduction of Ga3+ distorted the AlPO4 lattice, thus weakening and elongating the Al--O bond, which makes more acid catalytic sites exposed and enhanced the catalytic activity. The experiment shows that when the reaction temperature is 60 ²C, and the catalyst dosage is 10% of acetaldehyde, GAHPO could catalyze the condensation of acetaldehyde to produce butanolal with good conversion rate (47%) and excellent selectivity ( >99%). The reaction mechanism of acetaldehyde condensation catalyzed by GAHPO was investigated using scavengers, NH3-TPD and specially designed derivatives to confirm the reactive sites of the catalyst and the substrate. This work provides a feasible way for novel aluminum inorganic framework structures and the catalytic applications. [ABSTRACT FROM AUTHOR]

In view of the situation that the workspace of the parallel robot is small,the workspace of an equivalent 8-SPU parallel mechanism is solved and optimized by using the three-dimensional boundary search method. Considering the rod length constraint,angle constraint,link interference,the inverse kinematics equation is established,all points in the workspace is searched,the three-dimensional boundary diagram with fixed posture is given,and then the influential curve of two mechanism parameters on workspace is given. Finally,the ratio of the volume with stroke of the rod is taken as the objective function,and particle swarm optimization algorithm is used to get the maximum function value. The global optimal solution is obtained,and the optimized three-dimensional diagram and the comprehensive indices comparison between unoptimized and optimized is given. The results show that the volume of workspace increases 143. 91% with 27. 59% raise of the stroke and the optimization effect is obvious.