No abstract

The effect of molecular weights and hydrolysis degrees (HD) of polyvinyl alcohol (PVA) on thermal and mechanical properties and crystallinity of polylactic acid (PLA)/PVA blends was investigated. Blends were prepared by the melt blending method using PLA/PVA ratios: 80/20, 90/10 and 97/3 wt. %. A single glass transition temperatures was observed for all PLA/PVA blends, suggesting the formation of binary compatible blends at concentration range studied. Thermogravimetric analysis results showed a better thermal stability for PLA/PVA blends containing PVA of higher Mw and HD. According to mechanical properties, low quantities of PVA (3 wt. %) do not affect the tensile strength of blends (irrespective of Mw and HD). However, as the PVA content increases, tensile strength tends to lower values, especially for blends with 20 wt.% of PVA, with 98% of HD.

The pyrolysis kinetics of primary, secondary, and tertiary p-hydroxy ketones have been studied in static seasoned vessels over the pressure range of 21-152 torr and the temperature range of 190"-260°C. These eliminations are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are expressed by the following equations: for l-hydroxy-3-butanone, log k l ( s -' ) = (12.18 2 0.39) -(150.0 ? 3.9) k J mol-' (2.303RT)-'; for 4-hydroxy-2-pentanone, log k l ( s -' ) = (11.64 ? 0.28) -(142.1 ? 2.7) k J mol-' (2.303RT)-'; and for 4-hydroxy-4-methyl-2-pentanone, log k 1 k -l ) = (11.36 ? 0.52) -(133.4 -t 4.9) k J mol-' (2.303RT)-'. The acid nature of the hydroxyl hydrogen is not determinant in rate enhancement, but important in assistance during elimination. However, methyl substitution at the hydroxyl carbon causes a small but significant increase in rates and, thus, appears to be the limiting factor in a retroaldol type of mechanism in these decompositions. 0

The present work is focused on the development of polylactic acid/ZnO (PLA/ZnO) polymer nanocomposite through a melt blending route. Previously, the ZnO nanoparticles were coated with polyvinyl alcohol (PVA) via a solvothermal method. The morphology of PVA coated ZnO nanostructures and the formation of polymer nanocomposites were identified through transmission electron microscopy analysis. Thermogravimetric analysis showed that PVA coated ZnO(c) nanoparticles incorporated into the PLA matrix exhibited better thermal stability, suggesting that PVA could be acting as a strong stabilizing agent for ZnO nanoparticles. The tensile strength, elastic modulus, strain at maximum strength and the maximum strain were extracted through stress-strain relations.

High-throughput sequencing produces an extraordinary amount of genomic data that is organized into a number of high-dimension datasets. Accordingly, visualization of genomic data has become essential for quality control, exploration, and data interpretation. The Variant Call Format (VCF) is a text file format generated during the variant calling process that contains genomic information and locations of variants in a group of sequenced samples. The current workflow for visualization of genomic variant data from VCF files requires use of a combination of existing tools. Here, we describe VIVA (VIsualization of VAriants), a command line utility and Jupyter Notebook based tool for evaluating and sharing genomic data for variant analysis and quality control of sequencing experiments from VCF files. VIVA combines the functionality of existing tools into a single command to interactively evaluate and share genomic data, as well as create publication quality graphics.