A Repair Framework for Scalar MDS Codes

Several works have developed vector-linear maximum-distance separable (MDS) storage codes that min- imize the total communication cost required to repair a single coded symbol after an erasure, referred to as repair bandwidth (BW). Vector codes allow communicating fewer sub-symbols per node, instead of the entire content. This allows non trivial savings in repair BW. In sharp contrast, classic codes, like Reed- Solomon (RS), used in current storage systems, are deemed to suffer from naive repair, i.e. downloading the entire stored message to repair one failed node. This mainly happens because they are scalar-linear. In this work, we present a simple framework that treats scalar codes as vector-linear. In some cases, this allows significant savings in repair BW. We show that vectorized scalar codes exhibit properties that simplify the design of repair schemes. Our framework can be seen as a finite field analogue of real interference alignment. Using our simplified framework, we design a scheme that we call clique-repair which provably identifies the best linear repair strategy for any scalar 2-parity MDS code, under some conditions on the sub-field chosen for vectorization. We specify optimal repair schemes for specific (5,3)- and (6,4)-Reed- Solomon (RS) codes. Further, we present a repair strategy for the RS code currently deployed in the Facebook Analytics Hadoop cluster that leads to 20% of repair BW savings over naive repair which is the repair scheme currently used for this code.Comment: 10 Pages; accepted to IEEE JSAC -Distributed Storage 201

High pressure pyrolyzed non-precious metal oxygen reduction catalysts for alkaline polymer electrolyte membrane fuel cells

Non-precious metal catalysts, such as metal-coordinated to nitrogen doped-carbon, have shown reasonable oxygen reduction reaction (ORR) performances in alkaline fuel cells. In this report, we present the development of a highly active, stable and low-cost non-precious metal ORR catalyst by direct synthesis under autogenic-pressure conditions. Transmission electron microscopy studies show highly porous Fe-N-C and Co-N-C structures, which were further confirmed by Brunauer-Emmett-Teller surface area measurements. The surface areas of the Fe-N-C and Co-N-C catalysts were found to be 377.5 and 369.3 m2 g-1, respectively. XPS results show the possible existence of N-C and M-Nx structures, which are generally proposed to be the active sites in non-precious metal catalysts. The Fe-N-C electrocatalyst exhibits an ORR half-wave potential 20 mV higher than the reference Pt/C catalyst. The cycling durability test for Fe-N-C over 5000 cycles shows that the half-wave potential lost only 4 mV, whereas the half-wave potential of the Pt/C catalyst lost about 50 mV. The Fe-N-C catalyst exhibited an improved activity and stability compared to the reference Pt/C catalyst and it possesses a direct 4-electron transfer pathway for the ORR process. Further, the Fe-N-C catalyst produces extremely low HO2- content, as confirmed by the rotating ring-disk electrode measurements. In the alkaline fuel single cell tests, maximum power densities of 75 and 80 mW cm-2 were observed for the Fe-N-C and Pt/C cathodes, respectively. Durability studies (100 h) showed that decay of the fuel cell current was more prominent for the Pt/C cathode catalyst compared to the Fe-N-C cathode catalyst. Therefore, the Fe-N-C catalyst appears to be a promising new class of non-precious metal catalysts prepared by an autogenic synthetic method. © The Royal Society of Chemistry 2015.

Enhanced alpha-amylase production using Streptomyces gancidicus ASD by process optimization

845-852The present study was focused on purification and optimization of amylase from marine actinomycetes. Among 101 actinomycetes isolates from Andaman & Nicobar islands, Streptomyces sp gancidicus_ASD was isolated and further studied. The enzyme activity was studied at various physical parameters like temperature, pH, carbon source, Nitrogen source, metal ions, NaCl concentration etc. by maintaining all the factors with 100 ml of crude extract. Also, media optimization with response surface methodology was used to ameliorate the bioprocess economics. A central composite design was conducted to optimize the four selected factors. Statistical analyses of the data of model fitting were done by using Design expert 10.0 (stat-Ease). Results show a maximum predicted amylase yield of 11460.34 IU/ml when using 1.05% sucrose, 0.608% beef extract, 7.1 pH and 40.35 °C temperature. The predicted value is approximately 1.24-fold much higher than the original production (9248 IU/mL) determined by the conventional one-factor-at-a-time optimization method which can be applied in bioprocess for increased amylase yield

ANTICANCER ACTIVITY OF POLYMERIC NANOPARTICLES CONTAINING ETOPOSIDE USING ALBINO RATS AS EXPERIMENTAL ANIMAL MODEL

Objective: Etoposide is a potent anticancer drug and a major limiting factor that hinders therapeutic use as its high levels of systemic circulation often associated with various off-target effects, particularly cardiotoxicity. The present study focuses on the evaluation of the anticancer activity of optimized etoposide nanoparticles compared with marketed etoposide formulation in experimental animal models.Methods: Albino rats (180–200 g) were used for the study. The anticancer effect of the formulated etoposide nanoparticles was evaluated by induction of hepatocellular carcinoma (HCC). The animals housed in cages and kept on a 12 h light/dark cycle. Following the acclimatization for 1 week, HCC will be induced in rats by adding 100 mg/L of diethylnitrosamine (DENA) in drinking water for 8 weeks. Drug treatment (etoposide [9 mg/kg] in 0.5 % carboxymethyl cellulose; p.o.) can be started at the end of 1 week after cancer induction and dose of 9 mg/kg of etoposide and lyophilized nanoparticles will be administered through oral route on 1, 7, 14, 21, and 28 days. Nanoformulations were evaluated in healthy rats, and anticancer activity was studied in DENA treated rats.Results: The results showed that the polymeric nanoparticles containing etoposide was screened for its anticancer activity by counting the liver nodules of rats with hematoxylin and eosin stain when comparing control and etoposide-treated group.Conclusion: The results of the study concluded that in rats treated with nanoformulations, the numbers of liver nodules were found to be significantly reduced

Gender-Related Differential Item Functioning of Mathematics Computation Items among Non-native Speakers of English

This study aimed at determining the presence of gender Differential Item Functioning (DIF) for mathematics computation items among non-native speakers of English, and thus examining the relationship between gender DIF and characteristics of mathematics computation items. The research design is a comparative study, where the boys form the reference group and the girls form the focal group. The software WINSTEPS, which is based on the Rasch model was used. DIF analyses were conducted by using the Mantel-Haenszel chi-square method with boys forming the reference group and girls forming the focal group. A total of 988 boys and 1381 girls in form two were selected from 34 schools, with 17 schools located in the Penang island, 12 schools in Penang mainland and five schools in Perak. Some 20 items were selected from the grade eight TIMSS 1999 and TIMSS 2003 released mathematics items. Findings revealed that seven items were flagged as DIF, where two were of moderate DIF and one as large DIF. Two DIF items assessed combined operation from the topics of fraction and negative numbers in the Number domain and the cognitive domain of lower-order thinking skills of Knowing favoured girls. One moderate DIF which assessed higher order thinking skills of Applying from the Algebra domain favoured boys. The findings trigger a possibility that computation items with one step operation, which assess lower-order thinking skills favour girls, while items that assess higher-order thinking skills favour boys