Synthesis and water absorbency of crosslinked superabsorbent polymers

A series of novel copolymer superabsorbents based on monomer acrylamide (AM), potassium methacrylate (KMA), and 2‐hydroxyethyl methacrylate (HEMA) were prepared by copolymerization using ammonium persulfate (APS) as an initiator and N,N‐methylenebisacrylamide (MBA) as a crosslinking agent. The synthetic variables (the monomer concentration, crosslinker concentration, and initiator concentration) were also studied. The experimental results of superabsorbent polymers (SAPs) show a better absorbency in both water and NaCl solutions. The copolymers were characterized by IR spectroscopy. The water retention in the soil was enhanced using the above superabsorbents. The use of SAPs for the growth of groundnut plants was also investigated. SAPs can be considered for water‐managing materials for agriculture and horticulture purposes in desert and drought‐prone areas. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1795–1801, 2002     

Protein engineering of alcohol dehydrogenases; effects of amino acid changes at positions 93 and 48 of yeast ADH1

By protein engineering we have investigated changes to two aminoacid residues (Trp93 and Ser48) in the substrate pocket of yeastalcohol dehydrogenase 1. Upon changing Thr48 to serine we producedan enzyme which has markedly greater activity towards aliphaticalcohols with chain length up to 8, together with a generalincrease in catalytic activity (V/K). Changes at position 93were less pronounced, with the Phe enzyme being more activethan the parent towards the range of alcohols but with the alanineenzyme showing very little difference from the wild-type. Enzymeswith the double changes at 48 and 93 showed increased activitytowards alcohols with 3–8 carbons but the increases werenot additive over the single changes. The enzymes with changesat the two positions would metabolize both stereoisomers of2-octanol whereas the parent ADH would attack only one of them.None of the engineered enzymes would attack cyclohexanol oraromatic alcohols. The results are in general agreement withthe prediction that reducing the size of amino acids in thesubstrate pocket would enhance the ability to oxidize alcoholslarger than ethanol.     

The impact of multi‐group multi‐layer network structure on the performance of distributed consensus building strategies

We consider a structural approach to the consensus building problem in multi‐group multi‐layer (MGML) distributed sensor networks (DSNs) common in many natural and engineering applications. From among the possible network structures, we focus on bipartite graph structure as it represents a typical MGML structure and has a wide applicability in the real world. We establish exact conditions for consensus and derive a precise relationship between the consensus value and the degree distribution of nodes in a bipartite MGML DSN. We also demonstrate that for subclasses of connectivity patterns, convergence time and simple characteristics of network topology can be captured by explicit algebra. Direct inference of the convergence behavior of consensus strategies from MGML DSN structure is the main contribution of this paper. The insights gained from our analysis facilitate the design and development of large‐scale DSNs that meet specific performance criteria. Copyright © 2012 John Wiley & Sons, Ltd.     

Multiple evolutionary origins of the fungus causing Panama disease of banana: concordant evidence from nuclear and mitochondrial gene genealogies

Panama disease of banana, caused by the fungus Fusarium oxysporum f. sp. cubense, is a serious constraint both to the commercial production of banana and cultivation for subsistence agriculture. Previous work has indicated that F. oxysporum f. sp. cubense consists of several clonal lineages that may be genetically distant. In this study we tested whether lineages of the Panama disease pathogen have a monophyletic origin by comparing DNA sequences of nuclear and mitochondrial genes. DNA sequences were obtained for translation elongation factor 1alpha and the mitochondrial small subunit ribosomal RNA genes for F. oxysporum strains from banana, pathogenic strains from other hosts and putatively nonpathogenic isolates of F. oxysporum. Cladograms for the two genes were highly concordant and a partition-homogeneity test indicated the two datasets could be combined. The tree inferred from the combined dataset resolved five lineages corresponding to "F. oxysporum f. sp. cubense" with a large dichotomy between two taxa represented by strains most commonly isolated from bananas with Panama disease. The results also demonstrate that the latter two taxa have significantly different chromosome numbers. F. oxysporum isolates collected as nonpathogenic or pathogenic to other hosts that have very similar or identical elongation factor 1alpha and mitochondrial small subunit genotypes as banana pathogens were shown to cause little or no disease on banana. Taken together, these results indicate Panama disease of banana is caused by fungi with independent evolutionary origins.     

Mapping of groundwater potential zones in the Musi basin using remote sensing data and GIS

The objective of this study is to explore the groundwater availability for agriculture in the Musi basin. Remote sensing data and geographic information system were used to locate potential zones for groundwater in the Musi basin. Various maps (i.e., base, hydrogeomorphological, geological, structural, drainage, slope, land use/land cover and groundwater prospect zones) were prepared using the remote sensing data along with the existing maps. The groundwater availability of the basin is qualitatively classified into different classes (i.e., very good, good, moderate, poor and nil) based on its hydrogeomorphological conditions. The land use/land cover map was prepared for the Kharif season using a digital classification technique with the limited ground truth for mapping irrigated areas in the Musi basin. The alluvial plain in filled valley, flood plain and deeply buried pediplain were successfully delineated and shown as the prospective zones of groundwater.     

Strictly positive-definite spike train kernels for point-process divergences

Exploratory tools that are sensitive to arbitrary statistical variations in spike train observations open up the possibility of novel neuroscientific discoveries. Developing such tools, however, is difficult due to the lack of Euclidean structure of the spike train space, and an experimenter usually prefers simpler tools that capture only limited statistical features of the spike train, such as mean spike count or mean firing rate. We explore strictly positive-definite kernels on the space of spike trains to offer both a structural representation of this space and a platform for developing statistical measures that explore features beyond count or rate. We apply these kernels to construct measures of divergence between two point processes and use them for hypothesis testing, that is, to observe if two sets of spike trains originate from the same underlying probability law. Although there exist positive-definite spike train kernels in the literature, we establish that these kernels are not strictly definite and thus do not induce measures of divergence. We discuss the properties of both of these existing nonstrict kernels and the novel strict kernels in terms of their computational complexity, choice of free parameters, and performance on both synthetic and real data through kernel principal component analysis and hypothesis testing.     

X-ray and ion emission characteristics of plasmas ablated from solid materials using a high power Nd:Glass laser

X-ray and ion emissions from high temperature plasmas from solid targets with different atomic numbers have been studied. Plasma is generated using a high power Nd:Glass laser generating focused intensity in the range of 10¹² to 10¹³ Watts/cm² on targets. Plasma temperature is typically between 50 to 100 eV. X-ray emission scaling as a function of laser intensity as well as ion velocity has been measured in these targets. Non-uniform plasma expansion and generation of fast ions are observed for targets with higher atomic numbers.     

Thiobacillus denitrificans immobilized biotrickling filter for NO2 removal

Nitrogen dioxide (NO₂) removal efficiency of a biotrikling filter was evaluated under different operating conditions. Activated alumina (AA) was used as the immobilization matrix for Thiobacillus denitrificans (T. denitrificans) in the biotrickling filter. Batch studies were conducted to find out the degradation kinetics of nitrate and nitrite for a concentration range of 600–10,000 mg/L expressed as nitrogen. Nitrite exhibited maximum degradation rate followed by nitrate. Electron acceptor in the form of NO₂ gas showed least removal efficiency. Bio-kinetic parameters for T. denitrificans, by utilizing nitrate and nitrite as electron acceptors, were also evaluated. The μ_max (Maximum specific growth rate) and Y_T (Yield coefficient) values for T. denitrificans in the presence of nitrate and nitrite were 1.03 h⁻¹, 0.275 and 0.63 h⁻¹, 0.1316 respectively. Column study was conducted to find the adsorption and desorption potential of activated alumina. The adsorbed NO₂ from AA could easily be desorbed using distilled water with an efficiency of 76±0.8%. Once fed batch studies were conducted to evaluate the NO₂ removal efficiency by a biotrickling filter. With an influent NO₂ gas concentration of 2,735 ppm, the reactor could achieve a removal efficiency of 99% within 2 min from gas phase and within 96 h from the liquid phase, with an average biomass concentration of 200 mg/g of AA. The mechanism of NO₂ gas removal in the biotrickling filter seems to be the dissolution of NO₂ in water to form NO₃⁻, conversion of NO₃⁻ to NO₂ ⁻, and finally to N₂ gas.     

Optimization of tensile properties thermoplastic blends from soy and biodegradable polyesters: Taguchi design of experiments approach

Soy meal-based biodegradable blends were prepared by melt extrusion process. The effects of denaturants, i.e., urea and sodium sulfite and plasticizer (glycerol) and polyester type (polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate) on tensile strength and elongation at break were investigated using a Taguchi experimental design approach. The results showed that the sodium sulfite had little or no effect on final properties of the blends. Also, biodegradable polyester type had significant effect on the tensile strength and elongation at break of the blends prepared. The predicted values and experimental were found to be in tune with each other. The chemical structure and morphology of the optimum sample was probed by FT-IR spectroscopy and scanning electron microscopy (SEM). Also, the results provided an insight into how important the plasticization and destructurization of soy protein to obtain the blends with desired mechanical properties.