Development and application of the incident command tool for drinking water protection

The Incident Command Tool for Drinking Water Protection (ICWater) provides real‐time assessments of the travel and dispersion of contaminants in streams and rivers. It is structured around the RiverSpill model which has been enhanced to make use of the 1:100 000 scale National Hydrography Dataset Plus, Version 1.0 (NHDPlusV1). NHDPlusV1 is a hydrologically connected river network that contains over 3 million reach segments in the United States. This allows for both downstream and upstream tracing (which serves in forensic analysis). Mean flow and velocity have been calculated by the US Geological Survey (USGS) and Environmental Protection Agency (EPA) for each reach. These mean values are updated by flow from web accessible real‐time gauging stations. Example databases available within ICWater include: dams, reservoirs, water supplies, gauges, municipal and industrial dischargers and transportation networks. A contaminant database is also included which identifies biological, chemical and radiological contaminants and their toxicities. Navigating the river network upstream coupled with mass‐balance calculations from breakthrough curves allows for backtracking of the contamination to determine the origin and source strength.     

The photo-electrochemical studies of Eu doped yttrium orthovanadate–zinc oxide–reduced graphene oxide nanohybrid

A new class of nanostructured photo-electrocatalyst Eu³⁺ doped yttrium orthovanadate–zinc oxide–reduced graphene oxide (YVO₄:Eu³⁺–ZnO–RGO) nanohybrid was developed by a simple electrostatic self-assembly at room temperature, using ZnO, YVO₄:Eu³⁺ and RGO as building blocks. Interaction among YVO₄:Eu³⁺, ZnO and RGO is indicated by variation in hydrodynamic diameter (H_D) and zeta potentials of the products as compared to their individual components, thus suggesting that YVO₄:Eu³⁺–ZnO–RGO is a nanohybrid and not a physical mixture. Electrochemical response of this nanohybrid towards the redox couple of Fe(CN)₆^3−/4− was investigated before and after UV irradiation. Apart from quenching of the green emission of ZnO in photoluminescence spectrum, which serves as a probe to monitor the interfacial electron transfer from excited ZnO to RGO, degradation in electrochemical redox process provides an additional path to monitor interfacial electron transfer.     

Kaposi's sarcoma-associated herpes virus--a new concern for human reproduction?

The detection of the recently discovered Kaposi's sarcoma-associated herpes virus (KSHV) in human immunodeficiency virus-uninfected donor semen and in blood from a normal blood donor has led us to review this new area of health concern, with emphasis on a number of studies conducted into the presence of the virus in semen and the possibility of transmission during assisted conception procedures.     

Quantifying the accessible surface area of protein residues in their local environment

The quantification of the packing of residues in proteins anddocking of ligands to macromolecules is important in understandingprotein stability and drug design. The number of atoms in contact(within a distance of 4.5 Å) can be used to describe thelocal environment of a residue. As this number increases, theaccessible surface area (ASA) of the residue decreases exponentiallyand the variation can be described in terms of an exponentialequation of the form y = a₁exp(–x/a₂), each residue havingits own set of parameters a₁ and a₂, which also depend on whetherthe whole residue or just the side chain is considered. Hydrophobicand hydrophilic residues can be distinguished on the basis ofboth the average number of surrounding atoms and the variationof ASA. For a given number of partner atoms, a comparison ofthe observed ASA with the expected value obtained from the equationprovides a method of assessing the goodness of packing of theresidue in a protein structure or its importance in the bindingof a ligand. The equation provides a method to estimate theASA of a protein molecule and the average relative accessibilitiesof different residues, the latter being inversely correlatedwith hydrophobicity values.     

Efficient photon-to-electron conversion with rhodamine 6G-sensitized nanocrystalline n-ZnO thin film electrodes in acetonitrile solution

This work encompasses a study of the photosensitizing action of the commercially available laser dye rhodamine 6G (Rh 6G) on nanocrystalline n-ZnO thin film electrodes prepared by sol–gel technique. This dye, having strong absorption in the visible range with a pronounced absorption peak at 525 nm, was found to convert into electrical energy the visible light in the range of 450–560 nm. The electron injection by photo-excited dye molecules into the conduction band of ZnO was evidenced by the matching of the action spectrum of dye-capped ZnO electrode with the absorption spectrum of the dye in solution. The maximum incident photon-to-current conversion efficiency (IPCE) of Rh 6G-sensitized ZnO based cell was found to be 2.3% at 520 nm under short-circuit condition, which is nearly 1.5 times the IPCE value reported for Rh 6G-sensitized SnO₂ based cell. Dependence of the photocurrent on light intensity and the stability of the photocurrent obtainable from the Rh 6G-sensitized ZnO based photoelectrochemical cell on its prolong operation were also determined. On irradiation of the semiconductor electrode with monochromatic light (λ=520 nm), the power conversion efficiency (η) of the (ZnO electrode/ Rh 6G—containing electrolyte/carbon electrode) cell was found to be 0.2% with fill factor value of 0.44. Open-circuit photovoltage up to 500 mV could be obtained with this cell under visible (λ>420 nm) and white lights illumination.     

Mixed Micellization Study of Alkyltrimethylammonium and Alkyltriphenylphosphonium Bromides in Aqueous Solution

Mixed micellization study of cationic surfactants viz. alkyltrimethylammonium bromides (C_nTAB) and alkyltriphenylphosphonium bromides (C_nTPPB) with similar hydrophobic groups (C₁₂-, C₁₄-, and C₁₆-) was performed using tensiometry and UV–visible light spectrophotometry techniques. Critical micelle concentration (CMC) values of the single and binary surfactant mixtures were obtained from a plot of surface tension versus the logarithm of surfactant concentration (C _s). The degree of synergy and various mixed micelle parameters like interaction parameter (β), activity coefficients (f ^m ) and interfacial parameters like surface pressure (π _CMC), packing parameter (P), surface excess concentration (Г _max), surface tension at the CMC (γ _CMC), and minimum area per molecule (A _min) were evaluated using the regular solution theory (RST). Thermodynamic parameters were calculated using several proposed models which suggest the mixed micellar system to be more thermodynamically stable than their respective individual components. In addition, a dye solubilization study was performed using a spectrophotometric method to validate the CMC data obtained from tensiometric method. Conductometric measurements were also carried out for the mixture of C₁₂TAB + C₁₂TPPB only as it showed a more negative β, indicating a higher degree of synergism.     

Smallholders’ access to agricultural credit in Pakistan

The Government of Pakistan has implemented a policy of food security for smallholders by making provision of credit needed for purchasing inputs such as farm machinery, fertilizer and seed. This study analyzed access to and adequacy of credit for smallholders with landholdings up to 5 acres (= 2 ha), using primary data collected through a survey of 208 households, focus-group discussions and unstructured interviews. The findings revealed a partial success of the national credit policy in terms of the proportion of households having access to formal credit but appeared less successful when this was compared with the total amount of credit demanded and obtained. Among the three types of smallholders compared, i.e. lower-smallholders (≤1.0 acre), middle-smallholders (1.01–2.50 acres) and upper-smallholders (2.51–5.00 acres), the lower-smallholders obtained least benefit from the policy as reflected in the formal credit accounting for 12% of the total credit obtained and only 6% of the total credit demanded. The other two types of smallholders had relatively better access to formal credit. Due to a lack of access to adequate formal credit, informal sources have continued to play a major role in the credit market. The causes for this are explained and relevant policy recommendations are made for improving smallholders’ access to credit in the study area and elsewhere in Pakistan. It is hoped that the findings of this study will make a useful contribution to the understanding and remedying of the difficulties that smallholders experience in obtaining credit which may be of value not only in Pakistan but in other developing countries.