Antimicrobial sand via adsorption of cationic Moringa oleifera protein

Moringa oleifera (Moringa) seeds contain a natural cationic protein (MOCP) that can be used as an antimicrobial flocculant for water clarification. Currently, the main barrier to using Moringa seeds for producing potable water is that the seeds release other water-soluble proteins and organic matter, which increase the concentration of dissolved organic matter (DOM) in the water. The presence of this DOM supports the regrowth of pathogens in treated water, preventing its storage and later use. A new strategy has been established for retaining the MOCP protein and its ability to clarify and disinfect water while removing the excess organic matter. The MOCP is first adsorbed and immobilized onto sand granules, followed by a rinsing step wherein the excess organic matter is removed, thereby preventing later growth of bacteria in the purified water. Our hypotheses are that the protein remains adsorbed onto the sand after the functionalization treatment, and that the ability of the antimicrobial functionalized sand (f-sand) to clarify turbidity and kill bacteria, as MOCP does in bulk solution, is maintained. The data support these hypotheses, indicating that the f-sand removes silica microspheres and pathogens from water, renders adhered Escherichia coli bacteria nonviable, and reduces turbidity of a kaolin suspension. The antimicrobial properties of f-sand were assessed using fluorescent (live-dead) staining of bacteria on the surface of the f-sand. The DOM that can contribute to bacterial regrowth was shown to be significantly reduced in solution, by measuring biochemical oxygen demand (BOD). Overall, these results open the possibility that immobilization of the MOCP protein onto sand can provide a simple, locally sustainable process for producing storable drinking water.     

Possible effects of oxygen in Te-rich Σ3 (112) grain boundaries in CdTe

Using density functional theory calculation, we show that oxygen (O) exhibits an interesting effect in CdTe. The Te atoms with dangling bonds in a Te-rich rich Σ3 (112) grain boundary (GB) create deep gap states due to strong interaction between Te atoms. However, when such a Te atom is substituted by an O atom, the deep gap states can be shifted toward the valence band, making the site no longer a harmful non-radiative recombination center. We find that O atoms prefer energetically substituting these Te atoms and induce significant lattice relaxation due to their smaller atomic size and stronger electronegativity, which effectively reduces the anion–anion interaction. Consequently, the deep gap states are shifted to lower energy regions close to or even below the top of the valence band.     

Experimental Study of Water Injection into Geothermal Systems

Water injection or reinjection in geothermal reservoirs has been proven as a successful engineering technique with many benefits such as maintaining reservoir pressure and sustaining well productivity. However, many questions related to water injection into geothermal reservoirs still remain unclear; for example, how the in-situ water saturation changes with reservoir pressure and temperature, and how the reservoir pressure influences well productivity. In order to answer these questions, we studied the effects of temperature and pressure on the in-situ water saturation in a core sample using an experimental apparatus developed in this study. It was found that the in-situ water saturation decreases very sharply near the saturation pressure but not to the residual water saturation. When the mean pressure in the core sample decreases further, the in-situ water saturation decreases sharply again to the residual water saturation. Also investigated were the effects of pressure on well productivity index. We found that well productivity increased with an increase of mean reservoir pressure within a certain range and then decreased. The well productivity reached the maximum value at a pressure close to the saturation pressure. The results of this study may be useful to evaluate projects such as the waste water injection scheme at The Geysers.     

A study of the crystallinity index of polypropylene fibres

Crystallinity measurements were carried out with the help of X-ray diffraction, differential scanning calorimetry (DSC) and density measurements. The results of this study provide a better understanding of the morphology and complex thermal behaviour of polypropylene fibres. Crystallinity studies show that the crystallinity of PP fibres when measured by X-ray and DSC methods as a function of draw-ratios increases with increasing draw-ratios while the crystallinity of the same samples as derived by density measurements shows an inverse trend. These discrepancies are accounted for by the formation of microvoids within the polypropylene fibres due to drawing. In the DSC scan two endothermic peaks were found to occur in some of the samples. This is explained by the presence of two morphological forms i. e. lamellar and fibrillar morphology in the same sample. The crystallinity values obtained from different methods are correlated with mechanical properties, such as tenacity and elongations.Dedicated to Prof. Dr. H. Janeschitz-Kriegl, a pioneer of Polymer Physics in Austria, in honour of his sixtieth birthday.     

Niobium Doping in BiVO4: Interplay Between Effective Mass,Stability, and Pressure

We have applied density functional theory to study the electronic structure changes caused by Nb incorporation in BiVO₄ and the application of external pressure. The overall solubility of Nb in BiVO₄ is usually high, and the presence of oxygen vacancies affect the dopability of Nb in BiVO₄. Through the analyses of the chemical-potential landscape, we have determined the single-phase stability zone of BiVO₄ with the Nb doping. The most favorable Nb doping is simultaneous substitutions at both V- and Bi-sites. Even though Nb substitution at only V-site is next favorable, the band gap change is not very significant which agrees with an earlier experiment. However, it does change the electron effective mass by 20 % owing to the presence of Nb 4d bands in the conduction bands, which explains better catalytic activity by Nb-doped BiVO₄. In addition, application of external pressure the single-phase stability zone in the chemical-potential landscape. We have also focused on the local structural distortions near the Nb doping site, especially on the BiO₈ octahedra. We have shown here that pressure-induced symmetrization of BiO₈ dodecahedron lowers the electron's effective mass further and therefore can help to improve the photoconduction property of BiVO₄.     

ChemInform Abstract: Band Edge Electronic Structure of BiVO4: Elucidating the Role of the Bi s and V d Orbitals.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Minimax second-order designs over cuboidal regions for the difference between two estimated responses

Minimization of the variance of the difference between estimated responses at two points, maximized over all pairs of points in the factor space, is taken as the design criterion. Optimal designs under this criterion are derived, via a combination of algebraic and numerical techniques, for the full second-order regression model over cuboidal regions. Use of a convexity argument and a surrogate objective function significantly reduces the computational burden.     

Density functional study of O2 adsorption on (100) surface of γ‐uranium

Chemisorption of the oxygen molecule on the (100) surface of γ‐uranium was investigated using the generalized gradient approximation to Density Functional Theory. Dissociative adsorptions of O₂ are found to be significantly favored compared to molecular adsorptions. Interstitial adsorptions of molecular oxygen are less probable, as no bound states are found in this case. Only after dissociation of O₂ is atomic oxygen diffusion through the surface possible. The O 2p orbitals are found to hybridize with U 5f bands, and some of the U 5f electrons become more localized. A significant charge transfer from the first layer of the uranium surface to the oxygen atoms is found to occur, making the bonding partly ionic. For the most favored site, the dissociative chemisorption energy is ～9.5 eV, which indicates a strong reaction of uranium surface with oxygen. Spin polarization does not have a significant effect on the chemisorption process. For most of the sites and approaches, chemisorption configurations are almost same for both spin‐polarized and non‐spin‐polarized cases. For the most favored chemisorption sites of oxygen on uranium, paramagnetic adsorption is slightly stronger, by 0.304 eV, compared to magnetic adsorption. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Ab initio study of molecular oxygen adsorption on Pu (111) surface

Using the generalized gradient approximation to density functional theory (DFT), molecular and dissociative oxygen adsorptions on a Pu (111) surface has been studied in detail. Dissociative adsorption with a layer‐by‐layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable, and adsorption of oxygen does not change this feature. Hor1 (O₂ is parallel to the surface and lattice vectors) approach on the center2 (center of the unit cell, where there is a Pu atom directly below on the third layer) site, both without and with spin polarization, was found to be the preferred chemisorbed site among all cases studied with chemisorption energies of 8.365 and 7.897 eV, respectively. The second‐highest chemisorption energy occurs at the Ver (O₂ is vertical to the surface) approach of the bridge site with chemisorption energies of 8.294 eV (non‐spin‐polarized) and 7.859 eV (spin‐polarized), respectively. We find that 5f electrons are more localized in the spin‐polarized case than the non‐spin‐polarized counterparts. Localization of the 5f electrons is higher in the oxygen‐adsorbed plutonium layers compared with the bare layers. The ionic part of O? Pu bonding plays a significant role in the chemisorption process, along with Pu 5f? O 2p hybridization. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

On the QoS for ATM Networks Using a New Buffer Utilization Technique

A buffer sharing scheme need to meet many competing objectives like robustness to changes in traffic conditions,fairness, efficiency, implementation simplicity, etc. Of the existing techniques, Push Out (PO) is optimum in terms of overall cell loss performance, but its delay performance is worse than that of all other methods for the multiple space priority. Another scheme named Dynamic Threshold (DT) is robust and adaptive which has good delay performance. A hybrid technique named Dynamic Threshold with native Push Out (DnP) shows the best delay performance but its loss performance is worse specially for higher priority traffic. A novel policy called Balanced Buffer Push Out (BBPO) is proposed here that aims to achieve a better loss performance than DT and better delay performance than PO for multipriority traffic. Using computer simulation the loss performance and delay performance of DT, PO, DnP and BBPO are measured for bursty traffic, and a comparison of the results is presented. The proposed scheme exhibits the best loss performance on an average among all the schemes. Although for higher priority traffic the loss performance of PO is better than that of BBPO, the delay performance of BBPO is better than that of PO.