Padé approach to potential transients: Part 1. Electron transfer without and with coupling to first-order homogeneous reactions at planar electrodes

Potential transients are obtained by using “Padé approximants” (an accurate approximation procedure valid globally — not just perturbatively) for all amplitudes of concentration polarization and current densities. This is done for several mechanistic schemes under constant current conditions. We invert the non-linear current-potential relationship in the form (using the Lagrange or the Ramanujan method) of power series appropriate to the two extremes, namely near reversible and near irreversible. Transforming both into the Pad́e expressions, we construct the potential-time profile by retaining whichever is the more accurate of the two. The effectiveness of this method is demonstrated through illustrations which include couplings of homogeneous chemical reactions to the electron-transfer step.

Chemical potential of oxygen for iron-rutile-ilmenite and iron-ilmenite-ulvospinel equilibria

The chemical potential of oxygen corresponding to the iron-rutile-ilmenite (IRI) and iron-ilmenite-ulvospinel (IIU) equilibria has been measured employing solid-state galvanic cells,$$Pt, Fe + TiO_2 + FeTiO_3 //(Y_2 O_3 ) ZrO_2 //Fe + FeO, Pt$$ and $${\text{Pt, Fe + FeTiO}}_{\text{3}} {\text{ + Fe}}_{\text{2}} {\text{TiO}}_{\text{4}} {\text{//(Y}}_{\text{2}} {\text{0}}_{\text{3}} {\text{) ZrO}}_{\text{2}} {\text{//Fe + FeO, Pt}}$$ in the temperature range of 875 to 1275 K and 900 to 1373 K, respectively. The cells are written such that the right-hand electrodes are positive. The electromotive force (emf) of both the cells was found to be reversible and to vary linearly with temperature over the entire range of measurement. The chemical potential of oxygen for IRI equilibrium is represented by Δμo2(IRI) = -550,724 - 29.445T + 20.374T InT(±210) J mol−1 (875 <-T<- 1184 K) = -620,260 + 369.593T - 27.716T lnT(±210) J mol−1 (1184 <-T<- 1275 K) and that for IIU equilibrium by Δμo2(IIU) = -501,800 - 49.035T + 20.374T lnT(±210) J mol−1 (900 <-T<- 1184 K) = -571,336 + 350.003T− 27.716T lnT(=−210) J mol-1 (1184 <-T<- 1373 K) The standard Gibbs energy changes for IRI and IIU equilibria have been deduced from the measured oxygen potentials. Since ilmenite contains small amounts of Ti³+ ions, a correction for the activity of FeTiO3 has been incorporated by assuming ideal mixing on each cation sublattice in the FeTiO3-Ti2O3 system. Similarly, the ulvospinel contains some Fe³+ ions and a correction for the activity of Fe2TiO4 has been included by modeling the Fe2TiO4-Fe3O4 system. The third-law analysis of the results obtained for IRI equilibrium gives ΔH 298 0 = -575 (±1.0) kJ mol-1 and for IIU equilibrium yields ΔH 298 0 = -523.7 (±0.7) kJ mol−1}. The present results suggest that Fe2+ and Ti4+ cations mix almost ideally on the octahedral site of spinel lattice in Fe2TiO4, giving rise to a configurational contribution of 2R In 2 (11.5256 J mol-1 K-1) to the entropy of Fe2TiO4.

Effect of hole localization on Madelung potential of YBa2Cu3O7

The Madelung potential and formation energy of the superconducting compound YBa2Cu3O7 have been computed for hole localization at different sites in the crystal. The cases considered include Cu3+ ion at Cu(1) and Cu(2) sites, O− ion at O(1), O(2), O(3) and O(4) sites and combinations of O− and Cu3+ ions at O(4) and Cu(1) and O(2,3) and Cu(2) sites. The two lowest-energy configurations correspond to Cu3+ ion at Cu(1) site and O− ion at O(4) site. The difference in formation energy between those configurations is relatively small. The next preferred configuration corresponds to simultaneous partial localization of the hole at Cu (1) site and O(1) site. Other configurations are much less stable. The results suggest a resonating or fluctuating valence model for YBa2Cu3O7.

Double helix conformation, groove dimensions and ligand binding potential of a G/C stretch in B-DNA

The self-complementary DNA fragment CCGGCGCCGG crystallizes in the rhombohedral space group R3 with unit cell parameters a = 54.07 angstrom and c = 44.59 angstrom. The structure has been determined by X-ray diffraction methods at 2.2 angstrom resolution and refined to an R value of 16.7%. In the crystal, the decamer forms B-DNA double helices with characteristic groove dimensions: compared with B-DNA of random sequence, the minor groove is wide and deep and the major groove is rather shallow. Local base pair geometries and stacking patterns are within the range commonly observed in B-DNA crystal structures. The duplex bears no resemblance to A-form DNA as might have been expected for a sequence with only GC base pairs. The shallow major groove permits an unusual crystal packing pattern with several direct intermolecular hydrogen bonds between phosphate oxygens and cytosine amino groups. In addition, decameric duplexes form quasi-infinite double helices in the crystal by end-to-end stacking. The groove geometries and accessibilities of this molecule as observed in the crystal may be important for the mode of binding of both proteins and drug molecules to G/C stretches in DNA.

The potential of microbial ecological indicators to guide ecosophisticated management of hydrocarbon-contaminated soils

Soil is an unrenewable natural resource under increasing anthropogenic pressure. One of the main threats to soils, compromising their ability to provide us with the goods and ecosystem services we expect, is pollution. Oil hydrocarbons are the most common soil contaminants, and they disturb not just the biota but also the physicochemical properties of soils. Indigenous soil micro-organisms respond rapidly to changes in the soil ecosystem, and are chronically in direct contact with the hydrophobic pollutants on the soil surfaces. Soil microbial variables could thus serve as an intrinsically relevant indicator of soil quality, to be used in the ecological risk assessment of contaminated and remediated soils. Two contrasting studies were designed to investigate soil microbial ecological responses to hydrocarbons, together with parallel changes in soil physicochemical and ecotoxicological properties. The aim was to identify quantitative or qualitative microbiological variables that would be practicable and broadly applicable for the assessment of the quality and restoration of oil-polluted soil. Soil bacteria commonly react on hydrocarbons as a beneficial substrate, which lead to a positive response in the classical microbiological soil quality indicators; negative impacts were accurately reflected only after severe contamination. Hydrocarbon contaminants become less bioavailable due to weathering processes, and their potentially toxic effects decrease faster than the total concentration. Indigenous hydrocarbon degrader bacteria, naturally present in any terrestrial environment, use specific mechanisms to improve access to the hydrocarbon molecules adsorbed on soil surfaces. Thus when contaminants are unavailable even to the specialised degraders, they should pose no hazard to other biota either. Change in the ratio of hydrocarbon degrader numbers to total microbes was detected to predictably indicate pollutant effects and bioavailability. Also bacterial diversity, a qualitative community characteristic, decreased as a response to hydrocarbons. Stabilisation of community evenness, and community structure that reflected clean reference soil, indicated community recovery. If long-term temporal monitoring is difficult and appropriate clean reference soil unavailable, such comparison could possibly be based on DNA-based community analysis, reflecting past+present, and RNA-based community analysis, showing exclusively present conditions. Microbial ecological indicators cannot replace chemical oil analyses, but they are theoretically relevant and operationally practicable additional tools for ecological risk assessment. As such, they can guide ecologically informed and sustainable ecosophisticated management of oil-contaminated lands.

Identification of collagenolytic MMP networks as potential biomarkers in progressive chronic periodontitis subjects and MMP-8 null allele model

Chronic periodontitis results from a complex aetiology, including the formation of a subgingival biofilm and the elicitation of the host s immune and inflammatory response. The hallmark of chronic periodontitis is alveolar bone loss and soft periodontal tissue destruction. Evidence supports that periodontitis progresses in dynamic states of exacerbation and remission or quiescence. The major clinical approach to identify disease progression is the tolerance method, based on sequential probing. Collagen degradation is one of the key events in periodontal destructive lesions. Matrix metalloproteinase (MMP)-8 and MMP-13 are the primary collagenolytic MMPs that are associated with the severity of periodontal inflammation and disease, either by a direct breakdown of the collagenised matrix or by the processing of non-matrix bioactive substrates. Despite the numerous host mediators that have been proposed as potential biomarkers for chronic periodontitis, they reflect inflammation rather than the loss of periodontal attachment. The aim of the present study was to determine the key molecular MMP-8 and -13 interactions in gingival crevicular fluid (GCF) and gingival tissue from progressive periodontitis lesions and MMP-8 null allele mouse model. In study (I), GCF and gingival biopsies from active and inactive sites of chronic periodontitis patients, which were determined clinically by the tolerance method, and healthy GCF were analysed for MMP-13 and tissue inhibitor of matrix metalloproteinases (TIMP)-1. Chronic periodontitis was characterised by increased MMP-13 levels and the active sites showed a tendency of decreased TIMP-1 levels associated with increments of MMP-13 and total protein concentration compared to inactive sites. In study (II), we investigated whether MMP-13 activity was associated with TIMP-1, bone collagen breakdown through ICTP levels, as well as the activation rate of MMP-9 in destructive lesions. The active sites demonstrated increased GCF ICTP levels as well as lowered TIMP-1 detection along with elevated MMP-13 activity. MMP-9 activation rate was enhanced by MMP-13 in diseased gingival tissue. In study (III), we analysed the potential association between the levels, molecular forms, isoenzyme distribution and degree of activation of MMP-8, MMP-14, MPO and the inhibitor TIMP-1 in GCF from periodontitis progressive patients at baseline and after periodontal therapy. A positive correlation was found for MPO/MMP-8 and their levels associated with progression episodes and treatment response. Because MMP-8 is activated by hypochlorous acid in vitro, our results suggested an interaction between the MPO oxidative pathway and MMP-8 activation in GCF. Finally, in study (IV), on the basis of the previous finding that MMP-8-deficient mice showed impaired neutrophil responses and severe alveolar bone loss, we aimed to characterise the detection patterns of LIX/CXCL5, SDF-1/CXCL12 and RANKL in P. gingivalis-induced experimental periodontitis and in the MMP-8-/- murine model. The detection of neutrophil-chemoattractant LIX/CXCL5 was restricted to the oral-periodontal interface and its levels were reduced in infected MMP-8 null mice vs. wild type mice, whereas the detection of SDF-1/CXCL12 and RANKL in periodontal tissues increased in experimentally-induced periodontitis, irrespectively from the genotype. Accordingly, MMP-8 might regulate LIX/CXCL5 levels by undetermined mechanisms, and SDF-1/CXCL12 and RANKL might promote the development and/or progression of periodontitis.

CO2-fertilization and potential future terrestrial carbon uptake in India

There is huge knowledge gap in our understanding of many terrestrial carbon cycle processes. In this paper, we investigate the bounds on terrestrial carbon uptake over India that arises solely due to CO (2) -fertilization. For this purpose, we use a terrestrial carbon cycle model and consider two extreme scenarios: unlimited CO2-fertilization is allowed for the terrestrial vegetation with CO2 concentration level at 735 ppm in one case, and CO2-fertilization is capped at year 1975 levels for another simulation. Our simulations show that, under equilibrium conditions, modeled carbon stocks in natural potential vegetation increase by 17 Gt-C with unlimited fertilization for CO2 levels and climate change corresponding to the end of 21st century but they decline by 5.5 Gt-C if fertilization is limited at 1975 levels of CO2 concentration. The carbon stock changes are dominated by forests. The area covered by natural potential forests increases by about 36% in the unlimited fertilization case but decreases by 15% in the fertilization-capped case. Thus, the assumption regarding CO2-fertilization has the potential to alter the sign of terrestrial carbon uptake over India. Our model simulations also imply that the maximum potential terrestrial sequestration over India, under equilibrium conditions and best case scenario of unlimited CO2-fertilization, is only 18% of the 21st century SRES A2 scenarios emissions from India. The limited uptake potential of the natural potential vegetation suggests that reduction of CO2 emissions and afforestation programs should be top priorities.

Implications of climate change on mitigation potential estimates for forest sector in India

Climate change is projected to impact forest ecosystems, including biodiversity and Net Primary Productivity (NPP). National level carbon forest sector mitigation potential estimates are available for India; however impacts of projected climate change are not included in the mitigation potential estimates. Change in NPP (in gC/m(2)/yr) is taken to represent the impacts of climate change. Long term impacts of climate change (2085) on the NPP of Indian forests are available; however no such regional estimates are available for short and medium terms. The present study based on GCM climatology scenarios projects the short, medium and long term impacts of climate change on forest ecosystems especially on NPP using BIOME4 vegetation model. We estimate that under A2 scenario by the year 2030 the NPP changes by (-5) to 40% across different agro-ecological zones (AEZ). By 2050 it increases by 15% to 59% and by 2070 it increases by 34 to 84%. However, under B2 scenario it increases only by 3 to 25%, 3.5 to 34% and (-2.5) to 38% respectively, in the same time periods. The cumulative mitigation potential is estimated to increase by up to 21% (by nearly 1 GtC) under A2 scenario between the years 2008 and 2108, whereas, under B2 the mitigation potential increases only by 14% (646 MtC). However, cumulative mitigation potential estimates obtained from IBIS-a dynamic global vegetation model suggest much smaller gains, where mitigation potential increases by only 6% and 5% during the period 2008 to 2108.

A simple method for potential flow simulation of cascades

A simple method using a combination of conformal mapping and vortex panel method to simulate potential flow in cascades is presented. The cascade is first transformed to a single body using a conformal mapping, and the potential flow over this body is solved using a simple higher order vortex panel method. The advantage of this method over existing methodologies is that it enables the use of higher order panel methods, as are used to solve flow past an isolated airfoil, to solve the cascade problem without the need for any numerical integrations or iterations. The fluid loading on the blades, such as the normal force and pitching moment, may be easily calculated from the resultant velocity field. The coefficient of pressure on cascade blades calculated with this methodology shows good agreement with previous numerical and experimental results.

Support vector machine for evaluating seismic-liquefaction potential using shear wave velocity

The use of the shear wave velocity data as a field index for evaluating the liquefaction potential of sands is receiving increased attention because both shear wave velocity and liquefaction resistance are similarly influenced by many of the same factors such as void ratio, state of stress, stress history and geologic age. In this paper, the potential of support vector machine (SVM) based classification approach has been used to assess the liquefaction potential from actual shear wave velocity data. In this approach, an approximate implementation of a structural risk minimization (SRM) induction principle is done, which aims at minimizing a bound on the generalization error of a model rather than minimizing only the mean square error over the data set. Here SVM has been used as a classification tool to predict liquefaction potential of a soil based on shear wave velocity. The dataset consists the information of soil characteristics such as effective vertical stress (sigma'(v0)), soil type, shear wave velocity (V-s) and earthquake parameters such as peak horizontal acceleration (a(max)) and earthquake magnitude (M). Out of the available 186 datasets, 130 are considered for training and remaining 56 are used for testing the model. The study indicated that SVM can successfully model the complex relationship between seismic parameters, soil parameters and the liquefaction potential. In the model based on soil characteristics, the input parameters used are sigma'(v0), soil type. V-s, a(max) and M. In the other model based on shear wave velocity alone uses V-s, a(max) and M as input parameters. In this paper, it has been demonstrated that Vs alone can be used to predict the liquefaction potential of a soil using a support vector machine model. (C) 2010 Elsevier B.V. All rights reserved.

Thermophilic fungi: An assessment of their potential for growth in soil

An attempt has been made to forecast the potential of thermophilic fungi to grow in soil in the laboratory and in the field in the presence of a predominantly mesophilic fungal flora at usual temperature. The respiratory rate of thermophilic fungi was markedly responsive to changes in temperature, but that of mesophilic fungi was relatively independent of such changes. This suggested that in a thermally fluctuating environment, thermophilic fungi may be at a physiological disadvantage compared to mesophilic fungi. In mixed cultures in soil plates, thermophilic fungi outgrew mesophilic fungi under a fluctuating temperature regime only when the amplitude of the fluctuating temperatures was small and approached their temperature optima for growth. An antibody probe was used to detect the activity of native or an introduced strain of a thermophilic fungus, Thermomyces lanuginosus, under field conditions. The results suggest that although widespread, thermophilic fungi are ordinarily not an active component of soil microflora. Their presence in soil most likely may be the result of the aerial dissemination of propagules from composting plant material.

Potential of bio-DME as a transportation fuel for India

This article discusses the potential of bio-dimethyl ether (DME) as a promising fuel for India in the transportation sector where a majority of imported petroleum in the form of diesel is used. Specifically, the suitability of DME in terms of its properties vis-a-vis those of diesel, ability to liquefy DME at low pressures similar to liquefied petroleum gas (LPG), and ease of production from renewable feedstock (biomass), and most importantly, very low emissions including near-zero soot levels are some of the features that make it an attractive option. A detailed review presents the state-of-the-art on various aspects such as estimates of potential bio-DME production, methods of synthesis of bio-DME, important physicochemical properties, fuel-injection system-related concerns (both conventional and common-rail system), fuel spray characteristics which have a direct bearing on the engine performance, and finally, exhaust emissions. Future research directions covering all aspects from production to utilization are summarized (C) 2010 American Institute of Physics. doi:10.1063/1.3489529]

A Study on the Success Potential of Multiple Mobile Payment Technologies

Payment systems all over the world have grown into a complicated web of solutions. This is more challenging in the case of mobile based payment systems. Mobile based payment systems are many and consist of different technologies providing different services. The diffusion of these various technologies in a market is uncertain. Diffusion theorists, for example Rogers, and Davis suggest how innovation is accepted in markets. In the case of electronic payment systems, the tale of Mondex vs Octopus throws interesting insights on diffusion. Our paper attempts to understand the success potential of various mobile payment technologies. We illustrate what we describe as technology breadth in mobile payment systems using data from payment systems all over the world (n=62). Our data shows an unexpected superiority of SMS technology, over other technologies like NFC, WAP and others. We also used a Delphi based survey (n=5) with experts to address the possibility that SMS will gain superiority in market diffusion. The economic conditions of a country, particularly in developing countries, the services availed and characteristics of the user (for example number of un-banked users in large populated countries) may put SMS in the forefront. This may be true more for micro payments using the mobile.

Digital simulation of galvanostatic current-potential data for gas-diffusion electrodes and estimation of electrodekinetic parameters

A computerized non-linear-least-squares regression procedure to analyse the galvanostatic current-potential data for kinetically hindered reactions on porous gas-diffusion electrodes is reported. The simulated data fit well with the corresponding measured values. The analytical estimates of electrode-kinetic parameters and uncompensated resistance are found to be in good agreement with their respective values obtained from Tafel plots and the current-interrupter method. The procedure circumvents the need to collect the data in the limiting-current region where the polarization values are usually prone to errors. The polarization data for two typical cases, namely, methanol oxidation on a carbon-supported platinum-tin electrode and oxygen reduction on a Nafion-coated platinized carbon electrode, are successfully analysed.