Role of the Relaxation of the Iron(ll1) Ion Spin States Equilibrium in the Kinetics of Ligand Binding to Methaemoglobin

Temperature-jump experiments of the reaction of the thiocyanate ion with human aquomethaemoglobin have been performed in the presence of a 10-fold excess of inositol hexakisphosphate (inositolP,). Two kinetic phases corresponding to the a and /3 subunits were observed. Kinetic parameters of the reaction were evaluated from the reciprocal relaxation times on the basis of a fast relaxation of the iron(iii) ion spin states equilibrium before binding of the ligand. The association, ki,, and dissociation, k-i,, rate constants determined were: k,, = 225 dm3 mol-' s-', k-aL = 1.52 s-', k,, = 2430 dm3 mol-' s-', k-pL = 6.51 s-' at 27"C, pH 6.44. There was good agreement between the equilibrium constant of the ligand binding step determined by static methods (Kequ = 204 & 11 dm3 mol-') and that evaluated from kinetic data [(KaLKpL)1'2 = 235 & 12 dm3 mol-'1. The value ksJkaL = 11 obtained ensured proper separation of the two kinetic phases. Analyses of the subunit relaxation amplitudes, a€,, , showed that inositolP, perturbed the absorption spectrum of the /3 subunits. This suggests that in the presence of the organic phosphate, methaemoglobin behaves as a protein with independent binding sites rather than as an allosteric molecule. The kinetic and relaxation amplitude spectral characteristics of the subunits, in the presence of inositolP, have demonstrated that the kinetic dynamics are effectively decoupled in a stable tetramer

Relaxation amplitude analysis of thiocyanate and formate binding to human aquomethemoglobin A

The kinetics of the reaction of thiocyanate and formate ions with aquomethemoglobin can be adequately accounted for by a scheme in which the ligand-binding step in both the alpha and beta subunits is preceded by a fast transition of the iron atom from high to low spin (Okonjo, K.O. (1980) Eur. J. Biochem. 105, 329-334). Amplitude expressions derived from this scheme are used to analyse the relaxation amplitude data for alpha and beta subunits within the methemoglobin tetramer. The mean of the reaction enthalpies for ligand binding by the subunits within the tetramer is in good agreement with the reaction enthalpy for ligand binding by the methemoglobin tetramer obtained from a Van't Hoff plot of equilibrium titration data

Design and Costing of Information Services in Academic Libraries

Libraries are very important in providing information services to its users. The information services provided by academic libraries range from knowledge access and research support to reprographic services and the provision of information skills, aided by on-on-one assistance and advice. The article looked at the information services provided by academic libraries, including building blocks and methods of designing information products and services. The paper further discussed the basic components of costing/ pricing these information products and services and the different pricing methods used by libraries in deciding on the price of the information products and services they provide. Keywords: Information Services, Design, Information Products and Services, Costing, Academic Librarie

Subunit iron spin heterogeneity in human aquomethemoglobin A

On the basis of a reaction scheme in which the ligand binding steps are preceded by fast iron spin transitions (Okonjo, K.O. (1980) Eur. J. Biochem. 105, 329-334; Iwuoha, E.I. and Okonjo, K.O. (1985) Biochim. Biophys. Acta 829, 327-334), the spin equilibrium constants of methemoglobin subunits are calculated from kinetic and equilibrium binding parameters with azide ion as ligand. The results demonstrate the existence of thermodynamic spin heterogeneity within the tetramer

ICT and elections in Nigeria: rural dynamics of biometric voting technology adoption

Applications of Information and Communications Technology (ICT)-driven innovations are profound in the electoral cycle. Among them, biometric technology is currently sweeping across developing countries. It is, however, only poorly adopted among rural voters. Does the use of biometric technology in the conduct of elections reconstruct rural voters’ behaviour, amid prevailing social challenges? The links between these realities and their consequences are currently less understood, and lacking in supporting literature. I argue that the public perception of biometric technology, the availability of proper infrastructure, and the distance between polling stations and the dwellings of rural voters all affect the latter's level of adoption of biometric technology. These interactions combine to produce specific modalities that shape voting behaviour and general political culture. I elicit primary data from voters in Nigeria’s remote villages, so as to predict the implications and consequences of glossing over the dimensions and magnitude of the biometric technology adaptation challenge by policymakers. I conclude by reflecting on how these interplays and interactions create "spatial differentials" in electoral outcomes/credibility, and proffer possible strategies for institutional intervention.Die Anwendungen von Innovationen im Bereich der Informations- und Kommunikationstechnologie (IKT) sind im Wahlzyklus von großer Bedeutung. Biometrische Technologie erobert derzeit die Entwicklungsländer. Sie wird aber von den Wählern auf dem Land nur schlecht angenommen. Ändert die Nutzung von biometrischer Technologie das Wahlverhalten der Bevölkerung auf dem Land vor dem Hintergrund sozialer Herausforderungen? Der Zusammenhang zwischen diesen Realitäten und ihren Folgen wird in der Literatur noch nicht umfassend behandelt. Der Artikel argumentiert, dass die öffentliche Wahrnehmung der biometrischen Technologie, die Verfügbarkeit einer geeigneten Infrastruktur und die Entfernung zwischen den Wahllokalen und den Siedlungen der Wähler auf dem Land allesamt beeinflussen, inwieweit die ländliche Bevölkerung solche Technologien annimmt. Dieses Zusammenspiel führt zu spezifischen Modalitäten, die das Wahlverhalten und die allgemeine politische Kultur prägen. Ich nutze Primärdaten aus abgelegenen Dörfern in Nigeria, um zu zeigen, wie politische Entscheidungsträger Herausforderungen bei der Anwendung biometrischer Technologien schönreden und welche Folgen dies hat. Abschließend betrachte ich, wie diese Wechselwirkungen und Interaktionen zu "räumlichen Unterschieden" bei Wahlergebnissen/Glaubwürdigkeit führen und biete mögliche Strategien für institutionelle Interventionen an

Capacity Optimization Nanotechnologies for Enhanced Energy Storage Systems

Rechargeable lithium-ion battery (LIB) cathodes consist of transition metal oxide material, which reversibly (de)intercalates lithium at a high potential difference versus a carbon anode. Manganese oxide cathode material offers lower cost and toxicity than the normally used cobalt. However, LiMn2O4 suffers from capacity fading, Mn dissolution at high temperatures, and poor high rate capability. Its ultimate performance, however, depends on the morphology and electrochemical properties. In this work, Au alloyed with Fe, Pd, and Pt, respectively, was synthesized and used to improve the microstructure and catalytic activities by functionalizing LiMn2O4 via a coprecipitation calcination method. The pristine LiMn2O4 and modified materials were examined using a combination of spectroscopic and microscopic techniques along with in-detail galvanostatic charge–discharge tests. Microscopic results revealed that the modified composite cathode materials had high phase purity, highly crystallized particles, and more regular morphological structures with narrow size distributions. Galvanostatic charge–discharge testing indicated that the initial discharge capacities of LiMxMn2-xO4 at 0.1 C for M0.02=PtAu, FeAu, and PdAu were 147, 155.5, and 160.2 mAh g−1, respectively. The enhancement of the capacity retention and higher electrode coulombic efficiency of the modified materials were significant, especially at high C rate. At enlarged cycling potential ranges, the Li(M)0.02Mn1.98O4 samples delivered relevant discharge capacities (70, 80, and 90 mAh g-1) compared to LiMn2O4 (45 mAh g-1)

Analysis of Electrochemical and Structurally Enhanced LiMn2O4 Nanowire Cathode System

The performance of the battery cathode depends on the electrode microstructure and morphology, as well as the inherent electrochemical properties of the cathode materials. The spinel LiMn2O4 is the most promising candidate as a cathode material because of its low cost and nontoxicity compared with commercial LiCoO2. However, there is still a challenge to synthesize high-quality single-crystal nanostructured cathode materials. Nanowires offer advantages of a large surface to volume ratio, efficient electron conducting pathways and facile strain relaxation. To enhance the activity and stability, flexible spinel nanowires are synthesized, via α-MnO2 nanowire precursor method. Ultrathin LiMn2O4 nanowires with cubic spinel structure were synthesized by using a solvothermal reaction to produce α-MnO2 nanowire followed by solid-state lithiation. LiMn2O4 nanowires have diameters less than 10 nm and lengths of several micrometers. The LiMn2O4 nanowires are used as stabilizing support during the electrochemical redox processes. The unique nanoporous material effectively accommodates structural transformation during Li+ ion insertion and effectively reduces Li+ diffusion distances, reducing the volumetric changes and lattice stresses during charge and discharge. Galvanostatic battery testing showed that LiMn2O4 nanowires delivered 146 mAh/g in a large potential window. The electrochemical and spectrochemical interrogation techniques demonstrated that LiMn2O4 nanowires are promising cathode materials for lithium ion batteries as apposed to LiMn2O4 powders

Determination of Total Potency Equivalent Concentration (Tpec) of Carcinogenic Polycyclic Aromatic Hydrocarbons (Cpahs) In Soils of Bodo-City

The aim of this paper is to report the determination of Total potency equivalent concentration (TPEC) of Carcinogenic polycyclic aromatic hydrocarbons (cPAHs) in soil samples from Bodo area in Ogoniland  using the Toxicity Equivalent Factor (TEF) model. Gas Chromatography GC HP 5870 with FID was used for  analysis. Out of the seven cPAHs investigated only three were detected. They are Benzo (a) Pyrene (BaP), Dibenzo (a, h) anthracene and Indeno (1, 2, 3-cd) pyrene with soil concentrations of 19.06 mg/kg, 6.67 mg/kg and 29.26 mg/kg respectively. Their correspondingly individual potency equivalent  concentrations in soil (mg/kg) are 19.06, 0.67 and 2.93 respectively. Benzo (k) Fluoranthene, Benzo (a)  Anthracene, Benzo (b) Fluoranthene and Chrysene was not detected. The calculated TEQ or TPEC is  22.66mg/kg and this value by far exceeds the method B cleanup levels of BaP value of 0.137mg/kg, it suggests a massively contaminated soil. TPEC is 226.6 times higher than the method B and CAL-EPA risk-based cleanup value of 0.1mg/kg while Total cPAHs is 549.9 times higher than the risk-based cleanup value as indicated. This level of soil toxicity with respect to BaP indicates that the area should be declared a no-go area for humans and animals alike. We strongly  recommend the application of Dispersion by  Chemical Reaction Technology, should be deployed immediately in this area for total detoxification and  decontamination of the area.Keywords: TEQ, TEF, PEF, cPAHs, BaP, Bodo, risk assessment

Stripping Voltammetric Measurement of Trace Metal Ions at Screen-printed Carbon and Carbon Paste Electrodes

AbstractScreen-printed carbon electrodes (SPCEs) and carbon paste electrodes (CPEs) were prepared as “mercury-free” electrochemical sensors for the determination of trace metal ions in aqueous solutions. SPCEs were coated with conducting polymer layers of either polyaniline (PANI), or polyaniline-poly(2,2′–dithiodianiline) (PANI-PDTDA). Furthermore, CPEs containing electroactive compounds with reactivity towards metal ions were employed to obtain enhanced selectivity. Optimised experimental conditions for Hg2+, Pb2+, Ni2+ and Cd2+ determination included the supporting electrolyte concentration, deposition potential (Ed) and accumulation time (tacc). Initial results showed linearity in the examined concentration range between 1 × 10-9M and 1 × 10-6M for laboratory prepared solution