Photoanodic and photocathodic behaviour of La5Ti2CuS5O7 electrodes in the water splitting reaction.

The particulate semiconductor La5Ti2CuS5O7 (LTC) with a band gap energy of 1.9 eV functioned as either a photocathode or a photoanode when embedded onto Au or Ti metal layers, respectively. By applying an LTC/Au photocathode and LTC/Ti photoanode to, respectively, photoelectrochemical (PEC) water reduction and oxidation concurrently, zero-bias overall water splitting was accomplished under visible light irradiation. The band structures of LTC/Au and LTC/Ti calculated using a semiconductor device simulator (AFORS-HET) confirmed the critical role of the solid/solid junction of the metal back contact in the charge separation and PEC properties of LTC photoelectrodes. The prominently long lifetime of photoexcited charge carriers in LTC, confirmed by transient absorption spectroscopy, allowed the utilization of both photoexcited electrons and holes depending on the band structure at the solid/solid junction.

Predictors of malaria in febrile children in Sokoto, Nigeria.

BACKGROUND: Presumptive diagnosis of malaria is widespread, even where microscopy is available. As fever is very nonspecific, this often leads to over diagnosis, drug wastage and loss of opportunity to consider alternative causes of fever, hence the need to improve on the clinical diagnosis of malaria. MATERIALS AND METHODS: In a prospective cross-sectional comparative study, we examined 45 potential predictors of uncomplicated malaria in 800 febrile children (0-12 years) in Sokoto, Nigeria. We developed a clinical algorithm for malaria diagnosis and compared it with a validated algorithm, Olaleye's model. RESULTS: Malaria was confirmed in 445 (56%). In univariate analysis, 13 clinical variables were associated with malaria. In multivariate analysis, vomiting (odds ratio, OR 2.6), temperature ≥ 38.5°C (OR 2.2), myalgia (OR 1.8), weakness (OR 1.9), throat pain (OR 1.8) and absence of lung crepitations (OR 5.6) were independently associated with malaria. In children over age 3 years, any 3 predictors had a sensitivity of 82% and specificity of 47% for malaria. An Olaleye score ≥ 5 had a sensitivity of 62% and a specificity of 51%. CONCLUSION: In hyperendemic areas, the sensitivity of our algorithm may permit presumptive diagnosis of malaria in children. Algorithm positive cases can be presumptively treated, and negative cases can undergo parasitological testing to determine need for treatment.

Trapped state sensitive kinetics in LaTiO2N solid photocatalyst with and without cocatalyst loading.

In addition to the process of photogeneration of electrons and holes in photocatalyst materials, the competitive process of trapping of these charge carriers by existing defects, which can both enhance the photocatalytic activity by promoting electron-hole separation or can deteriorate the activity by serving as recombination centers, is also very crucial to the overall performance of the photocatalyst. In this work, using femtosecond diffuse reflectance spectroscopy we have provided evidence for the existence of energetically distributed trapped states in visible-light responsive solid photocatalyst powder material LaTiO2N (LTON). We observe trapped state sensitive kinetics in bare-LTON. CoOx cocatalyst loading (2 wt % CoOx-LTON) shows effect on the kinetics only when presence of excess energy (for above bandgap excitation) results in the generation of surface carriers. Thus, the kinetics show appreciable excitation wavelength dependence, and the experimental results obtained for different λexc have been rationalized on this basis. In an earlier work by Domen and co-workers, the optimized CoOx/LTON has been reported to exhibit a high quantum efficiency of 27.1 ± 2.6% at 440 nm, the highest reported for this class of photocatalysts (J. Am. Chem. Soc. 2012, 134, 8348-8351). In the present work, the mechanism is addressed in terms of picosecond charge carrier dynamics.

High prevalence of asymptomatic malaria in apparently healthy schoolchildren in Aliero, Kebbi state, Nigeria.

BACKGROUND & OBJECTIVES: In malaria endemic areas, continuous exposure to Plasmodium parasites leads to asymptomatic carriers that provide a reservoir, contributing to the persistence of malaria transmission. Thus, a study of the degree of prevalence of asymptomatic parasitaemias will help in assessing the level of reservoir of infection. METHODS: All the consented participants without any signs and symptoms, suggestive of malaria were interviewed and thick blood smears were made to detect malaria parasites. The children presenting with malaria or any other severe illness, and those declining to give consent were excluded from the study. RESULTS: A total of 118 (59.6%) children out of 198 apparently healthy children were positive for malaria parasites while 80 (40.4%) children were negative for malaria parasites. Prevalence of asymptomatic malaria was higher in males 75 (63.6%) compared to females 43 (36.4%), but the difference was not statistically significant. Incidence of asymptomatic malaria was highest with 76.1% in the children aged 6- 10 yr. There was statistically significant association of the use of bednet on prevalence of asymptomatic malaria. INTERPRETATION & CONCLUSION: High prevalence of asymptomatic malaria detected in this study is a big challenge and can be a threat to the present malaria control programme. Thus, it should be considered in assessing and reorganising more effective malaria elimination strategies to achieve the desired goal of malaria control.

Knowledge, attitude and practices on malaria among the rural communities in aliero, northern Nigeria.

OBJECTIVE: Families' perceptions, beliefs, and attitudes about malaria causation, symptom identification, treatment of malaria, and prevention are often overlooked in malaria control efforts. This study was conducted to understand these issues, which can be an important step towards developing strategies, aimed at controlling malaria. MATERIALS AND METHODS: A community based descriptive cross-sectional study in four villages: Danwarai, Gehuru, Jiga, and Kashin Zama of Aliero local government area in Kebbi Sate, in northern Nigeria. Two hundred household were randomly selected and interviewed using standardized questionnaire. RESULTS: Knowledge of the role of mosquitoes in malaria transmission (11.8%) and cause of malaria (9.6%) was observed to be low among the study population. Comprehensive knowledge about malaria prevention measures was high (90%), but not reflecting in their practice (16%). They have good knowledge of mosquito behavior (breeding areas (64.5%), resting places (70%) and biting time (81%)). Seeking hospital care for a febrile child was a good practice (68.5%) observed. Attitudes regarding the best antimalarial therapy was limited (56.7%) to chloroquine. CONCLUSIONS: Misconceptions about malaria transmission and its cause still exist. Knowledge about preventive measures does not necessarily translate into improvement in practices. There is a need for targeted educational programs to increase the communities' efforts to develop desirable attitude and practices regarding malaria and their participation for malaria control.

A new window towards multidimensional sensing of transition metal cations through dual mode sensing ability of N-benzyl-(3-hydoxy-2-naphthalene): emission enhancement coupled remarkable spectral shift.

A structurally simple Schiff base N-benzyl-(3-hydroxy-2-naphthalene) (NBHN32) has been synthesized and characterized by (1)H NMR, (13)C NMR, and DEPT spectroscopy. The photophysical behaviour of NBHN32 in response to the presence of various transition metal cations has been explored by means of steady-state absorption, emission and time-resolved emission spectroscopy techniques. Efficient through space intramolecular photoinduced electron transfer (PET) between the naphthalene fluorophore and the imine group has been argued for extremely low fluorescence yield of NBHN32 compared to the parent molecule 3-hydroxy-2-naphthaldehyde (HN32) containing the same fluorophore but lacking the receptor moiety. Transition metal ion-induced emission enhancement is thus addressed on the lexicon of perturbation of the PET by the metal ions. Apart from fluorescence enhancement, transition metal ion imparts remarkable shift of the emission maxima of NBHN32, which is another unique aspect on the proposed ability of NBHN32 to function as a fluorescence chemosensor.

Inequivalence of substitution pairs in hydroxynaphthaldehyde: A theoretical measurement by intramolecular hydrogen bond strength, aromaticity, and excited-state intramolecular proton transfer reaction.

The inequivalence of substitution pair positions of naphthalene ring has been investigated by a theoretical measurement of hydrogen bond strength, aromaticity, and excited state intramolecular proton transfer (ESIPT) reaction as the tools in three substituted naphthalene compounds viz 1-hydroxy-2-naphthaldehyde (HN12), 2-hydroxy-1-naphthaldehyde (HN21), and 2-hydroxy-3-naphthaldehyde (HN23). The difference in intramolecular hydrogen bond (IMHB) strength clearly reflects the inequivalence of substitution pairs where the calculated IMHB strength is found to be greater for HN12 and HN21 than HN23. The H-bonding interactions have been explored by calculation of electron density ρ(r) and Laplacian ∇(2) ρ(r) at the bond critical point using atoms in molecule method and by calculation of interaction between σ* of OH with lone pair of carbonyl oxygen atom using NBO analysis. The ground and excited state potential energy surfaces (PESs) for the proton transfer reaction at HF (6-31G**) and DFT (B3LYP/6-31G**) levels are similar for HN12, HN21 and different for HN23. The computed aromaticity of the two rings of naphthalene moiety at B3LYP/6-31G** method also predicts similarity between HN12 and HN21, but different for HN23.

A DFT-based theoretical study on the photophysics of 4-hydroxyacridine: single-water-mediated excited state proton transfer.

Study of intra- and intermolecular hydrogen-bonding interaction and excited state proton transfer reaction has been carried out in 4-hydroxyacridine (4-HA) and its hydrated clusters theoretically. Density functional theory [B3LYP/6-311++G(d,p)] has been exploited to calculate structural parameters and relative energies of different conformers of 4-HA and its hydrates. The substantial impact of solvent reaction field on hydrogen-bond energies, conformational equilibrium, and tautomerization reaction in aqueous medium have been realized by employing Onsager and PCM reaction field methods, and the stability of the conformers of 4-HA is found to be profusely modulated by the electrostatic influence of the solvent. A deeper insight into the nature of H-bonding in 4-HA and its hydrated clusters has been achieved under the provision of natural bond orbital and atoms in molecule analysis. Elucidation of potential energy curves for proton transfer reaction reveals that an intrinsic and two-water-molecule-assisted proton transfer (PT) reaction in 4-HA is hindered by high energy barrier in the S(1) surface, whereas single-water-assisted PT reaction is practically rendered barrierless. At the same time, the appreciably high barrier height of the ground state potential energy curve in all the cases unambiguously rules out the possibility of ground state proton transfer reaction.

Study of proteinous and micellar microenvironment using donor acceptor charge transfer fluorosensor N,N-dimethylaminonaphthyl-(acrylo)-nitrile.

Interaction of charge transfer fluorophore N,N-dimethylaminonaphthyl-(acrylo)-nitrile (DMANAN) with globular proteins Human Serum Albumin (HSA) and Bovine Serum Albumin (BSA) brings forth a marked change in the position and intensity of band maxima both in case of absorption and fluorescence spectra. Spectroscopic approach has been elaborately implemented to explore the binding phenomena of the probe with HSA and BSA and it is found that the extent of binding of the probe to both serum albumins is similar in nature. Steady state fluorescence anisotropy values, fluorescence quenching study using acrylamide quencher and Red Edge Excitation Shift (REES) help in drawing reliable conclusions regarding the location of the probe molecule within the hydrophobic cavity of the proteins. An increase in fluorescence lifetime of the probe molecule solubilized in both the proteinous media also indicate that the probe is located at the motionally restricted environment inside the hydrophobic cavity of proteins and hence non-radiative channels are less operative than in the bulk water. Similarly, the variation of position and intensity of the emission maxima of DMANAN solubilized in micellar medium of Sodium Dodecyl Sulphate (SDS) also predicts well the critical micellar concentration (CMC) and polarity of micellar microenvironment.

Interaction of human serum albumin with charge transfer probe ethyl ester of N,N-dimethylamino naphthyl acrylic acid: an extrinsic fluorescence probe for studying protein micro-environment.

The charge transfer (CT) probe ethyl ester of N,N-dimethylamino naphthyl acrylic acid (EDMANA) bound to Human Serum Albumin (HSA) serves as an efficient reporter of the polarity and conformational changes of protein in aqueous buffer (Tris-HCl buffer, pH=7.03) and in presence of denaturant, quencher and reverse micelles. The change in fluorescence intensity and the position of emission maxima of EDMANA in presence of HSA well reflect the nature of binding and location of the probe inside the proteinous environment. The increase in steady state anisotropy values with increase of protein concentration indicate restriction imposed on the mobility of the probe molecules in the proteinous medium. The results of fluorescence quenching of EDMANA by acrylamide, Fluorescence Resonance Energy Transfer (FRET) and Red Edge Excitation Shift (REES) studies throw light on the accessibility to the probe bound to HSA and hence indicate the probable location of the probe within the hydrophobic cavity of HSA. The complicated nature of protein unfolding in presence of urea is well studied by change in the fluorescence properties of EDMANA bound to HSA protein.

Study of protein-probe interaction and protective action of surfactant sodium dodecyl sulphate in urea-denatured HSA using charge transfer fluorescence probe methyl ester of N,N-dimethylamino naphthyl acrylic acid.

We have demonstrated that the intramolecular charge transfer (ICT) probe Methyl ester of N,N-dimethylamino naphthyl acrylic acid (MDMANA) serves as an efficient reporter of the proteinous microenvironment of Human Serum Albumin (HSA). This work reports the binding phenomenon of MDMANA with HSA and spectral modulation thereupon. The extent of binding and free energy change for complexation reaction along with efficient fluorescence resonance energy transfer from Trp-214 of HSA to MDMANA indicates strong binding between probe and protein. Fluorescence anisotropy, red edge excitation shift, acrylamide quenching and time resolved measurements corroborate the binding nature of the probe with protein and predicts that the probe molecule is located at the hydrophobic site of the protein HSA. Due to the strong binding ability of MDMANA with HSA, it is successfully utilized for the study of stabilizing action of anionic surfactant Sodium Dodecyl Sulphate to the unfolding and folding of protein with denaturant urea in concentration range 1M to 9M.

Study of interaction of proton transfer probe 1-hydroxy-2-naphthaldehyde with serum albumins: a spectroscopic study.

In the present work, we have studied the interaction of proton transfer probe 1-hydroxy-2-naphthaldehyde (HN12) with Human Serum Albumin (HSA) and Bovine Serum Albumin (BSA) by steady state absorption and emission spectroscopy combined with time resolved fluorescence measurements. The measured binding constant (K) and free energy change (DeltaG) indicate a stronger affinity of HN12 molecule for HSA than BSA. Steady state anisotropy, excitation anisotropy and fluorescence resonance energy transfer (FRET) studies indicate that the probe molecule resides at the hydrophobic site of the protein environment.