Structural, luminescence and EPR studies on SrSnO3 nanorods doped with europium ions.

The present study describes the structural and luminescent properties of SrSnO(3) nanorods containing Eu(3+) ions. Based on Rietveld refinement of XRD patterns corresponding to both undoped and europium doped SrSnO(3) nanorods, it is inferred that the average bond lengths of Sr-O1 linkages, which have a square planar geometry around Sr(2+) in the SrO(12) polyhedra present in SrSnO(3), remained unaffected with Eu(3+) incorporation into the lattice. However, the average bond lengths of shorter Sr-O2 linkages increase and longer Sr-O2 linkages decrease with Eu(3+) doping into the SrSnO(3) lattice. A lack of variation in the lattice parameters of SrSnO(3) with doped Eu(3+) ions is explained based on mutually compensating changes in the average bond lengths of the Sr-O2 linkages in the unit cell. Luminescence studies have confirmed that Eu(3+) ions occupy the centrosymmetric Sr(2+) site only up to 2 at%, beyond which Eu(3+) ions exist in a significantly distorted environment (grain boundaries). Beyond 3%, incorporation of Eu(3+) ions into the SrSnO(3) lattice leads to the formation of a Eu(2)Sn(2)O(7) phase. From the EPR studies it is confirmed that around 5% of the incorporated Eu(3+) ions get converted to Eu(2+) ions and they occupy Sr(2+) sites in the lattice.

Excess enthalpy and luminescence studies of SnO2 nanoparticles.

The extra reactivity of nano materials is attributed to the excess surface energy stored in the sample. The excess enthalpy of SnO2 nano-particles were measured as a function of particle size using a calvet calorimeter. SnO2 with particle size 11, 27, 47 nm and bulk samples (1 microm) were dropped from room temperature to 987, 936 and 885 K and their H(T)-H298 values were determined. The excess enthalpies for SnO2 samples with particle sizes 11, 27 and 47 nm compared to the bulk sample calculated from the difference between H(T)-H298 values of the nano and the bulk samples were found to be 15.06, 3.05, 2.21 kJ x mol(-1) respectively. Luminescence experiments reveal that the surface trap electron density decreases with increase of particle size. The excess enthalpy is related to the surface trap intensity.

Raman spectroscopic investigations of nanoparticles of Sn(x)Ti(1-x)O2 solid solution.

SnO2 nanoparticles dispersed in TiO2 matrix are prepared at a relatively low temperature of approximately 185 degrees C. Nanoparticles of Sn(x)Ti(1-x)O2 solid solution without significant aggregation have been prepared by annealing them at approximately 500 and 900 degrees C. X-ray diffraction and high-resolution transmission electron microscopy studies have clearly established the nano-size nature of the samples. Raman spectroscopic investigations of these samples show mixed vibrational modes, some of them being similar to TiO2 (A(1g), E(g)), while some of them are similar to SnO2 (B(2g)). The E(g) mode shows significant red shift and B(2g) mode shows significant blue shift. Unlike this A(1g) mode remains unaffected. These results are explained based on the combined effects of random alloy formation and the nano-size nature of samples.

Luminescence properties of SnO2 nanoparticles dispersed in Eu3+ doped SiO2 matrix.

SnO2 nanoparticles dispersed in Eu3+ doped silica (SnO2-SiO2:Eu3+) were prepared at a low temperature (185 degrees C) in ethylene glycol medium. Transmission electron microscopy studies on as-prepared samples have established that SnO2 nanoparticles having size of 4.6 nm are uniformly covered by the SiO2 matrix. Significant extent of exciton mediated energy transfer between SnO2 and Eu3+ ions in heat treated SnO2-SiO2:Eu3+ samples has been attributed to the diffusion of Eu3+ ions from the SiO2 matrix to the near vicinity of SnO2 nanoparticles and its incorporation in the SnO2 matrix. On the other hand, very weak energy transfer exists for SnO2:Eu3+ nanoparticles heated at different temperatures due to the phase segregation of Eu3+ ions from the matrix.

Adsorbed anthranilic acid molecules cause charge reversal of nonionic micelles.

The effect of anthranilic acid, an aromatic amino acid, on the structural characteristics of nonionic micelles of Triton X-100 at different pH values was investigated by light scattering and small-angle neutron scattering (SANS) measurements. The scattered light intensity decreases as pH is increased or decreased on either side of the isoelectric point (IEP = 3.4) of the amino acid. Analysis of the SANS data using a sticky hard-sphere model shows that the micelles are oblate ellipsoids with an axial ratio of approximately 2.3. No significant change could be observed in the size of the micelles with a change in the pH, while the stickiness parameter (tau), which is related to the interaction potential (u(0)) increases on either side of the IEP. As tau increases, u(o) becomes less negative, indicating a decrease in the attractive interaction between nonionic micelles. This can be explained in terms of the changes in the surface charge of the micelles resulting from a shift in the acid-base equilibrium of the adsorbed amino acid. The variation of the intermicellar interaction as calculated from the stickiness parameter is consistent with the picture of reversal of charge of amino acids with pH. This is further supported by the observed variation of the cloud point of the solutions at different pH values. The change in the interparticle interaction is also reflected in the diffusion coefficient of the micelles measured by dynamic light scattering.

Luminescence study on Eu(3+) doped Y(2)O(3) nanoparticles: particle size, concentration and core-shell formation effects.

Nanoparticles of Eu(3+) doped Y(2)O(3) (core) and Eu(3+) doped Y(2)O(3) covered with Y(2)O(3) shell (core-shell) are prepared by urea hydrolysis for 3 h in ethylene glycol medium at a relatively low temperature of 140 °C, followed by heating at 500 and 900 °C. Particle sizes determined from x-ray diffraction and transmission electron microscopic studies are 11 and 18 nm for 500 and 900 °C heated samples respectively. Based on the luminescence studies of 500 and 900 °C heated samples, it is confirmed that there is no particle size effect on the peak positions of Eu(3+) emission, and optimum luminescence intensity is observed from the nanoparticles with a Eu(3+) concentration of 4-5 at.%. A luminescence study establishes that the Eu(3+) environment in amorphous Y (OH)(3) is different from that in crystalline Y(2)O(3). For a fixed concentration of Eu(3+) doping, there is a reduction in Eu(3+) emission intensity for core-shell nanoparticles compared to that of core nanoparticles, and this has been attributed to the concentration dilution effect. Energy transfer from the host to Eu(3+) increases with increase of crystallinity.

Effect of therapy on serum zinc and copper in primary complex of children.

Tuberculosis is a global problem especially in children, more so because of the difficulty in the diagnosis of the disease. There are about 0.5 million deaths every year by this disease, worldwide. There are some reports that, during the disease, there are changes in serum concentrations of zinc and copper, which reach towards normal levels during treatment. Such data for children are scarce, especially in reference to India. Our study indicates that there is an insignificant to significant rise in serum zinc levels in various age groups of children after antitubercular therapy (mean 61.89 +/- 3.21 to 65.24 +/- 3.60 microg/dl) and significant fall in serum copper levels in different age groups of children (mean 129.96 +/- 3.18 to 124.91 +/- 3.48 microg/dl). The Cu/Zn ratio also changed significantly from 2.11 +/- 0.12 to 1.92 +/- 0.12. Because evaluation of available diagnostic criteria for primary complex in children has been found to have high sensitivity, and although this criterion is presently not recommended for diagnosis of primary complex of children, further research can prove its utility in diagnosis and treatment of this disease.

Comparative study of misoprostol vs dinoprostone for induction of labour.

Various methods of induction of labour may be associated with risk and complications. Therefore, this study has been undertaken to compare the safety and efficacy of intra-vaginal misoprostol (PGE1 analogue) with intra-cervical dinoprostone (PGE2) in progress and induction of labour, the maternal side effects and the foetal outcome. 40 pregnant women aged between 16-35 years with indication of induction of labour participated in the study. Twenty patients (control) were administered 0.5 mg dinoprostone intra-cervically, 12 hourly while 20 patients (study group) were given misoprostol 100 microg, 4 hourly, intravaginally. The mean induction of labour initiation interval was 2.08 +/- 1.46 hours in study group and 2.21 +/- 1.20 hours in dinoprostone group. The Induction delivery interval was 6.92 +/- 4.01 hours in misoprostol group and 12.54 +/- 7.73 in dinoprostone group, whereas vaginal route of delivery was 95% in misoprostol group and 85% in dinoprostone group. Average dosages required were 1.55 +/- 1.02 in misoprostol group and 1.30 +/- 0.46 in dinoprostone group. All these result were statistically significant. Very few maternal side effects were reported in study group. There was no significant difference in foetal out come in either group. Therefore, it can be concluded that misoprostol is easy to administer and is cheap, effective, safe and convenient drug for induction of labour.

Enhanced hydrogen generation by particles during sonochemical decomposition of water.

A novel effect of any oxide particle/intermetallics enhancing hydrogen generation from water as compared to water alone when subjected to ultrasonic irradiation is reported here. Addition of methanol to water or decrease in particle size also improved the hydrogen yield. Hydrogen generation from water was further enhanced by the presence of both methanol and particles in water.

Time response and stability of porous silicon capacitive immunosensors.

The time response of affinity sensors made with nanostructured materials is a topic of considerable interest, since affinity sensors made with nanostructured materials provide greater sensitivities than corresponding planar crystalline devices but at the cost of stability and drift. We present a study of the time response of capacitive immunosensors made using porous silicon and ultrathin room temperature anodic oxide. It was found that sensor drift can be substantial but can be reduced by subjecting the capacitive immunosensor in buffer to an anodic bias that is larger than the bias at which sensor capacitance is measured. By measuring sensor response before the addition of the analyte and using it for baseline correction after addition of the analyte, the effect of nonspecific sensor drift can be further reduced. We observed that after the addition of the analyte to the porous silicon immunocapacitor, there is a fast decrease in capacitance (order of tens of seconds) followed by a slow increase (order of tens of minutes), which models well as a sum of exponents with a fast exponential decay followed by a slow exponential rise. Possible processes that can give rise to such a response are perturbations of the double layer for the fast decay and column resistance switching for the slow rise.

Role of bromocriptine and pyridoxine in premenstrual tension syndrome.

Premenstrual syndrome (PMS) is a universal problem of women of reproductive age group. No satisfactory treatment is available to treat this syndrome till date. Sixty female patients with PMS in age group of 20-45 years were interviewed. A detailed history and 20 premenstrual symptoms were included for making the diagnosis of PMS. Premenstrual symptom score of each patient was recorded before treatment. Patients were followed up monthly for 3 months after starting treatment, to ascertain the change in score. The patients were divided into 3 groups of 20 patients each - control group, bromocriptine group and pyridoxine group. In control group, patients were kept on ferrous sulphate tablet 100 mg for 3 months, as placebo. There was no significant change in the premenstrual symptoms score at the end of the study period in control group. Bromocriptrine 2.5 mg twice a day and pyridoxine 100 mg/day showed a significant reduction in the mean premenstrual symptom score after 3 months of treatment. It is concluded that both the drugs are effective for treatment of premenstrual syndrome but, pyridoxine showed significantly higher response rate and lesser incidence of side effects than bromocriptine.

Polymer-surfactant layered heterostructures by electropolymerization of phenosafranine in Langmuir-Blodgett films.

Langmuir-Blodgett (LB) films of the water-soluble dye phenosafranine (PS) have been prepared by its adsorption from aqueous dye solution to an arachidic acid (AA) monolayer at the air-water interface. Atomic force microscopy (AFM) images of the LB films revealed the effect of change in pH of deposition on the degree of complexation of AA with the PS dye. Well-defined circular islands and holes were observed which disappeared with the increase in pH. Polarized absorption studies indicated that the dye molecules are oriented uniaxially with their long axis titled at a constant angle to the surface normal of the LB film. Within the restricted geometry of the LB film, the PS dye was electropolymerized to form a two-dimensional film of poly(phenosafranine) sandwiched between arachidic acid layers. The film was characterized by IR spectroscopy, cyclic voltammetry, and AFM. X-ray diffraction studies reveal the presence of a layer structure in the AA-PS LB film before and after polymerization. The polymer film showed highly anisotropic electrical conductivity of ca. 10 orders of magnitude. This indicates the formation of two-dimensional polyPS layers between arachidic acid layers resulting in a layered heterostructure film having alternate conducting and insulating regions. Also, the conductivity of the polyPS prepared from LB film was found to be approximately 2.5 times higher than the conductivity of polyPS prepared by solution polymerization method.

Structural and electronic properties of Si(n), Si(n)-, and PSi(n-1) clusters (2 < or = n < or = 13): Theoretical investigation based on ab initio molecular orbital theory.

The geometric and electronic structures of Si(n), Si(n)-, and PSi(n-1) clusters (2 < or = n < or = 13) have been investigated using the ab initio molecular orbital theory formalism. The hybrid exchange-correlation energy functional (B3LYP) and a standard split-valence basis set with polarization functions (6-31+G(d)) were employed to optimize geometrical configurations. The total energies of the lowest energy isomers thus obtained were recalculated at the MP2/aug-cc-pVTZ level of theory. Unlike positively charged clusters, which showed similar structural behavior as that of neutral clusters [Nigam et al., J. Chem. Phys. 121, 7756 (2004)], significant geometrical changes were observed between Si(n) and Si(n)- clusters for n = 6, 8, 11, and 13. However, the geometries of P substituted silicon clusters show similar growth as that of negatively charged Si(n) clusters with small local distortions. The relative stability as a function of cluster size has been verified based on their binding energies, second difference in energy (Delta2 E), and fragmentation behavior. In general, the average binding energy of Si(n)- clusters is found to be higher than that of Si(n) clusters. For isoelectronic PSi(n-1) clusters, it is found that although for small clusters (n < 4) substitution of P atom improves the binding energy of Si(n) clusters, for larger clusters (n > or = 4) the effect is opposite. The fragmentation behavior of these clusters reveals that while small clusters prefer to evaporate monomer, the larger ones dissociate into two stable clusters of smaller size. The adiabatic electron affinities of Si(n) clusters and vertical detachment energies of Si(n)- clusters were calculated and compared with available experimental results. Finally, a good agreement between experimental and our theoretical results suggests good prediction of the lowest energy isomeric structures for all clusters calculated in the present study.

Zinc and copper in Indian patients of tuberculosis: impact on antitubercular therapy.

The effectiveness and success of antitubercular therapy is mainly measured by identifying the organism in sputum. In certain patients, especially in geriatric patients, available tuberculosis tests are not satisfactory and do not provide enough information on the effectiveness of antitubercular therapy, as the symptoms might be confused with the existing symptoms of ongoing diseases. Therefore, 60 diagnosed and randomly selected patients with tuberculosis were included into this study. The patients with other associated diseases likely to influence serum copper and zinc were not included in the study. The estimations of serum copper and zinc were done in healthy volunteers and in tubercular patients before the start of treatment and after 4 wk of antitubercular treatment. The average plasma concentration of serum copper and zinc in healthy volunteers were 102 +/- 20 microg/dL and 96 +/- 18 microg/dL respectively. In tuberculosis patients, serum copper and zinc levels were 123.65 +/- 9.98 microg/dL and 64.14 +/- 3.97 microg/dL, respectively, before the start of treatment, which came down to 116.23 +/- 4.27 mug/dL and 74.31 +/- 3.60 microg/dL, respectively, after 4 wk of antitubercular treatment.

Energy pooling in multiple ionization and Coulomb explosion of clusters by nanosecond-long, megawatt laser pulses.

We report the results of experiments that establish the possibility of bringing about multiple ionization and Coulomb explosion of molecular clusters with nanosecond laser pulses at intensities as small as 10(9) W cm(-2). We demonstrate several new facets of the laser-cluster interaction in the low-intensity, long-pulse domain: (i) The choice of laser wavelength for a given cluster species is very crucial. (ii) Excited electronic states play a very important role in the ionization dynamics. (iii) When field ionization is insignificant and ponderomotive energies are very small, it is energy pooling rather than inverse bremsstrahlung that determines how clusters absorb energy from the optical field.

Modification to the cumulant analysis of polydispersity in quasielastic light scattering data.

The electric field correlation function of light scattered from a polydispersed population of spherical particles having log-normal distribution with varying polydispersity is simulated. The correlation function with different polydispersity is compared with the method of cumulants over a wide range of correlation time. The large positive deviation of the method of cumulants at long correlation time is identified. This necessitates the truncation of the data at long correlation time or use of an appropriate weighting function to eliminate errors in the analysis. A modified cumulant analysis is used to overcome the limitation of truncating the correlation function. QELS data from polydisperse samples of micelles, liposomes and polyaniline nanoparticles are compared using the two methods. This method can be extended to the analysis of other multi-exponential decays such as stress relaxation, positron annihilation and NMR relaxation.

Surface modification of polystyrene using polyaniline nanostructures for biomolecule adhesion in radioimmunoassays.

The selection of an appropriate surface as a solid phase for coupling antibodies is a critical step in the development of solid-phase immunoassays. Availability of a new method of preactivating the surface of polystyrene tubes with a layer of another polymer for enhanced immobilization of antibodies seems to be promising. In this paper, we report the activation of a polystyrene surface using a layer of polyaniline and its effect on immobilizing antibodies for use as a solid phase in a T3 immunoassay. The modified surface on the polystyrene was characterized by optical absorption, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The modified tubes were coated with antibody and evaluated for their performance in the assay and validated for radioimmunoassay of T3. AFM images of the modified surface showed an enhancement in the surface roughness (Ra of 20.2 nm), as compared to an unmodified surface (Ra of 6 nm), allowing more adsorption of antibodies to the surface. XPS revealed the presence of N (binding energy approximately 400 eV) on the modified surface, which could help the antibody molecules to bind to these preactivated (modified) tubes. The modified tubes, when coated with antibody, not only showed an increase in the binding with the radioiodinated tracer but also improved the precision of coating the antibody. The present method of activating polystyrene surfaces is simple, does not involve severe chemical treatment, and may have wide applicability to functionalize other supports for immobilizing biomolecules.

Effect of SDS on the self-assembly behavior of the PEO-PPO-PEO triblock copolymer (EO)20(PO)70(EO)20.

The mixed micellar system comprising the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-based triblock copolymer (EO)(20)(PO)(70)(EO)(20) (P123) and the anionic surfactant sodium dodecyl sulfate (SDS) has been investigated in aqueous media by small-angle neutron scattering (SANS) and viscosity measurements. The aggregation number of the copolymer in the micelles decreases upon addition of SDS, but a simultaneous enhancement in the degree of micellar hydration leads to a significant increase in the micellar volume fraction at a fixed copolymer concentration. This enhancement in the micellar hydration leads to a marked increase in the stability of the micellar gel phase until it is destroyed at very high SDS concentration. Mixed micellar systems with low and intermediate SDS concentrations form the micellar gel phase in much wider temperature and copolymer concentration ranges than the pure copolymer micellar solution. A comparison of the observed results with those for the copolymers (EO)(26)(PO)(40)(EO)(26) (P85) and (EO)(99)(PO)(70)(EO)(99) (F127) suggests that the composition of the copolymers plays a significant role in determining the influence of SDS on the gelation characteristics of the aqueous copolymer solutions. Copolymers with high PO/EO ratios show an enhancement in the stability of the gel phase, whereas copolymers with low PO/EO ratios show a deterioration of the same in the presence of SDS.

Estimation of serum zinc and copper in children with acute diarrhea.

Diarrhea is, in reality, as much a nutritional disease as one of fluid and electrolyte loss. Children who die from diarrhea, despite good management of dehydration, are usually malnourished and often severely so. In this study, we determined the serum levels of zinc and copper before and after standard oral rehydration solution (ORS) therapy in children with acute diarrhea and correlated it with diarrheal duration and severity. One hundred ten children suffering from acute diarrhea were included. Serum zinc and copper levels of these children were estimated at the time of enrollment and after treatment with standard ORS therapy. This study shows that children suffering from acute diarrhea show a statistically significant decrease of 13.1% and 12.8% in serum zinc and copper concentrations, respectively, compared to normal. These levels further decrease by 22.6% and 22.4%, respectively, after treatment with standard ORS therapy. Our study shows that children with the lower plasma zinc and copper levels suffered with more severe and longer duration of diarrhea. Zinc and copper supplementation could be added to standard ORS therapy for the reduction in morbidity and mortality associated with acute diarrhea in children.

Photoionization of CH(3)I mediated by the C state in the visible and ultraviolet regions.

Three/two-photon resonant multiphoton ionization (MPI) of the CH3I monomer has been studied in the gas phase at 532 and 355 nm using time-of-flight mass spectrometry. Under low laser intensity (approximately 10(9) W/cm2) the mass spectra showed peaks at m/z 15, 127 and 142, corresponding to [CH3]+, [I]+ and [CH3I]+ species, at both these wavelengths. The laser power dependence for [CH3I]+, [I]+ and [CH3]+ ions showed a three-photon dependence at 532 nm. For the same three ions, photoionization studies at 355 nm gave a power dependence of 2. Both these results suggest that a vibronic energy level at approximately 7 eV, lying in the Rydberg C state, acts as a resonant intermediate level in ionization of CH3I. In the case of 355 nm, with increasing intensity additional peaks at m/z 139 and 141 were observed which could be assigned to [CI]+ and [CH2I]+ fragments. In contrast, for high intensity radiation at 532 nm ( approximately 2 x 10(10) W/cm2), only the [CI]+ fragment was observed. At these wavelengths, fragment ions observed in mass spectra mainly arise from photodissociation of the parent ion. Experiments at another wavelength in the visible region (564.2 nm) confirmed the results obtained at 532 nm. In order to assess the role of the A state in these MPI experiments, additional experiments were performed at 266 and 282.1 nm, which access the A state directly via a one-photon transition, and showed absence of a surviving precursor ion. Reaction energies for various possible dissociation channels of CH3I/[CH3I]+/[CH2I]+ were calculated theoretically at the MP2 level using the GAMESS electronic structure program.