Defect driven ferromagnetism in SnO2: a combined study using density functional theory and positron annihilation spectroscopy

Room temperature ferromagnetic ordering has been observed in polycrystalline SnO₂. Defect characterization by positron annihilation technique and ab initio calculation indicates that tin vacancies are mainly responsible for inducing magnetic moment in oxygen irradiate SnO₂.

Role of substrate effects on the morphological, structural, electrical and thermoelectrical properties of V2O5thin films

The present work focuses on the influence of different substrates on the morphological, compositional, phase purity, structural and transport properties of vanadium pentaoxide (V₂O₅) thin films.

Phase evolution and electrical properties of Co–Sb alloys fabricated from Co/Sb bilayers by thermal annealing and ion beam mixing

Thermoelectric power enhancement of ion beam synthesized Co–Sb alloy thin films.

Electronic excitation induced structural, optical and electrical properties of Se85S10Zn5thin films and applicability of a single oscillator model

The effect of electronic excitation induced by 120 MeV Ag⁹⁺ion irradiation on the physical properties of Se₈₅S₁₀Zn₅thin films has been investigated at various ion fluencies.

Investigating spin reversal and other anomalies in magnetic, transport and specific heat measurements of NdFeO3 and NdFe0.5Ni0.5O3 ortho-perovskites

Specific heat versus temperature. Lower inset: zero-field data with the fitting result. Upper inset: specific heat versus temperature at different magnetic fields near a Schottky anomaly in (a) NFO and (b) NFNO.

Effect of Mn doping on structural, morphological and dielectric properties of EuFeO3 ceramics

The conductivity measurements show that Mn doped EuFeO₃ compounds obey Jonscher's universal power law.

Effect of defects and film thickness on the optical properties of ZnO–Au hybrid films

Thickness and defects effects on the optical properties of ZnO–Au hybrid films were studied using optical and electronic structural studies.

Enhancement of thermoelectric power of PbTe:Ag nanocomposite thin films

Formation of nanostructures results in the enhancement in thermoelectric power of PbTe:Ag thin films.

Graphene scavenges free radicals to synergistically enhance structural properties in a gamma-irradiated polyethylene composite through enhanced interfacial interactions

A unique strategy for scavenging free radicals in situ on exposure to gamma irradiation in polyethylene (PE) nanocomposites is presented.

Electrical and magnetic properties of the pulsed laser deposited Ca doped LaMnO3 thin films on Si (100) and their electronic structures

Normalized O K-edge XAS spectra of La_1−xCa_xMnO₃ (x = 0.0, 0.3, 0.5, and 0.7) samples.

An experimental setup for the simultaneous measurement of thermoelectric power of two samples from 77 K to 500 K

We report on an experimental setup for the simultaneous measurement of the thermoelectric power (TEP) of two samples in the temperature range from 77 K to 500 K using optimum electronic instruments. The setup consists of two rectangular copper bars in a bridge arrangement for sample mounting, two surface mount (SM) chip resistors for creating alternate temperature gradient, and a type E thermocouple in differential geometry for gradient temperature (ΔT) measurement across the samples. In addition, a diode arrangement has been made for the alternate heating of SM resistors using only one DC current source. The measurement accuracy of ΔT increases with the differential thermocouple arrangement. For the calibration of the setup, measurements of TEP on a high purity (99.99%) platinum wire and type K thermocouple wires Chromel and Alumel have been performed from 77 K to 500 K with respect to copper lead wires. Additionally, this setup can be utilized to calibrate an unknown sample against a sample of known absolute TEP.

N-Ion-implanted TiO2 photoanodes in quantum dot-sensitized solar cells

Hierarchical nanostructured titanium dioxide (TiO(2)) clumps were fabricated using electrostatic spray with subsequent nitrogen-ion doping by an ion-implantation technique for improvement of energy conversion efficiency for quantum dot-sensitized solar cells (QDSCs). CdSe quantum dots were directly assembled on the produced N-ion-implanted TiO(2) photoanodes by chemical bath deposition, and their photovoltaic performance was evaluated in a polysulfide electrolyte with a Pt counter electrode. We found that the photovoltaic performance of TiO(2) electrodes was improved by nearly 145% upon N-ion implantation. The efficiency improvement seems to be due to (1) the enhancement of electron transport through the TiO(2) layer by inter-particle necking of primary TiO(2) particles and (2) an increase in the recombination resistance at TiO(2)/QD/electrolyte interfaces by healing the surface states or managing the oxygen vacancies upon N-ion doping. Therefore, N-ion-doped photoanodes offer a viable pathway to develop more efficient QD or dye-sensitized solar cells.

Efficient Performance of Electrostatic Spray-Deposited TiO2 Blocking Layers in Dye-Sensitized Solar Cells after Swift Heavy Ion Beam Irradiation

A compact TiO2 layer (~1.1 μm) prepared by electrostatic spray deposition (ESD) and swift heavy ion beam (SHI) irradiation using oxygen ions onto a fluorinated tin oxide (FTO) conducting substrate showed enhancement of photovoltaic performance in dye-sensitized solar cells (DSSCs). The short circuit current density (Jsc = 12.2 mA cm(-2)) of DSSCs was found to increase significantly when an ESD technique was applied for fabrication of the TiO2 blocking layer, compared to a conventional spin-coated layer (Jsc = 8.9 mA cm(-2)). When SHI irradiation of oxygen ions of fluence 1 × 10(13) ions/cm(2) was carried out on the ESD TiO2, it was found that the energy conversion efficiency improved mainly due to the increase in open circuit voltage of DSSCs. This increased energy conversion efficiency seems to be associated with improved electronic energy transfer by increasing the densification of the blocking layer and improving the adhesion between the blocking layer and the FTO substrate. The adhesion results from instantaneous local melting of the TiO2 particles. An increase in the electron transport from the blocking layer may also retard the electron recombination process due to the oxidized species present in the electrolyte. These findings from novel treatments using ESD and SHI irradiation techniques may provide a new tool to improve the photovoltaic performance of DSSCs.

Magnetic and humidity-sensing properties of nanostructured CuxCo(1-x)Fe2O4 synthesized via autocombustion

The magnetic nanomaterials of CuxCo(1-x)Fe2O4 (x = 0.0, 0.5, and 1.0) were synthesized via autocombustion. The crystallite sizes of these materials were calculated from their X-ray diffraction peaks and were found to be within the range of 23-43 nm. The band near 575 cm(-1) that was observed in the Fourier transform infrared spectrum of these samples confirmed the presence of the ferrite phase. The conductivity versus temperature graph shows thermal hysteresis and exhibits the knee points at 475, 525, and 500 degrees C for copper ferrite, cobalt ferrite, and copper-cobalt ferrite, respectively. The M-H loops for these materials were traced using a vibrating sample magnetometer, and they indicated a significant increase in intrinsic coercivity due to the addition of Co2+ ions in the copper ferrite, while the remanence and saturation magnetization decreased. The ferrite materials that were used in this study exhibited good humidity sensitivity, but copper ferrite showed higher sensitivity compared to the other two materials.

Electronic structure studies of nanoferrite Cu(x)Co(1-x)Fe2O4 by X-ray absorption spectroscopy

Pure and mixed cobalt copper ferrites are of great interest due to their widespread application in electronics and medicine. We report on the electronic structure of a nanoferrite Cu(x)Co(1-x)Fe2O4 (0.0 < or = x < or = 1.0) system studied by X-ray absorption spectroscopy. These magnetic nanoferrites (average crystallite size approximately 31-43 nm) were synthesized by an auto combustion method and are characterized by high resolution X-ray diffraction and near edge X-ray absorption fine structure measurements at the O K and Co, Cu, and Fe L-edges. The O K-edge spectra suggest that there is a strong hybridization between O 2p and 3d electrons of Co, Cu and Fe cations and Fe L3,2-edge spectra indicate that Fe ions coexist in mixed valence states (Fe3+ and Fe2+) at tetrahedral and octahedral sites of the spinel structure. Copper and cobalt ions are distributed in the divalent state in octahedral sites of the spinel structure. The origin of high saturation magnetization and coercivity in cobalt-copper ferrites are explained in light of these results.

Investigations on the in vitro bioactivity of swift heavy oxygen ion irradiated hydroxyapatite

The effect of swift heavy oxygen ion irradiation of hydroxyapatite on its in vitro bioactivity was studied. The irradiation experiment was performed using oxygen ions at energy of 100 MeV with 1 x 10(12) and 1 x 10(13) ions/cm2 fluence range. The irradiated samples were characterized by glancing angle X-ray diffraction (GXRD), photoluminescence spectroscopy (PL) and scanning electron microscopy (SEM). GXRD showed that irradiated samples exhibited better crystallinity. The irradiated samples revealed an increase in PL intensity. In addition, the irradiated hydroxyapatite was found to have enhanced bioactivity.

Preparation of thermally stable nanocrystalline hydroxyapatite by hydrothermal method

Thermally stable hydroxyapatite (HAp) was synthesized by hydrothermal method in the presence of malic acid. X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA) was done on the synthesized powders. These analyses confirmed the sample to be free from impurities and other phases of calcium phosphates, and were of rhombus morphology along with nanosized particles. IR and Raman analyses indicated the adsorption of malic acid on HAp. Thermal stability of the synthesized HAp was confirmed by DTA and TGA. The synthesized powders were thermally stable upto 1,400 degrees C and showed no phase change. The proposed method might be useful for producing thermally stable HAp which is a necessity for high temperature coating applications.

Effect of swift heavy ions in Ni-Al nanocrystalline films studied by X-ray absorption spectroscopy

X-ray absorption spectroscopic measurements have been used to compare the electronic structures of swift heavy ions (100 MeV Si ions) irradiated and pristine Ni-Al nanocrystalline films. Results from X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES) spectra at Al K-, and Ni L(2,3)-edges and extended X-ray absorption fine structure (EXAFS) at Ni K-edges are discussed. The observed XRD peaks indicate the improvement of crystalline nature and Al(111) clustering after the swift heavy ion interactions. While the XANES spectra at Ni L(2,3)-edges show decrease in the intensity of white line strength, the Al K-edge shows increase in intensity after irradiation. Above results imply that swift heavy ions induce low Z (i.e., Al) ion mass transport, changes in Al sp-Ni-d hybridization, and charge transfer. EXAFS results show that crystalline nature is improved after swift heavy irradiation which is consistent with XRD results.

Electrochemical destruction of p-chlorophenol and p-nitrophenol -- Influence of surfactants and anode materials

The electrochemical oxidative removal of p-chlorophenol and p-nitrophenol was studied by cyclic voltammetry (CV) and constant current electrolysis on commercially available graphite and titanium substrate insoluble anodes (TSIA). The effect of cationic cetyl trimethylammonium bromide (CTAB), anionic sodium dodecyl sulphate (SDS) and non-ionic polyoxyethylene(23)lauryl ether (Brij-35) surfactants, which prevent adherent film formation on the electrode surface were also studied. CV experiments indicate that p-chlorophenol exhibits a relatively higher tendency for film formation on graphite and that sodium chloride is a better medium for the destruction of phenols. The electrochemical oxidation of phenols under galvanostatic conditions in chloride medium with CTAB enhanced the detoxification process with significantly lower fouling effects on TSIA. The surfactants, however, did not improve phenol removal on graphite under identical experimental conditions. A charge of 2.5F per mol was found to be sufficient to achieve 44-48% removal of phenol on both the electrodes in the absence of the surfactants. A 55-65% removal was achieved in the presence of the cationic surfactant on the TSIA electrode. Phenol was removed as a low molecular weight polymer (MW approximately 4450).

X-ray absorption spectroscopy investigations on oxidized Ni/Au contacts to p-GaN

X-ray absorption spectroscopy was used to investigate the electronic structure of as-deposited and oxidized Ni/Au contacts to p-GaN and to elucidate the mechanism responsible for low impedance. X-ray absorption near edge spectra of Ni K- and L3,2-edges clearly indicate formation of NiO on the sample surface after annealing. The reason for low impedance may be attributed to increase in hole concentration and existence of p-NiO layer on the surface.

X-ray absorption spectroscopy studies of Ba(1-x)Ca(x)TiO3

We report x-ray absorption near edge spectroscopy (XANES) of Ca and O K-edges of Ba(1-x)Ca(x)TiO3 (x = 0, 0.01, 0.08, 1) and understand the spectral features related to the electronic structure of these perovskites. The XANES spectra of Ca K-edge possess a pre-edge peak similar to other 3d transition metals like Ti, Ni when present in perovskite structure and provides information about p-type or hole doping. Presence of considerable amount of 3d states justifies the reason to consider it as a light 3d transition metal. The O K-edge spectra display characteristic spectral features assigned as e(g) and t2g and show strong dependence on concentration.

Egg contamination by Salmonella serovar enteritidis following vaccination with Delta-aroA Salmonella serovar typhimurium

The efficacy of an aroA Salmonella serovar typhimurium modified live vaccine to decrease internal egg contamination after oral challenge of hens with egg-contaminating Salmonella serovar enteritidis was assessed. Challenge was with a mixed phenotype of S. enteritidis that had virulence characteristics previously associated with enhanced oral invasiveness and egg contamination in chickens. Immunized birds had fewer positive ovary/oviduct pools and lower cfu g(-1) cecal contents than did non-immunized birds, but the differences were not significant. The number of positive intestinal (duodenum, jejunum, ileum) and organ (spleen, kidney, liver) pools following challenge from each treatment group were equivalent. Most importantly, immunization did not decrease egg contamination. These results suggest that the ability of modified live vaccines to reduce internal egg contamination by S. serovar enteritidis can be assessed using characterized strains for challenge.

Numerical evidence for the existence of a low-dimensional attractor and its implications in the rheology of dilute suspensions of periodically forced slender bodies

We provide numerical evidence for the existence of a low-dimensional chaotic attractor in the rheology of dilute suspensions of slender bodies in a simple shear flow. The rheological parameters which characterize the stress deformation behavior of the suspension are calculated based on appropriate averages over the orientation vectors of the slender bodies. The system considered in this work, therefore, exhibits chaos in experimentally measurable averages over a large number of uncoupled chaotic oscillators. The numerical demonstration that these parameters may evolve chaotically may thus have important consequences for both chaos theory and suspension rheology. We also provide plausible explanations for the existence of a low-dimensional chaotic attractor in the rheological parameters in terms of the expressions for the rheological parameters and the coupling between individually chaotically evolving orientations and the expressions for the rheological parameters.

The structure of the colony migration factor from pathogenic Proteus mirabilis. A capsular polysaccharide that facilitates swarming

Swarming by Proteus mirabilis is characterized by cycles of rapid and coordinated population migration across surfaces following differentiation of vegetative cells into elongated hyperflagellated swarm cells. It has been shown that surface colony expansion by the swarm cell population is facilitated by a colony migration factor (Cmf), a capsular polysaccharide (CPS) that also contributes to the uropathogenicity of P. mirabilis (Gygi, D., Rahman, M. M., Lai, H.-C., Carlson, R., Guard-Petter, J., and Hughes, C. (1995) Mol. Microbiol. 17, 1167-1175). In this report, the Cmf-CPS was extracted with hot water, precipitated with ethanol, and further purified by gel permeation chromatography. Its structure was established by glycosyl composition and linkage analyses, and by one- and two-dimensional NMR spectroscopy. The Cmf-CPS is composed of the following tetrasaccharide repeating unit. [see text]

Clinical and veterinary isolates of Salmonella enterica serovar enteritidis defective in lipopolysaccharide O-chain polymerization

Twelve human and chicken isolates of Salmonella enterica serovar Enteritidis belonging to phage types 4, 8, 13a, and 23 were characterized for variability in lipopolysaccharide (LPS) composition. Isolates were differentiated into two groups, i.e., those that lacked immunoreactive O-chain, termed rough isolates, and those that had immunoreactive O-chain, termed smooth isolates. Isolates within these groups could be further differentiated by LPS compositional differences as detected by gel electrophoresis and gas liquid chromatography of samples extracted with water, which yielded significantly more LPS in comparison to phenol-chloroform extraction. The rough isolates were of two types, the O-antigen synthesis mutants and the O-antigen polymerization (wzy) mutants. Smooth isolates were also of two types, one producing low-molecular-weight (LMW) LPS and the other producing high-molecular-weight (HMW) LPS. To determine the genetic basis for the O-chain variability of the smooth isolates, we analyzed the effects of a null mutation in the O-chain length determinant gene, wzz (cld) of serovar Typhimurium. This mutation results in a loss of HMW LPS; however, the LMW LPS of this mutant was longer and more glucosylated than that from clinical isolates of serovar Enteritidis. Cluster analysis of these data and of those from two previously characterized isogenic strains of serovar Enteritidis that had different virulence attributes indicated that glucosylation of HMW LPS (via oafR function) is variable and results in two types of HMW structures, one that is highly glucosylated and one that is minimally glucosylated. These results strongly indicate that naturally occurring variability in wzy, wzz, and oafR function can be used to subtype isolates of serovar Enteritidis during epidemiological investigations.

The structure of the capsular polysaccharide from a swarming strain of pathogenic Proteus vulgaris

The structure was determined for the capsular polysaccharide (CPS) isolated from a swarming strain of Proteus vulgaris, CP2-96, which was obtained from the spleen of an infected mouse. The CPS was extracted from the cell pellet by hot water, precipitated with ethanol, and further purified by gel-permeation chromatography. The structure was established by glycosyl composition and linkage analyses, and by NMR spectroscopy. The sequence of the glycosyl residues was determined by a NOESY experiment. The CPS is composed of a tetrasaccharide repeating unit with the following structure: OAc [symbol: see text] 4 -->4)-beta-D-Glcp-(1-->3)-beta-D-GalpNAc-(1-->2)-alpha-D-Glcp-(1-->4)-al pha- D-GlcpA-(1-->.