Influence of Al doping in LaCoO3 on structural,electrical and magnetic properties

We report investigations on polycrystalline LaCo_1?x Al _x O₃ (x = 0–0.9) bulk samples. The solid state synthesized samples showed a coexistence of rhombohedral and monoclinic phases in the intermediate concentrations (0.2 ≤ x ≤ 0.5) and pure rhombohedral phase otherwise. The observed effect of Al doping on dc transport has been analysed on the basis of small polaron hopping mechanism. The magnetisation results presented give evidence of weak ferromagnetism and anomalous temperature dependence of coercivity which we associate to the canting of the localised high-spin Co(III) and anti-symmetric exchange interactions at low temperatures.     

Correction to: Superconducting Transport Properties of NiFe Artificial Spin Ice and Nb Hybrid Structure

Journal of Superconductivity and Novel Magnetism -     

Occurrence of Superconductivity and Magnetism in Nominally Undoped LaOFeAs

Superconductivity in a LaOFeAs system is known to get introduced by F-doping (LaO_1−x F _x FeAs) even under ambient conditions and oxygen deficiency (LaO_1−x FeAs) under high pressure conditions. Hitherto unreported, superconductivity in F-free undoped LaOFeAs samples is observed and confirmed for the first time by various characterization tools–resistive ρ(T,B), magnetic M(T,B) and modulated microwave absorption (MMA) measurements. The ρ(T) at B=0 shows a clear superconducting transition with an onset at T _con∼17 K and a tail-like behavior when R goes to zero at T _c0∼8 K. In the presence of B, the superconducting transition shifts to lower T with a rate ∼−5.5 and −1.65 T/K, depending on whether the ρ(T) has dropped to 90% or 5% of its normal state value, respectively. M(T) in zero field cooling at B=10 mT shows diamagnetic downturn below at ∼12 K. At T<T _c0 the change in MMA with B shows a low field (B∼1 mT) peak, which vanishes at T>T _c0, indicating the presence of weak link superconducting networks in the sample. The sample shows a complex electrical and magnetic behavior in the normal state. For instance, ρ(T) reveals a weak SDW-like anomaly at T∼132 K along with a resistivity minimum at T _min∼78 K. M(T) also shows the presence of a magnetic anomaly at T∼130 K. Both below and above T _con, presence of an additional ferromagnetic component is observed in the isothermal M(B) loop measurements. The superconducting and normal state features of our sample are compared with other undoped and doped LaOFeAs systems reported in the literature.     

Covalent functionalization of zinc oxide nanowires for high sensitivity p-nitrophenol detection in biological systems

High-quality zinc oxide (ZnO) nanowires were synthesized using the atmospheric chemical vapor deposition technique and were appropriately characterized. Subsequently, the nanowire surface was covalently grafted with 1-pyrenebutyric acid (PBA) fluorophore, and surface-sensitive X-ray photoelectron spectroscopy and Fourier transform infrared-attenuated total reflectance spectroscopy were utilized to confirm the functionalization of 1-pyrenebutyric acid on the nanowire surface. Additionally, photoluminescence (PL) measurements were used to evaluate the optical behavior of pristine nanowires. Through fluorescence quenching of 1-pyrenebutyric acid by p-nitrophenol, a detection limit of 28 ppb was estimated. Based on these findings, ZnO nanowires functionalized with 1-pyrenebutyric acid are envisaged as extremely sensitive platforms for the ultra-trace detection of p-nitrophenol in biological systems.     

Empirical relations for the propagation characteristics of diffused channel waveguides

Empirical relations for the propagation constant and the field profile parameters of integrated optical diffused channel waveguides have been developed. The field profile used is the evanescent secant-hyperbolic field, which has been shown earlier to be a very good approximation for diffused channel-waveguide modes. Least-square fitting has been used to obtain the empirical relations. The results show that the error in empirical relations for the propagation constant is within 2% for a broad range of waveguide parameters. The obtained empirical relations for the field profile and the propagation constant have been used, as an example, to calculate the coupling length of diffused channel-waveguide-based directional couplers.     

A novel approach for analyzing severe crash patterns on multilane highways

This study presents a novel approach for analysis of patterns in severe crashes that occur on mid-block segments of multilane highways with partially limited access. A within stratum matched crash vs. non-crash classification approach is adopted towards that end. Under this approach crashes serve as units of analysis and it does not require aggregation of crash data over arterial segments of arbitrary lengths. Also, the proposed approach does not use information on non-severe crashes and hence is not affected by under-reporting of the minor crashes. Random samples of time, day of week, and location (i.e., milepost) combinations were collected for multilane arterials in the state of Florida and matched with severe crashes from the corresponding corridor to form matched strata consisting of severe crash and non-crash cases. For these cases, geometric design/roadside and traffic characteristics were derived based on the corresponding milepost locations. Four groups of crashes, severe rear-end, lane-change related, pedestrian, and single-vehicle/off-road crashes, on multilane arterials segments were compared separately to the non-crash cases. Severe lane-change related crashes may primarily be attributed to exposure while single-vehicle crashes and pedestrian crashes have no significant relationship with the ADT (Average Daily Traffic). For severe rear-end crashes speed limit, ADT, K-factor, time of day/day of week, median type, pavement condition, and presence of horizontal curvature were significant factors. The proposed approach uses general roadway characteristics as independent variables rather than event-specific information (i.e., crash characteristics such as driver/vehicle details); it has the potential to fit within a safety evaluation framework for arterial segments.     

Prediction of Bubble Size Distribution in Aluminium Foam as a Function of %Titanium Hydride Addition

Foaming of liquid aluminium by addition of foaming agent (TiH₂ particles) is numerically simulated using population balance equations. Phenomena such as hydrogen release by the TiH₂ particles, heterogeneous nucleation of bubbles in oxide surface cavities, and diffusion based bubble growth are modelled. A simple mass transfer coefficient, which varies inversely with the bubble size is used to estimate the bubble growth rate. Simulation is performed to study the effect of TiH₂ content on the final bubble size distribution, total number of bubbles and average bubble size. In general, the average properties of the predicted distributions are close to the experimental values, whereas the spread in the bubble size is observed to be considerably narrower for the predicted values. The deviation in the spread of the distributions is attributed to the inverse bubble size dependent growth rate and non-inclusion of bubble coalescence in the model.     

Examining the anomalous electrical characteristics observed in InN nanowires

Research interest in InN has intensified in recent years because of its unique material properties and promising applications in electronic and photonic devices. Measurements on InN nanowires presented by Chang et al., [J. Electron. Mater. 35, 738 (2006)] showed an anomalous resistance behavior in InN nanowires with diameters less than 90 nm. We examine possible theories presented in literature to explain this intriguing observation. We propose that the presence of a high density electron accumulation layer at the surface of thin InN nanowires is the most probable cause for the uncharacteristic relationship between the total measured resistance and the ratio of length-to-area. High density surface electron accumulation layer, characteristic of InN films and nanowire, promotes a surface conduction path distinct from the bulk conduction. For large diameter nanowires, bulk conduction is likely to be the dominant mechanism while surface conduction is proposed to play a major role for small diameter InN nanowires.     

Effect of hydrophilic and hydrophobic polymers on permeation of S-amlodipine besylate through intercalated polymeric transdermal matrix: 3(2) designing,optimization and characterization

Objective: Innovation in material science has made it possible to fabricate a pharmaceutical material of modifiable characteristics and utility, in delivering therapeutics at a sustained/controlled rate. The objective of this study is to design and optimize the controlled release transdermal films of S-Amlodipine besylate by intercalating hydrophilic and hydrophobic polymers.

Methods: 3(2) factorial design and response surface methodology was utilized to prepare formulations by intercalating the varied concentration of polymers(A) and penetration enhancer(B) in solvent. The effect of these independent factors on drug release and flux was investigated to substantiate the ex-vivo, stability and histological findings of the study.

Results: FTIR, DSC revealed the compatibility of drug with polymers; however, the semicrystallinity in drug was observed under PXRD. SEM micrographs showed homogeneous dispersion and entanglement of drug throughout the matrix. Results from the permeation study suggested the significant effect of factors on the ex vivo permeation of drug. It was observed that drug release was found to be increased with an increase in hydrophilic polymer concentration and PE. The formulations having polymers (EC:PVPK-30) at 7:3 showed maximum drug release with highest flux (102.60?±?1.12?µg/cm²/h) and permeability coefficient (32.78?±?1.38?cm/h). Significant effect of PE on lipid and protein framework of the skin was also observed which is responsible for increased permeation. The optimized formulation was found to be stable and showed no-sign of localized reactions, indicating safety and compatibility with the skin.

Conclusion: Thus, results indicated that the prepared intercalated transdermal matrix can be a promising nonoral carrier to deliver effective amounts of drug.