Study of thickness-dependent magnetic and transport properties of Fe/Al nanostructures

The paper presents magnetic and transport properties of compositionally modulated Fe/Al multilayer structures (MLS), with an overall atomic concentration ratio of Fe:Al = 3:1, 2:1 and 1:1. All MLS show soft ferromagnetic behaviour at room temperature (RT) with an in-plane easy axis of magnetization. In each case, coercivity increases continuously and magnetization decreases with an increase in temperature due to enhancement in the anisotropy as a result of non-uniform and disordered formation of thin intermixed (dead) FeAl layer at the interfaces. The Curie temperature obtained for the MLS is much less than that of bcc Fe but is well above RT. The observed magnetic behaviour is mainly attributed to the formation of different FeAl phases and increase in anti-ferromagnetic interlayer coupling with addition of Al. The formation of these phases is also supported by resistivity results. The results of this research enabled us to understand that by controlling of layers thickness and temperature in multilayer systems, the nanogranular thin films with good resistive and soft magnetic properties can be obtained.     

Feasibility study for detecting copper contaminants in transformer insulation using laser-induced breakdown spectroscopy

In recent times, copper sulphide (Cu₂S) diffusion in the transformer insulation is a major problem reducing the life of transformers. It is therefore essential to identify a simple methodology to understand the diffusion of Cu₂S into the solid insulation [oil impregnated pressboard (OIP)]. In the present work, laser-induced breakdown spectroscopy (LIBS) was adopted to study the diffusion of Cu₂S into the pressboard insulation and to determine the depth of diffusion. The diffusion of Cu₂S in pressboard was confirmed by electrical discharge studies. In general, flashover voltage and increase in ageing duration of pressboard insulation/Cu concentration had inverse relationship. The characteristic emission lines were also studied through optical emission spectroscopy. Based on LIBS studies with Cu powder dispersed pressboard samples, Cu I emission lines were found to be resolvable up to a lowest concentration of 5 μg/cm². The LIBS intensity ratio of Cu I–Ca II emission lines were found to increase with increase in the ageing duration of the OIP sample. LIBS studies with OIP samples showed an increase in the optical emission lifetime. LIBS results were in agreement with the electrical discharge studies.     

Application of various spectroscopic techniques to characterize the archaeological pottery excavated from Manaveli,Puducherry, India

This paper is focused on a spectroscopic study of some ancient pottery shreds from an archaeological site Manaveli village, Puducherry, India. Analytical characterization using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and differential scanning colorimetric coupled with thermo gravimetric analysis were carried out on red and black ware and red ware recently excavated from the above site. The experimental results of FT-IR and XRD are similar and allowed us to identify the mineralogical composition of pottery samples. In addition, TGA was applied in order to study the dehydration of hydroscopic water and decomposition of carboxyl group in the powdered pottery samples during heating. Moreover, this paper proves that all the above spectroscopic techniques are very useful analytical tool for the examination of ancient pottery, which is also suitable for the identification of its firing temperature and firing atmosphere.     

Telechelic Poly(disulfide)s and Related Block Copolymer

In this communication, a mild, efficient, and generalized polycondensation route is developed for poly(disulfide)s from commercially available monomers 2,2′‐dithiodipyridine and 1,6‐hexanedithiol. Using the stoichiometric imbalance between the two monomers, it is possible to produce telechelic poly(disulfide)s of predictable molecular weight with reactive pyridyl disulfide groups at both the terminals of the chain. The two terminal pyridyl disulfide groups can be quantitatively replaced by a functional thiol using selective thiol‐disulfide exchange and thus produces functional telechelic poly(disulfide)s, which can be used as a macroinitiator to initiate ring‐opening poly­merization of a cyclic lactide monomer generating an ABA‐type triblock copolymer with degradable B block.

     

Rapid Determination of Fingolimod Hydrochloride-Related Substances and Degradation Products in API and Pharmaceutical Dosage Forms by Use of a Stability-Indicating UPLC Method

Ultra-performance liquid chromatography coupled with photodiode-array detection has been used to develop a simple, sensitive, and reproducible reversed-phase method for quantitative determination of fingolimod hydrochloride and all possible process-related impurities. Chromatographic separation was achieved on a Waters Acquity BEH C18 (100 mm × 2.1 mm, 1.7 µm) column. The mobile phase was a gradient prepared from potassium dihydrogen phosphate (20 mM) containing 0.1 % (v/v) triethylamine and adjusted to pH 6.5 with trifluoroacetic acid (component A) and 85:15 (v/v) acetonitrile–water (component B); the gradient program (time (min)/% B) was: 0.01/20, 2.0/20, 6.0/75, 9.0/90, 12.0/90, 14.0/20, 16.0/20; the run time was 16 min and fingolimod hydrochloride and its six impurities were well separated. Eluting compounds were monitored at 220 nm. The method was validated for precision, specificity, linearity, limit of detection, limit of quantification, accuracy, and robustness in accordance with International Conference on Harmonization guidelines. Fingolimod hydrochloride was subjected to oxidative, acid, base, hydrolytic, thermal, and photolytic stress, and analysis was conducted to determine the amounts of related impurities formed.

     

Molecular sensing using armchair graphene nanoribbon

In molecular electronics, the conductance strongly depends on the frontier energy levels and spatial orientations of molecules. Utilizing these features, we investigate the electron transport characteristics of conjugated molecules attached on an armchair graphene nanoribbon. The resulting sharp reduction in the transmission which represents molecular fingerprints and the change of the transmission depending on the molecular orientation, are examined in accordance with a unified picture of the Fano–Anderson model. These characteristics, being unique for each molecule, would be applicable to molecular recognition and configurational analysis. © 2014 Wiley Periodicals, Inc.     

Improving the sensitivity of a humidity sensor based on fiber bend coated with a hygroscopic coating

A highly sensitive all-fiber humidity sensor is demonstrated. The sensor behaves as a humidity dependent optical switch between 85% and 90% RH. This sensor also offers the advantages of simple structure and low cost and its response is fast and reversible in nature. The typical humidity response of the sensor is suitable for using it as a human breath rate monitor.     

Studies on the influence of surface pre-treatments on electroless copper coating of boron carbide particles

Boron carbide is one of the hard ceramic particles which find application as structural materials and neutron shielding material due to its high neutron capture cross section. Copper coating on boron carbide particle is essential for the synthesis of metal-ceramic composites with enhanced sinterability and dispersibility. Surface characteristics of the substrate and the coating parameters play a foremost role in the formation of effective electroless coating. The effect of surface pre-treatment conditions and pH on electroless copper coating of boron carbide particles has been studied. Surface pre-treatement of B₄C when compared to acid treated and alkali treated particles were carried out. Uniform copper coating was observed at pH 12 in alkali treated particles when compared to others due to the effective removal of inevitable impurities during the production and processing of commercially available B₄C. A threshold pH 11 was required for initiation of copper coating on boron carbide particles. The growth pattern of the copper coating also varies depending on the surface conditions from acicular to spherical morphology.     

An efficient representation of Benes networks and its applications

The most popular bounded-degree derivative network of the hypercube is the butterfly network. The Benes network consists of back-to-back butterflies. There exist a number of topological representations that are used to describe butterfly—like architectures. We identify a new topological representation of butterfly and Benes networks.The minimum metric dimension problem is to find a minimum set of vertices of a graph G(V,E) such that for every pair of vertices u and v of G, there exists a vertex w with the condition that the length of a shortest path from u to w is different from the length of a shortest path from v to w. It is NP-hard in the general sense. We show that it remains NP-hard for bipartite graphs. The algorithmic complexity status of this NP-hard problem is not known for butterfly and Benes networks, which are subclasses of bipartite graphs. By using the proposed new representations, we solve the minimum metric dimension problem for butterfly and Benes networks. The minimum metric dimension problem is important in areas such as robot navigation in space applications.     

Topological regular semigroups and topological inductive groupoids

The theory of topological semigroups has emerged as a separate discipline during the fifties (cf. Hofmann and Mostert [5] and Carruth, Koch and Hildebrant [3]), but the idea of topologically consistent regularity in such semigroups does not seem to have gained much attention. In this paper topological regular semigroups are introduced where the regularity is topologically consistent. The topological version of the structure theorem for regular semigroups given by Nambooripad [7] is provided here. Some special cases are also discussed. The necessary terminology on topological groupoids are available in Brown and Hardy [1] and Mackenzie [6].