In-situ and ex-situ study of crystallization behaviour of magnetron sputtered Ni63Zr37 amorphous thin film

ABSTRACT

The stages of crystallization of magnetron sputter-deposited Ni₆₃Zr₃₇ film with mostly amorphous structure have been investigated by differential scanning calorimetry (DSC) and in-situ annealing at 300°C by use of heating stage on a high-resolution transmission electron microscope (HRTEM). These results have been further confirmed by grazing incidence X-ray diffraction analyses of thin film specimens annealed ex-situ at 300°C for various durations. The temperature for crystallization found by DSC has been found to increase from 371°C to 434°C with an increase in heating rate from 3°C/min to 10°C/min, and the apparent activation energy for amorphous to crystalline transformation has been found as ～260.2?kJ/mol from the Kissinger plot. Studies on HRTEM using in-situ heating stage have shown the crystallization to occur on annealing at 300°C for ～10?min. Crystallization at a temperature lower than that found by DSC is attributed to structural relaxation with reduction of free volume due to thermal activation. It has been observed that Ni₃Zr forms first due to its large negative enthalpy of formation, and is followed by the formation of Ni-rich solid solution (Ni_ss) grains. HRTEM studies have shown grain rotation with the formation of partial dislocations at Ni₃Zr-Ni_ss interfaces as well as twinning followed by detwinning with dislocation formation in the Ni_ss matrix possibly to reduce the interfacial energy.     

Applicability and effectiveness of classifications models for achieving the twin objectives of growth and outreach of microfinance institutions

Measuring performance of microfinance institutions (MFIs) is challenging as MFIs must achieve the twin objectives of outreach and sustainability. We propose a new measure to capture the performance of MFIs by placing their twin achievements in a 2 × 2 grid of a classification matrix. To make a dichotomous classification, MFIs that meet both their twin objectives are classified as ‘1’ and MFIs who could not meet their dual objectives simultaneously are designated as ‘0’. Six classifiers are applied to analyze the operating and financial characteristics of MFIs that can offer a predictive modeling solution in achieving their objectives and the results of the classifiers are comprehended using technique for order preference by similarity to ideal solution to identify an appropriate classifier based on ranking of measures of performance. Out of six classifiers applied in the study, kernel lab-support vector machines achieved highest accuracy and lowest classification error rate that discriminates the best achievement of the MFIs’ twin objective. MFIs can use both these steps to identify whether they are on the right path to attaining their multiple objectives from their operating characteristics.     

On further application of r as a metric for validation of QSAR models

Validation is a crucial aspect for quantitative structure–activity relationship (QSAR) model development. External validation is considered, in general, as the most conclusive proof of predictive capacity of a QSAR model. In the absence of truly external data set, external validation is usually performed on test set compounds, which are members of the original data set but not used in model development exercise. In the case of small data sets, QSAR researchers experience problem in model development due to the fact that the developed models may be less reliable on account of the small number of training set compounds and such models may also show poor external predictability because the models may not have captured all necessary features required for the particular structure–activity relationships. The present paper attempts to show that ‘true r_(LOO)’ statistic calculated based on the model derived from the undivided data set with application of variable selection strategy at each cycle of leave‐one‐out (LOO) validation may reflect external validation characteristics of the developed model thus obviating the requirement of splitting of the data set into training and test sets. This approach may be helpful in the case of small data sets as it uses all available data for model development and validation thus making the resulting model more reliable. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterisation and cryomagnetic study of a hydrothermally synthesised hydrogen bonded L–M–L type co-ordination polymer

A ligand–metal–ligand type co-ordination polymer [Ni (C₆H₁₂N₄)(NCS)₂(H₂O)₂] _n has been synthesised under controlled hydrothermal conditions. Here 1,3,5,7-tetraazatricyclo[3.3.1]decane [or hexamethylenetetramine (hmt)] has been used as a μ-(N,N′) bidentate spacer molecule. The prepared polymeric complex has been characterised by elemental and spectral analyses. The structure has been confirmed by a single crystal X-ray diffraction study. Magneto-structural correlation has been drawn from cryomagnetic susceptibility measurements (2–300 K) which unequivocally reflects very weak magnetic spin interactions among the long distant octahedral Ni(II) metal centres mediated by hmt and weak hydrogen bonding interactions between the adjacent zigzag one-dimensional polymeric chains carrying into a two-dimensional infinite polymeric framework.     

Natural Small Molecules in Gastrointestinal Tract and Associated Cancers: Molecular Insights and Targeted Therapies

Gastric cancer is one of the most common cancers of the gastrointestinal tract. Although surgery is the primary treatment, serious maladies that dissipate to other parts of the body may require chemotherapy. As there is no effective procedure to treat stomach cancer, natural small molecules are a current focus of research interest for the development of better therapeutics. Chemotherapy is usually used as a last resort for people with advanced stomach cancer. Anti-colon cancer chemotherapy has become increasingly effective due to drug resistance and sensitivity across a wide spectrum of drugs. Naturally-occurring substances have been widely acknowledged as an important project for discovering innovative medications, and many therapeutic pharmaceuticals are made from natural small molecules. Although the beneficial effects of natural products are as yet unknown, emerging data suggest that several natural small molecules could suppress the progression of stomach cancer. Therefore, the underlying mechanism of natural small molecules for pathways that are directly involved in the pathogenesis of cancerous diseases is reviewed in this article. Chemotherapy and molecularly-targeted drugs can provide hope to colon cancer patients. New discoveries could help in the fight against cancer, and future stomach cancer therapies will probably include molecularly formulated drugs.     

Halogen-containing tetrametallic aluminium alkoxides

New halogen-containing tetrametallic aluminium alkoxides of formula [Al{(mu-OEt)2AlMeCl}3] ( 2-cis; 2-trans), and [Al{(mu-OEt)2AlBr2}3] ( 4), have been synthesized by combining Al(OEt)3 and Me2AlCl (for 2) or EtAlBr2 (for 4). They were fully characterized by (1H, 27Al) NMR, IR, mp, elemental analysis, and single-crystal X-ray diffractometry. The chloride analogue of 4, [Al{(mu-OEt)2AlCl2}3] ( 3), prepared previously using a different route, was also prepared here by combining Al(OEt)3 and EtAlCl2.     

Temperature-dependent solvation dynamics of water in sodium bis(2-ethylhexyl)sulfosuccinate/isooctane reverse micelles

In this paper, for the first time, we report a detailed study of the temperature-dependent solvation dynamics of a probe fluorophore, coumarin-500, in AOT/isooctane reverse micelles (RMs) with varying degrees of hydration (w0) of 5, 10, and 20 at four different temperatures, 293, 313, 328, and 343 K. The average solvation time constant becomes faster with the increase in w0 values at a particular temperature. The solvation dynamics of a RM with a fixed w0 value also becomes faster with the increase in temperature. The observed temperature-induced faster solvation dynamics is associated with a transition of bound- to free-type water molecules, and the corresponding activation energy value for the w0 = 5 system has been found to be 3.4 kcal mol-1, whereas for the latter two systems, it is approximately 5 kcal mol-1. Dynamic light scattering measurements indicate an insignificant change in size with temperature for RMs with w0 = 5 and 10, whereas for a w0 = 20 system, the hydrodynamic diameter increases with temperature. Time-resolved fluorescence anisotropy studies reveal a decrease in the rotational restriction on the probe with increasing temperature for all systems. Wobbling-in-cone analysis of the anisotropy data also supports this finding.     

Surfactant tail length-dependent lipase activity profile in cationic water-in-oil microemulsions

The catalytic activity of Chromobacterium viscosum lipase (CV-lipase) was estimated across varying surfactant tail lengths (C-10-C-18) in water-in-oil (w/o) microemulsions of cationic surfactants containing four different hydroxyethyl-substituted head groups. An attempt to find a correlation, if any, between the activity of interfacially solubilized lipase and the varying surfactant tails was made for the first time in micellar enzymology. The second-order rate constant, k2, in lipase-catalyzed hydrolysis of p-nitrophenyl-n-hexanoate at pH 6.0 and 25 degrees C shows an improvement in enzyme activity (approximately 30-140%) across different head groups of amphiphiles with increasing tail lengths in varying solution compositions. Improvement of enzyme activity is prominent in ascending from C-10 to C-14/C-16, depending on the nature of polar head group. The hydrolytic activity of lipase in different surfactant (50 mM)/water/isooctane/n-hexanol with varying z= [alcohol]/[surfactant] (6.4 or 4.8) was amplified by 25-250% with increment in surfactant tail length in comparison with widely used cationic w/o microemulsions having solution compositions (z=16). As a notable outcome of this research, we found w/o microemulsions of 25 mM tetradecyltrimethylammonium bromide/water/isooctane/n-hexanol (z=8) producing the highest ever activity of lipase in any w/o microemulsions.     

Fluorescence properties of trans-ethyl-p-(dimethylamino) cinnamate in presence of bile acid host

The knowledge of the formation of bile acid micellar aggregates is of great importance because of the biological significance of these compounds and their pharmacological applications. The intramolecular charge transfer (ICT) fluorescence property of trans-ethyl-p-(dimethylamino) cinnamate is used to study the micelles formed by aggregation of three most important bile acids, viz. cholic acid, deoxycholic acid and chenodeoxycholic acid by steady state and picosecond time-resolved fluorescence spectroscopy. The ICT fluorescence band intensity was found to increase with concomitant blue shift with the addition of bile acids. The blue shift in ICT fluorescence maxima as well as decrease in nonradiative decay constants in presence of bile acids indicate the passage of the probe towards the micro domains formed from the aggregated bile acids. Binding constant of the probe with micelles as well as critical micelle concentration and average polarity parameter of the micellar environments were obtained from the variation of fluorescence intensity on increasing concentration of bile acids in the medium.     

Lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene: synthesis, characterization, and selective recognition of Hg2+ and its sensitivity toward pyrimidine bases

The structurally characterized lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene (L) exhibits high selectivity toward Hg(2+) among other biologically important metal ions, viz., Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+) as studied by fluorescence, absorption, and ESI MS. L acts as a sensor for Hg(2+) by switch-off fluorescence and exhibits a lowest detectable concentration of 1.87 ± 0.1 ppm. The complex formed between L and Hg(2+) is found to be 1:1 on the basis of absorption and fluorescence titrations and was confirmed by ESI MS. The coordination features of the mercury complex of L were derived on the basis of DFT computations and found that the Hg(2+) is bound through an N(2)O(2) extending from both the arms to result in a distorted octahedral geometry with two vacant sites. The nanostructural features such as shape and size obtained using AFM and TEM distinguishes L from its Hg(2+) complex and were different from those of the simple mercuric perchlorate. L is also suited to sense pyrimidine bases by fluorescence quenching with a minimum detection limit of 1.15 ± 0.1 ppm in the case of cytosine. The nature of interaction of pyrimidine bases with L has been further studied by DFT computational calculations and found to have interactions through a hydrogen bonding and NH-π interaction between the host and the guest.