Formation and stability criteria for amorphous Ge alloy films

Formation and stability of room-temperature deposited amorphous (a-) alloy films of Ge with Ag, Au, Cu, Ni, Fe, Ga, In, Sn, Sb, Ni, Bi and Nb have been studied, using differential thermal analysis and electron microscopy, as a function of various parameters such as: solubility of alloying element (in c-Ge), its melting point, atomic size and electonegativity. It has been shown that the composition range R, up to which amorphous alloy films are obtained, is affected by the solubility of the alloying element and its melting point. The effect of solubility S is dominant when S > 1 at%. However, for $\text{S ? 1}\text{at}\text{\%}$, the range is entirely governed by the melting point of the alloying element. Solubility and melting point have also been found to play a decisive role in stabilizing the amorphous phase of Ge. However, atomic size and electronegativity differences do not seem to play any important role in either the formation or stability of the amorphous phase.     

Metal catalyst-free direct α-iodination of ketones with molecular iodine

Ketones are directly converted to the corresponding α-iodoketones in good yields with molecular iodine under metal catalyst-free conditions. A significant difference in the reactivities was observed for aliphatic and aromatic ketones; whereas aliphatic ketones reacted smoothly at room temperature giving a mixture of 1-iodo, 3-iodo and 1,3-diiodoketones with predominant formation of the 3-iodo product, the α-iodination of aromatic ketones proceeded conveniently under heating to give good yields of α-iodo products.     

Efficacy and safety of Stephania glabra: an alkaloid-rich traditional medicinal plant

Stephania glabra (Roxb.) Miers (Menispermaceae) has long been used for the treatment of asthma, tuberculosis, dysentery, hyperglycaemia, cancer, fever, intestinal complaints, sleep disturbances and inflammation in many Asian countries. It mainly contains alkaloids and, until now, over 30 alkaloids such as bisbenzylisoquinolines, hasubanalactams, berberines and aporphines have been isolated from its tuber. Most of its traditional medicinal activities are scientifically approved by various in vitro and in vivo studies. It shows remarkable anti-psychotic, anti-diabetic, antipyretic, analgesic, antimicrobial and anti-hypertensive activities. This work includes comprehensive information on the ethnobotany, chemistry and pharmacology of S. glabra. This review also focuses on the future perspectives with main emphasis on the establishment of therapeutic index and safety index of the plant. This review concludes that S. glabra has a great potential to treat various diseases, and could be used as a source for novel healthcare products in the near future, which needs further studies.     

Perturbation solution for secondary bifurcation in the quadratically-damped Mathieu equation

This paper concerns the quadratically-damped Mathieu equation:

     

Calcium phosphate bioceramics and bioceramic composites

This paper reviews selected aspects of research work carried out in bioceramics and bioceramic composites at the Ceramics Laboratory IIT, Bombay, India. The focus here is in understanding and developing calcium hydroxyapatite (HA) bioceramics and biocomposites, including calcium hydroxyapatite-titanium (HA-Ti) and calcium hydroxyapatite-polymethylmethacrylate (HA-PMMA). Research involving apatite-wollastonite (AW) bioglass ceramics and bioceramic composites of AW with titanium as well as with polymethylmethacrylate will be presented in a future article. HA powders were precipitated from solutions with varying Ca/P ratios and calcined at a range of temperatures to investigate their structural evolution. HA-Ti composites were prepared by powder metallurgical processes using HA powders calcined at 400 °C, followed by compaction at 600 MPa and subsequent sintering at 1,000–1,200 °C. HA-PMMA composites containing up to 40 wt% PMMA were prepared by hot pressing at 150 °C and 150 MPa pressure. The phases present in the various materials were identified by X-ray diffraction (XRD) and functional groups by FTIR, while the sample morphologies were investigated by SEM. The bioactivity of the composites was evaluated by soaking them in simulated body fluid (SBF) for 7 days, to evaluate their apatite-forming ability (a key indicator of bioactivity). The results obtained are interpreted to aid in the development of “design rules” for the use of such biocomposite materials in specific biomedical application.     

Evaluation of direct analysis in real time mass spectrometry for onsite monitoring of batch slurry reactions

Batch slurry reactions are widely used in the industrial manufacturing of chemicals, pharmaceuticals, petrochemicals and polymers. However, onsite monitoring of batch slurry reactions is still not feasible in production plants due to the challenge in analyzing heterogeneous samples without complicated sample preparation procedures. In this study, direct analysis in real time mass spectrometry (DART-MS) has been evaluated for the onsite monitoring of a model batch slurry reaction. The results suggested that automation of the sampling process of DART-MS is important to achieve quantitative results. With a sampling technique of manual sample deposition on melting point capillaries followed by automatic sample introduction across the helium beam, relative standard deviation (RSD) of the protonated molecule signals from the reaction product of the model batch slurry reaction ranged from 6 to 30%. This RSD range is improved greatly over a sampling technique of manual sample deposition followed by manual sample introduction where the RSDs are up to 110%. Furthermore, with the semi-automated sampling approach, semi-quantitative analysis of slurry samples has been achieved. Better quantification is expected with a fully automated sampling approach.     

Detection and identification of alkylphosphonic acids by positive electrospray ionization tandem mass spectrometry using a tricationic reagent

The retrospective detection and identification of degradation products of chemical warfare agents are of immense importance in order to prove their spillage and use. A highly sensitive liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method--using an imidazolium-based tricationic reagent--was developed for the detection and identification of the anionic degradation products of nerve agents. A commercially available solution of 1,3-imidazolium-bis-(1-hexylbenzylimidazolium) trifluoride (IBHBI) formed adducts with alkylphosphonic acids (APAs), allowing detection of the APAs by positive mode ESI-MS. Tandem mass spectrometry was used for the unambiguous identification of the APAs. Parameters influencing the formation and stability of these adduct during mass spectrometric analysis, such as solvent composition, concentration of IBHBI, effect of pH and interferences by salts, were optimized. The absolute limits of detection (0.1 ng) for achieved for the APAs were better than those previously reported, and linear dynamic ranges of 10-2000 ng mL(-1) were achieved. The method was repeatable with a relative standard deviation ≤7.3%. APAs present in aqueous samples provided by the Organization for the Prohibition of Chemical Weapons during the 22(nd) and 24(th) Official Proficiency tests were detected and identified as IBHBI adducts. The added advantage of this method is that low-mass analytes are detected at higher mass, thus obviating the problem with background noise at low mass.     

Characterization and modeling of nonlinear hydrophobic interaction chromatographic systems

A general rate model was employed in concert with a preferential interaction quadratic adsorption isotherm for the characterization of HIC resins and the prediction of solute behavior in these separation systems. The results indicate that both pore and surface diffusion play an important role in protein transport in HIC resins. The simulated and experimental solute profiles were compared for two model proteins, lysozyme and lectin, for both displacement and gradient modes of chromatography. Our results indicate that a modeling approach using the generate rate model and preferential interaction isotherm can accurately predict the shock layer response in both gradient and displacement chromatography in HIC systems. While pore and surface diffusion played a major role and were limiting steps for proteins, surface diffusion was seen to play less of a role for the displacer. The results demonstrate that this modeling approach can be employed to describe the behavior of these non-linear HIC systems, which may have implications for the development of more efficient preparative HIC separations.