Weak n-injective and weak n-fat modules

Czechoslovak Mathematical Journal - We introduce and study the concepts of weak n-injective and weak n-flat modules in terms of super finitely presented modules whose projective dimension is at...     

Iron cross-linked carboxymethyl cellulose—gelatin complex coacervate beads for sustained drug delivery

The formation and smooth recovery of ibuprofen encapsulated in microcapsules using gelatin and carboxymethyl cellulose (CMC) complex coacervation without glutaraldehyde were the objectives of this investigation. The microcapsules were recovered as ionically cross-linked beads using aqueous ferric chloride in 50 vol.% of 2-propanol. A physical mixture of CMC/gelatin (FP1) and CMC alone (FP2) beads was also prepared for comparison. The drug-entrapment efficiency of complex coacervate beads (FP3-FP5) was dependent on the drug-to-polymer ratio and was in the range of 86–92 mass %. Beads prepared with the highest ratio of the drug (FP5) exhibited the lowest entrapment. FP1 and FP2 beads exhibited an entrapment efficiency of 98.5 mass % and 91.3 mass %, respectively. Infrared spectroscopy (FTIR) revealed different functional groups in complex coacervate, physical mixture and FP2 beads. Optical and scanning electron microscopy revealed the distinct appearance and surface morphology of the various beads. The stable and crystalline nature of ibuprofen in the beads was confirmed by FTIR and differential scanning calorimetry (DSC), respectively. Ibuprofen release from FP1 and FP2 beads was very slow and unsuitable for oral delivery. The bead prepared by complex coacervation (FP5) showed a better release profile over 48 h and could be developed as a sustained drug delivery system.     

Flow boiling heat transfer study of R-134a/R-290/R-600a mixture in 9.52 and 12.7 mm smooth horizontal tubes: Experimental investigation

A detailed experimental investigation is carried out to study the flow boiling heat transfer behavior of R-134a/R-290/R-600a (91%/4.068%/4.932% by mass) refrigerant mixture in smooth horizontal tubes of diameter 9.52 and 12.7 mm. The heat transfer coefficients of the mixture are experimentally measured under varied heat flux conditions for stratified flow patterns using a coaxial counter-current heat exchanger test section. The tests are conducted for refrigerant inlet temperatures between ?9 and 5 °C and mass flow rates ranging from 3 to 5 g s^?1. Kattan–Thome–Favrat maps are used to confirm the flow patterns for the tested conditions. The magnitude of the heat transfer coefficient with respect to flow patterns and different mechanisms of boiling are discussed. The heat transfer coefficient of the refrigerant mixture is also compared with that of R-134a for selected working conditions. The significance of nucleate boiling in the overall heat transfer process under these testing conditions is highlighted.     

Convective heat-transfer rate distributions over a missile shaped body flying at hypersonic speeds

Experiments are carried out with air as the test gas to obtain the surface convective heating rate on a missile shaped body flying at hypersonic speeds. The effect of fins on the surface heating rates of missile frustum is also investigated. The tests are performed in a hypersonic shock tunnel at stagnation enthalpy of 2 MJ/kg and zero degree angle of attack. The experiments are conducted at flow Mach number of 5.75 and 8 with an effective test time of 1 ms. The measured stagnation-point heat-transfer data compares well with the theoretical value estimated using Fay and Riddell expression. The measured heat-transfer rate with fin configuration is slightly higher than that of model without fin. The normalized values of experimentally measured heat transfer rate and Stanton number compare well with the numerically estimated results.     

Single crystal X-ray analysis of the electronic structure of the thermoelectric material Sn1?xGexTe

The precise bonding and the electronic structure of the thermoelectric material Sn_1−x Ge _x Te with two different doping levels viz., x = 0.12 and x = 0.25 have been determined using single crystal X-ray data and maximum entropy method (MEM). The thermal vibration parameters of the individual atoms in these two systems have also been studied and reported. The electron densities at the middle of the bond along [1 0 0] direction are found to be 0.346 e/?³ and 0.359 e/?³ for x = 0.12 and 0.25, respectively, showing different strengths of the bonding.     

A Stability-Indicating LC Method for Assay of Topotecan Hydrochloride

This paper describes the development of a stability-indicating high-performance liquid chromatographic (HPLC) method for quantitative determination of topotecan hydrochloride, a semi-synthetic derivative of camptothecin and anti-tumor drug with topoisomerase I-inhibitory activity. Chromatographic separation was achieved on a C₁₈ column with a mixture of phosphate buffer and acetonitrile as mobile phase. The method was validated for linearity, accuracy, precision, and robustness. Forced degradation studies were performed by treating bulk samples of topotecan hydrochloride with acid (0.5 M hydrochloric acid), base (0.5 M sodium hydroxide), oxidizing agent (10% v/v hydrogen peroxide), heat (60 °C), and UV light (254 nm).     

Growth and XRD analysis of the diluted magnetic semiconductor Zn1‐xNixO

Diluted magnetic semiconductor compound Zn_1‐xNi_x O (x =0.01, 0.02, 0.03, 0.04 and 0.05) was prepared by sol‐gel method and characterized using powder XRD for the distribution of electrons and bonding in the unit cell. The electronic structural studies of this material were carried out by maximum entropy method (MEM) for the quantitative and qualitative measurement on the inclusion and the effect induced on bonding by Ni doping. The spatial arrangement of charge and the bonding behavior of this material were analyzed from 3D, 2D and 1D density distributions. The evidence for the addition of Ni in the host lattice of Zn is realized. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

C2-symmetric recyclable organocatalyst for enantioselective Strecker reaction for the synthesis of α-amino acid and chiral diamine--an intermediate for APN inhibitor

Recyclable chiral amide-based organocatalyst 5 efficiently catalyzed asymmetric Strecker reaction of various aromatic and aliphatic N-benzhydrylimines with ethyl cyanoformate as cyanide source at -10 °C to give a high yield (95%) of α-aminonitriles with excellent chiral induction (ee, up to 99%) with the added advantage of recyclability. Based on experimental observations a probable mechanism was proposed for this reaction. This protocol with catalyst 5 was extended for the synthesis of (R)-phenylalanine and pharmaceutically important drug intermediate (R)-3-phenylpropane-1,2-diamine in high yield with high enantioselectivity.