Mössbauer, X-ray, electrical and magnetic properties of lithium borosilicate glasses containing iron and manganese Part I. Mössbauer measurements

The effect of the replacement of MnO₂ by Fe₂O₃ on the oxidation states of iron in some lithium borosilicate glasses were studied using Mössbauer spectroscopy. DTA and infrared measurements showed the presence of two glassy phases, one of them containing iron and the other manganese. The Mössbauer spectra were measured at room temperature for all the glass samples. The spectra revealed the presence of Fe ions only in ferric state in both tetrahedral and octahedral coordination. Also, it was observed that the ratio between the number of iron ions in both coordination states has not changed with the increase of MnO₂ content.     

A Complete Classification of Curvature Collineations of Cylindrically Symmetric Static Metrics

Curvature collineations are symmetry directions for the Riemann tensor, as isometries are for the metric tensor and Ricci collineations are for the Ricci tensor. Complete listings of many metrics possessing some minimal symmetry have been given for a number of symmetry groups for the latter two symmetries. It is shown that a claimed complete listing of cylindrically symmetric static metrics by their curvature collineations [1] was actually incomplete and is completed here. It turns out that in this complete list, unlike the previous claim, there are curvature collineations that are distinct from the set of isometries and of Ricci collineations. The physical interpretation of some of the metrics obtained is given.     

On Commutativity of Rings With Derivations

Let R be a ring and d : R → R a derivation of R. In the present paper we investigate commutativity of R satisfying any one of the properties (i)d([x,y]) = [x,y], (ii)d(x o y) = xoy, (iii)d(x) o d(y) = 0, or (iv)d(x) o d(y) = x o y, for all x, y in some apropriate subset of R.     

Depolymerization Study of Pakistani Lignite Coal Influence of Pre‐treatments on Product Slate

Influence of pretreatments, i.e., demineralization and pre‐soaking in some solvents on the yields of liquefied products obtained from hydro‐depolymerization of Pakistani coal in a pool of hydrogen has been discussed. Results of hydrogenation experiments demonstrated that demineralizing the coal sample prior to liquefaction caused the yields to decrease compared with the virgin coal samples. The contribution of mineral matter of coal has been evaluated by comparing the yields of liquid products of virgin and leached samples. Increase in the yields obtained from the hydrogenation experiments of swollen coal samples was not satisfactorily significant.     

Association between the photodynamic loss of Bcl-2 and the sensitivity to apoptosis caused by phthalocyanine photodynamic therapy

We have reported that photodynamic therapy (PDT) using the photosensitizer phthalocyanine (Pc) 4 and red light damages the antiapoptotic protein Bcl-2. Recently, using transient transfection of Bcl-2 deletion mutants, we identified the membrane anchorage domains of Bcl-2 as necessary to form the photosensitive target. However, it is not clear how Bcl-2 photodamage sensitizes cells to Pc 4-PDT-induced apoptosis, whether overall cell killing is also sensitized or how up-regulation of Bcl-2 in tumors might make them more or less responsive to Pc 4-PDT. In this study we report on MCF-7c3 cells (human breast cancer cells expressing stably transfected procaspase-3) overexpressing wild-type Bcl-2 or certain deletion mutants in either a transient or a stable mode. By flow cytometric analysis of transiently transfected cells, we found that wild-type Bcl-2, Bcl-2delta33-54 and Bcl-2delta37-63 (each of which can be photodamaged) protected cells from apoptosis caused by Pc 4-PDT. In contrast, Bcl-2delta210-239, which lacks the C-terminal transmembrane domain and cannot be photodamaged, afforded no protection. We then evaluated the PDT sensitivity of transfected cell lines stably overexpressing high levels of wild-type Bcl-2 or one of the Bcl-2 mutants. Overexpression of wild-type Bcl-2, Bcl-2delta33-54 or Bcl-2delta37-63 resulted in relative resistance of cells to Pc 4-PDT, as assessed by morphological apoptosis or loss of clonogenicity. Furthermore, overexpression of Bcl-2 also inhibited the activation-associated conformational change of the proapoptotic protein Bax, and higher doses of Pc 4 and light were required to activate Bax in cells expressing high levels of Bcl-2. Many advanced cancer cells have elevated amounts of Bcl-2. Our results show that increasing the dose of Pc 4-PDT can overcome the resistance afforded by either Bcl-2 or the two mutants. PDT regimens that photodamage Bcl-2 lead to activation of Bax, induction of apoptosis and elimination of the otherwise resistant tumor cells.     

Dichotenone-a and -b: two new enones from the marine brown alga Dictyota dichotoma (Hudson) Lamour

Marine brown alga Dictyota dichotoma (Dictyotaceae) collected from Karachi coast of Arabian Sea yielded two new (1 and 2) enones (dolastane-diterpenoids) named: dichotenone-A and -B along with an olide (loliolide, 3) as a new source. Their structures have been characterized with the aid of 2D-NMR spectroscopic techniques.     

Preparation and Properties of Aramid-Silica Hybrids with Inter-Phase Bonding Through (3-glycidoxypropyl)-trimethoxysilane

Nano-composites from aramid-silica system have been prepared via sol-gel process. Poly (phenyleneterephthalamide) copolymer chains were prepared by reacting a mixture of p- and m-phenylenediamines with terephthaloyl chloride in dimethylacetamide used as solvent. The sol-gel process in the polymer matrix was carried out through hydrolysis and condensation of a mixture of tetraethoxysilane and (3-glycidoxypropyl) trimethoxysilane. The latter was used to develop linkage, on one hand with silica network structure using alkoxy groups and on the other hand with aramid chains at its secondary amine groups through glycidal groups of silane. Mutual interaction between the two disparate phases aramid and silica network was thus created. Thin films of the composites containing different proportions of silica ranging from 5.0 to 25.0-wt% were cast by the solvent elution technique. The α-relaxation temperature associated with the glass transition was measured by the dynamic mechanical thermal analysis. The results showed an increase in the glass transition temperature from 328°C for the pure aramid to 352°C for the hybrid materials containing 25-wt% silica, an indicative of the increased interfacial interaction between the two phases. Films having relatively low silica content were flexible and transparent, but those with high silica content were opaque and brittle. These films were tested for their tensile strength, modulus and toughness. The mechanical strength of the composites as compared to the pure aramid increased initially but with further addition of silica the strength decreased. The initial increase can be explained due to increased interfacial interaction between the two phases, however agglomeration of silica particles was responsible for decreasing strength at higher silica contents.     

Metal organic chemical vapour deposition (MOCVD) of bone mineral like carbonated hydroxyapatite coatings

For the first time, the MOCVD technique has been used to deposit carbonated hydroxyapatite onto Ti6AL4V substrates using volatile monomeric (liquid) complexes [Ca(beta-diketonate)(2)(L)] and P(OEt)(3).     

Tests for liquid chromatographs

Summary The paper describes tests for liquid chromatographs to assess the autosampler and pump flow rate precision; suitability of the instrument for normal phase chromatography; UV detector performance; and external band broadening characteristics. Tests for mixing and proportioning characteristics of solvent pumps and performance of diode array detectors are also considered. These tests are designed to evaluate the performance of both newly released liquid chromatography equipment and equipment already in operation. Data from evaluations carried out by instrument manufacturer’s and suppliers is reported and discussed. This data offers specifications to a common format for initial selection of instruments prior to purchase.