Complexes of Tin(IV) Tetrachloride with 3-Formylpyridine Semicarbazone and Thiosemicarbazones

The reaction of tin(IV) tetrachloride with 3-formylpyridine semicarbazone and different 3-formylpyridine thiosemicarbazones produces [Sn(HL)CL 3 ][SnCl 5 ] where HL stands for the neutral ligand. The tin(IV) complexes were characterized using a variety of spectroscopic techniques. Coordination through the pyridine nitrogen occurs in all cases. Solvation studies in DMSO indicated that dissociation of the ligands and their complete replacement by solvent molecules occurs.     

Binding energy of a hydrogen impurity in an f.c.c. lattice

Hydrogen impurities in f.c.c. lattices, Pd metal for example, can occupy two interstitial sites, with tetrahedral or octahedral symmetries. Using the Husimi cactus to represent the f.c.c. lattice and two clusters to describe the two different interstices, we calculate the densities of states and the occupation numbers at the impurity site and on its nearest neighbours. The binding energies are calculated and plotted against the hopping integral between the hydrogen and its neighbours (t_a). We found that the octahedral site is the stable one for values of t_a from 0 to 1.5 eV.     

Brasiliensic and isobrasiliensic acids: isolation from Calophyllum brasiliense Cambess. and anti-Helicobacter pylori activity

The occurrence of chromanone derivatives has been noticed as a distinctive feature of the genus Calophyllum (Calophyllaceae). Previous studies have demonstrated that the extract of the stem bark of Calophyllum brasiliense and its chromanone-rich fractions show anti-ulcer activity in murine gastric ulcer models. In this work, brasiliensic and isobrasiliensic acids, the two main compounds of the n-hexane extract of the stem bark extract of C. brasiliense, were isolated by flash chromatography using silica gel impregnated with silver nitrate and their structures were elucidated by NMR techniques and mass spectrometry. ¹³C NMR data is available for the first time for both compounds. Brasiliensic and isobrasiliensic acids showed good in vitro bacteriostatic activity against Helicobacter pylori, and are responsible, at least in part, for the bacteriostatic anti-H. pylori activity of the n-hexane extract of the stem bark of C. brasiliense.     

Partially carboxymethylated cotton dust waste for sorption of textile wastewater coloured with the cationic dye Basic Blue 41 as a model: synthesis,regeneration and biodegradability

The removal of residual dyes in coloured textile wastewaters is mandatory, and a significant portion of the dyes used are cationic. Textile factories mainly process cotton yarns, and 8 % of this virgin feedstock is lost as cotton dust waste (CDW). Using factorial experimental design, this dust was derivatised with monochloroacetic acid (MCAA) to produce a partially carboxymethylated cellulose (CM^?-CDW) with NaOH, MCAA and isopropanol for the retention of Basic Blue 41 dye (BB 41) (column and batch), and biodegradability was investigated. The dye retention efficiency was examined with additional experiments varying the initial concentration, contact time and addition of salts. Heteronuclear multiple bonding correlation-nuclear magnetic resonance confirmed the covalent insertion of CM^? groups in the cellulosic fibres. The selected matrix provided a dye sorption of 58.33 (column) and 64.50 mg/g (batch). The Langmuir isotherm was a good fit to the sorption data. The efficiency of uptake of BB 41 was predominantly dictated by the concentration of alkali in the matrix synthesis. Biodegradability by cellulases was similar when using uncharged and dye-charged matrices. The latter were fully regenerated by washing in dilute acid. Retention was proportional to the initial dye concentration and the contact time required to reach equilibrium, which was longer for higher dye concentrations. The addition of 10 mmol/l NaCl decreased BB 41 retention by 50 %. Therefore, CM^?-CDW proved effective for the removal of the cationic dye BB 41 and thus represents an important alternative in the treatment of coloured textile effluents.     

Production and Stability of Protease from <Emphasis Type="Italic">Candida buinensis</Emphasis>

Cow raw milk from dairy cooperatives was examined for its microbial composition. Among the isolates identified, 17.6% were yeasts. The most frequent genus was Candida, although members belonging to the genera Brettanomyces, Dekkera, and Geotricum were also identified. Although qualitative and quantitative tests for extracellular proteolytic activity were positive for all the species isolated, Candida buinensis showed the highest response (23.5 U/mg); therefore, it was selected for subsequent investigation. The results of fermentations carried out at variable temperature, pH, and soybean flour concentration, according to a 2³ full factorial design, demonstrated that this yeast ensured the highest production of extracellular proteases (573 U/mL) when cultivated at 35 °C, pH 6.5, and using soybean flour concentrations in the range 0.1–0.5% (w/v). The cell-free supernatants showed the highest activity at 25 °C and pH 7.0, and satisfactory stability in the ranges 25–30 °C and pH 7–9. The first-order rate constants of protease inactivation in the cell-free supernatants were calculated at different temperatures from semi-log plots of the residual activity versus time and then used in Arrhenius and Eyring plots to estimate the main thermodynamic parameters of thermoinactivation (E* = 40.0 kJ/mol; ΔH* = 37.3 kJ/mol; ΔS* = −197.5 J/mol K; ΔG* = 101 kJ/mol).     

Platinum(II) complexes of 2-, 3-, and 4-formyl-pyridine thiosemicarbazone and 2-, 3- and 4-acetyl-pyridine thiosemicarbazone

Seven platinum(II) complexes isolated from thiosemicarbazones derived from 2-, 3- and 4-formylpyridine and 2-, 3-, and 4-acetylpyridine have been characterised by microanalyses, molar conductivities and by their i.r. and ¹H-n.m.r. spectra.     

Magneto-optical effects in Eu chalcogenides

To discuss the Faraday and Voigt effects in the Eu chalcogenides we derive a general expression for the polarizability of a system in which the important electronic transitions are from localized to itinerant orbitals. This expression is applied to a model system in which the electronic transitions take place from a 4f orbital to a 5dt_2g Wannier orbital centered at the same cell. We treat in detail the matrix elements of the electric dipole operator taking into account the many-body character of the 4f shell. The Coulomb potential of the intermediate state localized hole is included explicitely within a simple approximation. We present a numerical calculation of the frequency dependent Verdet constant and Voigt phase shift for the paramagnetic and ferromagnetic phases of EuSe. The fitting of the Verdet constant to the experimental results is fairly good and allows us to estimate the value of the integral (4f|r|5d) ? 4 × 10^?9 cm.     

An improved approach for flow-based cloud point extraction

Novel strategies are proposed to circumvent the main drawbacks of flow-based cloud point extraction (CPE). The surfactant-rich phase (SRP) was directly retained into the optical path of the spectrophotometric cell, thus avoiding its dilution previously to the measurement and yielding higher sensitivity. Solenoid micro-pumps were exploited to improve mixing by the pulsed flow and also to modulate the flow-rate for retention and removal of the SRP, thus avoiding the elution step, often carried out with organic solvents. The heat released and the increase of the salt concentration provided by an on-line neutralization reaction were exploited to induce the cloud point without an external heating device. These innovations were demonstrated by the spectrophotometric determination of iron, yielding a linear response from 10 to 200 μg L⁻¹ with a coefficient of variation of 2.3% (n = 7). Detection limit and sampling rate were estimated at 5 μg L⁻¹ (95% confidence level) and 26 samples per hour, respectively. The enrichment factor was 8.9 and the procedure consumed only 6 μg of TAN and 390 μg of Triton X-114 per determination. At the 95% confidence level, the results obtained for freshwater samples agreed with the reference procedure and those obtained for digests of bovine muscle, rice flour, brown bread and tort lobster agreed with the certified reference values. The proposed procedure thus shows advantages in relation to previously proposed approaches for flow-based CPE, being a fast and environmental friendly alternative for on-line separation and pre-concentration.     

Pulsed voltammetric/amperometric detection of polycyclic aromatic sulfur heterocycles (PASHs) at the gold disc electrode for studies in petroleum asphalts

This work describes the voltammetric and amperometric behavior of a high number of PASHs (sulfides, thiophenes, benzothiophenes, dibenzothiophenes, indenothiophenes, naphtothiophenes, thienothiophenes, phenanthrothiophenes, and acenaphtothiophenes) at gold disc electrodes aiming at their identification and determination in petroleum asphalts. The adsorption/redox processes expected for sulfur compounds at gold electrodes could be observed in all the studied PASHs in DMSO and hydromethanolic medium. Differential pulse (DP) voltammetry in non-aqueous solutions (0.1 mol L⁻¹ NaClO₄ in DMSO) was approached for determining non-volatile PASHs in asphalts submitted to different aging processes. It was found herein that the DP voltammetric monitoring of PASH oxidation at + 0.7 V (vs. Ag/AgCl/LiCl 3 mol L⁻¹) for virgin/aged asphalts can be used for the comparative study of asphalts based on the consumption of PASHs. Additionally, pulsed amperometric detection (PAD) in hydroalcoholic solution (10 mmol L⁻¹ acetate buffer in 65% methanol) coupled with a chromatographic separation was approached for determining volatile PASHs in asphalts submitted to thermal decomposition processes. A detection cycle of 2 s involving oxidative (0.4 s at + 0.4 V) and reductive (1.2 s at − 1.0 V) cleaning pulses after a detection pulse of − 0.8 V (0.4 s) applied successively to the gold electrode (vs. Pd/PdO) was found to be optimal for regenerating the gold surface during successive chromatographic runs of PASHs. Thus, reversed-phase liquid chromatography (LC)–coupled PAD was found useful to separate a complex mixture of PASHs. The optimized PAD and LC separation was further applied to investigate the presence of electroactive PASHs as volatile compounds in asphalt fumes generated at 260 °C.

     

Microscopic evaluation of proliferative disorders in the gerbil female prostate: evidence of aging and the influence of multiple pregnancies

The gerbil female prostate is located paraurethrally and has all the histological components of the male prostate, like secretor epithelium and fibromuscular stroma. This gland, like the prostate in males, is targeted by testosterone action, which promotes morphofunctional development. Furthermore, estrogens are required to maintain the male and female prostate and this gland presents both estrogen receptors (ER-α and ER-β). In the present work the structural and morphometric-stereological and serological aspects, as well as the quantification of the incidence, multiplicity and percentage of acini affected by different lesions were analyzed. Animals were divided into four groups: five adult nuliparous (AN) gerbils; five adult multiparous (AM) gerbils; five senescent nulliparous (SN) gerbils; five senescent multiparous (SM) gerbils, and were weighed and sacrificed by CO(2) inhalation. The ventral prostate was dissected out, weighed and fixed to perform histological and morphometric-stereological analysis and quantification of prostate disorders. A high rate of lesions, mainly dysplasia, was identified in tissue from senescent multiparous and adult multiparous animals. Prostatitis was found mainly in SN animals, while dysplasia, hyperplasia, neoplasia, PIA and adenocarcinoma were common in SM ones. Although the proliferative lesion incidence was high in AN group, it was highest in the SM group. The hormonal events which occur due to the estrous cycle in female gerbils (after and before each pregnancy) may be responsible for the high number of lesions observed in our study and all the data presented herein lead us to assume that pregnancy promotes augmentations in both the incidence and the multiplicity of proliferative disorders in the gerbil female prostate since progesterone levels remain high during pregnancy.