General spherically symmetric elastic stars in relativity

The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modeling of star interiors possessing elastic properties such as the ones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are reviewed, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. Specific examples are provided satisfying the dominant energy condition and admitting a constitutive equation, including a static two-layer star ‘toy model’ consisting of an elastic core surrounded by a perfect fluid corresponding to the interior Schwarzschild solution matched to the vacuum Schwarzschild solution. This paper extends and generalizes the pioneering work by Magli and Kijowski (Gen Relat Gravit 24:139, 1992), Magli (Gen Relat Gravit 25:1277, 1993; 25:441, 1993), and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers (Karlovini and Samuelsson in Class Quantum Grav 20:363, 2003; 21:1559, 21:4531, 2004).     

An HPLC method for the determination of adenosine diphosphate: An important marker of hexokinase activity in metabolic diseases

Hexokinases play a critical role in the cellular uptake and utilization of glucose. As such, they are of fundamental importance to all cells. By catalyzing glucose to produce glucose‐6‐phosphate, hexokinases control the first irreversible step of glucose metabolism and initiate all major pathways of glucose consumption. Our objective was to develop and validate highly sensitive and selective high‐performance liquid chromatography with photodiode array detector (HPLC‐PDA) assays allowing the determination of adenosine diphosphate, which was used for the determination of hexokinase activity. Samples were analyzed by HPLC‐PDA using a C₁₈ analytical column (250 × 4.6 mm) for chromatographic separation. Optimal detection was achieved based on isocratic elution with a mobile phase consisting of a mixture of sodium phosphate monobasic buffer and methanol. This method met all of the requirements of specificity, sensitivity, linearity, precision, accuracy and stability generally accepted in bioanalytical chemistry and was successfully applied to a study of hexokinase activity in an alloxan‐induced diabetic rat model. Determination of hexokinase activity will permit characterization of cellular metabolic state in many diseases, such as cancer and diabetes.     

Consumption of calcium hydroxide and formation of C–S–H in cement pastes

The pozzolanic properties of the equilibrium catalyst (Ecat), an abundant waste from fluid catalytic cracking units of oil refineries, have been studied in cementitious matrices. The consumption of calcium hydroxide is usually taken as a means to assess the pozzolanicity of a material, ignoring the formation of C–S–H and other hydrates, the main product of the pozzolanic reaction. The use of thermal analysis methods allows the identification and quantification of the products of the hydration reaction, based on the loss of chemically combined water of phases present in a cementitious matrix. In the present study, TG/DTG techniques were used to quantify the amount of C–S–H + ettringite, C–A–S–H + C–A–H, and calcium hydroxide in cement–Ecat pastes, containing 0–40 % Ecat, aged for 1–28 days. The influence of the content of these phases on the mechanical properties of the resulting samples was also investigated by axial compression. The results further confirmed the pozzolanic activity of Ecat, so that the production of C–S–H and C–A–S–H increased with the aging time, but in a smaller amount than in the reference paste. The compressive strength test showed that the pastes containing 10 % Ecat, aged for 14 and 28 days, presented improved properties as compared to the corresponding references.     

Theoretical study of Au/SAPO-11 catalyst and its potential use in thiophene HDS

Quantum chemistry calculations were carried out, using ONIOM2 methodology, in order to investigate the thiophene interaction with gold supported on silicoaluminophospates molecular sieves (Au/SAPO-11) catalysts. Two models were studied, one containing one Au atom per site, and the other with two Au atoms per site. Thiophene adsorption was found to be η¹ type. This adsorption presents a ΔH of ?13.2 and ?9.7 kcal/mol, for the models with one Au atom (Au/SAPO-11), and two Au atoms (Au₂/SAPO-11), respectively. The partial hydrogenation of the thiophene–Au/SAPO-11 and thiophene–Au₂/SAPO-11 complexes gives 2,5-dihydrothiophene (DHT), with a ΔH of ?23.0 and ?36.8 kcal/mol, respectively. 2-Butene production was found in both models with further hydrogenation. Likewise the direct butadiene elimination is achieved, but only with the separated Au dimer (ΔH = ?17.5 kcal/mol).     

Mechanisms of the gastric antiulcerogenic activity of Anacardium humile St. Hil on ethanol-induced acute gastric mucosal injury in rats

Leaves and bark infusions Anacardium humile St. Hil. (Anacardiaceae), known as in Brazil as "cajuzinho do cerrado", have been used in folk medicine as an alternative treatment for ulcers and gastritis. This study evaluated the gastroprotective activity of an ethyl acetate extract of the leaves of A. humile (AcF) and the mechanism involved in this gastroprotection. Pretreatment concentrations (50, 100, 200 mg x kg?1) were administered by gavage. Following a 60 min. period, all the rats were orally administered 1 mL of absolute ethanol. One hour after the administration of ethanol, all groups were sacrificed, and the gastric ulcer index was calculated. Prostaglandin PGE? concentration, gastric adherent mucous, and the participation of nitric oxide (NO) and sulfhydryl compounds in the gastroprotection process were also analyzed using the most effective tested dose (50 mg x kg?1). A histological study of the glandular stomach for the evaluation of the epithelial damage and mucus content was also performed. AcF significantly reduced the gastric damage produced by ethanol. This effect was statistically significant for the 50 mg x kg?1 group compared to control. Also, it significantly increased the PGE? (by 10-fold) and mucous production, while pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) or N-ethylmaleimide (NEM) completely abolished the gastroprotection. AcF has a protective effect against ethanol, and this effect, might be due to the augmentation of the protective mechanisms of mucosa.     

Optical properties of red, green and blue emitting rare earth benzenetricarboxylate compounds

Red, blue and green emitting rare earth compounds (RE³⁺=Eu³⁺, Gd³⁺ and Tb³⁺) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H₂O)₂], [RE(TLA)(H₂O)₄] and [RE(TMA)(H₂O)₆], except for Tb-TMA compound, which was obtained only as anhydrous. Phosphorescence data of Gd³⁺-(BTC) complexes showed that the triplet states (T) of the BTC³⁻ anions have energy higher than the main emitting states of the Eu³⁺ (⁵D₀) and Tb³⁺ (⁵D₄), indicating that BTC ligands can act as intramolecular energy donors for these metal ions. The high values of experimental intensity parameters (Ω₂) of Eu³⁺-(BTC) complexes indicate that the europium ion is in a highly polarizable chemical environment. Based on the luminescence spectra, the energy transfer from the T state of BTC ligands to the excited ⁵D₀ and ⁵D₄ levels of the Eu³⁺ and Tb³⁺ ions is discussed. The emission quantum efficiencies (η) of the ⁵D₀ emitting level of the Eu³⁺ ion have been also determined. In the case of the Tb³⁺ ion, the photoluminescence data show the high emission intensity of the characteristic transitions ⁵D₄→⁷F_J (J=0-6), indicating that the BTC ligands are good sensitizers. The RE³⁺-(BTC) complexes act as efficient light conversion molecular devices (LCMDs) and can be used as tricolor luminescent materials.     

Speciation of nickel by HPLC-UV/MS in pea nodules

A new and sensitive methodology based on normal phase HPLC has been developed for the speciation of nickel in low-complexity plant extracts. The method combines a silica stationary phase column, a 9:1 (v/v) hexane:ethanol mixture as mobile phase, and the detection of nickel complexes by either UV or MS. The developed methodology was applied to the speciation of nickel complexes in the cytoplasm of pea root nodules. Results obtained indicate that nickel citrate and nickel malate accounts for 99% of nickel present in pea nodule cytoplasm fraction. The low detection limit of the method (<0.2 nM) enables nickel speciation in non-hyperaccumulator plants.