Validation of a Gas Chromatography-Mass Spectrometry Method for the Measurement of the Redox State Metabolic Ratios Lactate/Pyruvate and β-Hydroxybutyrate/Acetoacetate in Biological Samples

The metabolic ratios lactate/pyruvate and β-hydroxybutyrate/acetoacetate are considered valuable tools to evaluate the in vivo redox cellular state by estimating the free NAD+/NADH in cytoplasm and mitochondria, respectively. The aim of the current study was to validate a gas-chromatography mass spectrometry method for simultaneous determination of the four metabolites in plasma and liver tissue. The procedure included an o-phenylenediamine microwave-assisted derivatization, followed by liquid-liquid extraction with ethyl acetate and silylation with bis(trimethylsilyl)trifluoroacetamide:trimethylchlorosilane 99:1. The calibration curves presented acceptable linearity, with a limit of quantification of 0.001 mM for pyruvate, β-hydroxybutyrate and acetoacetate and of 0.01 mM for lactate. The intra-day and inter-day accuracy and precision were within the European Medicines Agency’s Guideline specifications. No significant differences were observed in the slope coefficient of three-point standard metabolite-spiked curves in plasma or liver and water, and acceptable recoveries were obtained in the metabolite-spiked samples. Applicability of the method was tested in precision-cut liver rat slices and also in HepG2 cells incubated under different experimental conditions challenging the redox state. In conclusion, the validated method presented good sensitivity, specificity and reproducibility in the quantification of lactate/pyruvate and β-hydroxybutyrate/acetate metabolites and may be useful in the evaluation of in vivo redox states.     

Metal-matrix composites in the automotive industry: Opportunities and challenges

Metal-matrix composites offer considerable promise to help automotive engineers meet the challenges of current and future demands for recyclable, fuel-efficient, safe, and low-emission vehicles. These materials can be engineered to match the design requirements of automotive power-train or chassis components. Technological and infrastructural barriers tend to limit the implementation of these materials, but it is believed these barriers can be overcome and that metal-matrix composites can be applied in high-volume vehicle production. Reducing these barriers will require much effort by engineers and scientists, managers and planners at automotive manufacturers, and their suppliers. The result will be the gradual introduction of metal-matrix composites in high-volume vehicle production to satisfy customer desires while meeting regulatory requirements and competitive pressures.     

Mass-Balance Model of Pulmonary Oxygen Transport

A dynamic lumped-parameter model for pulmonary gas transport has been developed to characterize the lung and predict the effect of various parameter changes. The gas side of the lung is modeled as a series and parallel arrangement of five perfectly mixed, variable-volume compartments that correspond roughly to airway and alveolar regions. The blood side of the lung is modeled as a series of perfectly mixed, constant-volume compartments that represent the pulmonary capillary bed. From nonsteady mass balances, equations are derived which yield the time course of concentration for each compartment. Model simulations indicate that the oxygen-hemoglobin reaction does not reach equilibrium in the pulmonary capillaries, an assumption commonly made in analyses of pulmonary oxygen transport. Simulations also show the extent to which breathing amplitude and rate can affect the oxygen level in the blood leaving the lung. A comparison of simulations for a normal state and chronic obstructive lung disease (COLD) with identical input conditions demonstrates that the oxygen level in the blood leaving the lung is much lower in COLD. Also, the simulations are compared with experimental findings.     

Utilising semantic technologies for intelligent indexing and retrieval of digital images

The proliferation of digital media has led to a huge interest in classifying and indexing media objects for generic search and usage. In particular, we are witnessing a colossal growth in digital image repositories that are difficult to navigate using free-text search mechanisms, which often return inaccurate matches as they in principle rely on statistical analysis of query keyword recurrence in the image annotation or surrounding text. In this paper we present a semantically-enabled image annotation and retrieval engine that is designed to satisfy the requirements of the commercial image collections market in terms of both accuracy and efficiency of the retrieval process. Our search engine relies on methodically structured ontologies for image annotation, thus allowing for more intelligent reasoning about the image content and subsequently obtaining a more accurate set of results and a richer set of alternatives matchmaking the original query. We also show how our well-analysed and designed domain ontology contributes to the implicit expansion of user queries as well as the exploitation of lexical databases for explicit semantic-based query expansion.     

Thermogenic Effect from Nutritionally Enriched Coffee Consumption

Background  

The purpose of this study was to examine the effect of nutritionally enriched JavaFit™ (JF) coffee (450 mg of caffeine, 1200 mg of garcinia cambogia, 360 mg of citrus aurantium extract, and 225 mcg of chromium polynicotinate) on resting oxygen uptake (VO₂), respiratory exchange ratio (RER), heart rate (HR), and blood pressure (BP) in healthy and physically active individuals.     

Direct Synthesis and Sintering of Silicon Nitridenitanium Nitride Composite

Electrical discharge machining is an attractive machining technique which requires electrically conductive ceramic materials. Silicon nitride based composites with 35–40% of TiN possess electrical conductivity high enough to use this machining technique. The composite powder was prepared by combustion synthesis and densified by pressure sintering (sintering aids 6 wt% of Y₂O₃ and 4 wt% of A1,0₃). High fracture toughness, K _c 10.5 MPa^.m^1/2, is typical for the composite. It can be expected that this material can compete with pure silicon nitride in applications requiring complex machining.     

Mössbauer studies of illites and heat-treated illite as related to coal-conversion processes

Mossbauer spectra of iron species in the following illites were studied: Grundite, Fithian, Minerva, and New Albany. Spectra of samples of Fithian illite heated at temperatures of 225, 700, and 1000 °C were also obtained. Analyses of these spectra provide Mössbauer parameter values of iron species in the illites and heat-transformed illite for comparison with similar species found in coals containing illites and in coal process residues derived from them. The illites contain both ferric and ferrous species. Mössbauer parameters for one of the ferric species, designated M(2), are virtually the same as those of pyrite. The two species are therefore difficult to distinguish from one another. Values of the concentration of pyrite in coals and shales may be inflated if the pyrite concentration is measured by Mössbauer spectroscopy. Mössbauer spectra of the heat-treated illite samples reveal changes in iron distribution, principally at the 700 and 1000 °C levels, where there are found three and six different iron species respectively. These changes are accompanied by reduction of ferric to ferrous iron. This process should be integrated into any assessment of the iron chemistry which accompanies coal-conversion processes.     

Determination of diffusion coefficients of water in cellulose acetate membranes

The determination of the diffusion coefficient for water in various porosity cellulose acetate membranes by a gravimetric method, using a humidified carrier gas, is described. It was found to be impossible to obtain meaningful results for very porous membranes, although dense membranes gave limiting values of diffusion coefficient at high carrier gas velocities. This phenomenon is explained in terms of the dissipation of the heat of sorption by the forced convection provided by the carrier gas. The variation of diffusion coefficient with concentration of water in dense cellulose acetate is explained in terms of clustering of water molecules in the polymer at high concentration.     

Free and esterified sterols of cotton buds and anthers

Capillary gas liquid chromatography analyses were conducted on free and esterified sterol fractions of cotton (Gossypium hirsutum cv. Stoneville 213) floral buds and anthers. The free sterols of both cotton buds and anthers consist mainly of the common plant sterols sitosterol, stigmasterol and 24ζ-methylcholest-5-en-3β-ol. The composition of esterified sterols of cotton buds and anthers were similar, and consisted of pollinastanol, 31-norcycloartanol, cycloartenol, 31-norcycloartenol, 24-dehydropolinastanol and sitosterol. Desmosterol was also present in both the free and esterified sterols of anthers. The identities of the sterols were confirmed by gas chromatography-mass spectrometry analyses. Esterified sterols accounted for 46.7 and 88.7% of total sterols of cotton bud and anthers, respectively. The ratio of esterified sterol to free sterol per gram of tissue is about 8∶1 in anthers. The Δ⁵-sterols of the esterified sterols of cotton buds and anthers account for only 17 and 9.2% of the total sterols, respectively.