Determination of levoglucosan from smoke samples using microchip capillary electrophoresis with pulsed amperometric detection

Separation and detection of native anhydrous carbohydrates derived from the combustion of biomass using an electrophoretic microchip with pulsed amperometric detection (PAD) is described. Levoglucosan represents the largest single component of the water extractable organics in smoke particles and can be used to trace forest fires or discriminate urban air pollution sources. Detection of levoglucosan and other sugar anhydrides in both source and ambient aerosol samples is typically performed by gas chromatographic (GC) separation with mass spectrometric (MS) detection. This method is cost, time, and labor intensive, typically involving a multistep solvent extraction, chemical derivatization, and finally analysis by GC/MS. However, it provides a rich wealth of chemical information as the result of the combination of a separation method and MS and exhibits good sensitivity. In contrast, microchip capillary electrophoresis offers the possibility of performing simpler, less expensive, and faster analysis. In addition, integrated devices can be fabricated and incorporated with an aerosol collection system to perform semicontinuous, onsite analysis. In the present report, the effect of the separation potential, buffer pH and composition, injection time, and pulsed amperometric detection parameters were studied in an effort to optimize both the separation and detection of anhydrous sugars. Using the optimized conditions, the analysis can be performed in less than a minute, with detection limits ranging from 22 fmol (16.7 microM) for levoglucosan to 336 fmol (258.7 microM) for galactosan. To demonstrate the capabilities of the device, a comparison was made between GC/MS and microchip electrophoresis using an aerosol source sample generated in a wood-burning chamber. A second example utilizing an ambient aerosol sample illustrates a matrix interference necessitating additional method development for application to samples not dominated by wood smoke.     

Heat shock and structural proteins associated with meat tenderness in Nellore beef cattle,a Bos indicus breed

Nellore beef cattle, a Bos indicus (Zebu) breed, is well adapted to tropical conditions and has allowed Brazil to become one of the largest producers of red meat. Nevertheless, B. indicus breeds are reported to have less tender meat than Bos taurus. This study was designed to identify genes associated with meat tenderness and thus provides important information for breeding programs. A group of 138 animals was evaluated for longissimus thoracis muscle shear force (SF). Animals with the highest and lowest SF values (six animals each) were then selected for protein abundance studies. Samples were subjected to two-dimensional gel electrophoresis (2-DE) followed by peptide sequencing through mass spectrometry (MS) to identify differentially expressed proteins associated with SF values. Seventeen differentially expressed spots were observed (p < 0.05) between the two groups. The 13 proteins identified included structural proteins (alpha actin-1, MLC1, MLC3, MLC2F and tropomyosin), related to cell organization (HSPB1 and HSP70), metabolism (beta-LG, ACBD6 and Complex III subunit I) and some uncharacterized proteins. Results confirm the existence of differentially expressed proteins associated with SF, which can lead to a better understanding of mechanisms involved in meat tenderness.     

Polyphenols and the Modulation of Gene Expression Pathways: Can We Eat Our Way Out of the Danger of Chronic Disease?

Plant-derived dietary polyphenols may improve some disease states and promote health. Experimental evidence suggests that this is partially attributable to changes in gene expression. The rational use of bioactive food components may therefore present an opportunity to activate or repress selected gene expression pathways and, consequently, to manage or prevent disease. It remains to be determined whether this use of bioactive food components can be done safely. This article reviews the associated controversies and limitations of polyphenol therapy. There is a paucity of clinical data on the rational use of polyphenols, including a lack of knowledge on effective dosage, actual chemical formulations, bioavailability, distribution in tissues, the effect of genetic variations, differences in gut microflora, the synergistic (or antagonistic) effects observed in extracts, and the possible interaction between polyphenols and lipid domains of cell membranes that may alter the function of relevant receptors. The seminal question of why plants make substances that benefit humans remains unanswered, and there is still much to learn in terms of correlative versus causal effects of human exposure to various nutrients. The available data strongly suggest significant effects at the molecular level that represent interactions with the epigenome. The advent of relatively simple technologies is helping the field of epigenetics progress and facilitating the acquisition of multiple types of data that were previously difficult to obtain. In this review, we summarize the molecular basis of the epigenetic regulation of gene expression and the epigenetic changes associated with the consumption of polyphenols that illustrate how modifications in human nutrition may become relevant to health and disease.     

Gel mechanical properties of milk whey protein–dextran conjugates obtained by Maillard reaction

The effect of Maillard reaction on the mechanical properties of whey protein isolate (WPI) heat-induced gels was evaluated. WPI and dextran (15–25 kDa) conjugates were obtained by controlled dry heating during storage at 60 °C and 63% relative humidity for 2, 5 and 9 days. Changes in browning intensity and content of free amino groups were used to estimate the Maillard reaction. A decrease in free amino groups of WPI was observed when increasing polysaccharide concentration and reaction time. An increase in both a* and b* CIE Lab colour parameters indicated the development of a reddish-brown colour, typical of the Maillard reaction. Uniaxial compression and stress relaxation tests were performed to measure the mechanical properties of mixed and conjugate gels. Maillard reaction significantly modified the mechanical properties of WPI/DX gels, and even prevented fracture when conjugate gels were subjected to 80% deformation in uniaxial compression test.     

Corneo-scleral contact lenses in an uncommon case of keratoconus with high hyperopia and astigmatism

Purpose

To analyse the visual quality achieved by fitting corneo-scleral contact lenses (CScL) in an uncommon case of bilateral keratoconus, high hyperopia and astigmatism.

Physicochemical properties and silicon content in wheat flour treated with diatomaceous earth and conventionally stored

This study was done to evaluate the physicochemical properties and to quantify the residual silicon in flour from wheat grains treated with different dosages of DE and stored in a conventional system for 180 days. Samples containing 10.0 kg of wheat grain were treated with 0.00, 2.00 and 4.00 g kg⁻¹ of DE and then homogenized and stored in cotton bags at 22 °C and 70 ± 5 g 100 g⁻¹ relative humidity. Physicochemical analyses were carried out at 0, 60, 120 and 180 days of storage. The experiment was conducted in a randomized design with a factorial 3 × 4 arrangement (three doses of DE × four storage periods), totaling 12 treatments, with three replicates for each treatment. The wheat flour samples were digested and the silicon residue quantification was conducted through colorimetry. The wheat treated with DE presented a lower test weight compared with control, +b^∗ chromaticity coordinate for color and increased ash content and L^∗. The physicochemical changes in the grain and wheat flour were proportional to the amount of DE applied.     

The Impacts of Carbon Sequestration on Oil Production Projects Decision-Making： A Real Option Valuation Approach

A traditional real option model is applied to a simulation of an oil production project. This analysis includes a carbon sequestration structure cost and possible revenues from carbon credit markets. The evaluation focuses on the determination of an optimal timing for the investment in different scenarios, regarding the volatility of the uncertain variable, oil prices. Historical prices data from different moments are used to estimate different prices uncertainty scenarios and its impacts on the decision making on building a carbon sequestration structure. The results are compared between a real option model to the ones obtained using the traditional net present value evaluation. Trigger point of investments are defined for different scenarios with and without carbon sequestration. There is also an analysis of the effects on decision-making in different scenarios for carbon market prices. It is perceived an important difference in the decision making considering the different methods of economic analysis. The real option model is a fundamental valuation tool in periods of high price volatility and higher sunk costs added to a project such as the carbon sequestration structure. Greenhouse gas projects demand high oil prices, positive market trend expectation and volatility.     

Video microscopy as an alternative method for somatic cell count in milk

This paper presents an alternative method to estimate somatic cell count (SCC) in cows' milk. SCC is an important indicator in the detection of inflammatory reactions within the udder in cows and Direct Optical Microscopy (DOM) is the present reference method for SCC but, owing to its dependence on human operators, it is extremely costly, time-consuming and potentially subjective. The industrial method of choice is Epifluorescence (EF), which has the potential for impressive throughput and acceptable precision, but requires huge inversions and handling of highly toxic reactives and waste. In this paper, an advantageous method that involves application of a low-cost Video Microscopy (VM) system is analysed and discussed, including a comparison between DOM and VM, and an example of application of both methods to evaluate EF counts. We conclude that VM is sufficiently precise and very cheap to implement and operate.     

Analysis of a sequential production of electricity,ice and drying of agricultural products by cascading geothermal energy

In this paper, it is presented an analysis for the sequential production of electricity, ice and drying of agricultural products, by the concept of cascade for medium and low temperature geothermal energy. To carry out the analysis, a set of practical assumptions for the integration of technologies operated by cascade method for geothermal energy were defined. The geothermal cascade is composed of three thermal levels, each one operating under different temperatures in decreasing form. Additionally, the thermal cascade is composed at the first level by an Organic Rankine Cycle (ORC) for electricity production. In the second thermal level, by an absorption refrigeration cycle for ice production, and in the third level includes a dehydrator for drying of agricultural products. The agricultural products considered for dehydration are: avocado, green chile and tomato. Once the main assumptions were set, five integration alternatives and five different modes of operation of the system were proposed. The alternatives have different features for the activation of the first thermal level of the cascade, different nominal capacities of electricity production, cold, and quantity of product to be dehydrated. Subsequently, a technical-economic analysis is carried out to obtain the performance and energy characteristics of the different thermal levels of the cascade, different modes of operation, carbon dioxide emissions, cost estimations and indicators of economic viability. The results indicate that the dehydration process improves drastically the economic profits of all alternatives, especially for dehydration of tomato, achieving simple payback periods of around one year, overall energy efficiency of up to 17.84% and greenhouse emissions reduction of 537.7 tonnes of CO₂ per year. Concerning the modes of operation, it was determined that the one based on only-electricity production is not desirable due to the worst energy and economic performance.     

Chemical changes in the volatile fractions of Brazilian honeys during storage under tropical conditions

The chemical transformations of the volatile fractions of two different Brazilian honeys (cashew and marmeleiro) were monitored during storage under tropical conditions. Five systems, namely: 1 – fresh samples; 2 and 3 – samples heated for 3 and 6 months at 35 – 40 °C; 4 and 5 – samples kept under similar conditions to systems 2 and 3, but containing sodium metabisulphite, were tested. The transformations noted in the volatile fractions of these honeys could be mainly associated to acid or enzymatic hydrolysis of glycosides, volatilization, oxidation or esterification processes. The formation of furan derivatives, linalool derivatives and esters appears to be quite affected by the sodium metabisulphite. The concentrations of most powerful odorants increased during the storage (e.g.: benzenemethanol and isovaleric acid) or remained unchangeable (e.g.: vanillin, furfuryl mercaptan, 2-methoxyphenol).