Regulation of Phosphatidic Acid Levels in <Emphasis Type="Italic">Trypanosoma cruzi</Emphasis>

Lipid kinases and phosphatases play essential roles in signal transduction processes involved in cytoskeletal rearrangement, membrane trafficking, and cellular differentiation. Phosphatidic acid (PtdOH) is an important mediator lipid in eukaryotic cells, but little is known regarding its regulation in the parasite Trypanosoma cruzi, an agent of Chagas disease. In order to clarify the relationship between PtdOH metabolism and developmental stages of T. cruzi, epimastigotes in culture were subjected to hyperosmotic stress (~1,000 mOsm/L), mimicking the environment in the rectum of vector triatomine bugs. These experimental conditions resulted in differentiation to an intermediate form between epimastigotes and trypomastigotes. Morphological changes of epimastigotes were correlated with an increase in PtdOH mass accomplished by increased enzyme activity of diacylglycerol kinase (DAGK, E.C. 2.7.1.107) and concomitant decreased activity of phosphatidate phosphatases type 1 and type 2 (PAP1, PAP2, E.C. 3.1.3.4). Our results indicate progressive increases of PtdOH levels during the differentiation process, and suggest that the regulation of PtdOH metabolism is an important mechanism in the transition from T. cruzi epimastigote to intermediate form.     

Determination of sterigmatocystin in cheese by high-performance liquid chromatography-tandem mass spectrometry

Different cheese samples produced in Latvia (eight) and Belgium (13) were analysed for their sterigmatocystin (STC) content. Only two (9.5%) of the samples were positive for STC with concentration levels of 1.23 and 0.52 µg kg^?1, respectively. Five (24%) samples contained STC above the limit of detection (0.03 µg kg^?1) but below the limit of quantification (0.1 µg kg^?1), A sensitive liquid chromatography-electrospray positive ionisation-tandem mass spectrometry (LC-MS/MS) method, which was previously developed for the analysis of STC in grains, was modified and applied to the analysis of STC in cheese. This method involved sample extraction with acetonitrile–water (90 : 10, v/v), defatting with n-hexane, solid-phase extraction, separation on a reversed-phase C₁₈ column, and STC detection by LC-MS/MS.     

EFFECTS OF HEAT GENERATION-ABSORPTION AND CHEMICAL REACTION ON MAGNETOHYDRODYNAMIC FLOW IN A PERMEABLE MOVING PLATE: NETWORK NUMERICAL STUDY

This study addresses the transient heat and mass transfer problem by laminar flow of a Newtonian, viscous electrically conducting, and heat generating/absorbing fluid on a continuously moving permeable surface. It was carried out with the well-known network simulation method. The effect of the parameters involved in the process were analyzed, so the influence of the parameters is represented graphically for several cases. The dimensionless parameters used in this study are: chemical reaction parameter, Prandtl number, Grashof number, absorption coefficient or heat generation, Schmidt number, and Hartmann number. The results presented are important because of the relevance of the conclusions for the steady and transient cases. In the study, the flow was considered laminar and two-dimensional. In addition, the transverse magnetic field is uniform and viscous dissipation effects, Hall effect, and Joule heating are omitted.     

Improving retrieval accuracy of Hierarchical Cellular Trees for generic metric spaces

Metric Access Methods (MAMs) are indexing techniques which allow working in generic metric spaces. Therefore, MAMs are specially useful for Content-Based Image Retrieval systems based on features which use non L _p norms as similarity measures. MAMs naturally allow the design of image browsers due to their inherent hierarchical structure. The Hierarchical Cellular Tree (HCT), a MAM-based indexing technique, provides the starting point of our work. In this paper, we describe some limitations detected in the original formulation of the HCT and propose some modifications to both the index building and the search algorithm. First, the covering radius, which is defined as the distance from the representative to the furthest element in a node, may not cover all the elements belonging to the node’s subtree. Therefore, we propose to redefine the covering radius as the distance from the representative to the furthest element in the node’s subtree. This new definition is essential to guarantee a correct construction of the HCT. Second, the proposed Progressive Query retrieval scheme can be redesigned to perform the nearest neighbor operation in a more efficient way. We propose a new retrieval scheme which takes advantage of the benefits of the search algorithm used in the index building. Furthermore, while the evaluation of the HCT in the original work was only subjective, we propose an objective evaluation based on two aspects which are crucial in any approximate search algorithm: the retrieval time and the retrieval accuracy. Finally, we illustrate the usefulness of the proposal by presenting some actual applications.     

Comparative study of three yttrium organometallic compounds for the stabilization of the cubic phase in YSZ deposited by PE-CVD

In this work, the efficiencies of three organometallic yttrium precursors used to produce YSZ coatings by plasma-enhanced chemical vapor deposition were studied. Yttrium (III) acetylacetonate, Y (acac)₃, yttrium (III) hexafluoroacetylacetonate, Y (acacF₆)₃, and yttrium (III) tris(2,2,6,6-tetramethyl-3,5-heptanedionate), Y (tmhd)₃, were used to stabilize the cubic phase in zirconia deposited at temperatures from 500 to 800 °C. Our results showed that at temperatures between 500 and 600 °C, Y (tmhd)₃ appeared to be the most efficient dopant as it introduced the highest concentration of yttria (1–2.7 mol%) with only 6.4–5.6 at.% carbon. However, at 700 and 800 °C, Y (acac)₃ introduced twice as much yttria (8–15 mol%) as Y (tmhd)₃ with almost the same amount of carbon (5.4–3 at.%). Conversely, Y (acacF₆)₃ was the least efficient as it maintained a low concentration of yttria of around 0.7–1.8 mol% with 3.6–8.2 at.% carbon for all the deposition temperatures. Among these precursors, only Y (acac)₃ surpassed 8 mol% yttria and achieved a fully stabilized cubic phase at 800 °C, with the remaining samples stabilizing only the tetragonal phase. The tetragonal phase was stabilized due to the formation of crystallites of around 10 nm. The observed difference in the efficiency of the three precursors was correlated to important differences in their decomposition behavior as observed by mass spectrometry and thermogravimetry/differential scanning calorimetry.     

Chemical,thermal and structural properties of alkaline-cooked (nixtamalised) chickpea (Cicer arietinum) flours

The present study examined how the alkaline cooking process affects the chemical, thermal and structural properties of the chickpea, evaluating different lime concentrations. Cooking was carried out at 94 °C, with two times of water for 15 min with five different lime concentrations. Regarding chemical composition, a decrease in protein and fat was observed: from 23.64% to a range of 18.26–19.93% for protein and from 8.20% to a range of 6.05–7.74% for fat. However, an increase was observed for ash and mineral content. The same pattern was observed for potassium. Raw chickpea did not present endotherm retrogradation, but a higher endotherm retrogradation was presented in chickpea cooked without lime, denoting that nixtamalisation decreased retrogradation. Additionally, V-amylose relative crystallinity increased with concentration of lime. Protein digestibility increases by β-sheet dismissing structure. Finally, it was observed that steeping time plays a key role in the nixtamalisation process.     

Problems of operation and main reasons for failure of membranes in tertiary treatment systems.

This paper presents the results of the long-term operation and monitoring of membrane fouling at several full-scale MF/RO water recycling facilities operated by Agbar in Spain. It was demonstrated that membranes give very reliable treatment enabling the production of high-grade recycled water, well disinfected and with the removal of all priority substances. The high organic and salt concentrations of raw wastewater combined to extremely high variations justified the implementation of sand filtration to protect MF/RO membranes. Membrane autopsy was used to better understand the predominant fouling mechanisms and optimise down-stream operation and membrane cleaning strategy. The main membrane pathologies are described with recommendation of an adequate cleaning strategy.     

Optimized PCR labeling in mutational and microsatellite analysis

The behavior of the dielectric properties of gelatin in the frequency range from 10(3) Hz to 10(7) Hz was investigated and compared with that of the globule protein, bovine serum albumin (BSA), desalted gelatin and BSA being used. Dielectric relaxation was observed for both the gelatin and BSA solutions. The relaxation data were fitted well by the Cole-Cole equation; the Cole-Cole parameter (beta) and the relaxation time (tau) were obtained. For the BSA solutions, tau was proportional to the solution viscosity (eta) at 40 degrees C and 25 degrees C, and the values of beta at 40 degrees C were similar to those at 25 degrees C. For gelatin solution, tau was proportional to eta at 40 degrees C, but was not proportional to eta at 25 degrees C. In addition, the values of beta at 25 degrees C were smaller than those at 40 degrees C. These results indicate that the rotation of gelatin and/or polarization of submolecular groups in the coil state greatly contributed to the dielectric relaxation at 40 degrees C; on the other hand, the formation of cross-linking junctions consisting of helix structures would have affected the dielectric relaxation at 25 degrees C.     

Alterations of microsatellites in neurofibromas of von Recklinghausen's disease

von Recklinghausen's disease, or type I neurofibromatosis, a common familial tumor syndrome, is characterized by the occurrence of multiple benign neoplasms of nerve sheath cells. The disease is caused by germ-line mutations of the NF1 gene, which encodes a member of the GTPase-activating superfamily of Ras regulatory proteins. We analyzed 5 dinucleotide repeat loci in DNAs from neurofibromas and matched normal skin from 16 NF1 patients. Eight cases (50%) manifested microsatellite alterations. Expansions or compressions of dinucleotide repeats were observed at one locus in four cases and at two loci in one case. Banding patterns compatible with the loss of a microsatellite allele were observed in four cases, including one that also presented microsatellite instability. The surprisingly high frequency of microsatellite alterations suggests that the NF1 gene or another gene(s) contributing to the pathogenesis of neurofibromas might be directly or indirectly implicated in the control of genomic integrity.     

Causal delivery protocols in real-time systems: A generic model

The objective of this paper is to introduce a model for causal delivery protocols in real-time systems. We start by showing that temporal order properties of real-time protocols are independent of whether they are timer-driven or clock-driven, being instead related to their degree of synchronism, that we call steadiness. Then, we derive a set of correctness conditions for such protocols to secure causal delivery order. To achieve this objective, we use an extension of Lamport's model of time-stamp based order. We show that both timer- and clock-driven protocols have order correctness limits dictated by the environment and the target applications, and define those limits, through a set of working formulas. We show that in extremely adverse cases, timer-driven protocols will perform as well as clock-driven ones, due to the restrictions imposed on the operation of the latter, which is perhaps surprising. These results open the door to exploring new forms of communication in time-critical systems, for example, supporting clock-and time-driven communication, and event-and time-triggered operation. We expect that the results of this paper will give insight to that problem, and will be useful in real-life systems, such as distributed computer control.