Cercaria chaetotaxy of 2 Venezuelan strains of Schistosoma mansoni

By means of the silver impregnation of two lots of Schistosoma mansoni cercariae belonging to the strains: JR (32 cercariae) and C5 (45 cercariae), the number and pattern of disposition of the argentophillic papillae were determined with the following results: Average number of total dorsal papillae: 12.1 (JR strain) and 12.0 (C5 strain); the variation coefficients in this surface were less than 4% (JR strain) and bigger in JR than C5 strain. Average number of total ventral papillae: 12.15 (JR), 11.97 (C5); maximum value of the variation coefficient: 6.4% (JR), higher in JR than C5 strain. When the ventral surface was classified in four quadrants, the average number of papillae by quadrant was: quadrant A: 1.15 (JR) and 1.06 (C5): B: 1.06 (JR) and 1 (C5); C: 4.97 (JR) and 4.96 (C5); D: 5.03 (JR) and 4.98 (C5). The variation coefficients were higher in the A and B ventral quadrants, reaching maximum values of 31.9%, and 61.0% for the posterior quadrants C and D. When the ventral surface was divided in three equal parts for determining the position of the most variable papillae of this area, the greatest value of the variation coefficients obtained were for the 2nd thirds of the cercariae: 89.8% and 76.8% for C5 strain and 43.5% and 56.8% for JR strain. In relation to the total lateral papillae, the average numbers were: 17.0 (JR) and 16.6 (C5), with a maximum value of variation coefficient of (8.1% (C5). The average total number of papillae of the tail were: 25.6 (JR) and 26.1 (C5) for the ventral surface and 20.72 (JR) and 21.33 (C5) for the dorsal papillae. The comparison between the percents of the cercariae of two S. mansoni strains with more than 1 papillae on the anterior ventral quadrants A or B (94% JR and 34% C5), resulted with significant differences (P < 0.05).     

Catalytic Performance of Ce1−x Ni x O2 Catalysts for Propane Oxidative Steam Reforming

The model, proposed by Peskov et al. (Catal Today 105:223, 2005) to describe kinetic oscillations observed in the N₂O + H₂ reaction on Ir(110), is used to illustrate the effect of periodic perturbation of the reactant pressures on oscillations. The attention is focused on the conversion of natural period-1 oscillations to period-1 oscillations with the imposed frequency. For this conversion, simultaneous perturbation of both reactant pressures is found to be much more efficient compared to perturbation of one of the pressures.     

Stencil Adaptation Properties of a WENO Scheme in Direct Numerical Simulations of Compressible Turbulence

Weighted essentially non-oscillatory (WENO) methods can simultaneously provide the high order of accuracy, high bandwidth-resolving efficiency, and shock-capturing capability required for the detailed simulation of compressible turbulence. However, rigorous analysis of the actual versus theoretical error properties of these non-linear numerical methods is difficult. We use a bandwidth-optimized WENO scheme to conduct direct numerical simulations of two- and three-dimensional decaying isotropic turbulence, and we evaluate the performance of quantitative indicators of local WENO adaptation behavior within the resulting flow fields. One aspect of this assessment is the demarcation of shock-containing and smooth regions where the WENO method should, respectively, engage its adaptation mechanism and revert to its linear optimal stencil. Our results show that these indicators, when synthesized properly, can provide valuable quantitative information suitable for statistical characterization.     

Characterization of the morphological modification induced by long term operations on phosphoric acid fuel cell (PAFC) electrodes

The modification of the morphological and adhesive binding of PAFC electrodes has been studied by electron spectroscopy and electron microscopy with regard to their endurance and preparative treatments. The corrosion of the electrodes has been found to dramatically affect the electrical and adhesive contact between PTFE (polytetrafluoroethylene) and active carbon. This has been detected in X-ray photoelectron spectroscopy (XPS) by the charging shift seen for F 1 s due to the loss in electronic contact between these components. In addition, the adhesive character of the contact between the SiC matrix and the gas diffusion electrodes has been revealed by the XPS spectral characteristics. Here a major difference between the anode and the cathode has been observed with the cathode having a greater deadhesion. Extensive physical characterization by pore volume and size distribution, wetting, and weight loss has been performed. These results have been correlated with the XPS results to give a complete model of the deterioration of this technologically important system. A possible explanation for the observed loss of PTFE from the surface of the cathode based on an electrostatic rejection model of the delaminated PTFE particles is also suggested.     

Some aspects of stereoregulation in the stereospecific polymerization of vinyl monomers

Stereoregularity in vinyl polymers, although theoretically foreseen since 1929, became one of the main topics in polymer research after the discovery of the stereospecific polymerization of α-olefins in 1954. The theoretical and practical significance of a thorough knowledge of stereoregulation became immediately evident; however, in spite of extensive efforts made by different industrial and academic research groups, the mechanism of stereoregulation is far from being understood and the control of stereoregulation, particularly in Ziegler-Natta polymerization, is still carried out on a purely empirical basis. In this review, after a short survey of the methods used to determine polymer stereoregularity and a discussion of the information which can be obtained from examination of the microtacticity of the polymer chains, some of the factors which can influence the stereoregulation in radical, ionic and Ziegler-Natta polymerization will be considered. For the last type of polymerization, in which the nature of the catalyst seems to have an overwhelming importance, some analogies with the transition metal catalysed asymmetric reactions will be discussed. Finally, an attempt will be made to identify the main difficulties in further improving our knowledge of the control of stereoregulation.     

VideoAcM: a transitive and temporal access control mechanism for collaborative video database production applications

Access control models play an important role in database management systems. In general, there are three basic access control models: Discretionary Access Control (DAC), Mandatory Access Control (MAC), and Non-Discretionary Access Control (NAC). Currently, the majority of commercial DBMSs provide only DAC, and some temporal access control models have been derived based on either DAC or NAC. In the context of video database applications, since the structure of video data is complex in nature, it requires a specific and tailor-made access control mechanism which should include MAC as well as DAC and NAC. However, only few efforts have been put on access control models for video database systems. In this paper, a transitive and temporal access control mechanism for collaborative video database production applications has been proposed, which subsumes the properties of DAC, MAC, and NAC. Moreover, our proposed mechanism is integrated with the intellectual property concerns by constructing an access control hierarchy of video data with authorization rules. In particular, our mechanism can derive novel authorization rules not only on conventional client-data access control, but also on data–data access control. Besides video data, the proposed model is applicable to other data types which exhibit a hierarchical data structure.     

Localized iterative generalized multipole technique for largetwo-dimensional scattering problems

We propose a novel and efficient solution for the generalized multipole technique (GMT): the localized iterative generalized multipole technique (LIGMT). In LIGMT, an analytic constraint is imposed on the power radiated by the set of multipole sources sharing the same origin, rendering it minimum over a given angular sector. In this way, the power radiated by each set of multipoles is confined to a different section of the scatterer surface. It follows that each set of multipole coefficients can be solved step by step via an iterative process, which circumvents the need to solve the large and full matrix equation. This implies a significant reduction of the computational and storage cost, enhancing the scope of application of the GMT method to larger problems     

Investigation on the volatile oil of Makó onions

The authors have developed a method for determining the volatile oil content of onions. Using this method they found in the Hungarian Makó onions 0.019—0.031 % volatile oil, depending on storage. The composition of onion oil was studied by GC; GC-MS and TLC methods. GC-MS revealed 20 volatile sulphur compounds identified as 10 trisulphides, 6 disulphides, 3 tetrasulphides, and 1 thiophene derivative as well as one unsaturated aldehyde. Three of these: ethyl cis-1-propenyl trisulphide, ethyl trans-1-propenyl trisulphide, and butyl methyl trisulphide were described for the first time in onions. Carbonyl compounds were studied in the form of derivatives obtained with 2,4-dinitrophenyl hydrazine. On the basis of Rf-values and by addition, propanal, butanal, pentanal and hexanal were identified in the aldehyde fraction, while in the dicarbonyl fraction — beside an unknown compound — glyoxal and methyl glyoxal were identified. The presence of these two compounds in onion oil has been reported for the first time.