Analytical solution of the advection–diffusion transport equation using a change-of-variable and integral transform technique

This paper presents a formal exact solution of the linear advection–diffusion transport equation with constant coefficients for both transient and steady-state regimes. A classical mathematical substitution transforms the original advection–diffusion equation into an exclusively diffusive equation. The new diffusive problem is solved analytically using the classic version of Generalized Integral Transform Technique (GITT), resulting in an explicit formal solution. The new solution is shown to converge faster than a hybrid analytical–numerical solution previously obtained by applying the GITT directly to the advection–diffusion transport equation.     

Inhibitory pheromonal activity promoted by sulfur analogs of the sex pheromone of the female processionary mothThaumetopoea pityocampa (Denis and schiff)

New sulfur analogs of the sex pheromone of the female processionary mothThaumetopoea pityocampa have been found to be effective inhibitors of the natural pheromone activity both in EAG bioassays and field tests. The structures of these analogs have been derived from replacement of the oxygen atom(s) of the acetate group by sulfur (compounds 3-5) and the olefinic moiety of the enyne function by the isosteric SCH₂ group (compounds 6 and 7). The synthesis and biological activity of 3-[(Z)-12-pentadecen-10-ynylthio]-1,1,1-trifluoropropan-2-one (8), a closely related structure to the pheromone is also described.     

Fatty acid composition of selected roes from some marine species

Fifteen roes from different marine fish species available in Spain were analyzed in order to determine their fatty acid (FA) composition, especially the eicosapentaenoic acid (20:5n‐3, EPA) and docosahexaenoic acid (22:6n‐3, DHA) contents. Roes from Atlantic bonito (Sarda sarda), European squid (Loligo vulgaris), cuttlefish (Sepia spp.), lumpfish (Cyclopterus lumpus), European hake (Merluccius merluccius), Atlantic salmon (Salmo salar) and gonads of male Atlantic mackerel (Scomber scombrus) reached EPA + DHA amounts higher than 30% of the total FA, and among them, roes from lumpfish, European hake and salmon provide different FA type ratios that could make them adequate as dietary sources of EPA and DHA.     

The vaccinia virus 14-kilodalton (A27L) fusion protein forms a triple coiled-coil structure and interacts with the 21-kilodalton (A17L) virus membrane protein through a C-terminal alpha-helix

The vaccinia virus 14-kDa protein (encoded by the A27L gene) plays an important role in the biology of the virus, acting in virus-to-cell and cell-to-cell fusions. The protein is located on the surface of the intracellular mature virus form and is essential for both the release of extracellular enveloped virus from the cells and virus spread. Sequence analysis predicts the existence of four regions in this protein: a structureless region from amino acids 1 to 28, a helical region from residues 29 to 37, a triple coiled-coil helical region from residues 44 to 72, and a Leu zipper motif at the C terminus. Circular dichroism spectroscopy, analytical ultracentrifugation, and chemical cross-linking studies of the purified wild-type protein and several mutant forms, lacking one or more of the above regions or with point mutations, support the above-described structural division of the 14-kDa protein. The two contiguous cysteine residues at positions 71 and 72 are not responsible for the formation of 14-kDa protein trimers. The location of hydrophobic residues at the a and d positions on a helical wheel and of charged amino acids in adjacent positions, e and g, suggests that the hydrophobic and ionic interactions in the triple coiled-coil helical region are involved in oligomer formation. This conjecture was supported by the construction of a three-helix bundle model and molecular dynamics. Binding assays with purified proteins expressed in Escherichia coli and cytoplasmic extracts from cells infected with a virus that does not produce the 14-kDa protein during infection (VVindA27L) show that the 21-kDa protein (encoded by the A17L gene) is the specific viral binding partner and identify the putative Leu zipper, the predicted third alpha-helix on the C terminus of the 14-kDa protein, as the region involved in protein binding. These findings were confirmed in vivo, following transfection of animal cells with plasmid vectors expressing mutant forms of the 14-kDa protein and infected with VVindA27L. We find the structural organization of 14kDa to be similar to that of other fusion proteins, such as hemagglutinin of influenza virus and gp41 of human immunodeficiency virus, except for the presence of a protein-anchoring domain instead of a transmembrane domain. Based on our observations, we have established a structural model of the 14-kDa protein.     

Structural basis for heterogeneous kinetics: reengineering the hairpin ribozyme

The RNA cleavage reaction catalyzed by the hairpin ribozyme shows biphasic kinetics, and chase experiments show that the slow phase of the reaction results from reversible substrate binding to an inactive conformational isomer. To investigate the structural basis for the heterogeneous kinetics, we have developed an enzymatic RNA modification method that selectively traps substrate bound to the inactive conformer and allows the two forms of the ribozyme-substrate complex to be separated and analyzed by using both physical and kinetic strategies. The inactive form of the complex was trapped by the addition of T4 RNA ligase to a cleavage reaction, resulting in covalent linkage of the 5' end of the substrate to the 3' end of the ribozyme and in selective and quantitative ablation of the slow kinetic phase of the reaction. This result indicates that the inactive form of the ribozyme-substrate complex can adopt a conformation in which helices 2 and 3 are coaxially stacked, whereas the active form does not have access to this conformation, because of a sharp bend at the helical junction that presumably is stabilized by inter-domain tertiary contacts required for catalytic activity. These results were used to improve the activity of the hairpin ribozyme by designing new interfaces between the two domains, one containing a non-nucleotidic orthobenzene linkage and the other replacing the two-way junction with a three-way junction. Each of these modified ribozymes preferentially adopts the active conformation and displays improved catalytic efficiency.     

A boosting approach for corporate failure prediction

Predicting corporate failure is an important management science problem. This is a typical classification question where the objective is to determine which indicators are involved in the failure/success of a corporation. Despite the importance of this problem, until now only classical machine learning tools have been considered to tackle this classification task. The objective of this paper is twofold. On the one hand, we introduce novel discerning measures to rank independent variables in a generic classification task. On the other hand, we apply boosting techniques to improve the accuracy of a classification tree. We apply this methodology to a set of European firms, considering the usual predicting variables such as financial ratios, as well as including novel variables rarely used before in corporate failure prediction, such as firm size, activity and legal structure. We show that our approach decreases the generalization error about thirty percent with respect to the error produced with a classification tree. In addition, the most important ratios deal with profitability and indebtedness, as is usual in failure prediction studies. E. A. Cortés · M. G. Martínez · N. G. Rubio. The authors teach Statistics at the Faculty of Economic and Business Sciences in the University of Castilla-La Mancha. Esteban Alfaro completed his degree in Business in 1999 and got his Ph.D. in Economics in 2005, both in the University of Castilla-La Mancha. His thesis dealt with the application of ensemble classifiers to corporate failure prediction. Matías Gámez got his degree in Mathematics at the University of Granada in 1991 and finished a Master in Applied Statistics a year after. He completed his Ph.D. in Economics at the University of Castilla-La Mancha in 1998 on the application of geo-statistical techniques to the estimation of housing prices. Noelia García got her degree in Economics at the University of Madrid (UAM) in 1996 and completed her Ph.D. in Economics in 2004 on the construction of an intelligent and automated system for property valuation through the combination of neural nets and a geographic information system (GIS). Current research deals with spatial statistics and the combination of classifiers (decision trees and neural nets) for solving heated topics in the Economics.     

Blood cells of the gilthead seabream (Sparus aurata L.): light and electron microscopic studies

The peripheral blood cells of the gilthead seabream (Sparus aurata L.) were studied by light and transmission and scanning electron microscopic methods. Acidophilic erythroblasts and mature erythrocytes, round, oval, and fusiform thrombocytes, neutrophils, acidophils and basophils, lymphocytes, plasma cells, and monocyte-macrophages were characterized. A comparison of our light and electron microscopic results was carried out. The results were discussed with those for other fish species and the main modifications from the common vertebrate haematological pattern observed being considered.     

Rheological characterization of egg yolk processed by spray-drying and lipid-cholesterol extraction with carbon dioxide

The present work studies the rheological properties of avian egg yolks processed by spray-drying and by lipid-cholesterol extraction with CO₂ under near-critical conditions. The results have been compared with those obtained from native egg products in order to analyze the effect of processing on the microstructure and rheological properties of egg yolks. The rheological study included linear viscoelasticity measurements by means of dynamic oscillatory shear and creep tests, which provided information about the unperturbed structure of the material, as well as steady-state flow measurements. The thermal denaturation of proteins, which was produced during the spray-drying of egg yolk, was responsible for the dramatic change from fluid to gel-like behavior. The thermal denaturation of proteins promotes the formation of a gel-like network, which may be attributed to exposure of internal hydrophobic groups that favor protein aggregation. Lipid (and cholesterol) extraction from yolk increased the viscoelasticity functions and flow properties due to the increased protein concentration.