On the Bound States in a Non-linear Quantum Field Theory of a Spinor Field with Higher Derivatives

We consider a model of quantum field theory with higher derivatives for a spinor field with quartic selfinteraction. With the help of the Bethe-Salpeter equation we study the problem of the two particle bound states in the "chain" approximation. The existence of a scalar bound state is established.Comment: 14 pages, no figures, LaTe

Analysis of Short-term Steel Corrosion Products Formed in Tropical Marine Environments of Panama

The phases and compositions of the corrosion products of a mild steel (A-36) and two weathering steels (A-588 and COR 420) formed after 3 months exposure to the tropical marine atmosphere of Panama were examined using FTIR and Mössbauer spectroscopy. The results show that amorphous or crystallized iron oxyhydroxides goethite α-FeOOH and lepidocrocite γ-FeOOH are early corrosion products. Maghemite γ-Fe2O3 and magnetite Fe3O4 have also been identified and found to be prominent components for steels exposed to the most aggressive conditions. The formation of akaganeite β-FeOOH was observed when chlorides were occluded within the rust. FTIR showed the presence of hematite α-Fe2O3 in one sample.The phases and compositions of the corrosion products of a mild steel (A-36) and two weathering steels (A-588 and COR 420) formed after 3 months exposure to the tropical marine atmosphere of Panama were examined using FTIR and Mössbauer spectroscopy. The results show that amorphous or crystallized iron oxyhydroxides goethite α-FeOOH and lepidocrocite γ-FeOOH are early corrosion products. Maghemite γ-Fe2O3 and magnetite Fe3O4 have also been identified and found to be prominent components for steels exposed to the most aggressive conditions. The formation of akaganeite β-FeOOH was observed when chlorides were occluded within the rust. FTIR showed the presence of hematite α-Fe2O3 in one sample

Personal values and entrepreneurial intention: an empirical study

From a cognitive perspective, the study of the psychosocial characteristics of new entrepreneurs continues to attract more and more attention among researchers. Nevertheless, the identification of individual values and the effect they exert on the decision to become an entrepreneur is clearly an under-researched area of study. Social psychology has shown that values may cause behaviour by promoting positive attitudes and action-planning. This study examines the value-intention link in entrepreneurship on a sample of 1467 Spanish university students. Schwartz’s Portrait Value Questionnaire (PVQ) is used to measure values. Results confirm the positive effects of openness to change and self-enhancement values on the entrepreneurial intentio

Review of some classical gravitational superenergy tensors using computational techniques

We use computational algorithms recently developed by us to study completely four index divergence free quadratic in Riemann tensor polynomials in GR. Some results are new and some other reproduce and/or correct known ones. The algorithms are part of a Mathematica package called Tools of Tensor Calculus (TTC)[web address: http://baldufa.upc.es/ttc

ESTUDIO DEL EFECTO ESTACIONAL SOBRE LA CORROSIÓN ATMOSFÉRICA INICIAL DE ACEROS DE BAJO CARBONO EN LA CIUDAD DE PANAMÁ

In this work, the atmospheric corrosivity of a low carbon steel A-36 is assessed after exposure to the environment of Panama City (Main Campus of the University of Panama). Seasonal effect was determined by exposing, both, during dry and rainy season. The levels of contaminants (Cl- y SO2) observed during this study were lower than those obtained in previous studies (MICAT-Panama). The extrapolated corrosion values were 13 m/year, for steels that were exposed beginning in the dry and rainy season, respectively. Corrosivity was classified as C2 according to ISO. By using Mössbauer spectroscopy and Fourier transform Infrared analysis it was determined that the nature of the initial corrosion products was season dependent. Rust obtained from steels with exposure started during dry season was initially composed of amorphous and hydrated ferric oxyhydroxides; whereas during the rainy season it was a mixture of lepidocrocite (-FeOOH) and goethite (-FeOOH). After short periods, lepidocrocite and goethite constituted both types of samples. The amount of goehtite increased with time of exposition. No spinel phase could be identified.     En este trabajo se presentan los resultados de la evaluación de la corrosividad atmosférica sobre un acero de bajo carbono A-36, expuesto a la intemperie en la ciudad de Panamá (Campus Central de la Universidad de Panamá). Se determinó el efecto estacional de la exposición tanto en la época seca como en la época lluviosa. Los niveles de deposición de contaminantes (Cl-y SO2) observados durante el periodo de estudio, febrero 2002-febrero 2003, fueron menores que los observados en estudios previos (MICAT-Panamá). Las velocidades de corrosión en este estudio fueron menores a las obtenidas en el MICAT-Panamá. El valor extrapolado de la velocidad de corrosión fue de 13 m/año y 19m/año, para aceros cuyo inicio de exposición fue en la época seca y en la época lluviosa, respectivamente. La clasificación ISO de corrosividad fue C2, baja corrosividad. Mediante espectroscopia Mössbauer y el análisis infrarrojo de transformada de Fourier se determinó que la naturaleza de los productos iniciales de corrosión dependía de la época del año. La herrumbre obtenida en aceros con exposición iniciada en época seca está constituida inicialmente por oxihidróxidos férricos amorfos e hidratados; mientras que en la época lluviosa la herrumbre es una mezcla de lepidocrocita (-FeOOH) y goethita (-FeOOH). En periodos cortos, ambos tipos de muestras están formados por lepidocrocita y goethita. Las cantidades de goethita crecen con el tiempo de exposición. No se obtuvo fases de espinela

Estudio del efecto estacional sobre la corrosión atmosférica inicial de aceros de bajo carbono en la ciudad de Panamá

En este trabajo se presentan los resultados de la evaluación de la corrosividad atmosférica sobre un acero de bajo carbono A-36, expuesto a la intemperie en la ciudad de Panamá (Campus Central de la Universidad de Panamá). Se determinó el efecto estacional de la exposición tanto en la época seca como en la época lluviosa. Los niveles de deposición de contaminantes (Cly SO2) observados durante el periodo de estudio, febrero 2002-febrero 2003, fueron menores que los observados en estudios previos (MICAT-Panamá). Las velocidades de corrosión en este estudio fueron menores a las obtenidas en el MICAT-Panamá. El valor extrapolado de la velocidad de corrosión fue de 13 m/año y 19m/año, para aceros cuyo inicio de exposición fue en la época seca y en la época lluviosa, respectivamente. La clasificación ISO de corrosividad fue C2, baja corrosividad. Mediante espectroscopia Mössbauer y el análisis infrarrojo de transformada de Fourier se determinó que la naturaleza de los productos iniciales de corrosión dependía de la época del año. La herrumbre obtenida en aceros con exposición iniciada en época seca está constituida inicialmente por oxihidróxidos férricos amorfos e hidratados; mientras que en la época lluviosa la herrumbre es una mezcla de lepidocrocita (-FeOOH) y goethita (-FeOOH). En periodos cortos, ambos tipos de muestras están formados por lepidocrocita y goethita. Las cantidades de goethita crecen con el tiempo de exposición. No se obtuvo fases de espinel

Functional movement screen differences between male and female young judokas athletes

Background and Study Aim: The Functional Movement Screen (FMS) test has been used in different sports to identify the alterations and asymmetries in the basic movement patterns of the athletes, although it has not been analysed as widely in children population, and even less in judo. The cognitive objective of this study was knowledge about the basic motor competence and the probability of injury in children practicing judo through the evaluation of fundamental movement patterns using the FMS test, and to establish a comparison between genders. Material and Methods: Thirty young judokas (16 girls and 14 boys) participated in the study. The performance of each participant was digitally recorded by two cameras, one in each plane (front and sagittal), and was later analysed jointly by two evaluators who are experts in the use of FMS. Results: The girls obtained higher scores on the sum of the seven tests, compared to boys (16.00 ±1.79 vs. 13.57 ±2.59; p = 0.005). In particular, girls scored significantly better than boys in the deep squat, the rotary stability and the active straight leg raise tasks (p<0.05). The boys scored statistically significantly higher than girls in the trunk stability push up task (p<0.05). Conclusions: The girls scored higher on most tasks, indicating better fundamental movement patterns. In addition, most girls scored above 14 points, while most boys scored at or below 14 points, which may indicate decreased motor competence and increased risk of injury in boys

Phylogenetic analyses and toxigenic profiles of Fusarium equiseti and Fusarium acuminatum isolated from cereals from Southern Europe

Fusarium equiseti and Fusarium acuminatum are toxigenic species that contaminate cereal crops from diverse climatic regions. They are common in Spanish cereals. The information available on their phylogenetics and toxigenic profiles is, however, insufficient to assist risk evaluation. In this work, phylogenetic analyses were performed using partial sequences of the translation elongation factor gene (EF-1a) of F. equiseti and F. acuminatum strains isolated from barley and wheat from Spain and other countries. The Northern and Southern European F. equiseti strains largely separated into two phylogenetically distinct clusters. This suggests the existence of two distinct populations within this species, explaining its presence in these regions of markedly different climate. Production of type A and B trichothecenes by the Spanish strains, examined in wheat cultures using a multitoxin analytical method, indicated that F. equiseti could produce deoxynivalenol and nivalenol and other trichothecenes, at concentrations that might represent a significant risk of toxin contamination for Southern European cereals. F. acuminatum showed low intraspecific genetic variability and 58% of the strains could produce deoxynivalenol at low level. Neither species was found to produce T-2 or HT-2 toxins. The present results provide important phylogenetic and toxigenic information essential for the accurate prediction of toxigenic risk

The novel chemokine receptor CXCR7 regulates trans-endothelial migration of cancer cells

<p>Abstract</p> <p>Background</p> <p>Migration of metastatic tumor cells from the bloodstream into lymph nodes is thought to be facilitated by expression of the chemokine receptors CCR7, CXCR4 and, for B cell-derived tumors, CXCR5. Expression of their respective chemokine ligands (CCL19, CCL21, CXCL12 and CXCL13) by endothelial cells inside the lymph nodes facilitates the trans-endothelial migration (TEM) of these cells through high endothelial venules into the lymph node parenchyma. It is known that CXCR7, a second CXCL12 receptor, regulates TEM of CXCR4+CXCR7+ tumor cells towards a CXCL12 source. In this study, we set out to assess the potential stimulation by CXCL12 of tumor cell TEM towards other chemokines and whether CXCR7 might be able to regulate such effects.</p> <p>Methods</p> <p>The human Burkitt's lymphoma cell line NC-37, which expresses CXCR4, CXCR5, CXCR7 and CCR7, was selected as a model system. TEM of these cells through a human HUVEC endothelial cell monolayer was used as the main model system for these studies. Regulation of their TEM behavior by various concentrations of the various cognate chemokines for the above-mentioned receptors, placed in either the source or target wells of modified Boyden chamber migration plates, was assessed by quantifying the number of cells migrated under each experimental condition.</p> <p>Results</p> <p>Exposure of CXCR4⁺CXCR7⁺cancer cells to CXCL12 greatly potentiated their TEM towards the chemokines CCL19 and CXCL13. This CXCL12-potentiated TEM was inhibited by the second CXCR7 chemokine ligand, CXCL11, as well as CXCR7-specific small molecule antagonists and antibodies. In contrast, the CXCR4 antagonist AMD3100 was less effective at inhibiting CXCL12-potentiated TEM. Thus, CXCR7 antagonists may be effective therapeutic agents for blocking CXCL12-mediated migration of CXCR4⁺CXCR7⁺tumor cells into lymph nodes, regardless of whether the cancer cells follow a CXCL12 gradient or whether serum CXCL12 stimulates their migration towards CCR7 and CXCR5 chemokines in the lymph nodes.</p