Droplet-shaped waves: Causal finite-support analogs of X-shaped waves

A model of steady-state X-shaped wave generation by a superluminal (supersonic) pointlike source infinitely moving along a straight line is extended to a more realistic causal scenario of a source pulse launched at time zero and propagating rectilinearly at constant superluminal speed. In the case of infinitely short (delta) pulse, the new model yields an analytical solution, corresponding to the propagation-invariant X-shaped wave clipped by a droplet-shaped support, which perpetually expands along the propagation and transversal directions, thus tending the droplet-shaped wave to the X-shaped one.Comment: 14 pages, 6 figure

Harnack inequality and regularity for degenerate quasilinear elliptic equations

We prove Harnack inequality and local regularity results for weak solutions of a quasilinear degenerate equation in divergence form under natural growth conditions. The degeneracy is given by a suitable power of a strong $A_\infty$ weight. Regularity results are achieved under minimal assumptions on the coefficients and, as an application, we prove $C^{1,\alpha}$ local estimates for solutions of a degenerate equation in non divergence form

An Integrated Model of Safer Sex Practices among African-American Gay and Bisexual Men

Models of safer sex enable researchers to identify specific constructs that can be used to promote health behavior and are more effective than interventions without a theoretical base. This study tested basic and modified forms of the Theory of Reasoned Action and Information Motivation Behavioral Skills models among 151 African American gay/bisexual men. Gay socialization was added to an integrated model to see if this minority-specific contextual variable would improve the model. Self-efficacy was tested as an independent variable and a mediating variable. The results suggest that an integrated model of safer sex practices should include benefits/barriers to condom use, social norm perceptions, sexual assertiveness, and self-efficacy (as a mediating variable). Gay socialization did not improve the model statistically but may influence safer sex behavior conceptually and pragmatically

FePO(4)NPs Are an Efficient Nutritional Source for Plants: Combination of Nano-Material Properties and Metabolic Responses to Nutritional Deficiencies

Phosphorous and iron are a macro- and micronutrient, respectively, whose low bioavailability can negatively affect crop productivity. There is ample evidence that the use of conventional P and Fe fertilizers has several environmental and economical disadvantages, but even though great expectations surround nanotechnology and its applications in the field of plant nutrition, little is known about the mechanisms underlying the uptake and use of these sub-micron particles (nanoparticles, NPs) by crop species. This work shows that cucumber and maize plants both use the nutrients borne by FePO(4)NPs more efficiently than those supplied as bulk. However, morpho-physiological parameters and nutrient content analyses reveal that while cucumber plants (aStrategy Ispecies with regard to Fe acquisition) mainly use these NPs as a source of P, maize (aStrategy IIspecies) uses them preferentially for Fe. TEM analyses of cucumber root specimens revealed no cell internalization of the NPs. On the other hand, electron-dense nanometric structures were evident in proximity of the root epidermal cell walls of the NP-treated plants, which after ESEM/EDAX analyses can be reasonably identified as iron-oxyhydroxide. It appears that the nutritional interaction between roots and NPs is strongly influenced by species-specific metabolic responses

Testing the Health Belief Model among African-American Gay/Bisexual Men with Self-Efficacy and Minority-Specific Contextual Variables

This study used structural equation modeling to test variations of the Health Belief Model in predicting safer sex intentions among 151 African-American gay/bisexual men. Acculturation and gay socialization were included to see if minority-specific contextual variables improved the model fit. Perceived severity, perceived vulnerability, and cues to action did not improve the model. Including self-efficacy as a mediating variable improved the model and overall prediction of safer sex intentions. Although acculturation and gay socialization were not statistically significant additions to the model, there are conceptual and practical reasons why these variables may influence safer sex intentions among African-American gay/bisexual men

Nucleotide-Binding Oligomerization Domain-1 and -2 Play No Role in Controlling Brucella abortus Infection in Mice

Nucleotide-binding oligomerization domain proteins (NODs) are modular cytoplasmic proteins implicated in the recognition of peptidoglycan-derived molecules. Further, several in vivo studies have demonstrated a role for Nod1 and Nod2 in host defense against bacterial pathogens. Here, we demonstrated that macrophages from NOD1-, NOD2-, and Rip2-deficient mice produced lower levels of TNF-α following infection with live Brucella abortus compared to wild-type mice. Similar reduction on cytokine synthesis was not observed for IL-12 and IL-6. However, NOD1, NOD2, and Rip2 knockout mice were no more susceptible to infection with virulent B. abortus than wild-type mice. Additionally, spleen cells from NOD1-, NOD2-, and Rip2-deficient mice showed unaltered production of IFN-γ compared to C57BL/6 mice. Taken together, this study demonstrates that NOD1, NOD2 and Rip2 are dispensable for the control of B. abortus during in vivo infection

Evaluation of 3D image-treatment algorithms applied to optical-sectioning microscopy

La información extraída de especimenes biológicos es inherentemente tridimensional. Los datos tridimensionales (3D) permiten un mejor entendimiento de las estructuras y los eventos biológicos, comparados con sus proyecciones bidimensionales (2D), aunque a veces son más difíciles de manejar. Esto explica porqué actualmente se están investigando y mejorando las técnicas de seccionamiento óptico. El principal objetivo del presente trabajo fue evaluar la relevancia de algoritmos de tratamiento de imágenes, los cuales incluyen métodos de preprocesamiento (tales como promediación de imágenes, corrección de background y normalización de intensidades) y procesamiento (desconvolución de desborroneo y de restauración). Esto se realizó mediante la implementación de un algoritmo de cuantificación basado en el Laplaciano y un detector de puntos brillantes. Los algoritmos se aplicaron a un modelo 3D de adhesión celular en piel, basado en un espécimen comúnmente utilizado por nuestro grupo de investigación. Los resultados indican que ciertos métodos de preprocesamiento son requeridos para mejorar el rendimiento de los algoritmos de procesamiento, mientras que otros no deben ser aplicados para asegurar una adecuada y precisa cuantificación.Information extracted from biological specimens is inherently three-dimensional. Though it is sometimes hard to handle, three-dimensional (3D) data provides greater understanding of biological structures and events than its bidimensional (2D) projections. This explains why optical-sectioning techniques are currently being explored and enhanced. The main objective of the present work was to evaluate the relevance of image-treatment algorithms, which included preprocessing (such as image-averaging, background correction and normalization of intensities) and processing (deblurring and restoration deconvolution) methods. This was done by implementing a quantification algorithm based on the Laplacian and a bright-point detector. Algorithms were applied to a 3D cell-adhesion skin model, based upon a specimen commonly used by our research group. Results indicated that certain preprocessing methods are required to enhance the performance of processing algorithms, while others must not be applied in order to ensure an adequate and precise quantification.IV Workshop de Computación Gráfica, Imágenes y Visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI

A Method for Generation of Bone Marrow-Derived Macrophages from Cryopreserved Mouse Bone Marrow Cells

The broad use of transgenic and gene-targeted mice has established bone marrow-derived macrophages (BMDM) as important mammalian host cells for investigation of the macrophages biology. Over the last decade, extensive research has been done to determine how to freeze and store viable hematopoietic human cells; however, there is no information regarding generation of BMDM from frozen murine bone marrow (BM) cells. Here, we establish a highly efficient protocol to freeze murine BM cells and further generate BMDM. Cryopreserved murine BM cells maintain their potential for BMDM differentiation for more than 6 years. We compared BMDM obtained from fresh and frozen BM cells and found that both are similarly able to trigger the expression of CD80 and CD86 in response to LPS or infection with the intracellular bacteria Legionella pneumophila. Additionally, BMDM obtained from fresh or frozen BM cells equally restrict or support the intracellular multiplication of pathogens such as L. pneumophila and the protozoan parasite Leishmania (L.) amazonensis. Although further investigation are required to support the use of the method for generation of dendritic cells, preliminary experiments indicate that bone marrow-derived dendritic cells can also be generated from cryopreserved BM cells. Overall, the method described and validated herein represents a technical advance as it allows ready and easy generation of BMDM from a stock of frozen BM cells