Dynamic stability of crack fronts: Out-of-plane corrugations

The dynamics and stability of brittle cracks are not yet fully understood. Here we use the Willis-Movchan 3D linear perturbation formalism [J. Mech. Phys. Solids {\bf 45}, 591 (1997)] to study the out-of-plane stability of planar crack fronts in the framework of linear elastic fracture mechanics. We discuss a minimal scenario in which linearly unstable crack front corrugations might emerge above a critical front propagation speed. We calculate this speed as a function of Poisson's ratio and show that corrugations propagate along the crack front at nearly the Rayleigh wave-speed. Finally, we hypothesize about a possible relation between such corrugations and the long-standing problem of crack branching.Comment: 5 pages, 2 figures + supplementary informatio

A fluorescence-activatable reporter of flavivirus NS2B–NS3 protease activity enables live imaging of infection in single cells and viral plaques

The genus Flavivirus in the family Flaviviridae comprises many medically important viruses, such as dengue virus (DENV), Zika virus (ZIKV), and yellow fever virus. The quest for thera- peutic targets to combat flavivirus infections requires a better understanding of the kinetics of virus–host interactions during infections with native viral strains. However, this is precluded by limitations of current cell-based systems for monitoring flavivi- rus infection in living cells. In the present study, we report the construction of fluorescence-activatable sensors to detect the activities of flavivirus NS2B–NS3 serine proteases in living cells. The system consists of GFP-based reporters that become fluo- rescent upon cleavage by recombinant DENV-2/ZIKV proteases in vitro. A version of this sensor containing the flavivirus inter- nal NS3 cleavage site linker reported the highest fluorescence activation in stably transduced mammalian cells upon DENV-2/ ZIKV infection. Moreover, the onset of fluorescence correlated with viral protease activity. A far-red version of this flavivirus sensor had the best signal-to-noise ratio in a fluorescent Dulbec- co’s plaque assay, leading to the construction of a multireporter platform combining the flavivirus sensor with reporter dyes for detection of chromatin condensation and cell death, enabling studies of viral plaque formation with single-cell resolution. Finally, the application of this platform enabled the study of cell-population kinetics of infection and cell death by DENV-2, ZIKV, and yellow fever virus. We anticipate that future studies of viral infection kinetics with this reporter system will enable basic investigations of virus–host interactions and facilitate future applications in antiviral drug research to manage flavivi- rus infections.International Centre for Genetic Engineering and Biotechnology Grant CRP/CRI18-02.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Centro de Investigación en Enfermedades Tropicales (CIET)UCR::Vicerrectoría de Docencia::Salud::Facultad de Microbiologí

Electrocardiographic changes in normal and abnormal canine pregnancy

The aim of this study was to describe the canine electrocardiographic changes in the course of normal and abnormal pregnancy. Twenty-three Brucellosis-negative pregnant bitches were retrospectively classified as normal (n=12) or abnormal (n=11). A control group of non-pregnant dioestrous bitches (n=10) was also included. Normal pregnant females delivered healthy puppies at term while abnormal animals interrupted their pregnancy between days 52-60 (from estimated luteinizing hormone peak) or presented perinatal litter death higher than 60%. All the bitches were electrocardiographically evaluated every 10days from day 0 to day 65 of the oestrous cycle, to parturition or abortion. Percentage heart rate change increased 31.3% from day 40 to 60 in normal gestation while it decreased -1.8% in dioestrous bitches, although it did not change in the abnormal group (p<0.01). In the abnormal pregnant group but not in the others, percentage QRSa change fell to -34% on day 60 (p<0.01). At the same time point, percentage QRSd change was 6.2% vs -4.9% in normal gestations and dioestrous animals, respectively (p<0.05). Corrected QT interval augmented from day 40 onwards up to 9.9% and 4.3% in the normal pregnant and dioestrous groups, respectively, while it remained unchanged in abnormal gestations (p<0.05). It is concluded that during normal canine pregnancy, some electrocardiographic parameters begin changing from day 40 onwards, and that pathological gestations differ from normality from day 30. The use of electrocardiography in canine obstetrics might contribute to identify abnormal outcomes before they become clinically evident.Fil: Blanco, Paula Graciela. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Batista, Pablo Rodrigo. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Re, N. E.. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Mattioli, Guillermo Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Ciencias Básicas. Laboratorio de Nutrición Mineral y Fisiología Reproductiva; ArgentinaFil: Arias, Daniel Osvaldo. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Gobello, María Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Redes neuronales artificiales en conducción de calor multidimensional transitorio

Este artículo ilustra la aplicabilidad de las Redes Neuronales Artificiales en la predicción de latemperatura de algunos fenómenos de conducción de calor multidimensional transitorio. Seplantean dos casos en una dimensión con condición inicial constante y condiciones de frontera,para uno, de Dirichlet y para el otro, convectivas. Con estas mismas condiciones, se abordangeometrías en dos y tres dimensiones y se desarrollan sus soluciones analiticas para obtener lospatrones de entrada y salida utilizados en elposterior entrenamiento, verificación y generalizaciónde las redes neuronales artificiales. Para predecir la temperatura de los casos estudiados a partirde variables espaciales y temporales mediante la inteligencia artificial, Redes NeuronalesArtificiales, se empleó el Perceptrón multicapa con conexiones hacia adelante, función deactivación tangente hiperbólica para los nodos de la(s) capa(s) oculta(s) y lineal para el nodode salida, algoritmo de aprendizaje Levenberg - Marquardt y raíz de la suma de los cuadrados ypreprocesamiento rango como normalizaciones de las variables de entrada y salidarespectivamente. Una vez determinadas las especificaciones se llevaron a cabo las etapas dedesalTollo: entrenamiento, verificación y generalización de las redes de cada caso de conducciónde calor considerado empleando diversas configuraciones con el fin de seleccionar la másadecuada de acuerdo a los criterios: convergencia en el entrenamiento, capacidad degeneralización y simplicidad en su estructura.Neural networks to prediet the multidimensional unsteady-state temperature projile in a solidhave been used; convective and Dirichlet boundmy conditions for the mathematical model wereapplied to salve the model. For computer simulations several neural networks following theMultilayer Perceptron architecture were trained using the Levenberg-Marquardt algorithm. Resultsshowed an excellent agreement between numerical solutions afthe mathematical model and theneural network predictions

Redes neuronales artificiales en conducción de calor multidimensional transitorio

Este artículo ilustra la aplicabilidad de las Redes Neuronales Artificiales en la predicción de latemperatura de algunos fenómenos de conducción de calor multidimensional transitorio. Seplantean dos casos en una dimensión con condición inicial constante y condiciones de frontera,para uno, de Dirichlet y para el otro, convectivas. Con estas mismas condiciones, se abordangeometrías en dos y tres dimensiones y se desarrollan sus soluciones analiticas para obtener lospatrones de entrada y salida utilizados en elposterior entrenamiento, verificación y generalizaciónde las redes neuronales artificiales. Para predecir la temperatura de los casos estudiados a partirde variables espaciales y temporales mediante la inteligencia artificial, Redes NeuronalesArtificiales, se empleó el Perceptrón multicapa con conexiones hacia adelante, función deactivación tangente hiperbólica para los nodos de la(s) capa(s) oculta(s) y lineal para el nodode salida, algoritmo de aprendizaje Levenberg - Marquardt y raíz de la suma de los cuadrados ypreprocesamiento rango como normalizaciones de las variables de entrada y salidarespectivamente. Una vez determinadas las especificaciones se llevaron a cabo las etapas dedesalTollo: entrenamiento, verificación y generalización de las redes de cada caso de conducciónde calor considerado empleando diversas configuraciones con el fin de seleccionar la másadecuada de acuerdo a los criterios: convergencia en el entrenamiento, capacidad degeneralización y simplicidad en su estructura.Neural networks to prediet the multidimensional unsteady-state temperature projile in a solidhave been used; convective and Dirichlet boundmy conditions for the mathematical model wereapplied to salve the model. For computer simulations several neural networks following theMultilayer Perceptron architecture were trained using the Levenberg-Marquardt algorithm. Resultsshowed an excellent agreement between numerical solutions afthe mathematical model and theneural network predictions

Taxonomic distribution of neoplasia among non-domestic felid species under managed care

As evidenced by numerous case reports from zoos, neoplasia in felids is common, but most reports are limited to Panthera species in North America or Europe. In order to obtain a wider epidemiologic understanding of neoplasia distribution, necropsy records at seven facilities (USA, Mexico, Colombia, Peru, and Brazil) were evaluated. In contrast to others, this study population (195 cases, 16 species), included many non-Panthera felids. Overall neoplasia prevalence was 28.2% (55/195). Panthera species had a higher prevalence of neoplasia than non-Panthera species (52.5%; vs. 13.0%). Lions (66.7%), jaguars (55.0%), and tigers (31.3%) had the highest species-specific prevalence of neoplasia. Neoplasms in Panthera species were more frequently malignant than in non-Panthera (86.1% vs. 55.6%). The systems most commonly a_ected were the reproductive, hematolymphoid, and respiratory. The range of management conditions and more varied genetic backgrounds support a robust taxonomic pattern and suggest that the reported propensity for neoplasia in jaguars may have a genetic basis at a taxonomic level higher than species, as lions and tigers also have high prevalence. Given the high prevalence of neoplasia and high likelihood of malignancy, routine medical exams in all nondomestic felids, but Panthera species in particular, should include thorough assessments of any clinical signs of neoplasia

Gilbert Damping in Magnetic Multilayers

We study the enhancement of the ferromagnetic relaxation rate in thin films due to the adjacent normal metal layers. Using linear response theory, we derive the dissipative torque produced by the s-d exchange interaction at the ferromagnet-normal metal interface. For a slow precession, the enhancement of Gilbert damping constant is proportional to the square of the s-d exchange constant times the zero-frequency limit of the frequency derivative of the local dynamic spin susceptibility of the normal metal at the interface. Electron-electron interactions increase the relaxation rate by the Stoner factor squared. We attribute the large anisotropic enhancements of the relaxation rate observed recently in multilayers containing palladium to this mechanism. For free electrons, the present theory compares favorably with recent spin-pumping result of Tserkovnyak et al. [Phys. Rev. Lett. \textbf{88},117601 (2002)].Comment: 1 figure, 5page

Gobernanza y gestión del agua en el Occidente de México: la metrópoli de Guadalajara

La disponibilidad de agua como tal no es el problema más importante en la gestión del agua. La incertidumbre se sitúa en la capacidad para implementar sistemas de control, distribución y acceso al agua de una forma equitativa. Garantizar el acceso de agua potable a toda la población no es un problema financiero sino político, un asunto de prioridad .Ahora disponemos de un vasto conocimiento y herramientas aplicables en el campo de la hidrología, biotecnología e ingeniería del agua, pero nuestro entendimiento sobre procesos socioeconómicos, culturales y políticos involucrados en la gestión del agua, sigue siendo limitado. En este libro, desde diferentes ángulos, se analizan formas de gestión del agua, escenarios de gobernanza, conflictos sociales y soluciones de carácter sociopolítico y técnico encaminadas a un manejo más sustentable del agua con posibilidades de ser apropiado socialmente. La obra tiene un fuerte componente con tintes de ecología política alrededor de los conflictos por el agua en la metrópoli de Guadalajara y la cuenca Lerma–Chapala–Santiago, sobre todo en aquellos casos donde coinciden situaciones de deterioro ambiental y formas inadecuadas de desarrollo urbano. En las alternativas que se analizan y proponen, se descubre una rica diversidad que encabezan organizaciones sociales, ciudadanos, actores sociopolíticos, universidades e instituciones con diferentes niveles de impacto, vinculación y trayectorias. Se distinguen escalas y formas de gobernanza del agua a nivel de cuenca, zona metropolitana de Guadalajara, municipios y sistemas hidrográficos (microcuencas y sistemas de abastecimiento), además de revisar estilos de desarrollo urbano asociados al manejo del agua con una perspectiva de análisis y de propuesta.ITESO, A.C

NKG2D expression in CD4+ T lymphocytes as a marker of senescence in the aged immune system

Human aging is characterized by changes in the immune system which have a profound impact on the T-cell compartment. These changes are more frequently found in CD8+ T cells, and there are not well-defined markers of differentiation in the CD4+ subset. Typical features of cell immunosenescence are characteristics of pathologies in which the aberrant expression of NKG2D in CD4+ T cells has been described. To evaluate a possible age-related expression of NKG2D in CD4+ T cells, we compared their percentage in peripheral blood from 100 elderly and 50 young adults. The median percentage of CD4+ NKG2D+ in elders was 5.3% (interquartile range (IR): 8.74%) versus 1.4% (IR: 1.7%) in young subjects (p < 0.3 × 10−10). CD28 expression distinguished two subsets of CD4+ NKG2D+ cells with distinct functional properties and differentiation status. CD28+ cells showed an immature phenotype associated with high frequencies of CD45RA and CD31. However, most of the NKG2D+ cells belonged to the CD28null compartment and shared their phenotypical properties. NKG2D+ cells represented a more advanced stage of maturation and exhibited greater response to CMV (5.3 ± 3.1% versus 3.4 ± 2%, p = 0.037), higher production of IFN-γ (40.56 ± 13.7% versus 24 ± 8.8%, p = 0.015), lower activation threshold and reduced TREC content. Moreover, the frequency of the CD4+ NKG2D+ subset was clearly related to the status of the T cells. Higher frequencies of the NKG2D+ subset were accompanied with a gradual decrease of NAIVE and central memory cells, but also with a higher level of more differentiated subsets of CD4+ T cells. In conclusion, CD4+ NKG2D+ represent a subset of highly differentiated T cells which characterizes the senescence of the immune system