Fundamental Solutions and Decay of Fully Non-local Problems

In this paper, we study a fully non-local reaction-diffusion equation which is non-local both in time and space. We apply subordination principles to construct the fundamental solutions of this problem, which we use to find a representation of the mild solutions. Moreover, using techniques of Harmonic Analysis and Fourier Multipliers, we obtain the temporal decay rates for the mild solutions

Normal Coordinates and Primitive Elements in the Hopf Algebra of Renormalization

We introduce normal coordinates on the infinite dimensional group $G$ introduced by Connes and Kreimer in their analysis of the Hopf algebra of rooted trees. We study the primitive elements of the algebra and show that they are generated by a simple application of the inverse Poincar\'e lemma, given a closed left invariant 1-form on $G$. For the special case of the ladder primitives, we find a second description that relates them to the Hopf algebra of functionals on power series with the usual product. Either approach shows that the ladder primitives are given by the Schur polynomials. The relevance of the lower central series of the dual Lie algebra in the process of renormalization is also discussed, leading to a natural concept of $k$-primitiveness, which is shown to be equivalent to the one already in the literature.Comment: Latex, 24 pages. Submitted to Commun. Math. Phy

FARM PROGRAM PAYMENTS AND ECONOMIES OF SCALE

Economies of scale are investigated and the impacts of farm payment limitations for producers of cotton and soybeans in Mississippi are evaluated. Limits proposed by the Senate following the recent farm bill debate are overlaid on estimates of the scale economies for the cost of producing these crops to determine the different impacts on farm efficiency and welfare benefits.Agricultural and Food Policy,

Linfocitos T reguladores y respuesta inmune

Immune regulation or immune suppression has been proposed to play a key role to maintain tolerance to self antigens, avoid development of autoimmune diseases, prevent runaway responses to pathogens or allergens, function to temper the massive proinflammatory stimulus created by bacteria within the gut, help maintain a balance with commensal microflora and facilitate tumors' escape from immune monitoring. Although several distinct cell lineages may participate in these control of the immune response, an important population of CD4+ T cells, known as regulatory T cells, play key roles in maintaining tolerance to self antigens. These regulatory T cells can suppress the proliferation and/or functions of various immune cells including CD4+ T cells, CD8+ T cells, NKT cells, dendritic cells (DCs), monocytes/macrophages, B cells, and NK cells. Naturally occurring CD4+ CD25+ Foxp3+ regulatory T cells (nTregs) represent 5-10% of peripheral CD4 T cells, and recent studies in the mouse have shown that these cells are critical regulators of immune tolerance. In recent years progress in characterizing many of these cell types has been accelerate, most notably by discovery of the relevance of the transcription factor Foxp3. It is established that under specific conditions naïve CD4+CD25-Foxp3- T cells can be converted into Foxp3+ inducible regulatory T cells (iTregs) and several conversion/expansion protocols have been described. Such protocols usually involve T cell stimulation under conditions of cytokine modification where transforming growth factor-beta (TGF-b) has been shown to play a critical role. These inducible populations of Tregs are characterized by expression of Foxp3 and the ability to inhibit the proliferation of effector T cells in vitro. Moreover, several studies have shown that these ex vivo generated Foxp3+ cells can regulate T cell responses in vivo following adoptive transfer into immunodeficient recipients.    La regulación inmune o inmunosupresión desempeña un rol trascendental en la mantención de la tolerancia a antígenos propios, evita la aparición de enfermedades autoinmunes, controla el desarrollo de una respuesta inmune exagerada frente a agentes patógenos o frente a distintos alergenos, ayuda a disminuir el masivo estímulo proinflamatorio de la microflora comensal del tracto digestivo y favorece el escape de las células tumorales al control inmunológico. Aunque distintas poblaciones celulares pueden participar en este importante control de la respuesta inmune, un grupo particular de linfocitos TCD4+, conocidos como linfocitos T reguladores, resulta fundamental en la mantención de la tolerancia a antígenos propios. Estos linfocitos T reguladores pueden suprimir la proliferación y/o función de diversas células del sistema inmune, incluyendo linfocitos TCD4+, linfocitos TCD8+, células NKT, células dendríticas, monocitos/macrófagos, linfocitos B y células NK. Los linfocitos T reguladores naturales CD4+ CD25+ Foxp3+ (nTregs) representan el 5-10% de los linfocitos T CD4 periféricos, y estudios en ratón han demostrado que estas células son reguladores esenciales en la mantención de la tolerancia inmunológica. En los últimos años los avances en la caracterización de Tregs han sido vertiginosos, sobre todo por el descubrimiento del relevante rol desempeñado por el factor de transcripción Foxp3. Se ha observado que en determinadas condiciones in vitro, linfocitos T vírgenes CD4+ CD25- Foxp3- se pueden convertir en linfocitos T reguladores inducibles Foxp3+ (iTregs), mediante diversos protocolos de conversión y/o expansión. Estos protocolos generalmente implican la activación de linfocitos TCD4+ bajo distintas condiciones experimentales, incluyendo el agregado exógeno de distintas citoquinas, como el factor de.crecimiento transformante-beta (TGF-β), que parece cumplir una función crítica en los procesos de activación y diferenciación. Estas poblaciones inducibles de Tregs se caracterizan por la expresión de Foxp3 y por la capacidad de inhibir la proliferación de de linfocitos T efectores in vitro. Diversos estudios han demostrado además, que estos linfocito Foxp3+, generados ex vivo, pueden regular la respuesta celular T in vivo, luego de su transferencia adoptiva en receptores inmunodeficientes.  

Resistencia de profesores de ciencias en los cambios de sus prácticas en el aula y sus representaciones sobre la enseñanza y el aprendizaje de las ciencias

Esta investigación indagó los efectos de un programa de capacitación en didáctica de las ciencias, realizada a cuatro profesores en Chile, sobre las representaciones que ellos tienen de la enseñanza y el aprendizaje de las ciencias, y sobre sus prácticas en el aula. Pudimos observar que, luego de cinco meses de trabajo, los profesores generar cambios en la estructura de sus clases, incorporando actividades de inicio y desarrollo pero no lograr realizar un cierre pedagógico. Además incorporan la evaluación de las habilidades, discriminando si existía coherencia entre los tipos de actividades que desarrollaban y la forma de evaluar a sus estudiantes. Sin embrago, los profesores no logran modificar sus representaciones sobre la enseñanza y aprendizaje de las ciencias, y atribuyen falencias de sus prácticas a los estudiantes o al establecimiento

Microlensing of the broad-line region in the quadruply imaged quasar HE0435-1223

Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223 acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope, we have detected a clear microlensing effect in images A and D. While microlensing affects the blue and red wings of the H{\alpha} line profile in image D very differently, it de-magnifies the line core in image A. The combination of these different effects sets constraints on the line-emitting region; these constraints suggest that a rotating ring is at the origin of the H{\alpha} line. Visible spectra obtained in 2004 and 2012 indicate that the MgII line profile is microlensed in the same way as the H{\alpha} line. Our results therefore favour flattened geometries for the low-ionization line-emitting region, for example, a Keplerian disk. Biconical models cannot be ruled out but require more fine-tuning. Flux ratios between the different images are also derived and confirm flux anomalies with respect to estimates from lens models with smooth mass distributions.Comment: 6 pages, 4 figures, 3 tables, accepted by A&A on 10 April 201

Experiences in porting mini-applications to OpenACC and OpenMP on heterogeneous systems

This article studies mini-applications—Minisweep, GenASiS, GPP, and FF—that use computational methods commonly encountered in HPC. We have ported these applications to develop OpenACC and OpenMP versions, and evaluated their performance on Titan (Cray XK7 with K20x GPUs), Cori (Cray XC40 with Intel KNL), Summit (IBM AC922 with Volta GPUs), and Cori-GPU (Cray CS-Storm 500NX with Intel Skylake and Volta GPUs). Our goals are for these new ports to be useful to both application and compiler developers, to document and describe the lessons learned and the methodology to create optimized OpenMP and OpenACC versions, and to provide a description of possible migration paths between the two specifications. Cases where specific directives or code patterns result in improved performance for a given architecture are highlighted. We also include discussions of the functionality and maturity of the latest compilers available on the above platforms with respect to OpenACC or OpenMP implementations