Modified ES / OP9 co-culture protocol provides enhanced characterization of hematopoietic progeny.

The in vitro differentiation of ES cells towards a hematopoietic cell fate is useful when studying cell populations that are difficult to access in vivo and for characterizing the earliest genes involved in hematopoiesis, without having to deal with embryonic lethalities. The ES/OP9 co-culture system was originally designed to produce hematopoietic progeny, without the over production of macrophages, as the OP9 stromal cell line is derived from the calvaria of osteopetrosis mutant mice that lack functional M-CSF. The in vitro ES/OP9 co-culture system can be used in order to recapitulate early hematopoietic development. When cultured on OP9 stromal cells, ES cells differentiate into Flk-1+ hemangioblasts, hematopoietic progenitors, and finally mature, terminally differentiated lineages. The standard ES/OP9 co-culture protocol entails the placement of ES cells onto a confluent layer of OP9 cells; as well as, periodic replating steps in order to remove old, contaminating OP9 cells. Furthermore, current protocols involve evaluating only the hematopoietic cells found in suspension and are not optimized for evaluation of ES-derived progeny at each day of differentiation. However, with replating steps and the harvesting of only suspension cells one potentially misses a large portion of ES-derived progeny and developing hematopoietic cells. This issue becomes important to address when trying to characterize hematopoietic defects associated with knockout ES lines. Here we describe a modified ES/mStrawberry OP9 co-culture, which allows for the elimination of contaminating OP9 cells from downstream assays. This method allows for the complete evaluation of all ES-derived progeny at all days of co-culture, resulting in a hematopoietic differentiation pattern, which more directly corresponds to the hematopoietic differentiation pattern observed within the embryo

Decoherence and the Loschmidt echo

Environment--induced decoherence causes entropy increase. It can be quantified using, e.g., the purity $\varsigma={\rm Tr}\rho^2$. When the Hamiltonian of a quantum system is perturbed, its sensitivity to such perturbation can be measured by the Loschmidt echo $\bar M(t)$. It is given by the average squared overlap between the perturbed and unperturbed state. We describe the relation between the temporal behavior of $\varsigma(t)$ and $\bar M(t)$. In this way we show that the decay of the Loschmidt echo can be analyzed using tools developed in the study of decoherence. In particular, for systems with a classically chaotic Hamiltonian the decay of $\varsigma$ and $\bar M$ has a regime where it is dominated by the classical Lyapunov exponent

Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for Ultraviolet Excesse

The search for binarity in AGB stars is of critical importance for our understanding of how planetary nebulae acquire the dazzling variety of aspherical shapes which characterises this class. However, detecting binary companions in such stars has been severely hampered due to their extreme luminosities and pulsations. We have carried out a small imaging survey of AGB stars in ultraviolet light (using GALEX) where these cool objects are very faint, in order to search for hotter companions. We report the discovery of significant far-ultraviolet excesses towards nine of these stars. The far-ultraviolet excess most likely results either directly from the presence of a hot binary companion, or indirectly from a hot accretion disk around the companion.Comment: revised for Astrophysical Journa

Interpretation of runaway electron synchrotron and bremsstrahlung images

The crescent spot shape observed in DIII-D runaway electron synchrotron radiation images is shown to result from the high degree of anisotropy in the emitted radiation, the finite spectral range of the camera and the distribution of runaways. The finite spectral camera range is found to be particularly important, as the radiation from the high-field side can be stronger by a factor $10^6$ than the radiation from the low-field side in DIII-D. By combining a kinetic model of the runaway dynamics with a synthetic synchrotron diagnostic we see that physical processes not described by the kinetic model (such as radial transport) are likely to be limiting the energy of the runaways. We show that a population of runaways with lower dominant energies and larger pitch-angles than those predicted by the kinetic model provide a better match to the synchrotron measurements. Using a new synthetic bremsstrahlung diagnostic we also simulate the view of the Gamma Ray Imager (GRI) diagnostic used at DIII-D to resolve the spatial distribution of runaway-generated bremsstrahlung.Comment: 21 pages, 11 figure

Fractional Newton-Raphson Method Accelerated with Aitken's Method

The Newton-Raphson (N-R) method is characterized by the fact that generating a divergent sequence can lead to the creation of a fractal, on the other hand the order of the fractional derivatives seems to be closely related to the fractal dimension, based on the above, a method was developed that makes use of the N-R method and the fractional derivative of Riemann-Liouville (R-L) that has been named as the Fractional Newton-Raphson (F N-R) method. In the following work we present a way to obtain the convergence of the F N-R method, which seems to be at least linearly convergent for the case where the order $\alpha$ of the derivative is different from one, a simplified way to construct the fractional derivative and fractional integral operators of R-L is presented, an introduction to the Aitken's method is made and it is explained why it has the capacity to accelerate the convergence of iterative methods to finally present the results that were obtained when implementing the Aitken's method in F N-R method.Comment: Newton-Raphson Method, Fractional Calculus, Fractional Derivative of Riemann-Liouville, Method of Aitken. arXiv admin note: substantial text overlap with arXiv:1710.0763

The progression of cancer and metastasis formation: An epigenetic hypothesis

AbstractThe molecular mechanisms of tumor metastasis remain largely unknown and undefined. A recent model suggests that a minor population of cells (cancer stem cells) is programmed to preferentially metastasize to specific organs based on their gene expression patterns. These cells have the ability to generate tumors after implantation into animal hosts, to self-renew and give rise to non-stem cells. In this paper I hypothesize that epigenetic mechanisms could play an important role in tumor metastasis through the reorganization of the bivalent chromatin marks in cancer stem cells in three phases: 1) the reprogramming of epigenetic marks in differentiation master regulator genes responsible for the differentiation to one particular lineage 2) the resolution of these bivalent chromatin marks forces cells to develop the necessary mechanisms to migrate to a new niche and 3) the epigenetic activation of the tissue-specific genes associated with the specific target organ and, simultaneously, the repression of genes associated with alternative developmental pathways

Globally controlled universal quantum computation with arbitrary subsystem dimension

We introduce a scheme to perform universal quantum computation in quantum cellular automata (QCA) fashion in arbitrary subsystem dimension (not necessarily finite). The scheme is developed over a one spatial dimension $N$-element array, requiring only mirror symmetric logical encoding and global pulses. A mechanism using ancillary degrees of freedom for subsystem specific measurement is also presented.Comment: 7 pages, 1 figur

“Problemática de la Integración Universitaria en América del Sur”

Nuestro punto de partida es la actual tendencia que considera la región como una nueva categoría político-territorial donde, la verdadera integración entre países vecinos, sólo podrá lograrse contemplando las dimensiones económico-política y cultural-educativa. El surgimiento de este nuevo paradigma implica un reacomodamiento que genera la creación de nuevos mecanismos de regulación, imponiéndose, en los procesos de integración económica, una atención preferencial a los problemas de índole cultural ya que, los espacios de integración abarcan un amplio espectro que exceden las limitaciones impuestas por las fronteras del Estado-Nación y la macroeconomía. Este trabajo se realiza sobre la base de un análisis crítico de los documentos “Declaración Mundial sobre la Educación Superior en el Siglo XXI: Visión y Acción” y “Marco de Acción Prioritaria para el Cambio y el Desarrollo de la Educación Superior”, aprobados por la Conferencia Mundial sobre la Educación Superior (UNESCO,1998). A los fines de contextualizar el discurso, hacemos una primera aproximación al tema con planteos relacionados con la historia de la integración en América Latina. Nuestra intención es la de derivar la temática al campo regional del Noroeste Argentino teniendo en cuenta la historia institucional-educativa del área. A nivel metodológico comenzamos con una aclaración de los conceptos utilizados y, en segundo lugar, contrastamos el contenido de los documentos mencionados con la praxis integracionista de los últimos 20 años. América Latina, enfrenta el desafío de impulsar un desarrollo sostenible, que favorezca la inserción externa y promueva una creciente equidad interna. A la vez la inserción internacional plantea requisitos de innovación institucional, sustentabilidad ambiental y estrategia educacional. De una rápida revisión de los temas del debate contemporáneo podemos extraer varias líneas fundamentales que modifican los enfoques tradicionales de las problemáticas planteadas por las distintas áreas disciplinares; es a partir de aquí desde dónde, en última instancia, reflexionamos sobre las posibles alternativas de propuestas para la integración de las universidades de la región