290 research outputs found
Book of the Occurrences of the Times to Jeshurun in the Land of Israel - KÌŁorot ha-Ê»itim li-Yeshurun be-ÊŸErets YisÌraÊŸel
This work was authored by Menahem Mendel me-Kaminitz (an ancestor of one of the current translators David Cook) following his first attempt to settle in the Land of Israel in 1834
Emergent Dynamics of Thymocyte Development and Lineage Determination
Experiments have generated a plethora of data about the genes, molecules, and cells involved in thymocyte development. Here, we use a computer-driven simulation that uses data about thymocyte development to generate an integrated dynamic representationâa novel technology we have termed reactive animation (RA). RA reveals emergent properties in complex dynamic biological systems. We apply RA to thymocyte development by reproducing and extending the effects of known gene knockouts: CXCR4 and CCR9. RA simulation revealed a previously unidentified role of thymocyte competition for major histocompatability complex presentation. We now report that such competition is required for normal anatomical compartmentalization, can influence the rate of thymocyte velocities within chemokine gradients, and can account for the disproportion between single-positive CD4 and CD8 lineages developing from double-positive precursors
The Immune System Computes the State of the Body: Crowd Wisdom, Machine Learning, and Immune Cell Reference Repertoires Help Manage Inflammation
Here, we outline an overview of the mammalian immune system that updates and extends the classical clonal selection paradigm. Rather than focusing on strict self-not-self discrimination, we propose that the system orchestrates variable inflammatory responses that maintain the body and its symbiosis with the microbiome while eliminating the threat from pathogenic infectious agents and from tumors. The paper makes four points:
The immune system classifies healthy and pathologic states of the bodyâincluding both self and foreign elementsâby deploying individual lymphocytes as cellular computing machines; immune cells transform input signals from the body into an output of specific immune reactions.Rather than independent clonal responses, groups of individually activated immune-system cells co-react in lymphoid organs to make collective decisions through a type of self-organizing swarm intelligence or crowd wisdom.Collective choices by swarms of immune cells, like those of schools of fish, are modified by relatively small numbers of individual regulators responding to shifting conditionsâsuch collective inflammatory responses are dynamically responsive.Self-reactive autoantibody and T-cell receptor (TCR) repertoires shared by healthy individuals function in a biological version of experience-based supervised machine learning. Immune system decisions are primed by formative experience with training sets of self-antigens encountered during lymphocyte development; these initially trained T cell and B cell repertoires form a Wellness Profile that then guides immune responses to test sets of antigens encountered later. This experience-based machine learning strategy is analogous to that deployed by supervised machine-learning algorithms.We propose experiments to test these ideas. This overview of the immune system bears clinical implications for monitoring wellness and for treating autoimmune disease, cancer, and allograft reactions
Protegidos, sindicalizados y pobres : el impacto de distorsiones sobre la asignacioÌn de recursos y la productividad
Se desarrollaraÌ un modelo para explicar la mala asignacioÌn de recursos entre
sectores a partir de la implementacioÌn de distorsiones en el mercado laboral y en el
mercado de bienes. En base a un primer equilibrio competitivo se realiza un ejercicio de
estaÌtica comparativa donde primero se introduce una tarifa proteccionista y luego se
agrega el poder sindical. Realizando una comparacioÌn entre los distintos casos, se logra
demostrar coÌmo las distorsiones y las posibles interacciones entre ellas generan un
problema de asignacioÌn de recursos que resulta en un deterioro de la productividad. Las
conclusiones del modelo podriÌan servir como fundamento para explicar los bajos
ingresos croÌnicos de LatinoameÌrica
Deconstructing blazars: A different scheme for jet kinematics in flat-spectrum AGN
Recent VLBI studies of the morphology and kinematics of individual BL Lac
objects (S5 1803+784, PKS 0735+178, etc.) have revealed a new paradigm for the
pc-scale jet kinematics of these sources. Unlike the apparent superluminal
outward motions usually observed in blazars, most, if not all, jet components
in these sources appear to be stationary with respect to the core, while
exhibiting strong changes in their position angles. As a result, the jet ridge
lines of these sources evolve substantially, at times forming a wide
channel-flow. We investigate the Caltech-Jodrell Bank flat-spectrum (CJF)
sample of radio-loud active galaxies to study this new kinematic scenario for
flat-spectrum AGN. We develop a number of tools that extract information about
the apparent linear and angular evolution of the CJF jet ridge lines, as well
as their morphology. In this way, we study both radial and non-radial apparent
motions in the CJF jets. We find that approximately half of the sample shows
appreciable apparent jet widths (), with BL Lac jet ridge lines
showing significantly larger apparent widths than both quasars and radio
galaxies. In addition, BL Lac jet ridge lines are found to change their
apparent width more strongly. Finally, BL Lac jet ridge lines show the least
apparent linear evolution, which translates to the smallest apparent expansion
speeds for their components. We find compelling evidence supporting a
substantially different kinematic scenario for flat-spectrum radio-AGN jets and
in particular for BL Lac objects. In addition, we find that variability is
closely related to the properties of a source's jet ridge line. Variable
quasars are found to show "BL Lac like" behavior, compared to their
non-variable counterparts.Comment: 16 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
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