124 research outputs found
Expectations for the Deep Impact collision from cometary nuclei modelling
Using the cometary nucleus model developed by Espinasse et al. (1991), we
calculate the thermodynamical evolution of Comet 9P/Tempel 1 over a period of
360 years. Starting from an initially amorphous cometary nucleus which
incorporates an icy mixture of H2O and CO, we show that, at the time of Deep
Impact collision, the crater is expected to form at depths where ice is in its
crystalline form. Hence, the subsurface exposed to space should not be
primordial. We also attempt an order-of-magnitude estimate of the heating and
material ablation effects on the crater activity caused by the 370 Kg
projectile released by the DI spacecraft. We thus show that heating effects
play no role in the evolution of crater activity. We calculate that the CO
production rate from the impacted region should be about 300-400 times higher
from the crater resulting from the impact with a 35 m ablation than over the
unperturbed nucleus in the immediate post-impact period. We also show that the
H2O production rate is decreased by several orders of magnitude at the crater
base just after ablation
Ordinary Unfamiliarity: Foundation Pedagogy through the Critique of the Everyday
In our new foundation program, we proceed from two principles of instruction: first, we direct the focus of work away from conventional architectural topics and use analogy to awaken native critical insight; second, we postpone traditional design activity by strictly emphasizing observation skills and critical analysis. We delay design activity until the first quarter of the second year, in preparation for which we organize firstyear \tudio workshops around short iterative exercises that capitalize on the students\u27 familiarity with the everyday world. We then structure these problems to render the everyday world in unfamiliar terms. This oscillation between the ordinary and the unfamiliar greatly intensifies the analogical resonance between everyday experience and the production of buildings. The result is greater confidence in critical thinking earlier in the student\u27s academic career
Observation of radio galaxies with HAWC
The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an
extensive air shower array located in Puebla, Mexico. The closest radio galaxy
within the HAWC field of view, M87, has been detected in very high energies. In
this work we report upper limits on the TeV {\gamma}-ray flux of the radio
galaxy M87. At a distance of 16 Mpc, M87 is a supergiant elliptical galaxy
located in the Virgo Cluster that has been observed from radio wavelengths to
TeV {\gamma}-rays. Although a single-zone synchrotron self-Compton model has
been successfully used to explain the spectral energy distribution of this
source up to a few GeV, the {\gamma}-ray spectrum at TeV has been interpreted
within different theoretical models. We discuss the implications of these upper
limits on the photo-hadronic interactions, as well as the number of neutrino
events expected in the IceCube neutrino telescope.Comment: 8 pages, 1 figure, ICRC 201
BRST Cohomology is Lie Algebroid Cohomology
In this paper we demonstrate that the exterior algebra of an Atiyah Lie
algebroid generalizes the familiar notions of the physicist's BRST complex. To
reach this conclusion, we develop a general picture of Lie algebroid morphisms
as commutative diagrams between algebroids preserving the geometric structure
encoded in their brackets. We illustrate that a necessary and sufficient
condition for such a diagram to define a morphism is that the two algebroids
possess gauge-equivalent connections. This observation indicates that the set
of Lie algebroid morphisms should be regarded as equivalent to the set of local
diffeomorphisms and gauge transformations. Moreover, a Lie algebroid morphism
being a chain map in the exterior algebra sense ensures that morphic algebroids
are cohomologically equivalent. The Atiyah Lie algebroids derived from
principal bundles with common base manifolds and structure groups may therefore
be divided into equivalence classes of morphic algebroids. Each equivalence
class possesses a representative which we refer to as the trivialized Lie
algebroid, and we show that the exterior algebra of the trivialized algebroid
gives rise to the BRST complex. We conclude by illustrating the usefulness of
Lie algebroid cohomology in computing quantum anomalies. In particular, we pay
close attention to the fact that the geometric intuition afforded by the Lie
algebroid (which was absent in the naive BRST complex) provides hints of a
deeper picture that simultaneously geometrizes the consistent and covariant
forms of the anomaly. In the algebroid construction, the difference between the
consistent and covariant anomalies is simply a different choice of basis.Comment: 24 pages, 1 figure, LaTe
Bayesian Renormalization
In this note we present a fully information theoretic approach to
renormalization inspired by Bayesian statistical inference, which we refer to
as Bayesian Renormalization. The main insight of Bayesian Renormalization is
that the Fisher metric defines a correlation length that plays the role of an
emergent RG scale quantifying the distinguishability between nearby points in
the space of probability distributions. This RG scale can be interpreted as a
proxy for the maximum number of unique observations that can be made about a
given system during a statistical inference experiment. The role of the
Bayesian Renormalization scheme is subsequently to prepare an effective model
for a given system up to a precision which is bounded by the aforementioned
scale. In applications of Bayesian Renormalization to physical systems, the
emergent information theoretic scale is naturally identified with the maximum
energy that can be probed by current experimental apparatus, and thus Bayesian
Renormalization coincides with ordinary renormalization. However, Bayesian
Renormalization is sufficiently general to apply even in circumstances in which
an immediate physical scale is absent, and thus provides an ideal approach to
renormalization in data science contexts. To this end, we provide insight into
how the Bayesian Renormalization scheme relates to existing methods for data
compression and data generation such as the information bottleneck and the
diffusion learning paradigm.Comment: 20 pages, no figures. V2: Citation format fixed, references adde
Reattachment of the Multifidus Tendon in Lumbar Surgery to Decrease Postoperative Back Pain: A Technical Note.
The posterior midline approach to the lumbar spine requires significant manipulation of the paraspinal muscles. Muscle detachment and retraction results in iatrogenic damage such as crush injury, devascularization, and denervation, all of which have been associated with postoperative pain. The muscle most directly affected by the posterior approach is the lumbar multifidus (LM), the largest and most medial of the deep lumbar paraspinal muscles. The effects of the posterior approach on the integrity of the LM is concerning, as multiple studies have demonstrated that intraoperative injuries sustained by the LM lead to postoperative muscle atrophy and potentially worsening low back pain. Given the inevitability of intraoperative paraspinal muscle manipulation when using the posterior approach, this technical note describes methods by which surgeons may minimize LM tissue disruption and restore the anatomical position of the LM to ultimately expedite recovery, minimize postoperative pain, and improve patient satisfaction
Junge Hochschul- und Mediendidaktik. Forschung und Praxis im Dialog
Am 29./30.05.2012 fand in Hamburg die Konferenz “Junges Forum Hochschul- und Mediendidaktik” (JFHM) statt. Ausgerichtet vom Zentrum für Hochschul- und Weiterbildung (ZHW) der Universität Hamburg, kooperierten bei der Konzeption und Durchführung der Tagung Vertreterinnen und Vertreter aus hochschul- und mediendidaktischer Berufspraxis mit Vertreterinnen der wissenschaftlichen Nachwuchsförderung aus der Deutschen Gesellschaft für Hochschuldidaktik (DGHD) und der Gesellschaft für Medien in der Wissenschaft (GMW). Das Ziel der Tagung war die Sichtbarmachung und Vernetzung theoretischer und praktischer hochschul- und mediendidaktischer Arbeit. Der vorliegende Sammelband vereint Beiträge der Konferenz und gibt so einen Einblick in aktuelle Themen von Hochschul- und Mediendidaktik - und zwar speziell aus der Perspektive jüngerer Forscherinnen und Forscher sowie Praktikerinnen und Praktiker. Er gibt damit auch Anhaltspunkte dafür, welche Themen diese Arbeitsbereiche in Zukunft (weiter) beschäftigen werden. (DIPF/Autor
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Rare variant analysis of 4241 pulmonary arterial hypertension cases from an international consortium implicates FBLN2, PDGFD, and rare de novo variants in PAH
Abstract: Background: Pulmonary arterial hypertension (PAH) is a lethal vasculopathy characterized by pathogenic remodeling of pulmonary arterioles leading to increased pulmonary pressures, right ventricular hypertrophy, and heart failure. PAH can be associated with other diseases (APAH: connective tissue diseases, congenital heart disease, and others) but often the etiology is idiopathic (IPAH). Mutations in bone morphogenetic protein receptor 2 (BMPR2) are the cause of most heritable cases but the vast majority of other cases are genetically undefined. Methods: To identify new risk genes, we utilized an international consortium of 4241 PAH cases with exome or genome sequencing data from the National Biological Sample and Data Repository for PAH, Columbia University Irving Medical Center, and the UK NIHR BioResource – Rare Diseases Study. The strength of this combined cohort is a doubling of the number of IPAH cases compared to either national cohort alone. We identified protein-coding variants and performed rare variant association analyses in unrelated participants of European ancestry, including 1647 IPAH cases and 18,819 controls. We also analyzed de novo variants in 124 pediatric trios enriched for IPAH and APAH-CHD. Results: Seven genes with rare deleterious variants were associated with IPAH with false discovery rate smaller than 0.1: three known genes (BMPR2, GDF2, and TBX4), two recently identified candidate genes (SOX17, KDR), and two new candidate genes (fibulin 2, FBLN2; platelet-derived growth factor D, PDGFD). The new genes were identified based solely on rare deleterious missense variants, a variant type that could not be adequately assessed in either cohort alone. The candidate genes exhibit expression patterns in lung and heart similar to that of known PAH risk genes, and most variants occur in conserved protein domains. For pediatric PAH, predicted deleterious de novo variants exhibited a significant burden compared to the background mutation rate (2.45×, p = 2.5e−5). At least eight novel pediatric candidate genes carrying de novo variants have plausible roles in lung/heart development. Conclusions: Rare variant analysis of a large international consortium identified two new candidate genes—FBLN2 and PDGFD. The new genes have known functions in vasculogenesis and remodeling. Trio analysis predicted that ~ 15% of pediatric IPAH may be explained by de novo variants
Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications
This work was supported by a restricted research grant of Bayer AG
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