926 research outputs found
HESS J1632-478: an energetic relic
HESS J1632-478 is an extended and still unidentified TeV source in the
galactic plane. In order to identify the source of the very high energy
emission and to constrain its spectral energy distribution, we used a deep
observation of the field obtained with XMM-Newton together with data from
Molonglo, Spitzer and Fermi to detect counterparts at other wavelengths. The
flux density emitted by HESS J1632-478 peaks at very high energies and is more
than 20 times weaker at all other wavelengths probed. The source spectrum
features two large prominent bumps with the synchrotron emission peaking in the
ultraviolet and the external inverse Compton emission peaking in the TeV. HESS
J1632-478 is an energetic pulsar wind nebula with an age of the order of 10^4
years. Its bolometric (mostly GeV-TeV) luminosity reaches 10% of the current
pulsar spin down power. The synchrotron nebula has a size of 1 pc and contains
an unresolved point-like X-ray source, probably the pulsar with its wind
termination shock.Comment: A&A accepted, 9 pages, 5 figures, 4 table
Evaluating quality in online asynchronous interactions between students and discussion facilitators
Online discussion forums have become an essential part of university courses, whether the course is conducted online, or face to face, or in mixed or blended mode. Discussion forums are considered to engage students better with the course content and encourage them to share and gain knowledge from each other. However, online engagement does not always happen automatically between students. Hence grading of discussion forum participation has been recommended to ensure quality student participation. Currently, a major focus has been put onto the better use of discussion forums, but the way in which the quality of participation can be evaluated has yet to be adequately investigated. Furthermore, evaluation of the instructor participation in a discussion forum and its impact on students and their contributions is lacking. In this paper, we report on our research into online discussion forum quality through analysis of discussion forum activities, along with student focus group meetings and instructor interviews. We have devised a set of criteria for evaluating discussion forum activities. Our results show that students depend highly on the instructor's feedback and the participation of the students can only be evaluated with reference to the moderation of the instructors
I reinterventi nell’iperparatiroidismo
reinterventi in chirurgia paratiroidea rappresentano una sfida impegnativa per il chirurgo che deve valutare attentamente i dati operatori e istologici del primo intervento, usare una diagnostica accurata preoperatoria con ecografia e scintigrafia con sestamibi e avere ben presente l’anatomia e l’embriologia delle ghiandole paratiroidee. Elementi fondamentali per ottenere un successo chirurgico sono l’uso del dosaggio intraoperatorio del paratormone e una grande esperienza del chirurgo. Seguendo tali principi si arriva a ottenere una remissione del quadro iperparatiroideo nell’85-90% per l’HPT I e nel 70% per l’HPT II e III.
Gli Autori presentano la loro casistica di 75 reinterventi dopo HPT I e di 85 reinterventi dopo HPT II e III, su una casistica totale di 2072 interventi di paratiroidectomia eseguiti fra gennaio 1975 e ottobre 2009
Analysis of Petri Net Models through Stochastic Differential Equations
It is well known, mainly because of the work of Kurtz, that density dependent
Markov chains can be approximated by sets of ordinary differential equations
(ODEs) when their indexing parameter grows very large. This approximation
cannot capture the stochastic nature of the process and, consequently, it can
provide an erroneous view of the behavior of the Markov chain if the indexing
parameter is not sufficiently high. Important phenomena that cannot be revealed
include non-negligible variance and bi-modal population distributions. A
less-known approximation proposed by Kurtz applies stochastic differential
equations (SDEs) and provides information about the stochastic nature of the
process. In this paper we apply and extend this diffusion approximation to
study stochastic Petri nets. We identify a class of nets whose underlying
stochastic process is a density dependent Markov chain whose indexing parameter
is a multiplicative constant which identifies the population level expressed by
the initial marking and we provide means to automatically construct the
associated set of SDEs. Since the diffusion approximation of Kurtz considers
the process only up to the time when it first exits an open interval, we extend
the approximation by a machinery that mimics the behavior of the Markov chain
at the boundary and allows thus to apply the approach to a wider set of
problems. The resulting process is of the jump-diffusion type. We illustrate by
examples that the jump-diffusion approximation which extends to bounded domains
can be much more informative than that based on ODEs as it can provide accurate
quantity distributions even when they are multi-modal and even for relatively
small population levels. Moreover, we show that the method is faster than
simulating the original Markov chain
IGR J11014-6103: a newly discovered pulsar wind nebula?
Context: IGRJ11014-6103 is one of the still unidentified hard X-ray INTEGRAL
sources, reported for the first time in the 4th IBIS/ISGRI catalog. Aims: We
investigated the nature of IGR J11014-6103 by carrying out a multiwavelength
analysis of the available archival observations performed in the direction of
the source. Methods: We present first the results of the timing and spectral
analysis of all the X-ray observations of IGR J11014-6103 carried out with
ROSAT, ASCA, Einstein, Swift, and XMM-Newton, and then use them to search for
possible counterparts to the source in the optical, infra-red, radio and
gamma-ray domain. Results: Our analysis revealed that IGR J11014-6103 is
comprised of three different X-ray emitting regions: a point-like source, an
extended object and a cometary-like "tail" (~4 arcmin). A possible radio
counterpart positionally coincident with the source was also identified.
Conclusions: Based on these results, we suggest that the emission from IGR
J11014-6103 is generated by a pulsar wind nebula produced by a high-velocity
pulsar. IGR J11014-6103 might be the first of these systems detected with
INTEGRAL IBIS/ISGRI.Comment: A&A accepted, 8 pages, 8 figures, 2 table
China and the art of (technological) war
China se encamina a convertirse en una potencia tecnológica a mediados del siglo XXI. Este proceso se funda sobre cuatro pilares: sostenido incremento del presupuesto asignado al desarrollo cientÃfico-tecnológico, su directa vinculación con estrategias de innovación a fin de aumentar la productividad y sostener competitividad exportadora, creación e internacionalización de firmas tecnológicas, y expectativas gubernamentales por cerrar las brechasde conocimiento aún existentes que separan a China de competidores asiáticos y occidentales. A lo largo de cuatro décadas, las reformas pro mercado confirman esta senda de transformación y generación de capacidades en sectores tecnológicos de punta. La competencia estratégica con Estados Unidos acelera esta carrera y confirma objetivos sobre posicionamiento de firmas tecnológicas chinas como lÃderes en inteligencia artificial (IA), telecomunicaciones y redes 5G.China is on the wayto become a technological power in the mid-21st Century. This process is based on four pillars: sustained increase in science and technology development budget allocations, its direct link to innovation strategies to increase productivity and up-keep exploration competitiveness, high-tech firm creation and internationalization, and national goals aimed at closing the gap between domestic S&T capacities and those of the more advanced developed Asian and Western economies. Over four decades, pro-market reforms have confirmed this path, towards transformation and capacity building in cutting edge technological sectors. Strategic tensions with the United States speed up this race and confirm China's national goals for its companies to take the lead in artificial intelligence (AI), telecommunications and 5G networks.Instituto de Relaciones Internacionale
Resilience of small-scale societies: a view from drylands.
To gain insights on long-term social-ecological resilience, we examined adaptive responses of small-scale societies to dryland-related hazards in different regions and chronological periods, spanning from the mid-Holocene to the present. Based on evidence from Africa (Sahara and Sahel), Asia (south margin of the Thar desert), and Europe (South Spain), we discuss key traits and coping practices of small-scale societies that are potentially relevant for building resilience. The selected case studies illustrate four main coping mechanisms: mobility and migration, storage, commoning, and collective action driven by religious beliefs. Ultimately, the study of resilience in the context of drylands emphasizes the importance of adaptive traits and practices that are distinctive of small-scale societies: a strong social-ecological coupling, a solid body of traditional ecological knowledge, and a high degree of internal cohesion and self-organization.SP2016http://www.ecologyandsociety.org/vol21/iss2/art53
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