484 research outputs found
Radiation management and credentialing of fluoroscopy users
During the last 15 years, developments in X-ray technologies have substantially improved the ability of practitioners to treat patients using fluoroscopically guided interventional techniques. Many of these procedures require a greater use of fluoroscopy and more recording of images. This increases the potential for radiation-induced dermatitis and epilation, as well as severe radiation-induced burns to patients. Many fluoroscope operators are untrained in radiation management and do not realize that these procedures increase the risk of radiation injury and radiation-induced cancer in personnel as well as patients. The hands of long-time fluoroscope operators in some cases exhibit radiation damage—especially when sound radiation protection practices have not been followed. In response, the Center for Devices and Radiological Health of the United States Food and Drug Administration has issued an Advisory calling for proper training of operators. Hospitals and administrators need to support and enforce the need for this training by requiring documentation of credentials in radiation management as a prerequisite for obtaining fluoroscopy privileges. A concerted effort on the part of professional medical organizations and regulatory agencies will be required to train fluoroscopy users to prevent physicians from unwittingly imparting serious radiation injuries to their patients
First discovery of Holocene cryptotephra in Amazonia
The use of volcanic ash layers for dating and correlation (tephrochronology) is widely applied in the study of past environmental changes. We describe the first cryptotephra (non-visible volcanic ash horizon) to be identified in the Amazon basin, which is tentatively attributed to a source in the Ecuadorian Eastern Cordillera (0–1°S, 78-79°W), some 500-600 km away from our field site in the Peruvian Amazon. Our discovery 1) indicates that the Amazon basin has been subject to volcanic ash fallout during the recent past; 2) highlights the opportunities for using cryptotephras to date palaeoenvironmental records in the Amazon basin and 3) indicates that cryptotephra layers are preserved in a dynamic Amazonian peatland, suggesting that similar layers are likely to be present in other peat sequences that are important for palaeoenvironmental reconstruction. The discovery of cryptotephra in an Amazonian peatland provides a baseline for further investigation of Amazonian tephrochronology and the potential impacts of volcanism on vegetation
Effects of exposure to cigarette smoke prior to pregnancy in diabetic rats
<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to evaluate the effects of cigarette smoke exposure before pregnancy on diabetic rats and their offspring development.</p> <p>Methods</p> <p>Diabetes was induced by streptozotocin and cigarette smoke exposure was conducted by mainstream smoke generated by a mechanical smoking device and delivered into a chamber. Diabetic female Wistar rats were randomly distributed in four experimental groups (n minimum = 13/group): nondiabetic (ND) and diabetic rats exposed to filtered air (D), diabetic rats exposed to cigarette smoke prior to and into the pregnancy period (DS) and diabetic rats exposed to cigarette smoke prior to pregnancy period (DSPP). At day 21 of pregnancy, rats were killed for maternal biochemical determination and reproductive outcomes.</p> <p>Results</p> <p>The association of diabetes and cigarette smoke in DSPP group caused altered glycemia at term, reduced number of implantation and live fetuses, decreased litter and maternal weight, increased pre and postimplantation loss rates, reduced triglyceride and VLDL-c concentrations, increased levels of thiol groups and MDA. Besides, these dams presented increased SOD and GSH-Px activities. However, the increased antioxidant status was not sufficient to prevent the lipid peroxidation observed in these animals.</p> <p>Conclusion</p> <p>Despite the benefits stemming from smoking interruption during the pregnancy of diabetic rats, such improvement was insufficient to avoid metabolic alterations and provide an adequate intrauterine environment for embryofetal development. Therefore, these results suggest that it is necessary to cease smoking extensive time before planning pregnancy, since stopping smoking only when pregnancy is detected may not contribute effectively to fully adequate embryofetal development.</p
Conformal symmetry of the critical 3D Ising model inside a sphere
We perform Monte-Carlo simulations of the three-dimensional Ising model at the critical temperature and zero magnetic field. We simulate the system in a ball with free boundary conditions on the two dimensional spherical boundary. Our results for one and two point functions in this geometry are consistent with the predictions from the conjectured conformal symmetry of the critical Ising model.We are grateful to Slava Rychkov for useful discussions and for suggesting this work. The research leading to these results has received funding from the [European Union] Seventh Framework Programme [FP7-People-2010-IRSES] and [FP7/2007-2013] under grant agreements No 269217, 317089 and No 247252, and from the grant CERN/FP/123599/2011. Centro de Física do Porto is partially funded by the Foundation for Science and Technology of Portugal (FCT). J.V.P.L. acknowledges funding from projecto Operacional Regional do Norte, within Quadro de Referência Estratégico Nacional (QREN) and through Fundo Europeu de Desenvolvimento Regional (FEDER), Ref. NORTE-07-0124-FEDER- 00003
Neutron Majorana mass from exotic instantons
We show how a Majorana mass for the Neutron could result from
non-perturbative quantum gravity effects peculiar to string theory. In
particular, "exotic instantons" in un-oriented string compactifications with
D-branes extending the (supersymmetric) standard model could indirectly produce
an effective operator delta{m} n^t n+h.c. In a specific model with an extra
vector-like pair of `quarks', acquiring a large mass proportional to the string
mass scale (exponentially suppressed by a function of the string moduli
fields), delta{m} can turn out to be as low as 10^{-24}-10^{-25} eV. The
induced neutron-antineutron oscillations could take place with a time scale
tau_{n\bar{n}} > 10^8 s, that could be tested by the next generation of
experiments. On the other hand, proton decay and FCNC's are automatically
strongly suppressed and are compatible with the current experimental limits.
Depending on the number of brane intersections, the model may also lead to the
generation of Majorana masses for R-handed neutrini. Our proposal could also
suggest neutron-neutralino or neutron-axino oscillations, with implications in
UCN, Dark Matter Direct Detection, UHECR and Neutron-Antineutron oscillations.
This suggests to improve the limits on neutron-antineutron oscillations, as a
possible test of string theory and quantum gravity.Comment: 35 pages, 11 figures. More comments on neutron-neutralino mixin
Asteroseismology and Interferometry
Asteroseismology provides us with a unique opportunity to improve our
understanding of stellar structure and evolution. Recent developments,
including the first systematic studies of solar-like pulsators, have boosted
the impact of this field of research within Astrophysics and have led to a
significant increase in the size of the research community. In the present
paper we start by reviewing the basic observational and theoretical properties
of classical and solar-like pulsators and present results from some of the most
recent and outstanding studies of these stars. We centre our review on those
classes of pulsators for which interferometric studies are expected to provide
a significant input. We discuss current limitations to asteroseismic studies,
including difficulties in mode identification and in the accurate determination
of global parameters of pulsating stars, and, after a brief review of those
aspects of interferometry that are most relevant in this context, anticipate
how interferometric observations may contribute to overcome these limitations.
Moreover, we present results of recent pilot studies of pulsating stars
involving both asteroseismic and interferometric constraints and look into the
future, summarizing ongoing efforts concerning the development of future
instruments and satellite missions which are expected to have an impact in this
field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume
14, Issue 3-4, pp. 217-36
Improved nutrition in adolescents and young adults after childhood cancer - INAYA study
Biodiversity of the Deep-Sea Continental Margin Bordering the Gulf of Maine (NW Atlantic): Relationships among Sub-Regions and to Shelf Systems
Background: In contrast to the well-studied continental shelf region of the Gulf of Maine, fundamental questions regarding
the diversity, distribution, and abundance of species living in deep-sea habitats along the adjacent continental margin
remain unanswered. Lack of such knowledge precludes a greater understanding of the Gulf of Maine ecosystem and limits
development of alternatives for conservation and management.
Methodology/Principal Findings: We use data from the published literature, unpublished studies, museum records and
online sources, to: (1) assess the current state of knowledge of species diversity in the deep-sea habitats adjacent to the Gulf
of Maine (39–43uN, 63–71uW, 150–3000 m depth); (2) compare patterns of taxonomic diversity and distribution of
megafaunal and macrofaunal species among six distinct sub-regions and to the continental shelf; and (3) estimate the
amount of unknown diversity in the region. Known diversity for the deep-sea region is 1,671 species; most are narrowly
distributed and known to occur within only one sub-region. The number of species varies by sub-region and is directly
related to sampling effort occurring within each. Fishes, corals, decapod crustaceans, molluscs, and echinoderms are
relatively well known, while most other taxonomic groups are poorly known. Taxonomic diversity decreases with increasing
distance from the continental shelf and with changes in benthic topography. Low similarity in faunal composition suggests
the deep-sea region harbours faunal communities distinct from those of the continental shelf. Non-parametric estimators of
species richness suggest a minimum of 50% of the deep-sea species inventory remains to be discovered.
Conclusions/Significance: The current state of knowledge of biodiversity in this deep-sea region is rudimentary. Our ability
to answer questions is hampered by a lack of sufficient data for many taxonomic groups, which is constrained by sampling
biases, life-history characteristics of target species, and the lack of trained taxonomists
Neural circuitry at age 6 months associated with later repetitive behavior and sensory responsiveness in autism
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
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