4,321 research outputs found
Characterization of Structures of Equivalent Tissue With a Pixel Detector
Research using hybrid pixel detectors in medical physics is on the rise. Timepix detectors have arrays of 256 Ă 256 pixels with a resolution of 55 Îźm. Here, and by using Timepix counts instead of Hounsfield units, we present a calibration curve of a Timepix detector analog to those used for CT calibration. Experimentation consisted of the characterization of electron density in 10 different kinds of tissue equivalent samples from a CIRS 062M phantom (lung, 3 kinds of bones, fat, breast, muscle, water and air). Radiation of the detector was performed using an orthodontic X-ray machine at 70 KeV and .06 second of tube current with a purpose-built aluminum collimator. Data acquisition was performed at 1 frame per second and taking 3 frames per phantom. We were able to find a curve whose behavior was similar to others already published. This will lead to the verification of the usage of Timepix for identification of different tissues in an organ
Analysis of coal conversion to biomass as a transitional technology
The dominant transitional path towards a low carbon electricity industry for systems which have been heavily dependent upon coal is through its replacement by large scale wind farms and the widespread emergence of distributed solar. In this pathway, maintaining resource adequacy in the context of increased intermittency in generation has become a major concern. This paper examines this requirement to maintain resource adequacy and compare the costs and carbon impacts for new gas turbines or biomass conversions to achieve this in an expedient transitional way. This is formulated as a policy optimization in which the imperative is to replace existing coal with a renewable alternative (in this case study, wind) and to maintain the system security at the existing level, and thereby find the optimal subsidies, either as energy credits ("green certificates" or âcontracts-for-differencesâ) or capital benefits ("capacity payments" or tax
allowances). In a model of the GB system, the results show that that biomass-conversion outperforms investment in peaking gas turbines to deal with the transitional economic externality of extra reserve costs. In particular, the results suggest benefits of 10% lower costs of subsidies, 70% lower implied costs of carbon, and a reduction of 18% in wholesale power prices
IN PRAISE OF ENLIGHTENED PARTICULARITY
Autor u svojoj studiji analizira odnos opÄe kulture i njenih posebnih segmenata unutar jedinstvene politiÄke zajednice te zakljuÄuje: dok god, dakle, postoje graÄani, postojat Äe i sukob izmeÄu opÄega i posebnog, i pritom Äe se uvijek iznova pokazivati da posredovanje izmeÄu te dvije kategorije nikada nije konaÄno, nego da uvijek iznova treba odreÄivati ĹĄto je primjereno, ĹĄto je ono pravo i obvezujuÄe. U tome se oÄituje snaga prosuÄivanja kojoj su shematske orijentacije poput univerzalizma i partikularizma potrebne samo da bi se ukazalo na ono ĹĄto nedostaje, te da bi se to nadopunilo.In this study, the author analyses the relationship between general culture and its particularistic segments within the integral political community and concludes: as long as there are citizens, there will be a conflict between the general and the singular; also, the mediation between these two categories is never final; instead, one should repeatedly define what is appropriate, right and compulsory. This is the strength of the type of reasoning to which the schematic landmarks such as universalism and particularism are necessary only as reminders of what is missing in order to fill in the gaps
The 2HWC HAWC Observatory Gamma Ray Catalog
We present the first catalog of TeV gamma-ray sources realized with the
recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the
most sensitive wide field-of-view TeV telescope currently in operation, with a
1-year survey sensitivity of ~5-10% of the flux of the Crab Nebula. With an
instantaneous field of view >1.5 sr and >90% duty cycle, it continuously
surveys and monitors the sky for gamma ray energies between hundreds GeV and
tens of TeV.
HAWC is located in Mexico at a latitude of 19 degree North and was completed
in March 2015. Here, we present the 2HWC catalog, which is the result of the
first source search realized with the complete HAWC detector. Realized with 507
days of data and represents the most sensitive TeV survey to date for such a
large fraction of the sky. A total of 39 sources were detected, with an
expected contamination of 0.5 due to background fluctuation. Out of these
sources, 16 are more than one degree away from any previously reported TeV
source. The source list, including the position measurement, spectrum
measurement, and uncertainties, is reported. Seven of the detected sources may
be associated with pulsar wind nebulae, two with supernova remnants, two with
blazars, and the remaining 23 have no firm identification yet.Comment: Submitted 2017/02/09 to the Astrophysical Journa
Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory
The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been
used for the past 25 years as a reference source in TeV astronomy, for
calibration and verification of new TeV instruments. The High Altitude Water
Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe
the Crab Nebula at high significance across nearly the full spectrum of
energies to which HAWC is sensitive. HAWC is unique for its wide field-of-view,
nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC's
sensitivity improves with the gamma-ray energy. Above 1 TeV the
sensitivity is driven by the best background rejection and angular resolution
ever achieved for a wide-field ground array.
We present a time-integrated analysis of the Crab using 507 live days of HAWC
data from 2014 November to 2016 June. The spectrum of the Crab is fit to a
function of the form . The data is well-fit with values of
, , and
log when
is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the
systematic errors in this HAWC measurement is discussed and estimated to be
50\% in the photon flux between 1 and 37 TeV.
Confirmation of the Crab flux serves to establish the HAWC instrument's
sensitivity for surveys of the sky. The HAWC survey will exceed sensitivity of
current-generation observatories and open a new view of 2/3 of the sky above 10
TeV.Comment: Submitted 2017/01/06 to the Astrophysical Journa
Spectroscopic and Mechanistic Studies of Heterodimetallic Forms of Metallo-β-lactamase NDM-1
In an effort to characterize the roles of each metal ion in metallo-β-lactamase NDM-1, heterodimetallic analogues (CoCo-, ZnCo-, and CoCd-) of the enzyme were generated and characterized. UVâvis, 1H NMR, EPR, and EXAFS spectroscopies were used to confirm the fidelity of the metal substitutions, including the presence of a homogeneous, heterodimetallic cluster, with a single-atom bridge. This marks the first preparation of a metallo-β-lactamase selectively substituted with a paramagnetic metal ion, Co(II), either in the Zn1 (CoCd-NDM-1) or in the Zn2 site (ZnCo-NDM-1), as well as both (CoCo-NDM-1). We then used these metal-substituted forms of the enzyme to probe the reaction mechanism, using steady-state and stopped-flow kinetics, stopped-flow fluorescence, and rapid-freeze-quench EPR. Both metal sites show significant effects on the kinetic constants, and both paramagnetic variants (CoCd- and ZnCo-NDM-1) showed significant structural changes on reaction with substrate. These changes are discussed in terms of a minimal kinetic mechanism that incorporates all of the data
Mapping genetic determinants of host susceptibility to Pseudomonas aeruginosa lung infection in mice.
Background: P. aeruginosa is one of the top three causes of opportunistic human bacterial infections. The remarkable
variability in the clinical outcomes of this infection is thought to be associated with genetic predisposition. However,
the genes underlying host susceptibility to P. aeruginosa infection are still largely unknown.
Results: As a step towards mapping these genes, we applied a genome wide linkage analysis approach to a mouse
model. A large F2 intercross population, obtained by mating P. aeruginosa-resistant C3H/HeOuJ, and susceptible A/J
mice, was used for quantitative trait locus (QTL) mapping. The F2 progenies were challenged with a P. aeruginosa
clinical strain and monitored for the survival time up to 7 days post-infection, as a disease phenotype associated trait.
Selected phenotypic extremes of the F2 distribution were genotyped with high-density single nucleotide polymorphic
(SNP) markers, and subsequently QTL analysis was performed. A significant locus was mapped on chromosome 6 and
was named P. aeruginosa infection resistance locus 1 (Pairl1). The most promising candidate genes, including Dok1,
Tacr1, Cd207, Clec4f, Gp9, Gata2, Foxp1, are related to pathogen sensing, neutrophils and macrophages recruitment and
inflammatory processes.
Conclusions: We propose a set of genes involved in the pathogenesis of P. aeruginosa infection that may be explored
to complement human studie
Long-term follow-up of certolizumab pegol in uveitis due to immune-mediated inflammatory diseases: multicentre study of 80 patients
ObjectivesTo evaluate effectiveness and safety of certolizumab pegol (CZP) in uveitis due to immune-mediated inflammatory diseases (IMID).MethodsMulticentre study of CZP-treated patients with IMID uveitis refractory to conventional immunosuppressant. Effectiveness was assessed through the following ocular parameters: best-corrected visual acuity, anterior chamber cells, vitritis, macular thickness and retinal vasculitis. These variables were compared between the baseline, and first week, first, third, sixth months, first and second year.ResultsWe studied 80 (33 men/47 women) patients (111 affected eyes) with a mean age of 41.6 +/- 11.7 years. The IMID included were: spondyloarthritis (n=43), Behcet's disease (n=10), psoriatic arthritis (n=8), Crohn's disease (n=4), sarcoidosis (n=2), juvenile idiopathic arthritis (n=1), reactive arthritis (n=1), rheumatoid arthritis (n=1), relapsing polychondritis (n=1),ConclusionsCZP seems to be effective and safe in uveitis related to different IMID, even in patients refractory to previous biological drugs
The Polycomb Protein and E3 Ubiquitin Ligase Ring1B Harbors an IRES in its Highly Conserved 5ⲠUTR
Ring1B is an essential member of the highly conserved Polycomb group proteins, which orchestrate developmental processes, cell growth and stem cell fate by modifying local chromatin structure. Ring1B was found to be the E3 ligase that monoubiquitinates histone H2A, which adds a new level of chromatin modification to Polycomb group proteins. Here we report that Ring1B belongs to the exclusive group of proteins that for their translation depend on a stable 5ⲠUTR sequence in their mRNA known as an Internal Ribosome Entry Site (IRES). In cell transfection assays the Ring1B IRES confers significantly higher expression levels of Ring1B than a Ring1B cDNA without the IRES. Also, dual luciferase assays show strong activity of the Ring1B IRES. Although our findings indicate Ring1B can be translated under conditions where cap-dependent translation is impaired, we found the Ring1B IRES to be cap-dependent. This raises the possibility that translational control of Ring1B is a multi-layered process and that translation of Ring1B needs to be maintained under varying conditions, which is in line with its essential role as an E3 ligase for monoubiquitination of histone H2A in the PRC1 Polycomb protein complex
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