1,804 research outputs found
Card sorting, test d'oculométrie et test d'utilisabilité sur le site web du Service d'information scientifique du CERN
Ce travail de Bachelor a pour objectif lâĂ©valuation du site web du Service dâinformation scientifique du CERN. Cette Ă©valuation est basĂ©e sur les mĂ©thodes utilisĂ©es en User Centered Design (UCD). Pour effectuer cette Ă©valuation, nous avons sĂ©lectionnĂ© trois tests : un card sorting, un test dâoculomĂ©trie et un test dâutilisabilitĂ©. Selon la norme ISO 9241-11 :1998, lâutilisabilitĂ© se dĂ©finit par « le degrĂ© selon lequel un produit peut ĂȘtre utilisĂ©, par des utilisateurs identifiĂ©s, pour atteindre les buts dĂ©finis avec efficacitĂ©, efficience et satisfaction, dans un contexte dâutilisation spĂ©cifiĂ© ». Les tests que nous avons rĂ©alisĂ©s nous ont permis dâidentifier les problĂšmes dâutilisabilitĂ© du site du Service, en nous appuyant sur les caractĂ©ristiques dâutilisabilitĂ© dĂ©finies dans cette norme. Pour ce faire, nous avons Ă©laborĂ© les tests en nous basant sur les pratiques utilisĂ©es par les spĂ©cialistes en UCD. Nous avons ensuite proposĂ© Ă des employĂ©s du CERN, reprĂ©sentatifs des utilisateurs du site, Ă participer aux tests. Nous avons ainsi pu rĂ©colter des donnĂ©es quantitatives et qualitatives. De plus, les commentaires des participants, obtenus avec le « think aloud » et les dĂ©briefings, nous ont apportĂ© des informations utiles sur la maniĂšre dont ils perçoivent et utilisent le site. Au terme des tests, les rĂ©sultats de ceux-ci ont Ă©tĂ© analysĂ©s individuellement. A la suite de cette analyse, nous avons Ă©laborĂ© une synthĂšse, reprenant les principaux problĂšmes dâutilisabilitĂ© identifiĂ©s pour lesquels nous proposons des amĂ©liorations. Les principaux problĂšmes observĂ©s sont liĂ©s Ă la disposition des informations sur les pages du site, notamment avec la prĂ©sence de longs textes suivis qui ne facilitent pas la lecture et lâidentification des informations essentielles. Quelques problĂšmes ont Ă©galement Ă©tĂ© identifiĂ©s dans la structure du site. Ceux-ci concernent principalement la nomenclature utilisĂ©e pour les menus et les sous-menus, ainsi que quelques titres de pages, qui prĂȘtent Ă confusion. Au vu des problĂšmes constatĂ©s, nous recommandons de diminuer la longueur des textes prĂ©sents sur les pages et de fractionner lâinformation quand cela sâavĂšre nĂ©cessaire, afin de proposer des pages plus claires et donc plus lisibles. Concernant la structure, nous proposons Ă©galement de modifier certains labels de menus et sousmenus, afin de les rendre plus explicites
Role of parathyroid hormone in the phosphaturia of extracellular fluid volume expansion
Role of parathyroid hormone in the phosphaturia of extracellular fluid volume expansion. Acute expansion of the extracellular fluid volume increases the urinary excretion of phosphate. The present study examined the importance of increased plasma parathyroid hormone concentration in the phosphaturia accompanying acute extracellular fluid volume expansion (ECVE). Infusion of a calcium-free Ringer's solution into dogs was associated with increased urinary phosphate excretion and serum immunoreactive parathyroid hormone concentration (iPTH), the latter being significantly correlated with a decrease in plasma ionized calcium concentration. Prevention of the fall in plasma ionized calcium concentration by infusion of a calcium containing Ringer's solution prevented the increase in serum iPTH but the magnitude of the phosphaturia was not affected. The phosphaturia associated with ECVE was also not affected in thyroparathyroidectomized (TPTX) dogs which received a maintenance infusion of bovine PTH. In contrast, in acutely TPTX dogs which did not receive a maintenance infusion of PTH, the phosphaturic response to ECVE was significantly depressed. These data indicate that 1) the increase in serum iPTH concentration following ECVE is the result of a fall in plasma ionized calcium concentration, 2) the increase in phosphate excretion accompanying ECVE is not dependent on an increase in serum iPTH concentration and 3) in the presence of a low or falling serum PTH concentration, the increase in phosphate excretion can be significantly blunted.RĂŽle de l'hormone parathyroĂŻdienne dans la phosphaturie consĂ©cutive Ă l'expansion extracellulaire. L'expansion aiguĂ« du volume extracellulaire augmente l'excrĂ©tion urinaire du phosphate. Ce travail examine le rĂŽle de l'augmentation de la concentration d'hormone parathyroĂŻdienne dans la phosphaturie qui accompagne l'expansion du volume extracellulaire (ECVE). L'administration Ă des chiens d'une solution de Ringer sans calcium est associĂ©e Ă une augmentation de l'excrĂ©tion urinaire de phosphate et Ă une augmentation de la concentration d'hormone parathyroĂŻdienne immunorĂ©active du plasma (iPTH). Cette derniĂšre est significativement corrĂ©lĂ©e Ă la diminution de la concentration plasmatique du calcium ionisĂ©. L'empĂȘchement de la diminution de la concentration plasmatique du calcium ionisĂ© par l'administration d'une solution de Ringer contenant du calcium Ă©vite l'augmentation de iPTH dans le plasma mais n'affecte pas l'importance de la phosphaturie. La phosphaturie associĂ©e Ă ECVE n'est pas non plus modifiĂ©e chez des chiens thyroparathyroĂŻdectomisĂ©s (TPTX) qui reçoivent une perfusion de PTH bovine. Au contraire chez des chiens TPTX aigus qui ne reçoivent pas de perfusion de PTX la rĂ©ponse Ă ECVE est significativement diminuĂ©e. Ces rĂ©sultats indiquent que 1) L'augmentation de iPTH du plasma aprĂšs ECVE est la consĂ©quence d'une diminution de la concentration plasmatique du calcium ionisĂ©, 2) l'augmentation de l'excrĂ©tion du phosphate qui accompagne ECVE ne dĂ©pend pas de l'augmentation de iPTH du plasma et 3) quand la concentration plasmatique de PTH est faible ou en voie de diminution, l'augmentation de l'excrĂ©tion de phosphate peut ĂȘtre significativement masquĂ©e
Consistent model for drain current mismatch in mosfets using the carrier number fluctuation theory
PostprintThis work presents an approach for accurate MOS transistor matching calculation. Our model, which is based on an accurate physics-based MOSFET model, allows the assessment of mismatch from process parameters and valid for any operating region. Experimental results taken on a test set of transistors implemented in a 1.2 /spl mu/m CMOS technology corroborate the theoretical development of this work
X-ray Insights into the Nature of Weak Emission-Line Quasars at High Redshift
We present Chandra observations of nine high-redshift quasars (z=2.7-5.9)
discovered by the Sloan Digital Sky Survey with weak or undetectable
high-ionization emission lines in their UV spectra (WLQs). Adding archival
X-ray observations of six additional sources of this class has enabled us to
place the strongest constraints yet on the X-ray properties of this remarkable
class of AGNs. Although our data cannot rule out the possibility that the
emission lines are overwhelmed by a relativistically boosted continuum, as
manifested by BL Lac objects, we find that WLQs are considerably weaker in the
X-ray and radio bands than the majority of BL Lacs found at much lower
redshifts. If WLQs are high-redshift BL Lacs, then it is difficult to explain
the lack of a large parent population of X-ray and radio bright weak-lined
sources at high redshift. We also consider the possibility that WLQs are
quasars with extreme properties, and in particular that the emission lines are
suppressed by high accretion rates. Using joint spectral fitting of the X-ray
spectra of 11 WLQs we find that the mean photon index in the hard X-ray band is
consistent with those observed in typical radio-quiet AGNs with no hint of an
unusually steep hard-X-ray spectrum. This result poses a challenge to the
hypothesis that WLQs have extremely high accretion rates, and we discuss
additional observations required to test this idea.Comment: 13 pages (emulateapj), 7 figures. Accepted for publication in Ap
The Infrared Luminosity of Galaxy Clusters
The aim of this study is to quantify the infrared luminosity of clusters as a
function of redshift and compare this with the X-ray luminosity. This can
potentially constrain the origin of the infrared emission to be intracluster
dust and/or dust heated by star formation in the cluster galaxies. We perform a
statistical analysis of a large sample of galaxy clusters selected from
existing databases and catalogues.We coadd the infrared IRAS and X-ray RASS
images in the direction of the selected clusters within successive redshift
intervals up to z = 1. We find that the total infrared luminosity is very high
and on average 20 times higher than the X-ray luminosity. If all the infrared
luminosity is to be attributed to emission from diffuse intracluster dust, then
the IR to X-ray ratio implies a dust-to-gas mass abundance of 5e-4. However,
the infrared luminosity shows a strong enhancement for 0.1 < z < 1, which
cannot be attributed to cluster selection effects. We show that this
enhancement is compatible with a star formation rate in the member galaxies
that is typical of the central Mpc of the Coma cluster at z = 0 and evolves
with the redshift as (1+z)^5. It is likely that most of the infrared luminosity
that we measure is generated by the ongoing star formation in the member
galaxies. From theoretical predictions calibrated on extinction measurements
(dust mass abundance equal to 1e-5), we expect only a minor contribution, of a
few percent, from intracluster dust.Comment: 9 pages, 7 figures, accepted july 31st 2008 for publication in
Astronomy and Astrophysics, language improved for this versio
Detectability of low energy X-ray spectral components in type 1 AGN
In this paper we examine the percentage of type 1 AGN which require the
inclusion of a soft excess component and/or significant cold absorption in the
modelling of their X-ray spectra obtained by XMM-Newton. We do this by
simulating spectra which mimic typical spectral shapes in order to find the
maximum detectability expected at different count levels. We then apply a
correction to the observed percentages found for the Scott et al. (2011) sample
of 761 sources. We estimate the true percentage of AGN with a soft excess
component to be 75+/-23%, suggesting that soft excesses are ubiquitous in the
X-ray spectra of type 1 AGN. By carrying out joint fits on groups of low count
spectra in narrow z bins in which additional spectral components were not
originally detected, we show that the soft excess feature is recovered with a
mean temperature kT and blackbody to power-law normalisation ratio consistent
with those of components detected in individual high count spectra. Cold
absorption with nH values broadly consistent with those reported in individual
spectra are also recovered. We suggest such intrinsic cold absorption is found
in a minimum of ~5% of type 1 AGN and may be present in up to ~10%.Comment: 10 pages, 6 figures, 4 tables. Accepted for publication in MNRA
Ablation of hepatocellular carcinoma by percutaneous ethanol injection: Imaging findings
Summary: Since PEI is a treatment based on imaging techniques, the radiologist should be familiar with the various findings that may be observed after PEI on US, CT, and MR images immediately after treatment and during later follow-up. Although US is well suited for performing PEI, contrast-enhanced CT currently is the most commonly used imaging method to evaluate the effect of PEI. Residual, nodular areas of contrast enhancement correlate well with residual tumor and warrant additional treatment. Although the findings on MR images obtained after PEI are more complex, MR imaging may be used as an alternative to C
X-ray Detection of the Primary Lens Galaxy Cluster of the Gravitational Lens System Q0957+561
Analysis of several recent ROSAT HRI observations of the gravitationally
lensed system Q0957+561 has led to the detection at the 3sigma level of the
cluster lens containing the primary galaxy G1. The total mass was estimated by
applying the equation of hydrostatic equilibrium to the detected hot
intracluster gas for a range of cluster core radii, cluster sizes and for
different values of the Hubble constant. X-ray estimates of the lensing cluster
mass provide a means to determine the cluster contribution to the deflection of
rays originating from the quasar Q0957+561. The present mass estimates were
used to evaluate the convergence parameter kappa, the ratio of the local
surface mass density of the cluster to the critical surface mass density for
lensing. The convergence parameter, kappa, calculated in the vicinity of the
lensed images, was found to range between 0.07 and 0.21, depending on the
assumed cluster core radius and cluster extent. This range of uncertainty in
kappa does not include possible systematic errors arising from the estimation
of the cluster temperature through the use of the cluster
luminosity-temperature relation and the assumption of spherical symmetry of the
cluster gas. Applying this range of values of kappa to the lensing model of
Grogin & Narayan (1996) for Q0957+561 but not accounting for uncertainties in
that model yields a range of values for the Hubble constant:67<H_0<82 km s^-1
Mpc^-1, for a time delay of 1.1 years.Comment: Accepted for publication in ApJ, 25 pages, 9 figure
The X-Ray Properties of the Optically Brightest Mini-BAL Quasars from the Sloan Digital Sky Survey
We have compiled a sample of 14 of the optically brightest radio-quiet
quasars (~~17.5 and ~~1.9) in the Sloan Digital Sky Survey
Data Release 5 quasar catalog that have C IV mini-BALs present in their
spectra. X-ray data for 12 of the objects were obtained via a Chandra snapshot
survey using ACIS-S, while data for the other two quasars were obtained from
archival XMM-Newton observations. Joint X-ray spectral analysis shows the
mini-BAL quasars have a similar average power-law photon index
() and level of intrinsic absorption () as non-BMB (neither BAL nor mini-BAL) quasars.
Mini-BAL quasars are more similar to non-BMB quasars than to BAL quasars in
their distribution of relative X-ray brightness (assessed with
). Relative colors indicate mild dust reddening in the
optical spectra of mini-BAL quasars. Significant correlations between
and UV absorption properties are confirmed for a sample
of 56 sources combining mini-BAL and BAL quasars with high signal-to-noise
ratio rest-frame UV spectra, which generally supports models in which X-ray
absorption is important in enabling driving of the UV absorption-line wind. We
also propose alternative parametrizations of the UV absorption properties of
mini-BAL and BAL quasars, which may better describe the broad absorption
troughs in some respects.Comment: ApJ accepted; 21 pages, 11 figures, and 9 table
XMM-Newton study of the lensing cluster of galaxies CL0024+17
We present a detailed gravitational mass measurement based on the XMM-Newton
imaging spectroscopy analysis of the lensing cluster of galaxies CL0024+17 at
z=0.395. The emission appears approximately symmetric. However, on the scale of
r~3.3' some indication of elongation is visible in the northwest-southeast
(NW-SE) direction from the hardness ratio map (HRM). Within 3', we measure a
global gas temperature of 3.52\pm0.17 keV, metallicity of 0.22\pm0.07, and
bolometric luminosity of 2.9\pm0.1 \times 10^{44} h^{-2}_{70} erg/s. We derive
a temperature distribution with an isothermal temperature of 3.9 keV to a
radius of 1.5' and a temperature gradient in the outskirts (1.3<r<3'). Under
the assumption of hydrostatic equilibrium, we measure gravitational mass and
gas mass fraction to be M_{200}=2.0\pm0.3 \times 10^{14} h_{70}^{-1} M_{\odot}
and f_{\rm gas}=0.20\pm0.03 h^{-3/2}_{70} at r_{200}=1.05 h^{-1}_{70} Mpc using
the observed temperature profile. The complex structure in the core region is
the key to explaining the discrepancy in gravitational mass determined from
XMM-Newton X-ray observations and HST optical lensing measurements.Comment: 16 pages, 12 figures, to appear in A&
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