1,516 research outputs found
Analyzing redshift surveys to measure the power spectrum on large scales
Upcoming large redshift surveys potentially allow precision measurements of
the galaxy power spectrum. To accurately measure P(k) on the largest scales,
comparable to the depth of the survey, it is crucial that finite volume effects
are accurately corrected for in the data analysis. Here we derive analytic
expressions for the one such effect that has not previously been worked out
exactly: that of the so-called integral constraint. We also show that for data
analysis methods based on counts in cells, multiple constraints can be included
via simple matrix operations, thereby rendering the results less sensitive to
galactic extinction and misestimates of the shape of the radial selection
function.Comment: Mostly superseded by astro-ph/9708020; from 5/5-97. 10 pages, with 1
figure included. More detailed treatment at
http://www.sns.ias.edu/~max/galpower.html (faster from the US), from
http://www.mpa-garching.mpg.de/~max/galpower.html (faster from Europe) or
from [email protected]
18F-Fluoride Positron Emission Tomographic Imaging of Penile Arteries and Erectile Dysfunction.
BACKGROUND: Fluorine-18 sodium fluoride (NaF), a bone-seeking radiopharmaceutical used to detect osseous metastases, localizes in regions of microcalcification in atherosclerosis. OBJECTIVES: To determine if atherosclerosis of penile arteries plays a role in erectile dysfunction (ED), this study analyzed NaF images in prostate cancer patients. METHODS: NaF positron emission tomography-computed tomography bone scans were evaluated in 437 prostate cancer patients (age 66.6 ± 8.7 years). Their urologic histories were reviewed for prevalent ED (diagnosed before the scan date) or incident ED (no ED at first scan, but developed during 1-year follow-up); patients with no ED (neither before the scan nor during follow-up) were included as a control group. A semicircular region of interest was set on the dorsal one-half of the penis (to avoid residual excreted activity in the urethra) on 5 contiguous slices at the base of the penis on positron emission tomography-computed tomography coronal reconstructions, and the average standardized uptake value (SUVmax) was described as NaF uptake. RESULTS: Of 437 patients, 336 (76.9%) had prevalent ED, 60 incident ED (13.7%), and 41 had no ED (9.4%). SUVmax in patients with prevalent (median 1.88; interquartile range [IQR]: 1.67 to 2.16) or incident (median 1.86; IQR: 1.72 to 2.08) ED was significantly higher than no ED (median 1.42; IQR: 1.25 to 1.54) patients (p < 0.001). After adjustment for other risk factors, the odds ratio of prevalent or incident ED was 25.2 (95% confidence interval: 9.5 to 67.0) for every 0.5-U increment in SUVmax with receptor operating characteristic area of 0.91 (95% confidence interval: 0.88 to 0.94). CONCLUSIONS: NaF uptake in penile vessels suggests that atherosclerosis is associated with ED in prostate cancer patients. The importance of NaF uptake needs to be tested in noncancer subjects and cause-effect relationship needs to be established
Interventional suite and equipment management: cradle to grave
The acquisition process for interventional equipment and the care that this equipment receives constitute a comprehensive quality improvement program. This program strives to (a) achieve the production of good image quality that meets clinical needs, (b) reduce radiation doses to the patient and personnel to their lowest possible levels, and (c) provide overall good patient care at reduced cost. Interventional imaging equipment is only as effective and efficient as its supporting facility. The acquisition process of interventional equipment and the development of its environment demand a clinical project leader who can effectively coordinate the efforts of the many professionals who must communicate and work effectively on this type of project. The clinical project leader needs to understand (a) clinical needs of the end users, (b) how to justify the cost of the project, (c) the technical needs of the imaging and all associated equipment, (d) building and construction limitations, (e) how to effectively read construction drawings, and (f) how to negotiate and contract the imaging equipment from the appropriate vendor. After the initial commissioning of the equipment, it must not be forgotten. The capabilities designed into the imaging device can be properly utilized only by well-trained operators and staff who were initially properly trained and receive ongoing training concerning the latest clinical techniques throughout the equipment’s lifetime. A comprehensive, ongoing maintenance and repair program is paramount to reducing costly downtime of the imaging device. A planned periodic maintenance program can identify and eliminate problems with the imaging device before these problems negatively impact patient care
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Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at √s = 8 TeV
A description is provided of the performance of the CMS detector for photon reconstruction and identification in proton-proton collisions at a centre-of-mass energy of 8 TeV at the CERN LHC. Details are given on the reconstruction of photons from energy deposits in the electromagnetic calorimeter (ECAL) and the extraction of photon energy estimates. The reconstruction of electron tracks from photons that convert to electrons in the CMS tracker is also described, as is the optimization of the photon energy reconstruction and its accurate modelling in simulation, in the analysis of the Higgs boson decay into two photons. In the barrel section of the ECAL, an energy resolution of about 1% is achieved for unconverted or late-converting photons from Hγγ decays. Different photon identification methods are discussed and their corresponding selection efficiencies in data are compared with those found in simulated events
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Measurement of masses in the [Formula: see text] system by kinematic endpoints in pp collisions at [Formula: see text].
A simultaneous measurement of the top-quark, W-boson, and neutrino masses is reported for [Formula: see text] events selected in the dilepton final state from a data sample corresponding to an integrated luminosity of 5.0 fb-1 collected by the CMS experiment in pp collisions at [Formula: see text]. The analysis is based on endpoint determinations in kinematic distributions. When the neutrino and W-boson masses are constrained to their world-average values, a top-quark mass value of [Formula: see text] is obtained. When such constraints are not used, the three particle masses are obtained in a simultaneous fit. In this unconstrained mode the study serves as a test of mass determination methods that may be used in beyond standard model physics scenarios where several masses in a decay chain may be unknown and undetected particles lead to underconstrained kinematics
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Search for physics beyond the standard model in events with Ï„ leptons, jets, and large transverse momentum imbalance in pp collisions at [Formula: see text].
A search for physics beyond the standard model is performed with events having one or more hadronically decaying Ï„ leptons, highly energetic jets, and large transverse momentum imbalance. The data sample corresponds to an integrated luminosity of 4.98 fb-1 of proton-proton collisions at [Formula: see text] collected with the CMS detector at the LHC in 2011. The number of observed events is consistent with predictions for standard model processes. Lower limits on the mass of the gluino in supersymmetric models are determined
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Measurement of jet multiplicity distributions in [Formula: see text] production in pp collisions at [Formula: see text].
The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7[Formula: see text] at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0[Formula: see text]. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the [Formula: see text] production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed
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