The Doctrine of Informed Consent: Protecting the Patient\u27s Right to Make Informed Health Care Decisions

The Doctrine of Informed Consent: Protecting the Patient\u27s Right to Make Informed Health Care Decision

Potential Diurnal Variation in Dual X-ray Absorptiometry Collected Skeletal Muscle Mass Measures: A Pilot Study

Skeletal muscle mass (SKMM) is ~30 to ~40 % of total body weight. Measuring SKMM is an important assessment for both exercise and nutritional research. There is biological variation in dual X-ray absorptiometry (DXA) estimates related to subject presentation, changes in tissue hydration, as well as GI tract contents. The consumption of water alone may increase lean mass estimates. PURPOSE: The purpose of this study is to examine how normal daily activities (e.g. eating, sleeping, exercise) may influence SKMM measures using DXA. METHODS: (Mean ± SEM; n = 8; ht: 170.2 ± 8.1 cm; wt: 70.6 ± 5.1 kg; body fat 22.7 ± 3.0 %; appendicular lean soft tissue (ALST): 24.94 ± 2.9 kg). Each participant underwent an AM (0600-0800 h) and PM (1800-2000 h) DXA (Lunar Prodigy; GE Healthcare, Madison, WI) and BIA (720; InBody, Cerriritos, CA) scan, and completed a 3-day dietary recall using Myfitnesspal. RESULTS: No differences were found between AM and PM on lean body mass (LBM; kg), ASLT (kg), SKMM (kg), body fat (kg), total body water (kg), extracellular body water (kg), and intracellular body water (kg). However, carbohydrate (CHO) and Kcal intake were different (p = .04, respectively). CONCLUSION: Currently, it appears that in college aged participants, there is minimal change in SKMM from normal daily activities between the morning and evening DXA body composition measures, which may be due to an inconsistency in daily dietary CHO intake

Signatures of synchrotron emission and of electron acceleration in the X-ray spectra of Mrk 421

BL Lac objects undergo strong flux variations involving considerable changes in their spectral shapes. We specifically investigate the X-ray spectral evolution of Mrk 421 over a time span of about nine years. We aim at statistically describing and physically understanding the large spectral changes in X rays observed in Mrk 421 over this time span. We perform a homogeneous spectral analysis of a wide data set including archived observations with ASCA, BeppoSax, RXTE, as well as published and unpublished XMM-Newton data. The presence of uncertainties is taken into account in our correlation analysis. The significance of the correlations found and possible spurious effects are studied with Monte Carlo simulations. We find that the Mrk421 spectral energy distribution (SED) has a lower peak at energies that vary in the range, 0.1-10 keV while its X-ray spectrum is definitely curved. Parameterizing the X-ray spectra with a log-parabolic model, we find a positive correlation between the position and the height of the SED peak. In addition, we find a negative trend of the spectral curvature parameter vs. the SED peak energy. We show that these relations between the spectral parameters are consistent with statistical or stochastic acceleration of the emitting particles, and provide insight into the physical processes occurring in BL Lac nuclei.Comment: 11 pages, 5 fiures, Accepted for publication in A&

The 26 year-long X-ray light curve and the X-ray spectrum of the BL Lac Object 1E 1207.9+3945 in its brightest state

We studied the temporal and spectral evolution of the synchrotron emission from the high energy peaked BL Lac object 1E 1207.9+3945. Two recent observations have been performed by the XMM-Newton and Swift satellites; we carried out X-ray spectral analysis for both of them, and photometry in optical-ultraviolet filters for the Swift one. Combining the results thus obtained with archival data we built the long-term X-ray light curve, spanning a time interval of 26 years, and the Spectral Energy Distribution (SED) of this source. The light curve shows a large flux increasing, about a factor of six, in a time interval of a few years. After reaching its maximum in coincidence with the XMM-Newton pointing in December 2000 the flux decreased in later years, as revealed by Swift. The very good statistics available in the 0.5-10 keV XMM-Newton X-ray spectrum points out a highly significant deviation from a single power law. A log-parabolic model with a best fit curvature parameter of 0.25 and a peak energy at ~1 keV describes well the spectral shape of the synchrotron emission. The simultaneous fit of Swift UVOT and XRT data provides a milder curvature (b~0.1) and a peak at higher energies (~15 keV), suggesting a different state of source activity. In both cases UVOT data support the scenario of a single synchrotron emission component extending from the optical/UV to the X-ray band. New X-ray observations are important to monitor the temporal and spectral evolution of the source; new generation gamma-ray telescopes like AGILE and GLAST could for the first time detect its inverse Compton emission.Comment: 7 pages, 6 figures, accepted for publication in A&

A fast X-ray timing capability on XEUS

Fast X-ray timing can be used to probe strong gravity fields around collapsed objects and constrain the equation of state of dense matter in neutron stars. These studies require extremely good photon statistics. In view of the huge collecting area of its mirrors, XEUS could make a unique contribution to this field. For this reason, we propose to include a fast X-ray timing capability in the focal plane of the XEUS mirrors. We briefly outline the scientific motivation for such a capability. We compute some sensitivity estimates, which indicate that XEUS could provide better than an order of magnitude sensitivity improvement over the Rossi X-ray Timing Explorer. Finally, we present a possible detector implementation, which could be an array of small size silicon drift detectors operated out of focus.Comment: 7 pages, 8 figures. To appear in the proceedings of the workshop "XEUS-studying the evolution of the hot universe" held in Garching, March 11-13, 2002, eds. G. Hasinger, Th. Boller and A. Parmar, MPE repor

A systematic look at the Very High and Low/Hard state of GX 339-4: Constraining the black hole spin with a new reflection model

We present a systematic study of GX 339-4 in both its very high and low hard states from simultaneous observations made with XMM-Newton and RXTE in 2002 and 2004. The X-ray spectra of both these extreme states exhibit strong reflection signatures, with a broad, skewed Fe-Kalpha line clearly visible above the continuum. Using a newly developed, self-consistent reflection model which implicitly includes the blackbody radiation of the disc as well as the effect of Comptonisation, blurred with a relativistic line function, we were able to infer the spin parameter of GX 339-4 to be 0.935 +/- 0.01 (statistical) +/- 0.01 (systematic) at 90 per cent confidence. We find that both states are consistent with an ionised thin accretion disc extending to the innermost stable circular orbit around the rapidly spinning black hole.Comment: 10 pages, 10 figures, accepted for publication in MNRAS 17/04/0

An XMM-Newton Study of the Hard X-ray Sky

We report on the spectral properties of a sample of 90 hard X-ray selected serendipitous sources detected in 12 XMM observations with 1<F(2-10)<80 10^(-14) erg/cm2/s. Approximately 40% of the sources are optically identified with 0.1<z<2 and most of them are classified as broad line AGNs. A simple model consisting of power law modified by Galactic absorption offers an acceptable fit to ~65% of the source spectra. This fit yields an average photon index of ~1.55 over the whole sample. We also find that the mean slope of the QSOs in our sample turns out to remain nearly constant (~1.8-1.9) between 0<z<2, with no hints of particular trends emerging along z. An additional cold absorption component with 10^(21)<Nh<10^(23) cm^(-2) is required in ~30% of the sources. Considering only subsamples that are complete in flux, we find that the observed fraction of absorbed sources (i.e. with Nh>~10^(22) cm^(-2)) is ~30%, with little evolution in the range 2<F(2-10)<80 10^(-14) erg/cm2/s. Interestingly, this value is a factor ~2 lower than predicted by the synthesis models of the CXB. This finding, detected for the first time in this survey, therefore suggests that most of the heavily obscured objects which make up the bulk of the CXB will be found at lower fluxes (F(2-10)< 10^(-14) erg/cm2/s). This mismatch together with other recent observational evidences which contrast with CXB model predictions suggest that one (or more) of the assumptions usually included in these models need to be revised.Comment: 20 pages, 13 figures, accepted for publication in A&

Swift observations of IBL and LBL objects

BL Lacs are an enigmatic class of active galactic nuclei (AGNs), characterized by the non-thermal continuum typically attributed to synchrotron and inverse Compton emission. Depending on the frequency location of the maxima of these components, they are subdivided into three subclasses LBLs, IBLs, and HBLs. We present the results of a set of observations of eight BL Lac objects of LBL and IBL type performed by the XRT and UVOT detectors onboard the Swift satellite between January 2005 and November 2006. We are mainly interested in measuring the spectral parameters, and particularly the steepness between the UV and the X-ray band, useful for determining the classification of these sources. We compare the behavior of these sources with previous XMM-Newton, BeppoSAX obser- vations and with historical data in the X-ray and in the optical band. We are also interested in classifying the sources in our sample on the basis of the observations and comparing them with their classification presented in literature. We performed X-ray spectral analysis of observed BL Lac objects using a simple powerlaw and in a few cases the log-parabolic model. We also combined the UV emission with the low energy X-ray data to We used observational data to classify sources in our sample and derived parameters of their spectral energy distribution. We found that for the IBLs X-rays low states show features of the high energy component, usually interpreted as due to inverse Compton emission. Sources in our sample exhibit a range of temporal UV and X-ray behaviors, some objects having clear and neat correlated UV and X-ray variations (e.g. ON231) and other objects showing no clear (e.g. AO 0235+164) UV and X-ray correlation. Finally, we also note that our estimates of spectral curvature are in the range of that measured for the HBLs.Comment: 10 pages, 7 figures, published in A&

A 64k pixel CMOS-DEPFET module for the soft X-rays DSSC imager operating at MHz-frame rates

: The 64k pixel DEPFET module is the key sensitive component of the DEPFET Sensor with Signal Compression (DSSC), a large area 2D hybrid detector for capturing and measuring soft X-rays at the European XFEL. The final 1-megapixel camera has to detect photons with energies between [Formula: see text] and [Formula: see text], and must provide a peak frame rate of [Formula: see text] to cope with the unique bunch structure of the European XFEL. This work summarizes the functionalities and properties of the first modules assembled with full-format CMOS-DEPFET arrays, featuring [Formula: see text] hexagonally-shaped pixels with a side length of 136&nbsp;μm. The pixel sensors utilize the DEPFET technology to realize an extremely low input capacitance for excellent energy resolution and, at the same time, an intrinsic capability of signal compression without any gain switching. Each pixel of the readout ASIC includes a DEPFET-bias current cancellation circuitry, a trapezoidal-shaping filter, a 9-bit ADC and a 800-word long digital memory. The trimming, calibration and final characterization were performed in a laboratory test-bench at DESY. All detector features are assessed at [Formula: see text]. An outstanding equivalent noise charge of [Formula: see text]e-rms is achieved at 1.1-MHz frame rate and gain of 26.8 Analog-to-Digital Unit per keV ([Formula: see text]). At [Formula: see text] and [Formula: see text], a noise of [Formula: see text] e-rms and a dynamic range of [Formula: see text] are obtained. The highest dynamic range of [Formula: see text] is reached at [Formula: see text] and [Formula: see text]. These values can fulfill the specification of the DSSC project

THE CONTROLLED DRIFT DETECTOR : CHARACTERISATION OF THE READOUT MECHANISM AND OF THE CHARGE HANDLING CAPABILITY.

A new position-sensing X-ray detector operated in integrate-readout mode has been recently designed and characterized. Due to the peculiar working principle of the new detector, the charge handling capability, that is the maximum charge that can be stored in a pixel, is related to the operating conditions of the device. In particular the amplitude of the barriers that confine the signal electrons during the integration phase depends on the applied drift field and on the field perturbation superposed to it. A detailed experimental characterization of the charge handling capability as a function of these parameters has been carried out