664 research outputs found
Gamma-ray spectra of the highest energy astrophysical objects
Measurement of the spectra of multiple TeV (1012 eV) astrophysical sources has now been performed by the Whipple collaboration using a 10 meter imaging atmospheric Cherenkov telescope. These sources include the Crab Nebula and active galactic nuclei Markarian 421 and Markarian 501. Comparisons amongst sources and verification of features within spectra is now possible. The TeV energy spectra of the AGN, in particular Markarian 501, are curved. This is demonstrated with high confidence. This is consistent with other observations and with theories of emission from AGN. Possible sources of systematic error are detailed and varied spectral comparisons are performed. A softening of the spectrum of the AGN Markarian 501 is detectable at very low flux levels. However, due to the small ratio of signal to noise, this cannot be demonstrated at a high confidence
A Belgian study on the reliability and relative validity of the Health Behaviour in School-Aged Children food-frequency questionnaire
Use of Equivalent Relative Utility (ERU) to Evaluate Artificial Intelligence-Enabled Rule-Out Devices
We investigated the use of equivalent relative utility (ERU) to evaluate the
effectiveness of artificial intelligence (AI)-enabled rule-out devices that use
AI to identify and autonomously remove non-cancer patient images from
radiologist review in screening mammography.We reviewed two performance metrics
that can be used to compare the diagnostic performance between the
radiologist-with-rule-out-device and radiologist-without-device workflows:
positive/negative predictive values (PPV/NPV) and equivalent relative utility
(ERU). To demonstrate the use of the two evaluation metrics, we applied both
methods to a recent US-based study that reported an improved performance of the
radiologist-with-device workflow compared to the one without the device by
retrospectively applying their AI algorithm to a large mammography dataset. We
further applied the ERU method to a European study utilizing their reported
recall rates and cancer detection rates at different thresholds of their AI
algorithm to compare the potential utility among different thresholds. For the
study using US data, neither the PPV/NPV nor the ERU method can conclude a
significant improvement in diagnostic performance for any of the algorithm
thresholds reported. For the study using European data, ERU values at lower AI
thresholds are found to be higher than that at a higher threshold because more
false-negative cases would be ruled-out at higher threshold, reducing the
overall diagnostic performance. Both PPV/NPV and ERU methods can be used to
compare the diagnostic performance between the radiologist-with-device workflow
and that without. One limitation of the ERU method is the need to measure the
baseline, standard-of-care relative utility (RU) value for mammography
screening in the US. Once the baseline value is known, the ERU method can be
applied to large US datasets without knowing the true prevalence of the
dataset
Urinalysis and Urinary Tract Infection: Update for Clinicians
Dysuria is a common presenting complaint of women and urinalysis is a valuable tool in the initial evaluation of this presentation. Clinicians need to be aware that pyuria is the best determinate of bacteriuria requiring therapy and that values significant for infection differ depending on the method of analysis. A hemocytometer yields a value of â„ 10 WBC/ mm(3) significant for bacteriuria, while manual microscopy studies show â„ 8 WBC/high-power field reliably predicts a positive urine culture. In cases of uncomplicated symptomatic urinary tract infection, a positive value for nitrites and leukocyte esterase by urine dipstick can be treated without the need for a urine culture. Automated urinalysis used widely in large volume laboratories provides more sensitive detection of leukocytes and bacteria in the urine.With automated microscopy, a value of > 2 WBC/hpf is significant pyuria indicative of inflammation of the urinary tract. In complicated cases such as pregnancy, recurrent infection or renal involvement, further evaluation is necessary including manual microscopy and urine culture with sensitivities
New Generation Atmospheric Cherenkov Detectors
High energy gamma-ray astronomy has been established during the last decade
through the launch of the Compton Gamma Ray Observatory (CGRO) and the success
of its ground-based counterpart, the imaging atmospheric Cherenkov technique.
In the aftermath of their important and surprising scientific results a
worldwide effort developing and designing new generation atmospheric Cherenkov
detectors is underway. These novel instruments will have higher sensitivity at
E > 250 GeV, but most importantly, will be able to close the unexplored energy
gap between 20 GeV and 250 GeV. Several ground-based detectors are proposed or
under construction. Aspects of the techniques used and sensitivity are
discussed in this overview paper. The instruments cover largely complementary
energy ranges and together are expected to explore the gamma-ray sky between 20
GeV and 100 TeV with unprecedented sensitivity.Comment: 13 pages, 4 Figures, Invited talk at the VERITAS Workshop on TeV
Astrophysics of Extragalactic Sources, eds. M. Catanese and T. Weekes, to be
published in Astroparticle Physic
Relativity, rank and the utility of income
This is the accepted version of the following article: Rablen, M. D. (2008), Relativity, Rank and the Utility of Income. The Economic Journal, 118: 801â821, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/j.1468-0297.2008.02143.x/abstract.Relative utility has become an important concept in several disjoint areas of economics. I present a cardinal model of income utility based on the supposition that agents care about their rank in the income distribution and that utility is subject to adaptation over time. Utility levels correspond to the Leyden Individual Welfare Function while utility differences yield a version of the prospect theory value function, thereby providing a new and shared derivation of each. I offer an explanation of some long-standing paradoxes in the wellbeing literature and an insight into the links between relative comparisons and loss aversion.ESR
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Identifying Motor, Emotional-Behavioral, and Cognitive Deficits that Comprise the Triad of HD Symptoms from Patient, Caregiver, and Provider Perspectives
Background: The objective of this study was to identify important attributes associated with the triad of symptoms (cognition, emotionalâbehavioral, and motor) of Huntington's disease (HD) from patient, caregiver, and medical provider perspectives to facilitate development of a new diseaseâspecific, healthârelated quality of life (HRQOL) instrument.
Methods: We conducted a targeted literature review of HD and HRQOL instruments, expert surveys, and patient and caregiver phoneâbased interviews to extract information on the symptoms and issues most relevant to the HD symptom triad (HD triad). The data collected from these sources were used to generate themes and subdomains and to develop an integrated schema that highlights the key dimensions of the triad.
Results: The search identified the following areas: emotional functioning/behavioral changes (e.g., positive emotions, sadness/depression); cognitive functioning (e.g., memory/learning, attention/comprehension); physical functioning (e.g., motor functioning, medication); social functioning (e.g., leisure, interpersonal relationships); endâofâlife concerns/planning; and gene testing. Fifteen individuals diagnosed with HD and 16 HD caregivers, recruited from several Huntington's Disease Society of America support group networks, completed phone interviews. Nineteen US medical providers who specialize in HD completed the online survey. Twentyâsix subdomains of the HD symptom triad (seven cognition, 12 emotionalâbehavioral, and seven motor) emerged relatively consistently across patient, caregiver, and provider samples. These included movements/chorea, memory impairment, depression, and anxiety.
Discussion: Based on an integrated, mixedâmethods approach, important HD triad symptom were identified and organized into a guiding schema. These patientâ, caregiverâ, and providerâtriangulated data served as the basis for development of a HDâspecific HRQOL instrument, the HDâPROâTRIADâą
On reminder effects, drop-outs and dominance: evidence from an online experiment on charitable giving
We present the results of an experiment that (a) shows the usefulness of screening out drop-outs and (b) tests whether different methods of payment and reminder intervals affect charitable giving. Following a lab session, participants could make online donations to charity for a total duration of three months. Our procedure justifying the exclusion of drop-outs consists in requiring participants to collect payments in person flexibly and as known in advance and as highlighted to them later. Our interpretation is that participants who failed to collect their positive payments under these circumstances are likely not to satisfy dominance. If we restrict the sample to subjects who did not drop out, but not otherwise, reminders significantly increase the overall amount of charitable giving. We also find that weekly reminders are no more effective than monthly reminders in increasing charitable giving, and that, in our three months duration experiment, standing orders do not increase giving relative to one-off donations
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