676 research outputs found
Sub-mm counterparts to Lyman-break galaxies
We summarize the main results from our SCUBA survey of Lyman-break galaxies
(LBGs) at z~3. Analysis of our sample of LBGs reveals a mean flux of
S850=0.60.2 mJy, while simple models of emission based on the UV
properties predict a mean flux about twice as large. Known populations of LBGs
are expected to contribute flux to the weak sub-mm source portion of the far-IR
background, but are not likely to comprise the bright source (S850>5 mJy) end
of the SCUBA-detected source count. The detection of the LBG, Westphal-MM8, at
1.9 mJy suggests that deeper observations of individual LBGs in our sample
could uncover detections at similar levels, consistent with our UV-based
predictions. By the same token, many sub-mm selected sources with S850<2 mJy
could be LBGs. The data are also consistent with the FarIR/ relation
holding at z=3.Comment: 6 pages, 1 figure, contributed talk at UMass/INAOE Conference ``Deep
Millimeter Surveys'
A study of the Sunyaev-Zel'dovich increment using archival SCUBA data
In a search for evidence of the short wavelength increment in the
Sunyaev-Zel'dovich (SZ) effect, we have analyzed archival galaxy cluster data
from the Sub-millimetre Common User Bolometer Array (SCUBA) on the James Clerk
Maxwell Telescope, resulting in the most complete pointed survey of clusters at
850 microns to date. SCUBA's 850 microns passband overlaps the peak of the SZ
increment. The sample consists of 44 galaxy clusters in the range 0 < z < 1.3.
Maps of each of the clusters have been made and sources have been extracted; as
an ancillary product we generate the most thorough galaxy cluster point source
list yet from SCUBA. Seventeen of these clusters are free of obvious AGN and
have data deep enough to provide interesting measurements of the expected SZ
signal. Specialized analysis techniques are employed to extract the SZ effect
signal from these SCUBA data, including using SCUBA's short wavelength band as
an atmospheric monitor and fitting the long wavelength channel to a model of
the spatial distribution of each cluster's SZ effect. By explicitly excising
the exact cluster centre from our analysis we demonstrate that emission from
galaxies within the cluster does not contaminate our measurement. The SZ
amplitudes from our measurements are consistently higher than the amplitudes
inferred from low frequency measurements of the SZ decrement.Comment: 27 pages, 6 figures, replacement matches version published in MNRA
Solid-Organ Transplantation in HIV-Infected Patients
Before the introduction of highly active antiretroviral therapy in the mid-1990s, transplantation centers were understandably reluctant to provide scarce solid organs for patients infected with the human immunodeficiency virus (HIV). However, because treated patients can now expect to live substantially longer than before, many will have end-stage organ disease long before they have life-threatening conditions related to HIV infection. It is therefore time for the transplantation community to readdress the safety, efficacy, and propriety of transplanting scarce organs in HIV-positive patients who need them.
In this article, we provide ethical arguments for viewing transplantation in patients with HIV infection as analogous to transplantation in patients with other chronic illnesses. Accordingly, transplantation in HIV-positive patients should be initiated at major centers and should not be considered experimental. In addition, reimbursement for such procedures should be similar to that for transplantation in other patients, unless evidence accumulates that HIV-infected transplant recipients fare poorly
Re-examining ethical obligations in the intensive care unit: HIV disclosure to surrogates
Physicians treating newly incapacitated patients often must help navigate surrogate decision-makers through a difficult course of treatment decisions, while safeguarding the patient's autonomy. We offer guidance for intensive care physicians who must frequently address the difficult questions concerning disclosure of confidential information to surrogates. Three clinical vignettes will highlight the ethical challenges to physician disclosure of a critically ill patient's HIV status. Two key distinctions are offered that influence the propriety of disclosure: first, whether HIV infection represents a 'primary cause' for the patient's critical illness; and second, whether the surrogate may be harmed by failure to disclose HIV status. This balanced consideration of the direct duties of physicians to patients, and their indirect duties to surrogates and third-party contacts, may be used as a framework for considering other ethical obligations in the intensive care unit. We also provide a tabulation of individual US state laws relevant to disclosure of HIV status
Assessing treatment effect heterogeneity in the presence of missing effect modifier data in cluster-randomized trials
Understanding whether and how treatment effects vary across subgroups is
crucial to inform clinical practice and recommendations. Accordingly, the
assessment of heterogeneous treatment effects (HTE) based on pre-specified
potential effect modifiers has become a common goal in modern randomized
trials. However, when one or more potential effect modifiers are missing,
complete-case analysis may lead to bias and under-coverage. While statistical
methods for handling missing data have been proposed and compared for
individually randomized trials with missing effect modifier data, few
guidelines exist for the cluster-randomized setting, where intracluster
correlations in the effect modifiers, outcomes, or even missingness mechanisms
may introduce further threats to accurate assessment of HTE. In this article,
the performance of several missing data methods are compared through a
simulation study of cluster-randomized trials with continuous outcome and
missing binary effect modifier data, and further illustrated using real data
from the Work, Family, and Health Study. Our results suggest that multilevel
multiple imputation (MMI) and Bayesian MMI have better performance than other
available methods, and that Bayesian MMI has lower bias and closer to nominal
coverage than standard MMI when there are model specification or compatibility
issues
Breaking the Redshift Deadlock - I: Constraining the star formation history of galaxies with sub-millimetre photometric redshifts
Future extragalactic sub-millimetre and millimetre surveys have the potential
to provide a sensitive census of the level of obscured star formation in
galaxies at all redshifts. While in general there is good agreement between the
source counts from existing SCUBA (850um) and MAMBO (1.25mm) surveys of
different depths and areas, it remains difficult to determine the redshift
distribution and bolometric luminosities of the sub-millimetre and millimetre
galaxy population. This is principally due to the ambiguity in identifying an
individual sub-millimetre source with its optical, IR or radio counterpart
which, in turn, prevents a confident measurement of the spectroscopic redshift.
Additionally, the lack of data measuring the rest-frame FIR spectral peak of
the sub-millimetre galaxies gives rise to poor constraints on their rest-frame
FIR luminosities and star formation rates. In this paper we describe
Monte-Carlo simulations of ground-based, balloon-borne and satellite
sub-millimetre surveys that demonstrate how the rest-frame FIR-sub-millimetre
spectral energy distributions (250-850um) can be used to derive photometric
redshifts with an r.m.s accuracy of +/- 0.4 over the range 0 < z < 6. This
opportunity to break the redshift deadlock will provide an estimate of the
global star formation history for luminous optically-obscured galaxies [L(FIR)
> 3 x 10^12 Lsun] with an accuracy of 20 per cent.Comment: 14 pages, 22 figures, submitted to MNRAS, replaced with accepted
versio
Evaluating the Economic Impact of Palliative and End-of-Life Care Interventions on Intensive Care Unit Utilization and Costs from the Hospital and Healthcare System Perspective.
Purpose of report: Understanding the impact of palliative care interventions on intensive care unit (ICU) costs and utilization is critical for demonstrating the value of palliative care. Performing these economic assessments, however, can be challenging. The purpose of this special report is to highlight and discuss important considerations when assessing ICU utilization and costs from the hospital perspective, with the goal of providing recommendations on methods to consider for future analyses.
FINDINGS: ICU length of stay (LOS) and associated costs of care are common and important outcome measures, but must be analyzed properly to yield valid conclusions. There is significant variation in costs by day of stay in the ICU with only modest differences between an ICU day at the end of a stay and the first day on the acute care floor; this variation must be appropriately accounted for analytically. Furthermore, reporting direct variable costs, in addition to total ICU costs, is needed to understand short-term and long-term impact of a reduction in LOS. Importantly, incentives for the hospital to realize savings vary depending on reimbursement policies.
SUMMARY: ICU utilization and costs are common outcomes in studies evaluating palliative care interventions. Accurate estimation and interpretation are key to understanding the economic implications of palliative care interventions
A Pragmatic Trial of E-Cigarettes, Incentives, and Drugs for Smoking Cessation
In a trial examining five approaches to smoking cessation among over 6,000 U.S. employees, financial incentives combined with free cessation aids were more effective at getting employees to stop smoking than free cessation aids alone. Specifically, the most effective intervention (free cessation aids plus $600 in redeemable funds) helped 2.9% of participants stop smoking through six months after their target quit date; this rate jumped to 12.7% among participants who actively engaged in the trial and were more motivated to quit. For employees with access to usual care (information and a free motivational text messaging service), offering free cessation aids or electronic cigarettes (e-cigarettes) did not help them quit smoking
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