Preference-Adaptive Randomization in Comparative Effectiveness Studies

Background Determination of comparative effectiveness in a randomized controlled trial requires consideration of an intervention’s comparative uptake (or acceptance) among randomized participants and the intervention’s comparative efficacy among participants who use their assigned intervention. If acceptance differs across interventions, then simple randomization of participants can result in post-randomization losses that introduce bias and limit statistical power. Methods We develop a novel preference-adaptive randomization procedure in which the allocation probabilities are updated based on the inverse of the relative acceptance rates among randomized participants in each arm. In simulation studies, we determine the optimal frequency with which to update the allocation probabilities based on the number of participants randomized. We illustrate the development and application of preference-adaptive randomization using a randomized controlled trial comparing the effectiveness of different financial incentive structures on prolonged smoking cessation. Results Simulation studies indicated that preference-adaptive randomization performed best with frequent updating, accommodated differences in acceptance across arms, and performed well even if the initial values for the allocation probabilities were not equal to their true values. Updating the allocation probabilities after randomizing each participant minimized imbalances in the number of accepting participants across arms over time. In the smoking cessation trial, unexpectedly large differences in acceptance among arms required us to limit the allocation of participants to less acceptable interventions. Nonetheless, the procedure achieved equal numbers of accepting participants in the more acceptable arms, and balanced the characteristics of participants across assigned interventions. Conclusions Preference-adaptive randomization, coupled with analysis methods based on instrumental variables, can enhance the validity and generalizability of comparative effectiveness studies. In particular, preference-adaptive randomization augments statistical power by maintaining balanced sample sizes in efficacy analyses, while retaining the ability of randomization to balance covariates across arms in effectiveness analyses

The male factor: Outcomes from a cluster randomized field experiment with a couples-based HIV prevention intervention in a South African township

This study examined the effects of the Couples Health CoOp intervention on heavy drinking, condom use, and HIV incidence

BFORE: The B-mode Foreground Experiment

The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ~1/4 of the sky with 1.7 - 3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to >10,000 superconducting detectors.Comment: 7 pages, 4 figures, conference proceedings published in Journal of Low Temperature Physic

Ethical and methodological issues in engaging young people living in poverty with participatory research methods

This paper discusses the methodological and ethical issues arising from a project that focused on conducting a qualitative study using participatory techniques with children and young people living in disadvantage. The main aim of the study was to explore the impact of poverty on children and young people's access to public and private services. The paper is based on the author's perspective of the first stage of the fieldwork from the project. It discusses the ethical implications of involving children and young people in the research process, in particular issues relating to access and recruitment, the role of young people's advisory groups, use of visual data and collection of data in young people's homes. The paper also identifies some strategies for addressing the difficulties encountered in relation to each of these aspects and it considers the benefits of adopting participatory methods when conducting research with children and young people

Nuclear spin driven quantum relaxation in LiY_0.998Ho_0.002F_4

Staircase hysteresis loops of the magnetization of a LiY_0.998Ho_0.002F_4 single crystal are observed at subkelvin temperatures and low field sweep rates. This behavior results from quantum dynamics at avoided level crossings of the energy spectrum of single Ho^{3+} ions in the presence of hyperfine interactions. Enhanced quantum relaxation in constant transverse fields allows the study of the relative magnitude of tunnel splittings. At faster sweep rates, non-equilibrated spin-phonon and spin-spin transitions, mediated by weak dipolar interactions, lead to magnetization oscillations and additional steps.Comment: 5 pages, 5 eps figures, using RevTe

The balloon-borne large-aperture submillimeter telescope for polarimetry: BLAST-Pol

The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol) is a suborbital mapping experiment designed to study the role played by magnetic fields in the star formation process. BLAST-Pol is the reconstructed BLAST telescope, with the addition of linear polarization capability. Using a 1.8 m Cassegrain telescope, BLAST-Pol images the sky onto a focal plane that consists of 280 bolometric detectors in three arrays, observing simultaneously at 250, 350, and 500 um. The diffraction-limited optical system provides a resolution of 30'' at 250 um. The polarimeter consists of photolithographic polarizing grids mounted in front of each bolometer/detector array. A rotating 4 K achromatic half-wave plate provides additional polarization modulation. With its unprecedented mapping speed and resolution, BLAST-Pol will produce three-color polarization maps for a large number of molecular clouds. The instrument provides a much needed bridge in spatial coverage between larger-scale, coarse resolution surveys and narrow field of view, and high resolution observations of substructure within molecular cloud cores. The first science flight will be from McMurdo Station, Antarctica in December 2010.Comment: 14 pages, 9 figures Submitted to SPIE Astronomical Telescopes and Instrumentation Conference 201

Instrumental performance and results from testing of the BLAST-TNG receiver, submillimeter optics, and MKID arrays

Polarized thermal emission from interstellar dust grains can be used to map magnetic fields in star forming molecular clouds and the diffuse interstellar medium (ISM). The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) flew from Antarctica in 2010 and 2012 and produced degree-scale polarization maps of several nearby molecular clouds with arcminute resolution. The success of BLASTPol has motivated a next-generation instrument, BLAST-TNG, which will use more than 3000 linear polarization sensitive microwave kinetic inductance detectors (MKIDs) combined with a 2.5m diameter carbon fiber primary mirror to make diffraction-limited observations at 250, 350, and 500 $\mu$m. With 16 times the mapping speed of BLASTPol, sub-arcminute resolution, and a longer flight time, BLAST-TNG will be able to examine nearby molecular clouds and the diffuse galactic dust polarization spectrum in unprecedented detail. The 250 $\mu$m detector array has been integrated into the new cryogenic receiver, and is undergoing testing to establish the optical and polarization characteristics of the instrument. BLAST-TNG will demonstrate the effectiveness of kilo-pixel MKID arrays for applications in submillimeter astronomy. BLAST-TNG is scheduled to fly from Antarctica in December 2017 for 28 days and will be the first balloon-borne telescope to offer a quarter of the flight for "shared risk" observing by the community.Comment: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, June 29th, 201

An ALMA survey of submillimetre galaxies in the COSMOS field: The extent of the radio-emitting region revealed by 3 GHz imaging with the Very Large Array

We determine the radio size distribution of a large sample of 152 SMGs in COSMOS that were detected with ALMA at 1.3 mm. For this purpose, we used the observations taken by the VLA-COSMOS 3 GHz Large Project. One hundred and fifteen of the 152 target SMGs were found to have a 3 GHz counterpart. The median value of the major axis FWHM at 3 GHz is derived to be $4.6\pm0.4$ kpc. The radio sizes show no evolutionary trend with redshift, or difference between different galaxy morphologies. We also derived the spectral indices between 1.4 and 3 GHz, and 3 GHz brightness temperatures for the sources, and the median values were found to be $\alpha=-0.67$ and $T_{\rm B}=12.6\pm2$ K. Three of the target SMGs, which are also detected with the VLBA, show clearly higher brightness temperatures than the typical values. Although the observed radio emission appears to be predominantly powered by star formation and supernova activity, our results provide a strong indication of the presence of an AGN in the VLBA and X-ray-detected SMG AzTEC/C61. The median radio-emitting size we have derived is 1.5-3 times larger than the typical FIR dust-emitting sizes of SMGs, but similar to that of the SMGs' molecular gas component traced through mid-$J$ line emission of CO. The physical conditions of SMGs probably render the diffusion of cosmic-ray electrons inefficient, and hence an unlikely process to lead to the observed extended radio sizes. Instead, our results point towards a scenario where SMGs are driven by galaxy interactions and mergers. Besides triggering vigorous starbursts, galaxy collisions can also pull out the magnetised fluids from the interacting disks, and give rise to a taffy-like synchrotron-emitting bridge. This provides an explanation for the spatially extended radio emission of SMGs, and can also cause a deviation from the well-known IR-radio correlation.Comment: 32 pages (incl. 5 appendices), 17 figures, 7 tables; accepted for publication in A&A; abstract abridged for arXi

Response to novel objects and foraging tasks by common marmoset (Callithrix Jacchus) female Pairs

Many studies have shown that environmental enrichment can significantly improve the psychological well-being of captive primates, increasing the occurrence of explorative behavior and thus reducing boredom. The response of primates to enrichment devices may be affected by many factors such as species, sex, age, personality and social context. Environmental enrichment is particularly important for social primates living in unnatural social groupings (i.e. same-sex pairs or singly housed animals), who have very few, or no, benefits from the presence of social companions in addition to all the problems related to captivity (e.g. increased inactivity). This study analyses the effects of enrichment devices (i.e. novel objects and foraging tasks) on the behavior of common marmoset (Callithrix jacchus) female pairs, a species that usually lives in family groups. It aims to determine which aspects of an enrichment device are more likely to elicit explorative behaviors, and how aggressive and stress-related behaviors are affected by its presence. Overall, the marmosets explored foraging tasks significantly longer than novel objects. The type of object, which varied in size, shape and aural responsiveness (i.e. they made a noise when the monkey touched them), did not affect the response of the monkeys, but they explored objects that were placed higher in the enclosure more than those placed lower down.Younger monkeys were more attracted to the enrichment devices than the older ones. Finally, stress-related behavior (i.e. scratching) significantly decreased when the monkeys were presented with the objects; aggressive behavior as unaffected. This study supports the importance of environmental enrichment for captive primates and shows that in marmosets its effectiveness strongly depends upon the height of the device in the enclosure and the presence of hidden food. The findings can be explained ifone considers the foraging behavior of wild common marmosets. Broader applications for the research findings are suggested in relation to enrichment

Deep, ultra-high-resolution radio imaging of submillimetre galaxies using Very Long Baseline Interferometry

We present continent-scale VLBI - obtained with the European VLBI Network (EVN) at a wavelength of 18cm - of six distant, luminous submm-selected galaxies (SMGs). Our images have a synthesized beam width of ~30 milliarcsec FWHM - three orders of magnitude smaller in area than the highest resolution VLA imaging at this wavelength - and are capable of separating radio emission from ultra-compact radio cores (associated with active super-massive black holes - SMBHs) from that due to starburst activity. Despite targeting compact sources - as judged by earlier observations with the VLA and MERLIN - we identify ultra-compact cores in only two of our targets. This suggests that the radio emission from SMGs is produced primarily on larger scales than those probed by the EVN, and therefore is generated by star formation rather than an AGN - a result consistent with other methods used to identify the presence of SMBHs in these systems.Comment: MNRAS, in pres