2,773 research outputs found
Apodized pupil Lyot coronagraphs for arbitrary apertures. V. Hybrid Shaped Pupil designs for imaging Earth-like planets with future space observatories
We introduce a new class of solutions for Apodized Pupil Lyot Coronagraphs
(APLC) with segmented aperture telescopes to remove broadband diffracted light
from a star with a contrast level of . These new coronagraphs provide
a key advance to enabling direct imaging and spectroscopy of Earth twins with
future large space missions. Building on shaped pupil (SP) apodization
optimizations, our approach enables two-dimensional optimizations of the system
to address any aperture features such as central obstruction, support
structures or segment gaps. We illustrate the technique with a design that
could reach contrast level at 34\,mas for a 12\,m segmented telescope
over a 10\% bandpass centered at a wavelength 500\,nm. These
designs can be optimized specifically for the presence of a resolved star, and
in our example, for stellar angular size up to 1.1\,mas. This would allow
probing the vicinity of Sun-like stars located beyond 4.4\,pc, therefore fully
retiring this concern. If the fraction of stars with Earth-like planets is
\eta_{\Earth}=0.1, with 18\% throughput, assuming a perfect, stable wavefront
and considering photon noise only, 12.5 exo-Earth candidates could be detected
around nearby stars with this design and a 12\,m space telescope during a
five-year mission with two years dedicated to exo-Earth detection (one total
year of exposure time and another year of overheads). Our new hybrid APLC/SP
solutions represent the first numerical solution of a coronagraph based on
existing mask technologies and compatible with segmented apertures, and that
can provide contrast compatible with detecting and studying Earth-like planets
around nearby stars. They represent an important step forward towards enabling
these science goals with future large space missions.Comment: 9 pages, 6 figures, ApJ accepted on 01/04/201
Automated detection of galaxy-scale gravitational lenses in high resolution imaging data
Lens modeling is the key to successful and meaningful automated strong
galaxy-scale gravitational lens detection. We have implemented a lens-modeling
"robot" that treats every bright red galaxy (BRG) in a large imaging survey as
a potential gravitational lens system. Using a simple model optimized for
"typical" galaxy-scale lenses, we generate four assessments of model quality
that are used in an automated classification. The robot infers the lens
classification parameter H that a human would have assigned; the inference is
performed using a probability distribution generated from a human-classified
training set, including realistic simulated lenses and known false positives
drawn from the HST/EGS survey. We compute the expected purity, completeness and
rejection rate, and find that these can be optimized for a particular
application by changing the prior probability distribution for H, equivalent to
defining the robot's "character." Adopting a realistic prior based on the known
abundance of lenses, we find that a lens sample may be generated that is ~100%
pure, but only ~20% complete. This shortfall is due primarily to the
over-simplicity of the lens model. With a more optimistic robot, ~90%
completeness can be achieved while rejecting ~90% of the candidate objects. The
remaining candidates must be classified by human inspectors. We are able to
classify lens candidates by eye at a rate of a few seconds per system,
suggesting that a future 1000 square degree imaging survey containing 10^7
BRGs, and some 10^4 lenses, could be successfully, and reproducibly, searched
in a modest amount of time. [Abridged]Comment: 17 pages, 11 figures, submitted to Ap
RETROCAM: A Versatile Optical Imager for Synoptic Studies
We present RETROCAM, an auxiliary CCD camera that can be rapidly inserted
into the optical beam of the MDM 2.4m telescope. The speed and ease of
reconfiguring the telescope to use the imager and a straightforward user
interface permit the camera to be used during the course of other observing
programs. This in turn encourages RETROCAM's use for a variety of monitoring
projects.Comment: 6 pages, 6 figures, Accepted by A
Heart rate variability in insomnia patients: A critical review of the literature
Heart rate variability (HRV) is an objective marker that provides insight into autonomic nervous system dynamics. There is conflicting evidence regarding the presence of HRV impairment in insomnia patients. Web-based databases were used to systematically search the literature for all studies that compared the HRV of insomnia patients to controls or reported the HRV of insomnia patients before and after an intervention. 22 relevant papers were identified. Study characteristics were summarised, HRV measures were extracted and a risk of bias assessment for each study was performed. We were limited in our ability to synthesise outcome measures and perform meta-analyses due to considerable differences in patient (and control) selection, study protocols, measurement and processing techniques and outcome reporting. Risk of bias was deemed to be high in the majority of studies. As such, we cannot confirm that HRV is reliably impaired in insomnia patients nor determine the HRV response to interventions. Whilst HRV impairment in insomnia is a widely accepted concept, it is not supported by empirical evidence. Large longitudinal studies incorporating 24-hour recordings are required to elucidate the precise nature of HRV dynamics in insomnia patients
Computational studies of multiple-particle nonlinear dynamics in a spatio-temporally periodic potential
The spatio-temporally periodic (STP) potential is interesting in Physics due to the intimate coupling between its time and spatial components. In this paper, we begin with a brief discussion of the dynamical behaviors of a single particle in a STP potential and then examine the dynamics of multiple particles interacting in a STP potential via the electric Coulomb potential. For the multiple particles\u27 case, we focus on the occurrence of bifurcations when the amplitude of the STP potential varies. It is found that the particle concentration of the system plays an important role; the type of bifurcations that occur and the number of attractors present in the Poincaré sections depend on whether the number of particles in the simulation is even or odd. In addition to the nonlinear dynamical approach, we also discuss dependence of the squared fractional deviation of particles\u27 kinetic energy of the multiple particle system on the amplitude of the STP potential which can be used to elucidate certain transitions of states; this approach is simple and useful particularly for experimental studies of complicated interacting systems. © 2014 AIP Publishing LLC
Comparison of Direct Staffing Costs of Advanced Practice Providers and Residents in a High Acuity Area of a Community Emergency Department
Background: Resident physicians and advanced practice providers (APPs) both have roles in providing care within emergency departments (ED). While both bring unique skill sets and capabilities to the health care team, little is known about the comparative financial impact of APPs and residents in a community ED. The objective of this study was to compare direct staffing costs per relative value unit (RVU) generated of emergency medicine (EM) residents and APPs in a community ED setting.
Methods: This was a retrospective, observational analysis of RVU productivity of resident physicians and APPs in the high acuity area of a community ED. Billing data was acquired to determine RVUs generated by both APPs and residents when supervised by an attending physician. Direct costs and hours worked were used to calculate RVUs/hour and direct costs/hour. Direct cost/RVU generated were calculated for the four specific groups of providers (PGY1, PGY2, PGY3, and APP).
Results: During the study period, APPs generated 2.88 RVUs/hour. Residents generated 2.01, 3.00, and 3.49 RVUs/hour respectively from PGY1 to PGY3. When the RVU data was combined with scheduled hours and direct costs for both groups, APPs were found to cost 12.38 per RVU generated.
Conclusion: In a high acuity area of a community ED, EM residents generate more RVUs/hour than APPs after completion of their PGY1 year. Given the lower direct hourly cost of a resident compared with an APP, the direct cost of a resident to assist an attending to generate RVUs is less than that of their APP counterparts during all three years of training. This suggests that community hospitals should consider sponsoring EM residency positions over hiring APPs for use in the high acuity setting
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Influence of Acidic pH on Hydrogen and Acetate Production by an Electrosynthetic Microbiome
Production of hydrogen and organic compounds by an electrosynthetic microbiome using electrodes and carbon dioxide as sole electron donor and carbon source, respectively, was examined after exposure to acidic pH (∼5). Hydrogen production by biocathodes poised at −600 mV vs. SHE increased>100-fold and acetate production ceased at acidic pH, but ∼5–15 mM (catholyte volume)/day acetate and>1,000 mM/day hydrogen were attained at pH ∼6.5 following repeated exposure to acidic pH. Cyclic voltammetry revealed a 250 mV decrease in hydrogen overpotential and a maximum current density of 12.2 mA/cm2 at −765 mV (0.065 mA/cm2 sterile control at −800 mV) by the Acetobacterium-dominated community. Supplying −800 mV to the microbiome after repeated exposure to acidic pH resulted in up to 2.6 kg/m3/day hydrogen (≈2.6 gallons gasoline equivalent), 0.7 kg/m3/day formate, and 3.1 kg/m3/day acetate ( = 4.7 kg CO2 captured).</p
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Opportunities to encourage mail order pharmacy delivery service use for diabetes prescriptions: a qualitative study.
BackgroundMedication non-adherence is a major contributor to poor outcomes in diabetes. Previous research has shown an association between use of mail order pharmacy delivery and better medication adherence, but little is known about the barriers and facilitators to mail order pharmacy use in diabetes patients. This qualitative study examined factors related to mail order pharmacy use versus traditional "brick and mortar" pharmacies to refill prescriptions.MethodsWe conducted four 90-min focus groups in 2016 among 28 diabetes patients in the Hawaii and Northern California regions of Kaiser Permanente, a large integrated health care delivery system. We queried participants on their preferred mode for refilling prescriptions and perceived barriers and facilitators of mail order pharmacy use. One researcher independently coded each focus group transcript, with two of these transcripts double-coded by a second researcher to promote reliability. We employed thematic analysis guided by the Capability, Opportunity, Motivation, and Behavior (COM-B) framework using NVivo 11 software.ResultsA total of 28 diabetes patients participated. Participants' average age was 64.1 years; 57% were female; and racial/ethnic backgrounds included Asian/Native Hawaiian/Pacific Islander (36%), Black/African-American (21%) Hispanic/Latino (7%), and non-Hispanic White (36%). Analysis uncovered 26 themes related to the decision to use mail order pharmacy, with each theme representing a barrier or facilitator mapped to the COM-B framework. Most themes (20/26) fell into the COM-B category of 'Opportunity.' Opportunity barriers to mail order pharmacy use included unpredictability of medication delivery date, concerns about mail security, and difficulty coordinating refill orders for multiple prescriptions. In contrast, facilitators included greater access and convenience (e.g., no need to wait in line or arrange transportation) compared to traditional pharmacies. Motivational facilitators to mail order pharmacy use included receiving a pharmacy benefit plan incentive of a free one-month supply of prescriptions.ConclusionsThis study found that while patients with diabetes may benefit from mail order pharmacy use, they perceive numerous barriers to using the service. These findings will inform the design of interventions and quality improvement initiatives to increase mail order pharmacy use, which in turn may improve medication adherence and outcomes in diabetes patients, across health care systems
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