897 research outputs found
Municipal Diverging from “Bureaucracy:” A Case Study of Organizational Image in Housing Services
This article presents a case study of efforts of a workforce development unit within a local public housing authority to recraft its image as separate from the larger housing authority, in order to better attract participants to its optional supportive services. Using qualitative interview data with Section 8 voucher recipients and public housing authority staff, and descriptive quantitative data from a larger dataset, and drawing on theories of street-level bureaucracies and agency-client interactions, the case study finds that service recipients perceive the housing authority as a largely compliance-oriented organization that is overly bureaucratic, excessively regulating of private spheres of family life, and highly punitive. In order to attract participants to its optional supportive services, the workforce development unit recrafted its organizational identity and its external image through spatial relocation, rebranding, reallocation of workload among staff, and program redesign. The result is a workforce development unit that is highly valued and attractive to service participants, and that service seekers view as distinct from the housing authority within which the unit resides
HIV Suppression among Patients on Treatment in Vietnam: A Review of HIV Viral Load Testing in a Public Urban Clinic in Ho Chi Minh City
Background. There are few reports of HIV viral load (VL) testing among patients on ART in Vietnam. Methods. From a public clinic in Ho Chi Minh City (HCMC), we reviewed cases of VL measurements from adults on ART. Results. We identified 228 cases. Median age was 30 years (27–34), 85% were male, and 77% had a history of IDU. The mean ART duration was 26 months (95% CI 25–27); d4T/3TC/NVP was the most common regimen. Viral suppression was seen in 160/228 (70%). Viremia (>1000 copies/mL) was associated with prior ART exposure (OR 5.68, P < .0001) and immunologic failure (OR 4.69, P = .0001). Targeted testing accounted for 13% of cases, only half of which yielded viremia. Conclusion. We demonstrate a high HIV suppression rate among patients on ART in HCMC, Vietnam. In this setting, routine testing detects viremia missed by targeted testing
Agritourism around the globe: Definitions, authenticity, and potential controversy
This commentary identifies the variability in definitions of agritourism that exists in a variety of different countries, discusses reasons why this variability might produce problems, and provides examples of efforts to harmonize these definitions, including an ongoing international dialogue on the topic
A Titanium Nitride Absorber for Controlling Optical Crosstalk in Horn-Coupled Aluminum LEKID Arrays for Millimeter Wavelengths
We discuss the design and measured performance of a titanium nitride (TiN)
mesh absorber we are developing for controlling optical crosstalk in
horn-coupled lumped-element kinetic inductance detector arrays for
millimeter-wavelengths. This absorber was added to the fused silica
anti-reflection coating attached to previously-characterized, 20-element
prototype arrays of LEKIDs fabricated from thin-film aluminum on silicon
substrates. To test the TiN crosstalk absorber, we compared the measured
response and noise properties of LEKID arrays with and without the TiN mesh.
For this test, the LEKIDs were illuminated with an adjustable, incoherent
electronic millimeter-wave source. Our measurements show that the optical
crosstalk in the LEKID array with the TiN absorber is reduced by 66\% on
average, so the approach is effective and a viable candidate for future
kilo-pixel arrays.Comment: 7 pages, 5 figures, accepted for publication in the Journal of Low
Temperature Physic
Horn-Coupled, Commercially-Fabricated Aluminum Lumped-Element Kinetic Inductance Detectors for Millimeter Wavelengths
We discuss the design, fabrication, and testing of prototype horn-coupled,
lumped-element kinetic inductance detectors (LEKIDs) designed for cosmic
microwave background (CMB) studies. The LEKIDs are made from a thin aluminum
film deposited on a silicon wafer and patterned using standard
photolithographic techniques at STAR Cryoelectronics, a commercial device
foundry. We fabricated twenty-element arrays, optimized for a spectral band
centered on 150 GHz, to test the sensitivity and yield of the devices as well
as the multiplexing scheme. We characterized the detectors in two
configurations. First, the detectors were tested in a dark environment with the
horn apertures covered, and second, the horn apertures were pointed towards a
beam-filling cryogenic blackbody load. These tests show that the multiplexing
scheme is robust and scalable, the yield across multiple LEKID arrays is 91%,
and the noise-equivalent temperatures (NET) for a 4 K optical load are in the
range 26\thinspace\pm6 \thinspace \mu \mbox{K} \sqrt{\mbox{s}}
The Detector System for the Stratospheric Kinetic Inductance Polarimeter (SKIP)
The Stratospheric Kinetic Inductance Polarimeter (SKIP) is a proposed
balloon-borne experiment designed to study the cosmic microwave background, the
cosmic infrared background and Galactic dust emission by observing 1133 square
degrees of sky in the Northern Hemisphere with launches from Kiruna, Sweden.
The instrument contains 2317 single-polarization, horn-coupled, aluminum
lumped-element kinetic inductance detectors (LEKID). The LEKIDs will be
maintained at 100 mK with an adiabatic demagnetization refrigerator. The
polarimeter operates in two configurations, one sensitive to a spectral band
centered on 150 GHz and the other sensitive to 260 and 350 GHz bands. The
detector readout system is based on the ROACH-1 board, and the detectors will
be biased below 300 MHz. The detector array is fed by an F/2.4 crossed-Dragone
telescope with a 500 mm aperture yielding a 15 arcmin FWHM beam at 150 GHz. To
minimize detector loading and maximize sensitivity, the entire optical system
will be cooled to 1 K. Linearly polarized sky signals will be modulated with a
metal-mesh half-wave plate that is mounted at the telescope aperture and
rotated by a superconducting magnetic bearing. The observation program consists
of at least two, five-day flights beginning with the 150 GHz observations.Comment: J Low Temp Phys DOI 10.1007/s10909-013-1014-3 The final publication
is available at link.springer.co
The new generation CMB B-mode polarization experiment: POLARBEAR
We describe the Cosmic Microwave Background (CMB) polarization experiment
called Polarbear. This experiment will use the dedicated Huan Tran Telescope
equipped with a powerful 1,200-bolometer array receiver to map the CMB
polarization with unprecedented accuracy. We summarize the experiment, its
goals, and current status
A LEKID-based CMB instrument design for large-scale observations in Greenland
We present the results of a feasibility study, which examined deployment of a
ground-based millimeter-wave polarimeter, tailored for observing the cosmic
microwave background (CMB), to Isi Station in Greenland. The instrument for
this study is based on lumped-element kinetic inductance detectors (LEKIDs) and
an F/2.4 catoptric, crossed-Dragone telescope with a 500 mm aperture. The
telescope is mounted inside the receiver and cooled to K by a
closed-cycle He refrigerator to reduce background loading on the detectors.
Linearly polarized signals from the sky are modulated with a metal-mesh
half-wave plate that is rotated at the aperture stop of the telescope with a
hollow-shaft motor based on a superconducting magnetic bearing. The modular
detector array design includes at least 2300 LEKIDs, and it can be configured
for spectral bands centered on 150~GHz or greater. Our study considered
configurations for observing in spectral bands centered on 150, 210 and
267~GHz. The entire polarimeter is mounted on a commercial precision rotary air
bearing, which allows fast azimuth scan speeds with negligible vibration and
mechanical wear over time. A slip ring provides power to the instrument,
enabling circular scans (360 degrees of continuous rotation). This mount, when
combined with sky rotation and the latitude of the observation site, produces a
hypotrochoid scan pattern, which yields excellent cross-linking and enables
34\% of the sky to be observed using a range of constant elevation scans. This
scan pattern and sky coverage combined with the beam size (15~arcmin at
150~GHz) makes the instrument sensitive to in the angular
power spectra
Spatially-resolved decoherence of donor spins in silicon strained by a metallic electrode
Electron spins are amongst the most coherent solid-state systems known,
however, to be used in devices for quantum sensing and information processing
applications, they must be typically placed near interfaces. Understanding and
mitigating the impacts of such interfaces on the coherence and spectral
properties of electron spins is critical to realize such applications, but is
also challenging: inferring such data from single-spin studies requires many
measurements to obtain meaningful results, while ensemble measurements
typically give averaged results that hide critical information. Here, we report
a comprehensive study of the coherence of near-surface bismuth donor spins in
28-silicon at millikelvin temperatures. In particular, we use strain-induced
frequency shifts caused by a metallic electrode to make spatial maps of spin
coherence as a function of depth and position relative to the electrode. By
measuring magnetic-field-insensitive clock transitions we separate magnetic
noise caused by surface spins from charge noise. Our results include
quantitative models of the strain-split spin resonance spectra and extraction
of paramagnetic impurity concentrations at the silicon surface. The interplay
of these decoherence mechanisms for such near-surface electron spins is
critical for their application in quantum technologies, while the combination
of the strain splitting and clock transition extends the coherence lifetimes by
up to two orders of magnitude, reaching up to 300 ms at a mean depth of only
100nm. The technique we introduce here to spatially map coherence in
near-surface ensembles is directly applicable to other spin systems of active
interest, such as defects in diamond, silicon carbide, and rare earth ions in
optical crystals.Comment: 16 pages, 11 figure
The bolometric focal plane array of the Polarbear CMB experiment
The Polarbear Cosmic Microwave Background (CMB) polarization experiment is
currently observing from the Atacama Desert in Northern Chile. It will
characterize the expected B-mode polarization due to gravitational lensing of
the CMB, and search for the possible B-mode signature of inflationary
gravitational waves. Its 250 mK focal plane detector array consists of 1,274
polarization-sensitive antenna-coupled bolometers, each with an associated
lithographed band-defining filter. Each detector's planar antenna structure is
coupled to the telescope's optical system through a contacting dielectric
lenslet, an architecture unique in current CMB experiments. We present the
initial characterization of this focal plane
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