1,955 research outputs found
Periods for flat algebraic connections
In previous work, we established a duality between the algebraic de Rham
cohomology of a flat algebraic connection on a smooth quasi-projective surface
over the complex numbers and the rapid decay homology of the dual connection
relying on a conjecture by C. Sabbah, which has been proved recently by T.
Mochizuki for algebraic connections in any dimension. In the present article,
we verify that Mochizuki's results allow to generalize these duality results to
arbitrary dimensions also
Thermal kinetic inductance detectors for ground-based millimeter-wave cosmology
We show measurements of thermal kinetic inductance detectors (TKID) intended
for millimeter wave cosmology in the 200-300 GHz atmospheric window. The TKID
is a type of bolometer which uses the kinetic inductance of a superconducting
resonator to measure the temperature of the thermally isolated bolometer
island. We measure bolometer thermal conductance, time constant and noise
equivalent power. We also measure the quality factor of our resonators as the
bath temperature varies to show they are limited by effects consistent with
coupling to two level systems.Comment: 8 pages, 4 figures. Submitted to Journal of Low Temperature Physic
Location Privacy in Spatial Crowdsourcing
Spatial crowdsourcing (SC) is a new platform that engages individuals in
collecting and analyzing environmental, social and other spatiotemporal
information. With SC, requesters outsource their spatiotemporal tasks to a set
of workers, who will perform the tasks by physically traveling to the tasks'
locations. This chapter identifies privacy threats toward both workers and
requesters during the two main phases of spatial crowdsourcing, tasking and
reporting. Tasking is the process of identifying which tasks should be assigned
to which workers. This process is handled by a spatial crowdsourcing server
(SC-server). The latter phase is reporting, in which workers travel to the
tasks' locations, complete the tasks and upload their reports to the SC-server.
The challenge is to enable effective and efficient tasking as well as reporting
in SC without disclosing the actual locations of workers (at least until they
agree to perform a task) and the tasks themselves (at least to workers who are
not assigned to those tasks). This chapter aims to provide an overview of the
state-of-the-art in protecting users' location privacy in spatial
crowdsourcing. We provide a comparative study of a diverse set of solutions in
terms of task publishing modes (push vs. pull), problem focuses (tasking and
reporting), threats (server, requester and worker), and underlying technical
approaches (from pseudonymity, cloaking, and perturbation to exchange-based and
encryption-based techniques). The strengths and drawbacks of the techniques are
highlighted, leading to a discussion of open problems and future work
The Design and Operation of The Keck Observatory Archive
The Infrared Processing and Analysis Center (IPAC) and the W. M. Keck
Observatory (WMKO) operate an archive for the Keck Observatory. At the end of
2013, KOA completed the ingestion of data from all eight active observatory
instruments. KOA will continue to ingest all newly obtained observations, at an
anticipated volume of 4 TB per year. The data are transmitted electronically
from WMKO to IPAC for storage and curation. Access to data is governed by a
data use policy, and approximately two-thirds of the data in the archive are
public.Comment: 12 pages, 4 figs, 4 tables. Presented at Software and
Cyberinfrastructure for Astronomy III, SPIE Astronomical Telescopes +
Instrumentation 2014. June 2014, Montreal, Canad
Photoinduced, Copper-Catalyzed Alkylation of Amides with Unactivated Secondary Alkyl Halides at Room Temperature
The development of a mild and general method for the alkylation of amides with relatively unreactive alkyl halides (i.e., poor substrates for S_N2 reactions) is an ongoing challenge in organic synthesis. We describe herein a versatile transition-metal-catalyzed approach: in particular, a photoinduced, copper-catalyzed monoalkylation of primary amides. A broad array of alkyl and aryl amides (as well as a lactam and a 2-oxazolidinone) couple with unactivated secondary (and hindered primary) alkyl bromides and iodides using a single set of comparatively simple and mild conditions: inexpensive CuI as the catalyst, no separate added ligand, and C–N bond formation at room temperature. The method is compatible with a variety of functional groups, such as an olefin, a carbamate, a thiophene, and a pyridine, and it has been applied to the synthesis of an opioid receptor antagonist. A range of mechanistic observations, including reactivity and stereochemical studies, are consistent with a coupling pathway that includes photoexcitation of a copper–amidate complex, followed by electron transfer to form an alkyl radical
Hybrid Processing Design for Multipair Massive MIMO Relaying with Channel Spatial Correlation
Massive multiple-input multiple-output (MIMO) avails of simple transceiver
design which can tackle many drawbacks of relay systems in terms of complicated
signal processing, latency, and noise amplification. However, the cost and
circuit complexity of having one radio frequency (RF) chain dedicated to each
antenna element are prohibitive in practice. In this paper, we address this
critical issue in amplify-and-forward (AF) relay systems using a hybrid analog
and digital (A/D) transceiver structure. More specifically, leveraging the
channel long-term properties, we design the analog beamformer which aims to
minimize the channel estimation error and remain invariant over a long
timescale. Then, the beamforming is completed by simple digital signal
processing, i.e., maximum ratio combining/maximum ratio transmission (MRC/MRT)
or zero-forcing (ZF) in the baseband domain. We present analytical bounds on
the achievable spectral efficiency taking into account the spatial correlation
and imperfect channel state information at the relay station. Our analytical
results reveal that the hybrid A/D structure with ZF digital processor exploits
spatial correlation and offers a higher spectral efficiency compared to the
hybrid A/D structure with MRC/MRT scheme. Our numerical results showcase that
the hybrid A/D beamforming design captures nearly 95% of the spectral
efficiency of a fully digital AF relaying topology even by removing half of the
RF chains. It is also shown that the hybrid A/D structure is robust to coarse
quantization, and even with 2-bit resolution, the system can achieve more than
93% of the spectral efficiency offered by the same hybrid A/D topology with
infinite resolution phase shifters.Comment: 17 pages, 13 figures, to appear in IEEE Transactions on
Communication
Emergency extra-intracranial bypass surgery in a patient with neurologic deficit after an accident in carotid occlusive test: A case report.
OBJECTIVE: BTO is the procedure performed to assess the collateral circulation within the Willis circle in a giant ICA aneurysm. An ICA occlusion after BTO is very rare. We present a case of an internal carotid artery occlusion as a complication of BTO that required urgent revascularization surgery.
CASE PRESENTATION: A 56-year-old female with a history of transient ischemic attacks for one year was diagnosed with multiple aneurysms: a giant aneurysm of the left supra-clinoid ICA, two small ones on left MCA and right ophthalmic. A BTO was performed to assess collateral supply and determine whether bypass surgery should be necessary. During the procedure, the balloon was detached while insufflating, and the patient had a subsequent neurological decline consistent with an MCA syndrome. EC-IC bypass surgery was performed with an end-to-side anastomosis of STA-MCA by trapping the giant aneurysm and clipping the ipsilateral MCA aneurysm. The patient had a reversal of neurological symptoms and made an uneventful recovery.
DISCUSSION: We discuss the epidemiology of giant ICA aneurysms, the indications for BTO, and its complication. Emergency intracranial and extracranial bypass surgery in case of acute ICA injury is also discussed. We also highlighted the attributable factors to treatment strategies under restrictive conditions in Vietnam.
CONCLUSIONS: ICA occlusion due to insufflated balloon detachment is an unreported complication in literature. Emergency bypass surgery is a potential treatment choice for this unusual iatrogenic complication
Knowledge, attitudes and practices of mothers and caregivers on infant and young child feeding in Peri-Urban Zones of Bobo-Dioulasso in Burkina Faso
Knowledge, attitudes and practices (KAP) of mothers/caregivers on infant and young child feeding are key factors for optimal nutritional status, health and growth of the children. A community-based, cross-sectional descriptive study was conducted duringJanuary 2017 to assess the knowledge, attitudes and practices on infant and young child feeding (IYCF) of mothers/ caregivers who lived in peri-urban areas of Bobo-Dioulasso, Burkina-Faso. This study was carried out before a nutrition education-based interventionand included 245 mothers/ caregivers that were randomly selected in the peri-urban communities of Bobo-Dioulasso. A semi-structured interviewer-administered questionnaire developed based on Food and Agriculture Organization knowledge, attitudes and practices assessment method was used to collect KAP and socio-economic data. Analyses were performed using SPSS version 20. For this study, authorization was obtained from the regional directorate of health of the Hauts-Bassins region. Verbal consent was obtained after the participants had been informed about the study objectives. Among the 245 study participants, 55.1% were aged less than 30 years. More than 3 out of 4 mothers/caregivers (76.3%) were Muslim and 59.2% of them were illiterate. Almost all mothers/caregivers (98.8%) had adequate knowledge for breastfeeding and 87.9% of them knew about exclusive breast feeding up to 6 months. In addition, 91.8% of mothers/caregivers reported that they gave colostrum at birth. Furthermore, 67.5% of the mothers started breastfeeding within one hour after delivery. Based on mothers/caregivers’ report on complementary foods consumed by 6-59 months children in the previous 24h before the interview, cereals were the most reported consumed food group (89.8%) followed by meat and fish products (28.6%). This study found that mothers/caregivers had adequate knowledge about IYCF in general. However,mothers/caregivers’ practice of complementary feeding was inappropriate. Cereals were the food group consumed by most of children aged 6-59 months raising the needs for interventions, such as cooking demonstrations during postnatal visits in health facilities, to improve complementary feeding in this population.
Key words: IYCF, knowledge, attitude, and practices; low income countries; Burkina Fas
WFPC2 Images of the Central Regions of Early-Type Galaxies - I. The Data
We present high resolution R-band images of the central regions of 67
early-type galaxies obtained with the Wide Field and Planetary Camera 2 (WFPC2)
aboard the Hubble Space Telescope (HST). Our sample strikingly confirms the
complex morphologies of the central regions of early-type galaxies. In
particular, we detect dust in 43 percent of all galaxies, and evidence for
embedded stellar disks in a remarkably large fraction of 51 percent. In 14 of
those galaxies the disk-like structures are misaligned with the main galaxy,
suggesting that they correspond to stellar bars in S0 galaxies. We analyze the
luminosity profiles of the galaxies in our sample, and classify galaxies
according to their central cusp slope. To a large extent we confirm the clear
dichotomy found in previous HST surveys: bright, boxy ellipticals with shallow
inner cusps (`core' galaxies) on one hand and faint, disky ellipticals with
steep central cusps (`power-law' galaxies) on the other hand. The advantages
and shortcomings of classification schemes utilizing the extrapolated central
cusp slope are discussed, and it is shown that this cusp slope might be an
inadequate representation for galaxies whose luminosity profile slope changes
smoothly with radius rather than resembling a broken power-law. In fact, we
find evidence for an `intermediate' class of galaxies, that cannot
unambiguously be classified as either core or power-law galaxies, and which
have central cusp slopes and absolute magnitudes intermediate between those of
core and power-law galaxies.Comment: 44 pages, 7 Postscript figures. Accepted for publication in the
Astronomical Journal. The associated Appendix with figures of luminosity
profiles, contour plots and isophotal parameters for all galaxies is
available at http://www.astro.washington.edu/rest/centralpro
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