37,977 research outputs found
Coordinated Multicasting with Opportunistic User Selection in Multicell Wireless Systems
Physical layer multicasting with opportunistic user selection (OUS) is
examined for multicell multi-antenna wireless systems. By adopting a two-layer
encoding scheme, a rate-adaptive channel code is applied in each fading block
to enable successful decoding by a chosen subset of users (which varies over
different blocks) and an application layer erasure code is employed across
multiple blocks to ensure that every user is able to recover the message after
decoding successfully in a sufficient number of blocks. The transmit signal and
code-rate in each block determine opportunistically the subset of users that
are able to successfully decode and can be chosen to maximize the long-term
multicast efficiency. The employment of OUS not only helps avoid
rate-limitations caused by the user with the worst channel, but also helps
coordinate interference among different cells and multicast groups. In this
work, efficient algorithms are proposed for the design of the transmit
covariance matrices, the physical layer code-rates, and the target user subsets
in each block. In the single group scenario, the system parameters are
determined by maximizing the group-rate, defined as the physical layer
code-rate times the fraction of users that can successfully decode in each
block. In the multi-group scenario, the system parameters are determined by
considering a group-rate balancing optimization problem, which is solved by a
successive convex approximation (SCA) approach. To further reduce the feedback
overhead, we also consider the case where only part of the users feed back
their channel vectors in each block and propose a design based on the balancing
of the expected group-rates. In addition to SCA, a sample average approximation
technique is also introduced to handle the probabilistic terms arising in this
problem. The effectiveness of the proposed schemes is demonstrated by computer
simulations.Comment: Accepted by IEEE Transactions on Signal Processin
Characteristics, Mortality, and Outcome of Infants Weighing Over 2500 Grams Who Require Intensive Care
Documentations of morbidity and mortality of infants weighing over 2500 g who require intensive care, along with research to improve their outcome, have not received adequate emphasis in the literature. From 1981 to 1984 these infants accounted for 495 (40.1%) admissions and 16 (9.8%) deaths in Henry Ford Hospital\u27s neonatal intensive care unit. The most common diagnoses were hematologic diseases (24.6%), meconium aspiration (20.4%), respiratory distress/asphyxia (17.2%), congenital anomalies (13.8%), and infants of diabetic mothers (10.7%). Infant mortality was 56.2% from congenital anomalies. 25% from meconium aspiration, 6.2% from infection, 6.2% from maternal accident, and 6.2% from accidental neonatal asphyxia. About 44% of the deaths were potentially preventable. Investigative studies are recommended to improve the outcome of higher birth weight infants who require intensive care
On the Insignificance of Photochemical Hydrocarbon Aerosols in the Atmospheres of Close-in Extrasolar Giant Planets
The close-in extrasolar giant planets (CEGPs) reside in irradiated
environments much more intense than that of the giant planets in our solar
system. The high UV irradiance strongly influences their photochemistry and the
general current view believed that this high UV flux will greatly enhance
photochemical production of hydrocarbon aerosols. In this letter, we
investigate hydrocarbon aerosol formation in the atmospheres of CEGPs. We find
that the abundances of hydrocarbons in the atmospheres of CEGPs are
significantly less than that of Jupiter except for models in which the CH
abundance is unreasonably high (as high as CO) for the hot (effective
temperatures K) atmospheres. Moreover, the hydrocarbons will be
condensed out to form aerosols only when the temperature-pressure profiles of
the species intersect with the saturation profiles--a case almost certainly not
realized in the hot CEGPs atmospheres. Hence our models show that photochemical
hydrocarbon aerosols are insignificant in the atmospheres of CEGPs. In
contrast, Jupiter and Saturn have a much higher abundance of hydrocarbon
aerosols in their atmospheres which are responsible for strong absorption
shortward of 600 nm. Thus the insignificance of photochemical hydrocarbon
aerosols in the atmospheres of CEGPs rules out one class of models with low
albedos and featureless spectra shortward of 600 nm.Comment: ApJL accepte
Larkin-Ovchinnikov-Fulde-Ferrell phase in the superconductor (TMTSF)2ClO4: Theory versus experiment
We consider a formation of the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase
in a quasi-one-dimensional (Q1D) conductor in a magnetic field, parallel to its
conducting chains, where we take into account both the paramagnetic
spin-splitting and orbital destructive effects against superconductivity. We
show that, due to a relative weakness of the orbital effects in a Q1D case, the
LOFF phase appears in (TMTSF)ClO superconductor for real values of its
Q1D band parameters. We compare our theoretical calculations with the recent
experimental data by Y. Maeno's group [S. Yonezawa et al., Phys. Rev. Lett.
\textbf{100}, 117002 (2008)] and show that there is a good qualitative and
quantitative agreement between the theory and experimental data.Comment: 4 pages, 1 figur
Manipulation of External Tachodynamometer by the Patient: Case Report
External tachodynamometer has frequently been used to evaluate premature labor. In three cases, the patient was apparently able to record uterine contraction-like curves by means of abdominal pressure. In two of these cases, the patient was evidently using this manipulation to gain attention and support from her husband and/or family members. In the third case, described in this paper, because false curves were recorded, an emergency Caesarean section was performed under the impression that abruptio placenta had occurred
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