334 research outputs found
Sedation for Gastrointestinal Endoscopic Procedures in the Elderly: Getting Safer but Still Not Nearly Safe Enough
Previously published UK reports showed that excessively large doses of benzodiazepines and opiates were being commonly used to sedate elderly patients for gastrointestinal (GI) endoscopy. This unsafe practice has lead to avoidable morbidity and mortality. We have taken the opportunity provided by recent reports to examine whether GI endoscopy sedation practice in the elderly has improved in the light of this evidence and the publication of guidelines in which specific recommendations on sedation dosage are given
Network on Chip Optimization Based on Surrogate Model Assisted Evolutionary Algorithms
Network-on-Chip (NoC) design is attracting more and more attention nowadays, but there is a lack of design optimization method due to the computationally very expensive simulations of NoC. To address this problem, an algorithm, called NoC design optimization based on Gaussian process model assisted differential evolution (NDPAD), is presented. Using the surrogate model-aware evolutionary search (SMAS) framework with the tournament selection based constraint handling method, NDPAD can obtain satisfactory solutions using a limited number of expensive simulations. The evolutionary search strategies and training data selection methods are then investigated to handle integer design parameters in NoC design optimization problems. Comparison shows that comparable or even better design solutions can be obtained compared to standard EAs, and much less computation effort is needed
Harnessing optical micro-combs for microwave photonics
In the past decade, optical frequency combs generated by high-Q
micro-resonators, or micro-combs, which feature compact device footprints, high
energy efficiency, and high-repetition-rates in broad optical bandwidths, have
led to a revolution in a wide range of fields including metrology, mode-locked
lasers, telecommunications, RF photonics, spectroscopy, sensing, and quantum
optics. Among these, an application that has attracted great interest is the
use of micro-combs for RF photonics, where they offer enhanced functionalities
as well as reduced size and power consumption over other approaches. This
article reviews the recent advances in this emerging field. We provide an
overview of the main achievements that have been obtained to date, and
highlight the strong potential of micro-combs for RF photonics applications. We
also discuss some of the open challenges and limitations that need to be met
for practical applications.Comment: 32 Pages, 13 Figures, 172 Reference
Microwave and RF Applications for Micro-resonator based Frequency Combs
Photonic integrated circuits that exploit nonlinear optics in order to
generate and process signals all-optically have achieved performance far
superior to that possible electronically - particularly with respect to speed.
We review the recent achievements based in new CMOS-compatible platforms that
are better suited than SOI for nonlinear optics, focusing on radio frequency
(RF) and microwave based applications that exploit micro-resonator based
frequency combs. We highlight their potential as well as the challenges to
achieving practical solutions for many key applications. These material systems
have opened up many new capabilities such as on-chip optical frequency comb
generation and ultrafast optical pulse generation and measurement. We review
recent work on a photonic RF Hilbert transformer for broadband microwave
in-phase and quadrature-phase generation based on an integrated frequency
optical comb. The comb is generated using a nonlinear microring resonator based
on a CMOS compatible, high-index contrast, doped-silica glass platform. The
high quality and large frequency spacing of the comb enables filters with up to
20 taps, allowing us to demonstrate a quadrature filter with more than a
5-octave (3 dB) bandwidth and an almost uniform phase response.Comment: 10 pages, 6 figures, 68 references. arXiv admin note: substantial
text overlap with arXiv:1512.0174
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Controls on mangrove forest-atmosphere carbon dioxide exchanges in western Everglades National Park
We report on net ecosystem production (NEP) and key environmental controls on net ecosystem exchange (NEE) of carbon dioxide (CO2) between a mangrove forest and the atmosphere in the coastal Florida Everglades. An eddy covariance system deployed above the canopy was used to determine NEE during January 2004 through August 2005. Maximum daytime NEE ranged from â20 to â25 mmol (CO2) mâ2 sâ1 between March and May. Respiration (Rd) was highly variable (2.81 Âą 2.41 mmol (CO2) mâ2 sâ1), reaching peak values during the summer wet season. During the winter dry season, forest CO2 assimilation increased with the proportion of diffuse solar irradiance in response to greater radiative transfer in the forest canopy. Surface water salinity and tidal activity were also important controls on NEE. Daily light use efficiency was reduced at high (\u3e34 parts per thousand (ppt)) compared to low (ppt) salinity by 46%. Tidal inundation lowered daytime Rd by âź0.9 mmol (CO2) mâ2 sâ1 and nighttime Rd by âź0.5 mmol (CO2) mâ2 sâ1. The forest was a sink for atmospheric CO2, with an annual NEP of 1170 Âą 127 g C mâ2 during 2004. This unusually high NEP was attributed to yearâround productivity and low ecosystem respiration which reached a maximum of only 3 g C mâ2 dâ1. Tidal export of dissolved inorganic carbon derived from belowground respiration likely lowered the estimates of mangrove forest respiration. These results suggest that carbon balance in mangrove coastal systems will change in response to variable salinity and inundation patterns, possibly resulting from secular sea level rise and climate change. Citation: Barr, J. G., V. Engel, J. D. Fuentes
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