600 research outputs found
Prediction of postoperative atrial fibrillation with postoperative epicardial electrograms
Objectives. New-onset postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery. The arrhythmia often entails a longer hospital stay, greater risk of other complications, and higher mortality both short- and long-term. An investigation of the use of early atrial electrograms in predicting POAF in cardiac surgery was performed. Design. In this prospective observational study, a total of 99 consecutive adult patients undergoing coronary artery bypass grafting, valve surgery or both were included. On the first postoperative morning, standard 12-lead electrograms (ECG), unipolar atrial electrograms (aEG), and vital values were recorded. The outcome was new-onset POAF within one month postoperatively. Results. Three multivariable prediction models for POAF were formed using measurements derived from the ECG, aEG, and patient characteristics. Age, body mass index, and two unipolar electrogram measurements quantifying local activation time and fractionation were strongly associated with the outcome POAF. The performance of the POAF prediction models was assessed through receiver operating curve characteristics with cross-validation, and discrimination using the leave-one-out-method to internally validate the models. The cross-validated area under the receiver operating characteristic curve (AUC) was improved in a prediction model using atrial-derived electrogram variables (AUC 0.796, 95% CI 0.698-0.894), compared with previous ECG and clinical models (AUC 0.716, 95% CI 0.606-0.826 and AUC 0.718, 95% CI 0.613-0.822, respectively). Conclusions. This study found that easily obtainable measurements from atrial electrograms may be helpful in identifying patients at risk of POAF in cardiac surgery
Modelling of environmental impacts from biological treatment of organic municipal waste in EASEWASTE
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An Improved Global Model for Air-Sea Exchange of Mercury: High Concentrations over the North Atlantic
We develop an improved treatment of the surface ocean in the GEOS-Chem global 3-D biogeochemical model for mercury (Hg). We replace the globally uniform subsurface ocean Hg concentrations used in the original model with basin-specific values based on measurements. Updated chemical mechanisms for Hg0/HgII redox reactions in the surface ocean include both photochemical and biological processes, and we improved the parametrization of particle-associated Hg scavenging. Modeled aqueous Hg concentrations are consistent with limited surface water observations. Results more accurately reproduce high-observed MBL concentrations over the North Atlantic (NA) and the associated seasonal trends. High seasonal evasion in the NA is driven by inputs from Hg enriched subsurface waters through entrainment and Ekman pumping. Globally, subsurface waters account for 40% of Hg inputs to the ocean mixed layer, and 60% is from atmospheric deposition. Although globally the ocean is a net sink for 3.8 Mmol Hg yâ1, the NA is a net source to the atmosphere, potentially due to enrichment of subsurface waters with legacy Hg from historical anthropogenic sources.Engineering and Applied Science
A search for solar-like oscillations in K giants in the globular cluster M4
To expand the range in the colour-magnitude diagram where asteroseismology
can be applied, we organized a photometry campaign to find evidence for
solar-like oscillations in giant stars in the globular cluster M4. The aim was
to detect the comb-like p-mode structure characteristic for solar-like
oscillations in the amplitude spectra. The two dozen main target stars are in
the region of the bump stars and have luminosities in the range 50-140 Lsun. We
collected 6160 CCD frames and light curves for about 14000 stars were
extracted. We obtain high quality light curves for the K giants, but no clear
oscillation signal is detected. High precision differential photometry is
possible even in very crowded regions like the core of M4. Solar-like
oscillations are probably present in K giants, but the amplitudes are lower
than classical scaling laws predict.Comment: 14 pages, 16 figures, accepted for publication in A&
Morphological Instabilities in a growing Yeast Colony: Experiment and Theory
We study the growth of colonies of the yeast Pichia membranaefaciens on
agarose film. The growth conditions are controlled in a setup where nutrients
are supplied through an agarose film suspended over a solution of nutrients. As
the thickness of the agarose film is varied, the morphology of the front of the
colony changes. The growth of the front is modeled by coupling it to a
diffusive field of inhibitory metabolites. Qualitative agreement with
experiments suggests that such a coupling is responsible for the observed
instability of the front.Comment: RevTex, 4 pages and 3 figure
Solar-like oscillations in the G2 subgiant beta Hydri from dual-site observations
We have observed oscillations in the nearby G2 subgiant star beta Hyi using
high-precision velocity observations obtained over more than a week with the
HARPS and UCLES spectrographs. The oscillation frequencies show a regular comb
structure, as expected for solar-like oscillations, but with several l=1 modes
being strongly affected by avoided crossings. The data, combined with those we
obtained five years earlier, allow us to identify 28 oscillation modes. By
scaling the large frequency separation from the Sun, we measure the mean
density of beta Hyi to an accuracy of 0.6%. The amplitudes of the oscillations
are about 2.5 times solar and the mode lifetime is 2.3 d. A detailed comparison
of the mixed l=1 modes with theoretical models should allow a precise estimate
of the age of the star.Comment: 13 pages, 14 figures, accepted by ApJ. Fixed minor typo (ref to Fig
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Measurement of unique magnetic and superconducting phases in oxygen-doped high-temperature superconductors La<sub>2-x</sub>Sr<sub>x</sub>CuO<sub>4+y</sub>
We present a combined magnetic neutron scattering and muon spin rotation
study of the nature of the magnetic and superconducting phases in
electronically phase separated La(2-x)Sr(x)CuO(4+y), x = 0.04, 065, 0.09. For
all samples, we find long-range modulated magnetic order below T_N ~ T_c = 39
K. In sharp contrast wit oxygen-stoichiometric La(2-x)Sr(x)CuO(4), we find that
the magnetic propagation vector as well as the ordered magnetic moment is
independent of Sr content and consistent with that of the 'striped' cuprates.
Our study provides direct proof that superoxygenation in La(2-x)Sr(x)CuO(4+y)
allows the spin stripe ordered phase to emerge and phase separate from
superconducting regions with the hallmarks of optimally doped
oxygen-stoichiometric La(2-x)Sr(x)CuO(4)
Longâterm monitoring and experimental manipulation of a Chihuahuan desert ecosystem near Portal, Arizona (1977â2013)
Desert ecosystems have long served as model systems in the study of ecological concepts (e.g., competition, resource pulses, topâdown/bottomâup dynamics). However, the inherent variability of resource availability in deserts, and hence consumer dynamics, can also make them challenging ecosystems to understand. Study of a Chihuahuan desert ecosystem near Portal, Arizona began in 1977. At this site, 24 experimental plots were established and divided among controls and experimental manipulations. Experimental manipulations over the years include removal of all or some rodent species, all or some ants, seed additions, and various alterations of the annual plant community. This dataset includes data previously available through an older data publication and adds 11Â years of data. It also includes additional ant and weather data not previously available. These data have been used in a variety of publications documenting the effects of the experimental manipulations as well as the response of populations and communities to longâterm changes in climate and habitat. Sampling is ongoing and additional data will be published in the future.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146431/1/ecy1360.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146431/2/ecy1360_am.pd
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