70,601 research outputs found
Beating heart coronary surgery and renal function: a prospective randomised study (Presented at 18th Spring Meeting of the Association of Cardiothoracic Anaesthetists: Selected abstracts, Cambridge, UK. 22 June 2001)
Introduction
Cardiopulmonary bypass (CPB) is widely regarded as an important contributor to renal failure, a well recognised complication, following coronary artery surgery (CABG). Off-pump coronary surgery (OPCAB) is intuitively considered renoprotective. We examine the extent of renal glomerular and tubular injury in low-risk patients undergoing either OPCAB or on-pump coronary artery bypass (ONCAB).Methods
Forty patients awaiting elective CABG were prospectively randomized into those undergoing OPCAB (n = 20) and ONCAB (n = 20). Table 1 illustrates the exclusion criteria. Glomerular and tubular injury were assessed, respectively, by urinary excretion of microalbumin and retinol binding protein (RBP) indexed to urinary creatinine [1]. Daily measurements were made from admission to postoperative day 5. Fluid balance, serum creati-nine and blood urea were also monitored.
Results
No mortality or renal complication was observed. Both groups had similar demographic make-up. The OPCAB group received fewer coronary grafts than their counterparts (1.8 versus 2.8; P = 0.002). Serum creatinine and blood urea remained normal in both groups throughout the study. A dramatic and similar rise in mean ± 2SD urinary RBP:creatinine ratio occurred in both groups peaking on day 1 (3183 ± 2534 versus 4035 ± 4078; P = 0.43) before returning to baseline levels. These trends were also observed with the urinary microalbumin:creatinine ratio (5.05 ± 2.66 versus 6.77 ± 5.76; P = 0.22). ONCAB patients had a significantly more negative fluid balance on postoperative day 2 (-183 ± 1118 versus 637 ± 847 ml; P < 0.05).
Conclusions
Although renal dysfunction did not clinically occur in any patient, sensitive indicators revealed significant and similar injury to both renal tubules and glomeruli following either OPCAB or ONCAB. These suggest that avoidance of CPB per se does not offer additional renoprotection to patients at low risk of perioperative renal insult during CABG
Slow X-ray bursts and chromospheric flares with filament disruption
The data from OGO-5 and OSO-7 X-ray experiments have been analyzed to study six chromospheric flares with filament disruption associated with slow thermal X-ray bursts. Filament activation accompanied by a slight X-ray enhancement precedes the first evidence of H alpha flare by a few minutes. Rapid increase of the soft X-ray flux is accompanied by a sudden brightening of the filament when viewed on-band H alpha. Thereafter the bright chromospheric strands reach their maximum brightness with maximum X-ray flux. Any plateau or slow decay phase in the X-ray flux is accompanied by a quieting in filament activity and even by filament re-appearance. The height of the disrupted prominence is proportional to the soft X-ray flux for the August 3, 1970 limb occulted event
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Communicability across evolving networks
Many natural and technological applications generate time ordered sequences of networks, defined over a fixed set of nodes; for example time-stamped information about ‘who phoned who’ or ‘who came into contact with who’ arise naturally in studies of communication and the spread of disease. Concepts and algorithms for static networks do not immediately carry through to this dynamic setting. For example, suppose A and B interact in the morning, and then B and C interact in the afternoon. Information, or disease, may then pass from A to C, but not vice versa. This subtlety is lost if we simply summarize using the daily aggregate network given by the chain A-B-C. However, using a natural definition of a walk on an evolving network, we show that classic centrality measures from the static setting can be extended in a computationally convenient manner. In particular, communicability indices can be computed to summarize the ability of each node to broadcast and receive information. The computations involve basic operations in linear algebra, and the asymmetry caused by time’s arrow is captured naturally through the non-mutativity of matrix-matrix multiplication. Illustrative examples are given for both synthetic and real-world communication data sets. We also discuss the use of the new centrality measures for real-time monitoring and prediction
Antiferromagnetic Exchange Interaction between Electrons on Degenerate LUMOs in Benzene Dianion
We discuss the ground state of Benzene dianion (Bz) on the basis of
the numerical diagonalization method of an effective model of orbitals.
It is found that the ground state can be the spin singlet state, and the
exchange coupling between LUMOs can be antiferromagnetic.Comment: Accepted for publication in J. Phys. Soc. Jpn., 2 pages, 3 figure
High Energy Quark-Antiquark Elastic scattering with Mesonic Exchange
We studies the high energy elastic scattering of quark anti-quark with an
exchange of a mesonic state in the channel with .
Both the normalization factor and the Regge trajectory can be calculated in
PQCD in cases of fixed (non-running) and running coupling constant. The
dependence of the Regge trajectory on the coupling constant is highly
non-linear and the trajectory is of order of in the interesting physical
range.Comment: 29 page
Phase glass and zero-temperature phase transition in a randomly frustrated two-dimensional quantum rotor model
The ground state of the quantum rotor model in two dimensions with random
phase frustration is investigated. Extensive Monte Carlo simulations are
performed on the corresponding (2+1)-dimensional classical model under the
entropic sampling scheme. For weak quantum fluctuation, the system is found to
be in a phase glass phase characterized by a finite compressibility and a
finite value for the Edwards-Anderson order parameter, signifying long-ranged
phase rigidity in both spatial and imaginary time directions. Scaling
properties of the model near the transition to the gapped, Mott insulator state
with vanishing compressibility are analyzed. At the quantum critical point, the
dynamic exponent is greater than one. Correlation
length exponents in the spatial and imaginary time directions are given by
and , respectively, both assume values
greater than 0.6723 of the pure case. We speculate that the phase glass phase
is superconducting rather than metallic in the zero current limit.Comment: 14 pages, 4 figures, to appear in JSTA
Negative Link Prediction in Social Media
Signed network analysis has attracted increasing attention in recent years.
This is in part because research on signed network analysis suggests that
negative links have added value in the analytical process. A major impediment
in their effective use is that most social media sites do not enable users to
specify them explicitly. In other words, a gap exists between the importance of
negative links and their availability in real data sets. Therefore, it is
natural to explore whether one can predict negative links automatically from
the commonly available social network data. In this paper, we investigate the
novel problem of negative link prediction with only positive links and
content-centric interactions in social media. We make a number of important
observations about negative links, and propose a principled framework NeLP,
which can exploit positive links and content-centric interactions to predict
negative links. Our experimental results on real-world social networks
demonstrate that the proposed NeLP framework can accurately predict negative
links with positive links and content-centric interactions. Our detailed
experiments also illustrate the relative importance of various factors to the
effectiveness of the proposed framework
Temperature Effects on Threshold Counterion Concentration to Induce Aggregation of fd Virus
We seek to determine the mechanism of like-charge attraction by measuring the
temperature dependence of critical divalent counterion concentration
() for the aggregation of fd viruses. We find that an increase in
temperature causes to decrease, primarily due to a decrease in the
dielectric constant () of the solvent. At a constant ,
is found to increase as the temperature increases. The effects of
and on can be combined to that of one parameter:
Bjerrum length (). decreases exponentially as
increases, suggesting that entropic effect of counterions plays an important
role at the onset of bundle formation.Comment: 12 pages, 3 figure
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