What’s in a wave?

In western society, cardiovascular disease is one of the leading causes of death. An appropriate lifestyle and therapeutic interventions can delay the deterioration of cardiovascular disease. As a result, early detection of cardiovascular disease has received significant attention. Two of the oldest cardiovascular signals measured are blood pressure [1] and ECG [2]. These measures provide (non-) invasive estimates of cardiac and vascular function. With technical advances, the entire arterial blood pressure waveform (figure 1) became available to clinicians, allowing a major step forward in the recognition of cardiovascular disease. For example, the arterial blood pressure waveform allows for the determination of vascular stiffness, which has been shown to be an early predictor of the development of hypertension [3] and risk for myocardial infarction [4]. The arterial blood pressure waveform is also used in the early detection of shock [5, 6], guiding immediate treatment with the administration of fluids and/or vaso-active agents. Hence the evaluation of the arterial blood pressure waveform has become part of daily clinical practice

Weak-Localization in Chaotic Versus Non-Chaotic Cavities: A Striking Difference in the Line Shape

We report experimental evidence that chaotic and non-chaotic scattering through ballistic cavities display distinct signatures in quantum transport. In the case of non-chaotic cavities, we observe a linear decrease in the average resistance with magnetic field which contrasts markedly with a Lorentzian behavior for a chaotic cavity. This difference in line-shape of the weak-localization peak is related to the differing distribution of areas enclosed by electron trajectories. In addition, periodic oscillations are observed which are probably associated with the Aharonov-Bohm effect through a periodic orbit within the cavities.Comment: 4 pages revtex + 4 figures on request; amc.hub.94.

Low tidal volume ventilation ameliorates left ventricular dysfunction in mechanically ventilated rats following LPS-induced lung injury

Background: High tidal volume ventilation has shown to cause ventilator-induced lung injury (VILI), possibly contributing to concomitant extrapulmonary organ dysfunction. The present study examined whether left ventricular (LV) function is dependent on tidal volume size and whether this effect is augmented during lipopolysaccharide(LPS)-induced lung injury. Methods: Twenty male Wistar rats were sedated, paralyzed and then randomized in four groups receiving mechanical ventilation with tidal volumes of 6 ml/kg or 19 ml/kg with or without intrapulmonary administration of LPS. A conductance catheter was placed in the left ventricle to generate pressure-volume loops, which were also obtained within a few seconds of vena cava occlusion to obtain relatively load-independent LV systolic and diastolic function parameters. The end-systolic elastance / effective arterial elastance (Ees/Ea) ratio was used as the primary parameter of LV systolic function with the end-diastolic elastance (Eed) as primary LV diastolic function. Results: Ees/Ea decreased over time in rats receiving LPS (p = 0.045) and high tidal volume ventilation (p = 0.007), with a lower Ees/Ea in the rats with high tidal volume ventilation plus LPS compared to the other groups (p < 0.001). Eed increased over time in all groups except for the rats receiving low tidal volume ventilation without LPS (p = 0.223). A significant interaction (p < 0.001) was found between tidal ventilation and LPS for Ees/Ea and Eed, and all rats receiving high tidal volume ventilation plus LPS died before the end of the experiment. Conclusions: Low tidal volume ventilation ameliorated LV systolic and diastolic dysfunction while preventing death following LPS-induced lung injury in mechanically ventilated rats. Our data advocates the use of low tidal volumes, not only to avoid VILI, but to avert ventilator-induced myocardial dysfunction as well

Density functional theory calculations of adsorption-induced surface stress changes

Density functional theory calculations of adsorbate-induced surface stress changes have been performed for a number of adsorbate and overlayer systems for which experimental data exists, namely: oxygen and sulphur adsorption on Ni(1 0 0); oxygen adsorption on W(1 1 0); pseudomorphic growth of Ni on Cu(1 0 0) and of Fe on W(1 1 0); oxygen adsorption on a 5 ML pseudomorphic film of Ni(1 0 0) grown on Cu(1 0 0). The theoretical calculations reproduce all the qualitative features of the experimental data, but there are some significant quantitative differences, most notably for the two atomic adsorbates on the bulk Ni(1 0 0) surface, for which the theoretical stress changes are substantially smaller than the experimental ones, a situation not obviously attributable to experimental error. For the W(1 1 0)/Fe system there is also a marked difference between experiment and theory in the coverage at which key surface stress changes occur

Four Dimensional String/String/String Triality

In six spacetime dimensions, the heterotic string is dual to a Type $IIA$ string. On further toroidal compactification to four spacetime dimensions, the heterotic string acquires an SL(2,\BbbZ)_S strong/weak coupling duality and an SL(2,\BbbZ)_T \times SL(2,\BbbZ)_U target space duality acting on the dilaton/axion, complex Kahler form and the complex structure fields $S,T,U$ respectively. Strong/weak duality in $D=6$ interchanges the roles of $S$ and $T$ in $D=4$ yielding a Type $IIA$ string with fields $T,S,U$. This suggests the existence of a third string (whose six-dimensional interpretation is more obscure) that interchanges the roles of $S$ and $U$. It corresponds in fact to a Type $IIB$ string with fields $U,T,S$ leading to a four-dimensional string/string/string triality. Since SL(2,\BbbZ)_S is perturbative for the Type $IIB$ string, this $D=4$ triality implies $S$-duality for the heterotic string and thus fills a gap left by $D=6$ duality. For all three strings the total symmetry is SL(2,\BbbZ)_S \times O(6,22;\BbbZ)_{TU}. The O(6,22;\BbbZ) is {\it perturbative} for the heterotic string but contains the conjectured {\it non-perturbative} SL(2,\BbbZ)_X, where $X$ is the complex scalar of the $D=10$ Type $IIB$ string. Thus four-dimensional triality also provides a (post-compactification) justification for this conjecture. We interpret the $N=4$ Bogomol'nyi spectrum from all three points of view. In particular we generalize the Sen-Schwarz formula for short multiplets to include intermediate multiplets also and discuss the corresponding black hole spectrum both for the $N=4$ theory and for a truncated $S$--$T$--$U$ symmetric $N=2$ theory. Just as the first two strings are described by the four-dimensional {\it elementary} and {\it dual solitonic} solutions, so theComment: 36 pages, Latex, 2 figures, some references changed, minor changes in formulas and tables; to appear in Nucl. Phys.

Soluble receptor for advanced glycation end products as an indicator of pulmonary vascular injury after cardiac surgery

Background: Cardiac surgery is frequently complicated by an acute vascular lung injury and this may be mediated, at least in part, by the (soluble) receptor for advanced glycation end products (sRAGE).Methods: In two university hospital intensive care units, circulating sRAGE was measured together with the 68Gallium-transferrin pulmonary leak index (PLI), a measure of pulmonary vascular permeabiliy, in 60 consecutive cardiac surgery patients stratified by the amount of blood transfusion, within 3 hours of admission to the intensive care.Results: Cardiac surgery resulted in elevated plasma sRAGE levels compared to baseline (315 ± 181 vs 110 ± 55 pg/ml, P = 0.001). In 37 patients the PLI was elevated 50% above normal. The PLI correlated with sRAGE (r2 = 0.11, P = 0.018). Plasma sRAGE discriminated well between those with an elevated PLI and those with a normal PLI (area under the operator curve 0.75; P = 0.035; 95% CI 0.55-0.95), with 91% sensitivity but low specificity of 36% at a cutoff value of 200 pg/mL

Strong/Weak Coupling Duality from the Dual String

On compactification to six spacetime dimensions, the fundamental heterotic string admits as a soliton a dual string whose effective worldsheet action couples to the background fields of the dual formulation of six-dimensional supergravity. On further toroidal compactification to four spacetime dimensions, the dual string acquires an $O(2,2;Z)$ target-space duality. This contains as a subgroup the axion-dilaton $SL(2,Z)$ which corresponds to a strong/weak coupling duality for the fundamental string. The dual string also provides a new non-perturbative mechanism for enhancement of the gauge symmetry.Comment: 23 pages LATE