The influence of oscillations on global existence for a class of semi-linear wave equations

The goal of this paper is to study the global existence of small data solutions to the Cauchy problem for the nonlinear wave equation u(tt) - a(t)(2) Delta u = u(t)(2) - a(t)(2)vertical bar del u vertical bar(2). In particular we are interested in statements for the 1D case. We will explain how the interplay between the increasing and oscillating behavior of the coefficient will influence global existence of small data solutions. Copyright c 2011 John Wiley & Sons, Ltd.

Comparison of Quantitative T-Wave Alternans Profiles of Healthy Subjects and ICD Patients

Background: Current relevance of T-wave alternans is based on its association with electrical disorder and elevated cardiac risk. Quantitative reports would improve understanding on TWA augmentation mechanisms during mental stress or prior to tachyarrhythmias. However, little information is available about quantitative TWA values in clinical populations. This study aims to create and compare TWA profiles of healthy subjects and ICD patients, evaluated on treadmill stress protocols. Methods: Apparently healthy subjects, not in use of any medication were recruited. All eligible ICD patients were capable of performing an attenuated stress test. TWA analysis was performed during a 15-lead treadmill test. The derived comparative profile consisted of TWA amplitude and its associated heart rate, at rest (baseline) and at peak TWA value. Chi-square or Mann-Whitney tests were used with p values <= 0.05. Discriminatory performance was evaluated by a binary logistic regression model. Results: 31 healthy subjects (8F, 23M) and 32 ICD patients (10F, 22M) were different on baseline TWA (1 +/- 2 mu V; 8 +/- 9 mu V; p < 0.001) and peak TWA values (26 +/- 13 mu V; 37 +/- 20 mu V; p = 0,009) as well as on baseline TWA heart rate (79 +/- 10 bpm; 67 +/- 15 bpm; p < 0.001) and peak TWA heart rate (118 +/- 8 bpm; 90 +/- 17 bpm; p < 0.001). The logistic model yielded sensitivity and specificity values of 88.9% and 92.9%, respectively. Conclusions: Healthy subjects and ICD patients have distinct TWA profiles. The new TWA profile representation (in amplitude-heart rate pairs) may help comparison among different research protocols. Ann Noninvasive Electrocardiol 2009;14(2):108-118.

Turbulent spots in boundary layers in a free-piston shock-tunnel flow

In this paper, experiments to detect turbulent spots in the transitional boundary layers, formed on a flat plate in a free-piston shock tunnel how, are reported. Experiments indicate that thin-film heat-transfer gauges are suitable for identifying turbulent-spot activity and can be used to identify parameters such as the convection rate of spots and the intermittency of turbulence.

PROWESS-SHOCK TRIAL: A PROTOCOL OVERVIEW AND PERSPECTIVES

Sepsis remains a challenge for intensive care physicians, as it keeps up with high mortality rate in spite of the high costs associated with its treatment. Several studies indicate that the infusion of Drotrecogin-alpha activated (DrotAA) reduce mortality in patients at high risk of death when administered early and secured the appropriate initial treatment of sepsis as recommended by Surviving Sepsis Campaign. Europe and United States of America differ regarding the criteria of high risk of death in sepsis, two or more organ dysfunctions and Acute Physiology and Chronic Health Evaluation 25 or more, respectively. In addition to varied definitions of high risk of death for inclusion of patients in sepsis studies, the possibility of bleeding related to drug use and intrinsic limitations related to study design led the Company to develop a new randomized, multinational, placebo-controlled, double-blind study to assess the effectiveness of drug in patients with septic shock in adults.

Potassium in Hemorrhagic Shock: A Potential Marker of Tissue Hypoxia

Background: This study was designed to evaluate serum potassium level variation in a porcine model of hemorrhagic shock ( HS). Methods: Eight pigs were studied in a controlled hemorrhage model of HS. Blood withdrawal began at a 50 mL/min to 70 mL/min rate, adjusted to reach a mean arterial pressure ( MAP) level of 60 mm Hg in 10 minutes. When MAP reached 60 mm Hg, the blood withdrawal rate was adjusted to maintain a MAP decrease rate of 10 mm Hg every 2 minutes to 4 minutes. Arterial and mixed venous blood samples were collected at MAP levels of 60 mm Hg, 50 mm Hg, 40 mm Hg, 30 mm Hg, 20 mm Hg, and 10 mm Hg and analyzed for oxygen saturation, PO(2), PCO(2), potassium, lactate, bicarbonate, hemoglobin, pH, and standard base excess. Results: Significant increase in serum potassium occurred early in all animals. The rate of rise in serum potassium and its levels accompanied the hemodynamic deterioration. Hyperkalemia ( K >5 mmol/L) incidence was 12.5% at 60 mm Hg and 50 mm Hg, 62.5% at 40 mm Hg, 87.5% at 30 mm Hg, and 100% at 20 mm Hg. Strong correlations were found between potassium levels and lactate ( R = 0.82), SvO(2) ( R = 0.87), Delta pH ( R = 0.83), and Delta PCO(2) ( R = 0.82). Conclusions: Serum potassium increase accompanies the onset of HS. The rise in serum potassium was directly related to the hemodynamic deterioration of HS and strongly correlated with markers of tissue hypoxia.

Fluid Resuscitation With Isotonic or Hypertonic Saline Solution Avoids Intraneural Calcium Influx After Traumatic Brain Injury Associated With Hemorrhagic Shock

Background: Calcium is one of the triggers involved in ischemic neuronal death. Because hypotension is a strong predictor of outcome in traumatic brain injury (TBI), we tested the hypothesis that early fluid resuscitation blunts calcium influx in hemorrhagic shock associated to TBI. Methods: Fifteen ketamine-halothane anesthetized mongrel dogs (18.7 kg +/- 1.4 kg) underwent unilateral cryogenic brain injury. Blood was shed in 5 minutes to a target mean arterial pressure of 40 mm Hg to 45 mm Hg and maintained at these levels for 20 minutes (shed blood volume = 26 mL/kg +/- 7 mL/kg). Animals were then randomized into three groups: CT (controls, no fluid resuscitation), HS (7.5% NaCl, 4 mL/kg, in 5 minutes), and LR (lactate Ringer`s, 33 mL/kg, in 15 minutes). Twenty minutes later, a craniotomy was performed and cerebral biopsies were obtained next to the lesion (""clinical penumbra"") and from the corresponding contralateral side (""lesion`s mirror"") to determine intracellular calcium by fluorescence signals of Fura-2-loaded cells. Results: Controls remained hypotensive and in a low-flow state, whereas fluid resuscitation improved hemodynamic profile. There was a significant increase in intracellular calcium in the injured hemisphere in CT (1035 nM +/- 782 nM), compared with both HS (457 nM +/- 149 nM, p = 0.028) and LR (392 nM +/- 178 nM, p = 0.017), with no differences between HS and LR (p = 0.38). Intracellular calcium at the contralateral, uninjured hemisphere was 438 nM +/- 192 nM in CT, 510 nM +/- 196 nM in HS, and 311 nM +/- 51 nM in LR, with no significant differences between them. Conclusion: Both small volume hypertonic saline and large volume lactated Ringer`s blunts calcium influx in early stages of TBI associated to hemorrhagic shock. No fluid resuscitation strategy promotes calcium influx and further neural damage.

A Comparison Between Pulse Pressure Variation and Right End Diastolic Volume Index as Guides to Resuscitation in a Model of Hemorrhagic Shock in Pigs

Background: Different hemodynamic parameters including static indicators of cardiac preload as right ventricular end-diastolic volume index (RVEDVI) and dynamic parameters as pulse pressure variation (PPV) have been used in the decision-making process regarding volume expansion in critically ill patients. The objective of this study was to compare fluid resuscitation guided by either PPV or RVEDVI after experimentally induced hemorrhagic shock. Methods: Twenty-six anesthetized and mechanically ventilated pigs were allocated into control (group I), PPV (group II), or RVEDVI (group III) group. Hemorrhagic shock was induced by blood withdrawal to target mean arterial pressure of 40 mm Hg, maintained for 60 minutes. Parameters were measured at baseline, time of shock, 60 minutes after shock, immediately after resuscitation with hydroxyethyl starch 6% (130/0.4), 1 hour and 2 hours thereafter. The endpoint of fluid resuscitation was determined as the baseline values of PPV and RVEDVI. Statistical analysis of data was based on analysis of variance for repeated measures followed by the Bonferroni test (p < 0.05). Results: Volume and time to resuscitation were higher in group III than in group II (group III = 1,305 +/- 331 mL and group II = 965 +/- 245 mL, p < 0.05; and group III = 24.8 +/- 4.7 minutes and group II = 8.8 +/- 1.3 minutes, p < 0.05, respectively). All static and dynamic parameters and biomarkers of tissue oxygenation were affected by hemorrhagic shock and nearly all parameters were restored after resuscitation in both groups. Conclusion: In the proposed model of hemorrhagic shock, resuscitation to the established endpoints was achieved within a smaller amount of time and with less volume when guided by PPV than when guided by pulmonary artery catheter-derived RVEDVI.

Acute Pancreatitis Hypertonic Saline Increases Heat Shock Proteins 70 and 90 and Reduces Neutrophil Infiltration in Lung Injury

Objectives: Acute pancreatitis (AP) protease release induces lung parenchymal destruction via matrix metalloproteinases (MMPs), a neutrophil (polymorphonuclear leukocyte)-dependent process. Recent studies in hemorrhagic shock revealed that hypertonic saline (HTS) has an anti-inflammatory effect and can inhibit a variety of neutrophil functions. The aim of this study was to determine whether HTS and its actions in the pathway of neutrophil migration, MMPs, and heat shock proteins (HSPs) are effective in protecting the lung from injury associated with AP. Methods: We determined neutrophil infiltration and expressions of MMPs and HSPs in the lung tissue after AP induced by retrograde infusion of 2.5% of sodium taurocholate. Results: Animals submitted to AP that received HTS compared with those who received normal saline presented with increased HSP70 and HSP90 expressions and reduced myeloperoxidase levels and MMP-9 expression and activity. Conclusions: Our data raised the hypothesis that a sequence of HTS lung protection events increases HSP70 and HSP90, inhibiting infiltration of neutrophils and their protease actions in the lung.

Supersonic velocimetry in a shock tube using laser enhanced ionisation and planar laser induced fluorescence

A novel flow-tagging technique is presented which was employed to measure gas velocities in the free stream of a shock tube. This method is based on the laser spectroscopic techniques of Laser-Enhanced Ionisation (LEI) and Laser-Induced Fluorescence (LIF). The flow in the shock tube is seeded with small amounts of sodium, and LEI is used to produce a substantial depletion of neutral sodium atom concentration in a well-defined region of the flow, by using two wavelength-resonance excitation and subsequent collisional ionisation. At a specific time delay, single-laser-pulse planar LIF is utilised to produce a two-dimensional (2-D) inverse image of the depleted tagged region downstream of the flow. By measuring the displacement of the tagged region, free stream velocities in a shock tube were determined. Large variations in the concentration of sodium seeded into the flow were observed and even in the presence of these large variations accurate free-stream velocity measurements were obtained. The experimentally determined value for velocity compares very well with the predicted velocity.

Effects of dobutamine on gut mucosal nitric oxide production during endotoxic shock in rabbits

Background: Dobutamine is the agent of choice for increasing cardiac output during myocardial depression in humans with septic shock. Studies have shown that beta-adrenoceptor agonists influence nitric oxide generation, probably by modulating cyclic adenosine monophosphate. We investigated the effects of dobutamine on the systemic and luminal gut release of nitric oxide during endotoxic shock in rabbits. Materials/Methods: Twenty anesthetized and ventilated New Zealand rabbits received placebo or intravenous lipopolysaccharide with or without dobutamine (5 mu g/kg/min). Ultrasonic flow probes placed around the superior mesenteric artery and the abdominal aorta continously estimated the flow. A segment from the ileum was isolated and perfused, and scrum nitrate/nitrite levels were measured in the perfusate solution and the serum every hour. Results: The mean arterial pressure decreased with statistical significance in the lipopolysaccharide group but not in the lipopolysaccharide/dobutamine group. The abdominal aortic flow decreased statistically significantly after lipopolysaccharide administration in both groups but recovered to base-line in the lipopolysaccharide/dobutamine group. The flow in the superior mesenteric artery was statistically significantly higher in the lipopolysaccharide/dobutamine group than in the lipopolysaccharide group at 2 hours. The serum nitrate/nitrite levels were higher in the lipopolysaccharide group and lower in the lipopolysaccharide/dobutamine group than those in the control group. The gut luminal perfusate serum nitrate/nitric level was higher in the lipopolysaccharide group than in the lipopolysaccharide/dobutamine group. Conclusions: Dobutamine can decrease total and intestinal nitric oxide production in vivo. Those effects seem to be inversely proportional to the changes in blood flow.

Beach water table fluctuations due to wave run-up: Capillarity effects

High-frequency beach water table fluctuations due to wave run-up and rundown have been observed in the field [Waddell, 1976]. Such fluctuations affect the infiltration/exfiltration process across the beach face and the interstitial oxygenation process in the beach ecosystem. Accurate representation of high-frequency water table fluctuations is of importance in the modeling of (1) the interaction between seawater and groundwater, more important, the effects on swash sediment transport and (2) the biological activities in the beach ecosystem. Capillarity effects provide a mechanism for high-frequency water table fluctuations. Previous modeling approaches adopted the assumption of saturated flow only and failed to predict the propagation of high-frequency fluctuations in the aquifer. In this paper we develop a modified kinematic boundary condition (kbc) for the water table which incorporates capillarity effects. The application of this kbc in a boundary element model enables the simulation of high-frequency water table fluctuations due to wave run-up. Numerical tests were carried out for a rectangular domain with small-amplitude oscillations; the behavior of water table responses was found to be similar to that predicted by an analytical solution based on the one-dimensional Boussinesq equation. The model was also applied to simulate the water table response to wave run-up on a doping beach. The results showed similar features of water table fluctuations observed in the field. In particular, these fluctuations are standing wave-like with the amplitude becoming increasingly damped inland. We conclude that the modified kbc presented here is a reasonable approximation of capillarity effects on beach water table fluctuations. However, further model validation is necessary before the model can confidently be used to simulate high-frequency water table fluctuations due to wave run-up.

Small volume resuscitation with 3% hypertonic saline solution decrease inflammatory response and attenuates end organ damage after controlled hemorrhagic shock

BACKGROUND: Recently, studies have been conducted examining the efficacy of 3% hypertonic saline solution (HS) for the treatment of traumatic brain injury; however, few studies have analyzed the effects of 3% hemorrhagic shock during hemorrhagic shock. The aim of this study was to test the potential immunomodulatory benefits of 3% hemorrhagic shock resuscitation over standard fluid resuscitation. METHODS: Wistar rats were bled to a mean arterial pressure of 35 mm Hg and then randomized into 3 groups: those treated with lactated Ringer`s solution (LR; 33 mL/kg, n = 7), 3% HS (10 mL/kg, n = 7), and 7.5% HS (4 mL/kg, n = 7). Half of the extracted blood was reinfused after fluid resuscitation. Animals that did not undergo shock served as controls (n = 5). Four hours after hemorrhagic shock, blood was collected for the evaluation of tumor necrosis factor-a and interleukin-6 by enzyme immunoassay. Lung and intestinal samples were obtained for histopathologic analysis. RESULTS: Animals in the HS groups had significantly higher mean arterial pressure than those in the LR group 1 hour after treatment. Osmolarity and sodium levels were markedly elevated in the HS groups. Tumor necrosis factor-alpha and interleukin-6 levels were similar between the control and HS groups but significantly higher in the LR group (P < .05). The lung injury score was significantly higher in the LR group compared with the 7.5% HS and 3% HS groups (5.7 +/- 0.7, 2.1 +/- 0.4, and 2.7 +/- 0.5, respectively). Intestinal injury was attenuated in the 7.5% HS and 3% HS groups compared with the LR group (2.0 +/- 0.6, 2.3 +/- 0.4, and 5.9 +/- 0.6, respectively). CONCLUSIONS: A small-volume resuscitation strategy modulates the inflammatory response and decreases end-organ damage after HS. Three percent HS provides immunomodulatory and metabolic effects similar to those observed with conventional concentrations of HS. (C) 2009 Elsevier Inc. All rights reserved.

A compact shock-assisted free-piston driver for impulse facilities

A free-piston driver that employs entropy-raising shock processes with diaphragm rupture has been constructed, which promises significant theoretical advantages over isentropic compression. Results from a range of conditions with helium and argon driver gases are reported. Significant performance gains were achieved in some test cases. Heat losses are shown to have a strong effect on driver processes. Measurements compare well with predictions from a quasi-one-dimensional numerical code.