Exponential Shock Research Articles

Computational analyses of transcriptomic data reveal the dynamic organization of the Escherichia coli chromosome under different conditions

The circular chromosome of Escherichia coli has been suggested to fold into a collection of sequentially consecutive domains, genes in each of which tend to be co-expressed. It has also been suggested that such domains, forming a partition of the genome, are dynamic with respect to the physiological conditions. However, little is known about which DNA segments of the E. coli genome form these domains and what determines the boundaries of these domain segments. We present a computational model here to partition the circular genome into consecutive segments, theoretically suggestive of the physically folded supercoiled domains, along with a method for predicting such domains under specified conditions. Our model is based on a hypothesis that the genome of E. coli is partitioned into a set of folding domains so that the total number of unfoldings of these domains in the folded chromosome is minimized, where a domain is unfolded when a biological pathway, consisting of genes encoded in this DNA segment, is being activated transcriptionally. Based on this hypothesis, we have predicted seven distinct sets of such domains along the E. coli genome for seven physiological conditions, namely exponential growth, stationary growth, anaerobiosis, heat shock, oxidative stress, nitrogen limitation and SOS responses. These predicted folding domains are highly stable statistically and are generally consistent with the experimental data of DNA binding sites of the nucleoid-associated proteins that assist the folding of these domains, as well as genome-scale protein occupancy profiles, hence supporting our proposed model. Our study established for the first time a strong link between a folded E. coli chromosomal structure and the encoded biological pathways and their activation frequencies.

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Analytical Modeling of the Underwater Shock Response of Rigid and Elastic Plates Near a Solid Boundary

In this paper, analytical solutions are derived for the case when an elastic water-backed plate (WBP) is subject to an exponential shock loading near a fixed solid boundary. Two cases, a rigid plate and an elastic plate represented by two mass elements connected by a spring and a dashpot, are studied. The analytical solution is extended from Taylor's (1963, “The Pressure and Impulse of Submarine Explosion Waves on Plates,” Scientific Papers of Sir Geoffrey Ingram Taylor, Vol. 3, G. K. Batchelor, ed., Cambridge University Press, Cambridge, UK, pp. 287–303) floating air-backed plate (ABP) model and the water-backed plate model of Liu and Young (2008, “Transient Response of Submerged Plates Subject to Underwater Shock Loading: An Analytical Perspective,” J. Appl. Mech., 75(4), 044504; 2010, “Shock-Structure Interaction Considering Pressure Precursor,” Proceedings of the 28th Symposium on Naval Hydrodynamics, Pasadena, CA). The influences of five parameters are studied: (a) the distance of the fixed boundary from the back plate d, (b) the fluid structure interaction (FSI) parameter φ of the plate, (c) the stiffness of the plate as represented by the natural frequency of the system T, (d) the material damping coefficient CD of the plate, and (e) the pressure precursor (rise) time θr. The results show that the pressure responses at the front and back surfaces of the plate are greatly affected by the proximity to the fixed boundary, the fluid-structure interaction parameter, the ratio of the shock decay time to the natural period of the structure, and the rise time of incident pressure. The effect of structural damping (assuming a typical material damping coefficient of 5%) is found to be practically negligible compared to the other four parameters.

New Self Similar Solution behind Exponential Magneto Radiative Blast Wave in a Dusty Gas

The self-similar solutions for point source magnetoradiative exponential shock wave moving into uniform atmosphere of dusty gas where total energy of wave depend on cube of shock radius has discussed. The effects of radiation on the discontinuities are also investigated. The ordinary differential equation obtained by similarity method are solved by software Matlab. The nature of flow variables are illustrated through graphs.

Ascending-Ramp Biphasic Waveform Has a Lower Defibrillation Threshold and Releases Less Troponin I Than a Truncated Exponential Biphasic Waveform

We tested the hypothesis that the shape of the shock waveform affects not only the defibrillation threshold but also the amount of cardiac damage. Defibrillation thresholds were determined for 11 waveforms-3 ascending-ramp waveforms, 3 descending-ramp waveforms, 3 rectilinear first-phase biphasic waveforms, a Gurvich waveform, and a truncated exponential biphasic waveform-in 6 pigs with electrodes in the right ventricular apex and superior vena cava. The ascending, descending, and rectilinear waveforms had 4-, 8-, and 16-millisecond first phases and a 3.5-millisecond rectilinear second phase that was half the voltage of the first phase. The exponential biphasic waveform had a 60% first-phase and a 50% second-phase tilt. In a second study, we attempted to defibrillate after 10 seconds of ventricular fibrillation with a single ≈30-J shock (6 pigs successfully defibrillated with 8-millisecond ascending, 8-millisecond rectilinear, and truncated exponential biphasic waveforms). Troponin I blood levels were determined before and 2 to 10 hours after the shock. The lowest-energy defibrillation threshold was for the 8-milliseconds ascending ramp (14.6±7.3 J [mean±SD]), which was significantly less than for the truncated exponential (19.6±6.3 J). Six hours after shock, troponin I was significantly less for the ascending-ramp waveform (0.80±0.54 ng/mL) than for the truncated exponential (1.92±0.47 ng/mL) or the rectilinear waveform (1.17±0.45 ng/mL). The ascending ramp has a significantly lower defibrillation threshold and at ≈30 J causes 58% less troponin I release than the truncated exponential biphasic shock. Therefore, the shock waveform affects both the defibrillation threshold and the amount of cardiac damage.

SIMILARITY SOLUTIONS FOR STRONG SHOCKS IN A NON-IDEAL GAS

A group theoretic method is used to obtain an entire class of similarity solutions to the problem of shocks propagating through a non-ideal gas and to characterize analytically the state dependent form of the medium ahead for which the problem is invariant and admits similarity solutions. Different cases of possible solutions, known in the literature, with a power law, exponential or logarithmic shock paths are recovered as special cases depending on the arbitrary constants occurring in the expression for the generators of the transformation. Particular case of collapse of imploding cylindrically and spherically symmetric shock in a medium in which initial density obeys power law is worked out in detail. Numerical calculations have been performed to obtain the similarity exponents and the profiles of the flow variables behind the shock, and comparison is made with the known results.

Self-similar solutions in a plasma with axial magnetic field (θ-pinch)

In this paper, Lie group of transformation method is used to investigate the self-similar solutions for the system of partial differential equations describing a plasma with axial magnetic field (θ–pinch). The arbitrary constants occurring in the expressions for the infinitesimals of the local Lie group of transformations give rise to two different cases of possible solutions i.e. with a power law and exponential shock paths. A particular solution to the problem in one case has been found out.

Are we listening to music or noise? Use of the Lyapunov exponent for comprehensive assessment of heart rate complexity during hemorrhage in sedated conscious miniature swine

Abstract : Objectives: Application of tools from nonlinear dynamics for calculation of changes in heart rate complexity assumes presence of deterministic chaotic trends in the investigated data. Calculation of the largest Lyapunov exponent (LLE) is a standard method for confirmation of whether such trends are present and is used to characterize the level of chaos in complex physiologic systems. We sought to evaluate the utility of LLE for that purpose during severe pump-controlled exponential hemorrhagic shock.

Spatial distribution and extent of electroporation by strong internal shock in intact structurally normal and chronically infarcted rabbit hearts.

Although life-saving, a strong internal defibrillation shock may temporarily or permanently damage the heart via disruption of cell membranes (electroporation). Spatial extent of electroporation in intact, normal, or infarcted hearts has not been investigated. In this study, shock-induced electroporation in intact rabbit hearts with and without chronic (>4 weeks) left ventricular myocardial infarction (MI) was characterized. A coil shock electrode was inserted in the right ventricle of Langendorff-perfused hearts. One truncated exponential monophasic shock (+300 V, 8 ms) was delivered by a 150 microF capacitor clinical defibrillator while the heart was perfused with membrane-impermeant dye propidium iodide (PI). The heart was sectioned transversely, and uptake of PI into ventricular myocardium through electropores was quantified. Histological evaluation was performed via Masson's trichrome staining. PI accumulation was minimal in the control (n = 3) and MI (n = 3) hearts without shock. Following shock delivery, (1) in control (n = 5) and MI (n = 5) hearts, electroporation mostly occurred near the shock electrode and was longitudinally distributed along the active region of the shock electrode; (2) in MI group, electroporation was significantly increased (P < 0.05) in the surviving anterior epicardial layers of the infarcted region; and (3) between the control and MI groups, the overall extent of electroporation was similar. Shock-induced electroporation was spatially dependent on the location and dimension of the active region of the shock electrode. The overall extent of electroporation in the MI heart was comparable with the control heart, but the surviving anterior epicardial layers in the infarcted region were more susceptible to electroporation.

Transvenous Electrical Cardioversion of Equine Atrial Fibrillation: Patient Factors and Clinical Results in 72 Treatment Episodes

Transvenous electrical cardioversion (TVEC) has been developed for treatment of atrial fibrillation (AF) in horses. The relationship among patient variables, treatment response, and outcome in a typical referral population has not been evaluated. Patient variables such as age, sex, weight, and duration of arrhythmia affect prognosis for response to treatment and the energy level at which cardioversion occurs. TVEC was applied to 72 episodes of lone AF in 63 client-owned performance horses, with the majority (54) being Standardbred racehorses. Catheterization of the right atrium (RA) and pulmonary artery (PA) through the jugular vein was used for electrode placement before horses were placed under general anesthesia. Biphasic, truncated exponential shock waves were delivered at incremental energy levels until cardioversion was achieved or a maximum single-energy level of 300 J was reached (cumulative energy 50-1,960 J). A multivariate model was constructed to evaluate influence of patient factors on cardioversion energy. Cardioversion was achieved in 71 of 72 episodes (62 of 63 horses) at a mean energy of 165.43 +/- 8.75 J. Cardioversion energy was higher for females than for males, and for interaction terms, weight was negatively related to energy in females and positively related in males. Age was positively related to cardioversion energy in females. No relationship was identified between duration of arrhythmia before treatment and prognosis for response or cardioversion energy. TVEC is highly effective in the treatment of lone AF in horses. Although age and sex influence cardioversion energy level, duration of arrhythmia does not.

Similarity solutions for the flow behind an exponential shock in a non-ideal gas

Similarity solutions for the flow of a non-ideal gas behind a strong exponential shock driven out by a piston (cylindrical or spherical) moving with time according to an exponential law are obtained. Similarity solutions exist only when the surrounding medium is of constant density. Solutions are obtained, in both the cases, when the flow between the shock and the piston is isothermal or adiabatic. It is found that the assumption of zero temperature gradient brings a profound change in the density distribution as compare to that of the adiabatic case. Effects of the non-idealness of the gas on the flow-field between the shock and the piston are investigated. The variations of density-ratio across the shock and the location of the piston with the parameter of non-idealness of the gas \({\overline{b}}\) are also obtained.

Similarity solutions for unsteady flow behind an exponential shock in a dusty gas

One-dimensional self-similar unsteady flow behind a strong exponential shock driven out by a piston moving with time according to an exponential law is investigated. The medium is assumed to be a mixture of small solid particles and a perfect gas. In order to get some essential features of the shock propagation, small solid particles are considered as pseudo-fluid and it is assumed that the equilibrium flow condition is maintained in the flow-field, and that the viscous-stress and heat conduction of the mixture are negligible. Solutions are obtained, in both cases, when the flow between the shock and the piston is isothermal or adiabatic. It is found that the assumption of zero temperature gradient brings a profound change in the density distribution as compared to that of the adiabatic case. Effects of a change in the mass concentration of the solid particles in the mixture Kp and the ratio of the density of solid particles to that of initial density of the gas G1 are also obtained.

Transvenous Electrical Cardioversion of Equine Atrial Fibrillation Technical Considerations

Conventional treatment of equine atrial fibrillation (AF) involves administration of quinidine salts. Most uncomplicated cases respond to treatment, but pharmacologic cardioversion involves a range of adverse effects, and some horses are unable to tolerate medication. A study was undertaken to develop transvenous electrical cardioversion (TVEC) as an alternative treatment. Safety issues and catheter placement techniques with catheter-integrated cardioversion electrodes were investigated, and responses to shock application were evaluated. After the premortem catheterization of elective-euthanasia horses, no tissue abnormalities were detected at postmortem examination. To evaluate the response to the application of shocks and appropriate electrode positions, an electrical cardioversion of research horses in chronic AF was then attempted. After catheterization of the right atrium (RA) and pulmonary artery through the right jugular vein, horses were placed under general anesthesia. Biphasic, truncated exponential shock waves were delivered at incremental energies until cardioversion was achieved or until a maximum energy of 300 J was reached. Five treatment events were applied to 3 horses, with cardioversion achieved in one of the treatment events. No adverse effects of cardioversion attempts or general anesthesia were observed. The procedure was then applied to 8 client-owned horses, with cardioversion achieved in 7. No adverse responses to appropriately delivered shocks were observed. No antiarrhythmic medications were administered to any horse at any stage. Catheter design and placement technique evolved throughout the study, with combined ultrasonography and pressure guidance proving most effective in achieving appropriate electrode placement. Results suggest TVEC, as applied in the present study, is a safe, effective, and realistic therapeutic option for equine AF.

Similarity Solutions for Strong Shocks in an Ideal Gas

The method of Lie group invariance is used to obtain a class of self‐similar solutions to the problem of shocks in an inhomogeneous gaseous medium and to characterize analytically the state‐dependent form of the medium ahead for which the problem is invariant and admits self‐similar solutions. Different cases of possible solutions, known in the literature, with a power law, exponential, or logarithmic shock paths are recovered as special cases depending on the arbitrary constants occurring in the expression for the generators of the transformation. Particular cases of plane rising shocks in an exponential medium and collapse of an imploding shock are worked out in detail. Numerical calculations have been performed to obtain the similarity exponents and the profiles of the flow variables, and comparison is made with the known results.

A trial of self-adhesive patch electrodes and hand-held paddle electrodes for external cardioversion of atrial fibrillation (MOBIPAPA)

External electrical cardioversion is the method of choice to terminate persistent atrial fibrillation. Whether the type of shock electrode affects cardioversion success is not known. We tested whether hand-held steel electrodes improve cardioversion outcome with monophasic or biphasic shocks when compared with adhesive patch electrodes. Two hundred and one consecutive patients with persistent atrial fibrillation (147 male, mean age 63+/-1 years, duration of atrial fibrillation 6.3+/-1 months) were randomly assigned to cardioversion using either a sinusoidal monophasic or a truncated exponential biphasic shock wave form. The first half of patients were cardioverted using adhesive patch electrodes, the second half using hand-held steel paddle electrodes, and all patients using an anterior-posterior electrode position. Paddle electrodes successfully cardioverted 100/104 patients (96%) and patch electrodes 85/97 patients (88%, P=0.04). This effect was comparable to that of biphasic shocks: biphasic shocks cardioverted 102/104 patients (98%) and monophasic shocks 83/97 patients (86%, P=0.001). A beneficial effect of paddle electrodes was observed for both shock wave forms. After cross-over from an ineffective monophasic to a biphasic shock, cardioversion was successful in 198/201 (98.5%) patients. Unsuccessful cardioversion after cross-over (3/201 patients) only occurred with patch electrodes (P=0.07). Hand-held paddle electrodes increase success of external cardioversion of atrial fibrillation in this trial. This increase is of similar magnitude as the increase in cardioversion success achieved with biphasic shocks. A combination of biphasic shocks, paddle electrodes, and an anterior-posterior electrode position renders outcome of external cardioversion almost always successful (104/104 patients in this trial).

Transvenous Electrical Cardioversion of Equine Atrial Fibrillation: Technical Considerations

Conventional treatment of equine atrial fibrillation (AF) involves administration of quinidine salts. Most uncomplicated cases respond to treatment, but pharmacologic cardioversion involves a range of adverse effects, and some horses are unable to tolerate medication. A study was undertaken to develop transvenous electrical cardioversion (TVEC) as an alternative treatment. Safety issues and catheter placement techniques with catheter-integrated cardioversion electrodes were investigated, and responses to shock application were evaluated. After the premortem catheterization of elective-euthanasia horses, no tissue abnormalities were detected at postmortem examination. To evaluate the response to the application of shocks and appropriate electrode positions, an electrical cardioversion of research horses in chronic AF was then attempted. After catheterization of the right atrium (RA) and pulmonary artery through the right jugular vein, horses were placed under general anesthesia. Biphasic, truncated exponential shock waves were delivered at incremental energies until cardioversion was achieved or until a maximum energy of 300 J was reached. Five treatment events were applied to 3 horses, with cardioversion achieved in one of the treatment events. No adverse effects of cardioversion attempts or general anesthesia were observed. The procedure was then applied to 8 client-owned horses, with cardioversion achieved in 7. No adverse responses to appropriately delivered shocks were observed. No antiarrhythmic medications were administered to any horse at any stage. Catheter design and placement technique evolved throughout the study, with combined ultrasonography and pressure guidance proving most effective in achieving appropriate electrode placement. Results suggest TVEC, as applied in the present study, is a safe, effective, and realistic therapeutic option for equine AF.

Efficacy of transthoracic cardioversion of atrial fibrillation using a biphasic, truncated exponential shock waveform at variable initial shock energies

Biphasic shocks are more effective than damped sine wave monophasic shocks for transthoracic cardioversion (CV) of atrial fibrillation (AF), but the optimal protocol for CV with biphasic shocks has not been defined. We conducted a prospective, randomized study of 120 consecutive patients with persistent AF to delineate the dose-response curve for CV of AF with a biphasic truncated exponential shock waveform and to identify clinical predictors of shock efficacy. Our data suggest that the initial shock energy for CV with this waveform should be 200 J if the patient weighs <90 kg and 360 J if the patient weighs >/=90 kg.

Fine-tuning in regulation of Clp protein content in Bacillus subtilis.

Clp-controlled proteolysis in Bacillus subtilis seems to play a substantial role, particularly under stress conditions. Calibrated Western blot analyses were used to estimate the approximate numbers of heat-inducible Clp molecules within a single cell. According to these numbers, the different Clp ATPases do not seem to compete for the proteolytic subunit ClpP. Coimmunoprecipitation experiments revealed the predicted specific ClpX-ClpP, ClpC-ClpP, and ClpE-ClpP interactions. ClpE and ClpX are rapidly degraded in wild-type cells during permanent heat stress but remained almost stable in a clpP mutant, suggesting ClpP-dependent degradation. In particular, ClpCP appeared to be involved in the degradation of the short-lived ClpE ATPase, indicating a negative "autoregulatory" circuit for this particular Clp ATPase at the posttranslational level. Analysis of the half-life of stress-inducible clp mRNAs during exponential growth and heat shock revealed precise regulation of the synthesis of each Clp protein at the posttranscriptional level as well to meet the needs of B. subtilis.

Automated external defibrillation versus manual defibrillation for prolonged ventricular fibrillation: Lethal delays of chest compressions before and after countershocks

Study objective We sought to determine whether the delays in chest compressions and defibrillation associated with an automated external defibrillator would adversely affect outcome compared with manual defibrillation in a swine model of out-of-hospital prolonged ventricular fibrillation. Methods After 8 minutes of untreated ventricular fibrillation, 16 swine (33±4 kg) were randomly assigned to automated external defibrillator defibrillation or manual defibrillation with the same biphasic truncated exponential waveform 150-J shock through the same type of pads. Defibrillation with the automated external defibrillator was performed as recommended by the manufacturer, and manual defibrillation was provided per American Heart Association Guidelines. The primary outcome measure was 24-hour survival with good neurologic outcome. Data are described as means±SD. Results None of 8 animals in the automated external defibrillator group survived for 24 hours, whereas 5 of 8 animals in the manual defibrillation group survived 24 hours, all with good neurologic outcome ( P=.027). The time interval from simulated defibrillator arrival to first compressions was 98±18 seconds in the automated external defibrillator group versus 68±15 seconds in the manual defibrillation group. In particular, the interval from first shock to first chest compressions was 46±18 seconds versus 22±16 seconds, respectively. The mean percentage of time that chest compressions were performed in the first minute after the first countershock was 15%±13% versus 40%±15%, respectively. As a result, return of spontaneous circulation within 5 minutes of simulated defibrillator arrival occurred in only 1 of 8 animals in the automated external defibrillator group versus 6 of 8 animals in the manual defibrillation group. Conclusion The longer delays in chest compressions with automated external defibrillator defibrillation versus manual defibrillation can worsen the outcome from prolonged ventricular fibrillation.

Pediatric transthoracic defibrillation: biphasic versus monophasic waveforms in an experimental model

Objectives: The purpose of this study was to determine and compare the efficacy of biphasic and monophasic waveforms in a porcine model of pediatric defibrillation. Background: The efficacy and safety of biphasic waveforms in children has not been established. Methods: We initially studied 27 piglets: 12 weighed 3–6 kg (‘infants’), and 15 weighed 7–12 kg (‘children’). Ventricular fibrillation (VF) was induced by rapid right ventricular pacing and maintained for 15 s. Transthoracic shocks of 7–100 J energy were given using monophasic (5 ms truncated exponential) and biphasic (5 ms positive, 5 ms negative pulse, truncated exponential) waveforms. A second study of four ‘infant’ and four ‘child’ piglets utilized the same protocol but with a 10 ms instead of 5 ms monophasic truncated exponential shock waveform compared with the 10 ms biphasic waveform. Results: For both biphasic and monophasic waveforms, shock success rate (termination of VF) rose steadily as energy was increased. In the first study in the ‘infant’ 3–6 kg group, the 10 ms biphasic waveforms were superior to 5 ms monophasic waveforms at 10, 20, and 30 J energies, and in the ‘child’ 7–12 kg group at 20 and 30 J energies ( P<0.05). High success rates (>80%) were achieved by 20 J (4 J/kg) biphasic waveform shocks in the ‘infant’ piglets and 30 J (3 J/kg) biphasic waveform shocks in the ‘child’ piglets. In the second study using a 10 ms monophasic waveform, we found similar results. Pulseless electrical activity occurred in two animals following biphasic shocks and in two animals following monophasic shocks. Conclusions: Biphasic waveforms proved superior to monophasic waveforms in both infant and child models. High success rates were achieved with low-energy biphasic shocks. Biphasic waveform defibrillation is a promising advance in pediatric resuscitation.