Unstable Shock Research Articles

An injectable subunit vaccine containing Elongation Factor Tu and Heat Shock Protein 70 partially protects American bison from Mycoplasma bovis infection.

Mycoplasma bovis (M. bovis) is the etiologic agent of high mortality epizootics of chronic respiratory disease in American bison (Bison bison). Despite the severity of the disease, no efficacious commercial vaccines have been licensed for the prevention of M. bovis infection in bison. Elongation factor thermal unstable (EFTu) and Heat Shock Protein 70 (Hsp70, DnaK) are highly conserved, constitutively expressed proteins that have previously been shown to provide protection against M. bovis infection in cattle. To assess the suitability of EFTu and Hsp70 as vaccine antigens in bison, the immune response to and protection conferred by an injectable, adjuvanted subunit vaccine comprised of recombinantly expressed EFTu and Hsp70 was evaluated. Vaccinates developed robust antibody and cellular immune responses against both EFTu and Hsp70 antigens. To assess vaccine efficacy, unvaccinated control and vaccinated bison were experimentally challenged with bovine herpes virus-1 (BHV-1) 4 days prior to intranasal infection with M. bovis. Vaccinated bison displayed reductions in joint infection, lung bacterial loads, and lung lesions compared to unvaccinated controls. Together, these results showed that this subunit vaccine reduced clinical disease and bacterial dissemination from the lungs in M. bovis challenged bison and support the further development of protein subunit vaccines against M. bovis for use in bison.

Early total care or damage control orthopaedics for major fractures ? Results of propensity score matching for early definitive versus early temporary fixation based on data from the trauma registry of the German Trauma Society (TraumaRegister DGU®)

PurposeDamage control orthopaedics (DCO) und early total care (ETC) are well-established strategies for managing severely injured patients. There is no definitive evidence of the superiority of DCO over ETC in polytrauma patients. We conducted this study to assess the probability of a polytraumatised patient undergoing DCO. In addition, the effect of DCO on complications and mortality was investigated.MethodsWe analysed data from 12,569 patients with severe trauma (Injury Severity Score ≥ 16) who were enrolled in the trauma registry of the German Trauma Society (TraumaRegister DGU®) from 2009 to 2016 and had undergone surgery for extremity or pelvic fractures. These patients were allocated to a DCO or an ETC group. We used the propensity score to identify factors supporting the use of DCO. For a comparison of mortality rates, the groups were stratified and matched on the propensity score.ResultsWe identified relevant differences between DCO and ETC. DCO was considerably more often associated with packed red blood cell (pRBC) transfusions (33.9% vs. 13.4%), catecholamine therapy (14.1% vs. 6.8%), lower extremity injuries (72.4% vs. 53.5%), unstable pelvic fractures (41.0% vs. 25.9%), penetrating injuries (2.8% vs. 1.5%), and shock (20.5% vs. 10.8%) and unconsciousness (23.7% vs. 16.3%) on admission. Based on the propensity score, patients with penetrating trauma, pRBC transfusions, unstable pelvic fractures, and lower extremity injuries were more likely to undergo DCO. A benefit of DCO such as reduced complications or reduced mortality was not detected.ConclusionWe could identify some parameters of polytrauma patients used in the trauma registry (Traumaregister DGU®), which led more likely to a DCO therapy. The propensity score did not demonstrate the superiority of DCO over ETC in terms of outcome or complications. It did not appear to adequately adjust for the variables used here. Definitive evidence for or against the use of DCO remains unavailable.

Response of shock train to fluctuating angle of attack in a scramjet inlet-isolator

Because a fluctuating incoming flow can affect with the unstable shock train movement, a numerical study was performed to analyze the effects. For the base flow with constant incoming and downstream flow conditions, the fundamental frequency and dominant role of the first separation shock are confirmed. The oscillations of the first separation shock are not always strengthened with an increase of the excitation amplitude at the resonant frequency. It is found that with a specific amplitude, the pressure peak in the shock wave/boundary layer interaction is enhanced, which can effectively suppress the upstream movement of the separation shock. However, a further increased excitation results in a wider oscillation region and greater pressure fluctuation. The non-negligible effects of the core flow enhance the oscillation of the separation shock.

Inferior Vena Cava/Abdominal Aorta Ratio as a Guide for Fluid Resuscitation.

Introduction:The fluid therapy is crucial in the treatment of critically ill children. Inadequate or excessive fluid resuscitation leads to increased mortality and morbidity, thus necessitating an accurate parameter for predicting fluid responsiveness when conducting fluid resuscitation. The inferior vena cava/abdominal aorta (IVC/Ao) ratio is suggested as a good guide for fluid resuscitation. However, the cutoff value for predicting fluid responsiveness in children has not been established. Is IVC/Ao ratio can be used to predict fluid responsiveness?Methods:The objective was to determine the accuracy and a cutoff value of IVC/Ao in predicting fluid responsiveness. A prospective cross-sectional study was conducted in the emergency room and the pediatric intensive care unit of the tertiary hospital from March to August 2017. We consecutively enrolled all critically ill children aged 1 month to 18 years' old who were hemodynamically unstable (shock). Measurements of IVC/Ao with ultrasound and stroke volume with ultrasound cardiac output monitor were obtained before and after fluid challenge.Results:Of 167 subjects enrolled in this study, only 58 subjects were included, most of whom were male (58.6%) and ranging in age from 1 to 11 months (32.8%). The mean IVC/Ao ratio before the fluid challenge in the fluid responsive group was 0.70 ± 0.053. The best cutoff of the IVC/Ao ratio is 0.675 with area under the curve 70.8% (95% confidence interval of 54.6%–87%), 75.7% sensitivity, and 61.9% specificity for predicting significant fluid responsiveness.Conclusion:The measurement of IVC/Ao is an accurate, sensitive, and specific parameter to predict fluid responsiveness. The best cut-off for the IVC/Ao ratio is 0.675.

Analysis of risk factors of early enteral nutrition intolerance in extremely severe burn patients

Objective: To explore the risk factors of early enteral nutrition intolerance in extremely severe burn patients. Methods: A retrospective case-control study was performed. From January 2018 to December 2020, seventy-six adult patients with extremely severe burns who met the inclusion criteria were admitted to Hwa Mei Hospital of University of Chinese Academy of Sciences, including 55 males and 21 females, aged (45±11) years with burns of 62% (52%, 82%) total body surface area. Depending on the patient's tolerance to early enteral nutrition, they were divided into tolerance group (47 patients) and intolerance group (29 patients), and their clinical data were statistically analyzed, including age, sex, body mass index (BMI), underlying disease, total burn area, full-thickness burn area, abbreviated burn severity index (ABSI) score, implementation of mechanical ventilation on the day of admission, stable shock state, vomiting before feeding. The following data were recorded including the onset time, duration length, and frequency of enteral nutrition intolerance of patients in intolerance group, and the number of operations, the length of hospitalization, the occurrence of sepsis within 2 weeks after injury, the outcome, as well as the serum hypersensitive C-reactive protein (hs-CRP), albumin, fasting blood glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and γ-glutamyl transpeptidase (γ-GT) on post burn day (PBD) 1, 5, 9, and 13 of patients in the two groups. Data were statistically analyzed with independent sample t test, Mann-Whitney U test, and chi-square test to screen the related factors of early enteral nutrition intolerance of the patients. Binary univariate and multivariate logistic regression analysis were used to analyze the independent risk factors of early enteral nutrition intolerance of the patients. Results: There were no statistically significant differences in age, sex, BMI, and percentage of underlying disease of patients between the two groups (P>0.05). The total burn area, full-thickness burn area, ABSI score, mechanical ventilation percentage on the day of admission, percentage of unstable shock period, percentage of vomiting before feeding of patients in intolerance group were significantly higher than those in tolerance group (Z=-4.559, -3.378, -4.067, χ2=18.375, 23.319, 8.339, P<0.01). In intolerance group, the onset time of intolerance was (9±4) d after injury, and the duration length was 4 (2, 6) d, with a total of 46 times occurred. Compared with tolerance group, the percentage of sepsis and mortality of patients in intolerance group were significantly higher within 2 weeks after injury (χ2=16.571, 12.665, P<0.01). The number of operation and length of hospitalization of patients in the two groups were similar (P>0.05); however the length of hospitalization of patients in the intolerance group was significantly more than that in tolerance group after excluding the death cases (Z=-2.266, P<0.05). On PBD 1, the level of fasting blood glucose and AST of patients in intolerance group were significantly higher than those in tolerance group (t=3.070, Z=-3.070, P<0.01). On PBD 5, the levels of hs-CRP, albumin, fasting blood-glucose, ALT, AST, and γ-GT of patients in the two groups were similar (P>0.05). On PBD 9, the level of hs-CRP of patients in intolerance group was significantly higher than that in tolerance group (t=2.836, P<0.01), and the levels of ALT and γ-GT of patients in intolerance group were significantly lower than those in tolerance group (Z=-3.932, -2.052, P<0.05 or P<0.01). On PBD 13, the level of hs-CRP of patients in intolerance group was significantly higher than that in tolerance group (t=3.794, P<0.01), and the levels of fasting blood glucose, ALT, and γ-GT of patients in intolerance group were significantly lower than those in tolerance group (t=-2.176, Z=-2.945, -2.250, P<0.05 or P<0.01). Binary univariate logistic regression analysis showed that total burn area, full-thickness burn area, ABSI score, implementation of mechanical ventilation on the day of admission, unstable shock period, vomiting before feeding, and fasting blood-glucose on PBD 1 of patients were related to early enteral nutrition intolerance (odds ratio=1.086, 1.052, 1.775, 9.167, 12.797, 10.125, 1.249, 95% confidence interval=1.045-1.129, 1.019-1.085, 1.320-2.387, 3.132-26.829, 4.199-39.000, 2.003-51.172, 1.066-1.464, P<0.01). Multivariate logistic regression analysis showed that the large total burn area, unstable shock period, vomiting before feeding, and high fasting blood-glucose on PBD 1 of patients were the independent risk factors of early enteral nutrition intolerance in patients (odds ratio=1.073, 6.390, 9.004, 1.246, 95% confidence interval=1.021-1.128, 1.527-26.734, 1.134-71.496, 1.007-1.540, P<0.05 or P<0.01). Conclusions: The percentage of early enteral nutrition intolerance is very high in extremely severe burn patients, which is closely related to poor prognosis. Large total burn area, vomiting before feeding, unstable shock phase, high fasting glucose on PBD 1 of patients are the independent risk factors for early enteral nutrition intolerance in extremely severe burn patients. The benefits and risks should be carefully evaluated before starting enteral nutrition in such patients, and early enteral nutrition should not be blindly pursued.

Investigation of the stability of transverse hydrogen injection combustion caused by plate vibration using the dynamic mode decomposition method

This article investigated the stability of transverse hydrogen injection combustion caused by the plate vibration. The finite-rate method is used to simulate the combustion. The unsteady flow field in the unstable phase of combustion is extracted. The unstable mode of the shock wave structure and the flame structure during the stage of combustion instability, the spatial and temporal characteristics of the dominant modes, as well as their stability are analyzed based on the dynamic mode decomposition (DMD) method. The results indicate that, according to the sequence of energy, the extracted first six orders modes of the shock wave structure and the flame structure have relatively low frequency with a negative growth rate and small numerical value, which presents a trend of weak convergence. The characteristics of the dominant structure of DMD modes show that the plate vibration has great effects on the reflected shock wave structure near the plate and on the upper wall surface, as well as the flame structure near the plate. According to the sequence of the mode energy and the growth rate, respectively, the extracted first six orders modes have relatively high frequency. Simultaneously, the structures of the modes extracted by the sequence of mode energy are more regular, while those extracted by the sequence of growth rate are more disorderly. The unstable shock wave structure is mainly manifested by the reflected shock wave in the vibration region and the shock wave structure reflected by the upper wall surface. The unstable flame structure is mainly concentrated near the vibration region and downstream areas.

Stability of two-fluid partially ionized slow-mode shock fronts

ABSTRACT A magnetohydrodynamic (MHD) shock front can be unstable to the corrugation instability, which causes a perturbed shock front to become increasingly corrugated with time. An ideal MHD parallel shock (where the velocity and magnetic fields are aligned) is unconditionally unstable to the corrugation instability, whereas the ideal hydrodynamic (HD) counterpart is unconditionally stable. For a partially ionized medium (for example, the solar chromosphere), both HD and MHD species coexist and the stability of the system has not been studied. In this paper, we perform numerical simulations of the corrugation instability in two-fluid partially ionized shock fronts to investigate the stability conditions, and compare the results to HD and MHD simulations. Our simulations consist of an initially steady two-dimensional parallel shock encountering a localized upstream density perturbation. In MHD, this perturbation results in an unstable shock front and the corrugation grows with time. We find that for the two-fluid simulation, the neutral species can act to stabilize the shock front. A parameter study is performed to analyse the conditions under which the shock front is stable and unstable. We find that for very weakly coupled or very strongly coupled partially ionized system the shock front is unstable, as the system tends towards MHD. However, for a finite coupling, we find that the neutrals can stabilize the shock front, and produce new features including shock channels in the neutral species. We derive an equation that relates the stable wavelength range to the ion-neutral and neutral-ion coupling frequencies and the Mach number. Applying this relation to umbral flashes gives an estimated range of stable wavelengths between 0.6 and 56 km.

Implosion dynamics of triple-nozzle gas-puff z pinches on COBRA

Experiments on the 1-MA, 220-ns COBRA generator at Cornell University [J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)] were conducted to provide detailed measurements of structured cylindrical gas-puff z pinches. In the experiments, a 7 cm diameter triple-nozzle gas valve assembly with concentric outer and inner annular nozzles and a central gas jet initialize the z-pinch load with various working gases, radial density profiles, and externally applied axial magnetic fields. Planar laser-induced fluorescence provides a measure of the initial neutral gas density of the load, while three-frame laser shearing interferometry and multi-frame extreme ultraviolet (XUV) cameras reveal the formation and propagation of a magneto-Rayleigh–Taylor (MRT) unstable shock layer. Implosion trajectories are compared to simple, experimentally informed models and found to be in good agreement. Differences in the structure of the accelerating plasma sheath and evolution of the MRT instability are observed for different gas species and axial magnetic field strengths, correlating with differences in pinch uniformity and x-ray emission. The average instability growth is compared to linear MRT theory predictions using the instantaneous acceleration of the best-fit implosion models and characteristic instability wavelength, with the effective Atwood number and seed perturbation size as fit parameters. For high density argon center jets, ionization prior to the arrival of the imploding plasma sheath suggests a heating mechanism consistent with photoionization by XUV self-emission.

Bilateral Alive Tubal Ectopic Pregnancy and its Management

Ectopic pregnancy is an important cause of maternal mortality. Bilateral tubal pregnancies are rare; The reported incidence is only 1 in 200 000 pregnancies. Detecting bilateral tubal ectopic pregnancy is urgent because of the associated morbidity and mortality1 The management of bilateral tubal ectopic pregnancies may be medical or surgical, and depends to a large extent on the state of the fallopian tubes at presentation. The main challenge being to identify and treat as early as possible .Risk factors for ectopic pregnancy comprises of previous ectopic pregnancy, tubal damage secondary to tubal surgery, Adhesions secondary to previous laparotomies, chronic infection and Endometriosis. Other nonspecific factors that might contribute to an increased risk are cigarette smoking, age more than 35 years, and use of Assisted reproductive technology( ovulation induction). Presentation to the health care services may varies widely from mild vaginal bleeding and lower back and abdominal pain to clinically unstable condition and shock due to ruptured ectopic and life threatening internal bleeding.

Continuum nonlinear dynamics of unstable shock waves induced by structural phase transformations in iron

Iron is the predominant metal in the interior of the Earth and other rocky planets and has also received substantial consideration in materials science and engineering due to its technological importance. Here, a finite deformation continuum framework for combining nonlinear elasto-viscoplasticity with multivariant phase-field theory is used to investigate shock-induced polymorphic phase transitions in single-crystal iron. A large number of low- and high-pressure variants with explicit anisotropic pressure-dependent stiffnesses are included with respect to the point-symmetry groups of cubic and hexagonal crystal lattices. Using the element-free Galerkin method with high-performance computing resources, the three-dimensional nonlinear calculations accurately describe some important features reported by the experimental literature, and strongly complement our understanding of the phase-change dynamics in iron at larger time and length scales than hitherto explored by molecular dynamics simulations in the last two decades. The numerical model is able to reproduce unstable shock waves (which break up into elastic, plastic and phase-transition waves), providing new stress-informed insights into the coupling between the high strain-rate plasticity and microstructure evolution during the displacive phase transitions. The analyses of time-position diagrams indicate that the prompt plastic relaxation to a nearly hydrostatic state from uniaxial shock-compression is responsible for the peculiar multiphase microstructure with an unexpected gradient selection of high-pressure variants behind the phase-transition wave front. The existence of two-zone sequential sets of “release” and “reload” variants that results from a heterogeneous nucleation instability leads to a specific microstructural fingerprint of the nonlinear dynamics of phase transitions, thus offering novel guidelines for future experimental diagnostics of shock wave propagation in iron.

Application of venous return curve in hemodynamic intervention of shock patients

In the cardiac output (CO) and venous return (VR) balance theory proposed by Guyton in the 1950s, the right atrial pressure (Pra) was used as the dependent variable, and the VR and right cardiac function curves were recorded simultaneously. The intersection of the two curves is the current circulating blood flow under the Pra at this moment. In patients with hemodynamically unstable shock, the primary treatment goal is to restore circulating blood volume and tissue perfusion with primary methods including fluid resuscitation and the use of vasoactive drugs. This review described the dynamic evolution of VR curve in hemodynamic intervention of shock patients and the changes in physiological indicators such as mean systemic filling pressure (Pmsf), venous resistance (Rv), and stressed volume (Vs), in order to more accurately interpret changes in hemodynamic parameters and guide the clinical treatment of shock from a goal-oriented perspective.

Instability of relativistic shock waves: Numerical study on the basis of model equation of state

The behavior of unstable relativistic shock waves is studied with the use of specially developed model equation of state (EOS). The EOS admits the Taub-Hugoniot adiabats with segments on which the criteria of the relativistic shock wave stability are violated. The instability segments are overlapped by the regions with ambiguous representation of the shock-wave discontinuity. The simulations are fulfilled for L < − 1 and L > (1 + 2M + v0v1)/(1 − v0v1) instability conditions, where L is relativistic analog of Dyakov parameter, M is post-shock Mach number, v0 and v1 are pre- and post-shock velocities in the shock attached reference frame. Under the condition of ambiguous representation of the shock-wave discontinuity in the former case the splitting of the unstable shock with formation of a composite compression wave with Lorentz factor dependent structure is observed. It is shown that the latter condition leads to two-dimensional non-stationary solutions characterized by presence of strong transverse waves.

A minimal hyperbolic system for unstable shock waves

We present a computational analysis of a 2×2 hyperbolic system of balance laws whose solutions exhibit complex nonlinear behavior. Traveling-wave solutions of the system are shown to undergo a series of bifurcations as a parameter in the model is varied. Linear and nonlinear stability properties of the traveling waves are computed numerically using accurate shock-fitting methods. The model may be considered as a minimal hyperbolic system with chaotic solutions and can also serve as a stringent numerical test problem for systems of hyperbolic balance laws.

Methanol Poisoning with Fatality- Case Series in Dhaka Medical College Hospital in Bangladesh

Background: Adulterated methanol is highly toxic and leads to severe metabolic acidosis and blindness and mortality is very high if not treated with specific antidote. The time of ingestion and severity of illness is very short and comprehensive quick assessment and care is crucial for survival of patient. The selective antidote Fomepizole is not available in Bangladesh and pure intravenous ethanol is also out of reach in health care facility. The oral ethanol has its legislative regulation. Occasional clusters of severe methanol poisoning leading to fatality has been observed in recent years in Bangladesh. Here is a case series of 8 cases of adulterated methanol poisoning in a tertiary care hospital with lethality. Results and discussion: From November 2012 to January, 2013, in sphere of 3 months medicine units of Dhaka Medical College Hospital (DMCH) experienced 8 cases of methanol poisoning with fatality. Six patient presented in unconscious states within 3 to 7 h of consuming methanol while two patient presented within 48 h. All of them had gastrointestinal toxicity with variable episodes of vomiting. Three patients presented with visual impairment while only two out of eight had normal ophthalmoscopy. Respiratory distress was uniformly found in all patients before unstable profound shock. Blood ethanol level was not performed in any patient due to lack of available facility. Seven patients received only supportive measures ranging from steroids to sodium bi carbonate while one patient presented in severe toxicity and died quickly before any supportive measures. Antidote was not prescribed in any patient in the form of fomepizole or intravenous or oral ethanol. Conclusion: The judicious use of antidote even in the form of oral ethanol and folinic acid can save the precious life. A national guideline should be uniformly practiced by the physicians to combat the catastrophic methanol poisoning in Bangladesh.

Bow-shock instability induced by Helmholtz resonator-like feedback in slipstream

Bow-shock instability has been experimentally observed in a low-γ flow. To clarify its mechanism, a parametric study was conducted with three-dimensional numerical simulations for specific heat ratio γ and Mach number M. A critical boundary of the instability was found in the γ-M parametric space. The bow shock tends to be unstable with low γ and high M, and the experimental demonstration was designed based on this result. The experiments were conducted with the ballistic range of the single-stage powder gun mode using HFC-134a of γ = 1.12 at Mach 9.6. Because the deformation of the shock front was observed in a shadowgraph image, the numerical prediction was validated to some extent. The theoretical estimation of vortex formation in a curved shock wave indicates that the generated vorticity is proportional to the density ratio across the shock front and that the critical density ratio can be predicted as ∼10. A strong slipstream from the surface edge generates noticeable acoustic waves because it can be deviated by the upstream flow. The acoustic waves emitted by synchronizing the vortex formation can propagate upstream and may trigger bow-shock instability. This effect should be emphasized in terms of unstable shock formation around an edged flat body.

Plasma physics. Stochastic electron acceleration during spontaneous turbulent reconnection in a strong shock wave.

Explosive phenomena such as supernova remnant shocks and solar flares have demonstrated evidence for the production of relativistic particles. Interest has therefore been renewed in collisionless shock waves and magnetic reconnection as a means to achieve such energies. Although ions can be energized during such phenomena, the relativistic energy of the electrons remains a puzzle for theory. We present supercomputer simulations showing that efficient electron energization can occur during turbulent magnetic reconnection arising from a strong collisionless shock. Upstream electrons undergo first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. These results shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves.

Shocking! Particle accelerators in space

Plasma Physics The acceleration of charged particles to high energies has been a major mystery, with a number of competing theories based on plasma physics. Many include the concept of turbulence, but with different roles. For example, shock-based theories emphasize the importance of turbulence developed from an unstable shock layer, whereas turbulent reconnection theories emphasize interactions of multiple reconnection sites. Matsumoto et al. present results of a large particle-in-cell simulation and examine how electrons are accelerated in the transition layer of a fast nonrelativistic shock (see the Perspective by Ji and Zweibel). Surprisingly, they find that when the shock is strong enough, charged particles (electrons in this case) are efficiently accelerated by turbulent reconnection within a turbulent shock layer containing multiscale structures. Science , this issue p. [974][1]; see also p. [944][2] [1]: /lookup/doi/10.1126/science.1260168 [2]: /lookup/doi/10.1126/science.aaa3036

Ignition Transients in a Scramjet Engine with Air Throttling Part 1: Nonreacting Flow

Achieving efficient ignition and stable combustion in a high-speed environment has long been a serious concern in the development of scramjet engines. In the engine startup stage, the low chamber pressure and unsettled fuel–air mixing tend to blow off the flame, even if a flameholding device such as a cavity is employed. The problem may be circumvented by modulating the flow structures in the isolator and combustor through air throttling downstream of the flameholder. In experiments, compressed air is introduced in a controlled manner into the combustor to generate a precombustion shock train in the isolator. The resultant increases in the temperature and pressure of the airstream in the combustor, along with the decrease in the flow velocity, lead to smooth and reliable ignition. The incidentally formed separated flows adjacent to the combustor sidewall improve fuel–air mixing as a result of enhanced flow distortion and increased residence time. Because insufficient reaction heat release often leads to an unstable shock train, and exceedingly large heat release may cause severe flow spillage or even inlet unstart, dynamic optimization of the throttling operation is needed to ensure the creation of flow conditions conducive to efficient ignition. The present work establishes an integrated theoretical/numerical framework, within which the influences of all known effects on the engine ignition transient and flame development are studied systematically. Part 1 of the study focuses on nonreacting flow development and fuel–air mixing under the influence of air throttling.

Risk Stratification for Long-Term Mortality After Percutaneous Coronary Intervention

A simple risk score to predict long-term mortality after percutaneous coronary intervention (PCI) using preprocedural risk factors is currently not available. In this study, we created one by simplifying the results of a Cox proportional hazards model. A total of 11,897 patients who underwent PCI from October through December 2003 in New York State were randomly divided into derivation and validation samples. Patients' vital statuses were tracked using the National Death Index through the end of 2008. A Cox proportional hazards model was fit to predict death after PCI using the derivation sample, and a simplified risk score was created. The Cox model identified 12 separate risk factors for mortality including older age, extreme body mass indexes, multivessel disease, a lower ejection fraction, unstable hemodynamic state or shock, several comorbidities (cerebrovascular disease, peripheral vascular disease, congestive heart failure, chronic obstructive pulmonary disease, diabetes mellitus, and renal failure), and a history of coronary artery bypass graft surgery. The C statistics of this model when applied to the validation sample were 0.787, 0.785, and 0.773 for risks of death within 1, 3, and 5 years after PCI, respectively. In addition, the point-based risk score demonstrated good agreement between patients' observed and predicted risks of death. A simple risk score created from a more complicated Cox proportional hazards model can be used to accurately predict a patient's risk of long-term mortality after PCI.

Experimental study on of dynamics of particles in the flow filed with intensive gradients

The dynamic response of particles in hyper/supersonic flow is one of the key points of techniques using tracer particles, such as particle image velocimetry (PIV). In the literature, it is validated by the single oblique shock response testing. However, particles suffer intensive variation of velocity, density and viscosity, when used to trace and measure the complex flow field in the high speed vehicle engine. To test and validate the dynamics of particles in such a flow field with intensive gradient, in this paper we conduct a series experiments dealing with this issue. The study includes the measurements on the velocity field at the exit of the wind tunnel nozzle to testify the performance of PIV system, the measurements on the oblique shock response of particles in Mach 4.2 and Mach 3.0 supersonic flows over a 10° wedge and a 15° wedge respectively, and measurements on the double oblique shock response of particles in the flow field which is designed to simulate the flow field inside the vehicle engine with gradients and without the influence of expansion wave. Based on the particle dynamic models, the relaxation time, relaxation distance, Stokes numbers of different cases can be gained. And the influence of unstable shock oscillation is analyzed and revised based on image method and statistic analysis. It can be found that the relaxation time and distance increase with the Mach number, given the same wedge degree. However, with the same incoming Mach number, the relaxation time and distance drop when the wedge degree increases. Due to the intensive variation of Reynolds number and viscosity, the results show that in a certain extent particles lose their following ability by 5.7%, while its Stokes number increases by 1%. In the flow condition herein, the Stokes number still meets the requirement of supersonic flow. However the decrease of particle following ability is worth being concerned, especially when using particles in the complex flow field with more intensive gradients.