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Sample records for advanced vasodilatory shock

  1. Antidiuretic hormone replacement therapy to prevent or ameliorate vasodilatory shock.

    PubMed

    Singh Ranger, Gurpreet

    2002-09-01

    Vasodilatory shock is a syndrome with high mortality. It is becoming evident that depletion of antidiuretic hormone (ADH) after cardiac surgery or during sepsis plays an important role in the pathogenesis of this condition. Established vasodilatory shock responds well to exogenous ADH infusion. It is possible that preventing ADH depletion at an earlier stage may abrogate the onset of vasodilatory shock, or at least reduce its severity. This paper examines the evidence supporting this concept, and the potential areas of concern in considering this particular type of hormone replacement therapy. PMID:12208165

  2. Exogenous Vasopressin-Induced Hyponatremia in Patients With Vasodilatory Shock: Two Case Reports and Literature Review.

    PubMed

    Salazar, Miguel; Hu, Bee Bee; Vazquez, Joyce; Wintz, Ruth L; Varon, Joseph

    2015-07-01

    Vasopressin has gained wide support as an adjunct vasopressor in patients with septic shock. This agent exerts its vasoconstriction effects through smooth muscle V1 receptors and also has antidiuretic activity via renal V2 receptors. This interaction with the renal V2 receptors results in the integration of aquaporin 2 channels in the apical membrane of the renal collecting duct leading to free water reabsorption. Thus, water intoxication with subsequent hyponatremia, although rare, is a potentially serious side effect of exogenous vasopressin administration. We present 2 patients who developed hyponatremia within hours of initiation of vasopressin infusion. Extensive diuresis followed its discontinuation with subsequent normalization of serum sodium. One of the patients required the use of hypertonic saline for more rapid normalization of serum sodium due to concerns for potential seizure activity. A review of the literature relevant to the incidence of vasopressin-induced hyponatremia is provided as well as discussion on additional factors relevant to septic shock that should be considered when determining the relative risk of hyponatremia in patients receiving vasopressin. PMID:24106070

  3. Non-Adrenergic Vasopressors in Patients with or at Risk for Vasodilatory Shock. A Systematic Review and Meta-Analysis of Randomized Trials

    PubMed Central

    Belletti, Alessandro; Musu, Mario; Silvetti, Simona; Saleh, Omar; Pasin, Laura; Monaco, Fabrizio; Hajjar, Ludhmila A.; Fominskiy, Evgeny; Finco, Gabriele; Zangrillo, Alberto; Landoni, Giovanni

    2015-01-01

    Introduction Hypotensive state is frequently observed in several critical conditions. If an adequate mean arterial pressure is not promptly restored, insufficient tissue perfusion and organ dysfunction may develop. Fluids and catecholamines are the cornerstone of critical hypotensive states management. Catecholamines side effects such as increased myocardial oxygen consumption and development of arrhythmias are well known. Thus, in recent years, interest in catecholamine-sparing agents such as vasopressin, terlipressin and methylene blue has increased; however, few randomized trials, mostly with small sample sizes, have been performed. We therefore conducted a meta-analysis of randomized trials to investigate the effect of non-catecholaminergic vasopressors on mortality. Methods PubMed, BioMed Central and Embase were searched (update December 31st, 2014) by two independent investigators. Inclusion criteria were: random allocation to treatment, at least one group receiving a non-catecholaminergic vasopressor, patients with or at risk for vasodilatory shock. Exclusion criteria were: crossover studies, pediatric population, non-human studies, studies published as abstract only, lack of data on mortality. Studied drugs were vasopressin, terlipressin and methylene blue. Primary endpoint was mortality at the longest follow-up available. Results A total of 1,608 patients from 20 studies were included in our analysis. The studied settings were sepsis (10/20 studies [50%]), cardiac surgery (7/20 [35%]), vasodilatory shock due to any cause (2/20 [19%]), and acute traumatic injury (1/20 [5%]). Overall, pooled estimates showed that treatment with non-catecholaminergic agents improves survival (278/810 [34.3%] versus 309/798 [38.7%], risk ratio = 0.88, 95% confidence interval = 0.79 to 0.98, p = 0.02). None of the drugs was associated with significant reduction in mortality when analyzed independently. Results were not confirmed when analyzing studies with a low risk of bias

  4. Shock-loading response of advanced materials

    NASA Astrophysics Data System (ADS)

    Gray, G. T., III

    1993-05-01

    Advanced materials, such as composites (metal, ceramic, or polymer-matrix), intermetallics, foams (metallic or polymeric-based), laminated materials, and nanostructured materials are receiving increasing attention because their properties can be custom tailored specific applications. The high-rate/impact response of advanced materials is relevant to a broad range of service environments such as the crashworthiness of civilian/military vehicles, foreign-object-damage in aerospace, and light-weight armor. Increased utilization of these material classes under dynamic loading conditions requires an understanding of the relationship between high-rate/shock-wave response as a function of microstructure if we are to develop models to predict material behavior. In this paper, the issues relevant to defect generation, storage, and the underlying physical basis needed in predictive models for several advanced materials are reviewed.

  5. Advances in Monitoring and Management of Shock

    PubMed Central

    Mtaweh, Haifa; Trakas, Erin V.; Su, Erik; Carcillo, Joseph A.; Aneja, Rajesh K.

    2013-01-01

    Synopsis Shock continues to be the proximate cause of death for many childhood diseases and imposes a significant burden. Early recognition and treatment of pediatric shock, regardless of etiology, decreases mortality and improves outcome. In addition to the conventional parameters (e.g., heart rate (HR), systolic blood pressure (SBP), urine output (UOP), and central venous pressure (CVP)), biomarkers and non-invasive methods of measuring cardiac output are now available to monitor and treat shock. In this article, we emphasize how fluid resuscitation is the cornerstone of shock resuscitation although the choice and amount of fluid may vary based on the etiology of shock. Other emerging treatments for shock i.e., temperature control, extracorporeal membrane oxygenation (ECMO)/Ventricular Assist Devices (VAD) are also discussed briefly in this article. PMID:23639660

  6. Advances in NIF Shock Timing Experiments

    NASA Astrophysics Data System (ADS)

    Robey, Harry

    2012-10-01

    Experiments are underway to tune the shock timing of capsule implosions on the National Ignition Facility (NIF). These experiments use a modified cryogenic hohlraum geometry designed to precisely match the performance of ignition hohlraums. The targets employ a re-entrant Au cone to provide optical access to multiple shocks as they propagate in the liquid deuterium-filled capsule interior. The strength and timing of all four shocks is diagnosed with VISAR (Velocity Interferometer System for Any Reflector). Experiments are now routinely conducted in a mirrored keyhole geometry, which allows for simultaneous diagnosis of the shock timing at both the hohlraum pole and equator. Further modifications are being made to improve the surrogacy to ignition hohlraums by replacing the standard liquid deuterium (D2) capsule fill with a deuterium-tritium (DT) ice layer. These experiments will remove any possible surrogacy difference between D2 and DT as well as incorporate the physics of shock release from the ice layer, which is absent in current experiments. Experimental results and comparisons with numerical simulation are presented.

  7. Advances in fluid resuscitation of hemorrhagic shock

    PubMed Central

    Tremblay, Lorraine N.; Rizoli, Sandro B.; Brenneman, Frederick D.

    2001-01-01

    The optimal fluid for resuscitation in hemorrhagic shock would combine the volume expansion and oxygen-carrying capacity of blood without the need for cross-matching or the risk of disease transmission. Although the ideal fluid has yet to be discovered, current options are discussed in this review, including crystalloids, colloids, blood and blood substitutes. The future role of blood substitutes is not yet defined, but the potential advantages in trauma or elective surgery may prove to be enormous. PMID:11407826

  8. MP4, a vasodilatory PEGylated hemoglobin.

    PubMed

    Cole, Russell H; Vandegriff, Kim D

    2011-01-01

    A vasodilatory hemoglobin (Hb)-based O(2) carrier (HBOC) has been developed by surface conjugation polyethylene glycol to tetrameric human Hb (MP4, Sangart, San Diego). Because the NO-binding kinetics of MP4 are similar to vasoconstrictive HBOCs, we propose that the decoupling of NO scavenging from vascular response is a consequence of MP4's high O(2) affinity (p50 = 5 mmHg) and unique surface chemistry. The release of ATP from erythrocytes is vasodilatory and the application of a high O(2) affinity HBOC minimizes ATP interference with intravascular ATP signaling. A second potential mechanism of action for MP4 involves the surface conjugation of polyethylene glycol (PEG) to tetrameric human Hb. It has been shown that the addition of unconjugated high molecular weight (Mw) PEG to cultured lung endothelial cells causes an immediate and significant reduction in endothelial permeability; an effect opposite to that of endothelial agonists such as cell-free Hb. It appears that some of the benefits of the PEG-endothelium interaction are carried onto molecules such as PEGylated Hb and PEGylated albumin, as demonstrated by favorable hemodynamic responses in vivo. PEGylation of ß93 cysteine residues, as in MP4, has also been reported to increase the nitrite reductase activity of Hb and enhance conversion of endogenous nitrite to bioactive NO. PMID:21445773

  9. Advances in shock timing experiments on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R.; Ross, J. S.; LePape, S.; Ralph, J. E.; Hohenberger, M.; Dewald, E. L.; Berzak Hopkins, L.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Boehly, T. R.; Nikroo, A.; Landen, O. L.; Edwards, M. J.

    2016-03-01

    Recent advances in shock timing experiments and analysis techniques now enable shock measurements to be performed in cryogenic deuterium-tritium (DT) ice layered capsule implosions on the National Ignition Facility (NIF). Previous measurements of shock timing in inertial confinement fusion (ICF) implosions were performed in surrogate targets, where the solid DT ice shell and central DT gas were replaced with a continuous liquid deuterium (D2) fill. These previous experiments pose two surrogacy issues: a material surrogacy due to the difference of species (D2 vs. DT) and densities of the materials used and a geometric surrogacy due to presence of an additional interface (ice/gas) previously absent in the liquid-filled targets. This report presents experimental data and a new analysis method for validating the assumptions underlying this surrogate technique.

  10. Vasopressin deficiency and vasodilatory state in end-stage liver disease

    PubMed Central

    Wagener, Gebhard; Kovalevskaya, Galina; Minhaz, Moury; Mattis, Fallon; Emond, Jean C.; Landry, Donald W.

    2010-01-01

    1. Objectives Relative vasopressin deficiency, a contributor to vasodilatory septic shock may also be a cause of the vasodilatory state in liver disease. This study assesses endogenous vasopressin levels in patients with liver disease and their hemodynamic response to exogenous vasopressin. 2. Design Prospective, observational study 3. Setting Single center, tertiary hospital 4. Participants Human subjects undergoing liver transplantation or major surgery 5. Interventions Vasopressin levels were measured in 28 patients with liver disease undergoing liver transplantation and 7 control patients with normal liver function. Additionally intravenous vasopressin was given to 20 liver transplant recipients and the hemodynamic response was observed. 6. Measurements and Main Results Patients with liver disease had significantly lower baseline vasopressin levels than controls (19.3 +/− 27.1 pg/mL versus 50.9 +/− 36.7 pg/mL, p=0.015). Patients with low vasopressin levels (• 20 pg/mL) were more likely to have low baseline mean blood pressure (• 80 mm Hg) than patients with high vasopressin levels (11 of 16 vs. 0 of 4, p=0.013). Systemic vascular resistance increased by 33% three minutes after intravenous vasopressin. Thirteen of 16 patients with low vasopressin levels compared to one of four patients with high vasopressin levels responded to exogenous vasopressin with an increase of mean blood pressure by more than 20% (p=0.028). 7. Conclusions Patients with liver disease have lower vasopressin levels than controls and respond with a brisk vasoconstrictor response to exogenous vasopressin. Relative endogenous vasopressin deficiency may therefore contribute to vasodilatory shock in liver disease similar to what has been observed in septic shock PMID:21126886

  11. The Advanced Composition Explorer Shock Database and Application to Particle Acceleration Theory

    NASA Technical Reports Server (NTRS)

    Parker, L. Neergaard; Zank, G. P.

    2015-01-01

    The theory of particle acceleration via diffusive shock acceleration (DSA) has been studied in depth by Gosling et al. (1981), van Nes et al. (1984), Mason (2000), Desai et al. (2003), Zank et al. (2006), among many others. Recently, Parker and Zank (2012, 2014) and Parker et al. (2014) using the Advanced Composition Explorer (ACE) shock database at 1 AU explored two questions: does the upstream distribution alone have enough particles to account for the accelerated downstream distribution and can the slope of the downstream accelerated spectrum be explained using DSA? As was shown in this research, diffusive shock acceleration can account for a large population of the shocks. However, Parker and Zank (2012, 2014) and Parker et al. (2014) used a subset of the larger ACE database. Recently, work has successfully been completed that allows for the entire ACE database to be considered in a larger statistical analysis. We explain DSA as it applies to single and multiple shocks and the shock criteria used in this statistical analysis. We calculate the expected injection energy via diffusive shock acceleration given upstream parameters defined from the ACE Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM) data to construct the theoretical upstream distribution. We show the comparison of shock strength derived from diffusive shock acceleration theory to observations in the 50 keV to 5 MeV range from an instrument on ACE. Parameters such as shock velocity, shock obliquity, particle number, and time between shocks are considered. This study is further divided into single and multiple shock categories, with an additional emphasis on forward-forward multiple shock pairs. Finally with regard to forwardforward shock pairs, results comparing injection energies of the first shock, second shock, and second shock with previous energetic population will be given.

  12. The Advanced Composition Explorer Shock Database and Application to Particle Acceleration Theory

    NASA Technical Reports Server (NTRS)

    Parker, L. Neergaard; Zank, G. P.

    2015-01-01

    The theory of particle acceleration via diffusive shock acceleration (DSA) has been studied in depth by Gosling et al. (1981), van Nes et al. (1984), Mason (2000), Desai et al. (2003), Zank et al. (2006), among many others. Recently, Parker and Zank (2012, 2014) and Parker et al. (2014) using the Advanced Composition Explorer (ACE) shock database at 1 AU explored two questions: does the upstream distribution alone have enough particles to account for the accelerated downstream distribution and can the slope of the downstream accelerated spectrum be explained using DSA? As was shown in this research, diffusive shock acceleration can account for a large population of the shocks. However, Parker and Zank (2012, 2014) and Parker et al. (2014) used a subset of the larger ACE database. Recently, work has successfully been completed that allows for the entire ACE database to be considered in a larger statistical analysis. We explain DSA as it applies to single and multiple shocks and the shock criteria used in this statistical analysis. We calculate the expected injection energy via diffusive shock acceleration given upstream parameters defined from the ACE Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM) data to construct the theoretical upstream distribution. We show the comparison of shock strength derived from diffusive shock acceleration theory to observations in the 50 keV to 5 MeV range from an instrument on ACE. Parameters such as shock velocity, shock obliquity, particle number, and time between shocks are considered. This study is further divided into single and multiple shock categories, with an additional emphasis on forward-forward multiple shock pairs. Finally with regard to forward-forward shock pairs, results comparing injection energies of the first shock, second shock, and second shock with previous energetic population will be given.

  13. Shock

    MedlinePlus

    ... problems) Hypovolemic shock (caused by too little blood volume) Anaphylactic shock (caused by allergic reaction) Septic shock ( ... as heart attack or heart failure ) Low blood volume (as with heavy bleeding or dehydration ) Changes in ...

  14. Shock

    MedlinePlus

    ... Emergencies A-Z Share this! Home » Emergency 101 Shock Shock is a serious, often life-threatening medical condition ... of death for critically ill or injured people. Shock results when the body is not getting enough ...

  15. Antioxidant and vasodilatory effects of blackberry and grape wines.

    PubMed

    Mudnic, Ivana; Budimir, Danijela; Modun, Darko; Gunjaca, Grgo; Generalic, Ivana; Skroza, Danijela; Katalinic, Visnja; Ljubenkov, Ivica; Boban, Mladen

    2012-03-01

    In contrast to the well-described various biological effects of grape wines, the potential effects of commonly consumed blackberry wine have not been studied. We examined in vitro antioxidant and vasodilatory effects of four blackberry wines and compared them with the effects of two red and two white grape wines. Although some blackberry wines had lower total phenolic content relative to the red grape wines, their antioxidant capacity was stronger, which may be related to a higher content of non-flavonoid compounds (most notably gallic acid) in blackberry wines. Although maximal vasodilation induced by blackberry wines was generally similar to that of red wines, blackberry wines were less potent vasodilators. Vasodilatory activity of all wines, in addition to their flavonoid and total phenolic content, was most significantly associated with their content of anthocyanins. No association of vasodilation with any individual polyphenolic compound was found. Our results indicate the biological potential of blackberry wines, which deserves deeper scientific attention. PMID:22082099

  16. Antioxidant and Vasodilatory Effects of Blackberry and Grape Wines

    PubMed Central

    Mudnic, Ivana; Budimir, Danijela; Modun, Darko; Gunjaca, Grgo; Generalic, Ivana; Skroza, Danijela; Katalinic, Visnja; Ljubenkov, Ivica

    2012-01-01

    Abstract In contrast to the well-described various biological effects of grape wines, the potential effects of commonly consumed blackberry wine have not been studied. We examined in vitro antioxidant and vasodilatory effects of four blackberry wines and compared them with the effects of two red and two white grape wines. Although some blackberry wines had lower total phenolic content relative to the red grape wines, their antioxidant capacity was stronger, which may be related to a higher content of non-flavonoid compounds (most notably gallic acid) in blackberry wines. Although maximal vasodilation induced by blackberry wines was generally similar to that of red wines, blackberry wines were less potent vasodilators. Vasodilatory activity of all wines, in addition to their flavonoid and total phenolic content, was most significantly associated with their content of anthocyanins. No association of vasodilation with any individual polyphenolic compound was found. Our results indicate the biological potential of blackberry wines, which deserves deeper scientific attention. PMID:22082099

  17. Shock wave lithotripsy: advances in technology and technique

    PubMed Central

    Lingeman, James E.; McAteer, James A.; Gnessin, Ehud; Evan, Andrew P.

    2010-01-01

    Shock wave lithotripsy (SWL) is the only noninvasive method for stone removal. Once considered as a primary option for the treatment of virtually all stones, SWL is now recognized to have important limitations that restrict its use. In particular, the effectiveness of SWL is severely limited by stone burden, and treatment with shock waves carries the risk of acute injury with the potential for long-term adverse effects. Research aiming to characterize the renal response to shock waves and to determine the mechanisms of shock wave action in stone breakage and renal injury has begun to suggest new treatment strategies to improve success rates and safety. Urologists can achieve better outcomes by treating at slower shock wave rate using a step-wise protocol. The aim is to achieve stone comminution using as few shock waves and at as low a power level as possible. Important challenges remain, including the need to improve acoustic coupling, enhance stone targeting, better determine when stone breakage is complete, and minimize the occurrence of residual stone fragments. New technologies have begun to address many of these issues, and hold considerable promise for the future. PMID:19956196

  18. Advances in ferroelectric polymers for shock compression sensors

    SciTech Connect

    Bauer, F.; Moulard, H.; Samara, G.

    1997-10-01

    Our studies of the shock compression response of PVDF polymer are continuing in order to understand the physical properties under shock loading and to develop high fidelity, reproducible, time-resolved dynamic stress gauges. New PVDF technology, new electrode configurations and piezoelectric analysis have resulted in enhanced precision gauges. Our new standard gauges have a precision of better than 1% in electric charge release under shock up to 15 GPa. The piezoelectric response of shock compressed PVDF gauges 1 mm{sup 2} in active area has been studied and yielded well-behaved reproducible data up to 20 GPa. Analysis of the response of these gauges in the {open_quotes}thin mode regime{close_quotes} using a Lagrangian hydrocode will be presented. P(VDF-TrFE) copolymers exhibit unique piezoelectric properties over a wide range of temperature depending on the composition. Their properties and phase transitions are being investigated. Emphasis of the presentation will be on key results and implications.

  19. Advances in ferroelectric polymers for shock compression sensors

    SciTech Connect

    Bauer, F.; Moulard, H.; Samara, G.

    1998-07-01

    Our studies of the shock compression response of PVDF polymer are continuing in order to understand the physical properties under shock loading and to develop high fidelity, reproducible, time-resolved dynamic stress gauges. New PVDF technology, new electrode configurations and piezoelectric analysis have resulted in enhanced precision gauges. Our new standard gauges have a precision of better than 1{percent} in electrical charge release under shock up to 15 GPa. The piezoelectric response of shock compressed PVDF gauges 1 mm{sup 2} in active area has been studied and yielded well-behaved reproducible data up to 20 GPa. Analysis of the response of these gauges in the {open_quotes}thin mode regime{close_quotes} using a Lagrangian hydrocode will be presented. P(VDF-TrFE) copolymers exhibit unique piezoelectric properties over a wide range of temperature depending on the composition. Their properties and phase transitions are being investigated. Emphasis of the presentation will be on key results and implications. {copyright} {ital 1998 American Institute of Physics.}

  20. Advance warning of high-speed ejecta based on real-time shock analyses: When fast-moving ejecta appear to be overtaking slow-moving shocks

    NASA Astrophysics Data System (ADS)

    Paulson, Kristoff W.; Taylor, David K.; Smith, Charles W.; Vasquez, Bernard J.; Hu, Q.

    2012-12-01

    Interplanetary shocks propagating into the magnetosphere can have significant space weather consequences. However, for many purposes it is the ejecta behind the shock that is the greater threat. The ejecta can be fast moving, impart significant momentum upon the magnetopause, and may contain a flux rope with strong southward magnetic fields. When transient solar wind activity strikes the magnetosphere, it can lead to enhanced magnetospheric currents and elevated radiation levels in the near-Earth environment. It is therefore desirable to use the observed shocks ahead of ejecta to predict any aspects of the approaching ejecta that can be predicted. We have examined 39 shocks observed by the Advanced Composition Explorer spacecraft in the years 1998 to 2003. Within the selection are shocks that were chosen because they appear to propagate significantly more slowly than the speed of the ejecta behind it. While appearing at first to be a contradiction, we show that the shocks are propagating across the radial direction and at significant angles to the velocity of the ejecta. These slow-moving shocks are actually precursors of fast-moving and potentially significant ejecta. Reversing the analysis, we are able to predict the peak speed of the ejecta well in advance of their observation, up to or in excess of 10 h following the shock crossing, when slow-moving shocks are seen, and we have incorporated this feature into our real-time shock analysis.

  1. Vasodilatory mechanisms of unoprostone isopropyl in isolated porcine retinal arterioles

    PubMed Central

    Tanano, Ichiro; Ono, Shinji; Omae, Tsuneaki; Otani, Shinichi; Yoshida, Akitoshi

    2015-01-01

    Purpose To clarify the vasodilatory mechanism of unoprostone isopropyl (UI), we examined its effects on the retinal microvascular diameter to determine the dependence on the endothelium and/or smooth muscle to reveal the signaling mechanisms involved in this vasomotor activity. Methods Porcine retinal arterioles were isolated, cannulated, and pressurized without flow in vitro. Video microscopic techniques recorded the diametric responses to UI. Results The retinal arterioles dilated in response to UI in a dose-dependent (100 pM-10 µM) manner. The nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) inhibited UI-induced vasodilation. The large-conductance Ca2+-activated K channel (BKCa channel) blocker iberiotoxin also inhibited UI-induced vasodilation. The residual vasodilation after L-NAME was eliminated with co-administration of iberiotoxin. Conclusions UI elicits dilation of the retinal arterioles mediated by NO release and BKCa channel activation. PMID:26120274

  2. Heat Shock Proteins in Dermatophytes: Current Advances and Perspectives.

    PubMed

    Martinez-Rossi, Nilce M; Jacob, Tiago R; Sanches, Pablo R; Peres, Nalu T A; Lang, Elza A S; Martins, Maíra P; Rossi, Antonio

    2016-04-01

    Heat shock proteins (HSPs) are proteins whose transcription responds rapidly to temperature shifts. They constitute a family of molecular chaperones, involved in the proper folding and stabilisation of proteins under physiological and adverse conditions. HSPs also assist in the protection and recovery of cells exposed to a variety of stressful conditions, including heat. The role of HSPs extends beyond chaperoning proteins, as they also participate in diverse cellular functions, such as the assembly of macromolecular complexes, protein transport and sorting, dissociation of denatured protein aggregates, cell cycle control, and programmed cell death. They are also important antigens from a variety of pathogens, are able to stimulate innate immune cells, and are implicated in acquired immunity. In fungi, HSPs have been implicated in virulence, dimorphic transition, and drug resistance. Some HSPs are potential targets for therapeutic strategies. In this review, we discuss the current understanding of HSPs in dermatophytes, which are a group of keratinophilic fungi responsible for superficial mycoses in humans and animals. Computational analyses were performed to characterise the group of proteins in these dermatophytes, as well as to assess their conservation and to identify DNA-binding domains (5'-nGAAn-3') in the promoter regions of the hsp genes. In addition, the quantification of the transcript levels of few genes in a pacC background helped in the development of an extended model for the regulation of the expression of the hsp genes, which supports the participation of the pH-responsive transcriptional regulator PacC in this process. PMID:27226766

  3. Shock.

    PubMed

    Wacker, David A; Winters, Michael E

    2014-11-01

    Critically ill patients with undifferentiated shock are complex and challenging cases in the ED. A systematic approach to assessment and management is essential to prevent unnecessary morbidity and mortality. The simplified, systematic approach described in this article focuses on determining the presence of problems with cardiac function (the pump), intravascular volume (the tank), or systemic vascular resistance (the pipes). With this approach, the emergency physician can detect life-threatening conditions and implement time-sensitive therapy. PMID:25441032

  4. Impact of age on the vasodilatory function of human skeletal muscle feed arteries.

    PubMed

    Park, Song-Young; Ives, Stephen J; Gifford, Jayson R; Andtbacka, Robert H I; Hyngstrom, John R; Reese, Van; Layec, Gwenael; Bharath, Leena P; Symons, John D; Richardson, Russell S

    2016-01-15

    Although advancing age is often associated with attenuated skeletal muscle blood flow and skeletal muscle feed arteries (SMFAs) have been recognized to play a regulatory role in the vasculature, little is known about the impact of age on the vasodilatory capacity of human SMFAs. Therefore, endothelium-dependent and -independent vasodilation were assessed in SMFAs (diameter: 544 ± 63 μm) obtained from 24 (equally represented) young (33 ± 2 yr) and old (71 ± 2 yr) subjects in response to three stimuli: 1) flow-induced shear stress, 2) ACh, and 3) sodium nitropusside (SNP). Both assessments of endothelium-dependent vasodilation, flow (young subjects: 68 ± 1% and old subjects: 32 ± 7%) and ACh (young subjects: 92 ± 3% and old subjects: 73 ± 4%), were significantly blunted (P < 0.05) in SMFAs of old compared with young subjects, with no such age-related differences in endothelium-independent vasodilation (SNP). In response to an increase in flow-induced shear stress, vasodilation kinetics (time constant to reach 63% of the amplitude of the response: 55 ± 1 s in young subjects and 92 ± 7 s in old subjects) and endothelial nitric oxide synthase (eNOS) activation (phospho-eNOS(s1177)/total eNOS: 1.0 ± 0.1 in young subjects and 0.2 ± 0.1 in old subjects) were also significantly attenuated in old compared with young subjects (P < 0.05). Furthermore, the vessel superoxide concentration was greater in old subjects (old subjects: 3.9 ± 1.0 area under curve/mg and young subjects: 1.7 ± 0.1 area under the curve/mg, P < 0.05). These findings reveal that the endothelium-dependent vasodilatory capacity, including vasodilation kinetics but not smooth muscle function, of human SMFAs is blunted with age and may be due to free radicals. Given the potential regulatory role of SMFAs in skeletal muscle blood flow, these findings may explain, at least in part, the often observed attenuated perfusion of skeletal muscle with advancing age that may contribute to exercise

  5. Vasopressin during cardiopulmonary resuscitation and different shock states: a review of the literature.

    PubMed

    Krismer, Anette C; Dünser, Martin W; Lindner, Karl H; Stadlbauer, Karl H; Mayr, Viktoria D; Lienhart, Hannes G; Arntz, Richard H; Wenzel, Volker

    2006-01-01

    Vasopressin administration may be a promising therapy in the management of various shock states. In laboratory models of cardiac arrest, vasopressin improved vital organ blood flow, cerebral oxygen delivery, the rate of return of spontaneous circulation, and neurological recovery compared with epinephrine (adrenaline). In a study of 1219 adult patients with cardiac arrest, the effects of vasopressin were similar to those of epinephrine in the management of ventricular fibrillation and pulseless electrical activity; however, vasopressin was superior to epinephrine in patients with asystole. Furthermore, vasopressin followed by epinephrine resulted in significantly higher rates of survival to hospital admission and hospital discharge. The current cardiopulmonary resuscitation guidelines recommend intravenous vasopressin 40 IU or epinephrine 1mg in adult patients refractory to electrical countershock. Several investigations have demonstrated that vasopressin can successfully stabilize hemodynamic variables in advanced vasodilatory shock. Use of vasopressin in vasodilatory shock should be guided by strict hemodynamic indications, such as hypotension despite norepinephrine (noradrenaline) dosages >0.5 mug/kg/min. Vasopressin must never be used as the sole vasopressor agent. In our institutional routine, a fixed vasopressin dosage of 0.067 IU/min (i.e. 100 IU/50 mL at 2 mL/h) is administered and mean arterial pressure is regulated by adjusting norepinephrine infusion. When norepinephrine dosages decrease to 0.2 microg/kg/min, vasopressin is withdrawn in small steps according to the response in mean arterial pressure. Vasopressin also improved short- and long-term survival in various porcine models of uncontrolled hemorrhagic shock. In the clinical setting, we observed positive effects of vasopressin in some patients with life-threatening hemorrhagic shock, which had no longer responded to adrenergic catecholamines and fluid resuscitation. Clinical employment of

  6. Validation of an Advanced Material Model for Simulating the Impact and Shock Response of Composite Materials

    NASA Astrophysics Data System (ADS)

    Clegg, Richard A.; Hayhurst, Colin J.; Nahme, Hartwig

    2001-06-01

    Validation of an advanced continuum based numerical model for the simulation of the shock response of composite materials during high rate transient dynamic loading is described. The constitutive model, implemented in AUTODYN-2D and 3D, allows for the representation of non-linear shock effects in combination with orthotropic stiffness and damage. Simulations of uniaxial flyer plate experiments on aramid and polyethylene fibre composite systems are presented and compared with experiment. The continuum model is shown to reproduce well the experimental VISAR velocity traces at the rear surface of the targets. Finally, practical application of the model as implemented in AUTODYN is demonstrated through the simulation of ballistic and hypervelocity impact events. Comparison with experiment is given where possible.

  7. Validation of an Advanced Material Model for Simulating the Impact and Shock Response of Composite Materials

    NASA Astrophysics Data System (ADS)

    Clegg, Richard A.; Hayhurst, Colin J.; Nahme, Hartwig

    2002-07-01

    Composite materials are now commonly used as ballistic and hypervelocity protection materials and the demand for simulation of impact on these materials is increasing. A new material model specifically designed for the shock response of anisotropic materials has been developed and implemented in the hydrocode AUTODYN. The model allows for the representation of non-linear shock effects in combination with anisotropic material stiffness and damage. The coupling of the equation of state and anisotropic response is based on the methodology proposed by Anderson et al. [2]. An overview of the coupled formulation is described in order to point out the important assumptions, key innovations and basic theoretical framework. The coupled model was originally developed by Century Dynamics and Fhg-EMI for assessing the hypervelocity impact response of composite satellite protection systems [1]. It was also identified that the developed model should also offer new possibilities and capabilities for modelling modern advanced armour materials. Validation of the advanced composite model is firstly shown via simulations of uniaxial strain flyer plate experiments on aramid and polyethylene fibre composite systems. Finally, practical application of the model as implemented in AUTODYN is demonstrated through the simulation of ballistic and hypervelocity impact events. Comparison with experiment is given where possible.

  8. Potential Improvements in Shock-Mitigation Efficacy of a Polyurea-Augmented Advanced Combat Helmet

    NASA Astrophysics Data System (ADS)

    Grujicic, A.; LaBerge, M.; Grujicic, M.; Pandurangan, B.; Runt, J.; Tarter, J.; Dillon, G.

    2012-08-01

    The design of the currently used Advanced Combat Helmet (ACH) has been optimized to attain maximum protection against ballistic impacts (fragments, shrapnel, etc.) and hard-surface collisions. However, the ability of the ACH to protect soldiers against blast loading appears not to be as effective. Polyurea, a micro-segregated elastomeric copolymer has shown superior shock-mitigation capabilities. In the present work, a combined Eulerian/Lagrangian transient non-linear dynamics computational fluid/solid interaction analysis is used to investigate potential shock-mitigation benefits which may result from different polyurea-based design augmentations of the ACH. Specific augmentations include replacement of the currently used suspension-pad material with polyurea and the introduction of a thin polyurea internal lining/external coating to the ACH shell. Effectiveness of different ACH designs was quantified by: (a) establishing the main forms of mild traumatic brain injury (mTBI); (b) identifying the key mechanical causes for these injuries; and (c) quantifying the extents of reductions in the magnitude of these mechanical causes. The results obtained show that while the ACH with a 2-mm-thick polyurea internal lining displays the best blast mitigation performance, it does not provide sufficient protection against mTBI.

  9. Time course of vasodilatory responses in skeletal muscle arterioles: role in hyperemia at onset of exercise

    NASA Technical Reports Server (NTRS)

    Wunsch, S. A.; Muller-Delp, J.; Delp, M. D.

    2000-01-01

    At the onset of dynamic exercise, muscle blood flow increases within 1-2 s. It has been postulated that local vasodilatory agents produced by the vascular endothelium or the muscle itself contribute to this response. We hypothesized that only vasodilators that act directly on the vascular smooth muscle could produce vasodilation of skeletal muscle arterioles in <2 s. To test this hypothesis, we determined the time course of the vasodilatory response of isolated skeletal muscle arterioles to direct application of potassium chloride, adenosine, acetylcholine, and sodium nitroprusside. Soleus and gastrocnemius muscles were dissected from the hindlimbs of male Sprague-Dawley rats. First-order arterioles (100-200 microm) were isolated, cannulated on micropipettes, and pressurized to 60 cmH(2)O in an organ bath. Vasodilatory agents were added directly to the bath, and diameter responses of the arterioles were recorded in real time on a videotape recorder. Frame-by-frame analysis of the diameter responses indicated that none of the vasodilator agents tested produced significant diameter increases in <4 s in either soleus or gastrocnemius muscle arterioles. These results indicate that, although these local vasodilators produce significant vasodilation of skeletal muscle resistance arterioles, these responses are not rapid enough (within 1-2 s) to contribute to the initiation of the exercise hyperemic response at the onset of dynamic exercise.

  10. [Advances in the research of early goal-directed therapy in severe sepsis and septic shock].

    PubMed

    Sun, W; Yuan, H X; An, Y Z

    2016-05-20

    Nowadays, severe infection has become one of the common problems in clinic. The morbidity of severe sepsis and septic shock is increasing, which becomes a big threat to patients with burn wounds or chronic diseases. It has become a key subject about how to cure severe sepsis and septic shock. In recent years, mortality of patients in such condition has declined slightly, which might be attributed to the application of early goal-directed therapy (EGDT) in certain degree. This article reviews application of EGDT in severe sepsis and septic shock, in order to analyze its effectiveness and boundedness, as well as predict its development. PMID:27188487

  11. Pharmacologic agents for acute hemodynamic instability: Recent advances in the management of perioperative shock- A systematic review

    PubMed Central

    Morozowich, Steven T.; Ramakrishna, Harish

    2015-01-01

    Despite the growing body of evidence evaluating the efficacy of vasoactive agents in the management of hemodynamic instability and circulatory shock, it appears no agent is superior. This is becoming increasingly accepted as current guidelines are moving away from detailed algorithms for the management of shock, and instead succinctly state that vasoactive agents should be individualized and guided by invasive hemodynamic monitoring. This extends to the perioperative period, where vasoactive agent selection and use may still be left to the discretion of the treating physician with a goal-directed approach, consisting of close hemodynamic monitoring and administration of the lowest effective dose to achieve the hemodynamic goals. Successful therapy depends on the ability to rapidly diagnose the etiology of circulatory shock and thoroughly understand its pathophysiology as well as the pharmacology of vasoactive agents. This review focuses on the physiology and resuscitation goals in perioperative shock, as well as the pharmacology and recent advances in vasoactive agent use in its management. PMID:26440241

  12. Peripheral microvascular vasodilatory response to estradiol and genistein in women with insulin resistance

    PubMed Central

    Wenner, Megan M.; Taylor, Hugh S.; Stachenfeld, Nina S.

    2015-01-01

    Objective Estradiol enhances vasodilation in healthy women, but vascular effects of the phytoestrogen genistein are still under investigation. Insulin resistance (IR) compromises microvascular function. We therefore examined the interaction of estradiol, genistein, and IR on microvascular vasodilatory responsiveness. Methods We hypothesized that estradiol and genistein increase microvascular vasodilation in healthy women (control, n=8, 23±2 yr, BMI 25.9±2.9 kg/m2) but not in women with IR (n=7, 20±1 yr, BMI 27.3±3.0 kg/m2). We used the cutaneous circulation as a model of microvascular vasodilatory function. We determined cutaneous vascular conductance (CVC) with laser Doppler flowmetry and beat-to-beat blood pressure during local cutaneous heating (42°C) with estradiol or genistein microdialysis perfusions. Because heat induced vasodilation is primarily an NO mediated response, we examined microvascular vasodilation with and without L-NMMA. Results In control women, estradiol enhanced CVC (94.4±2.6 % vs. saline 81.6±4.2 % CVCmax, P<0.05), which was reversed with L-NMMA (80.9±7.8 % CVCmax, P<0.05), but genistein did not affect vasodilation. Neither estradiol nor genistein altered CVC in IR, although L-NMMA attenuated CVC during genistein. Conclusions Our study does not support improved microvascular responsiveness during genistein exposure in healthy young women, and demonstrates that neither estradiol nor genistein improve microvascular vasodilatory responsiveness in women with IR. PMID:25996650

  13. Advances in the diagnosis of shock, its assessment and resuscitation during the Great War.

    PubMed

    Bullingham, A G P

    2016-07-01

    The Great War of 1914-1918 ushered in a new era of technology on the battlefield resulting in casualties on an unprecedented scale. There had been progress in many related areas of medicine before the outbreak of hostilities but these had not been applied or fully developed in clinical practice. This is particularly true for the management of haemorrhagic shock and resuscitation. This article discusses the history and development of medical treatment of shock and trauma patients during the conflict. PMID:27456289

  14. Radial Extracorporeal Shock Wave Therapy in a Person With Advanced Osteonecrosis of the Femoral Head

    PubMed Central

    Ma, Yue Wen; Jiang, Dong Lei; Zhang, Dai; Wang, Xiao Bei; Yu, Xiao Tong

    2016-01-01

    ABSTRACT This case report describes the first patient with avascular necrosis of the femoral head of Association Research Circulation Osseous stage IV, treated with radial extracorporeal shock wave therapy. By contrast, previous studies demonstrated the efficacy of a single treatment of focused extracorporeal shock wave therapy in improving pain and Harris Hip Scale in patients with avascular necrosis of the femoral head of Association Research Circulation Osseous stage I to III. The affected hip was treated with 6000 impulses of radial extracorporeal shock wave therapy at 10 Hz and an intensity ranging from 2.5 to 4.0 bar at 7-day intervals for 24 mos. The Harris Hip Scale values were 33, 43, 56, 77, 81, 88, and 92 at baseline and 1, 3, 6, 12, 18, and 24 mos, respectively. The radiographs showed that the subluxation of the right hip was slightly aggravated. Joint effusion was reduced, bone marrow edema disappeared, the density became more uniform, and the gluteal muscles were more developed based on magnetic resonance imaging. Increased tracer uptake was evident along the joint margin and superolateral aspect of the head both before and after radial extracorporeal shock wave therapy. This case report demonstrates the feasibility of long-term radial extracorporeal shock wave therapy in Association Research Circulation Osseous stage IV patients. PMID:27003206

  15. Radial Extracorporeal Shock Wave Therapy in a Person With Advanced Osteonecrosis of the Femoral Head.

    PubMed

    Ma, Yue Wen; Jiang, Dong Lei; Zhang, Dai; Wang, Xiao Bei; Yu, Xiao Tong

    2016-09-01

    This case report describes the first patient with avascular necrosis of the femoral head of Association Research Circulation Osseous stage IV, treated with radial extracorporeal shock wave therapy. By contrast, previous studies demonstrated the efficacy of a single treatment of focused extracorporeal shock wave therapy in improving pain and Harris Hip Scale in patients with avascular necrosis of the femoral head of Association Research Circulation Osseous stage I to III. The affected hip was treated with 6000 impulses of radial extracorporeal shock wave therapy at 10 Hz and an intensity ranging from 2.5 to 4.0 bar at 7-day intervals for 24 mos. The Harris Hip Scale values were 33, 43, 56, 77, 81, 88, and 92 at baseline and 1, 3, 6, 12, 18, and 24 mos, respectively. The radiographs showed that the subluxation of the right hip was slightly aggravated. Joint effusion was reduced, bone marrow edema disappeared, the density became more uniform, and the gluteal muscles were more developed based on magnetic resonance imaging. Increased tracer uptake was evident along the joint margin and superolateral aspect of the head both before and after radial extracorporeal shock wave therapy. This case report demonstrates the feasibility of long-term radial extracorporeal shock wave therapy in Association Research Circulation Osseous stage IV patients. PMID:27003206

  16. Vasodilatory effects of cinnamaldehyde and its mechanism of action in the rat aorta

    PubMed Central

    Xue, Yong-Liang; Shi, Hai-Xia; Murad, Ferid; Bian, Ka

    2011-01-01

    The vasodilatory effect of cinnamaldehyde was investigated for its mechanism of action using isolated rings of rat aorta. Cinnamaldehyde relaxed aortic rings precontracted with phenylephrine in a dose-dependent manner, was not affected by either the presence or removal of the endothelium. Pretreatment with NG-nitro-L-arginine methyl ester and 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one could not block vasodilation by cinnamaldehyde, indicating that nitric oxide signaling is not involved. Potassium channel blockers, such as glibenclamide, tetraethylammonium, and BaCl2, had no effect on the relaxation produced by cinnamaldehyde. In addition, treatment with either indomethacin or propranolol did not affect cinnamaldehyde-induced vasodilatation. On the other hand, pretreatment of endothelium-denuded rings with cinnamaldehyde significantly inhibited vasoconstriction induced by endogenous vasoconstrictors, including angiotensin II, 5-hydroxytryptamine, dopamine, endothelin-1, and phenylephrine. In a Ca2+-free experimental setting, this natural vasodilator not only blocked Ca2+ influx-dependent vasoconstriction by either phenylephrine or KCl, but also inhibited phenylephrine-induced tonic contraction, which relies on intracellular Ca2+ release. This study shows that endothelium-independent, Ca2+ influx and/or an inhibitory release mechanism contributes to the vasodilatory effect of cinnamaldehyde. PMID:21603596

  17. Thermally treated wine retains vasodilatory activity in rat and guinea pig aorta.

    PubMed

    Mudnić, Ivana; Budimir, Danijela; Jajić, Ivan; Boban, Nataša; Sutlović, Davorka; Jerončić, Ana; Boban, Mladen

    2011-06-01

    In contrast to the intact wine, cardiovascular effects of the thermally treated wine have not been studied, despite widespread habits of cooking with wine and consumption of mulled wine. Vasodilatory effects of the red wine heated at 75 and 125°C were examined in the isolated rat and guinea pig aorta and compared with the intact and wine dealcoholized without thermal stress. Samples were analyzed for their phenolic content, antioxidant capacity, resveratrol and ethanol contents. Heating-induced degradation of individual phenolic fraction was observed only in the samples treated at 125°C, although total phenolic concentration and related antioxidant activity increased in the thermally treated samples due to the reduction in their volume. All wine samples regardless of treatment caused similar maximal relaxation in both species, but the response was stronger in aortas from guinea pigs. At the lowest concentrations up to 1‰, dealcoholized wine produced vasodilation greater than that produced by intact wine and wines treated at 75 and 125°C, which showed similar vasodilating activity at all concentrations. Our results indicate that wine thermally treated under heating conditions applicable to the preparation of a mulled wine and cooking with wine largely retains vasodilatory activity in vitro despite significant heat-induced changes in its composition. PMID:21423027

  18. Advances in CFD prediction of shock wave turbulent boundary layer interactions

    NASA Astrophysics Data System (ADS)

    Knight, Doyle; Yan, Hong; Panaras, Argyris G.; Zheltovodov, Alexander

    2003-04-01

    The paper presents a summary of recent computational fluid dynamics (CFD) simulations of shock wave turbulent boundary layer interactions. This survey was prepared as part of the activity of NATO RTO Working Group 10 which was established in December 1998, and considers results obtained subsequent to the previous survey paper on the same topic by Knight and Degrez (“Shock Wave Boundary Layer Interactions in High Mach Number Flows-A Critical Survey of Current CFD Prediction Capabilities”, AGARD Advisory Report AR-319, Volume II, December 1998). Five configurations are considered: 2-D compression corner, 2-D shock impingement, 2-D expansion-compression corner, 3-D single fin and 3-D double fin. Recent direct numerical simulations (DNS), large eddy simulations (LES) and Reynolds-averaged Navier-Stokes (RANS) simulations are compared with experiment. The capabilities and limitations are described, and future research needs identified.

  19. Advanced Shock Position Control for Mode Transition in a Turbine Based Combined Cycle Engine Inlet Model

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Stueber, Thomas J.

    2013-01-01

    A dual flow-path inlet system is being tested to evaluate methodologies for a Turbine Based Combined Cycle (TBCC) propulsion system to perform a controlled inlet mode transition. Prior to experimental testing, simulation models are used to test, debug, and validate potential control algorithms. One simulation package being used for testing is the High Mach Transient Engine Cycle Code simulation, known as HiTECC. This paper discusses the closed loop control system, which utilizes a shock location sensor to improve inlet performance and operability. Even though the shock location feedback has a coarse resolution, the feedback allows for a reduction in steady state error and, in some cases, better performance than with previous proposed pressure ratio based methods. This paper demonstrates the design and benefit with the implementation of a proportional-integral controller, an H-Infinity based controller, and a disturbance observer based controller.

  20. Advanced Spectroscopic and Thermal Imaging Instrumentation for Shock Tube and Ballistic Range Facilities

    NASA Technical Reports Server (NTRS)

    Grinstead, Jay H.; Wilder, Michael C.; Reda, Daniel C.; Cruden, Brett A.; Bogdanoff, David W.

    2010-01-01

    The Electric Arc Shock Tube (EAST) facility and Hypervelocity Free Flight Aerodynamic Facility (HFFAF, an aeroballistic range) at NASA Ames support basic research in aerothermodynamic phenomena of atmospheric entry, specifically shock layer radiation spectroscopy, convective and radiative heat transfer, and transition to turbulence. Innovative optical instrumentation has been developed and implemented to meet the challenges posed from obtaining such data in these impulse facilities. Spatially and spectrally resolved measurements of absolute radiance of a travelling shock wave in EAST are acquired using multiplexed, time-gated imaging spectrographs. Nearly complete spectral coverage from the vacuum ultraviolet to the near infrared is possible in a single experiment. Time-gated thermal imaging of ballistic range models in flight enables quantitative, global measurements of surface temperature. These images can be interpreted to determine convective heat transfer rates and reveal transition to turbulence due to isolated and distributed surface roughness at hypersonic velocities. The focus of this paper is a detailed description of the optical instrumentation currently in use in the EAST and HFFAF.

  1. Augmented muscle vasodilatory responses in obese children with Glu27 beta-2-adrenoceptor polymorphism.

    PubMed

    da Silva, Alexandre G; Ribeiro, Mauricio M; Trombetta, Ivani C; Nicolau, Christiane; Frazzatto, Eliana; Guazzelli, Isabel; Matos, Luciana N J; Halbern, Alfredo; Negrão, Carlos E; Villares, Sandra M F

    2008-05-01

    This study examined forearm vasodilatation during mental challenge and exercise in 72 obese children (OC; age = 10 +/- 0.1 years) homozygous with polymorphism in the allele 27 of the beta-2-adrenoceptors: Gln27 (n = 61) and Glu27 (n = 11). Forearm blood flow was recorded during 3 min of each using the Stroop color-word test (MS) and handgrip isometric exercise. Baseline hemodynamic and vascular measurements were similar. During the MS, peak forearm vascular conductance was significantly greater in group Glu27 (Delta = 0.35 +/- 0.4 vs. 0.12 +/- 0.1 units, respectively, p = .042). Similar results were found during exercise (Delta = 0.64 +/- 0.1 vs. 0.13 +/- 0.1 units, respectively, p = .035). Glu27 OC increased muscle vasodilatory responsiveness upon the MS and exercise. PMID:18579897

  2. Septic Shock in Advanced Age: Transcriptome Analysis Reveals Altered Molecular Signatures in Neutrophil Granulocytes

    PubMed Central

    Vieira da Silva Pellegrina, Diogo; Severino, Patricia; Vieira Barbeiro, Hermes; Maziero Andreghetto, Flávia; Tadeu Velasco, Irineu; Possolo de Souza, Heraldo; Machado, Marcel Cerqueira César; Reis, Eduardo Moraes; Pinheiro da Silva, Fabiano

    2015-01-01

    Sepsis is one of the highest causes of mortality in hospitalized people and a common complication in both surgical and clinical patients admitted to hospital for non-infectious reasons. Sepsis is especially common in older people and its incidence is likely to increase substantially as a population ages. Despite its increased prevalence and mortality in older people, immune responses in the elderly during septic shock appear similar to that in younger patients. The purpose of this study was to conduct a genome-wide gene expression analysis of circulating neutrophils from old and young septic patients to better understand how aged individuals respond to severe infectious insult. We detected several genes whose expression could be used to differentiate immune responses of the elderly from those of young people, including genes related to oxidative phosphorylation, mitochondrial dysfunction and TGF-β signaling, among others. Our results identify major molecular pathways that are particularly affected in the elderly during sepsis, which might have a pivotal role in worsening clinical outcomes compared with young people with sepsis. PMID:26047321

  3. Affinity of isoxsuprine for adrenoreceptors in equine digital artery and implications for vasodilatory action.

    PubMed

    Belloli, C; Carcano, R; Arioli, F; Beretta, C

    2000-03-01

    We used isolated equine digital arteries to study the vasodilatory mechanism of isoxsuprine, and fowl caecum preparations to investigate the affinity of the drug for beta-adrenoceptors. Isoxsuprine is a potent vasodilator of arterial smooth muscle that has been precontracted by an alpha-adrenoceptor agonist such as noradrenaline (log EC50 = -6.33 [-5.98; -6.68]). The present study indicates that its effect is due to alpha-adrenoceptor blockade since: (1) after a long lasting exposure to cumulative doses of isoxsuprine the vasoconstricting action of noradrenaline cannot be restored; (2) isoxsuprine does not promote relaxation on preparations precontracted by PGF2alpha; (3) isoxsuprine shifts the dose-response curve of noradrenaline to the right; and (4) its affinity (pK(B) = 6.90 [6.60; 7.20]) in this experiment is comparable to that in noradrenaline-precontracted preparations and is 14 times lower than that of the selective alpha1-adrenergic antagonist prazosin [pK(B) = 8.04 (7.40; 8.68]). The affinity of isoxsuprine for beta-adrenoceptors was 100 times lower than that of isoprenaline when tested on fowl caecum. This preparation has a large beta-adrenoceptor and negligible alpha-adrenoceptor population concerned with the control of smooth muscle motility. Our data suggest that the alpha-mediated effect of isoxsuprine on horse arterial smooth muscle is due to higher affinity of the drug for alpha- than beta-adrenoceptors rather than low concentration or functionality of beta-sites at this site. According to these data, pure beta2-agonists seem to be more profitable tools to determine vasodilation of the arterial bed in horses legs. PMID:10743967

  4. Vasodilatory Effect of Wogonin on the Rat Aorta and Its Mechanism Study.

    PubMed

    Qu, Jing-Tian; Zhang, Dong-Xuan; Liu, Fang; Mao, Hao-Ping; Ma, Ya-Ke; Yang, Yue; Li, Chun-Xiao; Qiu, Li-Zhen; Geng, Xiao; Zhang, Jian-Mei; Gao, Xiu-Mei; Chen, Lu; Wang, Hong

    2015-01-01

    Wogonin, a natural flavonoid, is one of the bioactive compounds of the medicinal herb Eucommia ulmoides OLIV. widely used in southeastern Asia for treating hypertension. However, the molecular mechanisms for the therapeutic benefits remain largely unclear. The present study investigated the vasodilatory effect of wogonin and its possible mechanisms. The flavonoid (0.1-100 µM) caused concentration-dependent relaxations in endothelium-intact aortic rings precontracted with norepinephrine (NE, 1 µM) or potassium chloride (KCl, 60 mM). Preincubation with wogonin (10, 100 µM) for 20 min significantly inhibited the contractile responses to NE (0.1, 1, 10 µM) or KCl (7.5, 15, 30, 60 mM). Relaxant responses to wogonin were not inhibited by N(G)-nitro-L-arginine methylester (100 µM) or endothelial denudation. In a Ca(2+)-free Krebs' solution, wogonin not only blocked Ca(2+) influx-dependent vasoconstriction by either NE (1 µM) or KCl (100 mM), but also inhibited NE (1 µM)-induced tonic contraction, which is dependent on intracellular Ca(2+) release. Wogonin also suppressed the elevation of [Ca(2+)]i induced by KCl (60 mM) after exhausting the calcium store in sarcoplasmic and endoplasmic reticula with thapsigargin (1 µM) or by ATP (100 µM) in primary vascular smooth muscle cells. These findings suggest that wogonin-induced responses are mainly due to the inhibition of both intracellular Ca(2+) release and extracellular Ca(2+) influx. PMID:26632179

  5. Effect of {beta}{sub 1} adrenergic receptor blockade on myocardial blood flow and vasodilatory capacity

    SciTech Connect

    Boettcher, M.; Czernin, J.; Sun, K.

    1997-03-01

    The {beta}{sub 1} receptor blockade reduces cardiac work and may thereby lower myocardial blood flow (MBF) at rest. The effect of {beta}{sub 1} receptor blockade on hyperemic MBF is unknown. To evaluate the effect of selective {beta}{sub 1} receptor blockade on MBF at rest and during dipyridamole induced hyperemia, 10 healthy volunteers (8 men, 2 women, mean age 24 {+-} 5 yr) were studied using {sup 13}N-ammonia PET (two-compartment model) under control conditions and again during metoprolol (50 mg orally 12 hr and 1 hr before the study). The resting rate pressure product (6628 {+-} 504 versus 5225 {+-} 807) and heart rate (63 {+-} 6-54 {plus_minus} 5 bpm) declined during metoprolol (p < 0.05). Similarly, heart rate and rate pressure product declined from the baseline dipyridamole study to dipyridamole plus metoprolol (p < 0.05). Resting MBF declined in proportion to cardiac work by approximately 20% from 0.61 {+-} 0.09-0.51 {+-} 0.10 ml/g/min (p < 0.05). In contrast, hyperemic MBF increased when metoprolol was added to dipyridamole (1.86 {plus_minus} 0.27 {+-} 0.45 ml/g/min; p<0.05). The decrease in resting MBF together with the increase in hyperemic MBF resulted in a significant increase in the myocardial flow reserve during metoprolol (3.14 {+-} 0.80-4.61 {+-} 0.68; p<0.01). The {beta}{sub 1} receptor blockade increases coronary vasodilatory capacity and myocardial flow reserve. However, the mechanisms accounting for this finding remain uncertain. 32 refs., 2 figs., 2 tabs.

  6. Advancement of Shock-wave Induced Spraying Process through the Study of Gas and Particle Flow Fields

    NASA Astrophysics Data System (ADS)

    Karimi Esfahani, Mohammad

    This research advances the knowledge of the working principles of the Shock-wave Induced Spraying Process (SISP), a thermal spray material deposition technique. Pulses created by a fast acting valve pass through a heated line increasing energy content and interacting with metered batches of heated or non-heated powder introduced into the line. The powder is accelerated to high velocities before bonding to the substrate upon impact. Advantages over other cold spray processes include cost savings and a more effective transfer of thermal energy to the powder. The shock-wave occurring near the substrate in other cold spray processes is avoided. The SISP flow field is resolved by using a computational model. The two-dimensional model accounts for the valve, gas heater, a tapered nozzle at the tip of the device, and preheating of the powder. It is implemented with a commercial computational fluid dynamics code. Comparisons are made with one-dimensional predictions, and measurements of pressure and temperature. Particle flow predictions are validated using particle velocity and adhesion measurements. A flow region of both high temperature and velocity gas, favorable to material deposition, forms which is not present in comparable steady-state cold spray processes. Increasing gas pressure increases the gas speed, while increasing temperature increases speed and temperature of this region. Using helium results in greater energy levels but for shorter periods of time. This indicates the need for a powder feeder which places particles in the flow at correct instants and durations of time. The effects of particle flow parameters on system performance are examined. It is found that the device must be operated at very high main heater and powder heater temperatures: 900 °C and 700 °C respectively to achieve a coating with stainless steel using nitrogen as the driving gas. It is also shown that a heater length range of 0.9 m to 1.4 m results in the greatest likelihood of

  7. Quantitative Analysis of Vasodilatory Action of Quercetin on Intramural Coronary Resistance Arteries of the Rat In Vitro

    PubMed Central

    Monori-Kiss, Anna; Monos, Emil; Nádasy, György L.

    2014-01-01

    Background Dietary quercetin improves cardiovascular health, relaxes some vascular smooth muscle and has been demonstrated to serve as a substrate for the cyclooxygenase enzyme. Aims 1. To test quantitatively a potential direct vasodilatory effect on intramural coronary resistance artery segments, in different concentrations. 2. To scale vasorelaxation at different intraluminal pressure loads on such vessels of different size. 3. To test the potential role of prostanoids in vasodilatation induced by quercetin. Methods Coronary arterioles (70–240 µm) were prepared from 24 rats and pressurized in PSS, using a pressure microangiometer. Results The spontaneous tone that developed at 50 mmHg was relaxed by quercetin in the 10−9 moles/lit concentration (p<0.05), while 10−5 moles/lit caused full relaxation. Significant relaxation was observed at all pressure levels (10–100 mmHg) at 10−7 moles/lit concentration of quercetin. The cyclooxygenase blocker indomethacin (10−5moles/lit) induced no relaxation but contraction when physiological concentrations of quercetin were present in the tissue bath (p<0.02 with Anova), this contraction being more prominent in smaller vessels and in the higher pressure range (p<0.05, Pearson correlation). A further 2–8% contraction could be elicited by the NO blocker L-NAME (10−4 moles/lit). Conclusion These results demonstrate that circulating levels of quercetin (10−7 moles/lit) exhibit a substantial coronary vasodilatory effect. The extent of it is commeasurable with that of several other physiological mechanisms of coronary blood flow control. At least part of this relaxation is the result of an altered balance toward the production of endogenous vasodilatory prostanoids in the coronary arteriole wall. PMID:25144688

  8. Characterization of agonist-induced endothelium-dependent vasodilatory responses in the vascular bed of the equine digit.

    PubMed

    Berhane, Y; Bailey, S R; Putignano, C; Elliott, J

    2008-02-01

    The role of endothelium-derived relaxing factors was studied in the regulation of vascular responses in the Krebs perfused equine isolated digit. Perfusion pressure was recorded in response to bolus doses of 5-hydroxytryptamine (6 nmol) alone or co-administered with carbachol (CCh; 0.2 micromol), bradykinin (BK; 0.2 nmol), substance P (SP; 0.2 nmol) or sodium nitroprusside (SNP; 0.2 micromol). N(omega)-Nitro-L-Arginine methyl ester hydrochloride (L-NAME; 300 microm) caused partial but significant inhibition of CCh-induced vasodilatory response, whereas BK and SP-induced responses were resistant to L-NAME. High potassium (K(+), 30 mm) and the cytochrome P-450 (CYP) epoxygenase inhibitor, clotrimazole (10 microm) plus L-NAME (100 microm), completely abolished the CCh, BK and SP-induced vasodilatory responses, whereas the response to SNP was unaffected. In contrast, the L-NAME-resistant proportion of CCh, BK and SP-induced vasodilatory response was not inhibited by the highly selective CYP2C9 inhibitor, sulphaphenazole (10 microm). The cyclo-oxygenase inhibitor, ibuprofen (10 microm) did not affect the CCh, BK and SP-induced responses. These data demonstrate that CCh, BK and SP-induced relaxation in the equine digit involve a combination of the NO and endothelium-derived hyperpolarizing factor (EDHF) pathways. These results do not support the evidence for the involvement of CYP-derived epoxyeicosatrienoic acids and the exact nature of EDHF in the equine digit remains to be established. PMID:18177312

  9. Gas gun shock experiments with single-pulse x-ray phase contrast imaging and diffraction at the Advanced Photon Source

    SciTech Connect

    Luo, S. N.; Jensen, B. J.; Hooks, D. E.; Ramos, K. J.; Yeager, J. D.; Kwiatkowski, K.; Shimada, T.; Fezzaa, K.

    2012-07-15

    The highly transient nature of shock loading and pronounced microstructure effects on dynamic materials response call for in situ, temporally and spatially resolved, x-ray-based diagnostics. Third-generation synchrotron x-ray sources are advantageous for x-ray phase contrast imaging (PCI) and diffraction under dynamic loading, due to their high photon fluxes, high coherency, and high pulse repetition rates. The feasibility of bulk-scale gas gun shock experiments with dynamic x-ray PCI and diffraction measurements was investigated at the beamline 32ID-B of the Advanced Photon Source. The x-ray beam characteristics, experimental setup, x-ray diagnostics, and static and dynamic test results are described. We demonstrate ultrafast, multiframe, single-pulse PCI measurements with unprecedented temporal (<100 ps) and spatial ({approx}2 {mu}m) resolutions for bulk-scale shock experiments, as well as single-pulse dynamic Laue diffraction. The results not only substantiate the potential of synchrotron-based experiments for addressing a variety of shock physics problems, but also allow us to identify the technical challenges related to image detection, x-ray source, and dynamic loading.

  10. Recent advances in simulating unsteady flow phenomena brought about by passage of shock waves in a linear turbine cascade

    SciTech Connect

    Collie, J.C.; Moses, H.L.; Schetz, J.A. ); Gregory, B.A. . Turbine Aero and Cooling Technology)

    1993-10-01

    High-pressure-ratio turbines have flows dominated by shock structures that pass downstream into the next blade row in an unsteady fashion. Recent numerical results have indicated that these unsteady shocks may significantly affect the aerodynamic and mechanical performance of turbine blading. High cost and limited accessibility of turbine rotating equipment severely restrict the quantitative evaluation of the unsteady flow field in that environment. Recently published results of the Virginia Tech transonic cascade facility indicate high integrity in simulation of the steady state flow phenomena. The facility has recently been modified to study the unsteady effects of passing shock waves. Shock waves are generated by a shotgun blast upstream of the blade row. Shadowgraph photos and high-response pressure data are compared to previously published experimental and numerically predicted results. Plots are included that indicate large fluctuations in estimated blade lift and cascade loss.

  11. Decreased coronary vasodilatory capacity in hypertrophic cardiomyopathy determined by split-dose thallium-dipyridamole myocardial scintigraphy

    SciTech Connect

    Koga, Y.; Yamaguchi, R.; Ogata, M.; Kihara, K.; Toshima, H. )

    1990-05-01

    Split-dose thallium-dipyridamole myocardial scintigraphy was performed in patients with nonobstructive hypertrophic cardiomyopathy (HC) who had angiographically normal coronary arteries. The dipyridamole-induced increases in thallium-201 uptake, calculated to evaluate coronary vasodilatory capacity, were significantly lower in 30 patients with HC than in 13 control subjects (177 +/- 58 vs 281 +/- 46%) and the reductions were observed in both the septal and lateral segments. The reductions of the septal segment in HC patients were significantly greater than those in 10 hypertensive patients with comparable degrees of septal hypertrophy. Of patients with HC, 16 had increases in thallium uptake well below the normal range. Compared with those having normal increases, these patients had significantly lower exercise duration (11 vs 15 minutes), with 33% having ST depression develop at a workload less than or equal to 80 watts. These data indicate that approximately one-half of patients with HC have impaired coronary vasodilatory capacity that could be an important pathophysiologic abnormality of HC resulting in the development of myocardial ischemia and the impairment of cardiac performance during exercise.

  12. NSF CAREER: What did we learn and advance in our knowledge on shocks in the lower corona and the magnetic field structure in the heliosheath

    NASA Astrophysics Data System (ADS)

    Opher, M.; Evans, R. M.; Liu, Y.; Kay, C.; Das, I.; Provornikova, E.; Drake, J. F.; Izmodenov, V.; Toth, G.; Gombosi, T. I.

    2011-12-01

    Here we review the recent advances that we made in our group with the support of the NSF CAREER. We will highlight the advances in understanding two frontiers areas: a) evolution of shocks in the lower corona and b) the heliosheath. Very little is known on how shocks thought to be driven by CMEs, form and evolve in the lower corona. This is a crucial area since its has been shown by observations that they form low in the corona (1-4Rs) and coincide with the acceleration to GeV energies. We will describe our recent results describing the evolution of shocks in lower corona (Liu et al. 2008, 2011, Evans et al. 2011; Das et al.; 2011). Our ability to model and accurately describe shocks in the lower corona is challenged by our lack of knowledge of the background solar wind at the distances 1-10Rs (Evans et al. 2008). Recent models have included solar wind driven by Alfven waves with physical motivated damping reaching great agreement with tomographic observations in the lower corona R<1.2Rs (Evans et al. 2011a). Recent work (Das et al. 2011) found that compressions are formed in CME sheath due to the strong lateral expansions suffered in the lower corona. These would affect the acceleration of SEPs lower in the corona. We explored the evolution of shocks in the lower corona with this new solar wind background: finding extra heating at CME sheath due to Alfven waves (Evans et al. 2011b) and deflection when the CMEs are ejected near Coronal Holes (Kay et al. 2011). Finally, we present some of new phenomena that we were able to explore, the reconnection of the sectored magnetic field in the heliosheath. All the current global models of the heliosphere are based on the assumption that the magnetic field in the heliosheath, in the region close to the heliopause is laminar and connect back to the Sun. We argue recently, based on Voyager observations that in that region the heliospheric magnetic field is not laminar but instead consists of magnetic bubbles, or magnetic

  13. Pharmacological characterization of FE 202158, a novel, potent, selective, and short-acting peptidic vasopressin V1a receptor full agonist for the treatment of vasodilatory hypotension.

    PubMed

    Laporte, Régent; Kohan, Arash; Heitzmann, Joshua; Wisniewska, Halina; Toy, Jeannine; La, Erin; Tariga, Hiroe; Alagarsamy, Sudarkodi; Ly, Brian; Dykert, John; Qi, Steve; Wisniewski, Kazimierz; Galyean, Robert; Croston, Glenn; Schteingart, Claudio D; Rivière, Pierre J-M

    2011-06-01

    FE 202158, ([Phe(2),Ile(3),Hgn(4),Orn(iPr)(8)]vasopressin, where Hgn is homoglutamine and iPr is isopropyl), a peptidic analog of the vasoconstrictor hormone [Arg(8)]vasopressin (AVP), was designed to be a potent, selective, and short-acting vasopressin type 1a receptor (V(1a)R) agonist. In functional reporter gene assays, FE 202158 was a potent and selective human V(1a)R agonist [EC(50) = 2.4 nM; selectivity ratio of 1:142:1107:440 versus human vasopressin type 1b receptor, vasopressin type 2 receptor (V(2)R), and oxytocin receptor, respectively] contrasting with AVP's lack of selectivity, especially versus the V(2)R (selectivity ratio of 1:18:0.2:92; human V(1a)R EC(50) = 0.24 nM). This activity and selectivity profile was confirmed in radioligand binding assays. FE 202158 was a potent vasoconstrictor in the isolated rat common iliac artery ex vivo (EC(50) = 3.6 nM versus 0.8 nM for AVP) and reduced rat ear skin blood flow after intravenous infusion in vivo (ED(50) = 4.0 versus 3.4 pmol/kg/min for AVP). The duration of its vasopressor effect by intravenous bolus in rats was as short as AVP at submaximally effective doses. FE 202158 had no V(2)R-mediated antidiuretic activity in rats by intravenous infusion at its ED(50) for reduction of ear skin blood flow, in contrast with the pronounced antidiuretic effect of AVP. Thus, FE 202158 seems suitable for treatment of conditions where V(1a)R activity is desirable but V(2)R activity is potentially deleterious, such as vasodilatory hypotension in septic shock. In addition to the desirable selectivity profile, its short-acting nature should allow dose titration with rapid onset and offset of action to optimize vasoconstriction efficacy and safety. PMID:21411496

  14. Rescue therapy with terlipressin by continuous infusion in a child with catecholamine-resistant septic shock.

    PubMed

    Zeballos, Gonzalo; López-Herce, Jesús; Fernández, Carmen; Brandstrup, Kay B; Rodríguez-Núñez, Antonio

    2006-01-01

    A 2-month-old female infant presented with septic shock, refractory to high doses of catecholamines. Continuous infusion of terlipressin at a rate of 10 mcg/kgh produced a significant increase in the mean arterial pressure that was evident within half and hour, so allowing a reduction in the rate of catecholamine infusion. However, 18 h later, the blood pressure fell again and finally the patient died. This case shows the potential value of terlipressin infusion to restore normal mean arterial pressure in children with vasodilatory shock and hypotension refractory to catecholamines. PMID:16325320

  15. Part I. 3DPTV: Advances and error analysis. Part II. Extension of Guderley's solution for converging shock waves

    NASA Astrophysics Data System (ADS)

    Ponchaut, Nicolas F.

    This work is divided into two unrelated parts. In the first part, a full three-dimensional particle tracking system was developed and tested. Three images, from three separate CCDs placed at the vertices of an equilateral triangle, permit the three-dimensional location of particles to be determined by triangulation. Particle locations measured at two different times can then be used to create a three-component, three-dimensional velocity field. Key developments are the ability to accurately process overlapping particle images, offset CCDs to significantly improve effective resolution, treatment of dim particle images, and a hybrid particle tracking technique ideal for three-dimensional flows when only two sets of images exist. An in-depth theoretical error analysis was performed, which gives the important sources of error and their effect on the overall system. This error analysis was verified through a series of experiments, and a vortex flow measurement was performed. In the second part, the problem of a cylindrically or spherically imploding and reflecting shock wave in a flow initially at rest was examined. Guderley's strong shock solution around the origin was improved by adding two more terms in the series expansion solution for both the incoming and the reflected shock waves. A series expansion was also constructed for the case where the shock is still very far from the origin. In addition, a program based on the characteristics method was written. Thanks to an appropriate change of variables, the shock motion could be computed from virtually infinity to very close to the reflection point. Comparisons were made between the series expansions, the characteristics program, and the results obtained using an Euler solver. These comparisons showed that the addition of two terms to the Guderley solution significantly increases the accuracy of the series expansion.

  16. The vasodilatory effect of sulfur dioxide via SGC/cGMP/PKG pathway in association with sulfhydryl-dependent dimerization.

    PubMed

    Yao, Qiuyu; Huang, Yaqian; Liu, Angie Dong; Zhu, Mingzhu; Liu, Jia; Yan, Hui; Zhang, Qingyou; Geng, Bin; Gao, Yuansheng; Du, Shuxu; Huang, Pan; Tang, Chaoshu; Du, Junbao; Jin, Hongfang

    2016-06-01

    The present study was designed to explore the role of soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/PKG pathway in sulfur dioxide (SO2)-induced vasodilation. We showed that SO2 induced a concentration-dependent relaxation of phenylephrine (PE)-precontracted rat aortic rings in association with an increase in cGMP concentration, whereas l-aspartic acid β-hydroxamate (HDX), an inhibitor of SO2 synthase, contracted rings in a dose-dependent manner. Pretreatment of aortic rings with the sGC inhibitor ODQ (30 μM) attenuated the vasodilatory effects of SO2, suggesting the involvement of cGMP pathway in SO2-induced vasodilation. Mechanistically, SO2 upregulated the protein levels of sGC and PKG dimers, while HDX inhibited it, indicating SO2 could promote cGMP synthesis through sGC activation. Furthermore, the dimerization of sGC and PKG and vasodilation induced by SO2 in precontracted rings were significantly prevented by thiol reductants dithiothreitol (DTT). In addition, SO2 reduced the activity of phosphodiesterase type 5 (PDE5), a cGMP-specific hydrolytic enzyme, implying that SO2 elevated cGMP concentration by inhibiting its hydrolysis. Hence, SO2 exerted its vasodilatory effects at least partly by promoting disulfide-dependent dimerization of sGC and PKG, resulting in an activated sGC/cGMP/PKG pathway in blood vessels. These findings revealed a new mode of action and mechanisms by which SO2 regulated the vascular tone. PMID:27009048

  17. Echocardiography in shock management.

    PubMed

    McLean, Anthony S

    2016-01-01

    Echocardiography is pivotal in the diagnosis and management of the shocked patient. Important characteristics in the setting of shock are that it is non-invasive and can be rapidly applied.In the acute situation a basic study often yields immediate results allowing for the initiation of therapy, while a follow-up advanced study brings the advantage of further refining the diagnosis and providing an in-depth hemodynamic assessment. Competency in basic critical care echocardiography is now regarded as a mandatory part of critical care training with clear guidelines available. The majority of pathologies found in shocked patients are readily identified using basic level 2D and M-mode echocardiography. A more comprehensive diagnosis can be achieved with advanced levels of competency, for which practice guidelines are also now available. Hemodynamic evaluation and ongoing monitoring are possible with advanced levels of competency, which includes the use of colour Doppler, spectral Doppler, and tissue Doppler imaging and occasionally the use of more recent technological advances such as 3D or speckled tracking.The four core types of shock-cardiogenic, hypovolemic, obstructive, and vasoplegic-can readily be identified by echocardiography. Even within each of the main headings contained in the shock classification, a variety of pathologies may be the cause and echocardiography will differentiate which of these is responsible. Increasingly, as a result of more complex and elderly patients, the shock may be multifactorial, such as a combination of cardiogenic and septic shock or hypovolemia and ventricular outflow obstruction.The diagnostic benefit of echocardiography in the shocked patient is obvious. The increasing prevalence of critical care physicians experienced in advanced techniques means echocardiography often supplants the need for more invasive hemodynamic assessment and monitoring in shock. PMID:27543137

  18. Perioperative infusion of low- dose of vasopressin for prevention and management of vasodilatory vasoplegic syndrome in patients undergoing coronary artery bypass grafting-A double-blind randomized study

    PubMed Central

    2010-01-01

    Preoperative medication by inhibitors of angiotensin-converting enzyme (ACE) in coronary artery patients predisposes to vasoplegic shock early after coronary artery bypass grafting. Although in the majority of the cases this shock is mild, in some of them it appears as a situation, "intractable" to high-catecholamine dose medication. In this study we examined the possible role of prophylactic infusion of low-dose vasopressin, during and for the four hours post-bypass after cardiopulmonary bypass, in an effort to prevent this syndrome. In addition, we studied the influence of infused vasopressin on the hemodynamics of the patients, as well as on the postoperative urine-output and blood-loss. In our study 50 patients undergoing coronary artery bypass grafting were included in a blind-randomized basis. Two main criteria were used for the eligibility of patients for coronary artery bypass grafting: ejection fraction between 30-40%, and patients receiving ACE inhibitors, at least for four weeks preoperatively. The patients were randomly divided in two groups, the group A who were infused with 0.03 IU/min vasopressin and the group B who were infused with normal saline intraoperativelly and for the 4 postoperative hours. Measurements of mean artery pressure (MAP), central venous pressure (CVP), systemic vascular resistance (SVR), ejection fracture (EF), heart rate (HR), mean pulmonary artery pressure (MPAP), cardiac index (CI) and pulmonary vascular resistance (PVR) were performed before, during, and after the operation. The requirements of catecholamine support, the urine-output, the blood-loss, and the requirements in blood, plasma and platelets for the first 24 hours were included in the data collected. The incidence of vasodilatory shock was significantly lower (8% vs 20%) in group A and B respectively (p = 0,042). Generally, the mortality was 12%, exclusively deriving from group B. Postoperatively, significant higher values of MAP, CVP, SVR and EF were recorded in

  19. Perioperative infusion of low- dose of vasopressin for prevention and management of vasodilatory vasoplegic syndrome in patients undergoing coronary artery bypass grafting-A double-blind randomized study.

    PubMed

    Papadopoulos, Georgios; Sintou, Eleni; Siminelakis, Stavros; Koletsis, Efstratios; Baikoussis, Nikolaos G; Apostolakis, Efstratios

    2010-01-01

    Preoperative medication by inhibitors of angiotensin-converting enzyme (ACE) in coronary artery patients predisposes to vasoplegic shock early after coronary artery bypass grafting. Although in the majority of the cases this shock is mild, in some of them it appears as a situation, "intractable" to high-catecholamine dose medication. In this study we examined the possible role of prophylactic infusion of low-dose vasopressin, during and for the four hours post-bypass after cardiopulmonary bypass, in an effort to prevent this syndrome. In addition, we studied the influence of infused vasopressin on the hemodynamics of the patients, as well as on the postoperative urine-output and blood-loss. In our study 50 patients undergoing coronary artery bypass grafting were included in a blind-randomized basis. Two main criteria were used for the eligibility of patients for coronary artery bypass grafting: ejection fraction between 30-40%, and patients receiving ACE inhibitors, at least for four weeks preoperatively. The patients were randomly divided in two groups, the group A who were infused with 0.03 IU/min vasopressin and the group B who were infused with normal saline intraoperativelly and for the 4 postoperative hours. Measurements of mean artery pressure (MAP), central venous pressure (CVP), systemic vascular resistance (SVR), ejection fracture (EF), heart rate (HR), mean pulmonary artery pressure (MPAP), cardiac index (CI) and pulmonary vascular resistance (PVR) were performed before, during, and after the operation. The requirements of catecholamine support, the urine-output, the blood-loss, and the requirements in blood, plasma and platelets for the first 24 hours were included in the data collected. The incidence of vasodilatory shock was significantly lower (8% vs 20%) in group A and B respectively (p = 0,042). Generally, the mortality was 12%, exclusively deriving from group B. Postoperatively, significant higher values of MAP, CVP, SVR and EF were recorded in

  20. Antioxidant capacity and vasodilatory properties of Mediterranean food: the case of Cannonau wine, myrtle berries liqueur and strawberry-tree honey.

    PubMed

    Tuberoso, Carlo Ignazio Giovanni; Boban, Mladen; Bifulco, Ersilia; Budimir, Danijela; Pirisi, Filippo Maria

    2013-10-15

    The aim of this work was to use different assays to evaluate the antioxidant and vasodilatory properties of three typical food products from the Mediterranean area and to correlate these activities with their phenolic content. For this purpose, red wines Cannonau, liqueurs obtained by cold maceration of myrtle (Myrtus communis L.) berries and bitter honeys obtained from strawberry-tree flowers (Arbutus unedo L.) were analysed. The total phenolic (TP) content was measured spectrophotometrically with a modified Folin-Ciocalteau method and phenolic compounds were identified and dosed by HPLC-DAD and LC-MS/MS. Antioxidant activities were evaluated with DPPH, FRAP and ABTS assays and the in vitro vasodilatory effects were assessed using norepinephrine precontracted rat aortic rings. Cannonau wines and myrtle liqueurs showed high levels of TP (1978±279 and 1741±150mg GAE/L, respectively), linearly correlated to the results of FRAP, ABTS, and DPPH assays. Their maximal vasodilatory activity was 61.7±4.1% and 53.0±3.0%, respectively. Although strawberry-tree honey contained relatively high levels of phenolic compounds (922±38mg GAE/kg), it did not induce vasodilation, even at the highest dose tested (0.206g/L). These results indicate that foods with high levels of phenolic compounds should be studied using several different biological assays before being recommended to the general public as functional foods. PMID:23692754

  1. Cardiogenic shock

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000185.htm Cardiogenic shock To use the sharing features on this page, please enable JavaScript. Cardiogenic shock is when the heart has been damaged so ...

  2. Septic shock

    MedlinePlus

    Septic shock is a serious condition that occurs when a body-wide infection leads to dangerously low blood ... Septic shock occurs most often in the very old and the very young. It may also occur in ...

  3. Induction of hyaluronic acid synthase 2 (HAS2) in human vascular smooth muscle cells by vasodilatory prostaglandins.

    PubMed

    Sussmann, M; Sarbia, M; Meyer-Kirchrath, J; Nüsing, R M; Schrör, K; Fischer, J W

    2004-03-19

    Hyaluronic acid (HA) is a prominent constituent of the extracellular matrix of atherosclerotic vascular lesions in humans known to modulate vascular smooth muscle phenotype. The regulation of HA synthesis by vasodilatory prostaglandins was analyzed in human arterial smooth muscle cells (SMCs). The prostacyclin analogue, iloprost (100 nmol/L), markedly increased pericellular formation of HA coats and HA secretion into the cell culture medium in human arterial SMCs (8.7+/-1.6-fold). Expression of HA synthase 2 (HAS2) was determined by semiquantitative RT-PCR and found to be strongly upregulated at concentrations of iloprost between 1 and 100 nmol/L after 3 hours. Furthermore, endogenous cyclooxygenase-2 (COX2) activity was required for basal expression of HAS2 mRNA in SMCs in vitro. Total HA secretion in response to iloprost was markedly decreased by RNA interference (RNAi), specific for HAS2. In addition, siRNA targeting HAS2 strongly increased the spreading of human SMCs compared with mock-transfected cells. HAS2 mRNA levels were also stimulated by a selective prostacyclin receptor (IP) agonist, cicaprost (10 nmol/L), prostaglandin E(2) (10 nmol/L), and the EP(2) receptor agonist, butaprost (1 micromol/L). Induction of HAS2 mRNA and HA synthesis by prostaglandins was mimicked by stable cAMP analogues and forskolin. In human atherectomy specimens from the internal carotid artery, HA deposits and COX2 expression colocalized frequently. In addition, strong EP(2) receptor expression was detected in SMCs in HA-rich areas. Therefore, upregulation of HAS2 expression via EP(2) and IP receptors might contribute to the accumulation of HA during human atherosclerosis, thereby mediating proatherosclerotic functions of COX2. PMID:14752026

  4. Endothelium-dependent mechanisms of the vasodilatory effect of the endocannabinoid, anandamide, in the rat pulmonary artery.

    PubMed

    Baranowska-Kuczko, Marta; MacLean, Margaret R; Kozłowska, Hanna; Malinowska, Barbara

    2012-09-01

    Endocannabinoids exhibit vasodilatory properties and reduce blood pressure in vivo. However, the influence and mechanism of action of the prominent endocannabinoid, anandamide (AEA), in pulmonary arteries are not known. The present study determined the vascular response to AEA in isolated rat pulmonary arteries. AEA relaxed rat pulmonary arteries that were pre-constricted with U-46619. This relaxation was reduced by the following conditions:removal of the endothelium; in KCl pre-constricted preparations; in the presence of the potassium channel (K(Ca)) blockers, tetraethylammonium and the combination of charybdotoxin and apamin, and the prostacyclin receptor antagonist, RO1138452. Inhibitors of cyclooxygenase (indomethacin), nitric oxide (NO) synthase (N(G)-nitro-l-arginine methyl ester) and fatty acid amide hydrolase (URB597) alone or in combination diminished AEA-induced relaxation in endothelium-intact vessels. The remaining experiments were performed in the presence of URB597 to eliminate the influence of AEA metabolites. Antagonists of the endothelial cannabinoid receptor (CB(x)), O-1918 and cannabidiol, attenuated the AEA-induced response. Antagonists of CB(1), CB(2) and TRPV1 receptors, AM251, AM630 and capsazepine, respectively, did not modify the AEA-induced response. A reference activator of CB(x) receptors, abnormal cannabidiol, mimicked the receptor-mediated AEA effects. The present study demonstrated that AEA relaxed rat pulmonary arteries in an endothelium-dependent fashion via the activation of the O-1918-sensitive CB(x) receptor and/or prostacyclin-like vasoactive products of AEA. One or both of these mechanisms may involve K(Ca) or the NO pathway. PMID:22627170

  5. Superdiffusive shock acceleration and short acceleration times at interplanetary shocks

    NASA Astrophysics Data System (ADS)

    Perri, Silvia; Zimbardo, Gaetano

    2016-04-01

    The analysis of time profiles of particles accelerated at interplanetary shock waves has shown evidence for superdiffusive transport in the upstream region. Superdiffusive transport is characterized by a mean square displacement that grows faster than linearly in time and by non Gaussian statistics for the distribution of the particle jump lengths. In the superdiffusive framework it has been shown that particle time profiles upstream of a planar shock decay as power laws, at variance with exponential particle time profiles predicted in the case of diffusive transport. A large number of interplanetary shocks, including coronal mass ejection driven shocks, exhibit energetic particle time profiles that decay as power laws far upstream. In order to take this evidence into account, we have extended the standard theory of diffusive shock acceleration to the case of particle superdiffusive transport (superdiffusive shock acceleration). This has allowed us to derive both hard energy spectral indices and short acceleration times. This new theory has been tested for a number of interplanetary shock waves, observed by the Ulysses and the ACE spacecraft, and for the termination shock. The superdiffusive shock acceleration leads to a strong reduction of the acceleration times (even of about one order of magnitude) with respect to the diffusive shock acceleration. Thus, this new framework provides a substantial advancement in the understanding of the processes of particle acceleration and particle transport, which are among the main objectives of the new Solar Probe and Solar Orbiter space missions.

  6. AOTV bow shock location

    NASA Technical Reports Server (NTRS)

    Desautel, D.

    1985-01-01

    Hypersonic bow-shock location and geometry are of central importance to the aerodynamics and aerothermodynamics of aeroassisted orbital transfer vehicles (AOTVs), but they are difficult to predict for a given vehicle configuration. This paper reports experimental measurements of shock standoff distance for the 70 deg cone AOTV configuration in shock-tunnel-test flows at Mach numbers of 3.8 to 7.9 and for angles of attack from 0 deg to 20 deg. The controlling parameter for hypersonic bow-shock standoff distance (for a given forebody shape) is the mean normal-shock density ratio. Values for this parameter in the tests reported are in the same range as those of the drag-brake AOTV perigee regime. Results for standoff distance are compared with those previously reported in the literature for this AOTV configuration. It is concluded that the AOTV shock standoff distance for the conical configuration, based on frustrum (base) radius, is equivalent to that of a sphere with a radius about 35 percent greater than that of the cone; the distance is, therefore, much less than reported in previous studies. Some reasons for the discrepancies between the present and previous are advanced. The smaller standoff distance determined here implies there will be less radiative heat transfer than was previously expected.

  7. Aging Reduces L-Type Calcium Channel Current and the Vasodilatory Response of Small Mesenteric Arteries to Calcium Channel Blockers

    PubMed Central

    Albarwani, Sulayma A.; Mansour, Fathi; Khan, Abdul Aleem; Al-Lawati, Intisar; Al-Kaabi, Abdulla; Al-Busaidi, Al-Manar; Al-Hadhrami, Safa; Al-Husseini, Isehaq; Al-Siyabi, Sultan; Tanira, Musbah O.

    2016-01-01

    Calcium channel blockers (CCBs) are widely used to treat cardiovascular disease (CVD) including hypertension. As aging is an independent risk factor for CVD, the use of CCBs increases with increasing age. Hence, this study was designed to evaluate the effect of aging on the sensitivity of small mesenteric arteries to L-type voltage-gated calcium channel (LTCC) blockers and also to investigate whether there was a concomitant change in calcium current density. Third order mesenteric arteries from male F344 rats, aged 2.5–3 months (young) and 22–26 months (old) were mounted on wire myograph to measure the tension during isometric contraction. Arteries were contracted with 100 mM KCl and were then relaxed in a cumulative concentration-response dependent manner with nifedipine (0.1 nM–1 μM), verapamil (0.1 nM–10 μM), or diltiazem (0.1 nM–10 μM). Relaxation-concentration response curves produced by cumulative concentrations of three different CCBs in arteries of old rats were shifted to the right with statistically significant IC50s. pIC50 ± s.e.m: (8.37 ± 0.06 vs. 8.04 ± 0.05, 7.40 ± 0.07 vs. 6.81 ± 0.04, and 6.58 ± 0.07 vs. 6.34 ± 0.06) in young vs. old. It was observed that the maximal contractions induced by phenylephrine and reversed by sodium nitroprusside were not different between young and old groups. However, Bay K 8644 (1 μM) increased resting tension by 23 ± 4.8% in young arteries and 4.7 ± 1.6% in old arteries. LTCC current density were also significantly lower in old arteries (−2.77 ± 0.45 pA/pF) compared to young arteries (−4.5 ± 0.40 pA/pF); with similar steady-state activation and inactivation curves. Parallel to this reduction, the expression of Cav1.2 protein was reduced by 57 ± 5% in arteries from old rats compared to those from young rats. In conclusion, our results suggest that aging reduces the response of small mesenteric arteries to the vasodilatory effect of the CCBs and this may be due to, at least in part, reduced

  8. Hesperidin metabolite hesperetin-7-O-glucuronide, but not hesperetin-3'-O-glucuronide, exerts hypotensive, vasodilatory, and anti-inflammatory activities.

    PubMed

    Yamamoto, Masaki; Jokura, Hiroko; Hashizume, Koujiro; Ominami, Hideo; Shibuya, Yusuke; Suzuki, Atsushi; Hase, Tadashi; Shimotoyodome, Akira

    2013-09-01

    Orally ingested hesperidin (HES) is hydrolyzed into hesperetin in the gastrointestinal tract and conjugated during absorption. Hesperetin conjugates are the main circulating metabolites in human and rat plasma. We previously reported that glucosyl hesperidin (GHES), a water-soluble HES derivative, prevents hypertension via improvement of endothelial dysfunction in spontaneously hypertensive rats (SHRs). Although these hesperetin conjugates seem to be responsible for hypotensive and endothelium-dependent vasodilatory activities of dietary GHES, little is known about the mechanisms of action of these conjugated metabolites. Therefore, the aim of the present study was to investigate the effects of hesperetin-7-O-β-d-glucuronide (HPT7G) and hesperetin-3'-O-β-d-glucuronide (HPT3'G), which are the predominant HES metabolites in rat plasma, on blood pressure and endothelial function. Intravenous administration of HPT7G (5 mg kg(-1)) decreased blood pressure in anesthetized SHRs. HPT7G enhanced endothelium-dependent vasodilation in response to acetylcholine, but had no effect on endothelium-independent vasodilation in response to sodium nitroprusside (SNP) in aortas isolated from SHRs. HPT7G decreased hydrogen peroxide-induced intracellular adhesion molecule-1 and monocyte chemoattractant protein-1 mRNA expression in rat aortic endothelial cells. In contrast, HPT3'G had little effect on these parameters. In conclusion, HPT7G exerted hypotensive, vasodilatory and anti-inflammatory activities, similar to hesperetin and these effects are associated, in part, with the activity of GHES and HES to improve hypertension and endothelial dysfunction. PMID:23831969

  9. Evaluation of the cerebral vasodilatory capacity by the acetazolamide test before EC-IC bypass surgery in patients with occlusion of the internal carotid artery

    SciTech Connect

    Vorstrup, S.; Brun, B.; Lassen, N.A.

    1986-11-01

    Cerebral blood flow (CBF) was measured by xenon-133 inhalation tomography in 18 patients with cerebrovascular disease before and 4 months after extracranial-intracranial bypass surgery. Only patients who showed a reduced CBF in areas that were intact on the CT scan and relevant to the clinical and angiographical findings were operated. The majority of the patients had suffered a minor stroke with or without subsequent transient ischemic attacks. They were studied at least 6 weeks following the stroke. All patients had an occlusion of the relevant internal carotid artery. To identify preoperatively the patients with a compromised collateral circulation and hence reduced CBF due to reduced perfusion pressure, a cerebral vasodilatory stress test was performed using acetazolamide (Diamox). In normal subjects, Diamox has been shown to increase tomographic CBF without change of the flow distribution. In the present series 9 patients showed a significant redistribution of flow in favor of the non-occluded side (positive Diamox test). Two of these 9 patients showed even a paradoxical decrease in focal CBF preoperatively, i.e., a steal effect. These 2 patients were the only patients who improved in focal CBF after shunting. The remaining 9 patients all showed uniform flow responses (negative Diamox test), and none of these increased in focal CBF postoperatively. The finding of an unchanged flow map postoperatively confirmed that the low flow areas were not due to restricted flow via collateral pathways. However, an increase in the regional vasodilatory capacity was observed postoperatively in the majority of patients.

  10. Evaluation of the cerebral vasodilatory capacity by the acetazolamide test before EC-IC bypass surgery in patients with occlusion of the internal carotid artery.

    PubMed

    Vorstrup, S; Brun, B; Lassen, N A

    1986-01-01

    Cerebral blood flow (CBF) was measured by xenon-133 inhalation tomography in 18 patients with cerebrovascular disease before and 4 months after extracranial-intracranial bypass surgery. Only patients who showed a reduced CBF in areas that were intact on the CT scan and relevant to the clinical and angiographical findings were operated. The majority of the patients had suffered a minor stroke with or without subsequent transient ischemic attacks. They were studied at least 6 weeks following the stroke. All patients had an occlusion of the relevant internal carotid artery. To identify preoperatively the patients with a compromised collateral circulation and hence reduced CBF due to reduced perfusion pressure, a cerebral vasodilatory stress test was performed using acetazolamide (Diamox). In normal subjects, Diamox has been shown to increase tomographic CBF without change of the flow distribution. In the present series 9 patients showed a significant redistribution of flow in favor of the non-occluded side ("positive" Diamox test). Two of these 9 patients showed even a paradoxical decrease in focal CBF preoperatively, i.e., a "steal" effect. These 2 patients were the only patients who improved in focal CBF after shunting. The remaining 9 patients all showed uniform flow responses ("negative" Diamox test), and none of these increased in focal CBF postoperatively. The finding of an unchanged flow map postoperatively confirmed that the low flow areas were not due to restricted flow via collateral pathways. However, an increase in the regional vasodilatory capacity was observed postoperatively in the majority of patients. PMID:3492787

  11. Hypovolemic shock

    MedlinePlus

    ... clammy skin Confusion Decreased or no urine output General weakness Pale skin color (pallor) Rapid breathing Sweating , moist skin Unconsciousness The greater and more rapid the blood loss, the more severe the symptoms of shock.

  12. Study of the effect of thiols on the vasodilatory potency of S-nitrosothiols by using a modified aortic ring assay

    SciTech Connect

    Giustarini, Daniela; Tsikas, Dimitrios; Rossi, Ranieri

    2011-10-15

    Both low-molecular-mass thiols (LMM-SH) and protein thiols (P-SH) can modulate the biological activity of S-nitrosothiols (RSNO) via S-transnitrosation reactions. It has been difficult to evaluate the entity of this effect in blood circulation by in vitro assays with isolated aorta rings so far, because media rich in proteins cannot be used due to the foaming as a consequence of the needed gas bubbling. We have modified the original apparatus for organ bioassay in order to minimize foaming and to increase analytical performance. By using this modified bioassay we investigated the vasodilatory potency of various endogenous RSNOs in the presence of physiologically relevant concentrations of albumin and LMM-SH. Our results show that the sulfhydryl group of the cysteine moiety of albumin and LMM-SH has a dramatic effect on the vasodilatory potency of RSNO. Considering the equilibrium constants for S-transnitrosation reactions and the concentration of P-SH and LMM-SH we measured in healthy humans (aged 18-85 years), we infer that the age-dependency of hematic levels of LMM-SH may have a considerable impact in RSNO-mediated vasodilation. S-Nitrosoproteins such as S-nitrosoalbumin may constitute a relatively silent and constant amount of circulating RSNO. On the other hand, LMM-SH may mediate and control the biological actions of S-nitrosoproteins via S-transnitrosation reactions, by forming more potent nitric oxide-releasing LMM-S-nitrosothiols. Lifestyle habits, status of health and individual age are proven factors that, in turn, may influence the concentration of these compounds. These aspects should be taken into consideration when testing the vasodilatory effects of RSNO in pre-clinical studies. - Highlights: > A modification of the organ chamber apparatus for aortic ring bioassays is proposed. > The new apparatus can work in the presence of albumin at physiological concentrations. > Potency of RSNOs was studied in the presence of albumin and low molecular mass -SH

  13. Cellular Alterations in Shock and Ischemia and Their Correction.

    ERIC Educational Resources Information Center

    Chaudry, Irshad H.

    1985-01-01

    Reviews recent advances in cellular alterations in shock to help physicians and physiologists keep abreast of current research. Specifically addresses changes occurring as a result of hemorrhagic shock and possible ways such lesions could be corrected. (DH)

  14. [Obstructive shock].

    PubMed

    Pich, H; Heller, A R

    2015-05-01

    An acute obstruction of blood flow in central vessels of the systemic or pulmonary circulation causes the clinical symptoms of shock accompanied by disturbances of consciousness, centralization, oliguria, hypotension and tachycardia. In the case of an acute pulmonary embolism an intravascular occlusion results in an acute increase of the right ventricular afterload. In the case of a tension pneumothorax, an obstruction of the blood vessels supplying the heart is caused by an increase in extravascular pressure. From a hemodynamic viewpoint circulatory shock caused by obstruction is closely followed by cardiac deterioration; however, etiological and therapeutic options necessitate demarcation of cardiac from non-cardiac obstructive causes. The high dynamics of this potentially life-threatening condition is a hallmark of all types of obstructive shock. This requires an expeditious and purposeful diagnosis and a rapid and well-aimed therapy. PMID:25994928

  15. [Neurogenic shock].

    PubMed

    Meister, Rafael; Pasquier, Mathieu; Clerc, David; Carron, Pierre-Nicolas

    2014-08-13

    The neurogenic shock is a common complication of spinal cord injury, especially when localized at the cervical level. Characterized by a vasoplegia (hypotension) and bradycardia, the neurogenic shock is secondary to the damage of the sympathetic nervous system. The clinical presentation often includes tetraplegia, with or without respiratory failure. Early treatment aims to minimize the occurrence of secondary spinal cord lesions resulting from systemic ischemic injuries. Medical management consists in a standardized ABCDE approach, in order to stabilize vital functions and immobilize the spine. The hospital care includes performing imaging, further measures of neuro-resuscitation, and coordinated surgical assessment and treatment of any other injury. PMID:25199226

  16. Interstellar shock waves

    NASA Technical Reports Server (NTRS)

    Mckee, C. F.; Hollenbach, D. J.

    1980-01-01

    The structure of interstellar shocks driven by supernova remnants and by expanding H II regions around early-type stars is discussed. Jump conditions are examined, along with shock fronts, post-shock relaxation layers, collisional shocks, collisionless shocks, nonradiative shocks, radiative atomic shocks, and shock models of observed nebulae. Effects of shock waves on interstellar molecules are examined, with reference to the chemistry behind shock fronts, infrared and vibrational-rotational cooling by molecules, and observations of shocked molecules. Some current problems and applications of the study of interstellar shocks are summarized, including the initiation of star formation by radiative shock waves, interstellar masers, the stability of shocks, particle acceleration in shocks, and shocks in galactic nuclei.

  17. Shock Prevention

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The electrician pictured is installing a General Electric Ground Fault Interrupter (GFI), a device which provides protection against electrical shock in the home or in industrial facilities. Shocks due to defective wiring in home appliances or other electrical equipment can cause severe burns, even death. As a result, the National Electrical Code now requires GFIs in all new homes constructed. This particular type of GFI employs a sensing element which derives from technology acquired in space projects by SCI Systems, Inc., Huntsville, Alabama, producer of sensors for GE and other manufacturers of GFI equipment. The sensor is based on the company's experience in developing miniaturized circuitry for space telemetry and other spacecraft electrical systems; this experience enabled SCI to package interruptor circuitry in the extremely limited space available and to produce sensory devices at practicable cost. The tiny sensor measures the strength of the electrical current and detects current differentials that indicate a fault in the functioning of an electrical system. The sensing element then triggers a signal to a disconnect mechanism in the GFI, which cuts off the current in the faulty circuit.

  18. What Is Cardiogenic Shock?

    MedlinePlus

    ... page from the NHLBI on Twitter. What Is Cardiogenic Shock? Cardiogenic (kar-dee-oh-JE-nik) shock is ... treated right away. The most common cause of cardiogenic shock is damage to the heart muscle from a ...

  19. Supersonic jet shock noise reduction

    NASA Technical Reports Server (NTRS)

    Stone, J. R.

    1984-01-01

    Shock-cell noise is identified to be a potentially significant problem for advanced supersonic aircraft at takeoff. Therefore NASA conducted fundamental studies of the phenomena involved and model-scale experiments aimed at developing means of noise reduction. The results of a series of studies conducted to determine means by which supersonic jet shock noise can be reduced to acceptable levels for advanced supersonic cruise aircraft are reviewed. Theoretical studies were conducted on the shock associated noise of supersonic jets from convergent-divergent (C-D) nozzles. Laboratory studies were conducted on the influence of narrowband shock screech on broadband noise and on means of screech reduction. The usefulness of C-D nozzle passages was investigated at model scale for single-stream and dual-stream nozzles. The effect of off-design pressure ratio was determined under static and simulated flight conditions for jet temperatures up to 960 K. Annular and coannular flow passages with center plugs and multi-element suppressor nozzles were evaluated, and the effect of plug tip geometry was established. In addition to the far-field acoustic data, mean and turbulent velocity distributions were measured with a laser velocimeter, and shadowgraph images of the flow field were obtained.

  20. Particle Acceleration in Shock-Shock Interaction

    NASA Astrophysics Data System (ADS)

    Nakanotani, Masaru; Matsukiyo, Shuichi; Hada, Tohru

    2015-04-01

    Collisionless shock waves play a crucial role in producing high energy particles. One of the most plausible acceleration mechanisms is the first order Fermi acceleration in which non-thermal particles statistically gain energy while scattered by MHD turbulence both upstream and downstream of a shock. Indeed, X-ray emission from energetic particles accelerated at supernova remnant shocks is often observed [e.g., Uchiyama et al., 2007]. Most of the previous studies on shock acceleration assume the presence of a single shock. In space, however, two shocks frequently come close to or even collide with each other. For instance, it is observed that a CME (coronal mass ejection) driven shock collides with the earth's bow shock [Hietala et al., 2011], or interplanetary shocks pass through the heliospheric termination shock [Lu et al., 1999]. Colliding shocks are observed also in high power laser experiments [Morita et al., 2013]. It is expected that shock-shock interactions efficiently produce high energy particles. A previous work using hybrid simulation [Cargill et al., 1986] reports efficient ion acceleration when supercritical two shocks collide. In the hybrid simulation, however, the electron dynamics cannot be resolved so that electron acceleration cannot be discussed in principle. Here, we perform one-dimensional full Particle-in-Cell (PIC) simulations to examine colliding two symmetric oblique shocks and the associated electron acceleration. In particular, the following three points are discussed in detail. 1. Energetic electrons are observed upstream of the two shocks before their collision. These energetic electrons are efficiently accelerated through multiple reflections at the two shocks (Fermi acceleration). 2. The reflected electrons excite large amplitude upstream waves. Electron beam cyclotron instability [Hasegawa, 1975] and electron fire hose instability [Li et al., 2000] appear to occur. 3. The large amplitude waves can scatters energetic electrons in

  1. Shock waves and shock tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985

    NASA Technical Reports Server (NTRS)

    Bershader, D. (Editor); Hanson, R. (Editor)

    1986-01-01

    A detailed survey is presented of shock tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore shock tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to shock wave phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, shock wave and rarefaction wave characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in shock tubes. Shock interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of shocks in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a shock wave are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.

  2. Radiative Shock Waves In Emerging Shocks

    NASA Astrophysics Data System (ADS)

    Drake, R. Paul; Doss, F.; Visco, A.

    2011-05-01

    In laboratory experiments we produce radiative shock waves having dense, thin shells. These shocks are similar to shocks emerging from optically thick environments in astrophysics in that they are strongly radiative with optically thick shocked layers and optically thin or intermediate downstream layers through which radiation readily escapes. Examples include shocks breaking out of a Type II supernova (SN) and the radiative reverse shock during the early phases of the SN remnant produced by a red supergiant star. We produce these shocks by driving a low-Z plasma piston (Be) at > 100 km/s into Xe gas at 1.1 atm. pressure. The shocked Xe collapses to > 20 times its initial density. Measurements of structure by radiography and temperature by several methods confirm that the shock wave is strongly radiative. We observe small-scale perturbations in the post-shock layer, modulating the shock and material interfaces. We describe a variation of the Vishniac instability theory of decelerating shocks and an analysis of associated scaling relations to account for the growth of these perturbations, identify how they scale to astrophysical systems such as SN 1993J, and consider possible future experiments. Collaborators in this work have included H.F. Robey, J.P. Hughes, C.C. Kuranz, C.M. Huntington, S.H. Glenzer, T. Doeppner, D.H. Froula, M.J. Grosskopf, and D.C. Marion ________________________________ * Supported by the US DOE NNSA under the Predictive Sci. Academic Alliance Program by grant DE-FC52-08NA28616, the Stewardship Sci. Academic Alliances program by grant DE-FG52-04NA00064, and the Nat. Laser User Facility by grant DE-FG03-00SF22021.

  3. A Phase I study of the Heat Shock Protein 90 inhibitor alvespimycin (17-DMAG) given intravenously to patients with advanced solid tumors

    PubMed Central

    Pacey, Simon; Wilson, Richard H.; Walton, Mike; Eatock, Martin M.; Hardcastle, Anthea; Zetterlund, Anna; Arkenau, Hendrik-Tobias; Moreno-Farre, Javier; Banerji, Udai; Roels, Belle; Peachey, Heidi; Aherne, Wynne; de Bono, Johan S.; Raynaud, Florence; Workman, Paul; Judson, Ian

    2010-01-01

    Purpose A Phase I study to define toxicity and recommend a Phase II dose of the HSP90 inhibitor alvespimycin (17-DMAG; 17-dimethylaminoethylamino-17-demethoxygeldanamycin). Secondary endpoints included evaluation of pharmacokinetic profile, tumor response and definition of a biologically effective dose (BED). Patients and Methods Patients with advanced solid cancers were treated with weekly, intravenous (IV) 17-DMAG. An accelerated titration dose escalation design was used. The maximum tolerated dose (MTD) was the highest dose at which ≤ 1/6 patients experienced dose limiting toxicity (DLT). Dose de-escalation from the MTD was planned with mandatory, sequential tumor biopsies to determine a BED. Pharmacokinetic and pharmacodynamic assays were validated prior to patient accrual. Results Twenty five patients received 17-DMAG (range 2.5 to 106 mg/m2). At 106mg/m2 of 17-DMAG 2/4 patients experienced DLT, including one treatment related death. No DLT occurred at 80mg/m2. Common adverse events were gastrointestinal, liver function changes and ocular. AUC and Cmax increased proportionally with 17-DMAG doses ≤ 80mg/m2. In peripheral blood mononuclear cells significant (p <0.05) HSP72 induction was detected (≥ 20mg/m2) and sustained for 96 hours (≥ 40mg/m2). Plasma HSP72 levels were greatest in the two patients who experienced DLT. At 80mg/m2 client protein (CDK4, LCK) depletion was detected and tumor samples from 3/5 patients confirmed HSP90 inhibition. Clinical activity included complete response (castration refractory prostate cancer, CRPC 124 weeks), partial response (melanoma, 159 weeks) and stable disease (chondrosarcoma, CRPC and renal cancer for 28, 59 and 76 weeks respectively). Conclusion The recommended Phase II dose of 17-DMAG is 80mg/m2 weekly, IV. PMID:21278242

  4. Neptune inbound bow shock

    NASA Technical Reports Server (NTRS)

    Szabo, Adam; Lepping, Ronald P.

    1995-01-01

    Voyager 2 crossed the inbound or upstream Neptunian bow shock at 1430 spacecraft event time on August 24 in 1989 (Belcher et al., 1989). The plasma and magnetic field measurements allow us to study the solar wind interaction with the outermost gas giant. To fully utilize all of the spacecraft observations, an improved nonlinear least squares, 'Rankine-Hugoniot' magnetohydrodynamic shock-fitting technique has been developed (Szabo, 1994). This technique is applied to the Neptunian data set. We find that the upstream bow shock normal points nearly exactly toward the Sun consistent with any reasonable large-scale model of the bow shock for a near subsolar crossing. The shock was moving outward with a speed of 14 +/- 12 km/s. The shock can be characterized as a low beta, high Mach number, strong quasi-perpendicular shock. Finally, the shock microstructure features are resolved and found to scale well with theoretical expectations.

  5. Cardiogenic Shock: Failure of Oxygen Delivery and Oxygen Utilization.

    PubMed

    Lim, Hoong Sern

    2016-08-01

    Cardiogenic shock remains a highly lethal condition. Conventional therapy including revascularization and mechanical circulatory support aims to improve cardiac output and oxygen delivery, but increasing basic and clinical observations indicate wider circulatory and cellular abnormalities, particularly at the advanced stages of shock. Progressive cardiogenic shock is associated with microcirculatory and cellular abnormalities. Cardiogenic shock is initially characterized by a failure to maintain global oxygen delivery; however, progressive cardiogenic shock is associated with the release of pro-inflammatory cytokines, derangement of the regulation of regional blood flow, microcirculatory abnormalities, and cellular dysoxia. These abnormalities are analogous to septic shock and may not be reversed by increase in oxygen delivery, even to supranormal levels. Earlier mechanical circulatory support in cardiogenic shock may limit the development of microcirculatory and cellular abnormalities. PMID:27509355

  6. Biomass shock pretreatment

    DOEpatents

    Holtzapple, Mark T.; Madison, Maxine Jones; Ramirez, Rocio Sierra; Deimund, Mark A.; Falls, Matthew; Dunkelman, John J.

    2014-07-01

    Methods and apparatus for treating biomass that may include introducing a biomass to a chamber; exposing the biomass in the chamber to a shock event to produce a shocked biomass; and transferring the shocked biomass from the chamber. In some aspects, the method may include pretreating the biomass with a chemical before introducing the biomass to the chamber and/or after transferring shocked biomass from the chamber.

  7. Skin necrosis after a low-dose vasopressin infusion through a central venous catheter for treating septic shock.

    PubMed

    Kim, Eun Hee; Lee, Sae Hwan; Byun, Seung Woon; Kang, Ho Suk; Koo, Dong Hoe; Park, Hyun-Gu; Hong, Sang Bum

    2006-12-01

    This is a report on a case of severe skin necrosis in a vasodilatory septic shock patient after the infusion of low-dose vasopressin through a central venous catheter. An 84-year-old male was hospitalized for edema on both legs at Asan Medical Center, Seoul, Korea. On hospital day 8, the patient began to complain of dyspnea and he subsequently developed severe septic shock caused by E. coli. After being transferred to the medical intensive care unit, his hypotension, which was refractory to norepinephrine, was controlled by an infusion of low-dose vasopressin (0.02 unit/min) through a central venous catheter into the right subclavian vein. After the infusion of low-dose vasopressin, severe skin necrosis with bullous changes developed, necessitating discontinuation of the low-dose vasopressin infusion. The patient expired from refractory septic shock. Although low-dose vasopressin can control hypotension in septic shock patients, low-dose vasopressin must be used with caution because ischemic complications such as skin necrosis can develop even with administration through a central venous catheter. PMID:17249516

  8. What Causes Cardiogenic Shock?

    MedlinePlus

    ... page from the NHLBI on Twitter. What Causes Cardiogenic Shock? Immediate Causes Cardiogenic shock occurs if the heart suddenly can't pump ... to the body. The most common cause of cardiogenic shock is damage to the heart muscle from a ...

  9. Relativistic Shocks: Particle Acceleration and Magnetization

    NASA Astrophysics Data System (ADS)

    Sironi, L.; Keshet, U.; Lemoine, M.

    2015-10-01

    We review the physics of relativistic shocks, which are often invoked as the sources of non-thermal particles in pulsar wind nebulae (PWNe), gamma-ray bursts (GRBs), and active galactic nuclei (AGN) jets, and as possible sources of ultra-high energy cosmic-rays. We focus on particle acceleration and magnetic field generation, and describe the recent progress in the field driven by theory advances and by the rapid development of particle-in-cell (PIC) simulations. In weakly magnetized or quasi parallel-shocks (i.e. where the magnetic field is nearly aligned with the flow), particle acceleration is efficient. The accelerated particles stream ahead of the shock, where they generate strong magnetic waves which in turn scatter the particles back and forth across the shock, mediating their acceleration. In contrast, in strongly magnetized quasi-perpendicular shocks, the efficiencies of both particle acceleration and magnetic field generation are suppressed. Particle acceleration, when efficient, modifies the turbulence around the shock on a long time scale, and the accelerated particles have a characteristic energy spectral index of s_{γ}˜eq2.2 in the ultra-relativistic limit. We discuss how this novel understanding of particle acceleration and magnetic field generation in relativistic shocks can be applied to high-energy astrophysical phenomena, with an emphasis on PWNe and GRB afterglows.

  10. Simulating radiative shocks in nozzle shock tubes

    NASA Astrophysics Data System (ADS)

    van der Holst, B.; Tóth, G.; Sokolov, I. V.; Daldorff, L. K. S.; Powell, K. G.; Drake, R. P.

    2012-06-01

    We use the recently developed Center for Radiative Shock Hydrodynamics (CRASH) code to numerically simulate laser-driven radiative shock experiments. These shocks are launched by an ablated beryllium disk and are driven down xenon-filled plastic tubes. The simulations are initialized by the two-dimensional version of the Lagrangian Hyades code which is used to evaluate the laser energy deposition during the first 1.1 ns. Later times are calculated with the CRASH code. CRASH solves for the multi-material hydrodynamics with separate electron and ion temperatures on an Eulerian block-adaptive-mesh and includes a multi-group flux-limited radiation diffusion and electron thermal heat conduction. The goal of the present paper is to demonstrate the capability to simulate radiative shocks of essentially three-dimensional experimental configurations, such as circular and elliptical nozzles. We show that the compound shock structure of the primary and wall shock is captured and verify that the shock properties are consistent with order-of-magnitude estimates. The synthetic radiographs produced can be used for comparison with future nozzle experiments at high-energy-density laser facilities.

  11. New radiative shocks experiment

    NASA Astrophysics Data System (ADS)

    Leygnac, S.; Bouquet, S.; Stehlé, C.; Benuzzi, A.; Boireau, J.-P.; Chièze, J.-P.; Grandjouan, N.; Huser, G.; Koenig, M.; Malka, V.; Merdji, H.; Michaut, C.; Thais, F.; Vinci, T.

    2002-06-01

    An experimental study of shocks with astrophysical relevance is performed with the high energy density laser of the LULI, at the Ecole Polytechnique. The peculiarity of these shocks is the strong coupling between radiation and hydrodynamics which leads to a structure governed by a radiative precursor. A new experiment has been performed this year where we have observed shocks identified as radiative shocks. We study them in various experimental configurations (several speeds and geometries of the medium where the shock propagates, allowing a quasi-planar or a quasi-spherical expansion). From the measurements it is possible to infer several features of the shock such as the speed, the electronic density, the geometrical shape and spectroscopic informations. The results will be studied with numerical simulations.

  12. Shock Initiation of Heterogeneous Explosives

    SciTech Connect

    Reaugh, J E

    2004-05-10

    The fundamental picture that shock initiation in heterogeneous explosives is caused by the linking of hot spots formed at inhomogeneities was put forward by several researchers in the 1950's and 1960's, and more recently. Our work uses the computer hardware and software developed in the Advanced Simulation and Computing (ASC) program of the U.S. Department of Energy to explicitly include heterogeneities at the scale of the explosive grains and to calculate the consequences of realistic although approximate models of explosive behavior. Our simulations are performed with ALE-3D, a three-dimensional, elastic-plastic-hydrodynamic Arbitrary Lagrange-Euler finite-difference program, which includes chemical kinetics and heat transfer, and which is under development at this laboratory. We developed the parameter values for a reactive-flow model to describe the non-ideal detonation behavior of an HMX-based explosive from the results of grain-scale simulations. In doing so, we reduced the number of free parameters that are inferred from comparison with experiment to a single one - the characteristic defect dimension. We also performed simulations of the run to detonation in small volumes of explosive. These simulations illustrate the development of the reaction zone and the acceleration of the shock front as the flame fronts start from hot spots, grow, and interact behind the shock front. In this way, our grain-scale simulations can also connect to continuum experiments directly.

  13. New Developments in the Physical Chemistry of Shock Compression

    NASA Astrophysics Data System (ADS)

    Dlott, Dana D.

    2011-05-01

    This review discusses new developments in shock compression science with a focus on molecular media. Some basic features of shock and detonation waves, nonlinear excitations that can produce extreme states of high temperature and high pressure, are described. Methods of generating and detecting shock waves are reviewed, especially those using tabletop lasers that can be interfaced with advanced molecular diagnostics. Newer compression methods such as shockless compression and precompression shock that generate states of cold dense molecular matter are discussed. Shock compression creates a metallic form of hydrogen, melts diamond, and makes water a superionic liquid with unique catalytic properties. Our understanding of detonations at the molecular level has improved a great deal as a result of advanced nonequilibrium molecular simulations. Experimental measurements of detailed molecular behavior behind a detonation front might be available soon using femtosecond lasers to produce nanoscale simulated detonation fronts.

  14. Magnetized collisionless shock studies using high velocity plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, Thomas; Intrator, Thomas; Gao, Kevin

    2012-10-01

    Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create non-thermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and super-Alfvènic supercritical shocks with pre-existing magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Approved for Public Release: LA-UR-12-22886

  15. When shock waves collide

    DOE PAGESBeta

    Martinez, D.; Hartigan, P.; Frank, A.; Hansen, E.; Yirak, K.; Liao, A. S.; Graham, P.; Foster, J.; Wilde, B.; Blue, B.; et al

    2016-06-01

    Supersonic outflows from objects as varied as stellar jets, massive stars, and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures, and therefore a higher-excitation spectrum than does an oblique shock. In this paper, we summarize the results of a series of numerical simulations and laboratory experiments designed tomore » quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and subcritical angles, larger ones persist in these situations and can regrow if the intersection angle changes to become more favorable. Furthermore, the experimental and numerical results show that although Mach stems occur only over a limited range of intersection angles and size scales, within these ranges they are relatively robust, and hence are a viable explanation for variable bright knots observed in Hubble Space Telescope images at the intersections of some bow shocks in stellar jets.« less

  16. Anti-Shock Garment

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Ames Research Center developed a prototype pressure suit for hemophiliac children, based on research of astronauts' physiological responses in microgravity. Zoex Corporation picked up the design and patents and developed an anti-shock garment for paramedic use. Marketed by Dyna Med, the suit reverses the effect of shock on the body's blood distribution by applying counterpressure to the legs and abdomen, returning blood to vital organs and stabilizing body pressure until the patient reaches a hospital. The DMAST (Dyna Med Anti-Shock Trousers) employ lower pressure than other shock garments, and are non-inflatable.

  17. When Shock Waves Collide

    NASA Astrophysics Data System (ADS)

    Hartigan, P.; Foster, J.; Frank, A.; Hansen, E.; Yirak, K.; Liao, A. S.; Graham, P.; Wilde, B.; Blue, B.; Martinez, D.; Rosen, P.; Farley, D.; Paguio, R.

    2016-06-01

    Supersonic outflows from objects as varied as stellar jets, massive stars, and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures, and therefore a higher-excitation spectrum than does an oblique shock. In this paper, we summarize the results of a series of numerical simulations and laboratory experiments designed to quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and subcritical angles, larger ones persist in these situations and can regrow if the intersection angle changes to become more favorable. The experimental and numerical results show that although Mach stems occur only over a limited range of intersection angles and size scales, within these ranges they are relatively robust, and hence are a viable explanation for variable bright knots observed in Hubble Space Telescope images at the intersections of some bow shocks in stellar jets.

  18. Weak shock reflection

    NASA Astrophysics Data System (ADS)

    Hunter, John K.; Brio, Moysey

    2000-05-01

    We present numerical solutions of a two-dimensional inviscid Burgers equation which provides an asymptotic description of the Mach reflection of weak shocks. In our numerical solutions, the incident, reflected, and Mach shocks meet at a triple point, and there is a supersonic patch behind the triple point, as proposed by Guderley for steady weak-shock reflection. A theoretical analysis indicates that there is an expansion fan at the triple point, in addition to the three shocks. The supersonic patch is extremely small, and this work is the first time it has been resolved.

  19. Transient bow shock around a cylinder in a supersonic dusty plasma

    SciTech Connect

    Meyer, John K.; Merlino, Robert L.

    2013-07-15

    Visual observations of the formation of a bow shock in the transient supersonic flow of a dusty plasma incident on a biased cylinder are presented. The bow shock formed when the advancing front of a streaming dust cloud was reflected by the obstacle. After its formation, the density jump of the bow shock increased as it moved upstream of the obstacle. A physical picture for the formation of the electrohydrodynamic bow shock is discussed.

  20. How Is Cardiogenic Shock Treated?

    MedlinePlus

    ... page from the NHLBI on Twitter. How Is Cardiogenic Shock Treated? Cardiogenic shock is life threatening and requires emergency medical treatment. ... arrive. The first goal of emergency treatment for cardiogenic shock is to improve the flow of blood and ...

  1. [Historical vision of shock].

    PubMed

    Dosne Pasqualini, C

    1998-01-01

    The concept of shock and its close relationship with that of stress dates back to the experiments of Hans Selye initiated in 1936 at McGill University in Montreal, with whom I collaborated between 1939 and 1942. It was demonstrated that the General Adaptation Syndrome begins with an Alarm Reaction, which consists of a Stage of Shock and one of Counter-Shock, followed by a Stage of Adaptation and finally a Stage of Exhaustion. My Ph.D. thesis concluded that shock was due to an adrenal insufficiency postulating that active metabolic processes drain the body of certain essential compounds the lack of which causes shock. My interest in the role of the glucose metabolism in shock led me to work with Bernardo Houssay in 1942 at the Institute of Physiology of the University of Buenos Aires and in 1944 with C.N.H. Long at Yale University. There I developed a method for the induction of hemorrhagic shock in the guinea pig with 94% lethality; curiously, the administration of 200 mg of ascorbic acid prevented death. Upon my return to Buenos Aires, these results were confirmed and moreover, it was demonstrated that the administration of cortisone led to 40% survival of the animals while desoxycorticosterone had no effect. At the time, no explanation was available but to-day, half a century later, this Symposium should be able to explain the mechanisms leading to death by hemorrhagic shock. PMID:9816693

  2. Shock Demagnetization of Pyrrhotite

    NASA Technical Reports Server (NTRS)

    Louzada, K. L.; Stewart, S. T.; Weiss, b. P.

    2005-01-01

    Maps of the remanent magnetic field of Mars show demagnetized zones within and around giant impact basins. It is likely that vast regions of the Martian crust were demagnetized due to a shock-induced phase change or magnetic transition of magnetic minerals in the crust. This hypothesis is supported by the fact that around the Hellas and Argyre basins, the edges of the unmagnetized zones roughly correspond with peak shock pressure contour lines of a few GPa. Although pyrrhotite is not a major carrier of magnetization in the Earth s crust, it is a common phase in Martian meteorites and may be an important carrier in the Martian crust. Understanding the effects of shock waves on magnetic minerals is critical for determining the origin of the demagnetized zones in impact basins and possibly for identifying the major magnetic carrier phases. Here we present the results of the first controlled shock demagnetization measurements on pyrrhotite. Previous experiments: Shock demagnetization

  3. [The Use of Arginine Vasopressin and PhosphodiesteraseIII Inhibitor for Circulatory Shock after the Resection of a Massive Adrenal Pheochromocytoma].

    PubMed

    Nagamine, Yusuke; Nishinarita, Reiko; Mizutani, Kenji; Goto, Takahisa

    2016-06-01

    A 72-year-old man developed hypertensive crisis five month previously, and was diagnosed with massive adrenal pheochromocytoma, with a diameter of 14.5 cm. Preoperative echocardiography revealed normal cardiac function. The open abdominal surgery was performed under general anesthesia. During manipulation of the tumor he developed hypertension and tachycardia. Severe hypotension (50/25 mmHg) and mild bradycardia (70 beats x min(-1)) followed the resection of the tumor. In addition to volume replacement noradrenaline and adrenaline were administered, but the systolic blood pressure rose only to 60-70 mmHg. In order to treat vasodilatory shock, we started to administer arginine vasopressin infusion at 0.03 units x min(-1). His systolic blood pressure rose to 90 mmHg. The patient was transferred to the intensive care unit (ICU) postoperatively. The echocardiography revealed diffuse hypokinetic cardiac function. In order to treat cardiogenic shock, we started to administer olprinone (phosphodiesteraseIII inhibitor, infusion of 0.1 μg x kg(-1) x min(-1)). On postoperative day 2, circulatory shock improved and the patient was discharged from the ICU. In conclusion, circulatory shock after the resection of a massive pheochromocytoma was due to the down regulation of α and β adrenergic receptors. The non-adrenergic vasoconstrictor and inotrope were useful for this situation. PMID:27483661

  4. MEMS performance challenges: packaging and shock tests

    NASA Astrophysics Data System (ADS)

    Chang, Jiyoung; Yang, Chen; Zhang, Bin; Lin, Liwei

    2011-06-01

    This paper describes recent advances in the MEMS performance challenges with emphases on packaging and shock tests. In the packaging area, metal to metal bonding processes have been developed to overcome limitations of the glass frit bonding by means of two specific methods: (1) pre-reflow of solder for enhanced bonding adhesion, and (2) the insertion of thin metal layer between parent metal bonding materials. In the shock test area, multiscale analysis for a MEMS package system has been developed with experimental verifications to investigate dynamic responses under drop-shock tests. Structural deformation and stress distribution data are extracted and predicted for device fracture and in-operation stiction analyses for micro mechanical components in various MEMS sensors, including accelerometers and gyroscopes.

  5. Comparison of shock severity measures

    SciTech Connect

    Baca, T.J.

    1989-01-01

    In an effort to clarify the issues associated with quantifying shock severity, this paper compares the merits of two measures of shock severity. The first measure is the widely used absolute acceleration shock response spectrum (SAA). The second measure of shock severity is relatively new and is known as the shock intensity spectrum (SIS). Overall information content of SAA and SIS spectra are compared and discussed in the context of two shock excitations having known amplitude, duration, and frequency content. The first is a burst of band-limited white noise and the second is a classical haversine pulse. After describing both the SAA and SIS shock measures, numerous examples are described which emphasize the strengths and limitations of each shock characterization method. This discussion reveals how the use of different shock measures may alter an engineer's conclusions about relative shock severity between two shock environments. 8 refs., 15 figs.

  6. Termination Shock Surfing

    NASA Astrophysics Data System (ADS)

    Burrows, R. H.; Zank, G. P.; Webb, G. M.

    2009-11-01

    The recent Voyager 2 (V2) observations of the termination shock (TS) indicate that it is a plasma shock like no other in the heliosphere with dynamics and structure heavily influenced by the presence of an energized population of pickup ions (PUIs). The `unexpected' finding of a cold plasma in the heliosheath with very little heating of the solar wind suggests that the energy dissipated by the shock could be dominated by the acceleration of PUIs at the TS. We examine the 'shock surfing' mechanism at the test particle level, where multiply reflected ions (MRIs) gain energy from the motional electric field as a consequence of reflection from the cross-shockpotential, for a specific model of the TS3 (the third TS crossing measured by V2). The energization of PUI shell distributions at a stationary, perpendicular model of the TS3 indicate that shock surfing can provide substantial PUI acceleration and a dissipation mechanism at the TS. For a strong enough cross-shock potential and sufficiently narrow shock ramp MRI acceleration can account for the `missing' energy of the downstream solar wind plasma.

  7. Anthrax-associated shock.

    PubMed

    Goldman, David L; Casadevall, Arturo

    2008-01-01

    Recent events have brought attention to the potential of Bacillus anthracis as an agent of bioterrorism. The shock like state of anthrax is invariably associated with high mortality, despite anti-microbial and supportive therapy. Multi-system dysfunction is typical, including: enhanced vascular permeability, hemorrhage and inflammation. Important questions concerning the pathophysiology of anthrax-associated shock remain unanswered, including the effects of B. anthracis infection on cardiac function. This review discusses the current state of knowledge regarding the pathophysiology of anthrax-associated shock. PMID:18508494

  8. Shock effects in meteorites

    NASA Technical Reports Server (NTRS)

    Stoeffler, D.; Bischoff, A.; Buchwald, V.; Rubin, A. E.

    1988-01-01

    The impacts that can occur between objects on intersecting solar system orbits can generate shock-induced deformations and transformations, creating new mineral phases or melting old ones. These shock-metamorphic effects affect not only the petrography but the chemical and isotopic properties and the ages of primordial meteoritic materials. A fuller understanding of shock metamorphism and breccia formation in meteorites will be essential not only in the study of early accretion, differentiation, and regolith-evolution processes, but in the characterization of the primordial composition of the accreted material itself.

  9. Shocks near Jamming

    NASA Astrophysics Data System (ADS)

    Gómez, Leopoldo R.; Turner, Ari M.; van Hecke, Martin; Vitelli, Vincenzo

    2012-02-01

    Nonlinear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they jam, these fragile and disordered solids exhibit a vanishing rigidity and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are dynamically compressed and demonstrate that the elementary excitations are strongly nonlinear shocks, rather than ordinary phonons. We capture the full dependence of the shock speed on pressure and impact intensity by a surprisingly simple analytical model.

  10. Storm Sudden Commencements Without Interplanetary Shocks

    NASA Astrophysics Data System (ADS)

    Park, Wooyeon; Lee, Jeongwoo; Yi, Yu; Ssessanga, Nicholas; Oh, Suyeon

    2015-09-01

    Storm sudden commencements (SSCs) occur due to a rapid compression of the Earth's magnetic field. This is generally believed to be caused by interplanetary (IP) shocks, but with exceptions. In this paper we explore possible causes of SSCs other than IP shocks through a statistical study of geomagnetic storms using SYM-H data provided by the World Data Center for Geomagnetism ? Kyoto and by applying a superposed epoch analysis to simultaneous solar wind parameters obtained with the Advanced Composition Explorer (ACE) satellite. We select a total of 274 geomagnetic storms with minimum SYM-H of less than ?30nT during 1998-2008 and regard them as SSCs if SYM-H increases by more than 10 nT over 10 minutes. Under this criterion, we found 103 geomagnetic storms with both SSC and IP shocks and 28 storms with SSC not associated with IP shocks. Storms in the former group share the property that the strength of the interplanetary magnetic field (IMF), proton density and proton velocity increase together with SYM-H, implying the action of IP shocks. During the storms in the latter group, only the proton density rises with SYM-H. We find that the density increase is associated with either high speed streams (HSSs) or interplanetary coronal mass ejections (ICMEs), and suggest that HSSs and ICMEs may be alternative contributors to SSCs.

  11. Simulations of Relativistic Collisionless Shocks: Shock Structure and Particle Acceleration

    SciTech Connect

    Spitkovsky, Anatoly; /KIPAC, Menlo Park

    2006-04-10

    We discuss 3D simulations of relativistic collisionless shocks in electron-positron pair plasmas using the particle-in-cell (PIC) method. The shock structure is mainly controlled by the shock's magnetization (''sigma'' parameter). We demonstrate how the structure of the shock varies as a function of sigma for perpendicular shocks. At low magnetizations the shock is mediated mainly by the Weibel instability which generates transient magnetic fields that can exceed the initial field. At larger magnetizations the shock is dominated by magnetic reflections. We demonstrate where the transition occurs and argue that it is impossible to have very low magnetization collisionless shocks in nature (in more than one spatial dimension). We further discuss the acceleration properties of these shocks, and show that higher magnetization perpendicular shocks do not efficiently accelerate nonthermal particles in 3D. Among other astrophysical applications, this may pose a restriction on the structure and composition of gamma-ray bursts and pulsar wind outflows.

  12. Life shocks and homelessness.

    PubMed

    Curtis, Marah A; Corman, Hope; Noonan, Kelly; Reichman, Nancy E

    2013-12-01

    We exploited an exogenous health shock-namely, the birth of a child with a severe health condition-to investigate the effect of a life shock on homelessness in large cities in the United States as well as the interactive effects of the shock with housing market characteristics. We considered a traditional measure of homelessness, two measures of housing instability thought to be precursors to homelessness, and a combined measure that approximates the broadened conceptualization of homelessness under the 2009 Homeless Emergency Assistance and Rapid Transition to Housing Act (2010). We found that the shock substantially increases the likelihood of family homelessness, particularly in cities with high housing costs. The findings are consistent with the economic theory of homelessness, which posits that homelessness results from a conjunction of adverse circumstances in which housing markets and individual characteristics collide. PMID:23868747

  13. Toxic shock syndrome

    MedlinePlus

    ... by a toxin produced by some types of Staphylococcus bacteria. A similar problem, called toxic shock-like ... men. Risk factors include: Recent childbirth Infection with Staphylococcus aureus ( S. aureus ), commonly called a Staph infection Foreign ...

  14. Acute Biliary Septic Shock

    PubMed Central

    1990-01-01

    Forty-seven cases of biliary tract infection with septic shock are presented. The sepsis was caused by empyema of the gallbladder in 23 cases and by cholangitis in the remainder. Gallstones were most frequently the cause of the sepsis. An appropriate diagnostic description of the syndrome of biliary tract infection and septic shock should therefore include a description of the underlying biliary disease as well as the term acute biliary shock. In this series, emergency surgical management by removal of gallstones and drainage of suppuration was felt to be the most appropriate treatment. There was a high incidence of gallbladder rupture (10.6%) and intrahepatic stones (53.2%). Of the 13 patients who died, 8 might have survived if early operation had been performed after the diagnosis of acute biliary septic shock was established. PMID:2278914

  15. Testing bow shock models

    NASA Astrophysics Data System (ADS)

    Alrefay, Thamer; Meziane, Karim; Hamza, A. M.

    2016-07-01

    Space plasmas studies of bow shock dynamics, given the fundamental transport role and impact natural transition boundaries, have continued to attract much interest. With the overwhelming availability of data collected by various space science missions, several empirical models have been put forward to account for the location of the Earth's bow shock. Various solar wind and IMF measured parameters are used to constrain the proposed models published in the literature. For each of these empirical models, the bow shock nose velocity, at the standoff distance, is computed; each of these velocities is then compared with the observed shock speed as determined from a multipoint measurement provided by the Cluster quartet. The present study reveals to what extent the model parameters used are significant and determinant, and suggests that some empirical models are more accurate than others are.

  16. Hybrid simulations of the effects of interstellar pickup hydrogen on the solar wind termination shock

    NASA Technical Reports Server (NTRS)

    Liewer, P. C.; Goldstein, B. E.; Omidi, N.

    1993-01-01

    Hybrid (kinetic ions/fluid electrons) plasma simulations are used to study the effects of a population of energetic interstellar pickup hydrogen ions on the solar wind termination shock. The pickup hydrogen is treated as a second ion species in the simulations, and thus the effects of the pick-ups on the shock, as well as the effects of the shock on the pickups, are treated in a fully self-consistent manner. For quasi-perpendicular shocks with 10-20 percent pickup hydrogen the pickup ions manifest themselves in a small foot ahead of the shock ramp caused by pickup ion reflection. For oblique shocks with smaller angles between the field and the shock normal, a large fraction of the pickup ions are reflected and move back upstream where they excite large amplitude magnetosonic waves which steepen into shocklets. These backstreaming pickup ions may provide advance warning of a spacecraft encounter with the termination shock.

  17. "Smart" Electromechanical Shock Absorber

    NASA Technical Reports Server (NTRS)

    Stokes, Lebarian; Glenn, Dean C.; Carroll, Monty B.

    1989-01-01

    Shock-absorbing apparatus includes electromechanical actuator and digital feedback control circuitry rather than springs and hydraulic damping as in conventional shock absorbers. Device not subject to leakage and requires little or no maintenance. Attenuator parameters adjusted in response to sensory feedback and predictive algorithms to obtain desired damping characteristic. Device programmed to decelerate slowly approaching vehicle or other large object according to prescribed damping characteristic.

  18. Attosecond shock waves.

    PubMed

    Zhokhov, P A; Zheltikov, A M

    2013-05-01

    Shock-wave formation is a generic scenario of wave dynamics known in nonlinear acoustics, fluid dynamics, astrophysics, seismology, and detonation physics. Here, we show that, in nonlinear optics, remarkably short, attosecond shock transients can be generated through a strongly coupled spatial and temporal dynamics of ultrashort light pulses, suggesting a pulse self-compression scenario whereby multigigawatt attosecond optical waveforms can be synthesized. PMID:23683197

  19. Development of an ultra-low-shock separation nut

    NASA Technical Reports Server (NTRS)

    Woebkenberg, W.; Matteo, D. N.; Williams, V. D.

    1982-01-01

    The technical problems encountered in the development of an advanced separation nut design are described. The nut is capable of sustaining a large preload and releasing that load with a low level of induced pyrotechnic shock, while demonstrating a tolerance for extremely high shock imposed by other pyrotechnic devices. The analysis of the separation nut was performed to acquire additional understanding of the phenomena affecting operation of the nut and to provide quantitative evaluation of design modification for aerospace applications.

  20. Shock/shock interference on a transpiration cooled hemispherical model

    NASA Technical Reports Server (NTRS)

    Nowak, Robert J.; Wieting, Allan R.; Holden, Michael S.

    1990-01-01

    Experimental results are presented which show the effectiveness of transpiration cooling in reducing the peak heat flux caused by an impinging shock on a bow shock of a hemispherical model. The 12-inch diameter hemispherical transpiration model with helium coolant was tested in the Calspan 48-inch Hypersonic Shock Tunnel at nominal Mach 12.1 and freestream unit Reynolds number of 0.33 x 10 to the 6th/ft. An incident shock wave, generated by a blunt flat-plate shock generator inclined at 10 deg to the freestream, intersected the bow shock of the model to produce shock/shock interference. The stagnation heat flux without coolant or shock/shock interference was about 1.6 times a smooth surface laminar prediction due to effective roughness of the coolant ejection slots. A coolant mass flux 31 percent of the freestream mass flux reduced the stagnation heat flux to zero without shock/shock interference. However, for the same coolant mass flux and with shock/shock interference the peak heat flux was only reduced 8.3 percent, even though the total integrated heat load was reduced.

  1. Rescue treatment with terlipressin in children with refractory septic shock: a clinical study

    PubMed Central

    Rodríguez-Núñez, Antonio; López-Herce, Jesús; Gil-Antón, Javier; Hernández, Arturo; Rey, Corsino

    2006-01-01

    children with refractory vasodilatory septic shock. The addition of TP to high doses of catecholamines, however, can induce excessive vasoconstriction. Additional studies are needed to define the safety profile and the clinical effectiveness of TP in children with septic shock. PMID:16469127

  2. Shock Tunnel Studies of Scramjet Phenomena 1994

    NASA Technical Reports Server (NTRS)

    Morgan, R. G.; Paull, A.; Stalker, R. J.

    1997-01-01

    Reports by the research staff and graduate students of the Mechanical Engineering Department at the University of Queensland are collected and presented. These reports cover various studies related to the advancement of scramjet technology and the operation of advanced hypervelocity shock-expansion tubes. The report topics include the experimental studies of mixing and combustion in a scramjet flow path, the measurement of integrated thrust and skin friction, and the development of a free-piston-driven expansion tunnel capable of delivering a test gas at superorbital velocities.

  3. Shock structures of astrospheres

    NASA Astrophysics Data System (ADS)

    Scherer, K.; Fichtner, H.; Kleimann, J.; Wiengarten, T.; Bomans, D. J.; Weis, K.

    2016-02-01

    Context. The interaction between a supersonic stellar wind and a (super-)sonic interstellar wind has recently been viewed with new interest. We here first give an overview of the modeling, which includes the heliosphere as an example of a special astrosphere. Then we concentrate on the shock structures of fluid models, especially of hydrodynamic (HD) models. More involved models taking into account radiation transfer and magnetic fields are briefly sketched. Even the relatively simple HD models show a rich shock structure, which might be observable in some objects. Aims: We employ a single-fluid model to study these complex shock structures, and compare the results obtained including heating and cooling with results obtained without these effects. Furthermore, we show that in the hypersonic case valuable information of the shock structure can be obtained from the Rankine-Hugoniot equations. Methods: We solved the Euler equations for the single-fluid case and also for a case including cooling and heating. We also discuss the analytical Rankine-Hugoniot relations and their relevance to observations. Results: We show that the only obtainable length scale is the termination shock distance. Moreover, the so-called thin shell approximation is usually not valid. We present the shock structure in the model that includes heating and cooling, which differs remarkably from that of a single-fluid scenario in the region of the shocked interstellar medium. We find that the heating and cooling is mainly important in this region and is negligible in the regions dominated by the stellar wind beyond an inner boundary.

  4. Seismic Precursors to Space Shuttle Shock Fronts

    NASA Astrophysics Data System (ADS)

    Sorrells, G.; Bonner, J.; Herrin, E. T.

    - Seismic precursors to space shuttle re-entry shock fronts are detected at TXAR in Southwest Texas when the ground track of the orbiter vehicle passes within 150-200km of the observatory. These precursors have been termed ``shuttle-quakes'' because their seismograms superficially mimic the seismograms of small earthquakes from shallow sources. Analysis of the ``shuttle-quake'' seismograms, however, reveals one important difference. Unlike ordinary earthquakes, the propagation azimuths and horizontal phase velocities of the individual phases of the ``shuttle-quakes'' are functionally related. From a theoretical model developed to account for the origin of these precursors it is found that the seismic phases of ``shuttle-quakes'' are ``bow'' waves. A ``bow'' wave originates at the advancing tip of the shock front trace (i.e., intersection of the re-entry shock front with the surface of the earth) when the ground speed of the orbiter vehicle exceeds the horizontal phase velocity of a particular seismic phase. ``Bow'' waves are shown to differ in two important respects from the ordinary seismic phases. They vanish ahead of the advancing tip of the shock front trace and their propagation azimuths and horizontal phase velocities are functionally related. The ground speed of the orbiter vehicle exceeds the horizontal phase velocities of crustal seismic phase over much of the re-entry flight profile. As a result, P,S, and Rg``bow'' waves will be seen as precursors to the re-entry shock front at stations located within a few hundred km of its ground track.

  5. Heliospheric shocks and catastrophe theory

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.

    1990-01-01

    Various configurations of forward and reverse shocks that occur in the outer heliosphere can be classified using catastrophe theory. The existence of a forward shock is associated with a local maximum of a polynomial, and the existence of a reverse shock is associated with a local minimum of a polynomial. A configuration with N forward shocks and N reverse shocks corresponds to a polynomial with N maxima and N minima. The formation of forward and reverse shocks corresponds to the creation of maxima and minima of a polynomial, which is described by the separatrices of the catastrophes. The coalescence of two forward (reverse) shocks corresponds to the situation when two maxima (minima) of a polynomial have equal values, and the interaction of a forward shock with a reverse shock corresponds to a polynomial with a local maximum equal to a local minimum; these situations are described by the Maxwell sets of the appropriate catastrophes.

  6. Shocks in fragile matter

    NASA Astrophysics Data System (ADS)

    Vitelli, Vincenzo

    2012-02-01

    Non-linear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they unjam, these fragile and disordered solids exhibit vanishing elastic moduli and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are continuously compressed, and demonstrate that the resulting excitations are strongly nonlinear shocks, rather than linear waves. We capture the full dependence of the shock speed on pressure and compression speed by a surprisingly simple analytical model. We also treat shear shocks within a simplified viscoelastic model of nearly-isostatic random networks comprised of harmonic springs. In this case, anharmonicity does not originate locally from nonlinear interactions between particles, as in granular media; instead, it emerges from the global architecture of the network. As a result, the diverging width of the shear shocks bears a nonlinear signature of the diverging isostatic length associated with the loss of rigidity in these floppy networks.

  7. TIMING OF SHOCK WAVES

    DOEpatents

    Tuck, J.L.

    1955-03-01

    This patent relates to means for ascertaining the instant of arrival of a shock wave in an exploslve charge and apparatus utilizing this means to coordinate the timing of two operations involving a short lnterval of time. A pair of spaced electrodes are inserted along the line of an explosive train with a voltage applied there-across which is insufficient to cause discharge. When it is desired to initiate operation of a device at the time the explosive shock wave reaches a particular point on the explosive line, the device having an inherent time delay, the electrodes are located ahead of the point such that the ionization of the area between the electrodes caused by the traveling explosive shock wave sends a signal to initiate operation of the device to cause it to operate at the proper time. The operated device may be photographic equipment consisting of an x-ray illuminating tube.

  8. Life Shocks and Homelessness

    PubMed Central

    Corman, Hope; Noonan, Kelly; Reichman, Nancy E.

    2014-01-01

    We exploited an exogenous health shock—namely, the birth of a child with a severe health condition—to investigate the effect of a life shock on homelessness in large cities in the United States as well as the interactive effects of the shock with housing market characteristics. We considered a traditional measure of homelessness, two measures of housing instability thought to be precursors to homelessness, and a combined measure that approximates the broadened conceptualization of homelessness under the 2009 Homeless Emergency Assistance and Rapid Transition to Housing Act (2010). We found that the shock substantially increases the likelihood of family homelessness, particularly in cities with high housing costs. The findings are consistent with the economic theory of homelessness, which posits that homelessness results from a conjunction of adverse circumstances in which housing markets and individual characteristics collide. PMID:23868747

  9. Dusty Termination Shocks

    SciTech Connect

    Ip, W.H.

    2004-09-15

    In astrophysical settings, termination shocks where strong stellar wind outflows interact with the surrounding environments tend to take place in dusty regions. Just to name a few, star formation regions, planetary nebulae, supernova remnants and active galactic nuclei are all good examples. Dynamics and evolution of the associated dust clouds could have important influences on the acceleration and composition of energetic particles resulting from the diffusive shock acceleration at the termination shocks. In this note we provide a brief review of previous work predating the recent detection of ACR Mg, Na, Si and S ions which might have originated from the Kuiper belt dust. Their compositional abundance might be diagnostic of the collisional history of the Kupier belt objects.

  10. Principles and application of shock-tubes and shock tunnels

    NASA Technical Reports Server (NTRS)

    Ried, R. C.; Clauss, H. G., Jr.

    1963-01-01

    The principles, theoretical flow equations, calculation techniques, limitations and practical performance characteristics of basic and high performance shock tubes and shock tunnels are presented. Selected operating curves are included.

  11. [Traumatic neurogenic shock].

    PubMed

    Maurin, O; de Régloix, S; Caballé, D; Arvis, A-M; Perrochon, J-C; Tourtier, J-P

    2013-05-01

    Traumatic neurogenic shock is a rare but serious complication of spinal cord injury. It associates bradycardia and hypotension caused by a medullary trauma. It is life-threatening for the patient and it aggravates the neurological deficit. Strict immobilization and a quick assessment of the gravity of cord injury are necessary as soon as prehospital care has begun. Initial treatment requires vasopressors associated with fluid resuscitation. Steroids are not recommended. Early decompression is recommended for incomplete deficit seen in the first 6 hours. We relate the case of secondary spinal shock to a luxation C6/C7 treated in prehospital care. PMID:23566590

  12. Methods of Monitoring Shock

    PubMed Central

    Bajwa, Ednan K.; Malhotra, Atul; Thompson, B. Taylor

    2012-01-01

    Intensive monitoring is a crucial component of the management of shock. However, there is little consensus about optimal strategies for monitoring. Although the pulmonary artery catheter has been widely used, conflicting data exist about the utility of this device. A variety of other techniques have been developed in hopes of providing clinically useful information about myocardial function, intravascular volume, and indices of organ function. In addition, there is evolving evidence that targeting and monitoring certain physiological goals may be most important early in the course of shock. In this chapter, we examine many of the available monitoring techniques and the evidence supporting their use. PMID:16088506

  13. Shock destruction armor system

    DOEpatents

    Froeschner, Kenneth E.

    1993-01-01

    A shock destruction armor system is constructed and arranged to destroy the force of impact of a projectile by shock hydrodynamics. The armor system is designed to comprise a plurality of superimposed armor plates each preferably having a thickness less than five times the projectile's diameter and are preferably separated one-from-another by a distance at least equal to one-half of the projectile's diameter. The armor plates are effective to hydrodynamically and sequentially destroy the projectile. The armor system is particularly adapted for use on various military vehicles, such as tanks, aircraft and ships.

  14. Shock compression of [001] single crystal silicon

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Hahn, E. N.; Kad, B.; Remington, B. A.; Bringa, E. M.; Meyers, M. A.

    2016-05-01

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.

  15. Shock compression of [001] single crystal silicon

    DOE PAGESBeta

    Zhao, S.; Remington, B.; Hahn, E. N.; Kad, B.; Bringa, E. M.; Meyers, M. A.

    2016-03-14

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent withmore » dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Furthermore, application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.« less

  16. Characteristics of Weak Interplanetary Shocks and Shock-like Events

    NASA Astrophysics Data System (ADS)

    Balogh, A.; Gloag, J. M.

    The variation of magnetic and plasma parameters across the discontinuity of a colli- sionless shock wave are clearly understood and presented in MHD theory. The anal- ysis of 116 shock waves appearing on the Ulysses shock list in the period mid 1996 to the end of 1999 show that in the cases of the stronger shock waves, measured by the ratio of downstream to upstream magnetic field magnitudes, this MHD descrip- tion is adequate. However in the case of many of the weaker shocks there are events which are not clearly characterised in MHD terms and in these cases plasma param- eters are particularly difficult to interpret. To explore the issues associated with these very weak shocks further, a set of shock-like events is considered which have shock characteristics in the high frequency wave data measured by the plasma wave inves- tigation(URAP) but are not considered to be clearly shock waves purely considering magnetic and plasma data. These shock-like events are thought to extend the spectrum of interplanetary shocks at the very weakest end and possibly beyond what should be considered a collisionless shock wave.

  17. Impact-shocked zircons: Discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

    NASA Technical Reports Server (NTRS)

    Bohor, B. F.; Betterton, W. J.; Krogh, T. E.

    1993-01-01

    Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows scanning electron microscope (SEM) visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the U-Pb isotopic system.

  18. Impact-shocked zircons: discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

    USGS Publications Warehouse

    Bohor, B.F.; Betterton, W.J.; Krogh, T.E.

    1993-01-01

    Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows SEM visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the UPb isotopic system. ?? 1993.

  19. Shock waves data for minerals

    NASA Technical Reports Server (NTRS)

    Ahrens, Thomas J.; Johnson, Mary L.

    1994-01-01

    Shock compression of the materials of planetary interiors yields data which upon comparison with density-pressure and density-sound velocity profiles constrain internal composition and temperature. Other important applications of shock wave data and related properties are found in the impact mechanics of terrestrial planets and solid satellites. Shock wave equation of state, shock-induced dynamic yielding and phase transitions, and shock temperature are discussed. In regions where a substantial phase change in the material does not occur, the relationship between the particle velocity, U(sub p), and the shock velocity, U(sub s), is given by U(sub s) = C(sub 0) + S U(sub p), where C(sub 0) is the shock velocity at infinitesimally small particle velocity, or the ambient pressure bulk sound velocity. Numerical values for the shock wave equation of state for minerals and related materials of the solar system are provided.

  20. Developments in strong shock wave position tracking

    NASA Astrophysics Data System (ADS)

    Rae, Philip; Glover, Brain; Perry, Lee; WX-6; WX-7 Team

    2011-06-01

    This poster will highlight several modified techniques to allow the position vs. time to be tracked in strong shock situations (such as detonation). Each is a modification or improvement of existing ideas either making use of advances in specialist materials availability or recent advances in electronics.) Shorting embedded mini-coaxial cable with a standing microwave pattern. This technique is a modified version of an old LANL method of shock position tracking making use of a traveling short imposed in an embedded coaxial cable. A high frequency standing wave (3-8GHz) is present in the cable and the moving short position can be tracked by monitoring the output voltage envelope as a function of time. A diode detector is used to allow the envelope voltage to be monitored on a regular low frequency digitizer significantly reducing the cost. The small and cheap high frequency voltage generators now available allow much greater spatial resolution than possible previously. 2) Very thin shorting resistance track gauges. Parallel tracks of constantan resistance material are etched on a thin dielectric substrate. The gauges are less than 0.2 mm thick. The ionized gas present in a detonation front sweeps up the tracks lowering the measured resistance. A potential divider circuit allows the shock position vs. time to be monitored on a regular digitizer after easy calibration. The novel feature is the thin section of the gauge producing minimal perturbation in the detonation front.

  1. Maskelynite: Formation by explosive shock

    USGS Publications Warehouse

    Milton, D.J.; De Carli, P. S.

    1963-01-01

    When high pressure (250 to 300 kilobars) was applied suddenly (shock-loading) to gabbro, the plagioclase was transformed to a noncrystalline phase (maskelynite) by a solid-state reaction at a low temperature, while the proxene remained crystalline. The shock-loaded gabbro resembles meteorites of the shergottite class; this suggests that the latter formed as a result of shock. The shock-loading of gabbro at 600 to 800 kilobars raised the temperature above the melting range of the plagioclase.

  2. Shock compression of polyvinyl chloride

    NASA Astrophysics Data System (ADS)

    Neogi, Anupam; Mitra, Nilanjan

    2016-04-01

    This study presents shock compression simulation of atactic polyvinyl chloride (PVC) using ab-initio and classical molecular dynamics. The manuscript also identifies the limits of applicability of classical molecular dynamics based shock compression simulation for PVC. The mechanism of bond dissociation under shock loading and its progression is demonstrated in this manuscript using the density functional theory based molecular dynamics simulations. The rate of dissociation of different bonds at different shock velocities is also presented in this manuscript.

  3. A Shocking New Pump

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Hydro Dynamics, Inc. received a technical helping hand from NASA that made their Hydrosonic Pump (HPump) a reality. Marshall engineers resolved a bearing problem in the rotor of the pump and recommended new bearings, housings and mounting hardware as a solution. The resulting HPump is able to heat liquids with greater energy efficiency using shock waves to generate heat.

  4. Teleconnected food supply shocks

    NASA Astrophysics Data System (ADS)

    Bren d'Amour, Christopher; Wenz, Leonie; Kalkuhl, Matthias; Steckel, Jan Christoph; Creutzig, Felix

    2016-03-01

    The 2008-2010 food crisis might have been a harbinger of fundamental climate-induced food crises with geopolitical implications. Heat-wave-induced yield losses in Russia and resulting export restrictions led to increases in market prices for wheat across the Middle East, likely contributing to the Arab Spring. With ongoing climate change, temperatures and temperature variability will rise, leading to higher uncertainty in yields for major nutritional crops. Here we investigate which countries are most vulnerable to teleconnected supply-shocks, i.e. where diets strongly rely on the import of wheat, maize, or rice, and where a large share of the population is living in poverty. We find that the Middle East is most sensitive to teleconnected supply shocks in wheat, Central America to supply shocks in maize, and Western Africa to supply shocks in rice. Weighing with poverty levels, Sub-Saharan Africa is most affected. Altogether, a simultaneous 10% reduction in exports of wheat, rice, and maize would reduce caloric intake of 55 million people living in poverty by about 5%. Export bans in major producing regions would put up to 200 million people below the poverty line at risk, 90% of which live in Sub-Saharan Africa. Our results suggest that a region-specific combination of national increases in agricultural productivity and diversification of trade partners and diets can effectively decrease future food security risks.

  5. Teleconnected food supply shocks

    NASA Astrophysics Data System (ADS)

    Bren d’Amour, Christopher; Wenz, Leonie; Kalkuhl, Matthias; Steckel, Jan Christoph; Creutzig, Felix

    2016-03-01

    The 2008–2010 food crisis might have been a harbinger of fundamental climate-induced food crises with geopolitical implications. Heat-wave-induced yield losses in Russia and resulting export restrictions led to increases in market prices for wheat across the Middle East, likely contributing to the Arab Spring. With ongoing climate change, temperatures and temperature variability will rise, leading to higher uncertainty in yields for major nutritional crops. Here we investigate which countries are most vulnerable to teleconnected supply-shocks, i.e. where diets strongly rely on the import of wheat, maize, or rice, and where a large share of the population is living in poverty. We find that the Middle East is most sensitive to teleconnected supply shocks in wheat, Central America to supply shocks in maize, and Western Africa to supply shocks in rice. Weighing with poverty levels, Sub-Saharan Africa is most affected. Altogether, a simultaneous 10% reduction in exports of wheat, rice, and maize would reduce caloric intake of 55 million people living in poverty by about 5%. Export bans in major producing regions would put up to 200 million people below the poverty line at risk, 90% of which live in Sub-Saharan Africa. Our results suggest that a region-specific combination of national increases in agricultural productivity and diversification of trade partners and diets can effectively decrease future food security risks.

  6. Bow Shocks at Comets

    NASA Astrophysics Data System (ADS)

    Coates, Andrew J.

    2009-11-01

    Comets provide a wonderful laboratory to study the interaction of a fast flowing plasma, the solar wind, with neutral gas from the comet. On ionization, the more massive newly-born cometary ions are assimilated into the solar wind flow, eventually causing its deceleration via this `mass loading'. One of the effects of this is the cometary bow shock. The exploration of comet Halley by an armada of spacecraft in 1986, as well as the in-situ exploration of comets Giacobini-Zinner (1985), Grigg-Skjellerup (1992) and Borrelly (2001), has revealed important results on the behavior of these weak shocks and showed that mass loading plays a key role. In 2014, the Rosetta mission will provide the first observations of the formation of the cometary bow shock as a comet, Churyumov-Gerasimenko, nears the Sun. Rosetta will also provide the first measurements of the collision-dominated near-nucleus region. Here, we briefly review what we know about cometary bow shocks, and we examine the prospects for Rosetta.

  7. Interaction between perpendicular magnetohydrodynamic shocks

    NASA Technical Reports Server (NTRS)

    Hu, Y. Q.; Habbal, S. R.

    1993-01-01

    A general analysis is made of the collision and merging of perpendicular shocks as well as the interaction between a shock and a tangential discontinuity. It is found that two head-on shocks diminish both in strength after collisions and a tangential discontinuity forms between them. The property of the discontinuity depends on the relative strength of the two shocks. No discontinuity occurs if the shocks are equal in strength. The emerging of two shocks propagating in the same direction results in a strong shock followed by a tangential discontinuity and a reverse wave. The reverse wave is a rarefaction wave if one or both of the shocks are strong. If the shocks are both weak, a critical adiabatic index (CAI) exists. The reverse wave is a rarefaction wave if the wavelength is less than the CAI and a shock exists if the wavelength is greater than the CAI. As a wake shock enters from a medium of higher wave impedance into that of lower wave impedance, the reflected wave is a rarefaction wave and the total pressure ratio decreases and the velocity jump increases after the shock passes through the border.

  8. STEREO interplanetary shocks and foreshocks

    SciTech Connect

    Blanco-Cano, X.; Kajdic, P.; Aguilar-Rodriguez, E.; Russell, C. T.; Jian, L. K.; Luhmann, J. G.

    2013-06-13

    We use STEREO data to study shocks driven by stream interactions and the waves associated with them. During the years of the extended solar minimum 2007-2010, stream interaction shocks have Mach numbers between 1.1-3.8 and {theta}{sub Bn}{approx}20-86 Degree-Sign . We find a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. We find that many quasiperpendicular shocks can be accompanied by ULF wave and ion foreshocks, which is in contrast to Earth's bow shock. Fluctuations downstream of quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr {<=}0.05 AU. This is smaller than foreshock extensions for ICME driven shocks. The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at {approx}1 AU and have been producing suprathermal particles for a shorter time.

  9. Compression Shocks of Detached Flow

    NASA Technical Reports Server (NTRS)

    Eggink

    1947-01-01

    It is known that compression shocks which lead from supersonic to subsonic velocity cause the flow to separate on impact on a rigid wall. Such shocks appear at bodies with circular symmetry or wing profiles on locally exceeding sonic velocity, and in Laval nozzles with too high a back pressure. The form of the compression shocks observed therein is investigated.

  10. Entropy considerations applied to shock unsteadiness in hypersonic inlets

    NASA Astrophysics Data System (ADS)

    Bussey, Gillian Mary Harding

    The stability of curved or rectangular shocks in hypersonic inlets in response to flow perturbations can be determined analytically from the principle of minimum entropy. Unsteady shock wave motion can have a significant effect on the flow in a hypersonic inlet or combustor. According to the principle of minimum entropy, a stable thermodynamic state is one with the lowest entropy gain. A model based on piston theory and its limits has been developed for applying the principle of minimum entropy to quasi-steady flow. Relations are derived for analyzing the time-averaged entropy gain flux across a shock for quasi-steady perturbations in atmospheric conditions and angle as a perturbation in entropy gain flux from the steady state. Initial results from sweeping a wedge at Mach 10 through several degrees in AEDC's Tunnel 9 indicates the bow shock becomes unsteady near the predicted normal Mach number. Several curved shocks of varying curvature are compared to a straight shock with the same mean normal Mach number, pressure ratio, or temperature ratio. The present work provides analysis and guidelines for designing an inlet robust to off- design flight or perturbations in flow conditions an inlet is likely to face. It also suggests that inlets with curved shocks are less robust to off-design flight than those with straight shocks such as rectangular inlets. Relations for evaluating entropy perturbations for highly unsteady flow across a shock and limits on their use were also developed. The normal Mach number at which a shock could be stable to high frequency upstream perturbations increases as the speed of the shock motion increases and slightly decreases as the perturbation size increases. The present work advances the principle of minimum entropy theory by providing additional validity for using the theory for time-varying flows and applying it to shocks, specifically those in inlets. While this analytic tool is applied in the present work for evaluating the stability

  11. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  12. Weak-shock reflection factors

    SciTech Connect

    Reichenbach, H.; Kuhl, A.L.

    1993-09-07

    The purpose of this paper is to compare reflection factors for weak shocks from various surfaces, and to focus attention on some unsolved questions. Three different cases are considered: square-wave planar shock reflection from wedges; square-wave planar shock reflection from cylinders; and spherical blast wave reflection from a planar surface. We restrict ourselves to weak shocks. Shocks with a Mach number of M{sub O} < 1.56 in air or with an overpressure of {Delta}{sub PI} < 25 psi (1.66 bar) under normal ambient conditions are called weak.

  13. Multipoint study of interplanetary shocks

    NASA Astrophysics Data System (ADS)

    Blanco-Cano, Xochitl; Kajdic, Primoz; Russell, Christopher T.; Aguilar-Rodriguez, Ernesto; Jian, Lan K.; Luhmann, Janet G.

    2016-04-01

    Interplanetary (IP) shocks are driven in the heliosphere by Interplanetary Coronal Mass Ejections (ICMEs) and Stream Interaction Regions (SIRs). These shocks perturb the solar wind plasma, and play an active role in the acceleration of ions to suprathermal energies. Shock fronts evolve as they move from the Sun. Their surfaces can be far from uniform and be modulated by changes in the ambient solar wind (magnetic field orientation, flow velocity), shocks rippling, and perturbations upstream and downstream from the shocks, i.e., electromagnetic waves. In this work we use multipoint observations from STEREO, WIND, and MESSENGER missions to study shock characteristics at different helio-longitudes and determine the properties of the waves near them. We also determine shock longitudinal extensions and foreshock sizes. The variations of geometry along the shock surface can result in different extensions of the wave and ion foreshocks ahead of the shocks, and in different wave modes upstream and downtream of the shocks. We find that the ion foreshock can extend up to 0.2 AU ahead of the shock, and that the upstream region with modified solar wind/waves can be very asymmetric.

  14. Shock metamorphism of deformed quartz

    NASA Technical Reports Server (NTRS)

    Gratz, Andrew J.; Christie, John; Tyburczy, James; Ahrens, Thomas; Pongratz, Peter

    1988-01-01

    The effect produced by shock loading (to peak pressures of 12 and 24) on deformed synthetic quartz containing a dislocation and abundant bubbles and small inclusions was investigated, and the relationships between preexisting dislocation density shock lamellae in the target material were examined. The resultant material was found to be inhomogeneously deformed and extremely fractured. Results of TEM examinations indicate that no change in dislocation density was caused by shock loading except in regions containing shock lamellae, where the dislocation density was lowered. The shock-induced defects tend to nucleate on and be controlled by preexisting stress concentrators; shock lamellae, glassy veins, and most curviplanar defects form in tension, presumably during release. An extremely mobile silica fluid is formed and injected into fractures during release, which forcibly removes crystalline fragments from vein walls. It is concluded that shock deformation in quartz is dominated by fracture and melting.

  15. Role of shock-timing in two-shock platform

    NASA Astrophysics Data System (ADS)

    Krasheninnikova, Natalia; Bradley, Paul; Olson, Rick; Kyrala, George; Peterson, Bob; Devolder, Barbara; Shah, Rahul

    2015-11-01

    In present work we discuss the role of shock-timing and location of shock coalescence in newly developed two-shock platform on NIF. It is generally believed that single-shell capsules perform better when the shocks coalesce in the gas due to lower shell entropy, larger convergence ratio, better hot-spot assembly, and mix. Using HYDRA and RAGE with BHR we investigated this hypothesis for the case of separated reactants capsule and found when shocks coalesced in the gas yield improved by ~ 50% while acceptance energy only increased by ~ 3%. This suggests that improving shock timing can increase the neutron yield without a significant increase in the drive. The picture of how the mix changes with variation in shock timing is not as crisp as the overall performance. In particular, according RAGE with BHR, the mix mass can be higher or lower depending on the strength of the first shock, even when the location of coalescence is the same. However, DT yield, which is a measure of mix, noticeably increases when the shock coalesce in the gas due to prevalence of higher temperatures in the mixed region. So perhaps the mix mass is more sensitive to the strength of the shocks rather than the location of their coalescence.

  16. SUPERDIFFUSIVE SHOCK ACCELERATION

    SciTech Connect

    Perri, S.; Zimbardo, G.

    2012-05-10

    The theory of diffusive shock acceleration is extended to the case of superdiffusive transport, i.e., when the mean square deviation grows proportionally to t{sup {alpha}}, with {alpha} > 1. Superdiffusion can be described by a statistical process called Levy random walk, in which the propagator is not a Gaussian but it exhibits power-law tails. By using the propagator appropriate for Levy random walk, it is found that the indices of energy spectra of particles are harder than those obtained where a normal diffusion is envisaged, with the spectral index decreasing with the increase of {alpha}. A new scaling for the acceleration time is also found, allowing substantially shorter times than in the case of normal diffusion. Within this framework we can explain a number of observations of flat spectra in various astrophysical and heliospheric contexts, for instance, for the Crab Nebula and the termination shock of the solar wind.

  17. Landing-shock Recorder

    NASA Technical Reports Server (NTRS)

    Brevoort, M J

    1934-01-01

    A description of a special type of seismograph, called a "landing-shock recorder," to be used for measuring the acceleration during impacts such as are experienced in airplane landings, is given . The theory, together with the assumptions made, is discussed in its relation to calculating the acceleration experienced in impact. Calculations are given from records obtained for two impacts of known acceleration. In one case the impact was very severe and in the other it was only moderately severe.

  18. Selfsimilar time dependent shock structures

    NASA Technical Reports Server (NTRS)

    Beck, R.; Drury, L. O.

    1985-01-01

    Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.

  19. Selfsimilar time dependent shock structures

    NASA Astrophysics Data System (ADS)

    Beck, R.; Drury, L. O.

    1985-08-01

    Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.

  20. Shock-wave surfing

    SciTech Connect

    Laurence, Stuart J; Deiterding, Ralf

    2011-01-01

    A phenomenon referred to as shock-wave surfing , in which a body moves in such a way as to follow the shock wave generated by another upstream body, is investigated numerically and theoretically. This process can lead to the downstream body accumulating a significantly higher lateral velocity than would otherwise be possible, and thus is of importance in situations such as meteoroid fragmentation, in which the fragment separation behaviour following disruption is determined to a large extent by aerodynamic effects. The surfing effect is first investigated in the context of interactions between a sphere and a planar oblique shock. Numerical simulations are performed and a simple theoretical model is developed to determine the forces acting on the sphere. A phase-plane description is employed to elucidate features of the system dynamics. The theoretical model is then generalised to the more complex situation of aerodynamic interactions between two spheres, and, through comparisons with further computations, is shown to adequately predict, in particular, the final separation velocity of the surfing sphere in initially touching configurations. Both numerical simulations and theory indicate a strong influence of the body radius ratio on the separation process and predict a critical radius ratio for initially touching fragments that delineates entrainment of the smaller fragment within the larger fragment s shock from expulsion; this critical ratio also results in the most extended surfing. Further, these results show that an earlier prediction for the separation velocity to scale with the square root of the radius ratio does not accurately describe the separation behaviour. The theoretical model is then employed to investigate initial configurations with varying relative sphere positions and initial velocities. A phase-space description is also shown to be useful in elucidating the dynamics of the sphere-sphere system. With regard to meteoroid fragmentation, it is shown

  1. What causes oil price shocks

    SciTech Connect

    Bohi, D.R.

    1983-01-01

    It is common, though debatable, to model the world oil market as some form of a producer cartel that administers oil prices. In this context, the central question is what motivates the cartel to change prices and output. The answer is only partially given by presuming that producers seek to optimize the stream of earnings over time. Aside from complexities introduced by differences in discount rates and objective functions across producers, there is still the question of determining what the market will bear. A simple and popular explanation is that the cartel has been guided by changes in prices in spot markets. In this report, the author casts doubt on the importance of spot market prices in determining OPEC selling prices, and indeed on the proposition that OPEC price increases are administered rather than market induced. These observations are drawn from an examination of inventory and price behavior during the after the price shock of 1979. Although an alternative explanation of the 1979 experience is advanced, the primary message of this paper is that caution is advisable in accepting prevailing interpretations of how the market works. The ready corollary of this conclusion is that policies for mitigating harm during a disruption should be robust across a range of possible formulation processes. 14 refs., 6 figs., 1 tab.

  2. Shock metamorphism of carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Scott, Edward R. D.; Keil, Klaus; Stoeffler, Dieter

    1992-01-01

    Shock effects were studied in 69 carbonaceous chondrites, including CM2, CO3, CV3, ungrouped C2-C4, and CK4-6 chondrites, using optical microscopy of thin sections. It is shown that the classification scheme of Stoeffler et al. (1991) for the progressive stages of shock metamorphism in ordinary chondrites is also applicable to carbonaceous chondrites. On the basis of shock effects in olivine, the 69 carbonaceous chondrites could be assigned to four shock stage, S1 to S4. The CM2 and CO3 groups were found to be the least shocked chondrite groups, whereas the CK4-6 and CV3 were the most strongly shocked groups.

  3. Flexible Multi-Shock Shield

    NASA Technical Reports Server (NTRS)

    Christiansen, Eric L. (Inventor); Crews, Jeanne L. (Inventor)

    2005-01-01

    Flexible multi-shock shield system and method are disclosed for defending against hypervelocity particles. The flexible multi-shock shield system and method may include a number of flexible bumpers or shield layers spaced apart by one or more resilient support layers, all of which may be encapsulated in a protective cover. Fasteners associated with the protective cover allow the flexible multi-shock shield to be secured to the surface of a structure to be protected.

  4. Recent developments in shock tube research; Proceedings of the Ninth International Symposium, Stanford University, Stanford, Calif., July 16-19, 1973

    NASA Technical Reports Server (NTRS)

    Bershader, D. (Editor); Griffith, W.

    1973-01-01

    Recent advances in shock tube research are described in papers dealing with the design and performance features of new devices as well as applications in aerodynamic, chemical, and physics experiments. Topics considered include a cryogenic shock tube for studying liquid helium fluid mechanics, studies of shock focusing and nonlinear resonance in shock tubes, applications in gas laser studies, very-low and very-high temperature chemical kinetic measurements, shock tube studies of ionization and recombination phenomena, applications in bioacoustic research, shock-tube simulation studies of sonic booms, and plasma research. Individual items are announced in this issue.

  5. ASSOCIATION OF SUPRATHERMAL PARTICLES WITH COHERENT STRUCTURES AND SHOCKS

    SciTech Connect

    Tessein, J. A.; Matthaeus, W. H.; Wan, M.; Osman, K. T.; Ruffolo, D.; Giacalone, J.

    2013-10-10

    Various mechanisms have been proposed to explain observed suprathermal particle populations in the solar wind, including direct acceleration at flares, stochastic acceleration, shock acceleration, and acceleration by random compression or reconnection sites. Using magnetic field and suprathermal particle data from the Advanced Composition Explorer (ACE), we identify coherent structures and interplanetary shocks, and analyze the temporal association of energetic particle fluxes with these coherent structures. Coherent structures having a range of intensities are identified using the magnetic Partial Variance of Increments statistic, essentially a normalized vector increment. A stronger association of energetic particle flux in the 0.047-4.75 MeV range is found with intense magnetic discontinuities than is found with shocks. Nevertheless, the average profile of suprathermals near shocks is quite consistent with standard models of diffusive shock acceleration, while a significant amount of the energetic particles measured and strong discontinuities are found by ACE within six hours of a shock. This evidence supports the view that multiple mechanisms contribute to the acceleration and transport of interplanetary suprathermal particles.

  6. Magnetized Collisionless Shock Studies Using High Velocity Plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, Thomas; Intrator, T.

    2013-04-01

    Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create non-thermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and super-Alfvénic supercritical shocks with pre-existing magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Supported by DOE Office of Fusion Energy Sciences and National Nuclear Security Administration under LANS contract DE-AC52-06NA25369 Approved for Public Release: LA-UR-12-22886

  7. Magnetized collisionless shock studies using high velocity plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, T.; Intrator, T.; Gao, K.

    2012-12-01

    Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create non-thermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and super-Alfvènic supercritical shocks with pre-existing magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Supported by DOE Office of Fusion Energy Sciences and National Nuclear Security Administration under LANS contract DE-AC52-06NA25369 Approved for Public Release: LA-UR-12-22886

  8. Quasiperpendicular High Mach Number Shocks.

    PubMed

    Sulaiman, A H; Masters, A; Dougherty, M K; Burgess, D; Fujimoto, M; Hospodarsky, G B

    2015-09-18

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (M_{A}) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ~0.3τ_{c}, where τ_{c} is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and M_{A} and focus on the magnetic structure of such shocks to further show that for the same M_{A}, a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming. PMID:26430997

  9. Raman spectroscopy of shocked water

    SciTech Connect

    Holmes, N.C.; Mitchell, A.C.; Nellis, W.J.; Graham, W.B.; Walrafen, G.E.

    1983-07-01

    Raman scattering has been used extensively to study the vibrational and rotational properties of molecules under a variety of conditions. Here, interest is in the behavior of water molecules shocked to high pressures and temperatures. Behind the shock front the water molecules undergo changes in bonding and the molecules may become ionized. Raman spectroscopy can be used to determine the molecular species behind the shock front. In addition, changes in Raman spectra can yield information regarding inter- and intramolecular potentials and the temperature behind the shock front.

  10. Shock metamorphism of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Stoeffler, Dieter; Keil, Klaus; Scott, Edward R. D.

    1991-01-01

    This study proposes a revised petrographic classification of progressive stages of shock metamorphism of 26 ordinary chondrites. Six stages of shock (S1 to S6) are defined on the basis of shock effects in olivine and plagioclase as recognized by thin section microscopy, and the characteristic shock effects of each shock stage are described. It is concluded that shock effects and the sequence of progressively increasing degrees of shock metamorphosis are very similar in H, L, and LL groups. Differences in the frequency distribution of shock stages are relatively minor. It is suggested that the collisional histories of the H, L, and LL parent bodies were similar. Petrologic type-3 chondrites are deficient in stages S4 and S6 and, with increasing petrologic type, the frequency of stages S4 to S6 increases. It is suggested that the more porous and volatile-rich Type-3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type. Stage S3 is the most abundant in nearly all petrologic types.

  11. Quasiperpendicular High Mach Number Shocks

    NASA Astrophysics Data System (ADS)

    Sulaiman, A. H.; Masters, A.; Dougherty, M. K.; Burgess, D.; Fujimoto, M.; Hospodarsky, G. B.

    2015-09-01

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (MA ) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ˜0.3 τc , where τc is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA , a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.

  12. Raman spectroscopy of shocked water

    SciTech Connect

    Holmes, N.C.; Nellis, W.J.; Graham, W.B.; Walrafen, G.E.

    1985-08-01

    We describe a new technique for recording spontaneous Raman spectra from molecules during the passage of strong shock waves. We have used this technique to study the OH-stretch band of liquid H/sub 2/O shocked to pressure up to 26 GPa and 1700 K. The shape of the band changes over the range 7.5-26 GPa, and is described well by a two-component mixture model, implying changes in the intermolecular coupling of shock compressed water molecules. We discuss the implications of the spectra on the mechanism responsible for the electrical conductivity of shocked H/sub 2/O. 22 refs., 7 figs., 2 tabs.

  13. Maskelynite: Formation by Explosive Shock.

    PubMed

    Milton, D J; de Carli, P S

    1963-05-10

    When high pressure (250 to 300 kilobars) was applied suddenly (shock-loading) to gabbro, the plagioclase was transformed to a noncrystalline phase (maskelynite) by a solid-state reaction at a low temperature, while the proxene remained crystalline. The shock-loaded gabbro resembles meteorites of the shergottite class; this suggests that the latter formed as a result of shock. The shock-loading of gabbro at 600 to 800 kilobars raised the temperature above the melting range of the plagioclase. PMID:17737107

  14. Martian bow shock - PHOBOS observations

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, K.; Riedler, W.; Lichtenegger, H.; Yeroshenko, Ye.; Sauer, K.; Luhmann, J. G.; Ong, M.; Russell, C. T.

    1990-05-01

    Data obtained with the Magma magnetometer on the subsolar passes of the Phobos spacecraft during its 3 elliptic orbits reveals a turbulent bow shock with a strong foot consistent with the reflection of solar wind protons. The bow shock lies at a subsolar distance of 1.47 + or - .03 R(M). The circular orbit phase of the mission reveals a bow shock with a highly varying location. The median terminator crossing lies at 2.72 Mars radii. The location of the bow shock in the terminator plane is sensitive to neither the EUV flux nor to planetary longitude.

  15. Characterization of Shocked Beryllium

    SciTech Connect

    Cady, Carl M; Adams, Chris D; Hull, Lawrence M; Gray III, George T; Prime, Michael B; Addessio, Francis L; Wynn, Thomas A; Brown, Eric N

    2012-08-24

    Beryllium metal has many excellent structural properties in addition to its unique radiation characteristics, including: high elastic modulus, low Poisson's ratio, low density, and high melting point. However, it suffers from several major mechanical drawbacks: 1) high anisotropy - due to its hexagonal lattice structure and its susceptibility to crystallographic texturing; 2) susceptibility to impurity-induced fracture - due to grain boundary segregation; and 3) low intrinsic ductility at ambient temperatures thereby limiting fabricability. While large ductility results from deformation under the conditions of compression, the material can exhibit a brittle behavior under tension. Furthermore, there is a brittle to ductile transition at approximately 200 C under tensile conditions. While numerous studies have investigated the low-strain-rate constitutive response of beryllium, the combined influence of high strain rate and temperature on the mechanical behavior and microstructure of beryllium has received limited attention over the last 40 years. Prior studies have focused on tensile loading behavior, or limited conditions of dynamic strain rate and/or temperature. The beryllium used in this study was Grade S200-F (Brush Wellman, Inc., Elmore, OH) material. The work focused on high strain rate deformation and examine the validity of constitutive models in deformation rate regimes, including shock, the experiments were modeled using a Lagrangian hydrocode. Two constitutive strength (plasticity) models, the Preston-Tonks-Wallace (PTW) and Mechanical Threshold Stress (MTS) models, were calibrated using the same set of quasi-static and Hopkinson bar data taken at temperatures from 77K to 873K and strain rates from 0.001/sec to 4300/sec. In spite of being calibrated on the same data, the two models give noticeably different results when compared with the measured wave profiles. These high strain rate tests were conducted using both explosive drive and a gas gun to

  16. SHOCK-EXCITED OSCILLATOR

    DOEpatents

    Creveling, R.

    1957-12-17

    S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.

  17. Shocks in supersonic sand.

    PubMed

    Rericha, Erin C; Bizon, Chris; Shattuck, Mark D; Swinney, Harry L

    2002-01-01

    We measure time-averaged velocity, density, and temperature fields for steady granular flow past a wedge. We find the flow to be supersonic with a speed of granular pressure disturbances (sound speed) equal to about 10% of the flow speed, and we observe shocks nearly identical to those in a supersonic gas. Molecular dynamics simulations of Newton's laws yield fields in quantitative agreement with experiment. A numerical solution of Navier-Stokes-like equations agrees with a molecular dynamics simulation for experimental conditions excluding wall friction. PMID:11800951

  18. Shock-fitted Euler solutions to shock-vortex interactions

    NASA Technical Reports Server (NTRS)

    Salas, M. E.; Zang, T. A.; Hussaini, M. Y.

    1982-01-01

    The interaction of a shock wave with a hot spot, a single vortex and a vortex street is studied within the framework of the two dimensional compressible Euler equations. The numerical results obtained by the pseudospectral method and the finite difference MacCormack method are compared. In both the methods the shock wave is fitted as a boundary of the computational domain.

  19. Finite Mach number spherical shock wave, application to shock ignition

    SciTech Connect

    Vallet, A.; Ribeyre, X.; Tikhonchuk, V.

    2013-08-15

    A converging and diverging spherical shock wave with a finite initial Mach number M{sub s0} is described by using a perturbative approach over a small parameter M{sub s}{sup −2}. The zeroth order solution is the Guderley's self-similar solution. The first order correction to this solution accounts for the effects of the shock strength. Whereas it was constant in the Guderley's asymptotic solution, the amplification factor of the finite amplitude shock Λ(t)∝dU{sub s}/dR{sub s} now varies in time. The coefficients present in its series form are iteratively calculated so that the solution does not undergo any singular behavior apart from the position of the shock. The analytical form of the corrected solution in the vicinity of singular points provides a better physical understanding of the finite shock Mach number effects. The correction affects mainly the flow density and the pressure after the shock rebound. In application to the shock ignition scheme, it is shown that the ignition criterion is modified by more than 20% if the fuel pressure prior to the final shock is taken into account. A good agreement is obtained with hydrodynamic simulations using a Lagrangian code.

  20. Dual Mode Shock-Expansion/Reflected-Shock Tunnel

    NASA Technical Reports Server (NTRS)

    Erdos, John I.; Bakos, Robert J.; Castrogiovanni, Anthony; Rogers, R. Clayton

    1998-01-01

    NASA s HYPULSE facility at GASL has been reconfigured to permit free jet testing of the Hyper-X flowpath at flight Mach numbers of 7 and 10. Among the required changes are addition of a converging-diverging nozzle to permit operation in a reflected shock tunnel mode, a 7 ft. diameter test cabin and a 30 in. diameter contoured nozzle. However, none of these changes were allowed to interfere with rapid recovery of the prior shock-expansion tunnel mode of operation, and indeed certain changes should enhance facility usefulness and productivity in either mode. A previously-developed shock-induced detonation mode of driving the facility has been successfully applied to both reflected shock tunnel operation at Mach 10 flight conditions, with tailored interface operation, and shock-expansion tunnel operation at flight conditions corresponding to Mach numbers from 12 to 25. Tailored interface operation at Mach 7 has been achieved with an unheated helium driver. In the present paper, the rationale for a dual mode shock expansion/reflected shock tunnel is discussed, and the capabilities and limitations for each mode are outlined. The physical changes in the HYPULSE facility to achieve dual mode capability are also described. Limited calibration data obtained to date in the new reflected shock tunnel mode are presented and the anticipated flight simulation map with dual mode operation is also outlined.

  1. Finite Mach number spherical shock wave, application to shock ignition

    NASA Astrophysics Data System (ADS)

    Vallet, A.; Ribeyre, X.; Tikhonchuk, V.

    2013-08-01

    A converging and diverging spherical shock wave with a finite initial Mach number Ms0 is described by using a perturbative approach over a small parameter Ms-2. The zeroth order solution is the Guderley's self-similar solution. The first order correction to this solution accounts for the effects of the shock strength. Whereas it was constant in the Guderley's asymptotic solution, the amplification factor of the finite amplitude shock Λ(t)∝dUs/dRs now varies in time. The coefficients present in its series form are iteratively calculated so that the solution does not undergo any singular behavior apart from the position of the shock. The analytical form of the corrected solution in the vicinity of singular points provides a better physical understanding of the finite shock Mach number effects. The correction affects mainly the flow density and the pressure after the shock rebound. In application to the shock ignition scheme, it is shown that the ignition criterion is modified by more than 20% if the fuel pressure prior to the final shock is taken into account. A good agreement is obtained with hydrodynamic simulations using a Lagrangian code.

  2. Phase detonated shock tube (PFST)

    SciTech Connect

    Zerwekh, W.D.; Marsh, S.P.; Tan, Tai-Ho

    1993-07-01

    The simple, cylindrically imploding and axially driven fast shock tube (FST) has been a basic component in the high velocity penetrator (HVP) program. It is a powerful device capable of delivering a directed and very high pressure output that has been successfully employed to drive hypervelocity projectiles. The FST is configured from a hollow, high-explosive (HE) cylinder, a low-density Styrofoam core, and a one-point initiator at one end. A Mach stem is formed in the core as the forward-propagating, HE detonation wave intersects the reflected radial wave. This simple FST has been found to be a powerful pressure multiplier. Up to 1-Mbar output pressure can be obtained from this device. Further increase in the output pressure can be achieved by increasing the HE detonation velocity. The FST has been fine tuned to drive a thin plate to very high velocity under an impulse per unit area of about 1 Mbar{mu}s/cm{sup 2}. A 1.5-mm-thick stainless steel disk has been accelerated intact to 0.8 cm/{mu}s under a loading pressure rate of several Mbar/{mu}s. By making the plate curvature slightly convex at the loading side the authors have successfully accelerated it to almost 1.0 cm/{mu}s. The incorporation of a barrel at the end of the FST has been found to be important as confinement of the propellant gas by the barrel tends to accelerate the projectile to higher velocity. The desire to accelerate the plate above 1.0 cm/{mu}s provided the impetus to develop a more advanced fast shock tube to deliver a much higher output pressure. This report describes the investigation of a relatively simple air-lens phase-detonation system (PFST) with fifty percent higher phase-detonation velocity and a modest 2 Mbar output. Code calculations have shown that this PFST acceleration of a plate to about 1.2 cm/{mu}s can be achieved. The performance of these PFSTs has been evaluated and the details are discussed.

  3. Phase detonated shock tube (PFST)

    SciTech Connect

    Zerwekh, W.D.; Marsh, S.P.; Tan, Tai-Ho.

    1993-01-01

    The simple, cylindrically imploding and axially driven fast shock tube (FST) has been a basic component in the high velocity penetrator (HVP) program. It is a powerful device capable of delivering a directed and very high pressure output that has been successfully employed to drive hypervelocity projectiles. The FST is configured from a hollow, high-explosive (HE) cylinder, a low-density Styrofoam core, and a one-point initiator at one end. A Mach stem is formed in the core as the forward-propagating, HE detonation wave intersects the reflected radial wave. This simple FST has been found to be a powerful pressure multiplier. Up to 1-Mbar output pressure can be obtained from this device. Further increase in the output pressure can be achieved by increasing the HE detonation velocity. The FST has been fine tuned to drive a thin plate to very high velocity under an impulse per unit area of about 1 Mbar[mu]s/cm[sup 2]. A 1.5-mm-thick stainless steel disk has been accelerated intact to 0.8 cm/[mu]s under a loading pressure rate of several Mbar/[mu]s. By making the plate curvature slightly convex at the loading side the authors have successfully accelerated it to almost 1.0 cm/[mu]s. The incorporation of a barrel at the end of the FST has been found to be important as confinement of the propellant gas by the barrel tends to accelerate the projectile to higher velocity. The desire to accelerate the plate above 1.0 cm/[mu]s provided the impetus to develop a more advanced fast shock tube to deliver a much higher output pressure. This report describes the investigation of a relatively simple air-lens phase-detonation system (PFST) with fifty percent higher phase-detonation velocity and a modest 2 Mbar output. Code calculations have shown that this PFST acceleration of a plate to about 1.2 cm/[mu]s can be achieved. The performance of these PFSTs has been evaluated and the details are discussed.

  4. Novel therapies for septic shock over the past 4 decades.

    PubMed

    Suffredini, Anthony F; Munford, Robert S

    2011-07-13

    Infections that result in shock and organ failure are a major public health problem worldwide. Severe sepsis and septic shock affect patients of all ages and often complicate chronic diseases. They are the major causes of death in critical care units and contribute substantially to hospital inpatient costs. Translating the scientific advances of the last 4 decades into clinical practice has been challenging. Despite many attempts to develop new therapies, the basic elements of treatment have not changed since the 1960s. In this Grand Rounds, we summarize the results of the clinical trials conducted during the last 4 decades, discuss some lessons learned, and suggest possible directions for future investigation. PMID:21750297

  5. Generation of ultrafast optical fiducials for shock-wave experiments

    NASA Astrophysics Data System (ADS)

    Dodson, B. W.

    Recent advances in high time resolution optical diagnostic instrumentation for shock wave experiments in condensed media (especially timing resolved spectroscopy) have resulted in new challenges concerning the timing of such experiments. A technique for detecting the presence of a shock wave through the generation of an optical fiducial signal, which is detected and recorded directly by the optical recording device (typically a streak camera) is presented. This technique, which is based on Stress Induced Defeat of Total Internal Reflection (SIDTIR), requires only simple apparatus and set up, and offers fiducial transition times as short as 50 psec in a reasonable experimental configuration.

  6. IPShocks: Database of Interplanetary Shock Waves

    NASA Astrophysics Data System (ADS)

    Isavnin, Alexey; Lumme, Erkka; Kilpua, Emilia; Lotti, Mikko; Andreeova, Katerina; Koskinen, Hannu; Nikbakhsh, Shabnam

    2016-04-01

    Fast collisionless shocks are one of the key interplanetary structures, which have also paramount role for solar-terrestrial physics. In particular, coronal mass ejection driven shocks accelerate particles to high energies and turbulent post-shock flows may drive intense geomagnetic storms. We present comprehensive Heliospheric Shock Database (ipshocks.fi) developed and hosted at University of Helsinki. The database contains currently over 2000 fast forward and fast reverse shocks observed by Wind, ACE, STEREO, Helios, Ulysses and Cluster spacecraft. In addition, the database has search and sort tools based on the spacecraft, time range, and several key shock parameters (e.g., shock type, shock strength, shock angle), data plots for each shock and data download options. These features allow easy access to shocks and quick statistical analyses. All current shocks are identified visually and analysed using the same procedure.

  7. How Culture Shock Affects Communication.

    ERIC Educational Resources Information Center

    Barna, LaRay M.

    The paper defines the term "culture shock" and discusses the changes that this state can make in a person's behavior. Culture shock refers to the emotional and physiological reaction of high activation that is brought about by sudden immersion in a new culture. Because one's own culture shields one from the unknown and reduces the need to make…

  8. Reading, Writing, and Culture Shock.

    ERIC Educational Resources Information Center

    Damen, Louise

    Considerations for identifying the stages of cultural learning of individual students of English as a second language (ESL) are discussed. It is suggested that culture shock, or the shock of the new, is a common experience for those learning a second language in a second culture, and that anger, unhappiness, frustration, and even illness may…

  9. Dynamic shock studies of vanadium

    SciTech Connect

    Chhabildas, L.C.; Hills, C.R.

    1985-01-01

    Using gas-gun loading techniques and velocity interferometric techniques, time-resolved wave profiles have been obtained in vanadium over the stress range of 2.9 to 9.7 GPa. The risetime data indicate steepened shock structures with increasing shock amplitude. However, unlike aluminum, finite risetimes are determined even at 9.7 GPa, indicating a large effective viscosity for the material. The dynamic yield strength measured at the Hugoniot elastic limit is 0.8 GPa and is approximately twice the static yield strength. Material softening is evidenced through measurements of shock velocity and yield strength determinations in the shocked state. The yield strength of the material upon release from the shocked state is estimated to be approx.0.43 GPa and is comparable to the static yield strength. Strain-rate dependent processes may be responsible for a higher elastic shear stress sustained before relaxation to an equilibrium value. The primary mode of deformation in shocked vanadium appears to be cross slip, resulting in dislocation tangles. Deformation twins are also observed in shock-recovered specimens with an increasing number with increased shock stress. The thermal diffusivity for vanadium is low, and the shear-strength loss observed in this material is consistent with the strength loss observed for other materials which also have low thermal diffusivities. It is conceivable that the loss of shear strength may be due to long thermal recovery times resulting from inhomogeneous deformation process.

  10. Turbulence in argon shock waves

    NASA Technical Reports Server (NTRS)

    Johnson, J. A., III; Santiago, J. P.; I, L.

    1981-01-01

    Irregular density fluctuations with turbulent-like behaviors are found in ionizing shock fronts produced by an arc-driven shock tube. Electric probes are used as the primary diagnostic. Spectral analyses show statistical patterns which seem frozen-in and characterizable by a dominant mode and its harmonics.

  11. Pin puller impact shock attenuation

    NASA Technical Reports Server (NTRS)

    Auclair, G. F.; Leonard, B. S.; Robbins, R. E.; Proffitt, W. L.

    1976-01-01

    Design of a pin arresting mechanism for a pyrotechnically actuated pin puller is reviewed. The investigative approach is discussed and the impact shock test results for various candidate designs are presented. The selected pin arresting design reduced the peak value of the shock response spectrum by five to one.

  12. Shock Wave Lithotripsy

    MedlinePlus

    ... an organ donor. Professionals GFR CME/CE Primary Care Clinician Tools Guidelines Physicians Pharmacists Advanced Practitioners Nurses & Technicians Dietitians Social Workers Spring Clinical Meetings Local Chapters Journals Education & Research Kidney Career Center Featured Story GFR You can ...

  13. Self-sustained shock oscillations on airfoils at transonic speeds

    NASA Astrophysics Data System (ADS)

    Lee, B. H. K.

    2001-02-01

    Self-sustained shock wave oscillations on airfoils at transonic flow conditions are associated with the phenomenon of buffeting. The physical mechanisms of the periodic shock motion are not yet fully understood even though experiments performed over fifty years ago have demonstrated the presence of oscillatory shock waves on the airfoil surfaces at high subsonic speeds. The unsteady pressure fluctuations generated by the low-frequency large-amplitude shock motions are highly undesirable from the structural integrity and aircraft maneuverability point of view. For modern supercritical wing design with thick profiles, the shock-induced fluctuations are particularly severe and methods to reduce the shock wave amplitudes to lower values or even to delay the oscillations to higher Mach numbers or incidence angles will result in expanding the buffet boundary of the airfoil. This review begins with a recapitulation of the classical work on shock-induced bubble separation and trailing edge separation of a turbulent boundary layer. The characteristics of the unsteady pressure fluctuations are used to classify the types of shock-boundary layer interaction. The various modes of shock wave motion for different flow conditions and airfoil configurations are described. The buffet boundaries obtained using the standard trailing edge pressure divergence technique and an alternative approach of measuring the divergence of normal fluctuating forces are compared to show the equivalence. The mechanisms of self-sustained shock oscillations are discussed for symmetrical circular-arc airfoils at zero incidence and for supercritical airfoils at high incidence angles with fully separated flows. The properties of disturbances in the wake are examined from linear stability analysis of two-dimensional compressible flows. The advances in high-speed computing make predictions of buffeting flows possible. Navier-Stokes solvers and approximate boundary layer-inviscid flow interaction methods are

  14. Floating shock fitting via Lagrangian adaptive meshes

    NASA Technical Reports Server (NTRS)

    Vanrosendale, John

    1995-01-01

    In recent work we have formulated a new approach to compressible flow simulation, combining the advantages of shock-fitting and shock-capturing. Using a cell-centered on Roe scheme discretization on unstructured meshes, we warp the mesh while marching to steady state, so that mesh edges align with shocks and other discontinuities. This new algorithm, the Shock-fitting Lagrangian Adaptive Method (SLAM), is, in effect, a reliable shock-capturing algorithm which yields shock-fitted accuracy at convergence.

  15. A study of shock mitigating materials in a split Hopkinson bar configuration

    SciTech Connect

    Bateman, V.I.; Bell, R.G. III; Brown, F.A.; Hansen, N.R.

    1996-12-31

    Sandia National Laboratories (SNL) designs mechanical systems with electronics that must survive high shock environments. These mechanical systems include penetrators that must survive soil, rock, and ice penetration, nuclear transportation casks that must survive transportation environments, and laydown weapons that must survive delivery impact of 125-fps. These mechanical systems contain electronics that may operate during and after the high shock environment and that must be protected from the high shock environments. A study has been started to improve the packaging techniques for the advanced electronics utilized in these mechanical systems because current packaging techniques are inadequate for these more sensitive electronics. In many cases, it has been found that the packaging techniques currently used not only do not mitigate the shock environment but actually amplify the shock environment. An ambitious goal for this packaging study is to avoid amplification and possibly attenuate the shock environment before it reaches the electronics contained in the various mechanical system. As part of the investigation of packaging techniques, a two part study of shock mitigating materials is being conducted. This paper reports the first part of the shock mitigating materials study. A study to compare three thicknesses (0.125, 0.250, and 0.500 in.) of seventeen, unconfined materials for their shock mitigating characteristics has been completed with a split Hopkinson bar configuration. The nominal input as measured by strain gages on the incident Hopkinson bar is 50 fps {at} 100 {micro}s for these tests. It is hypothesized that a shock mitigating material has four purposes: to lengthen the shock pulse, to attenuate the shock pulse, to mitigate high frequency content in the shock pulse, and to absorb energy. Both time domain and frequency domain analyses of the split Hopkinson bar data have been performed to compare the materials` achievement of these purposes.

  16. Shock transmissibility of threaded joints

    SciTech Connect

    Hansen, N.R.; Bateman, V.I.; Brown, F.A.

    1996-12-31

    Sandia National Laboratories (SNL) designs mechanical systems with threaded joints that must survive high shock environments. These mechanical systems include penetrators that must survive soil and rock penetration; drilling pipe strings that must survive rock-cutting, shock environments; and laydown weapons that must survive delivery impact shock. This paper summarizes an analytical study and an experimental evaluation of compressive, one-dimensional, shock transmission through a threaded joint in a split Hopkinson bar configuration. Thread geometries were scaled to simulate large diameter threaded joints with loadings parallel to the axis of the threads. Both strain and acceleration were evaluated with experimental measurements and analysis. Analytical results confirm the experimental conclusions that in this split Hopkinson bar configuration, the change in the one-dimensional shock wave by the threaded joint is localized to a length equal to a few diameters` length beyond the threaded joint.

  17. [Vasopressin use in shock].

    PubMed

    Carrillo-Esper, Raúl; González-Salazar, Jorge A; Calvo-Carrillo, Benjamín

    2004-01-01

    Arginine-vasopressin (VP), also known as the antidiuretic hormone, is essential for water homeostasis. Its synthesis and liberation depends on regulation of osmotic, hypovolemic, hormonal, and nonosmotic stimuli. It has been demonstrated that it is key for maintenance of cardiovascular homeostasis through vasomotor regulation, the determinant of systemic vascular resistance and mean arterial pressure, a process acting through V1 receptors. Shock state with refractory vasodilation seen in sepsis, systemic inflammatory response, hypovolemia, cardiac arrest, polytrauma, etc., is characterized by an initial phase of liberation and increased levels of VP followed by a second phase characterized by inappropriately low levels of this hormone that are associated with refractoriness to management with volume, inotropics, and vasopressors. It has been demonstrated in clinical and experimental studies that exogenous VP treatment under this condition increases systemic vascular resistance, perfusion pressure, and oxygen supply to peripheral tissues, which makes it possible to decrease and to suspend vasopressors and also to increase survival. PMID:15022889

  18. Vorticity interaction effects on blunt bodies. [hypersonic viscous shock layers

    NASA Technical Reports Server (NTRS)

    Anderson, E. C.; Wilcox, D. C.

    1977-01-01

    Numerical solutions of the viscous shock layer equations governing laminar and turbulent flows of a perfect gas and radiating and nonradiating mixtures of perfect gases in chemical equilibrium are presented for hypersonic flow over spherically blunted cones and hyperboloids. Turbulent properties are described in terms of the classical mixing length. Results are compared with boundary layer and inviscid flowfield solutions; agreement with inviscid flowfield data is satisfactory. Agreement with boundary layer solutions is good except in regions of strong vorticity interaction; in these flow regions, the viscous shock layer solutions appear to be more satisfactory than the boundary layer solutions. Boundary conditions suitable for hypersonic viscous shock layers are devised for an advanced turbulence theory.

  19. Frequency shift measurement in shock-compressed materials

    DOEpatents

    Moore, David S.; Schmidt, Stephen C.

    1985-01-01

    A method for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the shock front advancing through the sample, thereby minimizing adverse effects of refraction.

  20. Cosmic-ray shock acceleration in oblique MHD shocks

    NASA Technical Reports Server (NTRS)

    Webb, G. M.; Drury, L. OC.; Volk, H. J.

    1986-01-01

    A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.

  1. The cosmic-ray shock structure problem for relativistic shocks

    NASA Technical Reports Server (NTRS)

    Webb, G. M.

    1985-01-01

    The time asymptotic behaviour of a relativistic (parallel) shock wave significantly modified by the diffusive acceleration of cosmic-rays is investigated by means of relativistic hydrodynamical equations for both the cosmic-rays and thermal gas. The form of the shock structure equation and the dispersion relation for both long and short wavelength waves in the system are obtained. The dependence of the shock acceleration efficiency on the upstream fluid spped, long wavelength Mach number and the ratio N = P sub co/cP sub co+P sub go)(Psub co and P sub go are the upstream cosmic-ray and thermal gas pressures respectively) are studied.

  2. Oblique shock reflection from an axis of symmetry: shock dynamics and relation to the Guderley singularity

    NASA Astrophysics Data System (ADS)

    Hornung, H. G.; Schwendeman, D. W.

    2001-07-01

    Oblique shock reflection from an axis of symmetry is studied using Whitham's theory of geometrical shock dynamics, and the results are compared with previous numerical simulations of the phenomenon by Hornung (2000). The shock shapes (for strong and weak shocks), and the location of the shock-shock (for strong shocks), are in good agreement with the numerical results, though the detail of the shock reflection structure is, of course, not resolved by shock dynamics. A guess at a mathematical form of the shock shape based on an analogy with the Guderley singularity in cylindrical shock implosion, in the form of a generalized hyperbola, fits the shock shape very well. The smooth variation of the exponent in this equation with initial shock angle from the Guderley value at zero to 0.5 at 90° supports the analogy. Finally, steady-flow shock reflection from a symmetry axis is related to the self-similar flow.

  3. Micas in experimentally shocked gneiss

    NASA Technical Reports Server (NTRS)

    Lambert, P.; Mackinnon, I. D. R.

    1984-01-01

    Powder-propellant guns are used to shock biotites and muscovites from a gneiss at pressures between 18 and 70 GPa. It is shown that shock in biotite and muscovite can produce homogeneous and devolatilized glasses within microseconds. Shock-deformed micas are found to exhibit fracturing, kinking, and complex extinction patterns over the entire pressure range investigated. Localized melting of micas commences at 33 GPa and reaches completion at 70 GPa. Even though melted biotite and muscovite are opaque optically, they exhibit extensive microvesiculation and flow when observed with the SEM. It is confirmed through electron diffraction that biotite and muscovite have transformed to a glass. The distribution of vesicles in shock-vitrified mica reveals escape of volatiles within the short duration of the shock experiment. It is noted that experimentally shocked biotite and muscovite undergo congruent melting. It is noted that the compositions of the glasses are similar to the unshocked micas except for volatiles (H2O loss and and K loss). These unusual glasses produced from mica can be quenched by rapid cooling conditions during the shock experiment. On the basis of the results, it is pointed out that the extremely low H2O content of tektites can be reconciled with a terrestrial origin by impact.

  4. Cardiogenic shock and nutrition: safe?

    PubMed

    Thibault, Ronan; Pichard, Claude; Wernerman, Jan; Bendjelid, Karim

    2011-01-01

    Cardiogenic shock is a common diagnosis in patients in the intensive care unit (ICU), and is characterized by a decreased cardiac output in the presence of adequate intravascular volume associated with an inadequate tissue perfusion including a physiological reduction in the splanchnic territory. It may occur in isolation as a reflection of cardiac pathology, or it may be part of a shock syndrome involving other pathogenic mechanisms. As the use of enteral nutrition (EN) is associated with an increase in mesenteric arterial output, EN could be deleterious by overwhelming the mechanisms of mesenteric adaptation. Accordingly, EN has been suspected to increase the risk of mesenteric ischaemia, bacterial translocation and sepsis in ICU patients with cardiogenic shock. International guidelines recommend a cautious use of EN within 72 h following cardiogenic shock. Recent evidence indicates that mesenteric arterial output may decrease during parenteral nutrition administration, suggesting that parenteral nutrition could have a protective effect on splanchnic organs in ICU patients with cardiogenic shock. Contrary to former beliefs, several meta-analyses have shown that parenteral nutrition is not associated with increased mortality. Exclusive EN is associated with negative energy balance and the combination of EN with supplemental parenteral nutrition during the first days following ICU admission has been proposed to prevent negative energy balance. Such a nutritional strategy could also be beneficial for the mesenteric circulation in cardiogenic shock, and consequently may improve the clinical outcome of patients with cardiogenic shock. Clinical trials are warranted to verify these hypotheses. PMID:21086113

  5. Chondrule destruction in nebular shocks

    SciTech Connect

    Jacquet, Emmanuel; Thompson, Christopher

    2014-12-10

    Chondrules are millimeter-sized silicate spherules ubiquitous in primitive meteorites, but whose origin remains mysterious. One of the main proposed mechanisms for producing them is melting of solids in shock waves in the gaseous protoplanetary disk. However, evidence is mounting that chondrule-forming regions were enriched in solids well above solar abundances. Given the high velocities involved in shock models, destructive collisions would be expected between differently sized grains after passage of the shock front as a result of differential drag. We investigate the probability and outcome of collisions of particles behind a one-dimensional shock using analytic methods as well as a full integration of the coupled mass, momentum, energy, and radiation equations. Destruction of protochondrules seems unavoidable for solid/gas ratios ε ≳ 0.1, and possibly even for solar abundances because of 'sandblasting' by finer dust. A flow with ε ≳ 10 requires much smaller shock velocities (∼2 versus 8 km s{sup –1}) in order to achieve chondrule-melting temperatures, and radiation trapping allows slow cooling of the shocked fragments. Initial destruction would still be extensive; although re-assembly of millimeter-sized particles would naturally occur by grain sticking afterward, the compositional heterogeneity of chondrules may be difficult to reproduce. We finally note that solids passing through small-scale bow shocks around few kilometer-sized planetesimals might experience partial melting and yet escape fragmentation.

  6. Chondrule Destruction in Nebular Shocks

    NASA Astrophysics Data System (ADS)

    Jacquet, Emmanuel; Thompson, Christopher

    2014-12-01

    Chondrules are millimeter-sized silicate spherules ubiquitous in primitive meteorites, but whose origin remains mysterious. One of the main proposed mechanisms for producing them is melting of solids in shock waves in the gaseous protoplanetary disk. However, evidence is mounting that chondrule-forming regions were enriched in solids well above solar abundances. Given the high velocities involved in shock models, destructive collisions would be expected between differently sized grains after passage of the shock front as a result of differential drag. We investigate the probability and outcome of collisions of particles behind a one-dimensional shock using analytic methods as well as a full integration of the coupled mass, momentum, energy, and radiation equations. Destruction of protochondrules seems unavoidable for solid/gas ratios epsilon >~ 0.1, and possibly even for solar abundances because of "sandblasting" by finer dust. A flow with epsilon >~ 10 requires much smaller shock velocities (~2 versus 8 km s-1) in order to achieve chondrule-melting temperatures, and radiation trapping allows slow cooling of the shocked fragments. Initial destruction would still be extensive; although re-assembly of millimeter-sized particles would naturally occur by grain sticking afterward, the compositional heterogeneity of chondrules may be difficult to reproduce. We finally note that solids passing through small-scale bow shocks around few kilometer-sized planetesimals might experience partial melting and yet escape fragmentation.

  7. Preliminary investigation of interplanetary shock structure: Quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Greenstadt, E. W.

    1974-01-01

    Pioneer 9's magnetic field and plasma data were studied to develop arguments for or against the observation of oblique interplanetary shocks. Structural classifications are defined, and the justification for seeking these classifications in the solar wind are presented.

  8. Shock temperature measurements in ammonia

    SciTech Connect

    Radousky, H.B.; Mitchell, A.C.; Nellis, W.J.; Ross, M.

    1985-07-01

    Our first shock temperature measurements on a cryogenic target are reported for NH/sub 3/. A new fast optical pyrometer and a cryogenic specimen holder for liquid NH/sub 3/ were developed to measure shock temperatures of 4400 and 3600 K at pressures of 61 and 48 GPa. These conditions correspond to those in the ice layers in Uranus and Neptune. The shock temperature data are in reasonable agreement with an equation of state based on an intermolecular potential derived from NH/sub 3/ Hugoniot data.

  9. Double layers and electrostatic shocks

    NASA Technical Reports Server (NTRS)

    Hershkowitz, N.

    1981-01-01

    It is shown that it is useful to define double layers and shocks so that the ion phase spaces of double layers are the mirror image (about zero ion velocity) of the ion phase spaces for laminar electrostatic shocks. The distinguishing feature is the direction of the free ion velocity. It is also shown that double layers can exist without the presence of trapped ions. The Bohm condition for double layers, that the ion drift velocity on the high potential side must be greater than the ion sound velocity, is shown to be related to a requirement of a lower limit on the Mach number of laminar electrostatic shocks

  10. Stishovite: Synthesis by shock wave

    USGS Publications Warehouse

    De Carli, P. S.; Milton, D.J.

    1965-01-01

    Small amounts of stishovite were separated from specimens of explosively shocked sandstones, novaculite, and single-crystal quartz. Estimated peak pressures for the syntheses ranged from 150 to 280 kilobars, and shock temperatures were from 150?? to 900??C. No coesite was detected in any sample. It is suggested that quartz can invert during shock to a short-range-order phase, with sixfold coordination. A small portion of this phase may develop the long-range order of stishovite, and, during the more protracted decrease of the pressure pulse through the stability field of coesite accompanying meteorite crater formation, a portion may invert to coesite.

  11. Slow shocks around the sun

    NASA Technical Reports Server (NTRS)

    Whang, Y. C.

    1982-01-01

    It is inferred from this study that magnetohydrodynamic slow shocks can exist in the vicinity of the sun. The study uses a two-hole corona model, the sub-Alfvenic streams originating from the edge of the polar open-field regions are forced to turn towards equator in coronal space following the curved boundary of the closed field region. When the streamlines from the opposite poles merge at a neutral point, their directions become parallel to the neutral sheet. An oblique slow shock can develop near or at the neutral point, the shock extends polewards to form a surface of discontinuity around the sun.

  12. [Septic shock in intensive care units. Current focus on treatment].

    PubMed

    Arriagada S, Daniela; Donoso F, Alejandro; Cruces R, Pablo; Díaz R, Franco

    2015-01-01

    Essential therapeutic principles in children with septic shock persist over time, although some new concepts have been recently incorporated, and fully awareness of pediatricians and intensivists is essential. Fluid resuscitation is a fundamental intervention, but the kind of ideal fluid has not been established yet, as each of these interventions has specific limitations and there is no evidence supportive of the superiority of one type of fluid. Should septic shock persists despite adequate fluid resuscitation, the use of inotropic medication and/or vasopressors is indicated. New vasoactive drugs can be used in refractory septic shock caused by vasopressors, and the use of hydrocortisone should be considered in children with suspected adrenal insufficiency, as it reduces the need for vasopressors. The indications for red blood cells transfusion or the optimal level of glycemia are still controversial, with no consensus on the threshold value for the use of these blood products or the initiation of insulin administration, respectively. Likewise, the use of high-volume hemofiltration is a controversial issue and further study is needed on the routine recommendation in the course of septic shock. Nutritional support is crucial, as malnutrition is a serious complication that should be properly prevented and treated. The aim of this paper is to provide update on the most recent advances as concerns the treatment of septic shock in the pediatric population. PMID:26323988

  13. Constraining the efficiency of cosmic ray acceleration by cluster shocks

    NASA Astrophysics Data System (ADS)

    Vazza, F.; Brüggen, M.; Wittor, D.; Gheller, C.; Eckert, D.; Stubbe, M.

    2016-06-01

    We study the acceleration of cosmic rays by collisionless structure formation shocks with ENZO grid simulations. Data from the Fermi satellite enable the use of galaxy clusters as a testbed for particle acceleration models. Based on advanced cosmological simulations that include different prescriptions for gas and cosmic rays physics, we use the predicted γ-ray emission to constrain the shock acceleration efficiency. We infer that the efficiency must be on average ≤10-3 for cosmic shocks, particularly for the M ˜ 2-5 merger shocks that are mostly responsible for the thermalization of the intracluster medium (ICM). These results emerge, both, from non-radiative and radiative runs including feedback from active galactic nuclei, as well as from zoomed resimulations of a cluster resembling MACSJ1752.0+0440. The limit on the acceleration efficiency we report is lower than what has been assumed in the literature so far. Combined with the information from radio emission in clusters, it appears that a revision of the present understanding of shock acceleration in the ICM is unavoidable.

  14. Shock-fitted Euler solutions to shock vortex interactions

    NASA Technical Reports Server (NTRS)

    Salas, M. D.; Zang, T. A.; Mussaini, M. Y.

    1982-01-01

    The interaction of a planar shock wave with one or more vortexes is computed using a pseudospectral method and a finite difference method. The development of the spectral method is emphasized. In both methods the shock wave is fitted as a boundary of the computational domain. The results show good agreement between both computational methods. The spectral method is, however, restricted to smaller time steps and requires use of filtering techniques.

  15. Shock compaction of magnet powder using underwater shock wave

    SciTech Connect

    Kubota, Shiro; Fujita, Masahiro; Itoh, Shigeru

    1996-12-31

    In order to get a high plug density (over 90%), the authors tried a direct consolidation of the magnet powder using the converging underwater shock wave created by the underwater explosion of explosives. The processes of the consolidation of the magnet powder were investigated by numerical calculation. They obtained the parameters of the EOS (Petrie-Page model) for Magnet powder using quasi-static loading experiments. Moreover, the characteristics of the shock compaction assembly were also verified.

  16. Quasilinear simulations of interplanetary shocks and Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Afanasiev, Alexandr; Battarbee, Markus; Ganse, Urs; Vainio, Rami; Palmroth, Minna; Pfau-Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian

    2016-04-01

    We have developed a new self-consistent Monte Carlo simulation model for particle acceleration in shocks. The model includes a prescribed large-scale magnetic field and plasma density, temperature and velocity profiles and a self-consistently computed incompressible ULF foreshock under the quasilinear approximation. Unlike previous analytical treatments, our model is time dependent and takes full account of the anisotropic particle distributions and scattering in the wave-particle interaction process. We apply the model to the problem of particle acceleration at traveling interplanetary (IP) shocks and Earth's bow shock and compare the results with hybrid-Vlasov simulations and spacecraft observations. A qualitative agreement in terms of spectral shape of the magnetic fluctuations and the polarization of the unstable mode is found between the models and the observations. We will quantify the differences of the models and explore the region of validity of the quasilinear approach in terms of shock parameters. We will also compare the modeled IP shocks and the bow shock, identifying the similarities and differences in the spectrum of accelerated particles and waves in these scenarios. The work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324 (HESPERIA). The Academy of Finland is thanked for financial support. We acknowledge the computational resources provided by CSC - IT Centre for Science Ltd., Espoo.

  17. Optimal triple configurations of stationary shocks

    NASA Astrophysics Data System (ADS)

    Tao, G.; Uskov, V. N.; Chernyshov, M. V.

    Shock-wave systems consisted of three stationary shocks with common (triple) point T (Fig. 1,a-e) are called triple configurations. The slipstream (τ) emanates from the triple point and divides the streams that have gone through the sequence of shocks 1-2 and through the alone (main) shock 3 at another side of the triple point.

  18. Dehydration kinetics of shocked serpentine

    NASA Technical Reports Server (NTRS)

    Tyburczy, James A.; Ahrens, Thomas J.

    1988-01-01

    Experimental rates of dehydration of shocked and unshocked serpentine were determined using a differential scanning calorimetric technique. Dehydration rates in shocked serpentine are enhanced by orders of magnitude over corresponding rates in unshocked material, even though the impact experiments were carried out under conditions that inhibited direct impact-induced devolatilization. Extrapolation to temperatures of the Martian surface indicates that dehydration of shocked material would occur 20 to 30 orders of magnitude more rapidly than for unshocked serpentine. The results indicate that impacted planetary surfaces and associated atmospheres would reach chemical equilibrium much more quickly than calculations based on unshocked material would indicate, even during the earliest, coldest stages of accretion. Furthermore, it is suggested that chemical weathering of shocked planetary surfaces by solid-gas reactions would be sufficiently rapid that true equilibrium mineral assemblages should form.

  19. Low-Shock Pyrotechnic Actuator

    NASA Technical Reports Server (NTRS)

    Lucy, M. H.

    1984-01-01

    Miniature 1-ampere, 1-watt pyrotechnic actuator enclosed in flexible metal bellows. Bellows confines outgassing products, and pyrotechnic shock reduction achieved by action of bellows, gas cushion within device, and minimum use of pyrotechnic material. Actuator inexpensive, compact, and lightweight.

  20. Shock compression of liquid hydrazine

    SciTech Connect

    Garcia, B.O.; Chavez, D.J.

    1996-05-01

    Liquid hydrazine (N{sub 2}H{sub 4}) is a propellant used for aerospace propulsion and power systems. Because the propellant modules can be subject to debris impacts during their use, the shock states that can occur in the hydrazine need to be characterized to safely predict its response. Several shock compression experiments have been conducted to investigate the shock detonability of liquid hydrazine; however, the experiments{close_quote} results disagree. Therefore, in this study, we reproduced each experiment numerically to evaluate in detail the shock wave profiles generated in the liquid hydrazine. This paper presents the results of each numerical simulation and compares the results to those obtained in experiment. {copyright} {ital 1996 American Institute of Physics.}

  1. Undercuts by Laser Shock Forming

    SciTech Connect

    Wielage, Hanna; Vollertsen, Frank

    2011-05-04

    In laser shock forming TEA-CO{sub 2}-laser induced shock waves are used to form metal foils, such as aluminum or copper. The process utilizes an initiated plasma shock wave on the target surface, which leads to a forming of the foil. A challenge in forming technologies is the manufacturing of undercuts. By conventional forming methods these special forms are not feasible. In this article, it is presented that undercuts in the micro range can be produced by laser shock deep drawing. Different drawing die diameters, drawing die depths and the material aluminum in the thicknesses 20 and 50 {mu}m were investigated. It will be presented that smaller die diameters facilitate undercuts compared to bigger die diameters. The phenomena can be explained by Barlow's formula. Furthermore, it is shown which maximum undercut depth at different die diameters can be reached. To this end, cross-sections of the different parameter combinations are displayed.

  2. Annular arc accelerator shock tube

    NASA Technical Reports Server (NTRS)

    Leibowitz, L. P. (Inventor)

    1976-01-01

    An annular arc accelerator shock tube employs a cold gas driver to flow a stream of gas from an expansion section through a high voltage electrode section to a test section, thus driving a shock wave in front of it. A glow discharge detects the shock wave and actuates a trigger generator which in turn fires spark-gap switches to discharge a bank of capacitors across a centered cathode and an annular anode in tandem electrode sections. The initial shock wave passes through the anode section from the cathode section thereby depositing energy into the flow gas without the necessity of any diaphragm opening in the gas flow from the expansion section through the electrode sections.

  3. Rayleigh-Taylor Shock Waves

    SciTech Connect

    Olson, B J; Cook, A W

    2007-08-30

    Beginning from a state of hydrostatic equilibrium, in which a heavy gas rests atop a light gas in a constant gravitational field, Rayleigh-Taylor instability at the interface will launch a shock wave into the upper fluid. The rising bubbles of lighter fluid act like pistons, compressing the heavier fluid ahead of the fronts and generating shocklets. These shocklets coalesce in multidimensional fashion into a strong normal shock, which increases in strength as it propagates upwards. Large-eddy simulations demonstrate that the shock Mach number increases faster in three dimensions than it does in two dimensions. The generation of shocks via Rayleigh-Taylor instability could have profound implications for astrophysical flows.

  4. Toxic Shock Syndrome (For Parents)

    MedlinePlus

    ... Problems Talking to Your Child About Menstruation Cellulitis MRSA Staph Infections What Are Germs? Why Is Hand ... in? Feeling Fresh All About Menstruation Staph Infections MRSA Toxic Shock Syndrome Contact Us Print Resources Send ...

  5. 'Shocking' Obedience Found in Children

    ERIC Educational Resources Information Center

    Science News, 1977

    1977-01-01

    Describes a Stanley Milgram type obedience experiment conducted with 192 Jordanian children ages 6-16. Seventy-three percent of the children responded via administering supposed dangerous electrical shocks to test subjects. (SL)

  6. Review of research into shock control bumps

    NASA Astrophysics Data System (ADS)

    Bruce, P. J. K.; Colliss, S. P.

    2015-09-01

    This paper presents a review of research on shock control bumps (SCBs), a class of flow control device with potential for application to transonic wings. Beginning with a brief review of the origins of the SCB concept, the primary focus is on the more recent studies from the last decade. Results from both experimental and numerical work are considered and the synergy between these two approaches to SCB research is critically explored. It is shown that the aerodynamic performance enhancement potential of SCBs, namely their capacity for drag reduction and delaying the onset of buffet for transonic wings, has been widely demonstrated in the literature, as has the high sensitivity of SCB performance to flow conditions including shock strength and position, and post-shock adverse pressure gradient. These characteristic features of SCBs are relatively well explained in terms of the flow physics that have been observed for different bump geometries. This stems from a number of studies that have focused on the balance of viscous and inviscid flow features and also the mechanism by which finite span SCBs generate streamwise vorticity. It is concluded that our understanding of SCBs is reaching an advanced level of maturity for SCBs in simple configurations and steady flow fields. However, SCB performance in unsteady flow and on swept wings requires further investigation before the concept can be considered a viable candidate for transonic wings. These investigations should adopt a multi-disciplinary approach combining carefully designed experiments and targeted computations. Finally, two concepts for future SCB research are suggested: the adaptive SCB and SCBs in engine intakes.

  7. Shock wave interaction with turbulence: Pseudospectral simulations

    SciTech Connect

    Buckingham, A.C.

    1986-12-30

    Shock waves amplify pre-existing turbulence. Shock tube and shock wave boundary layer interaction experiments provide qualitative confirmation. However, shock pressure, temperature, and rapid transit complicate direct measurement. Computational simulations supplement the experimental data base and help isolate the mechanisms responsible. Simulations and experiments, particularly under reflected shock wave conditions, significantly influence material mixing. In these pseudospectral Navier-Stokes simulations the shock wave is treated as either a moving (tracked or fitted) domain boundary. The simulations assist development of code mix models. Shock Mach number and pre-existing turbulence intensity initially emerge as key parameters. 20 refs., 8 figs.

  8. Implications of pressure diffusion for shock waves

    NASA Technical Reports Server (NTRS)

    Ram, Ram Bachan

    1989-01-01

    The report deals with the possible implications of pressure diffusion for shocks in one dimensional traveling waves in an ideal gas. From this new hypothesis all aspects of such shocks can be calculated except shock thickness. Unlike conventional shock theory, the concept of entropy is not needed or used. Our analysis shows that temperature rises near a shock, which is of course an experimental fact; however, it also predicts that very close to a shock, density increases faster than pressure. In other words, a shock itself is cold.

  9. The Diffusive Shock Acceleration Myth

    NASA Astrophysics Data System (ADS)

    Gloeckler, G.; Fisk, L. A.

    2012-12-01

    It is generally accepted that diffusive shock acceleration (DSA) is the dominant mechanism for particle acceleration at shocks. This is despite the overwhelming observational evidence that is contrary to predictions of DSA models. For example, our most recent survey of hourly-averaged, spin-averaged proton distribution functions around 61 locally observed shocks in 2001 at 1 AU found that in 21 cases no particles were accelerated. Spectral indices (γ ) of suprathermal tails on the velocity distributions around the 40 shocks that did accelerate particles, showed none of the DSA-predicted correlations of γ with the shock compression ratio and the shock normal to magnetic field angle. Here we will present ACE/SWICS observations of three sets of 72 consecutive one-hour averaged velocity distributions (in each of 8 SWICS spin sectors). Each set includes passage of one or more shocks or strong compression regions. All spectra were properly transformed to the solar wind frame using the detailed, updated SWICS forward model, taking into account the hourly-averaged directions of the solar wind flow, the magnetic field and the ACE spin axis (http://www.srl.caltech.edu/ACE/ASC/). The suprathermal tails are observed to be a combination of locally accelerated and remote tails. The local tails are power laws. The remote tails are also power laws with rollovers at higher energies. When local tails are weak (as is the case especially upstream of strong shocks or compression regions) the remote tails also have a rollover at low energies due to modulation (transport effects). Among our main findings are that (1) the spectral indices of both the local and remote tails are -5 within the uncertainties of the measurements, as predicted by our pump acceleration mechanism, and (2) the velocity distributions are anisotropic with the perpendicular (to the magnetic field) pressure greater than the parallel pressure.

  10. Shock compression of precompressed deuterium

    SciTech Connect

    Armstrong, M R; Crowhurst, J C; Zaug, J M; Bastea, S; Goncharov, A F; Militzer, B

    2011-07-31

    Here we report quasi-isentropic dynamic compression and thermodynamic characterization of solid, precompressed deuterium over an ultrafast time scale (< 100 ps) and a microscopic length scale (< 1 {micro}m). We further report a fast transition in shock wave compressed solid deuterium that is consistent with the ramp to shock transition, with a time scale of less than 10 ps. These results suggest that high-density dynamic compression of hydrogen may be possible on microscopic length scales.

  11. Shock metamorphism of granulated lunar basalt

    NASA Technical Reports Server (NTRS)

    Schaal, R. B.; Thompson, T. D.; Hoerz, F.; Bauer, J. F.

    1979-01-01

    The paper deals with an extensive series of shock-recovery experiments performed on both nonporous crystalline basalt and its granulated and sieved counterpart to study the role of porosity and grain size in shock motomorphic effects under otherwise identical conditions. Shocked samples are compared with unshocked starting material in terms of textural and mineralogical modifications attributable to shock. A comparative petrographic and chemical characterization is presented of pulverized and sieved lunar basalt 75035 shocked between 6 and 75 GPa in comparison with holocrystalline disks of the same basalts shocked in 10 earlier experiments. Specifically, a petrographic classification of shock features is given, along with an estimation of relative amounts of shock glasses and a chemical characterization of shock glasses in each shocked granular basalt.

  12. Turbulence in electrostatic ion acoustic shocks

    NASA Technical Reports Server (NTRS)

    Means, R. W.; Coroniti, F. V.; Wong, A. Y.; White, R. B.

    1973-01-01

    Three types of collisionless electrostatic ion acoustic shocks are investigated using a double plasma (DP) device: (1) laminar shocks; (2) small amplitude turbulent shocks in which the turbulence is confined to be upstream of the shock potential jump; and (3) large amplitude turbulent shocks in which the wave turbulence occurs throughout the shock transition. The wave turbulence is generated by ions which are reflected from the shock potential; linear theory spatial growth increments agree with experimental values. The experimental relationship between the shock Mach number and the shock potential is shown to be inconsistent with theoretical shock models which assume that the electrons are isothermal. Theoretical calculations which assume a trapped electron equation of a state and a turbulently flattened velocity distrubution function for the reflected ions yields a Mach number vs potential relationship in agreement with experiment.

  13. Mix and Instability Growth from Oblique Shock

    NASA Astrophysics Data System (ADS)

    Molitoris, John D.; Batteux, Jan D.; Garza, Raul G.; Tringe, Joseph W.; Souers, P. Clark; Energetic Materials Center Team

    2011-06-01

    We have studied the formation and evolution of shock-induced turbulent mix resulting from pre-emplaced interface features in a cylindrical geometry. In this research a solid cylindrical core of high-explosive was detonated to create an oblique shock wave that is driven through a cylindrical interface. Pre-emplaced surface features in plastic and aluminum were studied. Time sequence radiographic imaging was utilized to observe the resulting instability formation from the growth phase to onset of mix and turbulence. Different types of pre-emplaced structures at the interface resulted in a range of mix and instability conditions, with some much more effective at creating a well-mixed region. The plastic used here was porous polyethylene. Interfaces studied were between the high-explosive/aluminum, aluminum/plastic, and finally plastic/air. Radiographic image data will be compared with numerical simulations of the experiments. Partial support for this research was obtained from the Advanced Energetics Program, Defense Threat Reduction Agency. This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. Shock Tunnel Studies of Scramjet Phenomena 1993

    NASA Technical Reports Server (NTRS)

    Stalker, R. J.; Bakos, R. J.; Morgan, R. G.; Porter, L.; Mee, D.; Paull, A.; Tuttle, S.; Simmons, J. M.; Wendt, M.; Skinner, K.

    1995-01-01

    Reports by the staff of the University of Queensland on various research studies related to the advancement of scramjet technology and hypervelocity pulse test facilities are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation. This research activity is Supplement 10 under NASA Grant NAGw-674.

  15. The microphysics of collisionless shocks

    NASA Astrophysics Data System (ADS)

    Wilson, Lynn Bruce, III

    2010-11-01

    Shock waves in interplanetary (IP) space are of considerable interest due to their potential to damage ground based electronic systems and their ability to energize charged particles. The energization of charged particles at IP shocks has the obvious extrapolation to supernova shock waves, which are thought to be a candidate for generating the most energetic particles in the universe. The observations and theory behind collisionless shock wave evolution suggest that IP shocks should, for the most part, be stable structures which require energy dissipation. In a regular fluid, like our atmosphere, energy dissipation is accomplished through binary particle collisions transferring the loss of bulk flow kinetic energy to heat. Plasmas are mostly collisionless fluids, thus requiring other means by which to dissipate energy. The studies herein were performed using wave and particle data primarily from the Wind spacecraft to investigate the microphysics of IP shock energy dissipation mechanisms. Due to their lower Mach numbers, more simplified geometry, and quasi-perpendicular nature, IP shock waves are an excellent laboratory to study wave-particle related dissipation mechanisms. Utilization of multiple data sets from multiple high time resolution instruments on board the Wind spacecraft, we have performed studies on the transition region microphysics of IP shocks. The work began with a statistical study of high frequency (≥ 1 kHz) waveform capture data during 67 IP shocks with Mach numbers ranging from ∼1-6 found ion-acoustic wave amplitudes correlated with the fast mode Mach number and shock strength. The ion-acoustic waves (IAWs) were estimated to produce anomalous resistivities roughly seven orders of magnitude above classical estimates. Another study was an examination of low frequency waves (0.25 Hz < f < 10 Hz) at five quasi-perpendicular IP shocks found the wave modes to be consistent with oblique precusor whistler waves at four of the events. The strongest

  16. Characteristics of unsteady type IV shock/shock interaction

    NASA Astrophysics Data System (ADS)

    Chu, Y.-B.; Lu, X.-Y.

    2012-05-01

    Characteristics of the unsteady type IV shock/shock interaction of hypersonic blunt body flows are investigated by solving the Navier-Stokes equations with high-order numerical methods. The intrinsic relations of flow structures to shear, compression, and heating processes are studied and the physical mechanisms of the unsteady flow evolution are revealed. It is found that the instantaneous surface-heating peak is caused by the fluid in the "hot spot" generated by an oscillating and deforming jet bow shock (JBS) just ahead of the body surface. The features of local shock/boundary layer interaction and vortex/boundary layer interaction are clarified. Based on the analysis of flow evolution, it is identified that the upstream-propagating compression waves are associated with the interaction of the JBS and the shear layers formed by a supersonic impinging jet, and then the interaction of the freestream bow shocks and the compression waves results in entropy and vortical waves propagating to the body surface. Further, the feedback mechanism of the inherent unsteadiness of the flow field is revealed to be related to the impinging jet. A feedback model is proposed to reliably predict the dominant frequency of flow evolution. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to this complex flow.

  17. Shock Tunnel Studies of Scramjet Phenomena 1995. Supplement 13

    NASA Technical Reports Server (NTRS)

    Morgan, R. G.; Stalker, R. J.; Paull, A.

    1997-01-01

    Reports by the research staff and graduate students of the Mechanical Engineering Department at the University of Queensland are collected and presented. These reports cover various studies related to the advancement of scramjet technology and the operation of advanced hypervelocity shock-expansion tubes. The report topics include the experimental studies of mixing and combustion in a scramjet flow path, the measurement of integrated thrust and skin friction, and the development of a free-piston-driven expansion tunnel capable delivering a test gas at super orbital velocities.

  18. Interaction of interplanetary shocks and rotational discontinuities with the Earth`s bow shock

    SciTech Connect

    Yan, M.; Lee, L.C.

    1996-03-01

    The magnetohydrodynamic (MHD) aspects of the interaction between the Earth`s bow show and interplanetary shocks or rotational discontinues are systematically studied in this paper by MHD simulations. The interplanetary shocks under consideration include forward fast shocks, reverse fast shocks, forward slow shocks, and a reverse slow shocks. As an incident forward shock transmits through the bow shock, a fast shock, a slow expansion wave, a slow shock, and a contact discontinuity are generated downstream of the bow shock. At the same time, the bow shock is modified and moves earthward. If the incident shock is a reverse shock, the generated fast shock becomes a fast expansion wave, and the bow shock moves away from the earth. The generated fast shock or fast expansion wave carries most of the total pressure variation. The contact discontinuity also carries a significant part of the pressure variation. The slow expansion wave and the slow shock are both generated with a small variation in plasma density and pressure but a large variation in magnetic field. When the solar wind Alfven Mach number is small, the density variations associated with the slow shock or slow expansion wave can be significant. Through the interaction between an incident rotational discontinuity and the bow shock, a plateau in the plasma density and thermal pressure is formed. The magnetic pressure is depressed accordingly anticorrelated with the thermal pressure. If the incident rotational discontinuity proprogates toward the Earth (Sun) in the solar wind frame, the leading (trailing) edge of the plateau consists of an intermediate shock or a time-dependent intermediate shock and a slow shock, while the trailing (leading) edge is mainly a slow shock. The generated structure with enhanced plasma density and thermal pressure and a depressed magnetic pressure agrees very well with the observed slow-mode structure in the magnetosheath. 45 refs., 12 fig.

  19. The History of the APS Shock Compression of Condensed Matter Topical Group

    SciTech Connect

    Forbes, J W

    2001-05-02

    In order to provide broader scientific recognition and to advance the science of shock compressed condensed matter, a group of American Physical Society (APS) members worked within the Society to make this field an active part of the APS. Individual papers were presented at APS meetings starting in the 1940's and shock wave sessions were organized starting with the 1967 Pasadena meeting. Shock wave topical conferences began in 1979 in Pullman, WA. Signatures were obtained on a petition in 1984 from a balanced cross-section of the shock wave community to form an APS Topical Group (TG). The APS Council officially accepted the formation of the Shock Compression of Condensed Matter (SCCM) TG at its October 1984 meeting. This action firmly aligned the shock wave field with a major physical science organization. Most early topical conferences were sanctioned by the APS while those held after 1992 were official APS meetings. The topical group organizes a shock wave topical conference in odd numbered years while participating in shock wave/high pressure sessions at APS general meetings in even numbered years.

  20. History of the APS Topical Group on Shock Compression of Condensed Matter

    SciTech Connect

    Forbes, J W

    2001-10-19

    In order to provide broader scientific recognition and to advance the science of shock compressed condensed matter, a group of American Physical Society (APS) members worked within the Society to make this field an active part of the APS. Individual papers were presented at APS meetings starting in the 1940's and shock wave sessions were organized starting with the 1967 Pasadena meeting. Shock wave topical conferences began in 1979 in Pullman, WA. Signatures were obtained on a petition in 1984 from a balanced cross-section of the shock wave community to form an APS Topical Group (TG). The APS Council officially accepted the formation of the Shock Compression of Condensed Matter (SCCM) TG at its October 1984 meeting. This action firmly aligned the shock wave field with a major physical science organization. Most early topical conferences were sanctioned by the APS while those held after 1992 were official APS meetings. The topical group organizes a shock wave topical conference in odd numbered years while participating in shock wavehigh pressure sessions at APS general meetings in even numbered years.

  1. Pseudo-shock waves and their interactions in high-speed intakes

    NASA Astrophysics Data System (ADS)

    Gnani, F.; Zare-Behtash, H.; Kontis, K.

    2016-04-01

    In an air-breathing engine the flow deceleration from supersonic to subsonic conditions takes places inside the isolator through a gradual compression consisting of a series of shock waves. The wave system, referred to as a pseudo-shock wave or shock train, establishes the combustion chamber entrance conditions, and therefore influences the performance of the entire propulsion system. The characteristics of the pseudo-shock depend on a number of variables which make this flow phenomenon particularly challenging to be analysed. Difficulties in experimentally obtaining accurate flow quantities at high speeds and discrepancies of numerical approaches with measured data have been readily reported. Understanding the flow physics in the presence of the interaction of numerous shock waves with the boundary layer in internal flows is essential to developing methods and control strategies. To counteract the negative effects of shock wave/boundary layer interactions, which are responsible for the engine unstart process, multiple flow control methodologies have been proposed. Improved analytical models, advanced experimental methodologies and numerical simulations have allowed a more in-depth analysis of the flow physics. The present paper aims to bring together the main results, on the shock train structure and its associated phenomena inside isolators, studied using the aforementioned tools. Several promising flow control techniques that have more recently been applied to manipulate the shock wave/boundary layer interaction are also examined in this review.

  2. Properties of shocked polymers : Mbar experiments on Z and multi-scale simulations.

    SciTech Connect

    Mattsson, Thomas Kjell Rene

    2010-03-01

    Significant progress has been made over the last few years in understanding properties of matter subject to strong shocks and other extreme conditions. High-accuracy multi-Mbar experiments and first-principles theoretical studies together provide detailed insights into the physics and chemistry of high energy-density matter. While comprehensive advances have been made for pure elements like deuterium, helium, and carbon, progress has been slower for equally important, albeit more challenging, materials like molecular crystals, polymers, and foams. Hydrocarbon based polymer foams are common materials and in particular they are used in designing shock- and inertial confinement fusion experiments. Depending on their initial density, foams shock to relatively higher pressure and temperature compared to shocked dense polymers/plastics. As foams and polymers are shocked, they exhibit both structural and chemical transitions. We will present experimental and theoretical results for shocked polymers in the Mbar regime. By shock impact of magnetically launched flyer plates on poly(4-methyl-1-pentene) foams, we create multi-Mbar pressures in a dense plasma mixture of hydrogen, carbon, at temperatures of several eV. Concurrently with executing experiments, we analyze the system by multi-scale simulations, from density functional theory to continuum magneto-hydrodynamics simulations. In particular, density functional theory (DFT) molecular dynamics (MD) and classical MD simulations of the principal shock Hugoniot will be presented in detail for two hydrocarbon polymers: polyethylene (PE) and poly(4-methyl-1-pentene) (PMP).

  3. Whole-spacecraft shock isolation system

    NASA Astrophysics Data System (ADS)

    Johnson, Conor D.; Wilke, Paul S.

    2002-06-01

    Spacecraft are subjected to shock loads in the several thousands of g's level during their trip to orbit. These high shock loads usually result from some separation event, such as staging, spacecraft separation, and fairing separation. Shock loads are very detrimental to spacecraft components, instruments and electronics. A new type of shock isolation system is discussed. This shock system, referred to as the SoftRide ShockRing, is a whole-spacecraft isolation system, i.e., it shock isolates the complete spacecraft from the launch vehicle. Seven whole-spacecraft vibration isolation systems (SoftRide) have flown to date and flight data confirms large reductions of the dynamic loads on the spacecraft. The standard SoftRide system is a lower frequency isolation system than the ShockRing, vibration isolating the spacecraft starting in the approximately 25 Hz range. The ShockRing is targeted at shock loads and is set to isolate above approximately 75 Hz. Component tests have been performed on the ShockRing using a specially built pneumatic gun that can generate 10,000 g's on the test article. Results from these tests demonstrate substantial reductions of the shock being transmitted to the payload. Results from a system test consisting of a spacecraft simulator, payload attachment fittings, avionics section, and shock plate are discussed. In the system tests, pyrotechnic devices were used to obtain the high levels of shock for the tests.

  4. Shock Compression of Liquid Hydrazine.

    NASA Astrophysics Data System (ADS)

    Voskoboinikov, I. M.

    1999-06-01

    The possibility of calculation of the parameters of a shock compression of liquid hydrazine within the frameworks of the schemes is shown. When the mass velocities behind shock fronts do not exceed the value equals 3.1 km/s, it may be managed under assumption of the retention of the initial compound (hydrazine) behind a shock front. The detonation velocities of hydrazine solutions with nitromethane and hydrazinenitrate correspond to the destruction of hydrazine up to ammonia and nitrogen that is accompanied by a noticeable energy release. The estimates performed demonstrate a possibility of the detonation of a liquid hydrazine with the velocity equals 8 km/s, during which the heating up of the substance behind a shock front (equals approximately 2000 K) is comparable with those observed during detonation of liquid explosives. The large values of the critical diameter of detonation are expected because of activation energy of hydrazine decomposition equals 53.2 kcal/mol. They are decreased up on addition of a certain amount of liquid explosives. Their more rapid decomposition behind a shock front gives rise to the temperature increase that is sufficient for destruction of hydrazine.

  5. Vorticity production in shock diffraction

    NASA Astrophysics Data System (ADS)

    Sun, M.; Takayama, K.

    2003-03-01

    The production of vorticity or circulation production in shock wave diffraction over sharp convex corners has been numerically simulated and quantified. The corner angle is varied from 5° to 180°. Total vorticity is represented by the circulation, which is evaluated by integrating the velocity along a path enclosing the perturbed region behind a diffracting shock wave. The increase of circulation in unit time, or the rate of circulation production, depends on the shock strength and wall angle if the effects of viscosity and heat conductivity are neglected. The rate of vorticity production is determined by using a solution-adaptive code, which solves the Euler equations. It is shown that the rate of vorticity production is independent of the computational mesh and numerical scheme by comparing solutions from two different codes. It is found that larger wall angles always enhance the vorticity production. The vorticity production increases sharply when the corner angle is varied from 15° to 45°. However, for corner angles over 90°, the rate of vorticity production hardly increases and reaches to a constant value. Strong shock waves produce vorticity faster in general, except when the slipstream originating from the shallow corner attaches to the downstream wall. It is found that the vorticity produced by the slipstream represents a large proportion of the total vorticity. The slipstream is therefore a more important source of vorticity than baroclinic effects in shock diffraction.

  6. Transient shocks beyond the heliopause

    NASA Astrophysics Data System (ADS)

    Fermo, R. L.; Pogorelov, N. V.; Burlaga, L. F.

    2015-09-01

    The heliopause is a rich, dynamic surface affected by the time-dependent solar wind. Stream interactions due to coronal mass ejections (CMEs), corotating interaction regions (CIRs), and other transient phenomena are known to merge producing global merged interaction regions (GMIRs). Numerical simulations of the solar wind interaction with the local interstellar medium (LISM) show that GMIRs, as well other time-dependent structures in the solar wind, may produce compression/rarefaction waves and shocks in the LISM behind the heliopause. These shocks may initiate wave activity observed by the Voyager spacecraft. The magnetometer onboard Voyager 1 indeed observed a few structures that may be interpreted as shocks. We present numerical simulations of such shocks in the year of 2000, when both Voyager spacecraft were in the supersonic solar wind region, and in 2012, when Voyager 1 observed traveling shocks. In the former case, Voyager observations themselves provide time- dependent boundary conditions in the solar wind. In the latter case, we use OMNI data at 1 AU to analyze the plasma and magnetic field behavior after Voyager 1 crossed the heliospheric boundary. Numerical results are compared with spacecraft observations.

  7. Shock compression of liquid hydrazine

    SciTech Connect

    Garcia, B.O.; Chavez, D.J.

    1995-01-01

    Liquid hydrazine (N{sub 2}H{sub 4}) is a propellant used by the Air Force and NASA for aerospace propulsion and power systems. Because the propellant modules that contain the hydrazine can be subject to debris impacts during their use, the shock states that can occur in the hydrazine need to be characterized to safely predict its response. Several shock compression experiments have been conducted in an attempt to investigate the detonability of liquid hydrazine; however, the experiments results disagree. Therefore, in this study, we reproduced each experiment numerically to evaluate in detail the shock wave profiles generated in the liquid hydrazine. This paper presents the results of each numerical simulation and compares the results to those obtained in experiment. We also present the methodology of our approach, which includes chemical kinetic experiments, chemical equilibrium calculations, and characterization of the equation of state of liquid hydrazine.

  8. Deionization shocks in cross flows

    NASA Astrophysics Data System (ADS)

    Mani, Ali

    2011-11-01

    Recent experimental and theoretical studies have shown that surface conduction in supported electrolytes, such as in micro/nanochannels or porous media, can lead to nonlinear modes of transport and formation of sharp concentration fronts analogous to shock waves in gas dynamics. Propagation of these shocks leaves behind a region of ultra pure fluid, acting to deionize the bulk solution. In this work we present the analysis of salt transport in a porous medium next to a membrane with an electric field applied normal to the interface and cross flow in tangential direction. We show that two distinct boundary layers grow near the membrane: an inner (shocked) region with almost deionized solution dominated by surface conduction, and an outer layer with diffuse dynamics. Under certain conditions both regions collapse into a similarity solution with the same scaling. We will discuss advantages of such systems for desalination and water purification. Research performed in collaboration with Martin Bazant (MIT).

  9. Efficient particle acceleration in shocks

    NASA Astrophysics Data System (ADS)

    Heavens, A. F.

    1984-10-01

    A self-consistent non-linear theory of acceleration of particles by shock waves is developed, using an extension of the two-fluid hydrodynamical model by Drury and Völk. The transport of the accelerated particles is governed by a diffusion coefficient which is initially assumed to be independent of particle momentum, to obtain exact solutions for the spectrum. It is found that steady-state shock structures with high acceleration efficiency are only possible for shocks with Mach numbers less than about 12. A more realistic diffusion coefficient is then considered, and this maximum Mach number is reduced to about 6. The efficiency of the acceleration process determines the relative importance of the non-relativistic and relativistic particles in the distribution of accelerated particles, and this determines the effective specific heat ratio.

  10. Cardiogenic shock in a neonate

    PubMed Central

    Viveiros, Eulália; Aveiro, Ana Cristina; Costa, Edite; Nunes, José Luis

    2013-01-01

    We describe a case of a healthy male full-term neonate, 21 days old, admitted to the emergency room, presenting a severe cardiovascular collapse with an initial sinus rhythm. The first diagnostic hypothesis was of septic shock, having antibiotics, fluid resuscitation, inotropic drugs and ventilatory support started immediately. After achieving haemodynamic stability, a new cardiovascular collapse occurred with supraventricular tachycardia (SVT). The latter was successfully treated and the neonate did not suffer any organ damage. Cardiogenic shock should be considered despite being a much rarer cause of shock in neonates. SVT is promptly diagnosed when a cardiorespiratory monitor is available; however, the intermittent occurrence of the tachycardia episodes makes this diagnosis more difficult to recognise and manage. PMID:23737567

  11. Strong shock implosion, approximate solution

    NASA Astrophysics Data System (ADS)

    Fujimoto, Y.; Mishkin, E. A.; Alejaldre, C.

    1983-01-01

    The self-similar, center-bound motion of a strong spherical, or cylindrical, shock wave moving through an ideal gas with a constant, γ= cp/ cv, is considered and a linearized, approximate solution is derived. An X, Y phase plane of the self-similar solution is defined and the representative curved of the system behind the shock front is replaced by a straight line connecting the mappings of the shock front with that of its tail. The reduced pressure P(ξ), density R(ξ) and velocity U1(ξ) are found in closed, quite accurate, form. Comparison with numerically obtained results, for γ= {5}/{3} and γ= {7}/{5}, is shown.

  12. Shock Hugoniot Measurements in Foam

    NASA Astrophysics Data System (ADS)

    Petel, Oren; Ouellet, Simon; Frost, David; Higgins, Andrew

    2013-06-01

    Foams are found in a variety of protective equipment, including those used in applications involving high-speed impact and blast waves. Despite their exposure to shock wave loadings, there is a considerable lack of shock Hugoniot data for these materials. Typical characterizations of foams have involved the use of split-Hopkinson pressure bars or quasi-static compression machines to determine the stress-strain relationship in the foams. As such, the elastic-plastic response of foam at intermediate pressure ranges continues to be a source of confusion. In the present study, Photonic Doppler Velocimetry is used to measure the shock Hugoniot of a foam for a comparison to its quasi-static compression curves. The deviation of these two curves will be discussed and compared to common plasticity models used to describe dynamic foam behaviour in the literature.

  13. Gamma Rays from Intergalactic Shocks

    NASA Astrophysics Data System (ADS)

    Keshet, Uri; Waxman, Eli; Loeb, Abraham; Springel, Volker; Hernquist, Lars

    2003-03-01

    Structure formation in the intergalactic medium (IGM) produces large-scale, collisionless shock waves, in which electrons can be accelerated to highly relativistic energies. Such electrons can Compton-scatter cosmic microwave background photons up to γ-ray energies. We study the radiation emitted in this process using a hydrodynamic cosmological simulation of a ΛCDM universe. The resulting radiation, extending beyond TeV energies, has roughly constant energy flux per decade in photon energy, in agreement with the predictions of Loeb & Waxman. Assuming that a fraction ξe=0.05 of the shock thermal energy is transferred to the population of accelerated relativistic electrons, as inferred from collisionless nonrelativistic shocks in the interstellar medium, we find that the energy flux of this radiation, ɛ2(dJ/dɛ)~=50-160 eV cm-2 s-1 sr-1, constitutes ~10% of the extragalactic γ-ray background flux. The associated γ-ray point sources are too faint to account for the ~60 unidentified EGRET γ-ray sources, but GLAST should detect and resolve several γ-ray sources associated with large-scale IGM structures for ξe~=0.03 and many more sources for larger ξe. The intergalactic origin of the shock-induced radiation can be verified through a cross-correlation with, e.g., the galaxy distribution that traces the same structure. Its shock origin may be tested by cross-correlating its properties with radio synchrotron radiation, emitted as the same accelerated electrons gyrate in postshock magnetic fields. We predict that GLAST and Cerenkov telescopes such as MAGIC, VERITAS, and HESS should resolve γ-rays from nearby (redshifts z<~0.01) rich galaxy clusters, perhaps in the form of a ~5-10 Mpc diameter ringlike emission tracing the cluster accretion shock, with luminous peaks where the ring intersects galaxy filaments detectable even at z~=0.025.

  14. Shock Initiation of Damaged Explosives

    SciTech Connect

    Chidester, S K; Vandersall, K S; Tarver, C M

    2009-10-22

    Explosive and propellant charges are subjected to various mechanical and thermal insults that can increase their sensitivity over the course of their lifetimes. To quantify this effect, shock initiation experiments were performed on mechanically and thermally damaged LX-04 (85% HMX, 15% Viton by weight) and PBX 9502 (95% TATB, 5% Kel-F by weight) to obtain in-situ manganin pressure gauge data and run distances to detonation at various shock pressures. We report the behavior of the HMX-based explosive LX-04 that was damaged mechanically by applying a compressive load of 600 psi for 20,000 cycles, thus creating many small narrow cracks, or by cutting wedge shaped parts that were then loosely reassembled, thus creating a few large cracks. The thermally damaged LX-04 charges were heated to 190 C for long enough for the beta to delta solid - solid phase transition to occur, and then cooled to ambient temperature. Mechanically damaged LX-04 exhibited only slightly increased shock sensitivity, while thermally damaged LX-04 was much more shock sensitive. Similarly, the insensitive explosive PBX 9502 was mechanically damaged using the same two techniques. Since PBX 9502 does not undergo a solid - solid phase transition but does undergo irreversible or 'rachet' growth when thermally cycled, thermal damage to PBX 9502 was induced by this procedure. As for LX-04, the thermally damaged PBX 9502 demonstrated a greater shock sensitivity than mechanically damaged PBX 9502. The Ignition and Growth reactive flow model calculated the increased sensitivities by igniting more damaged LX-04 and PBX 9502 near the shock front based on the measured densities (porosities) of the damaged charges.

  15. Propagation of a curved weak shock

    NASA Astrophysics Data System (ADS)

    Monica, A.; Prasad, Phoolan

    2001-05-01

    Propagation of a curved shock is governed by a system of shock ray equations which is coupled to an infinite system of transport equations along these rays. For a two-dimensional weak shock, it has been suggested that this system can be approximated by a hyperbolic system of four partial differential equations in a ray coordinate system, which consists of two independent variables ([zeta], t) where the curves t = constant give successive positions of the shock and [zeta] = constant give rays. The equations show that shock rays not only stretch longitudinally due to finite amplitude on a shock front but also turn due to a non-uniform distribution of the shock strength on it. These changes finally lead to a modification of the amplitude of the shock strength. Since discontinuities in the form of kinks appear on the shock, it is necessary to study the problem by using the correct conservation form of these equations. We use such a system of equations in conservation form to construct a total-variation-bounded finite difference scheme. The numerical solution captures converging shock fronts with a pair of kinks on them the shock front emerges without the usual folds in the caustic region. The shock strength, even when the shock passes through the caustic region, remains so small that the small-amplitude theory remains valid. The shock strength ultimately decays with a well-defined geometrical shape of the shock front a pair of kinks which separate a central disc from a pair of wings on the two sides. We also study the ultimate shape and decay of shocks of initially periodic shapes and plane shocks with a dent and a bulge.

  16. Electron acceleration in a wavy shock front

    NASA Astrophysics Data System (ADS)

    Vandas, M.; Karlický, M.

    2011-07-01

    Context. It is known that electrons are accelerated at nearly perpendicular shocks by the drift mechanism. And it is also known that energy gain of electrons caused by this mechanism is not very high. Therefore it was suggested in the past that the energy gain might be increased if shocks had wavy fronts. For instance, there were attempts to explain coronal type II burst and their fine structure by electron acceleration in a wavy shock front. Aims: We studied electron acceleration numerically at nearly perpendicular wavy shocks for coronal conditions and compared it with analytical results on electron acceleration at nearly perpendicular plane shocks. Methods: An analytical model of a wavy shock front was used and trajectories of electrons in it and around it were calculated numerically in a guiding centre approximation. Results: We found that energy gains of electrons at a wavy shock front and a corresponding smoothed-into-plane shock on the average were comparable. That is why they do not depend significantly on the shock thickness, magnetic field profile inside the shock, and shock wavy form. They do depend on the angle between the smoothed shock front and ambient magnetic field. Conclusions: On average, a wavy shock front does not significantly increase an acceleration efficiency. Energy gain remarkably exceeds an average level for some combinations of initial parameters. Distribution functions of accelerated electrons have a patchy structure, which is prone to inducing plasma instabilities that will generate plasma waves. This may have relevance to the problem of type II burst origin.

  17. Observations of the termination shock and heliosheath

    NASA Astrophysics Data System (ADS)

    Richardson, J. D.

    2013-05-01

    The termination shock was crossed by Voyager 1 in 2004 and by Voyager 2 in 2007. This paper will review the observations at the shock and describe what observations in the heliosheath teach us about this shock. The termination shock presented several surprises. The speed decrease began 60 days in front of the ramp region, suggesting the shock was mediated by energetic particles. The thermal plasma downstream of the shock was still supersonic which allowed us to infer that most of the energy from the bulk flow went into the pickup ions. The ACRs were not accelerated where the Voyagers crossed the shock, so the ACR source must be in the flanks of the shock or elsewhere than the shock. The shock was a good accelerator of few MeV ions, the termination shock particles. Subsequent measurements of flow in the heliosheath suggest that the shock is compressed at the southern pole giving a shock which is blunter in the azimuthal than meridional direction. A recent sharp drop in the energetic particle fluxes may tell us the width of the flank region.

  18. Supercriticality of ICME and CIR shocks

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoyan; Smith, Edward J.

    2015-03-01

    Interplanetary coronal mass ejection (ICME) and corotating interaction region (CIR) shocks are characterized in terms of supercriticality introduced by Edmiston and Kennel (1984) to classify shocks based on whether dissipation is provided by electron resistivity alone or also requires ion viscosity. The condition for determining supercriticality is a critical Mach number, MC, a function of θBn, the angle between the upstream magnetic field, B, and the normal to the shock surface, n, and β, the ratio of the plasma and magnetic pressures. The criterion was subsequently revised by Kennel (1987) to include dissipation by electron thermal as well as electrical conductivity. Two early separate studies of ICME and CIR shocks motivated our investigation that included several improvements. We use Kennel (1987) and shocks identified by WIND near 1 AU and by Ulysses near 5 AU from the same solar cycle to provide Occurrence Probability Distributions and statistical information for all parameters. We answer three questions (1) Is the supercriticality of ICME and CIR shocks different? (2) If so, why? (3) Does the latter MC criterion change the answers? Our conclusions are (1) about two thirds of CIR shocks are supercritical as compared to one third of ICME shocks, (2) although ICME shock speeds are typically higher than CIR shocks, the fast-mode wave speeds are even higher at 1 AU than that of CIR shocks at ~5 AU causing a reduction in Mach numbers, and (3) CIR shocks are also more supercritical than ICME shocks using both criteria with slight differences.

  19. Effects Of Pyrotechnically Generated Shocks

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.; Evans, Maria J.; Neubert, Vernon H.

    1989-01-01

    Research program provides better understanding of pyrotechnic phenomenon for design purposes. Evaluating potential for damage to spacecraft by activation of pyrotechnic mechanisms, pyrotechnic-shock tests conducted on three configurations: pin pullers on orthogonal double Hopkinson bar arrangement; pin pullers on mockup of Halogen Occultation Experiment (HALOE) structure; and section of separation joint on single Hopkinson bar. Strains and accelerations measured. Strains converted to output stresses, forces, and moments. Acceleration shock-response spectra obtained for both acceleration and force signals. Results of research useful to designers in making comparison and evaluation tests before committing to costly spacecraft hardware.

  20. Shocking Results About Exploding Stars

    NASA Astrophysics Data System (ADS)

    Piro, Anthony

    2016-06-01

    Early light curves of supernovae are dominated by the emission of surface material that has been heated and ejected by the supernova shock. Studying this shock cooling can provide unique constraints on the radius of the progenitor, which is important for comparisons to stellar modeling, populations of massive stars, and pre-explosion imaging. Here I summarize both numerical and semi-analytic work to model this phase and apply it to current and future observations. I discuss a wide range of events, from the fairly common Type IIP supernovae to the exotic Type I superluminous supernovae for which their exact progenitors are still elusive.

  1. Shock-induced crystalline instabilities

    NASA Astrophysics Data System (ADS)

    Ravelo, Ramon; Holian, Brad Lee; Germann, Timothy C.

    2007-03-01

    Uniaxial deformations of single crystals such as those produced under planar shock loading can produce structural instabilities which compete with defect nucleation mechanisms. In fcc single crystals under (110) shock loading, the resulting body-centered orthorhombic crystal structure develops a long-wavelength dynamical instability associated with tetragonal shear distortions, which occurs at lower strains (pressures) than those predicted by the vanishing of the elastic constants at finite pressure (stiffness coefficients). The criterion for these instabilities is derived and verified by equilibrium and non-equilibrium molecular dynamics simulations [2]J. Wang, S. Yip, S.R. Phillpot, D. Wolf, Phys. Rev. Lett. 71, 4182 (1993)

  2. Multi-scale Shock Technique

    2009-08-01

    The code to be released is a new addition to the LAMMPS molecular dynamics code. LAMMPS is developed and maintained by Sandia, is publicly available, and is used widely by both natioanl laboratories and academics. The new addition to be released enables LAMMPS to perform molecular dynamics simulations of shock waves using the Multi-scale Shock Simulation Technique (MSST) which we have developed and has been previously published. This technique enables molecular dynamics simulations of shockmore » waves in materials for orders of magnitude longer timescales than the direct, commonly employed approach.« less

  3. Shock compaction of molybdenum powder

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.; Kostka, D.; Vreeland, T., Jr.; Schwarz, R. B.; Kasiraj, P.

    1983-01-01

    Shock recovery experiments which were carried out in the 9 to 12 GPa range on 1.4 distension Mo and appear adequate to compact to full density ( 45 (SIGMA)m) powders were examined. The stress levels, however, are below those calculated to be from 100 to approx. 22 GPa which a frictional heating model predicts are required to consolidate approx. 10 to 50 (SIGMA)m particles. The model predicts that powders that have a distension of m=1.6 shock pressures of 14 to 72 GPa are required to consolidate Mo powders in the 50 to 10 (SIGMA)m range.

  4. Method of making shock cells

    SciTech Connect

    Leblanc, R. F.; Cummins, W. T.

    1984-10-16

    A method of making an energy-absorbing shock cell for mounting bumper devices on legs of offshore oil rig structures having inner and outer metal tubes connected by an intervening vulcanized rubber sleeve maintained under compression adhesively bonded to the inner and outer metal tubes. The shock cell is made by a series of operations in which portions of the metal tubes are coated with adhesive material, and the rubber sleeve is bonded to the adhesive coated areas by vulcanization and post-vulcanized heating.

  5. Rarefaction shock waves in shock-compressed diamond <110> crystal

    NASA Astrophysics Data System (ADS)

    Perriot, Romain; Lin, You; Zhakhovsky, Vasily; White, Carter; Oleynik, Ivan

    2013-03-01

    Piston-driven shock compression of diamond <110> crystal was simulated by molecular dynamics using the REBO potential. At piston velocities between 2 and 5 km/s and corresponding pressures 117 GPA < P < 278 GPa, diamond sample undergoes a polymorphic phase transition, characterized by the coexistence of two elastically compressed phases, low-pressure phase A and high-pressure phase B. This phase transition results in the splitting of the shock wave into two elastic shock waves, composed of pure phase A and a mixture of phases A and B. Upon removal of the piston, a release wave is observed at the rear of the sample, turning into a rarefaction shock wave where the material undergoes the reverse phase transition from coexisting phases to the original low-pressure phase. For strong plastic waves induced by larger piston velocities the release wave propagates as a rarefaction wave without any phase transition corresponding to the adiabatic expansion along the plastic branch of the Hugoniot.

  6. Spallation in starphire under normal shock and shock induced shear

    NASA Astrophysics Data System (ADS)

    Dandekar, Dattatraya

    2013-06-01

    Starphire is a brand name used by PPG Industries for their clear glass. Its composition primarily differs from that of soda lime glass /float glass in terms of low MgO and Fe2O3 content. The densities of soda lime glass and starphire are identical i.e., 2.49 Mg/m3. Their elastic constants similarly are also identical: Young's and shear modulus of soda lime glass and starphire are 73 GPa, and 29 GPa, respectively. Current work was undertaken to investigate the effect of normal shock compression and simultaneous shock compression and shear on the spall strength of starphire. Simultaneous compression-shear was generated at an obliquity of 14 degrees. Starphire was shocked to a maximum stress of 6 GPa. The preliminary results of experiments performed on starphire indicate that: (a) spall strength of starphire is not altered significantly when it is subjected to normal shock compression or simultaneous compression shear, and (b) spall strengths of starphire at a given stress is strongly dependent on compression pulse width.

  7. Swords to plowshares: Shock wave applications to advanced lithography

    SciTech Connect

    Trucano, T.G.; Grady, D.E.; Kubiak, G.D.; Kipp, M.E.; Olson, R.E.; Farnsworth, A.

    1995-03-01

    Extreme UltraViolet Lithography (EUVL) seeks to apply radiation in a wavelength region centered near 13 nm to produce microcircuits having features sizes 0.1 micron or less. A critical requirement for the commercial application of this technology is the development of an economical, compact source of this radiation which is suitable for lithographic applications. A good candidate is a laser-plasma source, which is generated by the interaction of an intermediate intensity laser pulse (up to 10{sup 12} W/cm{sup 2}) with a metallic target. While such a source has radiative characteristics which satisfy the needs of an EUVL source, the debris generated during the laser-target interaction strikes at the economy of the source. Here, the authors review the use of concepts and computer modeling, originally developed for hypervelocity impact analysis, to study this problem.

  8. Shock absorber operates over wide range

    NASA Technical Reports Server (NTRS)

    Creasy, W. K.; Jones, J. C.

    1965-01-01

    Piston-type hydraulic shock absorber, with a metered damping system, operates over a wide range of kinetic energy loading rates. It is used for absorbing shock and vibration on mounted machinery and heavy earth-moving equipment.

  9. Shock State of Itokawa Regolith Grains

    NASA Technical Reports Server (NTRS)

    Zolensky, M.; Nishiizumi, K.; Mikouchi, T.; Chan, Q. H. S.; Martinez, J.; Caffee, M.

    2014-01-01

    One of the fundamental aspects of any astromaterial is its shock history, since this factor elucidates critical historical events, and also because shock metamorphism can alter primary mineralogical and petrographic features, and reset chronologies.

  10. Fresh look at floating shock fitting

    NASA Technical Reports Server (NTRS)

    Hartwich, PETER-M.

    1990-01-01

    A fast implicit upwind procedure for the two-dimensional Euler equations is described that allows accurate computations of shocked flows on nonadapted meshes. Away from shocks, the second-order accurate upwinding is based on the split-coefficient-matrix (SCM) method. In the presence of shocks, the difference stencils are modified using a floating shock fitting technique. Rapid convergence to steady-state solutions is attained with a diagonalized approximate factorization (AF) algorithm. Results are presented for Riemann's problem, for a regular shock reflection at an inviscid wall, for supersonic flow past a cylinder, and for a transonic airfoil. All computed shocks are ideally sharp and in excellent agreement with other numerical results or 'exact' solutions. Most importantly, this has been accomplished on unusually crude meshes without any attempt to align grid lines with shock fronts or to cluster grid lines around shocks.

  11. "Driverless" Shocks in the Interplanetary Medium

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Kaiser, M. L.; Lara, A.

    1999-01-01

    Many interplanetary shocks have been detected without an obvious driver behind them. These shocks have been thought to be either blast waves from solar flares or shocks due to sudden increase in solar wind speed caused by interactions between large scale open and closed field lines of the Sun. We investigated this problem using a set of interplanetary shock detected {\\it in situ} by the Wind space craft and tracing their solar origins using low frequency radio data obtained by the Wind/WAVES experiment. For each of these "driverless shocks" we could find a unique coronal mass ejections (CME) event observed by the SOHO (Solar and Heliospheric Observatory) coronagraphs. We also found that these CMEs were ejected at large angles from the Sun-Earth line. It appears that the "driverless shocks" are actually driver shocks, but the drivers were not intercepted by the spacecraft. We conclude that the interplanetary shocks are much more extended than the driving CMEs.

  12. Noise transmission along shock-waves

    NASA Astrophysics Data System (ADS)

    Amur Varadarajan, Prasanna

    Shocks at the inlet of scramjet engines are subject to perturbations from their interaction with turbulent boundary layer. DNS results for this interaction indicate the presence of discrete vortices that interact with the shock at its foot. These studies reveal that the vortices cause oscillations of the shock. In this work we examine the propagation of disturbances along a stationary oblique shock following interaction with a two-dimensional vortex. We study the decay of disturbances along a normal shock as measured from Euler computations and compare these with the predictions of Geometrical Shock Dynamics (GSD) for long range propagation. We have incorporated two improvements into the GSD model to tackle the shock-vortex interaction problem. The wave structure of the disturbance resembles N waves, the decay of which follows a power law profile. An extension of the GSD model to predict shock surface propagation in 3-D flows is presented along with the numerical implementation.

  13. Kinetic Simulations of Particle Acceleration at Shocks

    SciTech Connect

    Caprioli, Damiano; Guo, Fan

    2015-07-16

    Collisionless shocks are mediated by collective electromagnetic interactions and are sources of non-thermal particles and emission. The full particle-in-cell approach and a hybrid approach are sketched, simulations of collisionless shocks are shown using a multicolor presentation. Results for SN 1006, a case involving ion acceleration and B field amplification where the shock is parallel, are shown. Electron acceleration takes place in planetary bow shocks and galaxy clusters. It is concluded that acceleration at shocks can be efficient: >15%; CRs amplify B field via streaming instability; ion DSA is efficient at parallel, strong shocks; ions are injected via reflection and shock drift acceleration; and electron DSA is efficient at oblique shocks.

  14. Shock, Post-Shock Annealing, and Post-Annealing Shock in Ureilites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    The thermal and shock histories of ureilites can be divided into four periods: 1) formation, 2) initial shock, 3) post-shock annealing, and 4) post-annealing shock. Period 1 occurred approx.4.55 Ga ago when ureilites formed by melting chondritic material. Impact events during period 2 caused silicate darkening, undulose to mosaic extinction in olivines, and the formation of diamond, lonsdaleite, and chaoite from indigenous carbonaceous material. Alkali-rich fine-grained silicates may have been introduced by impact injection into ureilites during this period. About 57% of the ureilites were unchanged after period 2. During period 3 events, impact-induced annealing caused previously mosaicized olivine grains to become aggregates of small unstrained crystals. Some ureilites experienced reduction as FeO at the edges of olivine grains reacted with C from the matrix. Annealing may also be responsible for coarsening of graphite in a few ureilites, forming euhedral-appearing, idioblastic crystals. Orthopyroxene in Meteorite Hills (MET) 78008 may have formed from pigeonite by annealing during this period. The Rb-Sr internal isochron age of approx.4.0 Ga for MET 78008 probably dates the annealing event. At this late date, impacts are the only viable heat source. About 36% of ureilites experienced period 3 events, but remained unchanged afterwards. During period 4, approx.7% of the ureilites were shocked again, as is evident in the polymict breccia, Elephant Moraine (EET) 83309. This rock contains annealed mosaicized olivine aggregates composed of small individual olivine crystals that exhibit undulose extinction. Ureilites may have formed by impact-melting chondritic material on a primitive body with heterogeneous O isotopes. Plagioclase was preferentially lost from the system due to its low impedance to shock compression. Brief melting and rapid burial minimized the escape of planetary-type noble gases from the ureilitic melts. Incomplete separation of metal from silicates

  15. Converging cylindrical shocks in ideal magnetohydrodynamics

    SciTech Connect

    Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, R.

    2014-09-15

    We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R=√(μ{sub 0}/p{sub 0}) I/(2 π) where I is the current, μ{sub 0} is the permeability, and p{sub 0} is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The

  16. Converging cylindrical shocks in ideal magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, R.

    2014-09-01

    We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R=sqrt{μ _0/p_0} I/(2 π ) where I is the current, μ0 is the permeability, and p0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field

  17. A study of shock mitigating materials in a split Hopkinson bar configuration. Phase 1

    SciTech Connect

    Bateman, V.I.; Brown, F.A.; Hansen, N.R.

    1998-06-01

    Sandia National Laboratories (SNL) designs mechanical systems with electronics that must survive high shock environments. These mechanical systems include penetrators that must survive soil, rock, and ice penetration, nuclear transportation casks that must survive transportation environments, and laydown weapons that must survive delivery impact of 125 fps. These mechanical systems contain electronics that may operate during and after the high shock environment and that must be protected from the high shock environments. A study has been started to improve the packaging techniques for the advanced electronics utilized in these mechanical systems because current packaging techniques are inadequate for these more sensitive electronics. In many cases, it has been found that the packaging techniques currently used not only do not mitigate the shock environment but actually amplify the shock environment. An ambitious goal for this packaging study is to avoid amplification and possibly attenuate the shock environment before it reaches the electronics contained in the various mechanical systems. As part of the investigation of packaging techniques, a two phase study of shock mitigating materials is being conducted. The purpose of the first phase reported here is to examine the performance of a joint that consists of shock mitigating material sandwiched in between steel and to compare the performance of the shock mitigating materials. A split Hopkinson bar experimental configuration simulates this joint and has been used to study the shock mitigating characteristics of seventeen, unconfined materials. The nominal input for these tests is an incident compressive wave with 50 fps peak (1,500 {micro}{var_epsilon} peak) amplitude and a 100 {micro}s duration (measured at 10% amplitude).

  18. Equipment limitations in pyrotechnic shock testing

    NASA Astrophysics Data System (ADS)

    Rehard, John W.; Czajkowski, John

    1990-01-01

    Limitations on the equipment used to measure, analyze, and record ordnance-indced pyrotechnic shocks are discussed. The focus is on the four primary components of the data acquisition and analysis system: accelerometers, tape recorders, filters, and analyzers. It is argued that a large percentage of pyrotechnic shock test data that are being generated today are inaccurate in that higher shock levels are indicated than the hardware is actually experiencing. It is suggested that a standard for pyrotechnic shock testing be established.

  19. Entropy jump across an inviscid shock wave

    NASA Technical Reports Server (NTRS)

    Salas, Manuel D.; Iollo, Angelo

    1995-01-01

    The shock jump conditions for the Euler equations in their primitive form are derived by using generalized functions. The shock profiles for specific volume, speed, and pressure are shown to be the same, however density has a different shock profile. Careful study of the equations that govern the entropy shows that the inviscid entropy profile has a local maximum within the shock layer. We demonstrate that because of this phenomenon, the entropy, propagation equation cannot be used as a conservation law.

  20. Suppressive and Facilitative Effects of Shock Intensity and Interresponse Times Followed by Shock

    ERIC Educational Resources Information Center

    Everly, Jessica B.; Perone, Michael

    2012-01-01

    Although response-dependent shock often suppresses responding, response facilitation can occur. In two experiments, we examined the suppressive and facilitative effects of shock by manipulating shock intensity and the interresponse times that produced shock. Rats' lever presses were reinforced on a variable-interval 40-s schedule of food…

  1. Shock Mounting for Heavy Machines

    NASA Technical Reports Server (NTRS)

    Thompson, A. R.

    1984-01-01

    Elastomeric bearings eliminate extraneous forces. Rocket thrust transmitted from motor to load cells via support that absorbs extraneous forces so they do not affect accuracy of thrust measurements. Adapter spoked cone fits over forward end of rocket motor. Shock mounting developed for rocket engines under test used as support for heavy machines, bridges, or towers.

  2. Shock-swallowing air sensor

    NASA Technical Reports Server (NTRS)

    Nugent, J.; Sakamoto, G. M.; Webb, L. D.; Couch, L. M.

    1979-01-01

    An air-data probe allows air to flow through it so that supersonic and hypersonic shock waves form behind pressure measuring orifices and tube instead of directly on them. Measured pressures are close to those in free-flowing air and are used to determine mach numbers of flying aircraft.

  3. Economic Shocks, Wealth, and Welfare

    ERIC Educational Resources Information Center

    Frankenberg, Elizabeth; Smith, James P.; Thomas, Duncan

    2003-01-01

    The immediate effects of the Asian crisis on the well-being of Indonesians are examined using the Indonesia Family Life Survey, an ongoing longitudinal household survey. There is tremendous diversity in the effect of the shock: for some households, it was devastating; for others it brought new opportunities. A wide array of mechanisms was adopted…

  4. Shock Response of Silicon Nitride

    NASA Astrophysics Data System (ADS)

    Dandekar, D. P.; Casem, D. T.; Motoyashiki, Y.; Sato, E.

    2009-12-01

    Silicon nitride is suitable for varied applications because its properties can be tailored through processing and doping. The current work presents shock response of silicon nitride marketed as SN282. The density of this material, 3.4 Mg/m3, exceeds its single crystal density, 3.2 Mg/m3, due to the presence of lutetium oxide as an additive around 5% by weight in the material. While the average grain size is 3.4 microns, the aspect ratio of the grains exceed 3. Preliminary results of shock wave experiments may be summarized as follows: (1) The Hugoniot Elastic Limit (HEL) of SN282 lies between 10.8 and 11.9 GPa. (2) The magnitude of the inelastic wave velocity just above the HEL is 8.73 km/s, suggesting that inelastic deformation above the HEL is due to shock induced plasticity in the material. (3) The value of the spall strength lies between 0.57 and 0.65 GPa. The spall strength of SN282 remains unchanged even when shocked beyond the HEL to at least 19.2 GPa unlike other brittle ceramics.

  5. Shock Response of Silicon Nitride

    NASA Astrophysics Data System (ADS)

    Dandekar, D. P.; Casem, D. T.; Motoyashiki, Y.; Sato, E.

    2009-06-01

    Silicon nitride is suitable for varied applications. The properties of silicon nitride have been tailored through processing and doping. The current work presents shock response of silicon nitride marketed as SN282. The density of this material, 3.4 Mg/m^3, exceeds its single crystal density due to the presence of lutetium oxide as an additive in ca. 5% by weight in the material. While the average grain size is 3.4 microns, aspect ratio of the grains exceed 3. Preliminary results of shock wave experiments may be summarized as follows: (1) The Hugoniot Elastic Limit (HEL) of SN282 is 11.2 GPa. (2) The magnitude of the inelastic wave velocity just above the HEL is 8.73 km/s, suggesting that inelastic deformation above the HEL is due to shock induced plasticity in the material. (3) The estimated value of the spall strength is 0.5 GPa. The spall strength of SN282 remains unchanged even when shocked beyond the HEL. The non-vanishing spall strength suggests that doping plays a role in the retention of spall strength of SN282. The role of doping needs to be further investigated.

  6. Shock characterization of TOAD pins

    SciTech Connect

    Weirick, L.J.; Navarro, N.J.

    1995-08-01

    The purpose of this program was to characterize Time Of Arrival Detectors (TOAD) pins response to shock loading with respect to risetime, amplitude, repeatability and consistency. TOAD pins were subjected to impacts of 35 to 420 kilobars amplitude and approximately 1 ms pulse width to investigate the timing spread of four pins and the voltage output profile of the individual pins. Sets of pins were also aged at 45{degrees}, 60{degrees}, and 80{degrees}C for approximately nine weeks before shock testing at 315 kilobars impact stress. Four sets of pins were heated to 50.2{degrees}C (125{degrees}F) for approximately two hours and then impacted at either 50 or 315 kilobars. Also, four sets of pins were aged at 60{degrees}C for nine weeks and then heated to 50.2{degrees}C before shock testing at 50 and 315 kilobars impact stress, respectively. Particle velocity measurements at the contact point between the stainless steel targets and TOAD pins were made using a Velocity Interferometer System for Any Reflector (VISAR) to monitor both the amplitude and profile of the shock waves.

  7. Shock characterization of toad pins

    SciTech Connect

    Weirick, L.J.; Navarro, M.J.

    1996-05-01

    The purpose of this program was to characterize Time Of Arrival Detectors (TOAD) pins response to shock loading with respect to risetime, amplitude, repeatability and consistency. TOAD pins were subjected to impacts of 35 to 420 kilobars amplitude and approximately 1 ms pulse width to investigate the timing spread of four pins and the voltage output profile of the individual pins. Sets of pins were also aged at 45{degree}, 60{degree} and 80{degree}C for approximately nine weeks before shock testing at 315 kilobars impact stress. Four sets of pins were heated to 50.2{degree}C (125{degree}F) for approximately two hours and then impacted at either 50 or 315 kilobars. Also, four sets of pins were aged at 60{degree}C for nine weeks and then heated to 50.2{degree}C before shock testing at 50 and 315 kilobars impact stress, respectively. Particle velocity measurements at the contact point between the stainless steel targets and TOAD pins were made using a Velocity Interferometer System for Any Reflector (VISAR) to monitor both the amplitude and profile of the shock waves. {copyright} {ital 1996 American Institute of Physics.}

  8. Model for shock wave chaos.

    PubMed

    Kasimov, Aslan R; Faria, Luiz M; Rosales, Rodolfo R

    2013-03-01

    We propose the following model equation, u(t) + 1/2(u(2)-uu(s))x = f(x,u(s)) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, x<0, and the shock is located at x = 0 for any t ≥ 0. Here, u(s)(t) is the shock state and the source term f is taken to mimic the chemical energy release in detonations. This equation retains the essential physics needed to reproduce many properties of detonations in gaseous reactive mixtures: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations. PMID:23521260

  9. Electrokinetic instability of isotachophoresis shocks

    NASA Astrophysics Data System (ADS)

    Garcia, Giancarlo; Santiago, Juan; Mani, Ali

    2013-11-01

    Isotachophoresis (ITP) is an electrokinetic focusing technique used in a variety of life science and analytical chemistry applications. In ITP, an electrokinetic shock wave forms at the interface between leading and trailing electrolytes with relatively high and low conductivities. The ITP interface is self-sharpening, as restoring electromigration fluxes counteract molecular diffusion. However, the large electric field gradient at the shock interface also gives rise to free charge and strong electrostatic body forces. At large applied currents, electrostatic forces cause recirculating flows which destabilize the ITP interface. We performed stability analysis and direct simulation of ITP shocks through numerical solutions to the coupled Nernst-Planck and Navier-Stokes equations using a quasi-electroneutral approximation. In both experiments and numerical simulations, we observe two modes of instability: 1) a distorted ITP interface which is steady in time, and 2) an oscillating perturbation which persists. In addition, at the highest simulated electric fields, we observe transition towards more chaotic oscillatory modes. We use our stability analysis and numerical simulations to characterize instability of ITP shocks using two dimensionless parameters.

  10. Shock desensitizing of solid explosive

    SciTech Connect

    Davis, William C

    2010-01-01

    Solid explosive can be desensitized by a shock wave too weak to initiate it promptly, and desensitized explosive does not react although its chemical composition is almost unchanged. A strong second shock does not cause reaction until it overtakes the first shock. The first shock, if it is strong enough, accelerates very slowly at first, and then more rapidly as detonation approaches. These facts suggest that there are two competing reactions. One is the usual explosive goes to products with the release of energy, and the other is explosive goes to dead explosive with no chemical change and no energy release. The first reaction rate is very sensitive to the local state, and the second is only weakly so. At low pressure very little energy is released and the change to dead explosive dominates. At high pressure, quite the other way, most of the explosive goes to products. Numerous experiments in both the initiation and the full detonation regimes are discussed and compared in testing these ideas.

  11. Converging finite-strength shocks

    NASA Astrophysics Data System (ADS)

    Axford, R. A.; Holm, D. D.

    1981-01-01

    The converging shock problem was first solved by Guderley and later by Landau and Stanyukovich for infinitely strong shocks in an ideal gas with spherical and cylindrical symmetry. This problem is solved herein for finite-strength shocks and a non-ideal-gas equation of state with an adiabatic bulk modulus of the type Bs= {- v∂ p}/{∂ v| s} = ( p +B) f( v) , where B is a constant with the dimensions of pressure, and f(v) is an arbitrary function of the specific volume. Self-similar profiles of the particle velocity and thermodynamic variables are studied explicitly for two cases with constant specific heat at constant volume; the Tait-Kirkwood-Murnaghan equation, f(v) = constant, and the Walsh equation, f(v) = v/A, where A = constant. The first case reduces to the ideal gas when B = 0. In both cases the flow behind the shock front exhibits an unbalanced buoyant force instability at a critical Mach number which depends upon equation-of-state parameters.

  12. Orion Nebula and Bow Shock

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a bow shock around a very young star in the nearby Orion nebula, an intense star-forming region of gas and dust.

    A picture, from the Hubble Heritage team, is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/05 or http://www.jpl.nasa.gov/images/wfpc . It was taken in February 1995 as part of the Hubble Orion Nebula mosaic by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    Named for the crescent-shaped wave a ship makes as it moves through water, a bow shock can form in space when two gas streams collide. In this case, the young star, LL Ori, emits a vigorous wind, a stream of charged particles moving rapidly outward from the star. Our own Sun has a less energetic version of this wind that is responsible for auroral displays on the Earth.

    The material spewed from LL Ori collides with slow-moving gas evaporating away from the center of the Orion nebula, located to the lower right of the image. The surface where the two winds collide is seen as the crescent-shaped bow shock.

    Unlike a water wave from a ship, this interstellar bow shock is three-dimensional. The filamentary emission has a distinct boundary on the side facing away from LL Ori, but is diffuse on the side closest to the star, a trait common to many bow shocks.

    A second, fainter bow shock can be seen around a star near the upper right-hand corner of the image. Astronomers have identified numerous shock fronts in this complex star-forming region and are using this data to understand the complex phenomena associated with star birth.

    The Orion nebula is a close neighbor in our Milky Way galaxy, at only 1,500 light-years from Earth. The filters used in this color composite represent oxygen, nitrogen, and hydrogen emissions.

  13. EASI - EQUILIBRIUM AIR SHOCK INTERFERENCE

    NASA Technical Reports Server (NTRS)

    Glass, C. E.

    1994-01-01

    New research on hypersonic vehicles, such as the National Aero-Space Plane (NASP), has raised concerns about the effects of shock-wave interference on various structural components of the craft. State-of-the-art aerothermal analysis software is inadequate to predict local flow and heat flux in areas of extremely high heat transfer, such as the surface impingement of an Edney-type supersonic jet. EASI revives and updates older computational methods for calculating inviscid flow field and maximum heating from shock wave interference. The program expands these methods to solve problems involving the six shock-wave interference patterns on a two-dimensional cylindrical leading edge with an equilibrium chemically reacting gas mixture (representing, for example, the scramjet cowl of the NASP). The inclusion of gas chemistry allows for a more accurate prediction of the maximum pressure and heating loads by accounting for the effects of high temperature on the air mixture. Caloric imperfections and specie dissociation of high-temperature air cause shock-wave angles, flow deflection angles, and thermodynamic properties to differ from those calculated by a calorically perfect gas model. EASI contains pressure- and temperature-dependent thermodynamic and transport properties to determine heating rates, and uses either a calorically perfect air model or an 11-specie, 7-reaction reacting air model at equilibrium with temperatures up to 15,000 K for the inviscid flowfield calculations. EASI solves the flow field and the associated maximum surface pressure and heat flux for the six common types of shock wave interference. Depending on the type of interference, the program solves for shock-wave/boundary-layer interaction, expansion-fan/boundary-layer interaction, attaching shear layer or supersonic jet impingement. Heat flux predictions require a knowledge (from experimental data or relevant calculations) of a pertinent length scale of the interaction. Output files contain flow

  14. A Study of Fundamental Shock Noise Mechanisms

    NASA Technical Reports Server (NTRS)

    Meadows, Kristine R.

    1997-01-01

    This paper investigates two mechanisms fundamental to sound generation in shocked flows: shock motion and shock deformation. Shock motion is modeled numerically by examining the interaction of a sound wave with a shock. This numerical approach is validated by comparison with results obtained by linear theory for a small-disturbance case. Analysis of the perturbation energy with Myers' energy corollary demonstrates that acoustic energy is generated by the interaction of acoustic disturbances with shocks. This analysis suggests that shock motion generates acoustic and entropy disturbance energy. Shock deformation is modeled numerically by examining the interaction of a vortex ring with a shock. These numerical simulations demonstrate the generation of both an acoustic wave and contact surfaces. The acoustic wave spreads cylindrically. The sound intensity is highly directional and the sound pressure increases with increasing shock strength. The numerically determined relationship between the sound pressure and the Mach number is found to be consistent with experimental observations of shock noise. This consistency implies that a dominant physical process in the generation of shock noise is modeled in this study.

  15. 33 CFR 159.105 - Shock test.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Shock test. 159.105 Section 159... MARINE SANITATION DEVICES Design, Construction, and Testing § 159.105 Shock test. The device, with liquid... shocks that are ten times the force of gravity (10g) and have a duration of 20-25 milliseconds...

  16. 33 CFR 159.105 - Shock test.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Shock test. 159.105 Section 159... MARINE SANITATION DEVICES Design, Construction, and Testing § 159.105 Shock test. The device, with liquid... shocks that are ten times the force of gravity (10g) and have a duration of 20-25 milliseconds...

  17. 33 CFR 159.105 - Shock test.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Shock test. 159.105 Section 159... MARINE SANITATION DEVICES Design, Construction, and Testing § 159.105 Shock test. The device, with liquid... shocks that are ten times the force of gravity (10g) and have a duration of 20-25 milliseconds...

  18. Shock characterization of Diallyl Phthalate (DAP)

    SciTech Connect

    Weirick, L.J.

    1992-09-01

    This study involved the shock characterization of Diallyl Phthalate (DAP), in particular, the equation of state as measured by the shock Hugoniot. Tests were done between 1 and 11 GPa impact shock pressure. The Hugoniot parameters were determined to be: [rho][sub 0]= 1.743, C[sub 0] = 2.20, and S = 2.33.

  19. Shock absorbing mount for electrical components

    NASA Technical Reports Server (NTRS)

    Dillon, R. F., Jr.; Mayne, R. C. (Inventor)

    1975-01-01

    A shock mount for installing electrical components on circuit boards is described. The shock absorber is made of viscoelastic material which interconnects the electrical components. With this system, shocks imposed on one component of the circuit are not transmitted to other components. A diagram of a typical circuit is provided.

  20. Reliable estimation of shock position in shock-capturing compressible hydrodynamics codes

    SciTech Connect

    Nelson, Eric M

    2008-01-01

    The displacement method for estimating shock position in a shock-capturing compressible hydrodynamics code is introduced. Common estimates use simulation data within the captured shock, but the displacement method uses data behind the shock, making the estimate consistent with and as reliable as estimates of material parameters obtained from averages or fits behind the shock. The displacement method is described in the context of a steady shock in a one-dimensional lagrangian hydrodynamics code, and demonstrated on a piston problem and a spherical blast wave.The displacement method's estimates of shock position are much better than common estimates in such applications.

  1. Stability of shocks relating to the shock ignition inertial fusion energy scheme

    SciTech Connect

    Davie, C. J. Bush, I. A.; Evans, R. G.

    2014-08-15

    Motivated by the shock ignition approach to improve the performance of inertial fusion targets, we make a series of studies of the stability of shock waves in planar and converging geometries. We examine stability of shocks moving through distorted material and driving shocks with non-uniform pressure profiles. We then apply a fully 3D perturbation, following this spherically converging shock through collapse to a distorted plane, bounce and reflection into an outgoing perturbed, broadly spherical shock wave. We find broad shock stability even under quite extreme perturbation.

  2. Culture shock: Improving software quality

    SciTech Connect

    de Jong, K.; Trauth, S.L.

    1988-01-01

    The concept of software quality can represent a significant shock to an individual who has been developing software for many years and who believes he or she has been doing a high quality job. The very idea that software includes lines of code and associated documentation is foreign and difficult to grasp, at best. Implementation of a software quality program hinges on the concept that software is a product whose quality needs improving. When this idea is introduced into a technical community that is largely ''self-taught'' and has been producing ''good'' software for some time, a fundamental understanding of the concepts associated with software is often weak. Software developers can react as if to say, ''What are you talking about. What do you mean I'm not doing a good job. I haven't gotten any complaints about my code yetexclamation'' Coupling such surprise and resentment with the shock that software really is a product and software quality concepts do exist, can fuel the volatility of these emotions. In this paper, we demonstrate that the concept of software quality can indeed pose a culture shock to developers. We also show that a ''typical'' quality assurance approach, that of imposing a standard and providing inspectors and auditors to assure its adherence, contributes to this shock and detracts from the very goal the approach should achieve. We offer an alternative, adopted through experience, to implement a software quality program: cooperative assistance. We show how cooperation, education, consultation and friendly assistance can overcome this culture shock. 3 refs.

  3. Vasoplegia in septic shock (review).

    PubMed

    Gamcrlidze, M M; Intskirveli, N A; Vardosanidze, K D; Chikhladze, Kh E; Goliadze, L Sh; Ratiani, L R

    2015-02-01

    Vasoplegia is considered as a key factor responsible for the death of patients with septic shock, due to persistent and irreversible hypotension. The latter associated with vascular hyporeactivity to vasoconstrictors is a significant independent prognostic factor of mortality in severe sepsis. Loss of control of the vascular tone occurs through the complex, multifactorial mechanism and implicates deeply disrupted balance between vasoconstrictors and vasodilators. The aim of this review is to discuss in detail the recent suggested alternative mechanisms of vasoplegia in severe sepsis: Overproduction of nitric oxide (NO) by activation of inducible form of nitric oxide synthase (iNOS); up-regulation of prostacyclin (PG12); vasopressin deficiency; significantly elevated levels of circulating endothelin; increased concentrations of vasodilator peptides such as adrenomedulin (AM) and calcitonin gene-related peptide (CGRP); oxidative stress inducing endothelial dysfunction and vascular hyporeactivity to vasoconstrictors; inactivation of catecholamines by oxidation; over-activation of ATP-sensitive potassium channels (KATP channels) during septic shock and their involvement in vascular dysfunction. The review also discusses some therapeutic approaches based on pathogenetic mechanisms of severe sepsis and their efficacy in treatment of patients with septic shock. The loss of vascular tone control occurs through the complex, multifactorial mechanism and implicates deeply disrupted balance between vasoconstrictors and vasodilators in the pathogenesis of septic shock. Overproduction of nitric oxide (NO) by the inducible form of nitric oxide synthase (iNOS); up-regulation of prostacyclin (PG12); vasopressin deficiency; elevated levels of circulating endothelin; increased concentrations of vasodilator peptides such as adrenomedulin (AM) and calcitonin gene-related peptide (CGRP); oxidative stress inducing endothelial dysfunction and vascular hyporeactivity to vasoconstrictors

  4. Permeability enhancement by shock cooling

    NASA Astrophysics Data System (ADS)

    Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean

    2015-04-01

    The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of

  5. Interplanetary Shocks Lacking Type 2 Radio Bursts

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Xie, H.; Maekela, P.; Akiyama, S.; Yashiro, S.; Kaiser, M. L.; Howard, R. A.; Bougeret, J.-L.

    2010-01-01

    We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (approximately 34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed approximately 535 km/s) and only approximately 40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km/s and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration approximately +6.8 m/s (exp 2)), while those associated with RL shocks were decelerating (average acceleration approximately 3.5 m/s (exp 2)). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is

  6. INTERPLANETARY SHOCKS LACKING TYPE II RADIO BURSTS

    SciTech Connect

    Gopalswamy, N.; Kaiser, M. L.; Xie, H.; Maekelae, P.; Akiyama, S.; Yashiro, S.; Howard, R. A.; Bougeret, J.-L.

    2010-02-20

    We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks ({approx}34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed {approx}535 km s{sup -1}) and only {approx}40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km s{sup -1} and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration {approx}+6.8 m s{sup -2}), while those associated with RL shocks were decelerating (average acceleration {approx}-3.5 m s{sup -2}). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is predominant

  7. Symmetry of spherically converging shock waves through reflection, relating to the shock ignition fusion energy scheme.

    PubMed

    Davie, C J; Evans, R G

    2013-05-01

    We examine the properties of perturbed spherically imploding shock waves in an ideal fluid through the collapse, bounce, and development into an outgoing shock wave. We find broad conservation of the size and shape of ingoing and outgoing perturbations when viewed at the same radius. The outgoing shock recovers the velocity of the unperturbed shock outside the strongly distorted core. The results are presented in the context of the robustness of the shock ignition approach to inertial fusion energy. PMID:23683207

  8. Probing combustion chemistry in a miniature shock tube with synchrotron VUV photo ionization mass spectrometry.

    PubMed

    Lynch, Patrick T; Troy, Tyler P; Ahmed, Musahid; Tranter, Robert S

    2015-02-17

    Tunable synchrotron-sourced photoionization time-of-flight mass spectrometry (PI-TOF-MS) is an important technique in combustion chemistry, complementing lab-scale electron impact and laser photoionization studies for a wide variety of reactors, typically at low pressure. For high-temperature and high-pressure chemical kinetics studies, the shock tube is the reactor of choice. Extending the benefits of shock tube/TOF-MS research to include synchrotron sourced PI-TOF-MS required a radical reconception of the shock tube. An automated, miniature, high-repetition-rate shock tube was developed and can be used to study high-pressure reactive systems (T > 600 K, P < 100 bar) behind reflected shock waves. In this paper, we present results of a PI-TOF-MS study at the Advanced Light Source at Lawrence Berkeley National Laboratory. Dimethyl ether pyrolysis (2% CH3OCH3/Ar) was observed behind the reflected shock (1400 < T5 < 1700 K, 3 < P5 < 16 bar) with ionization energies between 10 and 13 eV. Individual experiments have extremely low signal levels. However, product species and radical intermediates are well-resolved when averaging over hundreds of shots, which is ordinarily impractical in conventional shock tube studies. The signal levels attained and data throughput rates with this technique are comparable to those with other synchrotron-based PI-TOF-MS reactors, and it is anticipated that this high pressure technique will greatly complement those lower pressure techniques. PMID:25594229

  9. Shock Injection Problem and Beyond in Hybrid/Particle-in-Cell Simulations

    NASA Astrophysics Data System (ADS)

    Hoshino, Masahiro

    Collisionless shocks are a rich repository of nonlinear plasma instabilities and the self-regulated system of plasma waves, and provide not only quick thermalization but also nonthermal particle acceleration. One of the most widely accepted models of the nonthermal particle acceleration is the diffusive shock acceleration (DSA), which was established in the late seventies. In order that DSA operates effectively, however, the pre-acceleration of particles - the acceleration from the thermal into the suprathermal energies - is needed, namely, the so-called "shock injection problem" remains elusive. The transition from the thermal energies, the suprathermal energies, and the high energy nothermal particles are not well understood yet. With the recent advance of supper computer technology, kinetic plasma modeling by hybrid/particle-in-cell simulations are widely used for understanding the shock dynamics and the particle acceleration mechanisms etc. The modern computer capability is not enough to demonstrate DAS or other strong particle acceleration processes yet, but a great progress is now obtained. In this review talk, we discuss several important progresses: the pre-acceleration at the shock front as the particle injection problem, the turbulent wave generation in the shock transition/upstream as the particle scatterers of DAS, and the magnetic field amplification and so on. We will also give a perspective of the shock acceleration in the future simulation study.

  10. Frequency shift measurement in shock-compressed materials

    DOEpatents

    Moore, D.S.; Schmidt, S.C.

    1984-02-21

    A method is disclosed for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the stock front advancing through the sample, thereby minimizing adverse effects of refraction.

  11. Connecting Shock Parameters to the Radiation Hazard from Energetic Particles

    NASA Technical Reports Server (NTRS)

    Berdichevsky, Daniel B.; Reames, Donald V.; Lepping, Ronald P.; Schwenn, Rainer W.

    2004-01-01

    We use data from Helios, IMP-8, and other spacecraft (e.g. ISEE) to systematically investigate solar energetic particle (SEP) events from different longitudes and distances in the heliosphere. The purpose of the project is to assess empirically the connection between the morphology of the travelling shock and strength with observed enhancements in the flow of energized particles in shock accelerated particle (SEP) events (also often identified as "gradual" solar energetic particle events). Activities during this first year centered on the organization of the SEPs events and their correlation with solar wind observations at multiple spacecraft locations. From an identified list of more than 30 SEPs events at multiple spacecraft locations, currently four single cases for detailed study were selected and are in an advance phase of preparation for publication. Preliminary results of these four cases were presented at AGU Spring and Fall 2003 meetings, and other meetings on SEPs.

  12. The microphysics of collisionless shock waves.

    PubMed

    Marcowith, A; Bret, A; Bykov, A; Dieckman, M E; Drury, L O'C; Lembège, B; Lemoine, M; Morlino, G; Murphy, G; Pelletier, G; Plotnikov, I; Reville, B; Riquelme, M; Sironi, L; Novo, A Stockem

    2016-04-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics. PMID:27007555

  13. The microphysics of collisionless shock waves

    NASA Astrophysics Data System (ADS)

    Marcowith, A.; Bret, A.; Bykov, A.; Dieckman, M. E.; O'C Drury, L.; Lembège, B.; Lemoine, M.; Morlino, G.; Murphy, G.; Pelletier, G.; Plotnikov, I.; Reville, B.; Riquelme, M.; Sironi, L.; Stockem Novo, A.

    2016-04-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics.

  14. Increased survival of cirrhotic patients with septic shock

    PubMed Central

    2013-01-01

    Introduction The overall outcome of septic shock has been recently improved. We sought to determine whether this survival gain extends to the high-risk subgroup of patients with cirrhosis. Methods Cirrhotic patients with septic shock admitted to a medical intensive care unit (ICU) during two consecutive periods (1997-2004 and 2005-2010) were retrospectively studied. Results Forty-seven and 42 cirrhotic patients presented with septic shock in 1997-2004 and 2005-2010, respectively. The recent period differed from the previous one by implementation of adjuvant treatments of septic shock including albumin infusion as fluid volume therapy, low-dose glucocorticoids, and intensive insulin therapy. ICU and hospital survival markedly improved over time (40% in 2005-2010 vs. 17% in 1997-2004, P = 0.02 and 29% in 2005-2010 vs. 6% in 1997-2004, P = 0.009, respectively). Furthermore, this survival gain in the latter period was sustained for 6 months (survival rate 24% in 2005-2010 vs. 6% in 1997-2004, P = 0.06). After adjustment with age, the liver disease stage (Child-Pugh score), and the critical illness severity score (SOFA score), ICU admission between 2005 and 2010 remained an independent favorable prognostic factor (odds ratio (OR) 0.09, 95% confidence interval (CI) 0.02-0.4, P = 0.004). The stage of the underlying liver disease was also independently associated with hospital mortality (Child-Pugh score: OR 1.42 per point, 95% CI 1.06-1.9, P = 0.018). Conclusions In the light of advances in management of both cirrhosis and septic shock, survival of such patients substantially increased over recent years. The stage of the underlying liver disease and the related therapeutic options should be included in the decision-making process for ICU admission. PMID:23601847

  15. Simulation of shock wave buffet and its suppression on an OAT15A supercritical airfoil by IDDES

    NASA Astrophysics Data System (ADS)

    Huang, JingBo; Xiao, ZhiXiang; Liu, Jian; Fu, Song

    2012-02-01

    In the present paper, extremely unsteady shock wave buffet induced by strong shock wave/boundary-layer interactions (SWBLI) on the upper surface of an OAT15A supercritical airfoil at Mach number of 0.73 and angle of attack of 3.5 degrees is first numerically simulated by IDDES, one of the most advanced RANS/LES hybrid methods. The results imply that conventional URANS methods are unable to effectively predict the buffet phenomenon on the wing surface; IDDES, which involves more flow physics, predicted buffet phenomenon. Some complex flow phenomena are predicted and demonstrated, such as periodical oscillations of shock wave in the streamwise direction, strong shear layer detached from the shock wave due to SWBLI and plenty of small scale structures broken down by the shear layer instability and in the wake. The root mean square (RMS) of fluctuating pressure coefficients and streamwise range of shock wave oscillation reasonably agree with experimental data. Then, two vortex generators (VG) both with an inclination angle of 30 degrees to the main flow directions are mounted in front of the shock wave region on the upper surface to suppress shock wave buffet. The results show that shock wave buffet can be significantly suppressed by VGs, the RMS level of pressure in the buffet region is effectively reduced, and averaged shock wave position is obviously pushed downstream, resulting in increased total lift.

  16. Cosmic ray decreases caused by interplanetary shocks observed by the Brazilian Southern Space Observatory's Multidirectional Muon Detector

    NASA Astrophysics Data System (ADS)

    Deggeroni, Vinicíus; Echer, Ezequiel; Schuch, Nelson Jorge; Dal Lago, Alisson; Da Silva, Marlos; Bremm, Tiago

    The space between the planets in the Solar System is continuously permeated by the supermagnetosonic expansion of the solar atmosphere - the solar wind. This is a magnetized plasma that carries outward the sun’s magnetic field. Furthermore, the Sun’s sporadically emits huge coronal mass ejections (CMEs) that disturb the solar wind. When the interplanetary remnants of these CMEs are faster than the local plasma magnetosonic wave speed, shock waves are driven. These shock waves are observed as abrupt variations in solar wind plasma and magnetic field parameters. As one consequence, when these shock waves pass by Earth, cosmic ray decreases are observed by ground based cosmic ray detectors. It is the aim of this work to study interplanetary shock waves effects on cosmic rays measured at ground level. Interplanetary shocks are identified and their parameters determined using the plasma and magnetic field instruments of the Advanced Composition Explorer (ACE). Cosmic rays decreases are studied using the Multidirectional Muon Detector (MMD), in operation at the Southern Space Observatory - SSO/CRS/INPE-MCTI, in São Martinho da Serra, RS, Southern Brazil. The period of analysis is from January 2006 to July 2011. In this study it is calculated the shock strength, the magnetic field and plasma density compression ratio across the shocks. Besides, the cosmic ray decrease due to the shocks is determined. Further, the amplitude of cosmic ray decreases is correlated to the shock strength. The results are compared with previous published works.

  17. PARTICLE ACCELERATION IN SHOCK-SHOCK INTERACTION: MODEL TO DATA COMPARISON

    SciTech Connect

    Hietala, H.; Vainio, R.; Sandroos, A.

    2012-05-20

    Shock-shock interaction is a well-established particle acceleration mechanism in astrophysical and space plasmas, but difficult to study observationally. Recently, the interplanetary shock collision with the bow shock of the Earth on 1998 August 10 was identified as one of the rare events where detailed in situ observations of the different acceleration phases can be made. Due to the advantageous spacecraft and magnetic field configurations, in 2011, Hietala et al. were able to distinguish the seed population and its reacceleration at the bow shock, as well as the Fermi acceleration of particles trapped between the shocks. They also interpreted their results as being the first in situ evidence of the release of particles from the trap as the two shocks collided. In the present study we use a global 2.5D test-particle simulation to further study particle acceleration in this event. We concentrate on the last phases of the shock-shock interaction, when the shocks approach and pass through each other. The simulation results verify that the main features of the measurements can be explained by shock-shock interaction in this magnetic geometry, and are in agreement with the previous interpretation of particle release. Shock-shock collisions of this type occur commonly in many astrophysical locations such as stellar coronae, planetary and cometary bow shocks, and the distant heliosphere.

  18. The plasma physics of shock acceleration

    NASA Technical Reports Server (NTRS)

    Jones, Frank C.; Ellison, Donald C.

    1991-01-01

    The history and theory of shock acceleration is reviewed, paying particular attention to theories of parallel shocks which include the backreaction of accelerated particles on the shock structure. The work that computer simulations, both plasma and Monte Carlo, are playing in revealing how thermal ions interact with shocks and how particle acceleration appears to be an inevitable and necessary part of the basic plasma physics that governs collisionless shocks is discussed. Some of the outstanding problems that still confront theorists and observers in this field are described.

  19. Calorimetric thermobarometry of experimentally shocked quartz

    NASA Technical Reports Server (NTRS)

    Ocker, Katherine D.; Gooding, James L.; Hoerz, Friedrich

    1994-01-01

    Structural damage in experimentally shock-metamorphosed, granular quartz is quantitatively measurable by differential scanning calorimetry (DSC). Shock-induced loss of crystallinity is witnessed by disappearance of the alpha/beta phase transformation and evolution of a broad endoenthalpic strain peak at 650-900 K. The strain-energy peak grows rapidly at less than 10 GPa but declines with increasing shock pressure; it approaches zero at 32 GPa where vitrification is extensive. Effects of grain size and post-shock thermal history must be better understood before calorimetric thermobarometry of naturally shocked samples becomes possible.

  20. On the simulation of ballistic shock loads

    NASA Technical Reports Server (NTRS)

    Hollburg, Uwe

    1987-01-01

    Blast or penetrator-impact induced shocks are characterized by high acceleration levels, particularily in the higher frequency range and for a short time duration. These shocks are dangerous for the equipment of ships, combat vehicles, airplanes or spacecraft structures. As ballistic shock loads are insufficiently simulated by laboratory test machines, researchers designed a ballistic shock simulator. The impact induced shocks are simulated by an explosive and the vehicle to be bombarded is replaced by a simplified structure. This structure is suitable to accommodate any equipment which can be tested up to their load limits.

  1. Shock-front broadening in polycrystalline materials

    NASA Astrophysics Data System (ADS)

    Barber, J. L.; Kadau, K.

    2008-04-01

    We analyze a model for the evolution of shock fronts in polycrystalline materials. This model is based on the idea of Meyers and Carvalho [Mater. Sci. Eng. 24, 131 (1976)] that the shock velocity anisotropy within the polycrystal is the most important factor in shock front broadening. Our analysis predicts that the shock front width increases as the 1/2 power of the front penetration distance into the crystal. Our theoretical prediction is in plausible agreement with previous experimental results for the elastic precursor rise time, and it should therefore provide a useful shock width estimate. Furthermore, our theoretical framework is also applicable to other problems involving front propagation in heterogeneous media.

  2. Shock interference heating in scramjet engines

    NASA Technical Reports Server (NTRS)

    Wieting, Allan R.

    1990-01-01

    Experimental and analytical research sponsored by the NASA Langley Research center and the NASP Structures Technology Maturation Program to define critical aerothermal loads for the NASP engine is summarized. Presented is a review of (1) shock-shock interaction on the engine cowl leading edge that results in a supersonic jet impinging on the leading edge surface and causes the heat transfer rate to be amplified by a factor of 30 or more over the undisturbed (no shock interaction) flow stagnation point heat transfer rate, (2) the effectiveness of supersonic film cooling with and without the effects of an impinging oblique shock wave, and (3) oblique shock impingement in an axial compression corner.

  3. Shock drift mechanism for Forbush decreases

    NASA Technical Reports Server (NTRS)

    Cheng, Andrew F.; Sarris, E. T.; Dodopoulos, C.

    1990-01-01

    Consideration is given to the way in which Forbush decreases can arise from variable drifts in nonuniform shocks, where the variation in shock strength along the shock front causes both the shock drift distance and the energy gain to become variable. More particles can then be transported out of a given region of space and energy interval than were transported in, so a spacecraft passing through this region can observe a Forbush decrease in this energy interval despite shock energization and compression. A simple example of how this can occur is presented.

  4. Shock drift mechanism for Forbush decreases

    SciTech Connect

    Cheng, A.F.; Sarris, E.T.; Dodopoulos, C. Thrace Democritus Univ., Xanthe )

    1990-02-01

    Consideration is given to the way in which Forbush decreases can arise from variable drifts in nonuniform shocks, where the variation in shock strength along the shock front causes both the shock drift distance and the energy gain to become variable. More particles can then be transported out of a given region of space and energy interval than were transported in, so a spacecraft passing through this region can observe a Forbush decrease in this energy interval despite shock energization and compression. A simple example of how this can occur is presented. 20 refs.

  5. Shock Wave Dynamics in Weakly Ionized Plasmas

    NASA Technical Reports Server (NTRS)

    Johnson, Joseph A., III

    1999-01-01

    An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.

  6. Initial conditions of radiative shock experiments

    SciTech Connect

    Kuranz, C. C.; Drake, R. P.; Krauland, C. M.; Marion, D. C.; Grosskopf, M. J.; Rutter, E.; Torralva, B.; Holloway, J. P.; Bingham, D.; Goh, J.; Boehly, T. R.; Sorce, A. T.

    2013-05-15

    We performed experiments at the Omega Laser Facility to characterize the initial, laser-driven state of a radiative shock experiment. These experiments aimed to measure the shock breakout time from a thin, laser-irradiated Be disk. The data are then used to inform a range of valid model parameters, such as electron flux limiter and polytropic γ, used when simulating radiative shock experiments using radiation hydrodynamics codes. The characterization experiment and the radiative shock experiment use a laser irradiance of ∼7 × 10{sup 14} W cm{sup −2} to launch a shock in the Be disk. A velocity interferometer and a streaked optical pyrometer were used to infer the amount of time for the shock to move through the Be disk. The experimental results were compared with simulation results from the Hyades code, which can be used to model the initial conditions of a radiative shock system using the CRASH code.

  7. Corrugation of Relativistic Magnetized Shock Waves

    NASA Astrophysics Data System (ADS)

    Lemoine, Martin; Ramos, Oscar; Gremillet, Laurent

    2016-08-01

    As a shock front interacts with turbulence it develops corrugation, which induces outgoing wave modes in the downstream plasma. For a fast shock wave, the incoming wave modes can either be fast magnetosonic waves originating downstream, outrunning the shock, or eigenmodes of the upstream plasma drifting through the shock. Using linear perturbation theory in relativistic MHD, this paper provides a general analysis of the corrugation of relativistic magnetized fast shock waves resulting from their interaction with small amplitude disturbances. Transfer functions characterizing the linear response for each of the outgoing modes are calculated as a function of the magnetization of the upstream medium and as a function of the nature of the incoming wave. Interestingly, if the latter is an eigenmode of the upstream plasma, we find that there exists a resonance at which the (linear) response of the shock becomes large or even diverges. This result may have profound consequences on the phenomenology of astrophysical relativistic magnetized shock waves.

  8. Bow shock and magnetosheath waves at Mercury

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Behannon, K. W.

    1975-01-01

    Mariner 10 measurements at the Mercury bow shock provide examples where the magnetic field is approximately parallel or perpendicular to the bow shock normal. Upstream of a broad irregular parallel shock, left hand circularly polarized waves are observed which cut off very sharply at approximately 4 Hz. Upstream of a perpendicular shock, right hand circularly polarized waves are observed which persist up to the Nyquist frequency of 12 Ha. Determination of the wave propagation vector as a function of frequency helps conclusively identify the waves as whistler mode waves propagating from the shock. The magnetosheath downstream of the parallel shock is disturbed more than that downstream of the perpendicular shock particularly below 1 Hz. In the latter case regular left hand polarized waves observed slightly above the proton gyrofrequency are identified as ion cyclotron waves with wavelength approximately 300 km which are Doppler shifted up to their observed frequency.

  9. Shock-induced chemistry in organic materials

    SciTech Connect

    Dattelbaum, Dana M; Sheffield, Steve; Engelke, Ray; Manner, Virginia; Chellappa, Raja; Yoo, Choong - Shik

    2011-01-20

    The combined 'extreme' environments of high pressure, temperature, and strain rates, encountered under shock loading, offer enormous potential for the discovery of new paradigms in chemical reactivity not possible under more benign conditions. All organic materials are expected to react under these conditions, yet we currently understand very little about the first bond-breaking steps behind the shock front, such as in the shock initiation of explosives, or shock-induced reactivity of other relevant materials. Here, I will present recent experimental results of shock-induced chemistry in a variety of organic materials under sustained shock conditions. A comparison between the reactivity of different structures is given, and a perspective on the kinetics of reaction completion under shock drives.

  10. About Shape of an Interplanetary Shock Front.

    NASA Astrophysics Data System (ADS)

    Petukhov, Ivan; Petukhov, Stanislav

    The form of an interplanetary shock front has been investigated by the statistical method. Results of determination the components of normals to the interplanetary shock fronts obtained from data of ACE experiment during from 1998 to 2003 years (about 200 measurements) are used. North-south asymmetry of shock amount about 15% is revealed. Possibly, it is caused by more activity of the north semi-sphere of the Sun. East-west asymmetry of shock area are obtained. At probability 95% values of asymmetry more 0.53 and less 0.65 at most probability 0.59. Here asymmetry is ratio west part of area to whole area of shock front. Possibly, it is formed at propagation of a shock in interplanetary space. The reason of asymmetry may be self-generation turbulence by the accelerated particles which influences on velocity of shock propagation.

  11. Water impact shock test system

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The basic objective was to design, manufacture, and install a shock test system which, in part, would have the ability to subject test articles weighing up to 1,000 pounds to both half sine and/or full sine pulses having peak levels of up to 50 G's with half sine pulse durations of 100 milliseconds or full sine period duration of 200 milliseconds. The tolerances associated with the aforementioned pulses were +20% and -10% for the peak levels and plus or minus 10% for the pulse durations. The subject shock test system was to be capable of accepting test article sizes of up to 4 feet by 4 feet mounting surface by 4 feet in length.

  12. Shock response of dry sand.

    SciTech Connect

    Reinhart, William Dodd; Thornhill, Tom Finley, III; Chhabildas, Lalit C..; Vogler, Tracy John; Brown, Justin L.

    2007-08-01

    The dynamic compaction of sand was investigated experimentally and computationally to stresses of 1.8 GPa. Experiments have been performed in the powder's partial compaction regime at impact velocities of approximately 0.25, 0.5, and 0.75 km/s. The experiments utilized multiple velocity interferometry probes on the rear surface of a stepped target for an accurate measurement of shock velocity, and an impedance matching technique was used to deduce the shock Hugoniot state. Wave profiles were further examined for estimates of reshock states. Experimental results were used to fit parameters to the P-Lambda model for porous materials. For simple 1-D simulations, the P-Lambda model seems to capture some of the physics behind the compaction process very well, typically predicting the Hugoniot state to within 3%.

  13. Specification of pyro shock tests

    NASA Technical Reports Server (NTRS)

    Trummel, M.

    1976-01-01

    Specifications of pyro shock tests are treated as the interconnection between raw measurements (or estimates) of the environment and the various test methods available. After a definition of the environment, various aspects of test method specification are discussed including one-sided pulses, test simulation parameters, and the effects of Q. Different test configurations are considered including rigid fixture tests, pseudo-real structure, and real structure.

  14. Astrospheres and Stellar Bow shocks

    NASA Astrophysics Data System (ADS)

    Van Marle, Allard Jan

    2016-07-01

    As stars evolve, they deliver feedback to the surrounding medium in the form of stellar wind and radiation. These shape the surrounding matter, forming what is called an astrosphere, a sphere of influence in which the star dominates the morphology and composition of the surrounding medium. Astrospheres are fascinating objects. Because they are formed through the interaction between the stellar feedback and the interstellar gas, they can tell us a great deal about both. Furthermore, because they are shaped over time they provide us with a window into the past. This is of particular interest for the study of stellar evolution, because the astrosphere reflects changes in the properties of the stellar wind, which relate directly to the properties of the star. A special sub-class of astrospheres, the stellar bow shocks, occur when the progenitor star moves through the surrounding medium at supersonic speed. Because the properties of the bow shock relate directly to both the stellar wind and the interstellar medium, the shape and size of the bow shock can be used to determine these properties. Using state-of-the-art numerical codes, it is possible to simulate the interaction between the stellar wind and radiation and the interstellar medium. These results can then be compared to observations. They can also be used to predict the type of observations that are best suited to study these objects. In this fashion computational and observational astronomy can support each other in their efforts to gain a better understanding of stars and their environment.

  15. Proton Acceleration at Oblique Shocks

    NASA Astrophysics Data System (ADS)

    Galinsky, V. L.; Shevchenko, V. I.

    2011-06-01

    Acceleration at the shock waves propagating oblique to the magnetic field is studied using a recently developed theoretical/numerical model. The model assumes that resonant hydromagnetic wave-particle interaction is the most important physical mechanism relevant to motion and acceleration of particles as well as to excitation and damping of waves. The treatment of plasma and waves is self-consistent and time dependent. The model uses conservation laws and resonance conditions to find where waves will be generated or damped, and hence particles will be pitch-angle-scattered. The total distribution is included in the model and neither introduction of separate population of seed particles nor some ad hoc escape rate of accelerated particles is needed. Results of the study show agreement with diffusive shock acceleration models in the prediction of power spectra for accelerated particles in the upstream region. However, they also reveal the presence of spectral break in the high-energy part of the spectra. The role of the second-order Fermi-like acceleration at the initial stage of the acceleration is discussed. The test case used in the paper is based on ISEE-3 data collected for the shock of 1978 November 12.

  16. PROTON ACCELERATION AT OBLIQUE SHOCKS

    SciTech Connect

    Galinsky, V. L.; Shevchenko, V. I.

    2011-06-20

    Acceleration at the shock waves propagating oblique to the magnetic field is studied using a recently developed theoretical/numerical model. The model assumes that resonant hydromagnetic wave-particle interaction is the most important physical mechanism relevant to motion and acceleration of particles as well as to excitation and damping of waves. The treatment of plasma and waves is self-consistent and time dependent. The model uses conservation laws and resonance conditions to find where waves will be generated or damped, and hence particles will be pitch-angle-scattered. The total distribution is included in the model and neither introduction of separate population of seed particles nor some ad hoc escape rate of accelerated particles is needed. Results of the study show agreement with diffusive shock acceleration models in the prediction of power spectra for accelerated particles in the upstream region. However, they also reveal the presence of spectral break in the high-energy part of the spectra. The role of the second-order Fermi-like acceleration at the initial stage of the acceleration is discussed. The test case used in the paper is based on ISEE-3 data collected for the shock of 1978 November 12.

  17. Shock dynamics of phase diagrams

    SciTech Connect

    Moro, Antonio

    2014-04-15

    A thermodynamic phase transition denotes a drastic change of state of a physical system due to a continuous change of thermodynamic variables, as for instance pressure and temperature. The classical van der Waals equation of state is the simplest model that predicts the occurrence of a critical point associated with the gas–liquid phase transition. Nevertheless, below the critical temperature theoretical predictions of the van der Waals theory significantly depart from the observed physical behaviour. We develop a novel approach to classical thermodynamics based on the solution of Maxwell relations for a generalised family of nonlocal entropy functions. This theory provides an exact mathematical description of discontinuities of the order parameter within the phase transition region, it explains the universal form of the equations of state and the occurrence of triple points in terms of the dynamics of nonlinear shock wave fronts. -- Highlights: •A new generalisation of van der Waals equation of state. •Description of phase transitions in terms of shock dynamics of state curves. •Proof of the universality of equations of state for a general class of models. •Interpretation of triple points as confluence of classical shock waves. •Correspondence table between thermodynamics and nonlinear conservation laws.

  18. Shock desensitizing of solid explosives

    SciTech Connect

    Davis, William C

    2010-01-01

    Solid explosive can be desensitized by a shockwave too weak to initiate it promptly, and desensitized explosive does not react although its chemical composition is almost unchanged. A strong second shock does not cause reaction until it overtakes the first shock. The first shock, if it is strong enough, accelerates very slowly at first, and then more rapidly as detonation approaches. These facts suggest that there are two competing reactions. One is the usual explosive goes to products with the release of energy, and the other is explosive goes to dead explosive with no chemical change and no energy release. The first reaction rate is very sensitive to the local state, and the second is only weakly so. At low pressure very little energy is released and the change to dead explosive dominates. At high pressure, quite the other way, most of the explosive goes to products. Numerous experiments in both the initiation and the full detonation regimes are discussed and compared in support of these ideas.

  19. Shock tunnel studies of scramjet phenomena, supplement 6

    NASA Technical Reports Server (NTRS)

    Wendt, M.; Nettleton, M.; Morgan, R. G.; Skinner, K.; Casey, R.; Stalker, R.; Brescianini, C.; Paull, A.; Allen, G.; Smart, M.

    1993-01-01

    Reports by the staff of the University of Queensland on various research studies related to the advancement of scramjet technology are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation.

  20. Shock tunnel studies of scramjet phenomena, supplement 8

    NASA Technical Reports Server (NTRS)

    Stalker, R. J.; Hollis, P.; Allen, G. A.; Roberts, G. T.; Tuttle, S.; Bakos, R. J.; Morgan, R. G.; Pulsonetti, M. V.; Brescianini, C.; Buttsworth, D. R.

    1993-01-01

    Reports by the staff of the University of Oueensland on various research studies related to the advancement of scramjet technology are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation. This research activity is Supplement 8 under NASA Grant NAGW-674.

  1. Shock tunnel studies of scramjet phenomena, supplement 7

    NASA Technical Reports Server (NTRS)

    Bakos, R. J.; Morgan, R. G.; Tuttle, S. L.; Kelly, G. M.; Paull, A.; Simmons, J. M.; Stalker, R. J.; Pulsonetti, M. V.; Buttsworth, D.; Allen, G. A., Jr.

    1993-01-01

    Reports by the staff of the University of Queensland on various research studies related to the advancement of scramjet technology are presented. These reports document the tests conducted in the reflected shock tunnel T4 and supporting research facilities that have been used to study the injection, mixing, and combustion of hydrogen fuel in generic scramjets at flow conditions typical of hypersonic flight. In addition, topics include the development of instrumentation and measurement technology, such as combustor wall shear and stream composition in pulse facilities, and numerical studies and analyses of the scramjet combustor process and the test facility operation. This research activity is Supplement 7 under NASA Grant NAGW-674.

  2. New approach of assessing hypovolemic shock class 1 during acute emergencies: Ultrasonographic inferior vena cava and abdominal aorta diameter ratio

    NASA Astrophysics Data System (ADS)

    Ahmad, Rashidi; Kunji, Mohamad Iqhbal; Hj Abd Kareem, Meera Mohaideen; Halim, Shamimi A.

    2013-09-01

    In a patient with hypovolemic shock class 1, the vital signs and biochemical properties are almost normal. The alteration of hemodynamic parameters and biochemical values occurs mainly in advanced hypovolemia state (neuroendocrine response). The availability of ultrasound machine at healthcare centers makes the measurement of vascular calibre feasible and possible. Inspiration and expiration inferior vena cava diameter changes predict hypovolemic shock class 1 but in acute emergencies this method is impractical. The purpose of this study is to develop a new approach in identifying hypovolemic shock at early phase by measuring the inferior vena cava and aorta diameter ratio using bedside ultrasound machine.

  3. Right colon cancer presenting as hemorrhagic shock.

    PubMed

    Iwata, Tomoyuki; Konishi, Kazuo; Yamazaki, Takahisa; Kitamura, Katsuya; Katagiri, Atsushi; Muramoto, Takashi; Kubota, Yutaro; Yano, Yuichiro; Kobayashi, Yoshiya; Yamochi, Toshiko; Ohike, Nobuyuki; Murakami, Masahiko; Gokan, Takehiko; Yoshikawa, Nozomi; Imawari, Michio

    2011-02-15

    A 67-year-old man visited our hospital with a history of continuous hematochezia leading to hemorrhagic shock. An abdominal computed tomography scan revealed a large mass in the ascending colon invading the duodenum and pancreatic head as well as extravasation of blood from the gastroduodenal artery (GDA) into the colon. Colonoscopy revealed an irregular ulcerative lesion and stenosis in the ascending colon. Therefore, right hemicolectomy combined with pylorus-preserving pancreaticoduodenectomy was performed. Histologically, the tumor was classified as a moderately differentiated adenocarcinoma. Moreover, cancer cells were mainly located in the colon but had also invaded the duodenum and pancreas and involved the GDA. Immunohistochemically, the tumor cells were positive for cytokeratin (CK)20 and carcinoembryonic antigen (CEA) but not for CK7 and carbohydrate antigen (CA)19-9. The patient died 23 d after the surgery because he had another episode of arterial bleeding from the anastomosis site. Although En bloc resection of the tumor with pancreaticoduodenectomy and colectomy performed for locally advanced colon cancer can ensure long-term survival, patients undergoing these procedures should be carefully monitored, particularly when the tumor involves the main artery. PMID:21607161

  4. Analysis of shock pulses for environmental tests

    NASA Technical Reports Server (NTRS)

    Houghton, J. R.

    1977-01-01

    Specifications for shock testing of components that will be used on the Space Shuttle vehicles require very high acceleration levels. A special shock machine was built for testing of rocket components to determine if they can meet the specified accelerations. Calibrations of transducers and methods to monitor the shock tests raised several signature-analysis questions. In this report, calibration capabilities of shock accelerometers are found to be limited to 10,000g. Equivalency of the mechanical shock test and the rocket pyrotechnic shock are examined, and two simple relationships for equivalency are proposed. Five different pulse signature-analysis techniques are tested on analytical and experimental pulse data and recommendations are made for the signature technique which most clearly identifies the magnitude of the impulse applied to the test specimen.

  5. Shock compaction of high- Tc superconductors

    SciTech Connect

    Weir, S.T.; Nellis, W.J.; McCandless, P.C.; Brocious, W.F. ); Seaman, C.L.; Early, E.A.; Maple, M.B. . Dept. of Physics); Kramer, M.J. ); Syono, Y.; Kikuchi, M. )

    1990-09-01

    We present the results of shock compaction experiments on high-{Tc} superconductors and describe the way in which shock consolidation addresses critical problems concerning the fabrication of high J{sub c} bulk superconductors. In particular, shock compaction experiments on YBa{sub 2}Cu{sub 3}O{sub 7} show that shock-induced defects can greatly increase intragranular critical current densities. The fabrication of crystallographically aligned Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} samples by shock-compaction is also described. These experiments demonstrate the potential of the shock consolidation method as a means for fabricating bulk high-{Tc} superconductors having high critical current densities.

  6. Propagation of shock waves through petroleum suspensions

    NASA Astrophysics Data System (ADS)

    Mukuk, K. V.; Makhkamov, S. M.; Azizov, K. K.

    1986-01-01

    Anomalous shock wave propagation through petroleum with a high paraffin content was studied in an attempt to confirm the theoretically predicted breakdown of a forward shock wave into oscillating waves and wave packets as well as individual solitons. Tests were performed in a shock tube at 10, 20, and 50 to 60 C, with pure kerosene as reference and with kerosene + 5, 10, 15, and 20% paraffin. The addition of paraffin was found to radically alter the rheodynamic characteristics of the medium and, along with it, the pattern of shock wave propagation. The integro-differential equation describing a one dimensional hydraulic shock process in viscoelastic fluids is reduced to the Burgers-Korteweg-deVries equation, which is solved numerically for given values of the system parameters. The results indicate that the theory of shock wave propagation through such an anomalous suspension must be modified.

  7. Shock metamorphism of lunar and terrestrial basalts

    NASA Technical Reports Server (NTRS)

    Schaal, R. B.; Hoerz, F.

    1977-01-01

    Lonar Crater (India) basalt and lunar basalt 75035 were shock loaded under controlled laboratory conditions up to 1000 kbar, generally in a CO/CO2 (1:1) environment evacuated to 10 to the minus seventh power torr. The Kieffer et al. (1976) classification scheme of progressive shock metamorphism is found to apply to lunar basalts. The major shock features of the five classes that span the range 0 to 1000 kbar are described. Only three out of 152 basalt specimens show shock effects in their natural state as severe as Class 2 features. The scarcity of shocked basalt hand samples in contrast to the abundance of shock-produced agglutinates and homogeneous glass spheres in the lunar regolith indicates the dominant role of micrometeorite impact in the evolution of the lunar regolith. The overall glass content in asteroidal and Mercurian regoliths is considered.

  8. Shock metamorphic effects in lunar microcraters

    NASA Technical Reports Server (NTRS)

    Schaal, R. B.; Hoerz, F.; Gibbons, R. V.

    1976-01-01

    Detailed petrographic descriptions and results of electron microprobe analyses are presented for impact glasses as well as shocked and unshocked minerals associated with individual lunar microcraters (diameters of 0.4 to 4.4 mm). Rocks of four typical lunar lithologies are studied: anorthosite, anorthositic norite, ophitic basalt, and polymict breccia. Textures, mineralogies, and chemical compositions are examined along a radial traverse through each microcrater; i.e., across the impact glasses lining the crater wall, the shock-metamorphosed zone immediately underlying the glass liner, and the unshocked host rock. The microcraters are discussed in a sequence of increasing mineralogical complexity of the host rock (from anorthosite to polymict breccia) in order to distinguish shock effects among mineral types. The shock metamorphic features observed are found to be comparable to those reported in shocked basalt from Lonar Crater, India, and are categorized into five shock-intensity classes with pressures experimentally calibrated.

  9. Exhaust Nozzle Plume and Shock Wave Interaction

    NASA Technical Reports Server (NTRS)

    Castner, Raymond S.; Elmiligui, Alaa; Cliff, Susan

    2013-01-01

    Fundamental research for sonic boom reduction is needed to quantify the interaction of shock waves generated from the aircraft wing or tail surfaces with the exhaust plume. Both the nozzle exhaust plume shape and the tail shock shape may be affected by an interaction that may alter the vehicle sonic boom signature. The plume and shock interaction was studied using Computational Fluid Dynamics simulation on two types of convergent-divergent nozzles and a simple wedge shock generator. The nozzle plume effects on the lower wedge compression region are evaluated for two- and three-dimensional nozzle plumes. Results show that the compression from the wedge deflects the nozzle plume and shocks form on the deflected lower plume boundary. The sonic boom pressure signature of the wedge is modified by the presence of the plume, and the computational predictions show significant (8 to 15 percent) changes in shock amplitude.

  10. Remote shock sensing and notification system

    DOEpatents

    Muralidharan, Govindarajan; Britton, Charles L.; Pearce, James; Jagadish, Usha; Sikka, Vinod K.

    2008-11-11

    A low-power shock sensing system includes at least one shock sensor physically coupled to a chemical storage tank to be monitored for impacts, and an RF transmitter which is in a low-power idle state in the absence of a triggering signal. The system includes interference circuitry including or activated by the shock sensor, wherein an output of the interface circuitry is coupled to an input of the RF transmitter. The interface circuitry triggers the RF transmitting with the triggering signal to transmit an alarm message to at least one remote location when the sensor senses a shock greater than a predetermined threshold. In one embodiment the shock sensor is a shock switch which provides an open and a closed state, the open state being a low power idle state.

  11. Remote shock sensing and notification system

    DOEpatents

    Muralidharan, Govindarajan [Knoxville, TN; Britton, Charles L [Alcoa, TN; Pearce, James [Lenoir City, TN; Jagadish, Usha [Knoxville, TN; Sikka, Vinod K [Oak Ridge, TN

    2010-11-02

    A low-power shock sensing system includes at least one shock sensor physically coupled to a chemical storage tank to be monitored for impacts, and an RF transmitter which is in a low-power idle state in the absence of a triggering signal. The system includes interface circuitry including or activated by the shock sensor, wherein an output of the interface circuitry is coupled to an input of the RF transmitter. The interface circuitry triggers the RF transmitter with the triggering signal to transmit an alarm message to at least one remote location when the sensor senses a shock greater than a predetermined threshold. In one embodiment the shock sensor is a shock switch which provides an open and a closed state, the open state being a low power idle state.

  12. Effects of shock pressures on calcic plagioclase

    NASA Technical Reports Server (NTRS)

    Gibbons, R. V.; Ahrens, T. J.

    1977-01-01

    Calcic plagioclase single crystals were subjected to shock loading up to a pressure of 496 kbar; optical and electron microscope studies were conducted to investigate the shock-induced effects on the mineral, which is found in terrestrial and lunar rocks and in meteorites. It was observed that up to 287 kbar pressure, the recovered samples are essentially crystalline, while samples subjected to pressures between 300 and 400 kbar are almost 100% diaplectic glasses, suggesting shock transformation in the solid state. Samples shock-loaded to pressures greater than 400 kbar yielded glasses with refractive indices similar to those of thermally fused glass. It is concluded that planar features, absent in all the specimens, may not be definitive shock indicators, but may be linked to local heterogeneous dynamic stresses experienced by plagioclase grains within shocked rocks.

  13. Entropy Generation Across Earth's Bow Shock

    NASA Technical Reports Server (NTRS)

    Parks, George K.; McCarthy, Michael; Fu, Suiyan; Lee E. s; Cao, Jinbin; Goldstein, Melvyn L.; Canu, Patrick; Dandouras, Iannis S.; Reme, Henri; Fazakerley, Andrew; Lin, Naiguo; Wilber, Mark

    2011-01-01

    Earth's bow shock is a transition layer that causes an irreversible change in the state of plasma that is stationary in time. Theories predict entropy increases across the bow shock but entropy has never been directly measured. Cluster and Double Star plasma experiments measure 3D plasma distributions upstream and downstream of the bow shock that allow calculation of Boltzmann's entropy function H and his famous H-theorem, dH/dt O. We present the first direct measurements of entropy density changes across Earth's bow shock. We will show that this entropy generation may be part of the processes that produce the non-thermal plasma distributions is consistent with a kinetic entropy flux model derived from the collisionless Boltzmann equation, giving strong support that solar wind's total entropy across the bow shock remains unchanged. As far as we know, our results are not explained by any existing shock models and should be of interests to theorists.

  14. Shock attenuation at the Slate Islands revisited

    NASA Technical Reports Server (NTRS)

    Wu, S.; Robertson, P. B.; Grieve, R. A. F.

    1993-01-01

    This study of a more extensive suite of Slate Islands samples confirms previous interpretations. It indicates clearly that recorded shock pressures, as determined by planar deformation feature orientations, increased towards the center. The 'shock center' is very close (considering the structural movements during cavity modification) to that from an independent determination from shatter cone orientations. Shock metamorphism at a higher level in breccia clasts than in the adjacent country rocks is evidence that the shock event preceded the formation of the breccia dikes. These observations, which are consistent with those at other impact structures, are all contrary to the interpretation by Sage that breccia dike formation by diatreme action was the source of the shock event. There is no plausible reason to consider the Slate Islands as anything but the emergent portion of the central uplift of a complex impact crater. It cannot be cited as an example of endogenic shock in arguments regarding evidence of impact in the terrestrial stratigraphic record.

  15. Theory and simulation of collisionless parallel shocks

    NASA Technical Reports Server (NTRS)

    Quest, K. B.

    1988-01-01

    This paper presents a self-consistent theoretical model for collisionless parallel shock structure, based on the hypothesis that shock dissipation and heating can be provided by electromagnetic ion beam-driven instabilities. It is shown that shock formation and plasma heating can result from parallel propagating electromagnetic ion beam-driven instabilities for a wide range of Mach numbers and upstream plasma conditions. The theoretical predictions are compared with recently published observations of quasi-parallel interplanetary shocks. It was found that low Mach number interplanetary shock observations were consistent with the explanation that group-standing waves are providing the dissipation; two high Mach number observations confirmed the theoretically predicted rapid thermalization across the shock.

  16. Shock wave control using liquid curtains

    NASA Astrophysics Data System (ADS)

    Colvert, Brendan; Tao, Xingtian; Eliasson, Veronica

    2014-11-01

    The effectiveness of a planar wall of liquid as a blast mitigation device is examined using a shock tube and a custom-designed and -built shock test chamber. Experimental data collection methods being used include high-speed schlieren photography and high-frequency pressure sensors. During the relevant shock interaction time periods, the liquid-gas interface is examined to determine its effect on shock waves. The characteristic quantities that reflect these effects include reflected-to-incident shock strength ratio, transmitted-to-incident shock strength ratio, transmitted and reflected impulse, and peak pressure reduction. These parameters are examined for correlations to incident wave speed, liquid mass, liquid density, and liquid viscosity. Initial results have been obtained that show a correlation between fluid mass and peak pressure reduction. More experiments are being performed to further explore this relationship as well as examine the effects of altering the other parameters such as liquid-gas interface geometry and using dilatant fluids.

  17. The earth's foreshock, bow shock, and magnetosheath

    SciTech Connect

    Onsager, T.G.; Thomsen, M.F. )

    1991-01-01

    Studies directly pertaining to the earth's foreshock, bow shock, and magnetosheath are reviewed, and some comparisons are made with data on other planets. Topics considered in detail include the electron foreshock, the ion foreshock, the quasi-parallel shock, the quasi-perpendicular shock, and the magnetosheath. Information discussed spans a broad range of disciplines, from large-scale macroscopic plasma phenomena to small-scale microphysical interactions. 184 refs.

  18. Shock-boundary-layer interaction in flight

    NASA Technical Reports Server (NTRS)

    Bertelrud, Arild

    1989-01-01

    A brief survey is given on the study of transonic shock/boundary layer effects in flight. Then the possibility of alleviating the adverse shock effects through passive shock control is discussed. A Swedish flight experiment on a swept wing attack aircraft is used to demonstrate how it is possible to reduce the extent of separated flow and increase the drag-rise Mach number significantly using a moderate amount of perforation of the surface.

  19. Survival of carbon grains in shocks

    NASA Technical Reports Server (NTRS)

    Seab, C. Gregory

    1990-01-01

    Supernova shocks play a significant part in the life of an interstellar grain. In a typical 10 to the 9th power year lifetime, a grain will be hit by an average of 10 shocks of 100 km s(sup -1) or greater velocity, and even more shocks of lower velocity. Evaluation of the results of this frequent shock processing is complicated by a number of uncertainties, but seems to give about 10 percent destruction of silicate grains and about half that for graphite grains. Because of the frequency of shocking, the mineralogy and sizes of the grain population is predominately determined by shock processing effects, and not by the initial grain nucleation and growth environment. One consequence of the significant role played by interstellar shocks is that a certain fraction (up to 5 percent) of the carbon should be transformed into the diamond phase. Diamond transformation is observed in the laboratory at threshold shock pressures easily obtainable in grain-grain collisions in supernova shocks. Yields for transforming graphite, amorphous carbon, glassy carbon, and other nearly pure carbon solids into diamond are quite high. Impurities up to at least the 10 percent level (for oxygen) are tolerated in the process. The typical size diamond expected from shock transformation agrees well with the observed sizes in the Lewis et al. findings in meteoritic material. Isotropic anomalies already contained in the grain are likely to be retained through the conversion process, while others may be implanted by the shock if the grain is close to the supernova. The meteoritic diamonds are likely to be the results of transformation of carbon grains in grain-grain collisions in supernova shock waves.

  20. Magnetohydrodynamic shock waves in molecular clouds

    SciTech Connect

    Draine, B.T.; Roberge, W.G.; Dalgarno, A.

    1983-01-15

    The structure of shock waves in molecular clouds is calculated, including the effects of ion-neutral streaming driven by the magnetic field. It is found that shock waves in molecular clouds will usually be C-type shock waves, mediated entirely by the dissipation accompanying ion-neutral streaming, and in which all of the hydrodynamic variables are continuous. Detailed results are presented for magnetohydrodynamic shock waves propagating at speeds in the range of 5--50 km s/sup -1/ in molecular clouds with preshock densities n/sub H/ = 10/sup 2/, 10/sup 4/, and 10/sup 6/ cm/sup -3/. Graphs are constructed of the effective ''excitation temperatures'' of the rotational and vibrational levels of H/sub 2/ in the shocked gas. The effects of chemical changes in the composition of oxygen-bearing molecules are investigated, and the contributions to the cooling of the shocked gas by emission from H/sub 2/, CO, OH, and H/sub 2/O are evaluated. Predictions are made of the intensities of the rotation-vibration lines of H/sub 2/ and of the fine-structure lines of O I and C I. Magnetic fields may lead to a substantial increase in the limiting shock velocity above which dissociation of H/sub 2/ takes place: for a cloud of density eta/sub H/ = 10/sup 6/ cm/sup -3/, the limiting shock speed is approx.45 km s/sup -1/. The fractional ionization is a critical parameter affecting the shock structure, and the processes acting to change the ionization in the shock are examined. Magnetic field effects enhance the sputtering of grain mantles in dense gas: H/sub 2/O ice mantles can be substantially eroded in v/sub s/> or =25 km s/sup -1/ shock waves. Grain erosion may contribute to the enhancement of some molecular species in the shocked gas.

  1. The physics of interstellar shock waves

    NASA Technical Reports Server (NTRS)

    Shull, J. Michael; Draine, Bruce T.

    1987-01-01

    This review discusses the observations and theoretical models of interstellar shock waves, in both diffuse cloud and molecular cloud environments. It summarizes the relevant gas dynamics, atomic, molecular and grain processes, radiative transfer, and physics of radiative and magnetic precursors in shock models. It then describes the importance of shocks for observations, diagnostics, and global interstellar dynamics. It concludes with current research problems and data needs for atomic, molecular and grain physics.

  2. Interplanetary shock waves associated with solar flares

    NASA Technical Reports Server (NTRS)

    Chao, J. K.; Sakurai, K.

    1974-01-01

    The interaction of the earth's magnetic field with the solar wind is discussed with emphasis on the influence of solar flares. The geomagnetic storms are considerered to be the result of the arrival of shock wave generated by solar flares in interplanetary space. Basic processes in the solar atmosphere and interplanetary space, and hydromagnetic disturbances associated with the solar flares are discussed along with observational and theoretical problems of interplanetary shock waves. The origin of interplanetary shock waves is also discussed.

  3. Shock-activated electrochemical power supplies

    DOEpatents

    Benedick, W.B.; Graham, R.A.; Morosin, B.

    1987-04-20

    A shock-activated electrochemical power supply is provided which is initiated extremely rapidly and which has a long shelf life. Electrochemical power supplies of this invention are initiated much faster than conventional thermal batteries. Power supplies of this invention comprise an inactive electrolyte and means for generating a high-pressure shock wave such that the shock wave is propagated through the electrolyte rendering the electrolyte electrochemically active. 2 figs.

  4. Shock-activated electrochemical power supplies

    DOEpatents

    Benedick, William B.; Graham, Robert A.; Morosin, Bruno

    1988-01-01

    A shock-activated electrochemical power supply is provided which is initiated extremely rapidly and which has a long shelf life. Electrochemical power supplies of this invention are initiated much faster than conventional thermal batteries. Power supplies of this invention comprise an inactive electrolyte and means for generating a high-pressure shock wave such that the shock wave is propagated through the electrolytes rendering the electrolyte electrochemically active.

  5. Shock-activated electrochemical power supplies

    DOEpatents

    Benedick, W.B.; Graham, R.A.; Morosin, B.

    1988-11-08

    A shock-activated electrochemical power supply is provided which is initiated extremely rapidly and which has a long shelf life. Electrochemical power supplies of this invention are initiated much faster than conventional thermal batteries. Power supplies of this invention comprise an inactive electrolyte and means for generating a high-pressure shock wave such that the shock wave is propagated through the electrolytes rendering the electrolyte electrochemically active. 2 figs.

  6. Oblique interaction of waves with shocks

    NASA Astrophysics Data System (ADS)

    Morro, A.

    The oblique interaction between plane waves and shocks in materials described by a system of conservation equations is investigated. Two results are found. First, a straightforward geometric-kinematic analysis of the interaction yields a relation for each emergent mode (i.e., the outgoing wave) which determines the relation of propagation once the incident wave is given. Second, the shock may undergo an angular velocity which is ultimately related to the shock acceleration

  7. PIV tracer behavior on propagating shock fronts

    NASA Astrophysics Data System (ADS)

    Glazyrin, Fyodor N.; Mursenkova, Irina V.; Znamenskaya, Irina A.

    2016-01-01

    The present work was aimed at the quantitative particle image velocimetry (PIV) measurement of a velocity field near the front of a propagating shock wave and the study of the dynamics of liquid tracers crossing the shock front. For this goal, a shock tube with a rectangular cross-section (48  ×  24 mm) was used. The flat shock wave with Mach numbers M  =  1.4-2.0 propagating inside the tube channel was studied as well as an expanding shock wave propagating outside the channel with M  =  1.2-1.8 at its main axis. The PIV imaging of the shock fronts was carried out with an aerosol of dioctyl sebacate (DEHS) as tracer particles. The pressures of the gas in front of the shock waves studied ranged from 0.013 Mpa to 0.1 MPa in the series of experiments. The processed PIV data, compared to the 1D normal shock theory, yielded consistent values of wake velocity immediately behind the plain shock wave. Special attention was paid to the blurring of the velocity jump on the shock front due to the inertial particle lag and peculiarities of the PIV technique. A numerical algorithm was developed for analysis and correction of the PIV data on the shock fronts, based on equations of particle-flow interaction. By application of this algorithm, the effective particle diameter of the DEHS aerosol tracers was estimated as 1.03  ±  0.12 μm. A number of different formulations for particle drag were tested with this algorithm, with varying success. The results show consistency with previously reported experimental data obtained for cases of stationary shock waves.

  8. X-ray diffraction studies of shocked lunar analogs

    NASA Technical Reports Server (NTRS)

    Hanss, R. E.

    1979-01-01

    The X-ray diffraction experiments on shocked rock and mineral analogs of particular significance to lunar geology are described. Materials naturally shocked by meteorite impact, nuclear-shocked, or artificially shocked in a flat plate accelerator were utilized. Four areas were outlined for investigation: powder diffractometer studies of shocked single crystal silicate minerals (quartz, orthoclase, oligoclase, pyroxene), powder diffractometer studies of shocked polycrystalline monomineralic samples (dunite), Debye-Scherrer studies of single grains of shocked granodiorite, and powder diffractometer studies of shocked whole rock samples. Quantitative interpretation of peak shock pressures experienced by materials found in lunar or terrestrial impact structures is presented.

  9. Shock timing measurements and analysis in deuterium-tritium-ice layered capsule implosions on NIF

    SciTech Connect

    Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R.; Ross, J. S.; LePape, S.; Ralph, J. E.; Dewald, E. L.; Berzak Hopkins, L.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Landen, O. L.; Edwards, M. J.; Hohenberger, M.; Boehly, T. R.; Nikroo, A.

    2014-02-15

    Recent advances in shock timing experiments and analysis techniques now enable shock measurements to be performed in cryogenic deuterium-tritium (DT) ice layered capsule implosions on the National Ignition Facility (NIF). Previous measurements of shock timing in inertial confinement fusion implosions [Boehly et al., Phys. Rev. Lett. 106, 195005 (2011); Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] were performed in surrogate targets, where the solid DT ice shell and central DT gas were replaced with a continuous liquid deuterium (D2) fill. These previous experiments pose two surrogacy issues: a material surrogacy due to the difference of species (D2 vs. DT) and densities of the materials used and a geometric surrogacy due to presence of an additional interface (ice/gas) previously absent in the liquid-filled targets. This report presents experimental data and a new analysis method for validating the assumptions underlying this surrogate technique. Comparison of the data with simulation shows good agreement for the timing of the first three shocks, but reveals a considerable discrepancy in the timing of the 4th shock in DT ice layered implosions. Electron preheat is examined as a potential cause of the observed discrepancy in the 4th shock timing.

  10. Shock timing measurements and analysis in deuterium-tritium-ice layered capsule implosions on NIF

    NASA Astrophysics Data System (ADS)

    Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R.; Ross, J. S.; LePape, S.; Ralph, J. E.; Hohenberger, M.; Dewald, E. L.; Berzak Hopkins, L.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Boehly, T. R.; Nikroo, A.; Landen, O. L.; Edwards, M. J.

    2014-02-01

    Recent advances in shock timing experiments and analysis techniques now enable shock measurements to be performed in cryogenic deuterium-tritium (DT) ice layered capsule implosions on the National Ignition Facility (NIF). Previous measurements of shock timing in inertial confinement fusion implosions [Boehly et al., Phys. Rev. Lett. 106, 195005 (2011); Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] were performed in surrogate targets, where the solid DT ice shell and central DT gas were replaced with a continuous liquid deuterium (D2) fill. These previous experiments pose two surrogacy issues: a material surrogacy due to the difference of species (D2 vs. DT) and densities of the materials used and a geometric surrogacy due to presence of an additional interface (ice/gas) previously absent in the liquid-filled targets. This report presents experimental data and a new analysis method for validating the assumptions underlying this surrogate technique. Comparison of the data with simulation shows good agreement for the timing of the first three shocks, but reveals a considerable discrepancy in the timing of the 4th shock in DT ice layered implosions. Electron preheat is examined as a potential cause of the observed discrepancy in the 4th shock timing.

  11. Endoscopically-controlled electrohydraulic intracorporeal shock wave lithotripsy (EISL) of salivary stones.

    PubMed

    Königsberger, R; Feyh, J; Goetz, A; Kastenbauer, E

    1993-02-01

    Twenty-nine patients with salivary stones were treated with the endoscopically-controlled electrohydraulic shock wave lithotripsy (EISL). This new minimally invasive treatment of sialolithiasis is performed under local anesthesia on an outpatient basis with little inconvenience to the patient. For endoscopy, a flexible fibroscope with an additional probe to generate shock waves is placed into the submandibular duct and advanced until the stone is identified. For shock wave-induced stone disintegration, the probe electrode must be placed 1 mm in front of the concrement. The shock waves are generated by a sparkover at the tip of the probe. By means of the endoscopically-controlled shock wave lithotripsy it was possible to achieve complete stone fragmentation in 20 out of 29 patients without serious side effects. In three patients, only partial stone fragmentation could be achieved due to the stone quality. Endoscopically-controlled electrohydraulic intracorporeal shock wave lithotripsy represents a novel minimally invasive therapy for endoscopically accessible salivary gland stones. The advantage in comparison to the endoscopically-controlled laser lithotripsy will be discussed. PMID:8445694

  12. Raman spectroscopies in shock-compressed materials

    SciTech Connect

    Schmidt, S.C.; Moore, D.S.; Shaner, J.W.

    1983-01-01

    Spontaneous Raman spectroscopy, stimulated Raman scattering and coherent anti-Stokes Raman scattering have been used to measure temperatures and changes in molecular vibrational frequencies for detonating and shocked materials. Inverse Raman and Raman induced Kerr effect spectroscopies have been suggested as diagnostic probes for determining and phenomenology of shock-induced chemical reactions. The practicality, advantages, and disadvantages of using Raman scattering techniques as diagnostic probes of microscopic phenomenology through and immediately behind the shock front of shock-compressed molecular systems are discussed.

  13. Particle Acceleration in Slower SNR Shocks

    NASA Astrophysics Data System (ADS)

    Raymond, John

    Models predict that the acceleration efficiency of shock waves drops off as an SNR shock slows down, though this is partly offset by the increasing area of the shock front. Middle-aged SNRs emit pion-decay gamma rays, but it is not yet clear when during the SNR evolution the enegetic protons were produced. We examine observations of the Cygnus Loop to obtain some estimates of the cosmic ray acceleration efficiency in the 400 km/s shock of this older supernova remnant.

  14. Shock melting and vaporization of metals.

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.

    1972-01-01

    The effect of initial porosity on shock induction of melting and vaporization is investigated for Ba, Sr, Li, Fe, Al, U, and Th. For the less compressible of these metals, it is found that for a given strong shock-generation system (explosive in contact, or flyer-plate impact) an optimum initial specific volume exists such that the total entropy production, and hence the amount of metal liquid or vapor, is a maximum. Initial volumes from 1.4 to 2.0 times crystal volumes, depending on the metal sample and shock-inducing system, will result in optimum post-shock entropies.

  15. Laboratory Astrophysics: Study of Radiative Shocks

    NASA Astrophysics Data System (ADS)

    Leygnac, S.; Lanz, T.; Stehlé, C.; Michaut, C.

    2002-12-01

    Radiative shocks are high Mach number shocks with a strong coupling between radiation and hydrodynamics which leads to a structure governed by a radiative precursor. They might be encountered in various astrophysical systems: stellar accretion shocks, pulsating stars, interaction of supernovae with the intestellar medium etc. A numerical one dimensional (1D) stationary study of the coupling between hydrodynamics and radiative transfer is being performed. An estimate of the error made by the 1D approach in the radiative transfer treatment is done by an approximate short characteristics approach. It shows, for exemple, how much of the radiation escapes from the medium in the configuration of the experiment. The experimental study of these shocks has been performed with the high energy density laser of the LULI, at the École Polytechnique (France). We have observed several shocks identified as radiative shocks. The shock waves propagate at about 50 km/s in a tiny 10 mm3 shock tube filled with gaz. From the measurements, it is possible to infer several features of the shock such as the speed and the electronic density.

  16. Accretion shock geometries in the magnetic variables

    NASA Technical Reports Server (NTRS)

    Stockman, H. S.

    1988-01-01

    The first self consistent shock models for the AM Herculis-type systems successfully identified the dominant physical processes and their signatures. These homogenous shock models predict unpolarized, Rayleigh-Jeans optical spectra with sharp cutoffs and rising polarizations as the shocks become optically thin in the ultraviolet. However, the observed energy distributions are generally flat with intermediate polarizations over a broad optical band. These and other observational evidence support a non-homogenous accretion profile which may extend over a considerable fraction of the stellar surface. Both the fundamental assumptions underlying the canonical 1-D shock model and the extension of this model to inhomogenous accretion shocks were identified, for both radial and linear structures. The observational evidence was also examined for tall shocks and little evidence was found for relative shock heights in excess of h/R(1) greater than or equal to 0.1. For several systems, upper limits to the shock height can be obtained from either x ray or optical data. These lie in the region h/R(1) is approximately 0.01 and are in general agreement with the current physical picture for these systems. The quasi-periodic optical variations observed in several magnetic variables may eventually prove to be a major aid in further understanding their accretion shock geometries.

  17. Gigabar shock wave in a laboratory experiment

    NASA Astrophysics Data System (ADS)

    Gus'kov, S. Yu.

    2016-03-01

    The current status of research on generating a powerful shock wave with a pressure of up to several gigabars in a laboratory experiment is reviewed. The focus is on results which give a possibility of shock-wave experiments to study an equation of state of matter (EOS) at the level of gigabar pressure. The proposals are discussed to achieve a plane record-pressure shock wave driven by laser-accelerated fast electrons with respect to EOS-experiment as well as to prospective method of inertial fusion target (ICF) ignition as shock ignition.

  18. Explosive shocks in air (2nd edition)

    NASA Astrophysics Data System (ADS)

    Kinney, G. F.; Graham, K. J.

    After an initial qualitative characterization of the properties of explosions in the atmosphere and their blast and shock propagation effects, attention is given to the underlying quantitative principles of explosive energy release, including the scaling laws for explosions and internal blast effects from confined explosions. The dynamic loads that blast waves impose on representative structures are then characterized, with attention to resulting structural damage. A major feature of the present treatment is the use of the dimensionless Mach number in all shock equations; a further simplification is furnished by first developing mathematical equations for shock in steady flow, and then applying these equations to explosive shock by simple transformation of coordinates.

  19. Basic Shock Physiology and Critical Care.

    PubMed

    Roberts, Brian K

    2016-05-01

    Veterinarians practicing emergency medicine and/or working with exotic animals must be well versed in the pathophysiology of shock because many exotic pets present with an acute crisis or an acute manifestation of a chronic process causing poor organ perfusion. This article discusses the pathophysiology of shock and the systemic inflammatory response syndrome, which may lead to organ dysfunction, organ failure, sepsis, and death. The physiology of perfusion, perfusion measurements, categories of shock, and altered function of the immune system, gastrointestinal barrier, and coagulation system are discussed. Veterinarians providing emergency care to patients with shock must also be aware of comorbidities. PMID:27131156

  20. Viscous shock profiles and primitive formulations

    NASA Technical Reports Server (NTRS)

    Karni, S.

    1990-01-01

    Weak solutions of hyperbolic systems in primitive (non-conservation) form for which a consistent conservation form exists are considered. It is shown that primitive formulations, shock relations are not uniquely defined by the states to either side of the shock but also depend on the viscous path connecting the two. Scheme-dependent high order correction terms are derived that enforce consistent viscous shock profiles. The resulting primitive algorithm is conservative to the order of approximation. One dimensional Euler calculations of flows containing strong shocks clearly show that conservation errors in primitive flow calculations are of comparable quality.

  1. Shock Waves in Outflows from Young Stars

    NASA Astrophysics Data System (ADS)

    Hartigan, Patrick

    This review focuses on physics of the cooling zones behind radiative shocks and the emission line diagnostics that can be used to infer physical conditions and mass loss rates in jets from young stars. Spatial separations of the cooling zones from the shock fronts, now resolvable with HST, and recent evidence for C-shocks have greatly increased our understanding of how shocks in outflows interact with the surrounding medium and with other material within the flow. By combining multiple epoch HST images, one can create `movies' of flows like those produced from numerical codes, and learn what kinds of instabilities develop within these systems.

  2. The role of divergences for shock waves

    NASA Astrophysics Data System (ADS)

    Uribe, Francisco

    2013-11-01

    Several continuum theories for shock waves give rise to a set of differential equations in which the analysis of the underlying vector field can be done using the tools of the theory of dynamical systems. We illustrate the importance of the divergences associated with the vector field by considering the ideas by Maxwell and Cattaneo and applied them to study shock waves in dilute gases. Different theoretical descriptions for shock waves are mentioned and some of them are compared with experimental data and computer simulations. Our goal is to derive conditions under which the shock wave problem has a solution by analyzing the singularities of the vector field.

  3. Shock-induced defects in bulk materials

    SciTech Connect

    Gray, G.T.

    1998-03-01

    In this paper examples of the shock-induced defects produced during shock compression which correlate with microstructure/mechanical property changes induced in materials due to shock prestraining are discussed. The characteristics of the shock impulse(peak shock pressure, pulse duration, and rarefaction rate) imparted to the material under investigation and the shock-induced defects produced in numerous metals and alloys are compared with their deformation behavior at ordinary rates of deformation. Examples of the range of defects observed in shock-recovered metals and alloys, include: dislocations, deformation twins, point defects, and residual metastable remnants from pressure-induced phase transformations. Results concerning the influence of interstitial content on the propensity of {omega}-phase formation and its structure in high-purity and A-7O Ti are presented. The influence of shock-wave deformation on the phase stability and substructure evolution of high-purity (low-interstitial) titanium and A-7O (3,700 ppm oxygen) titanium were probed utilizing real-time velocity interferometry (VISAR) and soft shock-recovery techniques. Suppression of the {alpha}-{omega} pressure-induced phase transformation in A-70 Ti, containing a high interstitial oxygen content, is seen to simultaneously correspond with the suppression of deformation twinning.

  4. Thermal Shock-resistant Cement

    SciTech Connect

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  5. Electron physics in shock waves

    NASA Astrophysics Data System (ADS)

    Kilian, Patrick

    2014-05-01

    The non-relativistic shocks that we find in the solar wind (no matter if driven by CMEs or encounters with planets) are dominated by ion dynamics. Therefore a detailed treatment of electrons is often neglegted to gain significant reductions in computational effort. With recent super computers and massively parallel codes it is possible to perform self-consistent kinetic simulations using particle in cell code. This allows to study the heating of the electrons as well as the acceleration to superthermal energies. These energetic electrons are interesting for couple of reasons. e.g. as an influence on plasma instabilities or for the generation of plasma waves.

  6. Bacterial Heat Shock Protein Activity

    PubMed Central

    Maleki, Farajollah; Khosravi, Afra; Nasser, Ahmad; Taghinejad, Hamid

    2016-01-01

    Bacteria are exposed to different types of stress in their growth conditions. They have developed appropriate responses, modulated by the re-modeling of protein complexes and by phosphorylation dependent signal transduction systems, to adapt and to survive in a variety range of nature. Proteins are essential components for biologic activity in the eukaryotic and prokaryotic cell. Heat Shock Proteins (HSP) have been identified from various organisms and have critical role in cell hemostasis. Chaperone can sense environment and have different potential role in the organism evolution. PMID:27134861

  7. Adaptive inertial shock-absorber

    NASA Astrophysics Data System (ADS)

    Faraj, Rami; Holnicki-Szulc, Jan; Knap, Lech; Seńko, Jarosław

    2016-03-01

    This paper introduces and discusses a new concept of impact absorption by means of impact energy management and storage in dedicated rotating inertial discs. The effectiveness of the concept is demonstrated in a selected case-study involving spinning management, a recently developed novel impact-absorber. A specific control technique performed on this device is demonstrated to be the main source of significant improvement in the overall efficiency of impact damping process. The influence of various parameters on the performance of the shock-absorber is investigated. Design and manufacturing challenges and directions of further research are formulated.

  8. Automated shock detection and analysis algorithm for space weather application

    NASA Astrophysics Data System (ADS)

    Vorotnikov, Vasiliy S.; Smith, Charles W.; Hu, Qiang; Szabo, Adam; Skoug, Ruth M.; Cohen, Christina M. S.

    2008-03-01

    Space weather applications have grown steadily as real-time data have become increasingly available. Numerous industrial applications have arisen with safeguarding of the power distribution grids being a particular interest. NASA uses short-term and long-term space weather predictions in its launch facilities. Researchers studying ionospheric, auroral, and magnetospheric disturbances use real-time space weather services to determine launch times. Commercial airlines, communication companies, and the military use space weather measurements to manage their resources and activities. As the effects of solar transients upon the Earth's environment and society grow with the increasing complexity of technology, better tools are needed to monitor and evaluate the characteristics of the incoming disturbances. A need is for automated shock detection and analysis methods that are applicable to in situ measurements upstream of the Earth. Such tools can provide advance warning of approaching disturbances that have significant space weather impacts. Knowledge of the shock strength and speed can also provide insight into the nature of the approaching solar transient prior to arrival at the magnetopause. We report on efforts to develop a tool that can find and analyze shocks in interplanetary plasma data without operator intervention. This method will run with sufficient speed to be a practical space weather tool providing useful shock information within 1 min of having the necessary data to ground. The ability to run without human intervention frees space weather operators to perform other vital services. We describe ways of handling upstream data that minimize the frequency of false positive alerts while providing the most complete description of approaching disturbances that is reasonably possible.

  9. Investigation of shock focusing in a cavity with incident shock diffracted by an obstacle

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Chen, X.; He, L.-M.; Rong, K.; Deiterding, R.

    2016-05-01

    Experiments and numerical simulations were carried out in order to investigate the focusing of a shock wave in a test section after the incident shock has been diffracted by an obstacle. A conventional shock tube was used to generate the planar shock. Incident shock Mach numbers of 1.4 and 2.1 were tested. A high-speed camera was employed to obtain schlieren photos of the flow field in the experiments. In the numerical simulations, a weighted essentially non-oscillatory (WENO) scheme of third-order accuracy supplemented with structured dynamic mesh adaptation was adopted to simulate the shock wave interaction. Good agreement between experiments and numerical results is observed. The configurations exhibit shock reflection phenomena, shock-vortex interaction and—in particular—shock focusing. The pressure history in the cavity apex was recorded and compared with the numerical results. A quantitative analysis of the numerically observed shock reflection configurations is also performed by employing a pseudo-steady shock transition boundary calculation technique. Regular reflection, single Mach reflection and transitional Mach reflection phenomena are observed and are found to correlate well with analytic predictions from shock reflection theory.

  10. Characterizing interplanetary shocks for development and optimization of an automated solar wind shock detection algorithm

    NASA Astrophysics Data System (ADS)

    Cash, M. D.; Wrobel, J. S.; Cosentino, K. C.; Reinard, A. A.

    2014-06-01

    Human evaluation of solar wind data for interplanetary (IP) shock identification relies on both heuristics and pattern recognition, with the former lending itself to algorithmic representation and automation. Such detection algorithms can potentially alert forecasters of approaching shocks, providing increased warning of subsequent geomagnetic storms. However, capturing shocks with an algorithmic treatment alone is challenging, as past and present work demonstrates. We present a statistical analysis of 209 IP shocks observed at L1, and we use this information to optimize a set of shock identification criteria for use with an automated solar wind shock detection algorithm. In order to specify ranges for the threshold values used in our algorithm, we quantify discontinuities in the solar wind density, velocity, temperature, and magnetic field magnitude by analyzing 8 years of IP shocks detected by the SWEPAM and MAG instruments aboard the ACE spacecraft. Although automatic shock detection algorithms have previously been developed, in this paper we conduct a methodical optimization to refine shock identification criteria and present the optimal performance of this and similar approaches. We compute forecast skill scores for over 10,000 permutations of our shock detection criteria in order to identify the set of threshold values that yield optimal forecast skill scores. We then compare our results to previous automatic shock detection algorithms using a standard data set, and our optimized algorithm shows improvements in the reliability of automated shock detection.

  11. Bow Shock Leads the Way for a Speeding Hot Jupiter

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    As hot Jupiters whip around their host stars, their speeds can exceed the speed of sound in the surrounding material, theoretically causing a shock to form ahead of them. Now, a study has reported the detection of such a shock ahead of transiting exoplanet HD 189733b, providing a potential indicator of the remarkably strong magnetic field of the planet.Rushing PlanetsDue to their proximity to their hosts, hot Jupiters move very quickly through the stellar wind and corona surrounding the star. When this motion is supersonic, the material ahead of the planet can be compressed by a bow shock and for a transiting hot Jupiter, this shock will cross the face of the host star in advance of the planets transit.In a recent study, a team of researchers by Wilson Cauley of Wesleyan University report evidence of just such a pre-transit. The teams target is exoplanet HD 189733b, one of the closest hot Jupiters to our solar system. When the authors examined high-resolution transmission spectra of this system, they found that prior to the optical transit of the planet, there was a large dip in the transmission of the first three hydrogen Balmer lines. This could well be the absorption of an optically-thick bow shock as it moves past the face of the star.Tremendous MagnetismOperating under this assumption, the authors create a model of the absorption expected from a hot Jupiter transiting with a bow shock ahead of it. Using this model, they show that a shock leading the planet at a distance of 12.75 times the planets radius reproduces the key features of the transmission spectrum.This stand-off distance is surprisingly large. Assuming that the location of the bow shock is set by the point where the planets magnetospheric pressure balances the pressure of the stellar wind or corona that it passes through, the planetary magnetic field would have to be at least 28 Gauss. This is seven times the strength of Jupiters magnetic field!Understanding the magnetic fields of exoplanets is

  12. A numerical scheme for ionizing shock waves

    SciTech Connect

    Aslan, Necdet . E-mail: naslan@yeditepe.edu.tr; Mond, Michael

    2005-12-10

    A two-dimensional (2D) visual computer code to solve the steady state (SS) or transient shock problems including partially ionizing plasma is presented. Since the flows considered are hypersonic and the resulting temperatures are high, the plasma is partially ionized. Hence the plasma constituents are electrons, ions and neutral atoms. It is assumed that all the above species are in thermal equilibrium, namely, that they all have the same temperature. The ionization degree is calculated from Saha equation as a function of electron density and pressure by means of a nonlinear Newton type root finding algorithms. The code utilizes a wave model and numerical fluctuation distribution (FD) scheme that runs on structured or unstructured triangular meshes. This scheme is based on evaluating the mesh averaged fluctuations arising from a number of waves and distributing them to the nodes of these meshes in an upwind manner. The physical properties (directions, strengths, etc.) of these wave patterns are obtained by a new wave model: ION-A developed from the eigen-system of the flux Jacobian matrices. Since the equation of state (EOS) which is used to close up the conservation laws includes electronic effects, it is a nonlinear function and it must be inverted by iterations to determine the ionization degree as a function of density and temperature. For the time advancement, the scheme utilizes a multi-stage Runge-Kutta (RK) algorithm with time steps carefully evaluated from the maximum possible propagation speed in the solution domain. The code runs interactively with the user and allows to create different meshes to use different initial and boundary conditions and to see changes of desired physical quantities in the form of color and vector graphics. The details of the visual properties of the code has been published before (see [N. Aslan, A visual fluctuation splitting scheme for magneto-hydrodynamics with a new sonic fix and Euler limit, J. Comput. Phys. 197 (2004) 1

  13. Converging shocks in elastic-plastic solids.

    PubMed

    Ortega, A López; Lombardini, M; Hill, D J

    2011-11-01

    We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=e(s)(I(1))+e(h)(ρ,ς), where e(s) accounts for shear through the first invariant of the Cauchy-Green tensor, and e(h) represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., e(h)=e(h)(ρ), with a power-law dependence e(h) is proportional to ρ(α), shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M is proportional to [log(1/R)](α), independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M is proportional to R(-(s-1)) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part e(h) is that of an ideal gas, is also tested, recovering the strong-shock limit M is proportional to R(-(s-1)/n(γ)) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the

  14. Converging shocks in elastic-plastic solids

    NASA Astrophysics Data System (ADS)

    López Ortega, A.; Lombardini, M.; Hill, D. J.

    2011-11-01

    We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=es(I1)+eh(ρ,ς), where es accounts for shear through the first invariant of the Cauchy-Green tensor, and eh represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., eh=eh(ρ), with a power-law dependence eh∝ρα, shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M∝[log(1/R)]α, independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M∝R-(s-1) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part eh is that of an ideal gas, is also tested, recovering the strong-shock limit M∝R-(s-1)/n(γ) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the hydrostatic part of the energy essentially commands the strong-shock behavior, the shear

  15. Acceleration of positrons in supernova shocks

    NASA Technical Reports Server (NTRS)

    Ellison, Donald C.

    1992-01-01

    During this project we investigated the acceleration of leptons (electrons and positrons) in collisionless shock waves. In particular, we were interested in how leptons are accelerated in the blast waves existing in the remnants of supernova explosions. Supernova remnants (SNRs) have long been considered as the most likely source of galactic cosmic rays but no definite connection between SNRs and the cosmic rays seen at earth can be made. Only by understanding lepton acceleration in shocks can the rich SNR data base be properly used to understand cosmic ray origins. Our project was directed at the neglected aspects of lepton acceleration. We showed that the efficiency of lepton acceleration depended critically on the lepton injection energy. We showed that, even when infection effects are not important, that proton and lepton distribution functions produced by shocks are quite different in the critical energy range for producing the observed synchrotron emission. We also showed that transrelativistic effects produced proton spectra that were not in agreement with standard results from radio observations, but that the lepton spectra were, in fact, consistent with observations. We performed simulations of relativistic shocks (shocks where the flow speed is a sizable fraction of the speed of light) and discovered some interesting effects. We first demonstrated the power of the Monte Carlo technique by determining the shock jump conditions in relativistic shocks. We then proceeded to determine how relativistic shocks accelerate particles. We found that nonlinear relativistic shocks treat protons and leptons even more differently than nonrelativistic shocks. The transrelativistic effects on the shock structure from the heavy ion component reduces the lepton acceleration to a tiny fraction of the ion acceleration. This effect is dramatic even if high energy leptons (many times thermal energy) are injected, and was totally unexpected. Our results have important

  16. Shock Wave Technology and Application: An Update☆

    PubMed Central

    Rassweiler, Jens J.; Knoll, Thomas; Köhrmann, Kai-Uwe; McAteer, James A.; Lingeman, James E.; Cleveland, Robin O.; Bailey, Michael R.; Chaussy, Christian

    2012-01-01

    Context The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems. Objective To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies. Evidence acquisition We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy. Evidence synthesis Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60–80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures. Conclusions New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL. PMID:21354696

  17. Shocks, star formation and the JWST

    NASA Astrophysics Data System (ADS)

    Gusdorf, A.

    2015-12-01

    The interstellar medium (ISM) is constantly evolving due to unremitting injection of energy in various forms. Energetic radiation transfers energy to the ISM: from the UV photons, emitted by the massive stars, to X- and γ-ray ones. Cosmic rays are another source of energy. Finally, mechanical energy is injected through shocks or turbulence. Shocks are ubiquitous in the interstellar medium of galaxies. They are associated to star formation (through jets and bipolar outflows), life (via stellar winds), and death (in AGB stellar winds or supernovae explosion). The dynamical processes leading to the formation of molecular clouds also generate shocks where flows of interstellar matter collide. Because of their ubiquity, the study of interstellar shocks is also a useful probe to the other mechanisms of energy injection in the ISM. This study must be conducted in order to understand the evolution of the interstellar medium as a whole, and to address various questions: what is the peculiar chemistry associated to shocks, and what is their contribution to the cycle of matter in galaxies ? What is the energetic impact of shocks on their surroundings on various scales, and hence what is the feedback of stars on the galaxies ? What are the scenarios of star formation, whether this star formation leads to the propagation of shocks, or whether it is triggered by shock propagation ? What is the role of shocks in the acceleration of cosmic rays ? Can they shed light on their composition and diffusion processes ? In order to progress on these questions, it is paramount to interpret the most precise observations with the most precise models of shocks. From the observational point of view, the James Webb Space Telescope represents a powerful tool to better address the above questions, as it will allow to observe numerous shock tracers in the infrared range at an unprecedented spatial and spectral resolution.

  18. Very low shock release pyromechanisms

    NASA Astrophysics Data System (ADS)

    Soulier, Grégory; Gaechter, J. Pierre

    2003-09-01

    Pyromechanisms have long been used in space for launchers and satellites applications, particularly for release or separation purposes, such as bolt cutters, release nuts, pyrovalves, etc. They offer a great variety of uses, a high potential between the power supplied and the weight on board with, at the same time, a high reliability. However, they also feature a drawback due to the high dynamics generated by their functioning. Pyroshocks levels may damage adjacent sensible equipments (eg electronic boxes, reaction wheels,...) and require to design damping systems or to remove those equipments from the shock source. In a mechanism using standard pyrodevices, shock generation comes from three sources: 1. Pyrotechnic reaction. 2. Energy from internal parts in motion. 3. The release of structural constraints. Devices developed by E. LACROIX have the objectives to avoid the two last ones by: Using heat and gas generated by pyrotechnic effects. Reducing speed of parts in motion. Reducing release speed of mechanical constraints. In this paper, LACROIX presents two products named "PYROSOFT" and "VIROSOFT " designed by LACROIX and supported by CNES Toulouse (French Space Agency). R&T contracts.

  19. Shock compression profiles in ceramics

    SciTech Connect

    Grady, D.E.; Moody, R.L.

    1996-03-01

    An investigation of the shock compression properties of high-strength ceramics has been performed using controlled planar impact techniques. In a typical experimental configuration, a ceramic target disc is held stationary, and it is struck by plates of either a similar ceramic or by plates of a well-characterized metal. All tests were performed using either a single-stage propellant gun or a two-stage light-gas gun. Particle velocity histories were measured with laser velocity interferometry (VISAR) at the interface between the back of the target ceramic and a calibrated VISAR window material. Peak impact stresses achieved in these experiments range from about 3 to 70 GPa. Ceramics tested under shock impact loading include: Al{sub 2}O{sub 3}, AlN, B{sub 4}C, SiC, Si{sub 3}N{sub 4}, TiB{sub 2}, WC and ZrO{sub 2}. This report compiles the VISAR wave profiles and experimental impact parameters within a database-useful for response model development, computational model validation studies, and independent assessment of the physics of dynamic deformation on high-strength, brittle solids.

  20. Evidence for confinement of low-energy cosmic rays ahead of interplanetary shock waves.

    NASA Technical Reports Server (NTRS)

    Palmeira, R. A. R.; Allum, F. R.

    1973-01-01

    Short-lived (about 15 min), low-energy proton increases associated with the passage of interplanetary shock waves have been previously reported. In the present paper, we have examined in a fine time scale (about 1 min) the concurrent particle and magnetic field data, taken by detectors on Explorer 34, for four of these events. Our results further support the view that these impulsive events are due to confinement of the solar cosmic-ray particles in the region just ahead (about 1,000,000 km) of the advancing shock front.

  1. [Effects of cold-shock on the growth and flower bud differentiation of tomato seedlings under high temperature stress].

    PubMed

    Li, Sheng-li; Xia, Ya-zhen; Sun, Zhi-qiang

    2016-02-01

    In order to explore the effects of cold-shock on the growth and flower bud differentiation of tomato seedlings under high temperature, tomato seedlings were subjected to cold-shock treat- ments every day with 10 °C for 10 minutes in. an artificial climate chamber. Tomato seedlings were treated with cold-shock at the first true leaf stage and the treatment lasted for 15 days. Tomato seed- lings without cold-shock were used as control. At the fourth true leaf period of tomato seedlings, five plants were randomly sampled and the growth characteristics and the ultrastructure changes of meso- phyll cell of tomato seedlings were examined. The flower bud differentiation process of tomato seed- lings was observed at the periods of the second, fourth and sixth true leaves respectively. Flowering and fruiting of tomato seedlings were also investigated after transplanting. The results showed that the stem diameter and health index of tomato seedlings with cold-shock were enhanced by 7.2% and 55.5% compared with seedlings without cold-shock. Mesophyll cells of the seedlings with cold-shock arranged loosely and various organelles such as chloroplasts and mitochondria were morphologically integrated, while chloroplasts and mitochondria of seedlings mesophyll cells without cold-shock swelled up and thylakoids vacuolized apparently. The flower bud differentiation process of seedlings with cold-shock could be advanced significantly at the early seedling stage compared with the control and the advancement was weakened with the seedling growing. Fruit set number and percentage on the first and second inflorescence of tomato plants transplanted by seedlings with cold-shock were enhanced significantly compared with those of the control. These results indicated that the injury of membrane structure of various organelles, especially chloroplast and mitochondria could be allevia- ted by cold-shock treatment under high temperature tress. Cold-shock treatment could not only im- prove the

  2. Clinical application of extracorporeal shock wave therapy in orthopedics: focused versus unfocused shock waves.

    PubMed

    Foldager, Casper Bindzus; Kearney, Cathal; Spector, Myron

    2012-10-01

    For the past decade extracorporeal shock wave therapy has been applied to a wide range of musculoskeletal disorders. The many promising results and the introduction of shock wave generators that are less expensive and easier to handle has added to the growing interest. Based on their nature of propagation, shock waves can be divided into two types: focused and unfocused. Although several physical differences between these different types of shock waves have been described, very little is known about the clinical outcome using these different modalities. The aim of the present review is to investigate differences in outcome in select orthopaedic applications using focused and unfocused shock waves. PMID:22920552

  3. Development of a shock noise prediction code for high-speed helicopters - The subsonically moving shock

    NASA Technical Reports Server (NTRS)

    Tadghighi, H.; Holz, R.; Farassat, F.; Lee, Yung-Jang

    1991-01-01

    A previously defined airfoil subsonic shock-noise prediction formula whose result depends on a mapping of the time-dependent shock surface to a time-independent computational domain is presently coded and incorporated in the NASA-Langley rotor-noise prediction code, WOPWOP. The structure and algorithms used in the shock-noise prediction code are presented; special care has been taken to reduce computation time while maintaining accuracy. Numerical examples of shock-noise prediction are presented for hover and forward flight. It is confirmed that shock noise is an important component of the quadrupole source.

  4. Optical observation of shock waves and cavitation bubbles in high intensity laser-induced shock processes

    SciTech Connect

    Marti-Lopez, L.; Ocana, R.; Porro, J. A.; Morales, M.; Ocana, J. L.

    2009-07-01

    We report an experimental study of the temporal and spatial dynamics of shock waves, cavitation bubbles, and sound waves generated in water during laser shock processing by single Nd:YAG laser pulses of nanosecond duration. A fast ICCD camera (2 ns gate time) was employed to record false schlieren photographs, schlieren photographs, and Mach-Zehnder interferograms of the zone surrounding the laser spot site on the target, an aluminum alloy sample. We recorded hemispherical shock fronts, cylindrical shock fronts, plane shock fronts, cavitation bubbles, and phase disturbance tracks.

  5. Plasma Shock Wave Modification Experiments in a Temperature Compensated Shock Tube

    NASA Technical Reports Server (NTRS)

    Vine, Frances J.; Mankowski, John J.; Saeks, Richard E.; Chow, Alan S.

    2003-01-01

    A number of researchers have observed that the intensity of a shock wave is reduced when it passes through a weakly ionized plasma. While there is little doubt that the intensity of a shock is reduced when it propagates through a weakly ionized plasma, the major question associated with the research is whether the reduction in shock wave intensity is due to the plasma or the concomitant heating of the flow by the plasma generator. The goal of this paper is to describe a temperature compensated experiment in a "large" diameter shock tube with an external heating source, used to control the temperature in the shock tube independently of the plasma density.

  6. Post-shock relaxation in crystalline nitromethane

    NASA Astrophysics Data System (ADS)

    Rivera-Rivera, Luis A.; Sewell, Thomas D.; Thompson, Donald L.

    2013-02-01

    Molecular dynamics simulations of shocked (100)-oriented crystalline nitromethane were carried out to determine the rates of relaxation behind the shock wave. The forces were described by the fully flexible non-reactive Sorescu-Rice-Thompson force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)], 10.1021/jp000942q. The time scales for local and overall thermal equilibration in the shocked crystal were determined. The molecular center-of-mass and atomic kinetic energy distributions rapidly reach substantially different local temperatures. Several picoseconds are required for the two distributions to converge, corresponding to establishment of thermal equilibrium in the shocked crystal. The decrease of the molecular center-of-mass temperature and the increase of the atomic temperature behind the shock front exhibit essentially exponential dependence on time. Analysis of covalent bond distance distributions ahead of, immediately behind, and well behind the shock front showed that the effective bond stretching potentials are essentially harmonic. Effective force constants for the C-N, C-H, and N-O bonds immediately behind the shock front are larger by factors of 1.6, 2.5, and 2.0, respectively, than in the unshocked crystal; and by factors of 1.2, 2.2, and 1.7, respectively, compared to material sufficiently far behind the shock front to be essentially at thermal equilibrium.

  7. International HPT: Rx for Culture Shock.

    ERIC Educational Resources Information Center

    Carey, Clare Elizabeth

    1999-01-01

    Examines the cultural adaptation process experienced by people working in foreign environments. Reviews current organizational gaps in managing cross-cultural challenges; examines the phenomenon of culture shock; and presents a model for applying HPT (human performance technology) strategies to change culture shock to cross-cultural competence.…

  8. Computing unsteady shock waves for aeroacoustic applications

    NASA Technical Reports Server (NTRS)

    Meadows, Kristine R.; Caughey, David A.; Casper, Jay

    1994-01-01

    The computation of unsteady shock waves, which contribute significantly to noise generation in supersonic jet flows, is investigated. The paper focuses on the difficulties of computing slowly moving shock waves. Numerical error is found to manifest itself principally as a spurious entropy wave. Calculations presented are performed using a third-order essentially nonoscillatory scheme. The effect of stencil biasing parameters and of two versions of numerical flux formulas on the magnitude of spurious entropy are investigated. The level of numerical error introduced in the calculation is quantified as a function of shock pressure ratio, shock speed, Courant number, and mesh density. The spurious entropy relative to the entropy jump across a static shock decreases with increasing shock strength and shock velocity relative to the grid, but is insensitive to Courant number. The structure of the spurious entropy wave is affected by the choice of flux formulas and algorithm biasing parameters. The effect of the spurious numerical waves on the calculation of sound amplification by a shock wave is investigated. For this class of problem, the acoustic pressure waves are relatively unaffected by the spurious numerical phenomena.

  9. Computing unsteady shock waves for aeroacoustic applications

    NASA Technical Reports Server (NTRS)

    Meadows,, Kristine r.; Caughey, David A.; Casper, Jay

    1994-01-01

    The computation of unsteady shock waves, which contribute significantly to noise generation in supersonic jet flows, is investigated. This paper focuses on the difficulties of computing slowly moving shock waves. Numerical error is found to manifest itself principally as a spurious entropy wave. Calculations presented are performed using a third order essentially nonoscillatory scheme. The effect of stencil biasing parameters and of two versions of numerical flux formulas on the magnitude of spurious entropy are investigated. The level of numerical error introduced in the calculation in quantified as a function of shock pressure ratio, shock speed, Courant number, and mesh density. The spurious entropy relative to the entropy jump across a static shock decreases with increasing shock strength and shock velocity relative to the grid, but is insensitive to Courant number. The structure of the spurious entropy wave is affected by the choice of flux formulas and algorithm biasing parameters. The effect of the spurious numerical waves on the calculation of sound amplification by a shock wave is investigated. For this class of problem, the acoustic pressure waves are relatively unaffected by the spurious numerical phenomena.

  10. Biological Effects of Shock Waves on Infection

    NASA Astrophysics Data System (ADS)

    Gnanadhas, Divya Prakash; Janardhanraj, S.; Chakravortty, Dipshikha; Gopalan, Jagadeesh

    Shock waves have been successfully used for disintegrating kidney stones[1], noninvasive angiogenic approach[2] and for the treatment of osteoporosis[3]. Recently shock waves have been used to treat different medical conditions including intestinal anastomosis[4], wound healing[5], Kienböck's disease[6] and articular cartilage defects[7].

  11. Shock wave diagnostics using fluorescent dye probes

    NASA Astrophysics Data System (ADS)

    Banishev, Alexandr; Christensen, James; Dlott, Dana

    2015-06-01

    Fluorescent probes are highly developed, and have found increasing use in a wide variety of applications. We have studied shock compression of various materials with embedded dye probes used as high speed probes of pressure and temperature. Under the right conditions, dye emission can be used to make a map of the pressure distribution in shocked microstructured materials with high time (1 ns) and space (1 micrometer) resolution. In order to accomplish this goal, we started by studying shock compression of PMMA polymer with rhodamine 6G dye (R6G), as a function of shock pressure and shock duration. We observed the shock-induced spectral redshift and the shock-induced intensity loss. We investigated the fundamental mechanisms of R6G response to pressure. We showed that the time response of a dye probe is limited by its photophysical behavior under shock. We developed superemissive ultrafast dye probes by embedding R6G in a silica nanoparticle. More recently, we have searched for dye probes that have better responses. For instance, we have found that the dye Nile Red embedded in the right polymer matrix has 1.7 times larger pressure-induced redshift than R6G.

  12. Thermal shock resistance of ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Carper, D. M.; Nied, H. F.

    1993-01-01

    The experimental and analytical investigation of the thermal shock phenomena in ceramic matrix composites is detailed. The composite systems examined were oxide-based, consisting of an aluminosilicate matrix with either polycrystalline aluminosilicate or single crystal alumina fiber reinforcement. The program was divided into three technical tasks; baseline mechanical properties, thermal shock modeling, and thermal shock testing. The analytical investigation focused on the development of simple expressions for transient thermal stresses induced during thermal shock. The effect of various material parameters, including thermal conductivity, elastic modulus, and thermal expansion, were examined analytically for their effect on thermal shock performance. Using a simple maximum stress criteria for each constituent, it was observed that fiber fracture would occur only at the most extreme thermal shock conditions and that matrix fracture, splitting parallel to the reinforcing fiber, was to be expected for most practical cases. Thermal shock resistance for the two material systems was determined experimentally by subjecting plates to sudden changes in temperature on one surface while maintaining the opposite surface at a constant temperature. This temperature change was varied in severity (magnitude) and in number of shocks applied to a given sample. The results showed that for the most severe conditions examined that only surface matrix fracture was present with no observable fiber fracture. The impact of this damage on material performance was limited to the matrix dominated properties only. Specifically, compression strength was observed to decrease by as much as 50 percent from the measured baseline.

  13. Going to Teach in Prisons: Culture Shock

    ERIC Educational Resources Information Center

    Wright, Randall

    2005-01-01

    Novice prison teachers experience confusion and disorientation--culture shock--when they go to teach in prison because teaching and prison cultures collide. The stages of acculturation associated with culture shock are predictable and so are the identities and experiences of teachers who are positioned by the cultural dynamics of prison teaching.…

  14. The shock Hugoniot of glass microballoons

    SciTech Connect

    Simpson, R.; Helm, F.

    1994-12-01

    Shock Hugoniot measurements were made on glass microballoons. Input pressures ranging from 0.37-3.9 GPa produced compression from 860-690%. The Hugoniot curves were found to be anomalous in that the density shocked to decreases with increasing pressure.

  15. Theoretical and Experimental Studies of Radiative Shocks

    NASA Astrophysics Data System (ADS)

    Michaut, C.; Vinci, T.; Boireau, L.; Koenig, M.; Bouquet, S.; Benuzzi-Mounaix, A.; Osaki, N.; Herpe, G.; Falize, E.; Loupias, B.; Atzeni, S.

    2007-01-01

    This paper deals with the radiative shock from both theoretical and numerical points of view. It is based on the whole experimental results obtained at Laboratoire d'Utilisation des Lasers Intenses (LULI, École Polytechnique). Radiative shocks are high-Mach number shocks with a strong coupling between radiation and hydrodynamics which leads to a structure governed by a radiative precursor. These shocks are involved in various astrophysical systems: stellar accretion shocks, pulsating stars, interaction between supernovae and the interstellar medium. In laboratory, these radiative shocks are generated using high power lasers. New diagnostics have been implemented to study the geometrical shape of the shock and the front shock density. Data were obtained varying initial conditions for different laser intensities and temperature. The modeling of these phenomena is mainly performed through numerical simulations (1D and 2D) and analytical studies. We exhibit results obtained from several radiative hydrodynamics codes. As a result, it is possible to discuss about the influence of the geometry and physical parameters introduced in the 1D and 2D models.

  16. Benjamin Franklin and Shock-Induced Amnesia

    ERIC Educational Resources Information Center

    Finger, Stanley; Zaromb, Franklin

    2006-01-01

    Shock-induced amnesia received considerable attention after Cerletti popularized electroconvulsive shock therapy in the late 1930s. Yet, often overlooked is the fact that Benjamin Franklin recognized that passing electricity through the head could affect memory for the traumatic event. Franklin described his findings on himself and others in…

  17. Floating shock fitting via Lagrangian adaptive meshes

    NASA Technical Reports Server (NTRS)

    Vanrosendale, John

    1994-01-01

    In recent works we have formulated a new approach to compressible flow simulation, combining the advantages of shock-fitting and shock-capturing. Using a cell-centered Roe scheme discretization on unstructured meshes, we warp the mesh while marching to steady state, so that mesh edges align with shocks and other discontinuities. This new algorithm, the Shock-fitting Lagrangian Adaptive Method (SLAM) is, in effect, a reliable shock-capturing algorithm which yields shock-fitted accuracy at convergence. Shock-capturing algorithms like this, which warp the mesh to yield shock-fitted accuracy, are new and relatively untried. However, their potential is clear. In the context of sonic booms, accurate calculation of near-field sonic boom signatures is critical to the design of the High Speed Civil Transport (HSCT). SLAM should allow computation of accurate N-wave pressure signatures on comparatively coarse meshes, significantly enhancing our ability to design low-boom configurations for high-speed aircraft.

  18. 33 CFR 159.105 - Shock test.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Shock test. 159.105 Section 159.105 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.105 Shock test. The device, with...

  19. 33 CFR 159.105 - Shock test.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Shock test. 159.105 Section 159.105 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.105 Shock test. The device, with...

  20. Precursors to Interstellar Shocks of Solar Origin

    NASA Astrophysics Data System (ADS)

    Gurnett, D. A.; Kurth, W. S.; Stone, E. C.; Cummings, A. C.; Krimigis, S. M.; Decker, R. B.; Ness, N. F.; Burlaga, L. F.

    2015-12-01

    On or about 2012 August 25, the Voyager 1 spacecraft crossed the heliopause into the nearby interstellar plasma. In the nearly three years that the spacecraft has been in interstellar space, three notable particle and field disturbances have been observed, each apparently associated with a shock wave propagating outward from the Sun. Here, we present a detailed analysis of the third and most impressive of these disturbances, with brief comparisons to the two previous events, both of which have been previously reported. The shock responsible for the third event was first detected on 2014 February 17 by the onset of narrowband radio emissions from the approaching shock, followed on 2014 May 13 by the abrupt appearance of intense electron plasma oscillations generated by electrons streaming outward ahead of the shock. Finally, the shock arrived on 2014 August 25, as indicated by a jump in the magnetic field strength and the plasma density. Various disturbances in the intensity and anisotropy of galactic cosmic rays were also observed ahead of the shock, some of which are believed to be caused by the reflection and acceleration of cosmic rays by the magnetic field jump at the shock, and/or by interactions with upstream plasma waves. Comparisons to the two previous weaker events show somewhat similar precursor effects, although differing in certain details. Many of these effects are very similar to those observed in the region called the "foreshock" that occurs upstream of planetary bow shocks, only on a vastly larger spatial scale.

  1. Precursors To Interstellar Shocks of Solar Origin

    NASA Astrophysics Data System (ADS)

    Gurnett, D. A.; Kurth, W. S.; Stone, E. C.; Cummings, A. C.; Krimigis, S. M.; Decker, R. B.; Ness, N. F.; Burlaga, L. F.

    2015-08-01

    On or about 2012 August 25, the Voyager 1 spacecraft crossed the heliopause into the nearby interstellar plasma. In the nearly three years that the spacecraft has been in interstellar space, three notable particle and field disturbances have been observed, each apparently associated with a shock wave propagating outward from the Sun. Here, we present a detailed analysis of the third and most impressive of these disturbances, with brief comparisons to the two previous events, both of which have been previously reported. The shock responsible for the third event was first detected on 2014 February 17 by the onset of narrowband radio emissions from the approaching shock, followed on 2014 May 13 by the abrupt appearance of intense electron plasma oscillations generated by electrons streaming outward ahead of the shock. Finally, the shock arrived on 2014 August 25, as indicated by a jump in the magnetic field strength and the plasma density. Various disturbances in the intensity and anisotropy of galactic cosmic rays were also observed ahead of the shock, some of which are believed to be caused by the reflection and acceleration of cosmic rays by the magnetic field jump at the shock, and/or by interactions with upstream plasma waves. Comparisons to the two previous weaker events show somewhat similar precursor effects, although differing in certain details. Many of these effects are very similar to those observed in the region called the “foreshock” that occurs upstream of planetary bow shocks, only on a vastly larger spatial scale.

  2. Hydrodynamic Simulations of Gaseous Argon Shock Experiments

    NASA Astrophysics Data System (ADS)

    Garcia, Daniel; Dattelbaum, Dana; Goodwin, Peter; Morris, John; Sheffield, Stephen; Burkett, Michael

    2015-06-01

    The lack of published Argon gas shock data motivated an evaluation of the Argon Equation of State (EOS) in gas phase initial density regimes never before reached. In particular, these regimes include initial pressures in the range of 200-500 psi (0.025 - 0.056 g/cc) and initial shock velocities around 0.2 cm/ μs. The objective of the numerical evaluation was to develop a physical understanding of the EOS behavior of shocked and subsequently multiply re-shocked Argon gas initially pressurized to 200-500 psi through Pagosa numerical hydrodynamic simulations utilizing the SESAME equation of state. Pagosa is a Los Alamos National Laboratory 2-D and 3-D Eulerian hydrocode capable of modeling high velocity compressible flow with multiple materials. The approach involved the use of gas gun experiments to evaluate the shock and multiple re-shock behavior of pressurized Argon gas to validate Pagosa simulations and the SESAME EOS. Additionally, the diagnostic capability within the experiments allowed for the EOS to be fully constrained with measured shock velocity, particle velocity and temperature. The simulations demonstrate excellent agreement with the experiments in the shock velocity/particle velocity space, but note unanticipated differences in the ionization front temperatures.

  3. Instability of spherically imploding shock waves

    SciTech Connect

    Chen, H.; Hilko, B.; Zhang, L.; Panarella, E.

    1995-12-31

    The importance of spherically imploding shock waves has increased recently due to their particular applications in inertial confinement fusion (ICF) and the Spherical Pinch (SP). In particular, the stability of spherically imploding shock waves plays a critical role in the ultimate success of ICF and SP. The instability of spherically imploding shock waves is now systematically investigated. The basic state is Guderley and Landau`s unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandresakhar`s approach to the stability of spherical flames together. The governing equations for disturbances are derived and they use the condition that perturbed gas flow is potential. The three dimensional perturbation velocity profile and a shock front perturbation are solved by using the kinematic and dynamic boundary conditions in the shock front. The time-dependent amplitudes of the perturbations are obtained by solving the system of ordinary differential equations. This enables them to study the time history of the spherically imploding shock wave subject to perturbations. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. Preliminary results are presented.

  4. Relativistic shock propagation in nonuniform media

    NASA Astrophysics Data System (ADS)

    Gnatyk, B. I.

    1985-10-01

    Strong shocks will propagate in much the same way whether they are non- or ultrarelativistic. An approximate law is proposed to describe the motion of a strong, adiabatic, arbitrarily relativistic shock through an initially nonrelativistic medium having any desired density distribution.

  5. Shock-induced arrhythmogenesis in the myocardium

    NASA Astrophysics Data System (ADS)

    Trayanova, Natalia; Eason, James

    2002-09-01

    The focus of this article is the investigation of the electrical behavior of the normal myocardium following the delivery of high-strength defibrillation shocks. To achieve its goal, the study employs a complex three-dimensional defibrillation model of a slice of the canine heart characterized with realistic geometry and fiber architecture. Defibrillation shocks of various strengths and electrode configurations are delivered to the model preparation in which a sustained ventricular tachycardia is induced. Instead of analyzing the post-shock electrical events as progressions of transmembrane potential maps, the study examines the evolution of the postshock phase singularities (PSs) which represent the organizing centers of reentry. The simulation results demonstrate that the shock induces numerous PSs the majority of which vanish before the reentrant wavefronts associated with them complete half of a single rotation. Failed shocks are characterized with one or more PSs that survive the initial period of PS annihilation to establish a new postshock arrhythmia. The increase in shock strength results in an overall decrease of the number of PSs that survive over 200 ms after the end of the shock; however, the exact behavior of the PSs is strongly dependent on the shock electrode configuration.

  6. Advances in implantable cardioverter defibrillator therapy.

    PubMed

    Rickard, John; Wilkoff, Bruce L

    2016-03-01

    Since the first implant in 1980, implantable cardioverter defibrillator (ICD) technology has progressed rapidly. Modern ICD's have hundreds of programmable options with the general goal of preventing inappropriate shocks and providing shocks for truly life threatening symptomatic ventricular arrhythmias. New studies on ICD programming have shown the benefits of prolonged detection intervals in reaching this goal. Anti-tachycardia pacing (ATP) therapy has become an important adjunct to defibrillator shocks. Remote monitoring technologies have surfaced which have been shown to identify arrhythmias and problems with the device in an expedient fashion. The subcutaneous ICD offers the advantage of avoiding intravascular leads and their inherent risks. Lastly, the current understanding of the effects of MRI in ICD patients has advanced creating new opportunities to provide MRI safely to such patients. PMID:26653411

  7. The influence of incident shock Mach number on radial incident shock wave focusing

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Tan, Sheng; He, Liming; Rong, Kang; Zhang, Qiang; Zhu, Xiaobin

    2016-04-01

    Experiments and numerical simulations were carried out to investigate radial incident shock focusing on a test section where the planar incident shock wave was divided into two identical ones. A conventional shock tube was used to generate the planar shock. Incident shock Mach number of 1.51, 1.84 and 2.18 were tested. CCD camera was used to obtain the schlieren photos of the flow field. Third-order, three step strong-stability-preserving (SSP) Runge-Kutta method, third-order weighed essential non-oscillation (WENO) scheme and adaptive mesh refinement (AMR) algorithm were adopted to simulate the complicated flow fields characterized by shock wave interaction. Good agreement between experimental and numerical results was observed. Complex shock wave configurations and interactions (such as shock reflection, shock-vortex interaction and shock focusing) were observed in both the experiments and numerical results. Some new features were observed and discussed. The differences of structure of flow field and the variation trends of pressure were compared and analyzed under the condition of different Mach numbers while shock wave focusing.

  8. Whistler Waves Associated with Weak Interplanetary Shocks

    NASA Technical Reports Server (NTRS)

    Velez, J. C. Ramirez; Blanco-Cano, X.; Aguilar-Rodriguez, E.; Russell, C. T.; Kajdic, P.; Jian,, L. K.; Luhmann, J. G.

    2012-01-01

    We analyze the properties of 98 weak interplanetary shocks measured by the dual STEREO spacecraft over approximately 3 years during the past solar minimum. We study the occurrence of whistler waves associated with these shocks, which on average are high beta shocks (0.2 < Beta < 10). We have compared the waves properties upstream and downstream of the shocks. In the upstream region the waves are mainly circularly polarized, and in most of the cases (approx. 75%) they propagate almost parallel to the ambient magnetic field (<30 deg.). In contrast, the propagation angle with respect to the shock normal varies in a broad range of values (20 deg. to 90 deg.), suggesting that they are not phase standing. We find that the whistler waves can extend up to 100,000 km in the upstream region but in most cases (88%) are contained in a distance within 30,000 km from the shock. This corresponds to a larger region with upstream whistlers associated with IP shocks than previously reported in the literature. The maximum amplitudes of the waves are observed next to the shock interface, and they decrease as the distance to the shock increases. In most cases the wave propagation direction becomes more aligned with the magnetic field as the distance to the shock increases. These two facts suggest that most of the waves in the upstream region are Landau damping as they move away from the shock. From the analysis we also conclude that it is likely that the generation mechanism of the upstream whistler waves is taking place at the shock interface. In the downstream region, the waves are irregularly polarized, and the fluctuations are very compressive; that is, the compressive component of the wave clearly dominates over the transverse one. The majority of waves in the downstream region (95%) propagate at oblique angles with respect to the ambient magnetic field (>60 deg.). The wave propagation with respect to the shock-normal direction has no preferred direction and varies similarly to

  9. Nondiscriminated avoidance of shock by pigeons pecking a key1

    PubMed Central

    Ferrari, Elenice A.; Todorov, João Claudio; Graeff, Frederico Guilherme

    1973-01-01

    Four pigeons were trained to avoid shock by pecking a key on a free-operant avoidance schedule in which no exteroceptive stimulus signalled impending shock. Response rate was an inverse function of response-shock interval when shock-shock interval was held constant at 2 sec and response-shock intervals varied from 5 to 40 sec. Amphetamine increased response rates in two subjects and reserpine markedly reduced responding in one. PMID:16811659

  10. Shock loading predictions from application of indicial theory to shock-turbulence interactions

    NASA Technical Reports Server (NTRS)

    Keefe, Laurence R.; Nixon, David

    1991-01-01

    A sequence of steps that permits prediction of some of the characteristics of the pressure field beneath a fluctuating shock wave from knowledge of the oncoming turbulent boundary layer is presented. The theory first predicts the power spectrum and pdf of the position and velocity of the shock wave, which are then used to obtain the shock frequency distribution, and the pdf of the pressure field, as a function of position within the interaction region. To test the validity of the crucial assumption of linearity, the indicial response of a normal shock is calculated from numerical simulation. This indicial response, after being fit by a simple relaxation model, is used to predict the shock position and velocity spectra, along with the shock passage frequency distribution. The low frequency portion of the shock spectra, where most of the energy is concentrated, is satisfactorily predicted by this method.

  11. Heat-shock Proteins and Photodynamic Therapy

    NASA Astrophysics Data System (ADS)

    Baylis, Joanne; Downs, Craig A.; Jones, Linda R.; Heckathorn, Scott A.

    1998-11-01

    Many cancer treatments, such as photodynamic therapy, generate active oxygen species, often in the mitochondria. These oxygen species adversely react with cellular processes, thereby destroying cancer cells and tissue. Heat-shock proteins are up-regulated in response to heat stress or other environmental stresses and are known to protect cells from active oxygen species. In tumor cells, heat-shock proteins accumulate in the mitochondria under non-stress conditions at higher levels than in normal cells. The objective of our work is to determine whether specific mitochondrial heat-shock proteins are responsible for the increased resistance of cancer cells to oxidative-based anti-cancer therapies. We will first determine which heat-shock proteins accumulate in the mitochondria of cancer cells (lung carcinomas). We will determine if the over-expression of specific heat-shock proteins in the mitochondria can protect cells from Photofrin®-mediated photodynamic therapy through protection of mitochondrial electron transport.

  12. Mass-loading at interplanetary shocks

    NASA Technical Reports Server (NTRS)

    Zank, G. P.

    1992-01-01

    Mass-loading fronts represent a new class of shocks which is found frequently in the solar system, both at the head of comets and upstream of weakly and nonmagnetized planets, and which has not yet been investigated in great detail. Here, a general theoretical description of mass-loading shocks (MLSs) in the heliosphere is presented and the difference between MLSs and classical nonreacting MHD shock are elucidated. It is found that the momentum contribution of added mass within the shock represents a physically important effect, particularly in the shock strength regime observed at Comets Halley and GZ. The mass-loading MHD Rankine-Hugoniot conditions are not tangentially invariant, so mass-loading fronts are subjected to shearing stresses, greatly curtailing the upstream parameter regime for which stable transitions are possible. The existence of fast and slow mode compound mass-loading fronts is predicted. Other forms of mass-loading fronts exist for which no classical MHD counterparts exist.

  13. Supermagnetosonic Jets behind a Collisionless Quasiparallel Shock

    SciTech Connect

    Hietala, H.; Vainio, R.; Laitinen, T. V.; Vaivads, A.; Andreeova, K.; Palmroth, M.; Pulkkinen, T. I.; Koskinen, H. E. J.; Lucek, E. A.; Reme, H.

    2009-12-11

    The downstream region of a collisionless quasiparallel shock is structured containing bulk flows with high kinetic energy density from a previously unidentified source. We present Cluster multispacecraft measurements of this type of supermagnetosonic jet as well as of a weak secondary shock front within the sheath, that allow us to propose the following generation mechanism for the jets: The local curvature variations inherent to quasiparallel shocks can create fast, deflected jets accompanied by density variations in the downstream region. If the speed of the jet is super(magneto)sonic in the reference frame of the obstacle, a second shock front forms in the sheath closer to the obstacle. Our results can be applied to collisionless quasiparallel shocks in many plasma environments.

  14. A midsummer-night's shock wave

    NASA Astrophysics Data System (ADS)

    Hargather, Michael; Liebner, Thomas; Settles, Gary

    2007-11-01

    The aerial pyrotechnic shells used in professional display fireworks explode a bursting charge at altitude in order to disperse the ``stars'' of the display. The shock wave from the bursting charge is heard on the ground as a loud report, though it has by then typically decayed to a mere sound wave. However, viewers seated near the standard safety borders can still be subjected to weak shock waves. These have been visualized using a large, portable, retro-reflective ``Edgerton'' shadowgraph technique and a high-speed digital video camera. Images recorded at 10,000 frames per second show essentially-planar shock waves from 10- and 15-cm firework shells impinging on viewers during the 2007 Central Pennsylvania July 4th Festival. The shock speed is not measurably above Mach 1, but we nonetheless conclude that, if one can sense a shock-like overpressure, then the wave motion is strong enough to be observed by density-sensitive optics.

  15. Design of a magnetorheological automotive shock absorber

    NASA Astrophysics Data System (ADS)

    Lindler, Jason E.; Dimock, Glen A.; Wereley, Norman M.

    2000-06-01

    Double adjustable shock absorbers allow for independent adjustment of the yield force and post-yield damping in the force versus velocity response. To emulate the performance of a conventional double adjustable shock absorber, a magnetorheological (MR) automotive shock absorber was designed and fabricated at the University of Maryland. Located in the piston head, an applied magnetic field between the core and flux return increases the force required for a given piston rod velocity. Between the core and flux return, two different shaped gaps meet the controllable performance requirements of a double adjustable shock. A uniform gap between the core and the flux return primarily adjusts the yield force of the shock absorber, while a non-uniform gap allows for control of the post-yield damping. Force measurements from sinusoidal displacement cycles, recorded on a mechanical damper dynamometer, validate the performance of uniform and non- uniform gaps for adjustment of the yield force and post-yield damping, respectively.

  16. Global Hybrid Simulations of the Bow Shock

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Blanco-Cano, X.; Russell, C. T.

    2005-08-01

    This paper summarizes recent results from global hybrid (kinetic ions, fluid electrons) simulations of bow shocks or waves associated with solar wind interaction with magnetic dipoles of various strength. By virtue of resolving ion temporal and spatial scales, global hybrid simulations account for collissionless dissipational processes at and upstream of the shock and their effects on the macrostructure of the bow shock, ion foreshock and the magnetosheath. The results demonstrate that as the level of magnetization increases and the dipole becomes a more effective obstacle, the quasi-perpendicular part of the bow shock forms first and that formation of quasi-parallel part of the bow shock is tied to the generation of oblique magnetosonic waves which steepen to form shocklets in the upstream region.

  17. Overdriven shocks in solids and liquids

    SciTech Connect

    Wallace, D.C.

    1991-01-01

    The structure of overdriven shocks in solids and liquids is analyzed in terms of the underlying physical concepts, without resorting to formal mathematics. Two dissipative processes are required for the existence of a steady-wave shock, namely plastic flow in a solid, or viscous flow in a liquid, and heat transport in either a solid or liquid. The first requirement is the analog of Rayleigh's theorem for gases, and the second requirement extends Rayleigh's findings. For metals, the shock analysis yields approximate plastic flow data at strain rates approaching 10{sup 12}s{sup {minus}1}. The shock risetime in solid or liquid metals is predicted to decrease to around a picosecond, as the shock strength increases through the overdriven threshold. 8 refs., 3 figs.

  18. Radiative shock calculations in various media

    NASA Astrophysics Data System (ADS)

    Michaut, C.; Boireau, L.; Leygnac, S.; Cornille, M.; Stehle, C.

    2002-06-01

    We are modeling shocks with structures governed by their radiative precursor. At this point, we are assuming a geometrically-plan shock in an ionized gas, which behaves differently than in a perfect gas. The ionization structure and the excitation energy are calculated from the local temperatures and densities, using hydrogen-like model atoms. This approach can thus be applied to heavy elements like Xenon, which is used in the experiment of astrophysical radiative shocks with the laser of the LULI, at the Ecole Polytechnique (France). After studying in details the shocks in Xenon, we now calculate the atomic data for multiple chemical elements as Hydrogen, Helium, Carbon which are everywhere in astrophysical objects, and as Argon, Krypton which are monoatomic gases. We thus investigate the jump conditions in different media and we will try to propose a phenomenological description of the radiative shocks in the stellar objects and their envelopes.

  19. Shock-produced olivine glass: First observation

    USGS Publications Warehouse

    Jeanloz, R.; Ahrens, T.J.; Lally, J.S.; Nord, G.L., Jr.; Christie, J.M.; Heuer, A.H.

    1977-01-01

    Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg0.88Fe 0.12SiO4 recovered from peak pressures of about 56 ?? 109 pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation ofolivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 ?? 109 pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.

  20. The structure of cosmic ray shocks

    NASA Astrophysics Data System (ADS)

    Axford, W. I.; Leer, E.; McKenzie, J. F.

    1982-07-01

    The acceleration of cosmic rays by steady shock waves has been discussed in brief reports by Leer et al. (1976) and Axford et al. (1977). This paper presents a more extended version of this work. The energy transfer and the structure of the shock wave is discussed in detail, and it is shown that even for moderately strong shock waves most of the upstream energy flux in the background gas is transferred to the cosmic rays. This holds also when the upstream cosmic ray pressure is very small. For an intermediate Mach-number regime the overall shock structure is shown to consist of a smooth transition followed by a gas shock (cf. Drury and Voelk, 1980).

  1. Shock front broadening in polycrystalline materials

    NASA Astrophysics Data System (ADS)

    Barber, John; Kadau, Kai

    2008-03-01

    We analyze a model for the evolution of weak shock fronts (or elastic precursor waves) in polycrystalline materials. This model is based on the idea of Meyers and Carvalho [Mater. Sci. Eng. 24, 131 (1976)] that the shock velocity anisotropy within the polycrystal is the most important factor in shock front broadening. Our analysis predicts that the shock front width increases as the 1/2 power of the front penetration distance into the crystal. Our theoretical prediction is in plausible agreement with previous experimental results for the elastic precursor rise time, and it should therefore provide a useful shock width estimate. Furthermore, our theoretical framework is also applicable to other problems involving front propagation in heterogeneous media.

  2. Strong imploding shock - The representative curve

    NASA Astrophysics Data System (ADS)

    Mishkin, E. A.; Alejaldre, C.

    1981-02-01

    The representative curve of the ideal gas behind the front of a spherically or cylindrically asymmetric strong imploding shock is derived. The partial differential equations of mass, momentum and energy conservation are reduced to a set of ordinary differential equations by the method of quasi-separation of variables, following which the reduced pressure and density as functions of the radius with respect to the shock front are explicit functions of coordinates defining the phase plane of the self-similar solution. The curve in phase space representing the state of the imploded gas behind the shock front is shown to pass through the point where the reduced pressure is maximum, which is located somewhat behind the shock front and ahead of the tail of the shock.

  3. Spherical shock waves in general relativity

    SciTech Connect

    Nutku, Y. )

    1991-11-15

    We present the metric appropriate to a spherical shock wave in the framework of general relativity. This is a Petrov type-{ital N} vacuum solution of the Einstein field equations where the metric is continuous across the shock and the Riemann tensor suffers a step-function discontinuity. Spherical gravitational waves are described by type-{ital N} Robinson-Trautman metrics. However, for shock waves the Robinson-Trautman solutions are unacceptable because the metric becomes discontinuous in the Robinson-Trautman coordinate system. Other coordinate systems that have so far been introduced for describing Robinson-Trautman solutions also suffer from the same defect. We shall present the {ital C}{sup 0}-form of the metric appropriate to spherical shock waves using Penrose's approach of identification with warp. Further extensions of Penrose's method yield accelerating, as well as coupled electromagnetic-gravitational shock-wave solutions.

  4. Organic synthesis in experimental impact shocks

    NASA Technical Reports Server (NTRS)

    McKay, C. P.; Borucki, W. J.

    1997-01-01

    Laboratory simulations of shocks created with a high-energy laser demonstrate that the efficacy of organic production depends on the molecular, not just the elemental composition of the shocked gas. In a methane-rich mixture that simulates a low-temperature equilibrium mixture of cometary material, hydrogen cyanide and acetylene were produced with yields of 5 x 10(17) molecules per joule. Repeated shocking of the methane-rich mixture produced amine groups, suggesting the possible synthesis of amino acids. No organic molecules were produced in a carbon dioxide-rich mixture, which is at odds with thermodynamic equilibrium approaches to shock chemistry and has implications for the modeling of shock-produced organic molecules on early Earth.

  5. Stability of imploding spherical shock waves

    NASA Astrophysics Data System (ADS)

    Chen, H. B.; Zhang, L.; Panarella, E.

    1995-12-01

    The stability of spherically imploding shock waves is systematically investigated in this letter. The basic state is Guderley and Landau's unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandrasekhar's approach to the stability of a viscous liquid drop with Zel'dovich's approach to the stability of spherical flames. The time-dependent amplitudes of the perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. It is found that the growth rate of perturbations is not in exponential form and near the collapse phase of the shocks, the spherically imploding shock waves are relatively stable.

  6. Stability of imploding spherical shock waves

    SciTech Connect

    Chen, H.B.; Zhang, L.; Panarella, E.

    1995-12-01

    The stability of spherically imploding shock waves is systematically investigated in this letter. The basic state is Guderley and Landau`s unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandrasekhar`s approach to the stability of a viscous liquid drop with Zel`dovich`s approach to the stability of spherical flames. The time-dependent amplitudes of the perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. It is found that the growth rate of perturbations is not in exponential form and near the collapse phase of the shocks, the spherically imploding shock waves are relatively stable. 14 refs., 1 fig.

  7. Shock-produced olivine glass - First observation

    NASA Technical Reports Server (NTRS)

    Jeanloz, R.; Ahrens, T. J.; Lally, J. S.; Nord, G. L., Jr.; Christie, J. M.; Heuer, A. H.

    1977-01-01

    Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, /Mg(0.88)Fe(0.12)/2SiO4, recovered from peak pressures of about 56 billion pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation of olivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 billion pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.

  8. Physics of Bacteria During Osmotic Shock

    NASA Astrophysics Data System (ADS)

    Price, Jordan; Klug, William

    Bacteria combat hypoosmotic shocks by opening mechanosensitive ion channels located within the inner membrane. These channels are believed to act as ``emergency release valves,'' reducing transient pressure during the shock by regulating solute and water flux. Recent experiments have shown that cell survivability depends strongly on channel populations and the rate of osmotic shock. However, the understanding of the physical mechanisms behind osmotic protection remains unclear. We investigate how channel deletions, variations in shock rate, and cell envelope mechanics affect survivability by constructing theoretical elasticity and transport models. We find that reducing the number of channels and applying faster shocks significantly increases the time-dependent stress of the cell membrane and wall. This result provides insight into physical mechanisms that govern cell failure, including membrane rupture and wall fracture.

  9. Converging shocks for DSD modelling

    NASA Astrophysics Data System (ADS)

    Matignon, Christophe

    2013-06-01

    Modelling of pyrotechnic systems requires both, a good understanding and precise prediction capabilities of the dynamics of detonation. When using insensitive high explosives IHE (such as TATB-based explosives) the interaction of the detonation front with the confinement can lead to very different detonation velocities. One of the most popular engineering tools used to model this behaviour is the Detonation Shock Dynamics (DSD). In the DSD assumption, the detonation front propagates at a normal shock velocity (Dn) which depends only on its local curvature (κ). For divergent detonations, the DSD limit is very well established both experimentally and theoretically and one can easily propose a model (which obeys the 1D quasi-steady weakly curved detonation theory) to reproduce this behavior. We propose to extend the DSD theory to slightly convergent detonation fronts and to validate it against experimental data. Two series of experiments were carried out. The first series was designed to collect precise information regarding converging detonation. Usually, in such configurations, the detonation is non steady, making precise and simultaneous measurements of velocity and curvature difficult to achieve. The originality of the proposed setup is to drive a self similar convergent detonation at constant speed in an IHE rod by an external explosive tube of greater detonation velocity (allowing an accurate recording of both velocity and curvature). A wide range EOS/reaction rate model (inspired from previous works of Wescott et al.) was then calibrated to reproduce both the strong shock initiation and the newly extended (Dn- κ) law. This model can be used to perform either direct numerical simulation (DNS) on fine resolved mesh grid, or its reduced PZR model (DSD based) on a much coarser grid. This model was then successfully validated against the second series of experiments involving a detonation propagating around an obstacle and exhibiting a non steady converging front

  10. Laser Light Scattering by Shock Waves

    NASA Technical Reports Server (NTRS)

    Panda, J.; Adamovsky, G.

    1995-01-01

    Scattering of coherent light as it propagates parallel to a shock wave, formed in front of a bluff cylindrical body placed in a supersonic stream, is studied experimentally and numerically. Two incident optical fields are considered. First, a large diameter collimated beam is allowed to pass through the shock containing flow. The light intensity distribution in the resultant shadowgraph image, measured by a low light CCD camera, shows well-defined fringes upstream and downstream of the shadow cast by the shock. In the second situation, a narrow laser beam is brought to a grazing incidence on the shock and the scattered light, which appears as a diverging sheet from the point of interaction, is visualized and measured on a screen placed normal to the laser path. Experiments are conducted on shocks formed at various free-stream Mach numbers, M, and total pressures, P(sub 0). It is found that the widths of the shock shadows in a shadowgraph image become independent of M and P(sub 0) when plotted against the jump in the refractive index, (Delta)n, created across the shock. The total scattered light measured from the narrow laser beam and shock interaction also follows the same trend. In the numerical part of the study, the shock is assumed to be a 'phase object', which introduces phase difference between the upstream and downstream propagating parts of the light disturbances. For a given shape and (Delta)n of the bow shock the phase and amplitude modulations are first calculated by ray tracing. The wave front is then propagated to the screen using the Fresnet diffraction equation. The calculated intensity distribution, for both of the incident optical fields, shows good agreement with the experimental data.

  11. Shock Propagation Modeling in Heterogeneous Materials

    NASA Astrophysics Data System (ADS)

    Haill, Thomas

    2013-06-01

    Shock compression of foams is an intriguing research area that challenges our abilities to model experiments using computer simulations that span 9 orders of magnitude in spatial scales from the atomistic scale through the mesoscale and up to the continuum levels. Experiments test shock compression of dense polymers, polymer foams, and high-Z doped foams. Random distributions of polymer fibers, variations in pore size, and non-uniformities in the bulk properties of the foam (such as mean density) lead to spread in the experimental data. Adding dopants to foams introduces new complexities and the effect of the distribution and sizes of dopant particles must be characterized and understood. Therefore we turn to computer simulation to illumine the intricacies of the experiments that cannot be directly measured. This paper overviews of our range of methods to model pure and platinum-doped poly-methyl-pentene (PMP) foams. At the nanometer scale, hydrodynamic simulations compare favorably to classical molecular dynamics (MD) simulations of porous foams, verifying models of foam vaporization under strong shock conditions. Inhomogeneous mesoscale and homogenized continuum simulations present contrasting pictures of shocked foams. Mesoscale simulations at the micron scale have diffuse shock widths that depend upon the pore size, and post-shock vorticity results in fluctuations about the mean post-shock state and lower mean pressures and temperatures. Homogenized simulations, in the limit of zero pore size, have narrow shock widths, steady post-shock states, and higher mean pressures and temperature that compare favorably with 1D analysis of experiments. We reconcile the contrasting mesoscale and continuum views using theoretical turbulent corrections to the Hugoniot jump condition to show a consistent picture of shocked foams over 9 orders of spatial scale. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned

  12. Combining Observations of Shock-induced Minerals with Calculations to Constrain the Shock History of Meteorites.

    NASA Astrophysics Data System (ADS)

    de Carli, P. S.; Xie, Z.; Sharp, T. G.

    2007-12-01

    All available evidence from shock Hugoniot and release adiabat measurements and from shock recovery experiments supports the hypothesis that the conditions for shock-induced phase transitions are similar to the conditions under which quasistatic phase transitions are observed. Transitions that require high temperatures under quasistatic pressures require high temperatures under shock pressures. The high-pressure phases found in shocked meteorites are almost invariably associated with shock melt veins. A shock melt vein is analogous to a pseudotachylite, a sheet of locally melted material that was quenched by conduction to surrounding cooler material. The mechanism by which shock melt veins form is not known; possible mechanisms include shock collisions, shock interactions with cracks and pores, and adiabatic shear. If one assumes that the phases within the vein crystallized in their stability fields, then available static high-pressure data constrain the shock pressure range over which the vein solidified. Since the veins have a sheet-like geometry, one may use one-dimensional heat flow calculations to constrain the cooling and crystallization history of the veins (Langenhorst and Poirier, 2000). Although the formation mechanism of a melt vein may involve transient pressure excursions, pressure equilibration of a mm-wide vein will be complete within about a microsecond, whereas thermal equilibration will require seconds. Some of our melt vein studies have indicated that the highly-shocked L chondrite meteorites were exposed to a narrow range of shock pressures, e.g., 18-25 GPa, over a minimum duration of the order of a second. We have used the Autodyn(TM) wave propagation code to calculate details of plausible impacts on the L-chondrite parent body for a variety of possible parent body stratigraphies. We infer that some meteorites probably represent material that was shocked at a depth of >10 km in their parent bodies.

  13. Molecular shock response of explosives: electronic absorption spectroscopy

    SciTech Connect

    Mcgrne, Shawn D; Moore, David S; Whitley, Von H; Bolme, Cindy A; Eakins, Daniel E

    2009-01-01

    Electronic absorption spectroscopy in the range 400-800 nm was coupled to ultrafast laser generated shocks to begin addressing the question of the extent to which electronic excitations are involved in shock induced reactions. Data are presented on shocked polymethylmethacrylate (PMMA) thin films and single crystal pentaerythritol tetranitrate (PETN). Shocked PMMA exhibited thin film interference effects from the shock front. Shocked PETN exhibited interference from the shock front as well as broadband increased absorption. Relation to shock initiation hypotheses and the need for time dependent absorption data (future experiments) is briefly discussed.

  14. Shock Hugoniot measurements in foam

    NASA Astrophysics Data System (ADS)

    Petel, O. E.; Ouellet, S.; Frost, D. L.; Higgins, A. J.

    2014-05-01

    The present study outlines a new approach to collecting shock Hugoniot data in foams using photonic Doppler velocimetry to perform mid-plane measurements of the foam deformation. Plate impact experiments were carried out to investigate wave propagation in a closed-cell polymeric foam and an open-cell aluminum foam. Dual-wave structures were observed in both materials with the leading precursor wave determined to be an elastic wave. The discussion of the results focuses on the nature of foam compression under high-rate loading, particularly the difference between the strain history in a foam undergoing uniform stress compaction and uniaxial strain compression. These results are discussed in reference to the current interpretations of Taylor-Hopkinson bar experiments on similar metallic foams. The importance of gas-filtration driven flows in the wave dynamics of open-cell foams is discussed in relation to the nature of the precursor waves.

  15. VIBRATION DAMPING AND SHOCK MOUNT

    DOEpatents

    Stevens, D.J.; Forman, G.W.

    1963-12-10

    A shock absorbing mount in which vibrations are damped by an interference fit between relatively movable parts of the mount is described. A pair of generally cup-shaped parts or members have skirt portions disposed in an oppositely facing nesting relationship with the skirt of one member frictionally engaging the skirt of the other. The outermost skirt may be slotted to provide spring-like segments which embrace the inner skirt for effecting the interference fit. Belleville washers between the members provide yieldable support for a load carried by the mount. When a resonant frequency of vibration forces acting upon the moumt attains a certain level the kinetic energy of these forces is absorbed by sliding friction between the parts. (AEC)

  16. Severe sepsis and septic shock

    PubMed Central

    Schorr, Christa A; Zanotti, Sergio; Dellinger, R Phillip

    2014-01-01

    Morbidity and mortality from sepsis remains unacceptably high. Large variability in clinical practice, plus the increasing awareness that certain processes of care associated with improved critical care outcomes, has led to the development of clinical practice guidelines in a variety of areas related to infection and sepsis. The Surviving Sepsis Guidelines for Management of Severe Sepsis and Septic Shock were first published in 2004, revised in 2008, and recently revised again and published in 2013. The first part of this manuscript is a summary of the 2013 guidelines with some editorial comment. The second part of the manuscript characterizes hospital based sepsis performance improvement programs and highlights the sepsis bundles from the Surviving Sepsis Campaign as a key component of such a program. PMID:24335487

  17. Thermal shock resistance ceramic insulator

    DOEpatents

    Morgan, Chester S.; Johnson, William R.

    1980-01-01

    Thermal shock resistant cermet insulators containing 0.1-20 volume % metal present as a dispersed phase. The insulators are prepared by a process comprising the steps of (a) providing a first solid phase mixture of a ceramic powder and a metal precursor; (b) heating the first solid phase mixture above the minimum decomposition temperature of the metal precursor for no longer than 30 minutes and to a temperature sufficiently above the decomposition temperature to cause the selective decomposition of the metal precursor to the metal to provide a second solid phase mixture comprising particles of ceramic having discrete metal particles adhering to their surfaces, said metal particles having a mean diameter no more than 1/2 the mean diameter of the ceramic particles, and (c) densifying the second solid phase mixture to provide a cermet insulator having 0.1-20 volume % metal present as a dispersed phase.

  18. Toxic shock syndrome in Canada.

    PubMed Central

    Clayton, A. J.; Peacocke, J. E.; Ewan, P. E.

    1982-01-01

    Since 1976, 53 confirmed or suspected cases of toxic shock syndrome (TSS) have been reported in Canada. Twenty-two cases occurred in 1980, and by October 1981 another 21 had been reported. In Canada, like the United States, where nearly 1200 cases have been recorded, TSS appears to be associated with tampon use, although a few cases have occurred in males and in nonmenstruating women. Of the 53 patients 3 died. The enterotoxin produced by Staphylococcus aureus is probably responsible for TSS. Manufacturers of tampons have now placed warning labels on tampon boxes and information on TSS in the instruction inserts. Women should select tampons of appropriate absorbency for the various stages of menstruation. PMID:7042059

  19. Current topics in shock waves; Proceedings of the International Symposium on Shock Waves and Shock Tubes, 17th, Lehigh University, Bethlehem, PA, July 17-21, 1989

    SciTech Connect

    Kim, Y.W.

    1990-01-01

    Various papers on shock waves are presented. The general topics addressed include: shock formation, focusing, and implosion; shock reflection and diffraction; turbulence; laser-produced plasmas and waves; ionization and shock-plasma interaction; chemical kinetics, pyrolysis, and soot formation; experimental facilities, techniques, and applications; ignition of detonation and combustion; particle entrainment and shock propagation through particle suspension; boundary layers and blast simulation; computational methods and numerical simulation.

  20. Clinical review: mechanical circulatory support for cardiogenic shock complicating acute myocardial infarction

    PubMed Central

    2010-01-01

    Acute myocardial infarction is one of the 10 leading reasons for admission to adult critical care units. In-hospital mortality for this condition has remained static in recent years, and this is related primarily to the development of cardiogenic shock. Recent advances in reperfusion therapies have had little impact on the mortality of cardiogenic shock. This may be attributable to the underutilization of life support technology that may assist or completely supplant the patient's own cardiac output until adequate myocardial recovery is established or long-term therapy can be initiated. Clinicians working in the intensive care environment are increasingly likely to be exposed to these technologies. The purpose of this review is to outline the various techniques of mechanical circulatory support and discuss the latest evidence for their use in cardiogenic shock complicating acute myocardial infarction. PMID:21067535

  1. A shock wave capability for the improved Two-Dimensional Kinetics (TDK) computer program

    NASA Astrophysics Data System (ADS)

    Nickerson, G. R.; Dang, L. D.

    1984-03-01

    The Two Dimensional Kinetics (TDK) computer program is a primary tool in applying the JANNAF liquid rocket engine performance prediction procedures. The purpose of this contract has been to improve the TDK computer program so that it can be applied to rocket engine designs of advanced type. In particular, future orbit transfer vehicles (OTV) will require rocket engines that operate at high expansion ratio, i.e., in excess of 200:1. Because only a limited length is available in the space shuttle bay, it is possible that OTV nozzles will be designed with both relatively short length and high expansion ratio. In this case, a shock wave may be present in the flow. The TDK computer program was modified to include the simulation of shock waves in the supersonic nozzle flow field. The shocks induced by the wall contour can produce strong perturbations of the flow, affecting downstream conditions which need to be considered for thrust chamber performance calculations.

  2. On the high correlation between storm sudden commencements and interplanetary shocks

    NASA Astrophysics Data System (ADS)

    Park, W.; Lee, J.; Oh, S.; Yi, Y.

    2014-12-01

    Storm Sudden Commencements (SSCs) occur due to sudden compression of magnetic field and current enhancement in the magnetopause, which is generally believed to be caused by interplanetary shock. However, neither all geomagnetic storms exhibit the SSC nor all SSCs are accompanied by interplanetary shocks. In this study, we search for geomagnetic storms without SSC using the SYM-H index data which is provided by the World Data Center for Geomagnetism Kyoto (WDC Geomag, Kyoto) during the period of 1998-2010. We also investigate the physical conditions such as density and velocity of protons, IMF Bz and total field strength provided by Advanced Composition Explorer (ACE) satellite. Finally, we classify the geomagnetic storms into two groups depending on whether or not accompanied by SSC and then further classify them based on their association with interplanetary shocks. Physical characteristics of the storms in each group will briefly be discussed.

  3. A shock wave capability for the improved Two-Dimensional Kinetics (TDK) computer program

    NASA Technical Reports Server (NTRS)

    Nickerson, G. R.; Dang, L. D.

    1984-01-01

    The Two Dimensional Kinetics (TDK) computer program is a primary tool in applying the JANNAF liquid rocket engine performance prediction procedures. The purpose of this contract has been to improve the TDK computer program so that it can be applied to rocket engine designs of advanced type. In particular, future orbit transfer vehicles (OTV) will require rocket engines that operate at high expansion ratio, i.e., in excess of 200:1. Because only a limited length is available in the space shuttle bay, it is possible that OTV nozzles will be designed with both relatively short length and high expansion ratio. In this case, a shock wave may be present in the flow. The TDK computer program was modified to include the simulation of shock waves in the supersonic nozzle flow field. The shocks induced by the wall contour can produce strong perturbations of the flow, affecting downstream conditions which need to be considered for thrust chamber performance calculations.

  4. Advance directives

    PubMed Central

    O’Sullivan, Rory; Mailo, Kevin; Angeles, Ricardo; Agarwal, Gina

    2015-01-01

    Abstract Objective To establish the prevalence of patients with advance directives in a family practice, and to describe patients’ perspectives on a family doctor’s role in initiating discussions about advance directives. Design A self-administered patient questionnaire. Setting A busy urban family medicine teaching clinic in Hamilton, Ont. Participants A convenience sample of adult patients attending the clinic over the course of a typical business week. Main outcome measures The prevalence of advance directives in the patient population was determined, and the patients’ expectations regarding the role of their family doctors were elucidated. Results The survey population consisted of 800 participants (a response rate of 72.5%) well distributed across age groups; 19.7% had written advance directives and 43.8% had previously discussed the topic of advance directives, but only 4.3% of these discussions had occurred with family doctors. In 5.7% of cases, a family physician had raised the issue; 72.3% of respondents believed patients should initiate the discussion. Patients who considered advance directives extremely important were significantly more likely to want their family doctors to start the conversation (odds ratio 3.98; P < .05). Conclusion Advance directives were not routinely addressed in the family practice. Most patients preferred to initiate the discussion of advance directives. However, patients who considered the subject extremely important wanted their family doctors to initiate the discussion. PMID:25873704

  5. Interplanetary shock-bow shock interaction: Comparison of a global MHD model and observation

    NASA Astrophysics Data System (ADS)

    Goncharov, O.; Šafránková, J.; Němeček, Z.

    2015-09-01

    A fast forward shock passing through the bow shock would generate a train of new discontinuities that differ with the distance from the Sun-Earth line. However, interplanetary (IP) shocks are often followed by a rotation of the interplanetary magnetic field (IMF) over a large angle and a presence of this rotation can modify the interaction process. The present paper analyzes in detail one IP shock where data measured by Wind are used as an input to a global BATS-R-US MHD model and the model prediction is compared with Geotail magnetosheath observations. The study is based on three runs of the global MHD model that use different modifications of upstream conditions. We have found that (1) about 45% of IP shocks is followed by a significant IMF rotation within 15 min after the shock ramp; (2) the IMF rotation modifies the dynamics of the magnetospheric response to the IP shock arrival; (3) a train of new discontinuities created by an interaction of the IP shock with bow shock can be identified in MHD simulations as well as in the experimental data; and (4) a new discontinuity is created by the interaction of the IMF rotation with the bow shock.

  6. Analysis of shock-wave propagation in aqueous foams using shock tube experiments

    NASA Astrophysics Data System (ADS)

    Jourdan, G.; Mariani, C.; Houas, L.; Chinnayya, A.; Hadjadj, A.; Del Prete, E.; Haas, J.-F.; Rambert, N.; Counilh, D.; Faure, S.

    2015-05-01

    This paper reports experimental results of planar shock waves interacting with aqueous foams in a horizontal conventional shock tube. Four incident shock wave Mach numbers are considered, ranging from 1.07 to 1.8, with two different foam columns of one meter thickness and expansion ratios of 30 and 80. High-speed flow visualizations are used along with pressure measurements to analyse the main physical mechanisms that govern shock wave mitigation in foams. During the shock/foam interaction, a precursor leading pressure jump was identified as the trace of the liquid film destruction stage in the foam fragmentation process. The corresponding pressure threshold is found to be invariant for a given foam. Regarding the mitigation effect, the results show that the speed of the shock is drastically reduced and that wetter is the foam, slower are the transmitted waves. The presence of the foam barrier attenuates the induced pressure impulse behind the transmitted shock, while the driest foam appears to be more effective, as it limits the pressure induced by the reflected shock off the foam front. Finally, it was found that the pressure histories in the two-phase gas-liquid mixture are different from those previously obtained within a cloud of droplets. The observed behavior is attributed to the process of foam fragmentation and to the modification of the flow topology past the shock. These physical phenomena occurring during the shock/foam interaction should be properly accounted for when elaborating new physical models.

  7. Shock finding on a moving mesh - I. Shock statistics in non-radiative cosmological simulations

    NASA Astrophysics Data System (ADS)

    Schaal, Kevin; Springel, Volker

    2015-02-01

    Cosmological shock waves play an important role in hierarchical structure formation by dissipating and thermalizing kinetic energy of gas flows, thereby heating the Universe. Furthermore, identifying shocks in hydrodynamical simulations and measuring their Mach number accurately are critical for calculating the production of non-thermal particle components through diffusive shock acceleration. However, shocks are often significantly broadened in numerical simulations, making it challenging to implement an accurate shock finder. We here introduce a refined methodology for detecting shocks in the moving-mesh code AREPO, and show that results for shock statistics can be sensitive to implementation details. We put special emphasis on filtering against spurious shock detections due to tangential discontinuities and contacts. Both of them are omnipresent in cosmological simulations, for example in the form of shear-induced Kelvin-Helmholtz instabilities and cold fronts. As an initial application of our new implementation, we analyse shock statistics in non-radiative cosmological simulations of dark matter and baryons. We find that the bulk of energy dissipation at redshift zero occurs in shocks with Mach numbers around M≈ 2.7. Furthermore, almost 40 per cent of the thermalization is contributed by shocks in the warm hot intergalactic medium, whereas ≈60 per cent occurs in clusters, groups, and smaller haloes. Compared to previous studies, these findings revise the characterization of the most important shocks towards higher Mach numbers and lower density structures. Our results also suggest that regions with densities above and below δb = 100 should be roughly equally important for the energetics of cosmic ray acceleration through large-scale structure shocks.

  8. Global Aeroheating Measurements of Shock-Shock Interactions on a Swept Cylinder

    NASA Technical Reports Server (NTRS)

    Mason, Michelle L.; Berry, Scott A.

    2015-01-01

    The effects of fin leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. The cylindrical leading-edge fin models, with radii varied from 0.25 to 0.75 inches, represent wings or struts on hypersonic vehicles. A 9deg wedge generated a planar oblique shock at 16.7deg. to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin sweep angle was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. These cases were chosen to explore three characterized shock-shock interaction types. Global temperature data were obtained from the surface of the fused silica fins using phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and any temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using a one-dimensional semi-infinite method, as well as one- and two-dimensional finite-volume methods. These results were compared to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for each explored shock-shock interaction type regardless of the leading-edge radius. However, the dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method.

  9. An asymmetric solar wind termination shock.

    PubMed

    Stone, Edward C; Cummings, Alan C; McDonald, Frank B; Heikkila, Bryant C; Lal, Nand; Webber, William R

    2008-07-01

    Voyager 2 crossed the solar wind termination shock at 83.7 au in the southern hemisphere, approximately 10 au closer to the Sun than found by Voyager 1 in the north. This asymmetry could indicate an asymmetric pressure from an interstellar magnetic field, from transient-induced shock motion, or from the solar wind dynamic pressure. Here we report that the intensity of 4-5 MeV protons accelerated by the shock near Voyager 2 was three times that observed concurrently by Voyager 1, indicating differences in the shock at the two locations. (Companion papers report on the plasma, magnetic field, plasma-wave and lower energy particle observations at the shock.) Voyager 2 did not find the source of anomalous cosmic rays at the shock, suggesting that the source is elsewhere on the shock or in the heliosheath. The small intensity gradient of Galactic cosmic ray helium indicates that either the gradient is further out in the heliosheath or the local interstellar Galactic cosmic ray intensity is lower than expected. PMID:18596802

  10. Dispersion discontinuities of strong collisionless shocks

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.

    1970-01-01

    Linear fluid equations are used to estimate wave train properties of strong collisionless shocks. Fast shocks exhibit several dispersion changes with increasing Mach number. For perpendicular propagation into a finite-beta plasma, an ion cyclotron radius trailing wave train exists only for (M sub F)2 is smaller than 2. Oblique fast shocks have a leading ion inertia wave train if M sub A is smaller than root of M(+)/M(-) cos theta/2 and a trailing electron inertia train if M sub A is greater than root of M(+)/M(-) cos theta/2. If the downstream sound speed exceeds the flow speed, linear wave theory predicts a trailing ion acoustic structure which probably resides within the magnetic shock. For a turbulent shock model in which an effective electron-ion collision frequency exceeds the lower hybrid frequency, ions decouple from the magnetic field; the shock wave train now trails with electron inertia and electron gyroradius lengths. Comparisons of this turbulent model and observations on the earth's bow shock are made.

  11. JPL pyro shock test approaches and results

    NASA Technical Reports Server (NTRS)

    Chang, Kurng Y.

    1986-01-01

    This paper presents the overall approach at JPL in performing spacecraft pyrotechnic shock qualification testing. Initially, the assembly shock requirements are developed early in the program based on previous spacecraft test experience and data. Pyrotechnic device development testing firings and spacecraft Development Test Model (DTM) pyro firings are then conducted to verify the adequacy of the assembly shock requirements and to determine the subsystem test firing and the subsequent system level test firing requirements. The electro-dynamic shaker, through shock synthesis techniques, is utilized to qualify the shock sensitive flight equipment with margins applied. Actual pyrotechnic device firings on spacecraft equipment or science instruments are performed when the influence of the pyros is localized and can be ignored at the system level. Full spacecraft system level shock tests, which include multiple firings of certain critical pyro devices, are conducted to verify the spacecraft design structural integrity and functions as well as to qualify hardware items which have not been previously qualified. These tests also provide a source of data from which assembly level requirements can be evaluated and compared. For example, during the Galileo program, the results demonstrated that good agreement between predicted and measured shock environments and adequate qualification of the flight spacecraft was achieved.

  12. Impaired Fracture Healing after Hemorrhagic Shock

    PubMed Central

    Kobbe, Philipp; Pfeifer, Roman; Campbell, Graeme C.; Tohidnezhad, Mersedeh; Bergmann, Christian; Kadyrov, Mamed; Fischer, Horst; Glüer, Christian C.; Pape, Hans-Christoph; Pufe, Thomas

    2015-01-01

    Impaired fracture healing can occur in severely injured patients with hemorrhagic shock due to decreased soft tissue perfusion after trauma. We investigated the effects of fracture healing in a standardized pressure controlled hemorrhagic shock model in mice, to test the hypothesis that bleeding is relevant in the bone healing response. Male C57/BL6 mice were subjected to a closed femoral shaft fracture stabilized by intramedullary nailing. One group was additionally subjected to pressure controlled hemorrhagic shock (HS, mean arterial pressure (MAP) of 35 mmHg for 90 minutes). Serum cytokines (IL-6, KC, MCP-1, and TNF-α) were analyzed 6 hours after shock. Fracture healing was assessed 21 days after fracture. Hemorrhagic shock is associated with a significant increase in serum inflammatory cytokines in the early phase. Histologic analysis demonstrated a significantly decreased number of osteoclasts, a decrease in bone quality, and more cartilage islands after hemorrhagic shock. μCT analysis showed a trend towards decreased bone tissue mineral density in the HS group. Mechanical testing revealed no difference in tensile failure. Our results suggest a delay in fracture healing after hemorrhagic shock. This may be due to significantly diminished osteoclast recruitment. The exact mechanisms should be studied further, particularly during earlier stages of fracture healing. PMID:26106256

  13. Overview of shock waves in medicine

    NASA Astrophysics Data System (ADS)

    Cleveland, Robin O.

    2003-10-01

    A brief overview of three applications of shock waves is presented. Shock wave lithotripsy (SWL) has been in clinical use for more than 20 years. In the United States it is used to treat more than 80% of kidney stone cases and has wide acceptance with patients because it is a noninvasive procedure. Despite SWLs enormous success there is no agreement on how shock waves comminute stones. There is also a general acceptance that shock waves lead to trauma to the soft tissue of the kidney. Yet there has been little forward progress in developing lithotripters which provide comminution with less side-effects, indeed the original machine is still considered the gold standard. The last decade has seen the advent of new shock wave devices for treating principally musculoskeletal indications, such as plantar fasciitis, tennis elbow, and bone fractures that do not heal. This is referred to as shock wave therapy (SWT). The mechanisms by which SWT works are even less well understood than SWL and the consequences of bioeffects have also not been studied in detail. Shock waves have also been shown to be effective at enhancing drug delivery into cells and assisting with gene transfection. [Work partially supported by NIH.

  14. Heat shock proteins of higher plants

    PubMed Central

    Key, Joe L.; Lin, C. Y.; Chen, Y. M.

    1981-01-01

    The pattern of protein synthesis changes rapidly and dramatically when the growth temperature of soybean seedling tissue is increased from 28°C (normal) to about 40°C (heat shock). The synthesis of normal proteins is greatly decreased and a new set of proteins, “heat shock proteins,” is induced. The heat shock proteins of soybean consist of 10 new bands on one-dimensional NaDodSO4 gels; a more complex pattern is observed on two-dimensional gels. When the tissue is returned to 28°C after 4 hr at 40°C, there is progressive decline in the synthesis of heat shock proteins and reappearance of a normal pattern of synthesis by 3 or 4 hr. In vitro translation of poly(A)+RNAs isolated from tissues grown at 28 and 40°C shows that the heat shock proteins are translated from a new set of mRNAs induced at 40°C; furthermore, the abundant class mRNAs for many of the normal proteins persist even though they are translated weakly (or not at all) in vivo at 40 or 42.5°C. The heat shock response in soybean appears similar to the much-studied heat shock phenomenon in Drosophila. Images PMID:16593032

  15. Beamwidth measurement of individual lithotripter shock waves

    PubMed Central

    Kreider, Wayne; Bailey, Michael R.; Ketterling, Jeffrey A.

    2009-01-01

    New lithotripters with narrower foci and higher peak pressures than the original Dornier HM3 electrohydraulic lithotripter have proven to be less effective and less safe. Hence, accurate measurements of the focal characteristics of lithotripter shock waves are important. The current technique for measuring beamwidth requires a collection of single-point measurements over multiple shock waves, thereby introducing error as a result of any shock-to-shock variability. This work reports on the construction of a hydrophone array sensor and on array measurements of individual lithotripter shock waves. Beamwidths for an electrohydraulic lithotripter with a broad-focus HM3-style reflector and a narrow-focus modified reflector were measured using both new and worn electrodes as well as two different electrical charging potentials. The array measured the waveform, beamwidth, and focal location of individual shock waves. The HM3-style reflector produced repeatable focal waveforms and beam profiles at an 18 kV charging potential with new and worn electrodes. Corresponding measurements suggest a narrower beamwidth than reported previously from averaged point measurements acquired under the same conditions. In addition, a lack of consistency in the measured beam profiles at 23 kV underscores the value of measuring individual shock waves. PMID:19206897

  16. DIFFUSIVE SHOCK ACCELERATION SIMULATIONS OF RADIO RELICS

    SciTech Connect

    Kang, Hyesung; Ryu, Dongsu; Jones, T. W. E-mail: ryu@canopus.cnu.ac.kr

    2012-09-01

    Recent radio observations have identified a class of structures, so-called radio relics, in clusters of galaxies. The radio emission from these sources is interpreted as synchrotron radiation from GeV electrons gyrating in {mu}G-level magnetic fields. Radio relics, located mostly in the outskirts of clusters, seem to associate with shock waves, especially those developed during mergers. In fact, they seem to be good structures to identify and probe such shocks in intracluster media (ICMs), provided we understand the electron acceleration and re-acceleration at those shocks. In this paper, we describe time-dependent simulations for diffusive shock acceleration at weak shocks that are expected to be found in ICMs. Freshly injected as well as pre-existing populations of cosmic-ray (CR) electrons are considered, and energy losses via synchrotron and inverse Compton are included. We then compare the synchrotron flux and spectral distributions estimated from the simulations with those in two well-observed radio relics in CIZA J2242.8+5301 and ZwCl0008.8+5215. Considering that CR electron injection is expected to be rather inefficient at weak shocks with Mach number M {approx}< a few, the existence of radio relics could indicate the pre-existing population of low-energy CR electrons in ICMs. The implication of our results on the merger shock scenario of radio relics is discussed.

  17. Modeling nonthermal emission from stellar bow shocks

    NASA Astrophysics Data System (ADS)

    Pereira, V.; López-Santiago, J.; Miceli, M.; Bonito, R.; de Castro, E.

    2016-04-01

    Context. Runaway O- and early B-type stars passing through the interstellar medium at supersonic velocities and characterized by strong stellar winds may produce bow shocks that can serve as particle acceleration sites. Previous theoretical models predict the production of high-energy photons by nonthermal radiative processes, but their efficiency is still debated. Aims: We aim to test and explain the possibility of emission from the bow shocks formed by runaway stars traveling through the interstellar medium by using previous theoretical models. Methods: We applied our model to AE Aurigae, the first reported star with an X-ray detected bow shock, to BD+43 3654, in which the observations failed in detecting high-energy emission, and to the transition phase of a supergiant star in the late stages of its life. Results: From our analysis, we confirm that the X-ray emission from the bow shock produced by AE Aurigae can be explained by inverse Compton processes involving the infrared photons of the heated dust. We also predict low high-energy flux emission from the bow shock produced by BD+43 3654, and the possibility of high-energy emission from the bow shock formed by a supergiant star during the transition phase from blue to red supergiant. Conclusions: Bow shocks formed by different types of runaway stars are revealed as a new possible source of high-energy photons in our neighborhood.

  18. Modeling and Laboratory Investigations of Radiative Shocks

    NASA Astrophysics Data System (ADS)

    Grun, Jacob; Laming, J. Martin; Manka, Charles; Moore, Christopher; Jones, Ted; Tam, Daniel

    2001-10-01

    Supernova remnants are often inhomogeneous, with knots or clumps of material expanding in ambient plasma. This structure may be initiated by hydrodynamic instabilities occurring during the explosion, but it may plausibly be amplified by instabilities of the expanding shocks such as, for example, corrugation instabilities described by D’yakov in 1954, Vishniac in 1983, and observed in the laboratory by Grun et al. in 1991. Shock instability can occur when radiation lowers the effective adiabatic index of the gas. In view of the difficulty of modeling radiation in non-equilibrium plasmas, and the dependence of shock instabilities on such radiation, we are performing a laboratory experiment to study radiative shocks. The shocks are generated in a miniature, laser-driven shock tube. The gas density inside the tube at any instant in time is measured using time and space-resolved interferometry, and the emission spectrum of the gas is measured with time-resolved spectroscopy. We simulate the experiment with a 1D code that models time dependent post-shock ionization and non-equilibrium radiative cooling. S. P. D’yakov, Zhurnal Eksperimentalnoi Teoreticheskoi Fiziki 27, 288 (1954); see also section 90 in L.D. Landau and E.M. Lifshitz, Fluid Mechanics (Butterworth-Heinemann 1987); E.T. Vishniac, Astrophys. J. 236, 880 (1983); J. Grun, et al., Phys. Rev. Lett., 66, 2738 (1991)

  19. Radiation from Shock-Accelerated Particles

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-ichi; Choi, E. J.; Min, K. W.; Niemiec, J.; Zhang, B.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2012-01-01

    Plasma instabilities excited in collisionless shocks are responsible for particle acceleration, generation of magnetic fields , and associated radiation. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. The shock structure depends on the composition of the jet and ambient plasma (electron-positron or electron-ions). Strong electromagnetic fields are generated in the reverse , jet shock and provide an emission site. These magnetic fields contribute to the electron's transverse deflection behind the shock. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. The detailed properties of the radiation are important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jet shocks, and supernova remnants

  20. Fever, hyperthermia and the heat shock response.

    PubMed

    Singh, Ishwar S; Hasday, Jeffrey D

    2013-08-01

    The heat shock response is a highly conserved primitive response that is essential for survival against a wide range of stresses, including extremes of temperature. Fever is a more recently evolved response, during which organisms raise their core body temperature and temporarily subject themselves to thermal stress in the face of infections. The present review documents studies showing the potential overlap between the febrile response and the heat shock response and how both activate the same common transcriptional programme (although with different magnitudes) including the stress-activated transcription factor, heat shock factor-1, to modify host defences in the context of infection, inflammation and injury. The review focuses primarily on how hyperthermia within the febrile range that often accompanies infections and inflammation acts as a biological response modifier and modifies innate immune responses. The characteristic 2-3 °C increase in core body temperature during fever activates and utilises elements of the heat shock response pathway to modify cytokine and chemokine gene expression, cellular signalling and immune cell mobilisation to sites of inflammation, infection and injury. Interestingly, typical proinflammatory agonists such as Toll-like receptor agonists modify the heat shock-induced transcriptional programme and expression of HSP genes following co-exposure to febrile range hyperthermia or heat shock, suggesting a complex reciprocal regulation between the inflammatory pathway and the heat shock response pathway. PMID:23863046

  1. Shock compression dynamics under a microscope.

    NASA Astrophysics Data System (ADS)

    Dlott, Dana

    2015-06-01

    We have developed a tabletop laser flyer launch system1 that solves many of the problems that plagued previous efforts. Using a novel mechanism where a spatially-uniform laser pulse creates a shock in a glass substrate just underneath a metal foil, we can launch tiny (0.7 mm diameter x 100 μm thick) flyers at speeds ranging from 0-5 km/s and the foils are flat, cold and intact. This tabletop launch system, where we often launch 100 flyers per day, provides a platform for a wide variety of time-resolved spectroscopies. The shocked material is viewed by a microscope objective that transmits near-infrared light from a photon Doppler velocimeter to monitor the flyer, and collects the light for spectroscopic and video images. Fluorescent probes, which have been highly developed for the biomedical sciences, have proven especially useful for these experiments. Using emission measurements, we have investigated the fundamental mechanisms of many shock wave effects including: viscoelastic compression of high molecular weight polymers, visualization of shocks in porous media such as sand, where we can observe the behavior of individual grains of sand, shock attenuation by passing the shock through reactive materials that undergo endothermic chemical reactions, and shock initiation of nanoenergetic materials.

  2. DSMC Computations for Regions of Shock/Shock and Shock/Boundary Layer Interaction

    NASA Technical Reports Server (NTRS)

    Moss, James N.

    2001-01-01

    This paper presents the results of a numerical study of hypersonic interacting flows at flow conditions that include those for which experiments have been conducted in the Calspan-University of Buffalo Research Center (CUBRC) Large Energy National Shock (LENS) tunnel and the ONERA R5Ch low-density wind tunnel. The computations are made with the direct simulation Monte Carlo (DSMC) method of Bird. The focus is on Mach 9.3 to 11.4 flows about flared axisymmetric configurations, both hollow cylinder flares and double cones. The results presented highlight the sensitivity of the calculations to grid resolution, provide results concerning the conditions for incipient separation, and provide information concerning the flow structure and surface results for the extent of separation, heating, pressure, and skin friction.

  3. Suprathermal Electrons at Saturn's Bow Shock

    NASA Astrophysics Data System (ADS)

    Masters, A.; Sulaiman, A. H.; Sergis, N.; Stawarz, L.; Fujimoto, M.; Coates, A. J.; Dougherty, M. K.

    2016-07-01

    The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini. The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, <28 keV) during shock crossings, but the higher energy channels were at (or close to) background. The high-energy electron detector (MIMI-LEMMS, >18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically only the lowest energy channels (<100 keV) were above background. We show that these results are consistent with the theory in which the “injection” of thermal electrons into an acceleration process involves interaction with whistler waves at the shock front, and becomes possible for all upstream magnetic field orientations at high Mach numbers like those of the strong shocks around young SNRs. A future dedicated study will analyze the rare crossings with evidence for relativistic electrons (up to ˜1 MeV).

  4. Multidimensional radiative effects in supercritical shocks

    NASA Astrophysics Data System (ADS)

    Leygnac, S.; Lanz, T.; Stehlé, C.; Michaut, C.; Korĉáková, D.

    Recent radiative shocks experiments performed on the LULI laser at Ecole Polytechnique in France (Fleury et al., Lasers and Particle Beams 20, 263, 2002) put in evidence a supercritical shock wave in a xenon gas cell. The structure of these shocks is quite similar to those of accretion shock wave in the case of stellar formation, as indicated in Stehlé and Chieze (SF2A - Paris proceedings, 2002). Some points require further studies like the contribution of the gas excitation/ionization energy to the compression ratio and the understanding of the discrepancy, which was noted between the velocity of the radiative precursor in the experiment and in the 1D simulation. Thus, to understand the physics of the radiative shock waves, the academic case of the stationary shock is particularly interesting. We have thus studied the structure of a radiative shock wave which propagates in an ionized gas. We study the extended Rankine Hugoniot equations in various media with inclusion of radiation pressure and energy and study also the extension of the radiative precursor in the diffusion approximation. We also study the equations of multidimensional radiative transfer for a snapshot of the experimental shock in xenon in order to quantify the radiative losses in the finite experimental cell. This academic approach will help to improve the knowledge of the physical processes which take place in radiative shocks of astrophysical interest, like in the birth and death of stars, and prepare ourselves to define appropriate experiments on future high power lasers like LIL and LMJ in Bordeaux.

  5. A merger shock in A2034

    SciTech Connect

    Owers, Matt S.; Couch, Warrick J.; Hopkins, Andrew M.; Nulsen, Paul E. J.; Ma, Cheng-Jiun; David, Laurence P.; Forman, William R.; Jones, Christine; Van Weeren, Reinout J.

    2014-01-10

    We present a 250 ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front. The new data reveal that the edge is coherent over a larger opening angle and is significantly more bow-shock-shaped than previously thought. Within ∼27° about the axis of symmetry of the edge, the density, temperature, and pressure drop abruptly by factors of 1.83{sub −0.08}{sup +0.09}, 1.85{sub −0.41}{sup +0.41}, and 3.4{sub −0.7}{sup +0.8}, respectively. This is inconsistent with the pressure equilibrium expected of a cold front and we conclude that the edge is a shock front. We measure a Mach number M=1.59{sub −0.07}{sup +0.06} and corresponding shock velocity v {sub shock} ≅ 2057 km s{sup –1}. Using spectra collected at the MMT with the Hectospec multi-object spectrograph, we identify 328 spectroscopically confirmed cluster members. Significantly, we find a local peak in the projected galaxy density associated with a bright cluster galaxy that is located just ahead of the nose of the shock. The data are consistent with a merger viewed within ∼23° of the plane of the sky. The merging subclusters are now moving apart along a north-south axis approximately 0.3 Gyr after a small impact parameter core passage. The gas core of the secondary subcluster, which was driving the shock, appears to have been disrupted by the merger. Without a driving 'piston,' we speculate that the shock is dying. Finally, we propose that the diffuse radio emission near the shock is due to the revival of pre-existing radio plasma that has been overrun by the shock.

  6. A Merger Shock in A2034

    NASA Astrophysics Data System (ADS)

    Owers, Matt S.; Nulsen, Paul E. J.; Couch, Warrick J.; Ma, Cheng-Jiun; David, Laurence P.; Forman, William R.; Hopkins, Andrew M.; Jones, Christine; van Weeren, Reinout J.

    2014-01-01

    We present a 250 ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front. The new data reveal that the edge is coherent over a larger opening angle and is significantly more bow-shock-shaped than previously thought. Within ~27° about the axis of symmetry of the edge, the density, temperature, and pressure drop abruptly by factors of 1.83^{+0.09}_{-0.08}, 1.85^{+0.41}_{-0.41}, and 3.4^{+0.8}_{-0.7}, respectively. This is inconsistent with the pressure equilibrium expected of a cold front and we conclude that the edge is a shock front. We measure a Mach number M = 1.59^{+0.06}_{-0.07} and corresponding shock velocity v shock ~= 2057 km s-1. Using spectra collected at the MMT with the Hectospec multi-object spectrograph, we identify 328 spectroscopically confirmed cluster members. Significantly, we find a local peak in the projected galaxy density associated with a bright cluster galaxy that is located just ahead of the nose of the shock. The data are consistent with a merger viewed within ~23° of the plane of the sky. The merging subclusters are now moving apart along a north-south axis approximately 0.3 Gyr after a small impact parameter core passage. The gas core of the secondary subcluster, which was driving the shock, appears to have been disrupted by the merger. Without a driving "piston," we speculate that the shock is dying. Finally, we propose that the diffuse radio emission near the shock is due to the revival of pre-existing radio plasma that has been overrun by the shock.

  7. A Reverse Shock in GRB 130427A

    NASA Astrophysics Data System (ADS)

    Laskar, Tanmoy; Berger, Edo; Zauderer, B. Ashley; Margutti, Raffaella; Soderberg, Alicia Margarita; Lunnan, Ragnhild; Chornock, Ryan

    2014-06-01

    We present extensive radio and millimeter observations of the unusually bright GRB 130427A at z=0.340, spanning 0.67 to 12 days after the burst. Taken in conjunction with detailed multi-band UV, optical, NIR, and X-ray observations we find that the broad-band afterglow emission is composed of distinct reverse shock and forward shock contributions. The reverse shock emission dominates in the radio/millimeter and at <0.1 days in the UV/optical/NIR, while the forward shock emission dominates in the X-rays and at >0.1 days in the UV/optical/NIR. We further find that the optical and X-ray data require a Wind circumburst environment, pointing to a massive star progenitor. Using the combined forward and reverse shock emission we find that the parameters of the burst are an isotropic kinetic energy of E_Kis 2e53 erg, a mass loss rate of Mdo 3e-8 Msun/yr (for a wind velocity of 1,000 km/s), and a Lorentz factor at the deceleration time of Gamma(200s 130. Due to the low density and large isotropic energy, the absence of a jet break to ~15 days places only a weak constraint on the opening angle of theta_j>2.5 deg, and therefore a total energy of E_gamma+E_K>1.2e51 erg, similar to other GRBs. The reverse shock emission is detectable in this burst due to the low circumburst density, which leads to a slow cooling shock. We speculate that this is a required property for the detectability of reverse shocks in the radio and millimeter bands. Following on GRB 130427A as a benchmark event, observations of future GRBs with the exquisite sensitivity of VLA and ALMA, coupled with detailed modeling of the reverse and forward shock contributions will test this hypothesis.

  8. Exogenous amino acids as fuel in shock.

    PubMed

    Daniel, A M; Kapadia, B; MacLean, L D

    1982-01-01

    It has been suggested that in shock branched-chain amino acids are preferentially oxidized resulting in continued proteolysis and stimulated gluconeogenesis. To determine if exogenous amino acids could be used as fuel in shock, dogs rendered hypotensive by controlled cardiac tamponade and normotensive controls were infused with amino acid mixtures and individual amino acids. When Nephramine, a mixture rich in branched-chain amino acids, was infused, plasma alpha-amino nitrogen levels rose but urea output did not increase in either the control state or in shock, suggesting that these amino acids were not rapidly deaminated to serve as fuels. Travasol, which in addition contained large amounts of alanine and glycine, tripled urea output in the controls and doubled it in shock. The limit of urea production was reached in both groups at 35 mumoles urea/minute/kg. In the Travasol-infused animals plasma alpha-amino nitrogen levels were maintained in normotension but rose sharply in shock. When glycine alone was infused into five dogs in shock urea production rate was 30.6 + 2.1 mumoles/minute/kg; with alanine the same value was 22.5 + 2.2 mumoles/minute/kg. In both cases plasma alpha-amino nitrogen levels were high, suggesting that transport of these amino acids into the cell was slow in shock. In four dogs in shock glycine-14C was added to the glycine infusate as a tracer. At radioactive equilibrium 28% of the label infused appeared in CO2; another 22% appeared in glucose. It is concluded that of all the amino acids tested only glycine and alanine are deaminated rapidly enough to serve as exogenous fuels in shock. PMID:6814205

  9. Screech Tones from Rectangular Jets with Spanwise Oblique Shock-Cell Structures

    NASA Technical Reports Server (NTRS)

    Raman, Ganesh

    1996-01-01

    Understanding screech is especially important for the design of advanced aircraft because screech can cause sonic fatigue failure of aircraft structures. Although the connection between shock-cell spacing and screech frequency is well understood, the relation between non-uniformities in the shock-cell structures and the resulting amplitude, mode, and steadiness of screech have remained unexplored. This paper addresses the above issues by intentionally producing spanwise (larger nozzle dimension) variations in the shock-cell structures and studying the resulting spanwise screech mode. The spanwise oblique shock-cell structures were produced using imperfectly expanded convergent-divergent rectangular nozzles (aspect ratio = 5) with nonuniform exit geometries. Three geometries were studied: (a) a nozzle with a spanwise uniform edge, (b) a nozzle with a spanwise oblique (single bevelled) edge, and (c) a nozzle that had two spanwise oblique (double bevelled) cuts to form an arrowhead-shaped nozzle. For all nozzles considered, the screech mode was antisymmetric in the transverse (smaller nozzle dimension) direction allowing focus on changes in the spanwise direction. Three types of spanwise modes were observed: symmetric (1), antisymmetric (2), and oblique (3). The following significant results emerged: (1) for all cases the screech mode corresponds with the spanwise shock-cell structure, (2) when multiple screech modes are present, the technique presented here makes it possible to distinguish between coexisting and mutually exclusive modes, (3) the strength of shocks 3 and 4 influences the screech source amplitude and determines whether screech is unsteady. The results presented here offer hope for a better understanding of screech and for tailoring shock-containing jets to minimize fatigue failure of aircraft components.

  10. Probing the Release of Shocked Material

    NASA Astrophysics Data System (ADS)

    Polsin, D. N.; McCoy, C. A.; Gregor, M. C.; Boehly, T. R.; Sangster, T. C.; Fratanduono, D. E.; Celliers, P. M.

    2014-10-01

    The behavior of shocked material as it releases to lower pressures is important for equation-of-state experiments and inertial confinement fusion research. We present results of experiments that used a 10-ps, 266-nm probe beam to image the release plumes of various target materials shocked to multi-megabar pressures by the OMEGA EP laser. Simultaneous VISAR (velocity interferometer system for any reflector) measurements provide the initial shocked state from which these materials release. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  11. Condensate Accretion in Shock Tube's Expansion Fan

    NASA Technical Reports Server (NTRS)

    Mezonlin, Ephrem-Denis; DeSilva, Upul P.; Hunte, F.; Johnson, Joseph A., III

    1997-01-01

    It has been shown that turbulence and temperature influence the droplet sizes in expansion fan induced condensation by studying the Rayleigh scattering from one port in our shock tube's test section. We have modified our set-up so as to allow, using two ports, the real time measurement of the influence of turbulence and temperature on the rate at which these droplets grow. To do this, we looked at the Rayleigh scattering from two different ports for ten Reynolds numbers at five different temperatures. We modeled the time of flight of droplets, using the equations of one-dimensional gas dynamics and the measured shock wave speed in shock tube's driven section.

  12. Ion acoustic shock waves in degenerate plasmas

    SciTech Connect

    Akhtar, N.; Hussain, S.

    2011-07-15

    Korteweg de Vries Burgers equation for negative ion degenerate dissipative plasma has been derived using reductive perturbation technique. The quantum hydrodynamic model is used to study the quantum ion acoustic shock waves. The effects of different parameters on quantum ion acoustic shock waves are studied. It is found that quantum parameter, electrons Fermi temperature, temperature of positive and negative ions, mass ratio of positive to negative ions, viscosity, and density ratio have significant impact on the shock wave structure in negative ion degenerate plasma.

  13. Turbulent energy generated by accelerations and shocks

    SciTech Connect

    Mikaelian, K.O.

    1986-10-08

    The turbulent energy generated at the interface between two fluids undergoing a constant acceleration or a shock is calculated. Assuming linear density profiles in the mixed region we find E/sub turbulent//E/sub directed/ = 2.3A/sup 2/% (constant acceleration) and 9.3A/sup 2/% (shock), where A is the Atwood number. Diffusion models predict somewhat less turbulent energy and a density profile with a tail extending into the lower density fluid. Eddy sizes are approximately 27% (constant acceleration) and 17% (shock) of the mixing depth into the heavier fluid. 6 refs., 3 figs.

  14. Coherent Raman Studies of Shocked Liquids

    NASA Astrophysics Data System (ADS)

    McGrane, Shawn; Brown, Kathryn; Dang, Nhan; Bolme, Cynthia; Moore, David

    2013-06-01

    Transient vibrational spectroscopies offer the potential to directly observe time dependent shock induced chemical reaction kinetics. We report recent experiments that couple a hybrid picosecond/femtosecond coherent anti-Stokes Raman spectroscopy (CARS) diagnostic with our tabletop ultrafast laser driven shock platform. Initial results on liquids shocked to 20 GPa suggest that sub-picosecond dephasing at high pressure and temperature may limit the application of this nonresonant background free version of CARS. Initial results using interferometric CARS to increase sensitivity and overcome these limitations will be presented.

  15. Impact processes and lunar magnetism. [shock effects

    NASA Technical Reports Server (NTRS)

    Cisowski, C. S.; Dunn, J. R.; Fuller, M.; Rose, M. F.; Wasilewski, P. J.

    1974-01-01

    Progress reports are presented of work related to the magnetic characterization of lunar samples, taking into account total iron ratios, questions of hysteresis classification, aspects of normalized remanence to remanent coercivity plots, and a comparison of NRM of lunar samples with hysteresis characterization. Shock experiments on lunar soil are also considered, giving attention to the effect of shock on the magnetic characteristics of lunar soil and the acquisition of remanence during shock. Preliminary measurements of individual soil particles and of samples from the Lunar Crater are discussed.

  16. Nonequilibrium volumetric response of shocked polymers

    SciTech Connect

    Clements, B E

    2009-01-01

    Polymers are well known for their non-equilibrium deviatoric behavior. However, investigations involving both high rate shock experiments and equilibrium measured thermodynamic quantities remind us that the volumetric behavior also exhibits a non-equilibrium response. Experiments supporting the notion of a non-equilibrium volumetric behavior will be summarized. Following that discussion, a continuum-level theory is proposed that will account for both the equilibrium and non-equilibrium response. Upon finding agreement with experiment, the theory is used to study the relaxation of a shocked polymer back towards its shocked equilibrium state.

  17. Comparison of Modern Methods for Shock Hydrodynamics

    SciTech Connect

    Cook, A W

    2005-06-13

    The accuracy and efficiency of several methods are compared for simulating multifluid compressible flows. The methods include a Godunov scheme (Colella, 1985), a Weighted Essentially Non-Oscillatory method (Jiang and Shu, 1996), an Arbitrary Lagrangian Eulerian algorithm (Marinak et al., 2001) and a compact scheme (Cook and Cabot, 2005). Test problems include a compressible breaking wave, the Shu-Osher problem, the Taylor-Green vortex and decaying turbulence. The compact method employs an artificial bulk viscosity for treating shocks and an artificial shear viscosity for modeling turbulence. The compact method is demonstrated to capture shocks as well as the other schemes, while providing superior resolution of post-shock features.

  18. Gated IR Images of Shocked Surfaces

    SciTech Connect

    S. S. Lutz; W. D. Turley; P. M. Rightley; L. E. Primas

    2001-06-01

    Gated infrared (IR) images have been taken of a series of shocked surface geometries in tin. Metal coupons machined with steps and flats were mounted directly to the high explosive. The explosive was point-initiated and 500-ns to 1-microsecond-wide gated images of the target were taken immediately following shock breakout using a Santa Barbara Focalplane InSb camera (SBF-134). Spatial distributions of surface radiance were extracted from the images of the shocked samples and found to be non-single-valued. Several geometries were modeled using CTH, a two-dimensional Eulerian hydrocode.

  19. Best Practices for Unstructured Grid Shock Fitting

    NASA Technical Reports Server (NTRS)

    McCloud, Peter L.

    2017-01-01

    Unstructured grid solvers have well-known issues predicting surface heat fluxes when strong shocks are present. Various efforts have been made to address the underlying numerical issues that cause the erroneous predictions. The present work addresses some of the shortcomings of unstructured grid solvers, not by addressing the numerics, but by applying structured grid best practices to unstructured grids. A methodology for robust shock detection and shock fitting is outlined and applied to production relevant cases. Results achieved by using the Loci-CHEM Computational Fluid Dynamics solver are provided.

  20. Outdoor measurements of spherical acoustic shock decay.

    PubMed

    Young, Sarah M; Gee, Kent L; Neilsen, Tracianne B; Leete, Kevin M

    2015-09-01

    Prior anechoic measurements of a small acetylene-oxygen balloon explosion were used to study spherical weak-shock decay over short ranges [Muhlestein et al., J. Acoust. Soc. Am. 131, 2422-2430 (2012)]. Here, longer-range measurements conducted at the Bonneville Salt Flats with a larger balloon are described. Waveform and spectral characteristics and comparisons of the peak pressure decay with an analytical weak-shock model are presented. Weak shocks persist to at least 305 m, with an amplitude decay that is predicted reasonably well using the model. Deviations are discussed in the context of atmospheric effects and nonlinear ground reflections. PMID:26428831