Shock Origin Research Articles

Cristaloides y coloides en la reanimación del paciente crítico

Fluid resuscitation is essential for the survival of critically ill patients in shock, regardless of the origin of shock. A number of crystalloids and colloids (synthetic and natural) are currently available, and there is strong controversy regarding which type of fluid should be administered and the potential adverse effects associated with the use of these products, especially the development of renal failure requiring renal replacement therapy. Recently, several clinical trials and metaanalyses have suggested the use of hydroxyethyl starch (130/0.4) to be associated with an increased risk of death and kidney failure, and data have been obtained showing clinical benefit with the use of crystalloids that contain a lesser concentration of sodium and chlorine than normal saline. This new information has increased uncertainty among clinicians regarding which type of fluid should be used. We therefore have conducted a review of the literature with a view to developing practical recommendations on the use of fluids in the resuscitation phase in critically ill adults.

A HARD X-RAY POWER-LAW SPECTRAL CUTOFF IN CENTAURUS X-4

The low-mass X-ray binary Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0.5-10 keV X-ray observations of Cen X-4 in quiescence identified two spectral components: soft thermal emission from the neutron star atmosphere and a hard power-law tail of unknown origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1 x 10^(33) erg/s (for D=1kpc), with around 60 percent in the thermal component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. We show that thermal Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X-ray spectrum is well fit by a thermal bremsstrahlung model with an 18 keV electron temperature, which can be understood as arising either in a hot layer above the neutron star atmosphere or in a radiatively-inefficient accretion flow (RIAF). The power-law cutoff energy may be set by the degree of Compton cooling of the bremsstrahlung electrons by thermal seed photons from the neutron star surface. Lower thermal luminosities should lead to higher (possibly undetectable) cutoff energies. We compare Cen~X-4's behavior with PSR J1023+0038, IGR J18245-2452, and XSS J12270-4859, which have shown transitions between LMXB and radio pulsar modes at a similar X-ray luminosity.

Artificial viscosity: back to the basics

SummaryIn this paper, we take a different perspective on the derivation of artificial viscosity. Heretofore, the development of artificial viscosity has been based on the paper published in Journal of Applied Physics in 1950 authored by John von Neumann and Robert Richtmyer [1]. Earlier, in 1948, Richtmyer published a report at Los Alamos Scientific Laboratory documenting the original concept [2]. This report was the true origin of shock capturing methods and contains several key ideas that are conceptually different than the 1950 journal article. Unfortunately, this report (LA‐671) was classified until 1993. This has resulted in two issues: the misattribution of the invention of artificial viscosity as primarily being the work of von Neumann and the loss of the structurally different ideas in the original report. We seek to right the record of history here and use the ideas contained in Richtmyer's report to good effect in deriving a new shock viscosity. The focus of previous development has been the Hugoniot curve describing the locus of states connected by a single shock wave. Here we follow a path more focused upon the Rayleigh line, which is strongly guided by Richtmyer's line of development of the original artificial viscosity formulation. We provide an implementation of the method resulting from this perspective and computational results for simple shock problems. Copyright © 2014 John Wiley &amp; Sons, Ltd.

GRB 120711A: an intense INTEGRAL burst with long-lasting softγ-ray emission and a powerful optical flash

A long and intense gamma-ray burst (GRB) was detected by INTEGRAL on July 11 2012 with a duration of ~115s and fluence of 2.8x10^-4 erg cm^-2 in the 20 keV-8 MeV energy range. GRB 120711A was at z~1.405 and produced soft gamma-ray emission (>20 keV) for at least ~10 ks after the trigger. The GRB was observed by several ground-based telescopes that detected a powerful optical flash peaking at an R-band brightness of ~11.5 mag at ~126 s after the trigger. We present a comprehensive temporal and spectral analysis of the long-lasting soft gamma-ray emission detected in the 20-200 keV band with INTEGRAL, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow from XMM-Newton, Chandra, and Swift and the optical/NIR detections from Watcher, Skynet, GROND, and REM. We modelled the long-lasting soft gamma-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the NIR to GeV energies suggest that the emission is produced by a broken power-law spectrum consistent with synchrotron radiation. The afterglow is well modelled using a stratified wind-like environment with a density profile k~1.2, suggesting a massive star progenitor (i.e. Wolf-Rayet). The analysis of the reverse and forward shock emission reveals an initial Lorentz factor of ~120-340, a jet half-opening angle of ~2deg-5deg, and a baryon load of ~10^-5-10^-6 Msun consistent with the expectations of the fireball model when the emission is highly relativistic. Long-lasting soft gamma-ray emission from other INTEGRAL GRBs with high peak fluxes, such as GRB 041219A, was not detected, suggesting that a combination of high Lorentz factor, emission above 100 MeV, and possibly a powerful reverse shock are required. Similar long-lasting soft gamma-ray emission has recently been observed from the nearby and extremely bright Fermi/LAT burst GRB 130427A.

Imaging the high‐frequency energy radiation process of a main shock and its early aftershock sequence: The case of the 2008 Iwate‐Miyagi Nairiku earthquake, Japan

AbstractTo understand the energy release process that operates at the end of the main shock rupture and start of the aftershock activity, we propose an inversion method that uses continuous high‐frequency seismogram envelopes of the main shock and early aftershocks (i.e., events that occur at short times after the main shock). In our approach, the aftershock sequence is regarded as a continuous energy release process, rather than a discrete time series of events. To correct for the contribution of coda wave energy excited by multiple scattering, we use the theoretical envelope synthesized on the basis of the radiative transfer theory as a Green's function. The site amplification factors are corrected considering the conservation of energy flux and using the coda normalization method. The inverted temporal energy release rate for the 2008 MW 6.9 Iwate‐Miyagi Nairiku earthquake, Japan, decays following t−1.1, at the lapse time t of 40–900 s after the main shock origin time. This exponent of the decay rate is similar to the p value of the modified Omori law. The amount of estimated energy release is consistent with that calculated from the magnitude listed in the aftershock catalog. Although the uncertainty is large, the location of large energy release at the lapse times of 40–900 s approximately overlaps to that of the aftershocks, which surrounds the large energy release area during the main shock faulting. The maxima of the energy release rate normalized by the average decay rate distributes following a power law, similar to the Gutenberg‐Richter law.

A discussion of “Inter-industry network structure and the cross-predictability of earnings and stock returns”

Aobdia et al. (Rev Account Stud, 2014) view the economy as a network of customers and suppliers. Using the 1997 input–output trade flow data from the Bureau of Economic Analysis to model the inter-industry network, they examine whether an industry’s position in the network, in particular, its “network centrality,” affects the transmission of information and economic shocks. They find that, compared to the accounting performance and stock returns of noncentral industries, those of central industries are explained by aggregate risks to a greater extent and are more highly associated with the contemporaneous and future performance of their linked industries. These findings suggest that network centrality matters—it plays an important role in how economic shocks are transmitted within the economy. The question of why network centrality matters, however, remains unanswered. A fruitful avenue for future research is to explore the origin of shocks to shed light on the fundamental question of whether sectoral shocks can aggregate into macro shocks.

Poster #M119 PRENATAL AND POSTNATAL EXPOSURES TO MAXIMUM ADVERSITY AMONG HOLOCAUST SURVIVORS AND THE COURSE OF SCHIZOPHRENIA: A POPULATION-BASED STUDY

The challenges faced by agricultural systems call for an advance in risk management (RM) assessments. This research identifies and discusses potential improvements to RM across 11 European Union (EU) farming systems (FS). The paper proposes a comprehensive, participatory approach that accounts for multi-stakeholder perspectives relying on 11 focus groups for brainstorming and gathering suggestions to improve RM. Data analysis is based on content analysis and coding of suggested improvements, and their assessment through the lenses of main challenges faced, farms’ flexibility, and dependence on subsidies. First, the results show that necessary improvements differ depending on whether they have their origin in sudden shocks or long-term pressures. Second, farm dependence on direct payments determines a stronger need to improve financial instruments, whereas farm flexibility suggests a need for more accessible and tailored tools for low-flexibility FS, and increased know-what and know-how for high-flexibility FS. Third, our findings indicate a potential for extending stakeholder involvement in RM to new or unconventional roles. Underlying specific improvements, the paper suggests and discusses three main avenues to improve RM as a whole: i) a developed learning and knowledge network; ii) new forms of collaboration; and iii) integrated financial and policy instruments.

Oil price shocks and Nigeria's stock market: what have we learned from crude oil market shocks?

AbstractOil price shocks do not only originate from the supply‐side of the crude oil market but may also be demand driven. The impact of oil price shocks on stock market activities may be different depending on its origin (i.e. demand and supply shocks). This paper provides the first examination of the impact of the origin of oil price shocks on Nigeria's stock market for the period 1995:1–2011:12. Oil price shocks is decomposed into oil supply shocks, aggregate demand shocks and oil‐specific demand shocks using a structural vector auto‐regression model, and their impacts on stock market prices were analysed using impulse response and variance decomposition analysis. The impulse response results show that stock market's response to oil supply shocks is insignificantly negative but significantly positive to aggregate demand and oil‐specific demand shocks. The cumulative effects of the oil price shocks account for about 47 per cent of the variation in stock prices in the long term. These results suggest that the origin of oil price shocks is crucial for understanding the volatility in Nigeria's stock market. Future policy direction should focus on diversifying the economy to reduce its vulnerability to oil price fluctuations while addressing the inefficiencies in the stock market.

Dynamic Spillover Between The Oil And Stock Markets Of Emerging Oil-Exporting Countries

&lt;p&gt;The paper investigates the time-varying correlations between stock market returns and oil prices in oil-exporting countries. A multivariate GARCH-DCC process is employed to evaluate this relationship based on data from Venezuela, the United Arab Emirates, Saudi Arabia and Kuwait. The results show that there are time-varying correlations between the oil and stock markets in emerging, oil-producing countries, indicating that they are affected by conditions in world markets. In addition, the relationship between oil prices and stock returns is found to be influenced by the origin of shocks to oil prices, with stock market responses being stronger to demand-side shocks caused by political turmoil or fluctuations in the global business cycle than to supply-side shocks caused by cuts in oil production. The results also provide evidence of volatility spillovers between the oil and stock markets.&lt;/p&gt;

High-pressure polymorph of TiO2-II from the Xiuyan crater of China

Abundant TiO2-II, a high-pressure polymorph of titanium dioxide, was found in the gneiss fragments of impact-produced breccias from the Xiuyan crater. Rutile in the gneiss was severely fragmented and fine-grained clasts less than 2 μm in size had been transformed to TiO2-II. Irregular thin layered TiO2-II is also observed in coarse-grained rutile fragments, where the TiO2-II layers distributes along fractures and cracks in rutile. About 30 percent of rutile in the gneiss had been transformed to TiO2-II. Fine grains of TiO2-II display light bluish grey to light yellow brown in plane-polarized reflected light. Crystallographic investigation shows that TiO2-II has an orthorhombic structure with space group Pbcn. The cell parameters are a=4.543(1) A, b=5.491(9) A and c=4.895(2) A. Its empirical formula calculated on the basis of two oxygen atoms can be written as (Ti0.985Fe0.008Nb0.006-Si0.003Zr0.001)1.003O2, or simply formula TiO2. According to the shock effects of quartz and feldspars, the peak shock pressure and post-shock temperature in the TiO2-II-bearing gneiss are estimated to be between 35 and 43 GPa and 300–900°C, respectively. The finding of TiO2-II in the shock-metamorphosed gneiss provides another mineral physics evidence for shock origin of the Xiuyan crater.

L1448-MM OBSERVATIONS BY THE HERSCHEL KEY PROGRAM, “DUST, ICE, AND GAS IN TIME” (DIGIT)

We present Herschel/PACS observations of L1448-MM, a Class 0 protostar with a prominent outflow. Numerous emission lines are detected at 55 < lambda < 210 micrometer including CO, OH, H2O, and [O I]. We investigate the spatial distribution of each transition to find that lines from low energy levels tend to distribute along the outflow direction while lines from high energy levels peak at the central spatial pixel. Spatial maps reveal that OH emission lines are formed in a relatively small area, while [O I] emission is extended. According to the rotational diagram analysis, the CO emission can be fitted by two (warm and hot) temperature components. For H2O, the ortho-to-para ratio is close to 3. The non-LTE LVG calculations suggest that CO and H2O lines could instead be formed in a high kinetic temperature (T > 1000 K) environment, indicative of a shock origin. For OH, IR-pumping processes play an important role in the level population. The molecular emission in L1448-MM is better explained with a C-shock model, but the atomic emission of PACS [O I] and Spitzer/IRS [Si II] emission is not consistent with C-shocks, suggesting multiple shocks in this region. Water is the major line coolant of L1448-MM in the PACS wavelength range, and the best-fit LVG models predict that H2O and CO emit (50-80)% of their line luminosity in the PACS wavelength range.

Disk-halo interactions: molecular clouds in the Galactic center

AbstractWe study the disk-halo interaction, in the context of orbits and Giant Molecular loops (GMLs) in the Galactic center (GC) region. From a large scale survey of the central kpc of the Galaxy, in SiO J = (2 − 1), HCO+J = (1 − 0) and H13CO+J = (1 − 0) molecular emission, we identify shock regions traced by the enhancement of the SiO. These positions were studied using the 12C/13C isotopic ratio to trace gas accretion/ejection. We found a systematically higher 12C/13C isotopic ratio (&gt; 40) toward the GMLs and the x1 orbits than for the GC standard molecular clouds (20–25). The high isotopic ratios are consistent with the accretion of the gas from the halo and from the outskirts of the Galactic disk. From multi-transitional observations of NH3, we derive two kinetic temperature regimes (one warm at ∼150 K and one cold at ∼40 K) for all the positions, except for the GMLs positions where only the warm component is present. The fractional abundances derived from the different molecules support the shock origin for the heating mechanism in the GC. We also present a detailed study of one molecular cloud placed in the foot points of two giant molecular loops, where two of the previously selected positions are placed. Using the 22m Mopra telescope we mapped the molecular cloud M − 3.8 + 0.9 in 3-mm molecular lines. The data show structures at small scale in SiO emission, with narrower line profiles than those of, e.g, HCO+ or HCN, which indicate that the shocks are dynamically confined. The data also show clear differences between different molecular tracers, e.g., between the SiO and HCO+ emission, which would indicate differences in the physical properties and chemistry within the cloud.

On-axis time-resolved spatial characterization of shock-induced refractive fringes in liquid water

We report here the on-axis measurement of time-resolved spatial characterization of refractive fringes due to nanosecond-laser-induced shock waves in liquid water. The complex shadowgraphic fringes due to interference of multiple shock waves observed in the transverse measurements are completely avoided in the on-axis measurements due to the fact that the outermost region of the shock front acts as a radially symmetric phase object to the probe beam, refraction from which results in clean and continuous fringes observed by the intensified charge coupled detector (ICCD) detector. A detailed analysis of different types of time-resolved fringes obtained in the on-axis measurement for fixed laser pulse energy leads us to an alternate and better way to analyze the fringes to obtain the shock wave velocity and the density profile in the entire region surrounding the shock origin, which will enable 3D imaging of shock wave dynamics.

GRB 090727 AND GAMMA-RAY BURSTS WITH EARLY-TIME OPTICAL EMISSION

We present a multi-wavelength analysis of gamma-ray burst GRB 090727, for which optical emission was detected during the prompt gamma-ray emission by the 2-m autonomous robotic Liverpool Telescope and subsequently monitored for a further two days with the Liverpool and Faulkes telescopes. Within the context of the standard fireball model, we rule out a reverse shock origin for the early time optical emission in GRB 090727 and instead conclude that the early time optical flash likely corresponds to emission from an internal dissipation processes. Putting GRB 090727 into a broader observational and theoretical context, we build a sample of 36 gamma-ray bursts (GRBs) with contemporaneous early time optical and gamma-ray detections. From these GRBs, we extract a sub-sample of 18 GRBs, which show optical peaks during prompt gamma-ray emission, and perform detailed temporal and spectral analysis in gamma-ray, X-ray, and optical bands. We find that in most cases early time optical emission shows sharp and steep behaviour, and notice a rich diversity of spectral properties. Using a simple internal shock dissipation model, we show that the emission during prompt GRB phase can occur at very different frequencies via synchrotron radiation. Based on the results obtained from observations and simulation, we conclude that the standard external shock interpretation for early time optical emission is disfavoured in most cases due to sharp peaks ($\Delta t/t < 1$) and steep rise/decay indices, and that internal dissipation can explain the properties of GRBs with optical peaks during gamma-ray emission.

Oil and stock returns: Evidence from European industrial sector indices in a time-varying environment

The time-varying correlation between oil prices returns and European industrial sector indices returns, considering the origin of the oil price shock, is investigated. A time-varying multivariate heteroskedastic framework is employed to test the above hypothesis based on data from 10 European sectors. The contemporaneous correlations suggest that the relationship between sector indices and oil prices change over time and they are industry specific. In addition, the supply-side oil price shocks result in low to moderate positive correlation levels, the precautionary demand oil price shocks lead to almost zero correlation levels, whereas the aggregate demand oil price shocks generate significant changes in the correlation levels (either positive or negative). Both the origin of the oil price shock and the type of industry are important determinants of the correlation level between industrial sectors’ returns and oil prices. Prominent among the results is the fact that during the financial crisis of 2008 some sectors were providing diversification opportunities to investors dealing with the crude oil market.

RADIO MONITORING OF THE TIDAL DISRUPTION EVENT SWIFT J164449.3+573451. II. THE RELATIVISTIC JET SHUTS OFF AND A TRANSITION TO FORWARD SHOCK X-RAY/RADIO EMISSION

We present continued multi-frequency radio observations of the relativistic tidal disruption event Sw1644+57 extending to dt~600 d. The data were obtained with the JVLA and AMI Large Array. We combine these data with public Swift/XRT and Chandra X-ray observations over the same time-frame to show that the jet has undergone a dramatic transition starting at ~500 d, with a sharp decline in the X-ray flux by about a factor of 170 on a timescale of dt/t<0.2. The rapid decline rules out a forward shock origin (direct or reprocessing) for the X-ray emission at <500 d, and instead points to internal dissipation in the inner jet. On the other hand, our radio data uniquely demonstrate that the low X-ray flux measured by Chandra at ~610 d is consistent with emission from the forward shock. Furthermore, the Chandra data are inconsistent with thermal emission from the accretion disk itself since the expected temperature of 30-60 eV and inner radius of 2-10 R_s cannot accommodate the observed flux level or the detected emission at >1 keV. We associate the rapid decline with a turn off of the relativistic jet when the mass accretion rate dropped below Mdot_Edd~0.006 Msun/yr (for a 3x10^6 Msun black hole and order unity efficiency) indicating that the peak accretion rate was about 330 Mdot_Edd, and the total accreted mass by 500 d is about 0.15 Msun. From the radio data we further find significant flattening in the integrated energy of the forward shock at >250 d with E_j,iso~2x10^54 erg (E_j~10^52$ erg for a jet opening angle, theta_j=0.1) following a rise by about a factor of 15 at 30-250 d. Projecting forward, we predict that the emission in the radio and X-ray bands will evolve in tandem with similar decline rates.

Transformation of graphite to lonsdaleite and diamond in the Goalpara ureilite directly observed by TEM

This study reports on the structural relationship between graphite, lonsdaleite, and diamond extracted from the Goalpara ureilite and propose a model for the formation of lonsdaleite and diamond in these stony meteorites. The study is based on data from reflected-light microscopy and laser Raman spectroscopy of a polished thin section (PTS) of the Goalpara ureilite and X-ray powder diffraction (XRPD) analyses of the grains taken out of it. Selected-area electron diffraction (SAED) analyses and high-resolution TEM (HRTEM) observations were carried out in the three unique directions of pristine graphite with two thin slices prepared from a carbon grain directly taken out of a PTS. SAED patterns reveal the relative crystal-axes orientations between graphite (Gr), lonsdaleite (Lo), and diamond (Di) as (001)Gr//(100)Lo//(111)Di, [210]Gr//[001]Lo//[21̅1̅]Di, and (12̅0)Gr//(1̅20)Lo//(02̅2)Di. The shapes of diffraction spots in the SAED patterns reveal that the transformation of graphite to lonsdaleite and diamond is initiated by sliding of hexagonal carbon planes of graphite along the [210] of the graphite structure. These results suggest that lonsdaleite and diamond in ureilites formed directly from graphite through boat-type buckling and chair-type puckering of hexagonal carbon planes of graphite, respectively. The results of this study confirm the shock origin of diamond in ureilites.

Diffusive Ion Acceleration by CME‐Driven Shocks

The acceleration of solar energetic ions in events at coronal/ interplanetary shocks is reviewed including: a brief observational motivation for a shock origin of gradual events, the historical development of the theory of shock acceleration as applied to solar energetic particles, the basic features of the process of diffusive shock acceleration (first-order Fermi acceleration at the shock, wave excitation by the energetic protons, magnetic focusing and upstream escape of the ions), challenges to developing a successful theory, the basic equations of ion transport and acceleration, and current theoretical research. Finally, outstanding issues which must be addressed by future work are listed including: ion injection into the process of diffusive shock acceleration, careful evaluation of the wave intensity upstream of the shock, acceleration and injection at quasi-perpendicular shocks, long-time behavior of gradual events, the inclusion of wave propagation velocities in the effective shock compression ratio, and a rigorous treatment of the time-dependence.

OH far-infrared emission from low- and intermediate-mass protostars surveyed withHerschel-PACS

OH is a key species in the water chemistry of star-forming regions, because its presence is tightly related to the formation and destruction of water. This paper presents OH observations from 23 low- and intermediate-mass young stellar objects obtained with the PACS integral field spectrometer on-board Herschel in the context of the Water In Star-forming Regions with Herschel (WISH) key program. Most low-mass sources have compact OH emission (< 5000 AU scale), whereas the OH lines in most intermediate-mass sources are extended over the whole PACS detector field-of-view (> 20000 AU). The strength of the OH emission is correlated with various source properties such as the bolometric luminosity and the envelope mass, but also with the OI and H2O emission. Rotational diagrams for sources with many OH lines show that the level populations of OH can be approximated by a Boltzmann distribution with an excitation temperature at around 70 K. Radiative transfer models of spherically symmetric envelopes cannot reproduce the OH emission fluxes nor their broad line widths, strongly suggesting an outflow origin. Slab excitation models indicate that the observed excitation temperature can either be reached if the OH molecules are exposed to a strong far-infrared continuum radiation field or if the gas temperature and density are sufficiently high. Using realistic source parameters and radiation fields, it is shown for the case of Ser SMM1 that radiative pumping plays an important role in transitions arising from upper level energies higher than 300 K. The compact emission in the low-mass sources and the required presence of a strong radiation field and/or a high density to excite the OH molecules points towards an origin in shocks in the inner envelope close to the protostar.

Oil and Stock Price Returns: Evidence from European Industrial Sector Indices in a Time-Varying Environment

The time-varying correlation between oil prices returns and European industrial sector indices returns, considering the origin of the oil price shock, is investigated. A time-varying multivariate heteroskedastic framework is employed to test the above hypothesis based on data from 10 European sectors. The contemporaneous correlations suggest that the relationship between sector indices and oil prices change over time and they are industry specific. In addition, the supply-side oil price shocks result in low to moderate positive correlation levels, the precautionary demand oil price shocks lead to almost zero correlation levels, whereas the aggregate demand oil price shocks generate significant changes in the correlation levels (either positive or negative). Both the origin of the oil price shock and the type of industry are important determinants of the correlation level between industrial sectors’ returns and oil prices. Prominent among the results is the fact that during the financial crisis of 2008 some sectors were providing diversification opportunities to investors dealing with the crude oil market.