Search results for "Shocks"

Complex singularities and PDEs

2015

In this paper we give a review on the computational methods used to capture and characterize the complex singularities developed by some relevant PDEs. We begin by reviewing the classical singularity tracking method and give an example of application using the Burgers equation as a case study. This method is based on the analysis of the Fourier spectrum of the solution and it allows to determine and characterize the complex singularity closest to the real domain. We then introduce other methods generally used to detect the hidden singularities. In particular we show some applications of the Padé approximation, of the Kida method, and of Borel-Polya method. We apply these techniques to the s…

Reduction of ICD Shock Burden by Eliminating Back-Up Pacing Induced Ventricular Tachyarrhythmias

2014

ICD Shock Reduction by Subthreshold Pacing Introduction Implantable cardioverter defibrillators (ICD) may have the capacity to provoke or worsen ventricular tachyarrhythmias (VT). It has been reported that ICD shocks by itself can increase mortality. This study aimed to determine the role of back-up pacing-induced VT (PIT) in the overall ICD shock burden by avoiding pause-related ventricular back-up pacing. Methods and Results A population of 550 single-chamber ICD patients was studied. Of them, 17 (3%, 69 ± 16 years, 14 male) patients had documented episodes of PIT. A total of 431 VT episodes were documented including 89 (21%) due to PIT. In 3 patients, VT events were exclusively PITs. Aft…

Additional Evidence for a Pulsar Wind Nebula in the Heart of SN 1987A from Multiepoch X-Ray Data and MHD Modeling

2022

Since the day of its explosion, supernova (SN) 1987A has been closely monitored to study its evolution and to detect its central compact relic. In fact, the formation of a neutron star is strongly supported by the detection of neutrinos from the SN. However, besides the detection in the Atacama Large Millimeter/submillimeter Array (ALMA) data of a feature that is compatible with the emission arising from a proto-pulsar wind nebula (PWN), the only hint for the existence of such elusive compact object is provided by the detection of hard emission in NuSTAR data up to ~ 20 keV. We report on the simultaneous analysis of multi-epoch observations of SN 1987A performed with Chandra, XMM-Newton and…

Accretion shock on CTTSs and its X-ray emission

2009

High spectral resolution X-ray observations of classical T Tauri stars (CTTSs) demonstrate the presence of plasma at T~2-3×10^6 K and ne~10^11-10^13 cm-3. Stationary models suggest that this emission is due to shock-heated accreting material. We address this issue by a 1-D hydrodynamic model of the impact of the accretion flow onto a chromosphere of a CTTS with the aim of investigating the stability of accretion shock and the role of the chromosphere. Our simulations include the effects of gravity, radiative losses from optically thin plasma, the thermal conduction and a detailed modeling of the stellar chromosphere. Here we present the results of a simulation based on the parameters of the…

The nearest X-ray emitting protostellar jet observed with HST

2009

The HH 154 jet coming from the YSO binary L1551 IRS5 is one of the closest (about 150 pc) astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks forming at the interaction front between the expanding material and the ambient medium. The substructures (knots) observed within the HH 154 jet were imaged in several spectral bands using the Hubble Space Telescope. This allows us to derive a simple characterization of the physical conditions in different structures as well as to measure the proper motion of the knots in the jet, their flux variability and shock emission over a time base of about ten years. These knots in the jet undergo si…

MHD modelling of plasma flowing in coronal magnetic channels

Effect of long-term salinity increase on nitritation and denitritation kinetics in activated sludge and granular sludge reactors

2017

The aim of this work was to investigate the effects of moderate and drastic long-termincrease of salinity.Particularly, the study was aimed at assessing the shock effecton nitritationand denitritation kineticsof halophilic biomass inboth forms:flocculent activated sludge and granular sludge.

Hydrodynamic simulations of the shock-cloud interaction in the Vela supernova remnant

2005

Monetary policy and exchange rate dynamics in the Spanish economy

1999

As the Spanish economy gets more integrated in international markets, the real exchange rate becomes a key determinant of the monetary transmission. In this paper we trace out the dynamic response of prices, output and the exchange rate following a monetary policy shock. We estimate a structural VAR model whose identification scheme is based on the long run properties common to a large class of models. The results suggest that a small model with efficient asset markets plus nominal inertia and long run monetary neutrality, captures the essential features of the monetary transmission mechanism in Spain. The interest rate shock is well identified and the exchange rate overshoots its long run …

BEMOD: A DSGE Model for the Spanish Economy and the Rest of the Euro Area

2006

In this paper we present the theoretical foundations and the simulation results obtained with a new dynamic general equilibrium model developed at the Banco de España for the Spanish economy and the rest of Euro area. The model is designed to help in simulating the effect of alternative shocks on the main aggregate variables. The main contributions of this work from a theoretical perspective are the modelling of a monetary union composed of two regions, the inclusion of housing as a durable good with its own sector of production and the degree and detail of the disaggregation considered for each country in the model, which replicates the Quarterly National Accounts. On the empirical side, t…