45 research outputs found
Time evolution of the anisotropies of the hydrodynamically expanding sQGP
In high energy heavy ion collisions of RHIC and LHC, a strongly interacting
quark gluon plasma (sQGP) is created. This medium undergoes a hydrodynamic
evolution, before it freezes out to form a hadronic matter. The initial state
of the sQGP is determined by the initial distribution of the participating
nucleons and their interactions. Due to the finite number of nucleons, the
initial distribution fluctuates on an event-by-event basis. The transverse
plane anisotropy of the initial state can be translated into a series of
anisotropy coefficients or eccentricities: second, third, fourth-order
anisotropy etc. These anisotropies then evolve in time, and result in
measurable momentum-space anisotropies, to be measured with respect to their
respective symmetry planes. In this paper we investigate the time evolution of
the anisotropies. With a numerical hydrodynamic code, we analyze how the speed
of sound and viscosity influence this evolution.Comment: 10 pages, 6 figures. To appear in the Gribov-85 Memorial Workshop's
proceedings volume. Supported by OTKA NK 10143
A Remarkable Angular Distribution of the Intermediate Subclass of Gamma‐Ray Bursts
We develop a method of testing the null hypothesis of intrinsic randomness in the angular distribution of gamma-ray bursts collected in the Current BATSE Catalog. The method is a modified version of the well-known counts-in-cells test and fully eliminates the nonuniform sky-exposure function of the BATSE instrument. Applying this method to the case of all gamma-ray bursts, we found no intrinsic nonrandomness. The test also did not find intrinsic nonrandomness for the short and long gamma-ray bursts. However, using the method on the new, intermediate subclass of gamma-ray bursts, the null hypothesis of intrinsic randomness for 181 intermediate gamma-ray bursts is rejected on the 96.4% confidence level. Taking 92 dimmer bursts from this subclass, we obtain a surprising result: this "dim" subclass of the intermediate subclass has an intrinsic nonrandomness on the 99.3% confidence level. On the other hand, the 89 "bright" gamma-ray bursts show no intrinsic nonrandomness
Higher order anisotropies in hydrodynamics
In the last years it has been revealed that if measuring relative to higher order event planes Ψn, higher order flow coefficients vn for n > 2 can be measured. It also turned out that Bose-Einstein (HBT) correlation radii also show 3rd order oscillations if measured versus the third order event plane Ψ3. In this paper we investigate how these observables can be described via analytic hydro solutions and hydro parameterizations. We also investigate the time evolution of asymmetry coefficients and the mixing of velocity field asymmetries and density asymmetries
Factor analysis of the spectral and time behavior of long GRBs
A sample of 197 long BATSE GRBs is studied statistically. In the sample 11
variables, describing for any burst the time behavior of the spectra and other
quantities, are collected. The application of the factor analysis on this
sample shows that five factors describe the sample satisfactorily. Both the
pseudo-redshifts coming from the variability and the Amati-relation in its
original form are disfavored.Comment: In GAMMA-RAY BURSTS 2007: Proceedings of the Santa Fe Conferenc
New Statistical Results on the Angular Distribution of Gamma-Ray Bursts
We presented the results of several statistical tests of the randomness in
the angular sky-distribution of gamma-ray bursts in BATSE Catalog. Thirteen
different tests were presented based on Voronoi tesselation, Minimal spanning
tree and Multifractal spectrum for five classes (short1, short2, intermediate,
long1, long2) of gamma-ray bursts, separately. The long1 and long2 classes are
distributed randomly. The intermediate subclass, in accordance with the earlier
results of the authors, is distributed non-randomly. Concerning the short
subclass earlier statistical tests also suggested some departure from the
random distribution, but not on a high enough confidence level. The new tests
presented in this article suggest also non-randomness here.Comment: in GAMMA-RAY BURSTS 2007: Proceedings of the Santa Fe Conferenc
Gamma kitörések statisztikus vizsgálata = Statistical investigation of Gamma ray Bursts
Égi eloszlás Több statisztikai módszerrel is elsőként igazoltuk a közepes és rövid gamma kitörések anizotrop eloszlását az égen. 13 új sztochasztikus változót definiáltunk a Voronoi felbontás, minimális kifeszítő fa és a multifraktál spektrum segítségével. Ezeket a változókat 8 korrelálatlan háttérváltozóba sűrítettük. 99%-nál nagyobb szignifikanciával igazoltuk, hogy a rövid kitörések nem véletlenül oszlanak el az égen (közepesekre ez 98.5%). Korai csillagkeletkezési folyamatok A hosszú kitörésekre a vöröseltolódásbeli eloszlás összhangban van a csillagkeletkezési gyakorisággal. A Swift mesterséges hold újabb, az eddig észlelteknél halványabb kitöréseket fedezett fel. Csoportunk összehasonlította a Swift által kapott vöröseltolódásokat más megfigyelésekből szerzettekkel, és a kettő szignifikánsan különbözőnek bizonyult. Sötét kitörések A többváltozós statisztika diszkriminacia analízisével összehasonítottuk az optikailag fényes, ill. sötét kitöréseket. A Swift műhold megfigyeléseiből felhasznált 7 változóból kettő mutatott szignifikáns eltérést. Az optikai tranziens produkáló kitörések nagyobb csúcsfényességgel rendelkeztek, és a hidrogén oszlopsűrűség átlagban alacsonyabb volt. Osztályozás A CGRO BATSE adatok részletes statisztikus vizsgálatával igazoltuk a harmadik közepes hosszúságú alosztály létezését. További figyelemreméltó új eredmény itt az erős antikorreláció az időtartam és a spektrumkeménység között. | Angular distribution Using several statistical methods we have first proven that the sky distributions of both short and intermediate gamma-ray bursts are anisotropic. We have defined 13 new stochastic variables based on Voronoi tessellation, minimal spanning tree and multifractal spectrum. These variables were joined into 8 non-correlated background variables. We have shown with a higher than 99% probability that the short bursts are not distributed randomly on the sky (for intermediates 98.5%). Early star-formation The redshift distribution of long bursts fits that of the star-formation rate. The Swift satellite discovered newer and fainter bursts than earlier detected. Our group has compared the redshifts obtained by Swift and by other observations and found them to be significantly different. Dark bursts Using the multivariate discriminant statistical analysis we compared the optically bright dark and bursts. From the seven variables used in the observations of the Swift satellite two have shown significant differences. The bursts producing optical transients have higher peakflux and on average their column densities are lower. Classification of the bursts Using a detailed statistical analysis of the CGRO BATSE data we have proven the existence of a third subgroup having an intermediate duration. A further remarkable new result here is the strong anti-correlation between the duration and the spectral hardness
Low thrombin generation predicts poor prognosis in ischemic stroke patients after thrombolysis.
Thrombolysis by intravenous recombinant tissue plasminogen activator (rt-PA) is an effective therapy in acute ischemic stroke (AIS). Thrombin generation test (TGT) is a global hemostasis test providing information about the speed and amount of generated thrombin in plasma. Here we aimed to find out whether results of this test before the initiation of thrombolysis might predict outcomes. Study population included 120 consecutive AIS patients, all within 4.5 hours of their symptom onset, who underwent thrombolysis by rt-PA. Blood samples were collected from all patients upon admission and TGT was performed using platelet poor plasma. Clinical data of patients including the NIHSS were registered at admission, day 1 and 7 after therapy. The ASPECT score was assessed using CT images taken before and 24 hours after thrombolysis. Long-term functional outcome was defined 3 months after the event by the modified Rankin Scale. Endogenous Thrombin Potential (ETP) and Peak Thrombin were significantly lower in patients with cardioembolic IS. Symptomatic intracranial hemorrhage (SICH) was found in 6 patients and was significantly associated with low ETP and Peak Thrombin levels. A multiple logistic regression model revealed that an ETP result in the lower quartile is an independent predictor of mortality within the first two weeks (OR: 6.03; 95%CI: 1.2-30.16, p<0.05) and three months after the event (OR: 5.28; 95%CI: 1.27-21.86, p<0.05). Low levels of ETP and Peak Thrombin parameters increase the risk of therapy associated SICH. A low ETP result is an independent predictor of short- and long-term mortality following thrombolysis
Low factor XIII levels after intravenous thrombolysis predict short-term mortality in ischemic stroke patients
L
Intracardiac Fibrinolysis and Endothelium Activation Related to Atrial Fibrillation Ablation with Different Techniques
L
PAI-1 5G/5G genotype is an independent risk of intracranial hemorrhage in post-lysis stroke patients
K