Search

The quark–gluon plasma (QGP) produced by collisions between ultrarelativistic heavy nuclei is well described in the language of hydrodynamics. Noncentral collisions are characterized by very large angular momentum, which in a fluid system manifests as flow vorticity. This rotational structure can lead to a spin polarization of the hadrons that eventually emerge from the plasma, and thus these collisions provide experimental access to flow substructure at unprecedented detail. Recently, the first observations of Λ hyperon polarization along the direction of collisional angular momentum were reported. These measurements are in broad agreement with hydrodynamic and transport-based calculations and reveal that the QGP is the most vortical fluid ever observed. However, there remain important tensions between theory and observation that might be fundamental in nature. In the relatively mature field of heavy-ion physics, the discovery of global hyperon polarization and 3D simulations of the collision have opened an entirely new direction of research. We discuss the current status of this rapidly developing area and directions for future research. [ABSTRACT FROM AUTHOR]

Recently, the global polarization of Λ and Λ – hyperons in heavy-ion collisions (HIC) has been observed [1] by the STAR Collaboration at the Relativistic Heavy Ion Collider (RHIC) in Brookhaven National Laboratory (BNL). The discovery confirms the theoretical prediction [2] made more than 10 years ago and indicates that the quark gluon plasma (QGP) produced in HIC possesses a vorticity as high as 1021s−1, much higher than any other fluid observed in nature. This opens a new window to study properties of QGP and a new direction in high energy heavy ion physics. [ABSTRACT FROM AUTHOR]

Moyamoya vasculopathy is a progressive, occlusive vasculopathy leading to ischemic and hemorrhagic strokes. No treatments are established to treat acute ischemic stroke with moyamoya vasculopathy. A 3-year-old girl with moyamoya syndrome developed acute left hemiplegia. Emergent angiography showed near-occlusion of the supraclinoid segment of the right internal carotid artery. Balloon angioplasty was performed within 6 hours of symptom onset, with significant improvement in the child’s neurological symptoms. This is the youngest case of intracranial balloon angioplasty, and this article discusses the paucity of data regarding angioplasty and other forms of endovascular intervention in pediatric cerebrovascular disease and moyamoya vasculopathy. Further study is needed to determine the safety and efficacy of endovascular intervention in these diseases. [ABSTRACT FROM PUBLISHER]

Acute chemotherapy-related leukoencephalopathy can present similar to acute stroke with symptoms including aphasia, dysarthria, and hemiplegia. Differentiation based on clinical appearance is challenging, and physicians must distinguish between the 2 conditions rapidly to institute appropriate therapies. An 8-year-old male with acute lymphoblastic leukemia receiving chemotherapy, including intrathecal methotrexate, presented to our emergency center with 2 hours of expressive aphasia and flaccid right hemiplegia. Emergent magnetic resonance imaging (MRI) was obtained, demonstrating diffusion restriction within bilateral corona radiata and centrum semiovale. Magnetic resonance perfusion revealed mildly increased perfusion, a finding inconsistent with ischemic stroke and previously unreported in acute chemotherapy-related leukoencephalopathy without necrosis. This increased perfusion conclusively eliminated stroke from the clinical differential. Magnetic resonance perfusion imaging proved valuable to rapidly distinguish acute chemotherapy-related leukoencephalopathy from ischemia, and the evaluation of perfusion alterations in this disorder may provide further insight into the pathophysiology of this entity. [ABSTRACT FROM AUTHOR]

Analyses of two-particle correlations have provided the chief means for determining spatio-temporal characteristics of relativistic heavy ion collisions. We discuss the theoretical formalism behind these studies and the experimental methods used in carrying them out. Recent results from RHIC are put into context in a systematic review of correlation measurements performed over the past two decades. The current understanding of these results is discussed in terms of model comparisons and overall trends. [ABSTRACT FROM AUTHOR]

The system created in ultrarelativistic nuclear collisions is known to behave as an almost ideal liquid. In noncentral collisions, because of the large orbital momentum, such a system might be the fluid with the highest vorticity ever created under laboratory conditions. Particles emerging from such a highly vorticous fluid are expected to be globally polarized with their spins on average pointing along the system angular momentum. Vorticity-induced polarization is the same for particles and antiparticles, but the intense magnetic field generated in these collisions may lead to the splitting in polarization. In this paper we outline the thermal approach to the calculation of the global polarization phenomenon for particles with spin and we discuss the details of the experimental study of this phenomenon, estimating the effect of feed-down. A general formula is derived for the polarization transfer in two-body decays and, particularly, for strong and electromagnetic decays. We find that accounting for such effects is crucial when extracting vorticity and magnetic field from the experimental data. [ABSTRACT FROM AUTHOR]

Objective: Malignant middle cerebral artery infarction (mMCAI) is a life-threatening condition in pediatric patients. Despite strong evidence showing decreased morbidity and mortality in adult mMCAI patients with decompressive hemicraniectomy (DCH), there is a paucity of data on the use of DCH in children with similar conditions. Here we report experience from our center and perform a systematic review of published literature on outcomes after use of DCH in pediatric mMCAI patients. Methods: By retrospective chart review, we identified 3 children with large ischemic stroke who underwent DCH for life-threatening cerebral edema. Information was obtained about patient characteristics on admission, radiological features of the stroke, surgical procedures, complications of the DCH and cranioplasty, and functional outcomes during follow-up visits. We also reviewed the current literature on DCH in pediatric stroke. Results: DCH was performed in all 3 cases after development of pupillary dilatation. All 3 children survived and were ambulatory at the time of follow-up. Review of literature identified 12 other published case series describing 26 cases of DCH in pediatric patients with ischemic stroke. Descriptive statistical analysis of these cases is presented. Published reports suggest that a good outcome is possible even in the presence of signs of herniation, low preoperative Glasgow Coma Scale score, involvement of multiple vascular territories, or longer time to surgery in pediatric ischemic stroke patients. Conclusions: The current data suggest a role for DCH in the management of cerebral edema in pediatric patients with mMCAI. Factors that help in prognostication for adult stroke patients undergoing DCH do not appear to convey similar information about the pediatric population. This highlights the urgent need for collaboration across institutes to further investigate this potentially life-saving procedure in pediatric stroke. [ABSTRACT FROM AUTHOR]

We examine the formation of vortical "smoke rings" as a result of thermalization of energy lost by a jet. We simulate the formation and evolution of these rings using hydrodynamics and define an observable that allows to probe this phenomenon experimentally. We argue that observation of vorticity associated with jets would be an experimental confirmation of the thermalization of the energy lost by quenched jets, and also a probe of shear viscosity. [ABSTRACT FROM AUTHOR]