Experimental Evidence of Large Collective Enhancement of Nuclear Level Density and its Significance in Radiative Neutron Capture

The collective enhancement of nuclear level density and its fade out with excitation energy in deformed $^{171}$Yb nucleus has been inferred through an exclusive measurement of neutron spectra.The statistical model analysis of neutron spectra demonstrated a large collective enhancement factor of 40$\pm$3 for the first time, which corroborates with the recent microscopic model predictions but is an anomalous result compared with the measurements in the nearby deformed nuclei. The complete picture of the energy dependent collective enhancement has been obtained by combining with Oslo data below neutron binding energy. The significance of large collective enhancement in radiative neutron capture cross section of astrophysical interest is highlighted.Comment: 12 pages, 5 figure

Evidence of a new shell closed nucleus governing slow quasi-fission

Mass distributions of fission fragments arising from the slow quasi-fission process have been derived by comparing the measured distributions with the theoretical distributions based on compound nuclear fission model for several reactions. The mass-distributions corresponding to quasi-fission events for all the systems show the following common features: (1) they are double peaked with fixed peak-centroids and nearly same width at different incident energies, (2) the yield of quasi-fission events decreases with the increasing projectile energy, and (3) peak corresponding to lighter fragment is observed at A $\sim$ 96 for all the systems, whereas the peak of heavier fragment increases linearly with the mass of the di-nuclear system. All the above observations are quite similar to the ones observed in well known asymmetric fission of actinides, thus providing clear evidences of shell effect in slow quasi-fission where the lighter fragment is possibly nuclei around $^{96}$Zr, a new doubly magic nucleus. This finding has great implications in the study of nuclear reactions, structure and particularly in super-heavy element synthesis where quasi-fission is synonymous

Cerebral Venous Thrombosis in COVID-19: A New York Metropolitan Cohort Study

BACKGROUND AND PURPOSE: Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infection is associated with hypercoagulability. We sought to evaluate the demographic and clinical characteristics of cerebral venous thrombosis among patients hospitalized for coronavirus disease 2019 (COVID-19) at 6 tertiary care centers in the New York City metropolitan area. MATERIALS AND METHODS: We conducted a retrospective multicenter cohort study of 13,500 consecutive patients with COVID-19 who were hospitalized between March 1 and May 30, 2020. RESULTS: Of 13,500 patients with COVID-19, twelve had imaging-proved cerebral venous thrombosis with an incidence of 8.8 per 10,000 during 3 months, which is considerably higher than the reported incidence of cerebral venous thrombosis in the general population of 5 per million annually. There was a male preponderance (8 men, 4 women) and an average age of 49 years (95% CI, 36-62 years; range, 17-95 years). Only 1 patient (8%) had a history of thromboembolic disease. Neurologic symptoms secondary to cerebral venous thrombosis occurred within 24 hours of the onset of the respiratory and constitutional symptoms in 58% of cases, and 75% had venous infarction, hemorrhage, or both on brain imaging. Management consisted of anticoagulation, endovascular thrombectomy, and surgical hematoma evacuation. The mortality rate was 25%. CONCLUSIONS: Early evidence suggests a higher-than-expected frequency of cerebral venous thrombosis among patients hospitalized for COVID-19. Cerebral venous thrombosis should be included in the differential diagnosis of neurologic syndromes associated with SARS-CoV-2 infection

Time to Wake-Up: Extending the Window for Management of Unknown-Onset Strokes

The term Wake-Up Stroke is applied to a patient who displays no symptoms before sleep, but wakes with neurologic deficits suggestive of stroke. The current guidelines for acute ischemic stroke limit intravenous tissue plasminogen activator use to stroke patients in whom symptom onset or last known well is less than 4.5 hours. Approximately one-third of acute ischemic stroke patients present with unknown time of symptom onset and are often not eligible for intravenous reperfusion therapy in clinical practice. This review provides an overview of several earlier trials that used advanced neuroimaging to determine eligibility for reperfusion therapy in patients with unknown stroke onset. The reassuring results of these earlier trials that led to recent thrombolysis trials specifically targeted at wake-up stroke patients are discussed in this review. Ongoing studies aim to expand our knowledge regarding the safety and efficacy of thrombolysis in these patients

Decision-Making for Patients With Cerebral Arteriovenous Malformations

Cerebral arteriovenous malformations (AVMs) are a complex and heterogeneous pathology which require an understanding of the natural history of these lesions, as well as the potential treatment options in order to manage them safely. While treatment is the agreed upon strategy for most ruptured AVMs, the management of unruptured AVMs continues to be debated. More recently, this debate has been fueled by the A Randomized Trial of Unruptured Arteriovenous Malformations (ARUBA) trial which attempts to define the natural history and treatment risk of AVMs. However, the trial has significant shortcomings which limit its broad applicability. In addition, the breadth, efficacy, and safety of potential treatment options continue to improve. This review focuses on defining the natural history of cerebral AVMs, an overview of the ARUBA trial, and the most current treatment paradigm for cerebral AVMs

Measurement of

The cross sections for $$^{58}$$Co(n,xp) reactions have been determined in the equivalent neutron energy range of 11.7–16.8 MeV by employing the surrogate reaction ratio method and using the cross-section values for the reference reaction $$^{60}$$Ni(n,xp) from the literature. The transfer reactions $$^{57}$$Fe($$^6$$Li,$$\alpha$$) at $$E_\textrm{lab}$$ = 37 MeV and $$^{59}$$Co($$^6$$Li,$$\alpha$$) at $$E_\textrm{lab}$$ = 33 MeV, are used to populate compound nuclei $$^{59}$$Co$$^*$$ (surrogate of n+$$^{58}$$Co) and $$^{61}$$Ni$$^*$$ (surrogate of n+$$^{60}$$Ni), respectively, at similar excitation energies. The evaporated protons at backward angles measured in coincidence with the projectile-like fragment alpha provide the proton decay probabilities of the compound nuclei. The cross sections estimated using the nuclear-reactions-model code taly

Management of Small Unruptured Intracranial Aneurysms: To Treat or Not to Treat?

Unruptured intracranial aneurysms measuringliterature, the 3 main treatments for an unruptured intracranial aneurysm are conservative management with follow-up imaging, endovascular coiling, or surgical clipping. However, there remains no consensus on the best treatment approach. The natural history of the aneurysm and risk factors for aneurysm rupture must be considered to individualize treatment. Models including population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from a prior aneurysm, site of aneurysm score, Unruptured Intracranial Aneurysm Treatment Score, and advanced neuroimaging can assist physicians in assessing the risk of aneurysm rupture. Macrophages and other inflammatory modulators have been elucidated as playing a role in intracranial aneurysm progression and eventual rupture. Further studies need to be conducted to explore the effects of therapeutic drugs targeting inflammatory modulators

Cerebral Venous Sinus Thrombosis in COVID-19 Infection: A Case Series and Review of The Literature

SARS-CoV-2, the virus responsible for novel Coronavirus (COVID-19) infection, has recently been associated with a myriad of hematologic derangements; in particular, an unusually high incidence of venous thromboembolism has been reported in patients with COVID-19 infection. It is postulated that either the cytokine storm induced by the viral infection or endothelial damage caused by viral binding to the ACE-2 receptor may activate a cascade leading to a hypercoaguable state. Although pulmonary embolism and deep venous thrombosis have been well described in patients with COVID-19 infection, there is a paucity of literature on cerebral venous sinus thrombosis (cVST) associated with COVID-19 infection. cVST is an uncommon etiology of stroke and has a higher occurrence in women and young people. We report a series of three patients at our institution with confirmed COVID-19 infection and venous sinus thrombosis, two of whom were male and one female. These cases fall outside the typical demographic of patients with cVST, potentially attributable to COVID-19 induced hypercoaguability. This illustrates the importance of maintaining a high index of suspicion for cVST in patients with COVID-19 infection, particularly those with unexplained cerebral hemorrhage, or infarcts with an atypical pattern for arterial occlusive disease

Endovascular Thrombectomy for Treatment of Acute Ischemic Stroke During Pregnancy and the Early Postpartum Period

BACKGROUND AND PURPOSE: Acute ischemic stroke (AIS) is a rare occurrence during pregnancy and the postpartum period. Existing literature evaluating endovascular mechanical thrombectomy (MT) for this patient population is limited. METHODS: The National Inpatient Sample was queried from 2012 to 2018 to identify and characterize pregnant and postpartum patients (up to 6 weeks following childbirth) with AIS treated with MT. Complications and outcomes were compared with nonpregnant female patients treated with MT and to other pregnant and postpartum patients managed medically. Complex samples regression models and propensity score matching were implemented to assess adjusted associations and to address confounding by indication, respectively. RESULTS: Among 4590 pregnant and postpartum patients with AIS, 180 (3.9%) were treated with MT, and rates of utilization increased following the MT clinical trial era (2015-2018; 1.9% versus 5.3%, CONCLUSIONS: This large-scale analysis utilizing national claims data suggests that MT is a safe and efficacious therapy for AIS during pregnancy and the postpartum period. In the absence of prospective clinical trials, population-based cross-sectional analyses such as the present study provide valuable clinical insight

Acute Cerebrovascular Disorders and Vasculopathies Associated with Significant Mortality in SARS-CoV-2 Patients Admitted to The Intensive Care Unit in The New York Epicenter

The current Coronavirus pandemic due to the novel SARS-Cov-2 virus has proven to have systemic and multi-organ involvement with high acuity neurological conditions including acute ischemic strokes. We present a case series of consecutive COVID-19 patients with cerebrovascular disease treated at our institution including 3 cases of cerebral artery dissection including subarachnoid hemorrhage. Knowledge of the varied presentations including dissections will help treating clinicians at the bedside monitor and manage these complications preemptively