On the formation history of Galactic double neutron stars

Double neutron stars (DNSs) have been observed as Galactic radio pulsars, and the recent discovery of gravitational waves from the DN merger GW170817 adds to the known DNS population. We perform rapi population synthesis of massive binary stars and discuss mode predictions, including DNS formation rates, mass distributions, an delay time distributions. We vary assumptions and parameters of physica processes such as mass transfer stability criteria, supernova natal kic distributions, remnant mass prescriptions, and common-envelop eccentricity distribution of the Galactic DNS population under each o our population synthesis models, allowing us to quantitatively compar burning secondary (case BB) on to a neutron star is most likel dynamically stable. We also find that a natal kick distribution compose of both low (Maxwellian σ =30 km s^{-1}) and high (σ =265 km s^{-1} components is preferred over a single high-kick component. We conclud that the observed DNS mass distribution can place strong constraints o model assumption

Agmatine, a metabolite of L-arginine, reverses scopolamine-induced learning and memory impairment in rats

Agmatine (1-amino-4-guanidino-butane), a metabolite of L-arginine through the action of arginine decarboxylase, is a novel neurotransmitter. In the present study, effects of agmatine on cognitive functions have been evaluated by using one trial step-down passive avoidance and three panel runway task. Agmatine (20, 40, 80 mg/kg i.p.) was administered either in the presence or absence of a cholinergic antagonist, scopolamine (1 mg/kg i.p.). Scopolamine significantly impaired learning and memory in both passive avoidance and three panel runway test. Agmatine did not affect emotional learning, working and reference memory but significantly improved scopolamine-induced impairment of learning and memory in a dose dependent manner. Our results indicate that agmatine, as an endogenous substance, may have an important role in modulation of learning and memory functions. (c) 2012 Elsevier Inc. All rights reserved.Research Foundation of Kocaeli UniversityKocaeli University [200439]The present study was supported by the Research Foundation of Kocaeli University (200439) and presented at Society of Biological Psychiatry's 65th Annual Meeting, New Orleans, Louisiana, 20-22 May, 2010

Effects of Holding Time on Thermomechanical Fatigue Properties of Compacted Graphite Iron Through Tests with Notched Specimens

In cylinder heads of compacted graphite iron (CGI), the heating and cooling cycles can lead to localized cracking due to thermomechanical fatigue (TMF). Traditionally, TMF behavior is studied by thermal cycling of smooth specimens. The resulting number of cycles to failure (Nf) constitutes a single parameter that can be used to predict actual service failures. Nevertheless, there are also some drawbacks of the conventional testing procedures, most noticeably the prolonged testing times and a considerable scatter in test results. To address these drawbacks, TMF tests were performed using notched specimens, resulting in shorter testing times with less scatter. In the case of cast iron, artificial notches do not necessarily change the TMF behavior since the inherent graphite particles behave as internal notches. Using a notch depth of 0.2 mm, the effect of prolonged holding times (HT) on TMF lifetime was studied and a clear effect was found. Extended holding times were also found to be accompanied by relaxation of compressive stresses, causing higher tensile stresses to develop in the subsequent low temperature stages of the TMF cycles. The lifetimes in notched CGI specimens can be predicted by the Paris’ fatigue crack growth model. This model was used to differentiate between the individual effects of stress level and holding times on TMF lifetime. Microstructural changes were evaluated by analyzing quantitative data sets obtained by orientation contrast microscopy based on electron backscattered diffraction (EBSD).Materials Innovation InstituteMechanical, Maritime and Materials Engineerin