Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Semantic relations and repetition of items enhance the free recall of words by multiple sclerosis patients

We compared 25 patients with multiple sclerosis (MS) and 24 normal controls on a test of free recall of words. Some lists contained words that were all unrelated, while in others the intermediary words were semantically related. in another set, the mid-list words were repeated across the lists, or, in addition to the repetition, were semantically associated. Immediate recall was assessed using these lists. Delayed recall was assessed using different lists (delay-unrelated and delay-related) after distractor tasks. Recency was not affected in MS patients, but the primacy effect was lower than in controls, this effect being interpreted as due to a deficiency in articulatory rehearsal. the delay interval after each list abolished recency in both groups and resulted in impaired recall in MS patients. However the patients, like the controls, benefited from semantic relations in the middle of the lists and from spaced repetition of words across the lists, in either immediate and delayed recall. the enhancing effects of word relatedness and of spaced repetition are seen as being due to automatic processes preserved in MS patients.Universidade Federal de São Paulo, Dept Psychobiol, Escola Paulista Med, BR-04024002 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Escola Paulista Med, BR-04024002 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, Escola Paulista Med, BR-04024002 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Escola Paulista Med, BR-04024002 São Paulo, BrazilWeb of Scienc