Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation1,2. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid1–3. A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation1. NASA’s Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission’s target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft4. Although past missions have utilized impactors to investigate the properties of small bodies5,6, those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft’s autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary.
Fissell WH, Hofmann CL, Smith R, Chen MH. Size and conformation of Ficoll as determined by size-exclusion chromatography followed by multiangle light scattering.
Introduction Cognitive impairment is prevalent and debilitating among persons with multiple sclerosis (MS). While many pharmacologic treatments have shown good efficacy in reducing clinical relapses, brain lesions, and improving certain physical symptoms, their efficacy for improving cognitive function is not well understood. Objectives The current systematic review aimed to evaluate the efficacy of pharmacologic treatments for improving cognitive function among persons with MS. Methods A literature search was conducted through the PubMed and PsycINFO databases. Two independent reviewers assessed each paper, and a third reviewer weighed in if the two reviewers could not reach a consensus. Classification of evidence was determined using the 2017 American Academy of Neurology (AAN) criteria for therapeutic trials. Standardized effect sizes (Cohen's d) were calculated to compare across studies. Results Eighty-seven journal articles published between 1990 and January 2020 were included in the current review. Overall, there is insufficient evidence to support the use of pharmacologic treatments to improve cognitive function in persons with MS. There were many contradictory findings observed in this review, which may be due to possible unidentified moderating treatment response variables and/or lack of standardization in assessment procedures. There was also an overreliance on statistical significance (most papers did not provide sizes of treatment effects), which may not be clinically meaningful. Conclusions Higher-quality randomized controlled trials are needed to establish the cognitive efficacy of pharmacologic treatments for MS-related cognitive dysfunction, with cognition as the primary endpoint. Researchers are urged to use standardized criteria (such as the AAN criteria) to guide their research designs. Clinicians should consider effect sizes of studies before deciding whether to prescribe certain medications to ameliorate cognitive symptoms.
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