20,886 research outputs found
Charges on Strange Quark Nuggets in Space
Since Witten's seminal 1984 paper on the subject, searches for evidence of
strange quark nuggets (SQNs) have proven unsuccessful. In the absence of
experimental evidence ruling out SQNs, the validity of theories introducing
mechanisms that increase their stability should continue to be tested. To
stimulate electromagnetic SQN searches, particularly space searches, we
estimate the net charge that would develop on an SQN in space exposed to
various radiation baths (and showers) capable of liberating their less strongly
bound electrons, taking into account recombination with ambient electrons. We
consider, in particular, the cosmic background radiation, radiation from the
sun, and diffuse galactic and extragalactic -ray backgrounds. A
possible dramatic signal of SQNs in explosive astrophysical events is noted.Comment: CitationS added, new subsection added, more discussion, same
numerical result
Distributed Cognition and the Task of Science
This paper gives a characterization of distributed cognition (d-cog) and explores ways that the framework might be applied in studies of science. I argue that a system can only be given a d-cog description if it is thought of as performing a task. Turning our attention to science, we can try to give a global d-cog account of science or local d-cog accounts of particular scientific projects. Several accounts of science can be seen as global d-cog accounts: Robert Merton\u27s sociology of scientific norms, Philip Kitcher\u27s 20th-century account of cognitive labor, and Kitcher\u27s 21st-century notion of well-ordered science. Problems that arise for them arise just because of the way that they attribute a function to science. The paper concludes by considering local d-cog accounts. Here, too, the task is the crux of the matter
Framing-effects approach: A theoretical and methodological critique
The article deals with research on framing effects. First, I will start with classifying different approaches on framing. Subsequently, I will provide a definition of the concepts of frame, schema and framing, expand on framing research conducted so far - both theoretically and operationally. Having this equipment at hand, I will initiate a discussion on studies of framing-effects in terms of theory, methods and empirical results. This discussion leads to the conclusion that studies on framing effects are insufficiently concerned with the more recent psychological constructs and theories. In merely focusing on the activation of schemata, most studies ignore the more elaborate types of framing-effects. Therefore, several empirical questions remain unanswered and some methodical chances seem to be wasted
Attenuation of choroidal tickness in patients with Alzheimer disease: evidence from an Italian prospective study
INTRODUCTION: To compare the 12-month choroidal thickness (CT) change between
Alzheimer disease (AD) patients and normal subjects.
METHODS: In this prospective, observational study, 39 patients with a diagnosis
of mild to moderate AD and 39 age-matched control subjects were included. All the
subjects underwent neuropsychological (Mini Mental State Examination, Alzheimer
disease Assessment Scale-Cognitive Subscale, and the Clinical Dementia Rating
Scale) and ophthalmological evaluation, including spectral domain optical
coherence tomography, at baseline and after 12 months. CT was measured manually
using the caliper tool of the optical coherence tomography device.
RESULTS: After 12 months, AD patients had a greater reduction of CT than controls
(P≤0.05, adjusted for baseline CT, age, sex, axial length, and smoking).
DISCUSSION: CT in patients with AD showed a rate of thinning greater than what
could be expected during the natural course of aging
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