5,118 research outputs found
Rogue decoherence in the formation of a macroscopic atom-molecule superposition
We theoretically examine two-color photoassociation of a Bose-Einstein
condensate, focusing on the role of rogue decoherence in the formation of
macroscopic atom-molecule superpositions. Rogue dissociation occurs when two
zero-momentum condensate atoms are photoassociated into a molecule, which then
dissociates into a pair of atoms of equal-and-opposite momentum, instead of
dissociating back to the zero-momentum condensate. As a source of decoherence
that may damp quantum correlations in the condensates, rogue dissociation is an
obstacle to the formation of a macroscopic atom-molecule superposition. We
study rogue decoherence in a setup which, without decoherence, yields a
macroscopic atom-molecule superposition, and find that the most favorable
conditions for said superposition are a density ~ 1e12 atoms per cc and
temperature ~ 1e-10.Comment: 10 pages, 4 figures, 46+ references; submitted to PR
Intercultural Challenges in Networked Learning
This paper gives an account of themes that emerged from a preliminary analysis of a large corpus of electronic communications in an online, mediated course for intercultural learners. The goals were to test assumptions that electronic communication is internationally standardized, to identify any problematic aspects of such communications, and to construct a framework for the analysis of electronic communications using constructs from intercultural communications theory. We found that cyberspace itself has a culture(s), and is not culture-free. Cultural gaps can exist between individuals, as well as between individuals and the dominant cyberculture, increasing the chances of miscommunication. The lack of elements inherent in face-to-face communication further problematizes intercultural communications online by limiting opportunities to give and save face, and to intuit meaning from non-verbal cues. We conclude that electronic communication across cultures presents distinctive challenges, as well as opportunities to course planners
Negotiating cultures in cyberspace
In this paper we report findings of a multidisciplinary study of online participation by culturally diverse participants in a distance adult education course offered in Canada and examine in detail three of the study's findings. First, we explore both the historical and cultural origins of "cyberculture values" as manifested in our findings, using the notions of explicit and implicit enforcement of those values and challenging the assumption that cyberspace is a culture free zone. Second, we examine the notion of cultural gaps between participants in the course and the
potential consequences for online communication successes and difficulties. Third, the analysis describes variations in participation frequency as a function of broad cultural groupings in our data. We identify the need for additional research, primarily in the form of larger scale comparisons across cultural groups of patterns of participation and interaction, but also in the form of case studies that can be submitted to microanalyses of the form as well as the content of communicator's participation and interaction online
Sellafield-derived anthropogenic C-14 in the marine intertidal environment of the NE Irish Sea
The intertidal biota from Parton beach, close to the Sellafield nuclear fuel reprocessing plant, were all found to be enriched in radiocarbon relative to ambient background. The degree of enrichment appears to reflect the positions of the biota in the food chain once the dilution in seaweed from atmospheric uptake is taken into account. Close to the low-water mark, the order was mussels gt limpets gt anemones congruent to winkles gt seaweed. The same order was observed close to the high-water mark, except that anemones were absent from this area. The activities in the biogeochemical fractions of the water column reflect the fact that discharges are primarily in the form of dissolved inorganic carbon (DIC), which is subsequently transferred to the particulate organic carbon (POC) and, to a lesser extent, the dissolved organic carbon (DOC), and finally, the particulate inorganic carbon (PIC). Analysis of intertidal sediment suggests that there is likely to be a gradual increase in the specific activity of C-14 in the inorganic component of this material as Sellafield contaminated organisms die and their shells are ground down by natural processes
Self-administration of edible Δ9-tetrahydrocannabinol and associated behavioral effects in mice
Background
With increasing access to legal cannabis across the globe, it is imperative to more closely study its behavioral and physiological effects. Furthermore, with the proliferation of cannabis use, modes of consumption are changing, with edible formulations becoming increasingly popular. Nevertheless, there are relatively few animal models of self-administration of the primary psychoactive component of cannabis, Δ9-tetrahydrocannabinol (THC), and almost all incorporate routes of administration other than those used by humans. The aim of the current study was to develop a model of edible THC self-administration and assess its impact on CB1 receptor-mediated behaviors in female and male mice.
Methods
Mice were given limited access to a palatable dough which occasionally contained THC in doses ranging from 1 to 10 mg/kg. Following dough consumption, mice were assessed for home cage locomotor activity, body temperature, or analgesia. Locomotor activity was also assessed in conjunction with the CB1 receptor antagonist SR141716A.
Results
Dough was well-consumed, but consumption decreased at the highest THC concentrations. Edible THC produced dose-dependent decreases in locomotor activity and body temperature in both sexes, and these effects were more pronounced in male mice. Hypolocomotion induced by edible THC was attenuated by SR141716A, indicating mediation by CB1 receptor activation.
Conclusions
In contrast to other cannabinoid self-administration models, edible THC is relatively low in stress and uses a route of administration analogous to one used by humans. Potential applications include chronic THC self-administration, determining THC reward/reinforcement, and investigating consequences of oral THC use
Patients with Essential thrombocythaemia have an increased prevalence of antiphospholipid antibodies which may be associated with thrombosis
A significant proportion of patients with Essential Thrombocythaemia (ET) have thrombotic complications which have an important impact upon the quality, and duration of their life. We performed a retrospective cross sectional study of the prevalence of antiphospholipid antibodies (APA) in 68 ET patients. Compared to 200 elderly controls (> 50 years) there was a significant increase in anticardiolipin IgM (p < 0.0001) and anti β2 glycoprotein I (anti-β2GPI) IgM (p < 0.0001) antibodies in ET. Thrombosis occurred in 10/20 with APA and 12/48 without, p = 0.04, relative risk 2.0 (95% confidence intervals 1.03-3.86); these patients did not differ in terms of other clinical features. The prevalence of thrombosis in patients with dual APA (6/7) was significant when compared to those with single APA (p = 0.02) and the remaining patients (p < 0.0002). Also anti-β2GPI IgM antibodies either alone, or in combination with another APA, were associated with thrombosis (p = 0.02). These results suggest that the prevalence of APA in ET and their influence upon thrombotic risk merit investigation in a larger study
Falling through the (cultural) gaps?
In this paper we report findings of a study of online participation by culturally diverse participants in a distance adult education course offered in Canada, and examine two of the study’s early findings. First, we explore both the historical and cultural origins of “cyberculture values” as manifested in our findings, using the notions of explicit and implicit enforcement of those values. Second, we examine the notion of “cultural gaps” between participants in the course and the potential consequences for online communication successes and difficulties. We also discuss theoretical perspectives from Sociolinguistics, Applied Linguistics, Genre and Literacy Theory and Aboriginal Education that may shed further light on “cultural gaps” in online communications. Finally, we identify the need for additional research, primarily in the form of larger scale comparisons across cultural groups of patterns of participation and interaction, but also in the form of case studies that can be submitted to microanalyses of the form as well as the content of communicator’s participation and interaction online
Rate limit for photoassociation of a Bose-Einstein condensate
We simulate numerically the photodissociation of molecules into noncondensate
atom pairs that accompanies photoassociation of an atomic Bose-Einstein
condensate into a molecular condensate. Such rogue photodissociation sets a
limit on the achievable rate of photoassociation. Given the atom density \rho
and mass m, the limit is approximately 6\hbar\rho^{2/3}/m. At low temperatures
this is a more stringent restriction than the unitary limit of scattering
theory.Comment: 5 pgs, 18 refs., 3 figs., submitted to Phys. Rev. Let
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