643 research outputs found
Alternator and voltage regulator-exciter for a Brayton cycle space power system. Volume 1 - Design and development
Alternator and voltage regulator for Brayton cycle space power syste
Non-Markovian Momentum Computing: Universal and Efficient
All computation is physically embedded. Reflecting this, a growing body of
results embraces rate equations as the underlying mechanics of thermodynamic
computation and biological information processing. Strictly applying the
implied continuous-time Markov chains, however, excludes a universe of natural
computing. We show that expanding the toolset to continuous-time hidden Markov
chains substantially removes the constraints. The general point is made
concrete by our analyzing two eminently-useful computations that are impossible
to describe with a set of rate equations over the memory states. We design and
analyze a thermodynamically-costless bit flip, providing a first counterexample
to rate-equation modeling. We generalize this to a costless Fredkin gate---a
key operation in reversible computing that is computation universal. Going
beyond rate-equation dynamics is not only possible, but necessary if stochastic
thermodynamics is to become part of the paradigm for physical information
processing.Comment: 6 pages, 3 figures; Supplementary Material, 1 page;
http://csc.ucdavis.edu/~cmg/compmech/pubs/cbdb.ht
Balancing Error and Dissipation in Computing
Modern digital electronics support remarkably reliable computing, especially
given the challenge of controlling nanoscale logical components that interact
in fluctuating environments. However, we demonstrate that the high-reliability
limit is subject to a fundamental error-energy-efficiency tradeoff that arises
from time-symmetric control: Requiring a low probability of error causes energy
consumption to diverge as logarithm of the inverse error rate for nonreciprocal
logical transitions. The reciprocity (self-invertibility) of a computation is a
stricter condition for thermodynamic efficiency than logical reversibility
(invertibility), the latter being the root of Landauer's work bound on erasing
information. Beyond engineered computation, the results identify a generic
error-dissipation tradeoff in steady-state transformations of genetic
information carried out by biological organisms. The lesson is that computation
under time-symmetric control cannot reach, and is often far above, the Landauer
limit. In this way, time-asymmetry becomes a design principle for
thermodynamically efficient computing.Comment: 19 pages, 8 figures; Supplementary material 7 pages, 1 figure;
http://csc.ucdavis.edu/~cmg/compmech/pubs/tsp.ht
Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components
Dry heat sterilization of spacecraft was investigated by studying the production of spore crops, and thermal inactivation of the spores, and bacillus subtillus. Spore assays were made by conventional plate count methods, and survival curves for the spores are presented. The results indicate that the inherent resistance of spores from a parent cell can be maintained
Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components
Experiments performed on the heat resistant organism CK 4-6 are described. Its response to dry heat at two temperatures (125 C and 135 C) at eight humidity levels (0.001 percent to 100 percent RH) in a closed can system is studied
Mitochondrial Impairment in Cerebrovascular Endothelial Cells is Involved in the Correlation between Body Temperature and Stroke Severity
Stroke is the second leading cause of death worldwide. The prognostic influence of body temperature on acute stroke in patients has been recently reported; however, hypothermia has confounded experimental results in animal stroke models. This work aimed to investigate how body temperature could prognose stroke severity as well as reveal a possible mitochondrial mechanism in the association of body temperature and stroke severity. Lipopolysaccharide (LPS) compromises mitochondrial oxidative phosphorylation in cerebrovascular endothelial cells (CVECs) and worsens murine experimental stroke. In this study, we report that LPS (0.1 mg/kg) exacerbates stroke infarction and neurological deficits, in the mean time LPS causes temporary hypothermia in the hyperacute stage during 6 hours post-stroke. Lower body temperature is associated with worse infarction and higher neurological deficit score in the LPS-stroke study. However, warming of the LPS-stroke mice compromises animal survival. Furthermore, a high dose of LPS (2 mg/kg) worsens neurological deficits, but causes persistent severe hypothermia that conceals the LPS exacerbation of stroke infarction. Mitochondrial respiratory chain complex I inhibitor, rotenone, replicates the data profile of the LPS-stroke study. Moreover, we have confirmed that rotenone compromises mitochondrial oxidative phosphorylation in CVECs. Lastly, the pooled data analyses of a large sample size (n=353) demonstrate that stroke mice have lower body temperature compared to sham mice within 6 hours post-surgery; the body temperature is significantly correlated with stroke outcomes; linear regression shows that lower body temperature is significantly associated with higher neurological scores and larger infarct volume. We conclude that post-stroke body temperature predicts stroke severity and mitochondrial impairment in CVECs plays a pivotal role in this hypothermic response. These novel findings suggest that body temperature is prognostic for stroke severity in experimental stroke animal models and may have translational significance for clinical stroke patients - targeting endothelial mitochondria may be a clinically useful approach for stroke therapy
Mind-modelling with corpus stylistics in David Copperfield
We suggest an innovative approach to literary discourse by using corpus linguistic methods to address research questions from cognitive poetics. In this article, we focus on the way that readers engage in mind-modelling in the process of characterisation. The article sets out our cognitive poetic model of characterisation that emphasises the continuity between literary characterisation and real-life human relationships. The model also aims to deal with the modelling of the author’s mind in line with the modelling of the minds of fictional characters. Crucially, our approach to mind-modelling is text-driven. Therefore we are able to employ corpus linguistic techniques systematically to identify textual patterns that function as cues triggering character information. In this article, we explore our understanding of mind-modelling through the characterisation of Mr. Dick from David Copperfield by Charles Dickens. Using the CLiC tool (Corpus Linguistics in Cheshire) developed for the exploration of 19th-century fiction, we investigate the textual traces in non-quotations around this character, in order to draw out the techniques of characterisation other than speech presentation. We show that Mr. Dick is a thematically and authorially significant character in the novel, and we move towards a rigorous account of the reader’s modelling of authorial intention
Behavioral Modernity and the Cultural Transmission of Structured Information: The Semantic Axelrod Model
Cultural transmission models are coming to the fore in explaining increases
in the Paleolithic toolkit richness and diversity. During the later
Paleolithic, technologies increase not only in terms of diversity but also in
their complexity and interdependence. As Mesoudi and O'Brien (2008) have shown,
selection broadly favors social learning of information that is hierarchical
and structured, and multiple studies have demonstrated that teaching within a
social learning environment can increase fitness. We believe that teaching also
provides the scaffolding for transmission of more complex cultural traits.
Here, we introduce an extension of the Axelrod (1997} model of cultural
differentiation in which traits have prerequisite relationships, and where
social learning is dependent upon the ordering of those prerequisites. We
examine the resulting structure of cultural repertoires as learning
environments range from largely unstructured imitation, to structured teaching
of necessary prerequisites, and we find that in combination with individual
learning and innovation, high probabilities of teaching prerequisites leads to
richer cultural repertoires. Our results point to ways in which we can build
more comprehensive explanations of the archaeological record of the Paleolithic
as well as other cases of technological change.Comment: 24 pages, 7 figures. Submitted to "Learning Strategies and Cultural
Evolution during the Paleolithic", edited by Kenichi Aoki and Alex Mesoudi,
and presented at the 79th Annual Meeting of the Society for American
Archaeology, Austin TX. Revised 5/14/1
Long-Term Potentiation: One Kind or Many?
Do neurobiologists aim to discover natural kinds? I address this question in this chapter via a critical analysis of classification practices operative across the 43-year history of research on long-term potentiation (LTP). I argue that this 43-year history supports the idea that the structure of scientific practice surrounding LTP research has remained an obstacle to the discovery of natural kinds
Robot life: simulation and participation in the study of evolution and social behavior.
This paper explores the case of using robots to simulate evolution, in particular the case of Hamilton's Law. The uses of robots raises several questions that this paper seeks to address. The first concerns the role of the robots in biological research: do they simulate something (life, evolution, sociality) or do they participate in something? The second question concerns the physicality of the robots: what difference does embodiment make to the role of the robot in these experiments. Thirdly, how do life, embodiment and social behavior relate in contemporary biology and why is it possible for robots to illuminate this relation? These questions are provoked by a strange similarity that has not been noted before: between the problem of simulation in philosophy of science, and Deleuze's reading of Plato on the relationship of ideas, copies and simulacra
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