2,035 research outputs found
Rasmus Petersen
No full textPostcard of Rasmus Petersen, creator of the Petersen Rock Gardens. | Rasmus Petersen settled on the present site of the rock gardens in 1906. Reclaiming the land for irrigation, took many of his earlier years. In recent years all of his time has been devoted to rock garden construction. The results of his efforts have been enjoyed by thousands of people from all parts of the world.picture postcar
A Divide-and-Conquer Approach for Analysing Overlaid Data Structures
No full textWe present a static program analysis for overlaid data structures such that a node in the structure includes links for multiple data structures and these links are intended to be used at the same time. These overlaid data structures are frequently used in systems code, in order to impose multiple types of indexing structures over the same set of nodes. Our analysis implements two main ideas. The first is to run multiple sub-analyses that track information about non-overlaid data structures, such as lists. The second idea is to control the communication among the sub-analyses using ghost states and ghost instructions. The purpose of this control is to achieve a high level of efficiency by allowing only necessary information to be transferred among sub-analyses and at as few program points as possible. Our analysis has been successfully applied to prove the memory safety of the Linux deadline IO scheduler and AFS server.
Forskere og ingeniør svarer igen:Mindre CO2 og høj forsyningssikkerhed kræver, at vi ser på alle muligheder – også atomkraft
No full textForfatterne bag notatet 'Fakta om atomkraft i Danmark' har taget til genmæle, men vores kritik bliver essentielt set ikke adresseret. Meningen kan ikke være at få en på forhånd udvalgt version af den grønne omstilling til at lykkes, men at se bredt på mulighederne, skriver Hans Uldall Fynbo, Bent Lauritzen, Rasmus Toft-Petersen og Paul-Frederik Bach
Confirmation and Reduction: A Bayesian Account
No full textVarious scientific theories stand in a reductive relation to each other. In a recent article, we have argued that a generalized version of the Nagel-Schaffner model (GNS) is the right account of this relation. In this article, we present a Bayesian analysis of how GNS impacts on confirmation. We formalize the relation between the reducing and the reduced theory before and after the reduction using Bayesian networks, and thereby show that, post-reduction, the two theories are confirmatory of each other. We then ask when a purported reduction should be accepted on epistemic grounds. To do so, we compare the prior and posterior probabilities of the conjunction of both theories before and after the reduction and ask how well each is confirmed by the available evidence
Effect of developmental sensory and motor deprivation on the functional organization of adult rat somatosensory cortex
No full textMost sensory systems are active, in the sense that the animal performs specific motor actions in order to collect information of interest - signals are not merely passively received. We, therefore, expect cortical development to depend not only correct sensory experience, but also on correct motor experience. In this study, we used the rat whisker system as a model to compare the importance of these factors. In one group of animals, we trimmed all whiskers starting from post-natal day 8 (P8). In a second group, we left the whiskers intact, but prevented "whisking" by sectioning the facial (VIIth cranial) nerve on P8. The first group had severely disrupted sensory experience but normal motor patterns ("whisker-cut" rats); the second group had normal sensory pathways within which temporal activity patterns were disrupted by motor impairment ("nerve-cut" rats). When they reached 3 months of age, we recorded multi-unit responses from the infragranular layers of primary somatosensory cortex in response to deflection of either single whiskers or pairs of whiskers in order to compare these two groups to a third group of rats that had normal sensory and motor experience. Cortical topographic organization was unaltered in whisker- and nerve-cut rats. Whisker-cut rats showed a smaller than normal difference between the response magnitudes for the principal and surrounding whiskers, as well as stronger than normal interactions between co-active whisker inputs. Responses in nerve-cut rats were nearly indistinguishable from those in normal animals. Thus, unexpectedly, neither pure sensory nor sensorimotor deprivation caused gross functional disruption of SI according to our measures. It appears that abnormal sensory experience leads to alterations in the fine-tuning of cortical properties, but cortex is unexpectedly resistant to the effects of abnormal sensory and sensorimotor experience. © 2003 Elsevier Science Inc. All rights reserved
Learning through maps: Functional significance of topographic organization in primary sensory cortex
No full textThe presence of 'maps' in sensory cortex is a hallmark of the mammalian nervous system, but the functional significance of topographic organization has been called into question by physiological studies claiming that patterns of neural behavioral activity transcend topographic boundaries. This paper discusses recent behavioral and physiological studies suggesting that, when animals or human subjects learn perceptual tasks, the neural modifications associated with the learning are distributed according to the spatial arrangement of the primary sensory cortical map. Topographical cortical representations of sensory events, therefore, appear to constitute a true structural framework for information processing and plasticity
The role of individual spikes and spike patterns in population coding of stimulus location in rat somatosensory cortex
No full textThis report addresses the nature of population coding in sensory cortex by applying information theoretic analysis to data recorded simultaneously from neuron pairs located in primary somatosensory cortex of anaesthetised rats. We studied how cortical spike trains code for the location of a whisker stimulus on the rat's snout. We found that substantially more information was conveyed by 10 ms precision spike timing compared with that conveyed by the number of spikes counted over a 40 ms response interval. Most of this information was accounted for by the timing of individual spikes. In particular, it was the first post-stimulus spikes that were crucial. Spike patterns within individual cells played a smaller role; spike patterns across cells were negligible. This pattern of results was robust both to the exact nature of the stimulus set and to the precision at which spikes were binned. © 2002 Elsevier Science Ireland Ltd. All rights reserved
Rasmus Petersen house and rock garden from bridge, located near Redmond, Oregon, between 1940 and 1950
No full textPH Coll 652.8Rasmus Petersen was born in 1883 in Denmark. In 1900, Petersen immigrated to the United States and settled in the state of Oregon in the vicinity of Redmond near the Cascade Mountains in 1906. He built a two-story Craftsman house and adjoining farm. As a personal hobby, he began collecting rocks on his land, including Oregon agates, obsidian, petrified wood, malachite, and jasper. In 1935, Petersen began building miniature buildings, monuments, and bridges out of rocks. By his death in 1952, Petersen had created a four-acre rock garden. Petersen's Rock Garden (called Petersen Rock Garden and Museum from the mid 1950s on) is a well-known Oregon roadside attraction.Scanned from a photographic print at 100 dpi in JPEG format at compression rate 3 and resized to 768x600 ppi. 201
Organisationsstrukturelle påvirkninger på kognitiv kommunikation i tværkommunale kulturproducerende organisationer
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