1,049 research outputs found
Mapping of Mammoth Cave: How Cartography Fueled Discoveries, with Emphasis on Max Kaemper’s 1908 Map
Maps came first at Mammoth Cave, Kentucky. Then came explorers who used the maps to make discoveries as they gained a more comprehensive understanding of the longest cave in the world. The saga of mapping at Mammoth Cave parallels the mapping of North America from the 1600s onward. The first map was an “Eye-Draught Map of Mammoth Cave”, penned from memory in 1811, not a survey, to acquaint merchants with the location of saltpeter dirt. In 1835 the managers of Mammoth Cave hired a surveyor, Edmond Lee, to survey and map and profile the main cave passages. Stephen Bishop, a slave guide at Mammoth Cave (1838 – 1857) drew a comprehensive map in 1842, partly based on the Lee survey. Bishop’s map is a schematic diagram showing many named passages and their relationship to each other. Max Kaemper, a German civil engineer, was hired by the cave manager to make an instrumental survey of the cave in 1908 and to draft a map showing five levels of the cave in distinctive colors. The Walker survey in 1936 served to establish an accurate baseline through the cave and tied entrances to each other. Ray Nelson drafted an unpublished map of the Walker survey, New Discovery survey, and more in 1956. Cave Research Foundation cartographers began mapping passages in the Flint Ridge Cave System in 1954 resulting in one of the first cave maps plotted on a topographic map. The Flint Ridge Folio, 1964, brought Flint Ridge mapping up to Kaemper’s graphic standard with the improvement of the superimposition of the surface topography. Since the 1972 connection between Flint Ridge and Mammoth Cave Ridge, Mammoth Cave has blossomed into a cave with a comprehensive high accuracy set of cave maps showing 365 miles of connected cave. The Kaemper map lay fallow in Park Service files for many years until it was rediscovered by James F. Quinlan in 1963. Diana Daunt retraced the original Kaemper map for publication by the Cave Research Foundation. The utility of the Kaemper map is its use by generations of explorers to find their way around in Mammoth Cave and to ultimately resurvey and remap all the features Kaemper recorded, and more
Impairment in preattentive visual processing in patients with Parkinson's disease
We explored the possibility of whether preattentive visual processing is impaired in Parkinson's disease. With this aim, visual discrimination thresholds for orientation texture stimuli were determined in two separate measurement sessions in 16 patients with idiopathic Parkinson's disease. The results were compared with those of 16 control subjects age-matched and 16 young healthy volunteers. Discrimination thresholds were measured in a four-alternative spatial forced-choice paradigm, in which subjects judged the location of a target embedded in a background of distractors. Four different stimulus configurations were employed: (i) a group of vertical targets among horizontal distractors (`vertical line targets'); (ii) targets with varying levels of orientation difference on a background of spatially filtered vertically oriented noise (`Gaussian filtered noise'); (iii) one `L' among 43 `+' signs (`texton'), all of which assess preattentive visual processing; and (iv) control condition, of one `L' among 43 `T' distractors (`non-texton' search target), which reflects attentive visual processing. In two of the preattentive tasks (filtered noise and texton), patients with Parkinson's disease required significantly greater orientation differences and longer stimulus durations, respectively. In contrast, their performance in the vertical line target and non-texton search target was comparable to that of the matched control subjects. These differences were more pronounced in the first compared with the second session. Duration of illness and age within the patient group correlated significantly with test performance. In all conditions tested, the young control subjects performed significantly better than the more elderly control group, further indicating an effect of age on this form of visual processing. The results suggest that, in addition to the well documented impairment in retinal processing, idiopathic Parkinson's disease is associated with a deficit in preattentive cortical visual processing
Changing Arctic snow cover: A review of recent developments and assessment of future needs for observations, modelling, and impacts
Open Access Journal (SHERPA RoMEO Green)
DOI: 10.1007/s13280-016-0770-0Snow is a critically important and rapidly
changing feature of the Arctic. However, snow-cover and
snowpack conditions change through time pose challenges
for measuring and prediction of snow. Plausible scenarios
of how Arctic snow cover will respond to changing Arctic
climate are important for impact assessments and
adaptation strategies. Although much progress has been
made in understanding and predicting snow-cover changes
and their multiple consequences, many uncertainties
remain. In this paper, we review advances in snow
monitoring and modelling, and the impact of snow
changes on ecosystems and society in Arctic regions.
Interdisciplinary activities are required to resolve the
current limitations on measuring and modelling snow
characteristics through the cold season and at different
spatial scales to assure human well-being, economic
stability, and improve the ability to predict manage and
adapt to natural hazards in the Arctic region
Automated Certification of Authorisation Policy Resistance
Attribute-based Access Control (ABAC) extends traditional Access Control by
considering an access request as a set of pairs attribute name-value, making it
particularly useful in the context of open and distributed systems, where
security relevant information can be collected from different sources. However,
ABAC enables attribute hiding attacks, allowing an attacker to gain some access
by withholding information. In this paper, we first introduce the notion of
policy resistance to attribute hiding attacks. We then propose the tool ATRAP
(Automatic Term Rewriting for Authorisation Policies), based on the recent
formal ABAC language PTaCL, which first automatically searches for resistance
counter-examples using Maude, and then automatically searches for an Isabelle
proof of resistance. We illustrate our approach with two simple examples of
policies and propose an evaluation of ATRAP performances.Comment: 20 pages, 4 figures, version including proofs of the paper that will
be presented at ESORICS 201
Antagonism of the mammalian target of rapamycin selectively mediates metabolic effects of epidermal growth factor receptor inhibition and protects human malignant glioma cells from hypoxia-induced cell death
Although inhibition of the epidermal growth factor receptor is a plausible therapy for malignant gliomas that, in vitro, enhances apoptosis, the results of clinical trials have been disappointing. The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that integrates starvation signals and generates adaptive responses that aim at the maintenance of energy homeostasis. Antagonism of mTOR has been suggested as a strategy to augment the efficacy of epidermal growth factor receptor inhibition by interfering with deregulated signalling cascades downstream of Akt. Here we compared effects of antagonism of mTOR utilizing rapamycin or a small hairpin RNA-mediated gene silencing to those of epidermal growth factor receptor inhibition or combined inhibition of epidermal growth factor receptor and mTOR in human malignant glioma cells. In contrast to epidermal growth factor receptor inhibition, mTOR antagonism neither induced cell death nor enhanced apoptosis induced by CD95 ligand or chemotherapeutic drugs. However, mTOR inhibition mimicked the hypoxia-protective effects of epidermal growth factor receptor inhibition by maintaining adenosine triphosphate levels. These in vitro experiments thus challenge the current view of mTOR as a downstream target of Akt that mediates antiapoptotic stimuli. Under the conditions of the tumour microenvironment, metabolic effects of inhibition of epidermal growth factor receptor, Akt and mTOR may adversely affect outcome by protecting the hypoxic tumour cell fractio
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