133,627 research outputs found
Towards structured, block-based PDF
The Portable Document Format (PDF), defined by Adobe Systems Inc. as the basis of its Acrobat product range, is discussed in some detail. Particular emphasis is given to its flexible object-oriented structure, which has yet to be fully exploited. It is currently used to represent not logical structure but simply a series of pages and associated resources. A definition of an Encapsulated PDF (EPDF) is presented, in which EPDF blocks carry with them their own resource requirements, together with geometrical and logical information. A block formatter called Juggler is described which can lay out EPDF blocks from various sources onto new pages. Future revisions of PDF supporting uniquely-named EPDF blocks tagged with semantic information would assist in composite-pagemakeup and could even lead to fully revisable PDF
Uncertainty in Soft Temporal Constraint Problems:A General Framework and Controllability Algorithms forThe Fuzzy Case
In real-life temporal scenarios, uncertainty and preferences are often
essential and coexisting aspects. We present a formalism where quantitative
temporal constraints with both preferences and uncertainty can be defined. We
show how three classical notions of controllability (that is, strong, weak, and
dynamic), which have been developed for uncertain temporal problems, can be
generalized to handle preferences as well. After defining this general
framework, we focus on problems where preferences follow the fuzzy approach,
and with properties that assure tractability. For such problems, we propose
algorithms to check the presence of the controllability properties. In
particular, we show that in such a setting dealing simultaneously with
preferences and uncertainty does not increase the complexity of controllability
testing. We also develop a dynamic execution algorithm, of polynomial
complexity, that produces temporal plans under uncertainty that are optimal
with respect to fuzzy preferences
Selective advantage for multicellular replicative strategies: A two-cell example
This paper develops a quasispecies model where cells can adopt a two-cell
survival strategy. Within this strategy, pairs of cells join together, at which
point one of the cells sacrifices its own replicative ability for the sake of
the other cell. We develop a simplified model for the evolutionary dynamics of
this process, allowing us to solve for the steady-state using standard
approaches from quasispecies theory. We find that our model exhibits two
distinct regimes of behavior: At low concentrations of limiting resource, the
two-cell strategy outcompetes the single-cell survival strategy, while at high
concentrations of limiting resource, the single-cell survival strategy
dominates. Associated with the two solution regimes of our model is a
localization to delocalization transition over the portion of the genome coding
for the multicell strategy, analogous to the error catastrophe in standard
quasispecies models. The existence of such a transition indicates that
multicellularity can emerge because natural selection does not act on specific
cells, but rather on replicative strategies. Within this framework, individual
cells become the means by which replicative strategies are propagated. Such a
framework is therefore consistent with the concept that natural selection does
not act on individuals, but rather on populations.Comment: 4 pages, 2 figures, to be submitted to Physical Review Letter
Magnetic Forming Coil Design and Development Final Summary Report, 17 Jun. 1963 - 31 Mar. 1964
Magnetic forming coils for corrective forming of weld-induced distortions in stiffened panel
Survey of Human Mitochondrial Diseases Using New Genomic/Proteomic Tools
BACKGROUND. We have constructed Bayesian prior-based, amino-acid sequence profiles for the complete yeast mitochondrial proteome and used them to develop methods for identifying and characterizing the context of protein mutations that give rise to human mitochondrial diseases. (Bayesian priors are conditional probabilities that allow the estimation of the likelihood of an event - such as an amino-acid substitution - on the basis of prior occurrences of similar events.) Because these profiles can assemble sets of taxonomically very diverse homologs, they enable identification of the structurally and/or functionally most critical sites in the proteins on the basis of the degree of sequence conservation. These profiles can also find distant homologs with determined three-dimensional structures that aid in the interpretation of effects of missense mutations. RESULTS. This survey reports such an analysis for 15 missense mutations one insertion and three deletions involved in Leber's hereditary optic neuropathy, Leigh syndrome, mitochondrial neurogastrointestinal encephalomyopathy, Mohr-Tranebjaerg syndrome, iron-storage disorders related to Friedreich's ataxia, and hereditary spastic paraplegia. We present structural correlations for seven of the mutations. CONCLUSIONS. Of the 19 mutations analyzed, 14 involved changes in very highly conserved parts of the affected proteins. Five out of seven structural correlations provided reasonable explanations for the malfunctions. As additional genetic and structural data become available, this methodology can be extended. It has the potential for assisting in identifying new disease-related genes. Furthermore, profiles with structural homologs can generate mechanistic hypotheses concerning the underlying biochemical processes - and why they break down as a result of the mutations.United States Department of Energy (DE-FG02-98ER62558); National Science Foundation (DBI-9807993
Methodology for estimation of total body composition in laboratory mammals
A standardized dissection and chemical analysis procedure was developed for individual animals of several species in the size range mouse to monkey (15 g to 15 kg). The standardized procedure permits rigorous comparisons to be made both interspecifically and intraspecifically of organ weights and gross chemical composition in mammalian species series, and was applied successfully to laboratory mice, hamsters, rats, guinea pigs, and rabbits, as well as to macaque monkeys. The procedure is described in detail
Autonomous flight and remote site landing guidance research for helicopters
Automated low-altitude flight and landing in remote areas within a civilian environment are investigated, where initial cost, ongoing maintenance costs, and system productivity are important considerations. An approach has been taken which has: (1) utilized those technologies developed for military applications which are directly transferable to a civilian mission; (2) exploited and developed technology areas where new methods or concepts are required; and (3) undertaken research with the potential to lead to innovative methods or concepts required to achieve a manual and fully automatic remote area low-altitude and landing capability. The project has resulted in a definition of system operational concept that includes a sensor subsystem, a sensor fusion/feature extraction capability, and a guidance and control law concept. These subsystem concepts have been developed to sufficient depth to enable further exploration within the NASA simulation environment, and to support programs leading to the flight test
In vitro and in vivo effects of salbutamol on neutrophil function in acute lung injury
Background: Intravenous salbutamol (albuterol) reduces lung water in patients with the acute respiratory
distress syndrome (ARDS). Experimental data show that it also reduces pulmonary neutrophil accumulation or
activation and inflammation in ARDS.
Aim: To investigate the effects of salbutamol on neutrophil function.
Methods: The in vitro effects of salbutamol on neutrophil function were determined. Blood and
bronchoalveolar lavage (BAL) fluid were collected from 35 patients with acute lung injury (ALI)/ARDS, 14
patients at risk from ARDS and 7 ventilated controls at baseline and after 4 days’ treatment with placebo or
salbutamol (ALI/ARDS group). Alveolar–capillary permeability was measured in vivo by thermodilution
(PiCCO). Neutrophil activation, adhesion molecule expression and inflammatory cytokines were measured.
Results: In vitro, physiological concentrations of salbutamol had no effect on neutrophil chemotaxis, viability
or apoptosis. Patients with ALI/ARDS showed increased neutrophil activation and adhesion molecule
expression compared with at risk-patients and ventilated controls. There were associations between alveolar–
capillary permeability and BAL myeloperoxidase (r = 0.4, p = 0.038) and BAL interleukin 8 (r = 0.38,
p = 0.033). In patients with ALI/ARDS, salbutamol increased numbers of circulating neutrophils but had no
effect on alveolar neutrophils.
Conclusion: At the onset of ALI/ARDS, there is increased neutrophil recruitment and activation. Physiological
concentrations of salbutamol did not alter neutrophil chemotaxis, viability or apoptosis in vitro. In vivo,
salbutamol increased circulating neutrophils, but had no effect on alveolar neutrophils or on neutrophil
activation. These data suggest that the beneficial effects of salbutamol in reducing lung water are unrelated to
modulation of neutrophil-dependent inflammatory pathways
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