61,566 research outputs found
The NASA Astrophysics Data System: The Search Engine and its User Interface
The ADS Abstract and Article Services provide access to the astronomical
literature through the World Wide Web (WWW). The forms based user interface
provides access to sophisticated searching capabilities that allow our users to
find references in the fields of Astronomy, Physics/Geophysics, and
astronomical Instrumentation and Engineering. The returned information includes
links to other on-line information sources, creating an extensive astronomical
digital library. Other interfaces to the ADS databases provide direct access to
the ADS data to allow developers of other data systems to integrate our data
into their system.
The search engine is a custom-built software system that is specifically
tailored to search astronomical references. It includes an extensive synonym
list that contains discipline specific knowledge about search term
equivalences.
Search request logs show the usage pattern of the various search system
capabilities. Access logs show the world-wide distribution of ADS users.
The ADS can be accessed at http://adswww.harvard.eduComment: 23 pages, 18 figures, 11 table
Stochastic Continuous Time Neurite Branching Models with Tree and Segment Dependent Rates
In this paper we introduce a continuous time stochastic neurite branching
model closely related to the discrete time stochastic BES-model. The discrete
time BES-model is underlying current attempts to simulate cortical development,
but is difficult to analyze. The new continuous time formulation facilitates
analytical treatment thus allowing us to examine the structure of the model
more closely. We derive explicit expressions for the time dependent
probabilities p(\gamma, t) for finding a tree \gamma at time t, valid for
arbitrary continuous time branching models with tree and segment dependent
branching rates. We show, for the specific case of the continuous time
BES-model, that as expected from our model formulation, the sums needed to
evaluate expectation values of functions of the terminal segment number
\mu(f(n),t) do not depend on the distribution of the total branching
probability over the terminal segments. In addition, we derive a system of
differential equations for the probabilities p(n,t) of finding n terminal
segments at time t. For the continuous BES-model, this system of differential
equations gives direct numerical access to functions only depending on the
number of terminal segments, and we use this to evaluate the development of the
mean and standard deviation of the number of terminal segments at a time t. For
comparison we discuss two cases where mean and variance of the number of
terminal segments are exactly solvable. Then we discuss the numerical
evaluation of the S-dependence of the solutions for the continuous time
BES-model. The numerical results show clearly that higher S values, i.e. values
such that more proximal terminal segments have higher branching rates than more
distal terminal segments, lead to more symmetrical trees as measured by three
tree symmetry indicators.Comment: 41 pages, 2 figures, revised structure and text improvement
Improved Attack on the Cellular Authentication and Voice Encryption Algorithm
We present new cryptanalysis of the Telecommunications hash algorithm known as Cellular Authentication and Voice Encryption Algorithm (CAVE). The previous guess-and-determine style reconstruction attack requires (resp. ) evaluations of CAVE-4 (resp. CAVE-8) to find a single valid pre-image (one which satisfies the input redundancy). Here we present a new attack that finds emph{all} valid pre-images with effort equivalent to around evaluations of the algorithm for both CAVE-4 and CAVE-8
Embedded Implicit Stand-ins for Animated Meshes: a Case of Hybrid Modelling
In this paper we address shape modelling problems, encountered in computer animation and computer games development that are difficult to solve just using polygonal meshes. Our approach is based on a hybrid modelling concept that combines polygonal meshes with implicit surfaces. A hybrid model consists of an animated polygonal mesh and an approximation of this mesh by a convolution surface stand-in that is embedded within it or is attached to it. The motions of both objects are synchronised using a rigging skeleton. This approach is used to model the interaction between an animated mesh object and a viscoelastic substance, normally modelled in implicit form. The adhesive behaviour of the viscous object is modelled using geometric blending operations on the corresponding implicit surfaces. Another application of this approach is the creation of metamorphosing implicit surface parts that are attached to an animated mesh. A prototype implementation of the proposed approach and several examples of modelling and animation with near real-time preview times are presented
New encouraging developments in contact prediction: Assessment of the CASP11 results
This article provides a report on the state-of-the-art in the prediction of intra-molecular residue-residue contacts in proteins
based on the assessment of the predictions submitted to the CASP11 experiment. The assessment emphasis is placed on the
accuracy in predicting long-range contacts. Twenty-nine groups participated in contact prediction in CASP11. At least eight
of them used the recently developed evolutionary coupling techniques, with the top group (CONSIP2) reaching precision of
27% on target proteins that could not be modeled by homology. This result indicates a breakthrough in the development of
methods based on the correlated mutation approach. Successful prediction of contacts was shown to be practically helpful
in modeling three-dimensional structures; in particular target T0806 was modeled exceedingly well with accuracy not yet
seen for ab initio targets of this size (>250 residues
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