40,769 research outputs found
An ab initio HCN and HNC rotational vibrationallinelist for astronomy
We present a new ab initio HCN/HNC linelist. The linelist forms themost accurate and extensive HCN/HNC data set presently in existence.The data contain rotation vibration line frequencies and line strengths,for all transitions that are not rigorously dipole forbidden, between stateswith energy less than 18 000 cm-1 and with J ? 60
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Layered Fabrication of Branched Networks Using Lindenmayer Systems
A current challenge impeding the growth of bone tissue engineering is the lack of
functional scaffolds of geometric sizes greater than 10mm due to the inability of cells to
survive deep within the scaffold. It is hypothesized that these scaffolds must have an
inbuilt nutrient distribution network to sustain the uniform growth of cells. In this
paper, we seek to enhance the design and layered fabrication of scaffold internal
architecture through the development of Lindenmayer systems, a graphical language
based theory to create nutrient delivery networks. The scaffolds are fabricated using the
Texas Instruments DLP™ system through UV‐photopolymerization to produce
polyethylene glycol hydrogels with internal branch structures. The paper will discuss
the Lindenmayer system, process planning algorithms, layered fabrication of samples,
challenges and future tasks.Mechanical Engineerin
On Computing Maximal Independent Sets of Hypergraphs in Parallel
Whether or not the problem of finding maximal independent sets (MIS) in
hypergraphs is in (R)NC is one of the fundamental problems in the theory of
parallel computing. Unlike the well-understood case of MIS in graphs, for the
hypergraph problem, our knowledge is quite limited despite considerable work.
It is known that the problem is in \emph{RNC} when the edges of the hypergraph
have constant size. For general hypergraphs with vertices and edges,
the fastest previously known algorithm works in time with
processors. In this paper we give an EREW PRAM algorithm
that works in time with processors on general
hypergraphs satisfying , where
and . Our algorithm is
based on a sampling idea that reduces the dimension of the hypergraph and
employs the algorithm for constant dimension hypergraphs as a subroutine
A study of the ATLAS detector's sensitivity to quark compositeness
The sensitivity of ATLAS to processes characterised by high-energy hadronic jets has been
investigated, with analysis of both theoretical and experimental sources of uncertainty. This analysis
has been applied in particular to a study of a quark compositeness model
Search for New Physics with Long-Lived Neutral Particles in ATLAS: The Hidden Valley Scenario
With the start of the Large Hadron Collider a new energy frontier will be accessible to experimental particle physics, and many new models and extensions to the Standard Model will be tested. A unique class of these new models are those in which long-lived particles can decay mid-detector, leaving atypical signatures that are often missed by standard LHC-detector triggers. Such models include the Hidden Valley models and some supersymmetric models. Prospects for triggering-on and detecting long-lived neutral particles in the ATLAS detector are presented
HR4049: signature of nova nucleosynthesis ?
The post-Asymptotic Giant Branch (AGB) star HR4049 is in an eccentric binary
system with a relatively short period probably surrounded by a dusty
circumbinary disk. Extremely anomalous oxygen isotopic ratios, O16/O17 ~
O16/O18 ~ 7, have been measured from CO_2 molecules likely residing in the
disk. Such a composition cannot be explained in the framework of AGB and
post-AGB evolution while it can be qualitatively associated with the
nucleosynthesis occurring during nova outbursts. We discuss nova models, the
presence of a white dwarf companion to HR4049 and possible scenarios for the
dynamical evolution of this binary system. Circumbinary disks in which mixing
occurs between red-giant and nova material may also be invoked as the site of
formation of some rare types of meteoritic presolar grains.Comment: 4 pages, 2 figures, submitted for the proceedings of the 8th Nuclei
in the Cosmos symposium (Vancouver, Canada, 19-23 July 2004
A review of fracture mechanics life technology
Current lifetime prediction technology for structural components subjected to cyclic loads was reviewed. The central objectives of the project were to report the current state of and recommend future development of fracture mechanics-based analytical tools for modeling and forecasting subcritical fatigue crack growth in structures. Of special interest to NASA was the ability to apply these tools to practical engineering problems and the developmental steps necessary to bring vital technologies to this stage. A survey of published literature and numerous discussions with experts in the field of fracture mechanics life technology were conducted. One of the key points made is that fracture mechanics analyses of crack growth often involve consideration of fatigue and fracture under extreme conditions. Therefore, inaccuracies in predicting component lifetime will be dominated by inaccuracies in environment and fatigue crack growth relations, stress intensity factor solutions, and methods used to model given loads and stresses. Suggestions made for reducing these inaccuracies include: development of improved models of subcritical crack growth, research efforts aimed at better characterizing residual and assembly stresses that can be introduced during fabrication, and more widespread and uniform use of the best existing methods
Search for new physics with Long-Lived particles in ATLAS: The Hidden Valley Scenario
With the start of the Large Hadron Collider a new energy frontier will be accessible to experimental particle physics, and many new models and extensions to the Standard Model will be tested. A unique class of these new models are those in which long-lived particles can decay mid-detector, leaving atypical signatures that are often missed by standard LHC-detector triggers. Such models include the Hidden Valley models and some supersymmetric models. Prospects for triggering-on and detecting long-lived particles in the ATLAS detector are presented
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