21,423 research outputs found
Adjustment of interaural-time-difference analysis to sound level
To localize low-frequency sound sources in azimuth, the binaural system compares the timing of sound waves at the two ears with microsecond precision. A similarly high precision is also seen in the binaural processing of the envelopes of high-frequency complex sounds. Both for low- and high-frequency sounds, interaural time difference (ITD) acuity is to a large extent independent of sound level. The mechanisms underlying this level-invariant extraction of ITDs by the binaural system are, however, only poorly understood. We use high-frequency pip trains with asymmetric and dichotic pip envelopes in a combined psychophysical, electrophysiological, and modeling approach. Although the dichotic envelopes cannot be physically matched in terms of ITD, the match produced perceptually by humans is very reliable, and it depends systematically on the overall sound level. These data are reflected in neural responses from the gerbil lateral superior olive and lateral lemniscus. The results are predicted in an existing temporal-integration model extended with a level-dependent threshold criterion. These data provide a very sensitive quantification of how the peripheral temporal code is conditioned for binaural analysis
Development of technology for modeling of a 1/8-scale dynamic model of the shuttle Solid Rocket Booster (SRB)
A NASTRAN analysis of the solid rocket booster (SRB) substructure of the space shuttle 1/8-scale structural dynamics model. The NASTRAN finite element modeling capability was first used to formulate a model of a cylinder 10 in. radius by a 200 in. length to investigate the accuracy and adequacy of the proposed grid point spacing. Results were compared with a shell analysis and demonstrated relatively accurate results for NASTRAN for the lower modes, which were of primary interest. A finite element model of the full SRB was then formed using CQUAD2 plate elements containing membrane and bending stiffness and CBAR offset bar elements to represent the longerons and frames. Three layers of three-dimensional CHEXAI elements were used to model the propellant. This model, consisting of 4000 degrees of freedom (DOF) initially, was reduced to 176 DOF using Guyan reduction. The model was then submitted for complex Eigenvalue analysis. After experiencing considerable difficulty with attempts to run the complete model, it was split into two substructres. These were run separately and combined into a single 116 degree of freedom A set which was successfully run. Results are reported
Fast quantum algorithm for numerical gradient estimation
Given a blackbox for f, a smooth real scalar function of d real variables,
one wants to estimate the gradient of f at a given point with n bits of
precision. On a classical computer this requires a minimum of d+1 blackbox
queries, whereas on a quantum computer it requires only one query regardless of
d. The number of bits of precision to which f must be evaluated matches the
classical requirement in the limit of large n.Comment: additional references and minor clarifications and corrections to
version
Left Bit Right: For SPARQL Join Queries with OPTIONAL Patterns (Left-outer-joins)
SPARQL basic graph pattern (BGP) (a.k.a. SQL inner-join) query optimization
is a well researched area. However, optimization of OPTIONAL pattern queries
(a.k.a. SQL left-outer-joins) poses additional challenges, due to the
restrictions on the \textit{reordering} of left-outer-joins. The occurrence of
such queries tends to be as high as 50% of the total queries (e.g., DBPedia
query logs).
In this paper, we present \textit{Left Bit Right} (LBR), a technique for
\textit{well-designed} nested BGP and OPTIONAL pattern queries. Through LBR, we
propose a novel method to represent such queries using a graph of
\textit{supernodes}, which is used to aggressively prune the RDF triples, with
the help of compressed indexes. We also propose novel optimization strategies
-- first of a kind, to the best of our knowledge -- that combine together the
characteristics of \textit{acyclicity} of queries, \textit{minimality}, and
\textit{nullification}, \textit{best-match} operators. In this paper, we focus
on OPTIONAL patterns without UNIONs or FILTERs, but we also show how UNIONs and
FILTERs can be handled with our technique using a \textit{query rewrite}. Our
evaluation on RDF graphs of up to and over one billion triples, on a commodity
laptop with 8 GB memory, shows that LBR can process \textit{well-designed}
low-selectivity complex queries up to 11 times faster compared to the
state-of-the-art RDF column-stores as Virtuoso and MonetDB, and for highly
selective queries, LBR is at par with them.Comment: SIGMOD 201
Development of a tailored, telehealth intervention to address chronic pain and heavy drinking among people with HIV infection: integrating perspectives of patients in HIV care.
BACKGROUND:
Chronic pain and heavy drinking commonly co-occur and can infuence the course of HIV. There have been no interventions designed to address both of these conditions among people living with HIV (PLWH), and none that have used telehealth methods. The purpose of this study was to better understand pain symptoms, patterns of alcohol use, treatment experiences, and technology use among PLWH in order to tailor a telehealth intervention that addresses these conditions
SUBJECTS:
Ten participants with moderate or greater chronic pain and heavy drinking were recruited from a cohort of patients engaged in HIV-care (Boston Alcohol Research Collaborative on HIV/AIDS Cohort) and from an integrated HIV/primary care clinic at a large urban hospital.
METHODS:
One-on-one interviews were conducted with participants to understand experiences and treatment
of HIV, chronic pain, and alcohol use. Participants’ perceptions of the infuence of alcohol on HIV and chronic pain were explored as was motivation to change drinking. Technology use and treatment preferences were examined in the fnal section of the interview. Interviews were recorded, transcribed and uploaded into NVivo® v12 software for analysis. A codebook was developed based on interviews followed by thematic analysis in which specifc meanings were assigned to codes.
RESULTS:
A number of themes were identifed that had implications for intervention tailoring including: resilience
in coping with HIV; autonomy in health care decision-making; coping with pain, stress, and emotion; understanding treatment rationale; depression and social withdrawal; motives to drink and refrain from drinking; technology use and capacity; and preference for intervention structure and style. Ratings of intervention components indicated that participants viewed each of the proposed intervention content areas as “helpful” to “very helpful”. Videoconferencing was viewed as an acceptable modality for intervention delivery
CONCLUSIONS:
Results helped specify treatment targets and provided information about how to enhance intervention
delivery. The interviews supported the view that videoconferencing is an acceptable telehealth method of addressing chronic pain and heavy drinking among PLWH.UH2 AA026192 - NIAAA NIH HHSPublished versio
Applications of BGP-reflection functors: isomorphisms of cluster algebras
Given a symmetrizable generalized Cartan matrix , for any index , one
can define an automorphism associated with of the field of rational functions of independent indeterminates It is an isomorphism between two cluster algebras associated to the
matrix (see section 4 for precise meaning). When is of finite type,
these isomorphisms behave nicely, they are compatible with the BGP-reflection
functors of cluster categories defined in [Z1, Z2] if we identify the
indecomposable objects in the categories with cluster variables of the
corresponding cluster algebras, and they are also compatible with the
"truncated simple reflections" defined in [FZ2, FZ3]. Using the construction of
preprojective or preinjective modules of hereditary algebras by Dlab-Ringel
[DR] and the Coxeter automorphisms (i.e., a product of these isomorphisms), we
construct infinitely many cluster variables for cluster algebras of infinite
type and all cluster variables for finite types.Comment: revised versio
The Evolution of Distorted Rotating Black Holes III: Initial Data
In this paper we study a new family of black hole initial data sets
corresponding to distorted ``Kerr'' black holes with moderate rotation
parameters, and distorted Schwarzschild black holes with even- and odd-parity
radiation. These data sets build on the earlier rotating black holes of Bowen
and York and the distorted Brill wave plus black hole data sets. We describe
the construction of this large family of rotating black holes. We present a
systematic study of important properties of these data sets, such as the size
and shape of their apparent horizons, and the maximum amount of radiation that
can leave the system during evolution. These data sets should be a very useful
starting point for studying the evolution of highly dynamical black holes and
can easily be extended to 3D.Comment: 16 page
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