250 research outputs found
Proton-Rich Nuclear Statistical Equilibrium
Proton-rich material in a state of nuclear statistical equilibrium (NSE) is
one of the least studied regimes of nucleosynthesis. One reason for this is
that after hydrogen burning, stellar evolution proceeds at conditions of equal
number of neutrons and protons or at a slight degree of neutron-richness.
Proton-rich nucleosynthesis in stars tends to occur only when hydrogen-rich
material that accretes onto a white dwarf or neutron star explodes, or when
neutrino interactions in the winds from a nascent proto-neutron star or
collapsar-disk drive the matter proton-rich prior to or during the
nucleosynthesis. In this paper we solve the NSE equations for a range of
proton-rich thermodynamic conditions. We show that cold proton-rich NSE is
qualitatively different from neutron-rich NSE. Instead of being dominated by
the Fe-peak nuclei with the largest binding energy per nucleon that have a
proton to nucleon ratio close to the prescribed electron fraction, NSE for
proton-rich material near freeze-out temperature is mainly composed of Ni56 and
free protons. Previous results of nuclear reaction network calculations rely on
this non-intuitive high proton abundance, which this paper will explain. We
show how the differences and especially the large fraction of free protons
arises from the minimization of the free energy as a result of a delicate
competition between the entropy and the nuclear binding energy.Comment: 4 pages, 7 figure
Testing Scalar-Tensor Gravity with Gravitational-Wave Observations of Inspiralling Compact Binaries
Observations of gravitational waves from inspiralling compact binaries using
laser-interferometric detectors can provide accurate measures of parameters of
the source. They can also constrain alternative gravitation theories. We
analyse inspiralling compact %binaries in the context of the scalar-tensor
theory of Jordan, Fierz, Brans and Dicke, focussing on the effect on the
inspiral of energy lost to dipole gravitational radiation, whose source is the
gravitational self-binding energy of the inspiralling bodies. Using a
matched-filter analysis we obtain a bound on the coupling constant of Brans-Dicke theory. For a neutron-star/black-hole binary, we find that
the bound could exceed the current bound of from
solar-system experiments, for sufficiently low-mass systems. For a neutron star and a black hole we find that a bound
is achievable. The bound decreases with
increasing black-hole mass. For binaries consisting of two neutron stars, the
bound is less than 500 unless the stars' masses differ by more than about . For two black holes, the behavior of the inspiralling binary is
observationally indistinguishable from its behavior in general relativity.
These bounds assume reasonable neutron-star equations of state and a detector
signal-to-noise ratio of 10.Comment: 10 pages, (3 figures upon request), WUGRAV-94-
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The Challenge of Spoken Language Systems: Research Directions for the Nineties
A spoken language system combines speech recognition, natural language processing and human interface technology. It functions by recognizing the person's words, interpreting the sequence of words to obtain a meaning in terms of the application, and providing an appropriate response back to the user. Potential applications of spoken language systems range from simple tasks, such as retrieving information from an existing database (traffic reports, airline schedules), to interactive problem solving tasks involving complex planning and reasoning (travel planning, traffic routing), to support for multilingual interactions. We examine eight key areas in which basic research is needed to produce spoken language systems: (1) robust speech recognition; (2) automatic training and adaptation; (3) spontaneous speech; (4) dialogue models; (5) natural language response generation; (6) speech synthesis and speech generation; (7) multilingual systems; and (8) interactive multimodal systems. In each area, we identify key research challenges, the infrastructure needed to support research, and the expected benefits. We conclude by reviewing the need for multidisciplinary research, for development of shared corpora and related resources, for computational support and far rapid communication among researchers. The successful development of this technology will increase accessibility of computers to a wide range of users, will facilitate multinational communication and trade, and will create new research specialties and jobs in this rapidly expanding area
Recommended from our members
The Challenge of Spoken Language Systems: Research Directions for the Nineties
A spoken language system combines speech recognition, natural language processing and human interface technology. It functions by recognizing the person's words, interpreting the sequence of words to obtain a meaning in terms of the application, and providing an appropriate response back to the user. Potential applications of spoken language systems range from simple tasks, such as retrieving information from an existing database (traffic reports, airline schedules), to interactive problem solving tasks involving complex planning and reasoning (travel planning, traffic routing), to support for multilingual interactions. We examine eight key areas in which basic research is needed to produce spoken language systems: (1) robust speech recognition; (2) automatic training and adaptation; (3) spontaneous speech; (4) dialogue models; (5) natural language response generation; (6) speech synthesis and speech generation; (7) multilingual systems; and (8) interactive multimodal systems. In each area, we identify key research challenges, the infrastructure needed to support research, and the expected benefits. We conclude by reviewing the need for multidisciplinary research, for development of shared corpora and related resources, for computational support and far rapid communication among researchers. The successful development of this technology will increase accessibility of computers to a wide range of users, will facilitate multinational communication and trade, and will create new research specialties and jobs in this rapidly expanding area
Colour categories are reflected in sensory stages of colour perception when stimulus issues are resolved
Debate exists about the time course of the effect of colour categories on visual processing. We investigated the effect of colour categories for two groups who differed in whether they categorised a blue-green boundary colour as the same- or different-category to a reliably-named blue colour and a reliably-named green colour. Colour differences were equated in just-noticeable differences to be equally discriminable. We analysed event-related potentials for these colours elicited on a passive visual oddball task and investigated the time course of categorical effects on colour processing. Support for category effects was found 100 ms after stimulus onset, and over frontal sites around 250 ms, suggesting that colour naming affects both early sensory and later stages of chromatic processing
Highlights of children with Cancer UK’s workshop on drug delivery in paediatric brain tumours
The first Workshop on Drug Delivery in Paediatric Brain Tumours was hosted in London by the charity Children with Cancer UK. The goals of the workshop were to break down the barriers to treating central nervous system (CNS) tumours in children, leading to new collaborations and further innovations in this under-represented and emotive field. These barriers include the physical delivery challenges presented by the blood–brain barrier, the underpinning reasons for the intractability of CNS cancers, and the practical difficulties of delivering cancer treatment to the brains of children. Novel techniques for overcoming these problems were discussed, new models brought forth, and experiences compared
Mind the gap!: Students' Understanding and Application of Social Work Values
This paper discusses a research project that explored the development of student social workers' values during the first year of professional education at one Scottish university. Questionnaires, based on a vignette, and focus groups established baseline information at the outset of the study. These methods were reapplied a year later to identify the extent to which students' values framework had developed, and the factors that had supported this. The study revealed that, by the end of that year, students could both identify and apply values to support them in their work with individuals to a greater extent than they could those to help them challenge structural discrimination. The study also highlighted the need for university-based teaching, and practice learning experiences, to provide more opportunities for reflection and discussion to support the development of values in student social workers
Mind the gap!: Students' Understanding and Application of Social Work Values
This paper discusses a research project that explored the development of student social workers' values during the first year of professional education at one Scottish university. Questionnaires, based on a vignette, and focus groups established baseline information at the outset of the study. These methods were reapplied a year later to identify the extent to which students' values framework had developed, and the factors that had supported this. The study revealed that, by the end of that year, students could both identify and apply values to support them in their work with individuals to a greater extent than they could those to help them challenge structural discrimination. The study also highlighted the need for university-based teaching, and practice learning experiences, to provide more opportunities for reflection and discussion to support the development of values in student social workers
Atypicalities in Perceptual Adaptation in Autism Do Not Extend to Perceptual Causality
A recent study showed that adaptation to causal events (collisions) in adults caused subsequent events to be less likely perceived as causal. In this study, we examined if a similar negative adaptation effect for perceptual causality occurs in children, both typically developing and with autism. Previous studies have reported diminished adaptation for face identity, facial configuration and gaze direction in children with autism. To test whether diminished adaptive coding extends beyond high-level social stimuli (such as faces) and could be a general property of autistic perception, we developed a child-friendly paradigm for adaptation of perceptual causality. We compared the performance of 22 children with autism with 22 typically developing children, individually matched on age and ability (IQ scores). We found significant and equally robust adaptation aftereffects for perceptual causality in both groups. There were also no differences between the two groups in their attention, as revealed by reaction times and accuracy in a change-detection task. These findings suggest that adaptation to perceptual causality in autism is largely similar to typical development and, further, that diminished adaptive coding might not be a general characteristic of autism at low levels of the perceptual hierarchy, constraining existing theories of adaptation in autism.16 page(s
The Association of Dietary Intake of Purine-Rich Vegetables, Sugar-Sweetened Beverages and Dairy with Plasma Urate, in a Cross-Sectional Study
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