4,049 research outputs found
Development of Feeding Cues During Infancy and Toddlerhood
To enhance responsive feeding, this study aimed to characterize the development of feeding cues during infancy and toddlerhood
The energetics of the gradual phase
Reseachers compare results with those in the chapter by Moore et al. (1980), who reached five main conclusions about the gradual phase: (1) the typical density of the soft X-ray emitting plasma is between 10 to the 11th power and 10 to the 12th power cm-3 for compact flares and between 10 to the 10th power and 10 to the 11th power cm-3 for a large-area flare; (2) cooling is by conduction and radiation in roughly equal proportions; (3) continual heating is needed in the decay phase of two-ribbon flares; (4) continual heating is probably not needed in compact events; (5) most of the soft-X-ray-emitting plasma results from chromospheric evaporation. The goal was to reexamine these problems with the data from the Solar Maximum Mission (SMM) and other supporting instruments as well as to take advantage of recent theoretical advances. SMM is capable of measuring coronal temperatures more accurately and with a better cadence than has been possible before. The SMM data set is also unique in that the complete transit of an active region was observed, with soft X-ray and UV images being taken every few minutes. Researcher's were therefore able to establish the pre-flare conditions of the region and see whether anything has changed as a result of the flare. The assumptions made in attempting to determine the required plasma parameters are described. The derived parameters for the five prime flares are presented, and the role of numerical simulations is discussed
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Capturing uncertainty in magnetospheric ultra-low frequency wave models
We develop and test an empirical model predicting ground-based observations of ultra-low frequency (ULF, 1-20 mHz) wave power across a range of frequencies, latitudes and magnetic local time sectors. This is parameterized by instantaneous solar wind speed , variance in proton number density and interplanetary southward magnetic field . A probabilistic model of ULF wave power will allow us to address uncertainty in radial diffusion coefficients and therefore improve diffusion modeling of radial transport in Earth's outer radiation belt. Our model can be used in two ways to reproduce wave power; by sampling from conditional probability distribution functions or by using the mean (expectation) values. We derive a method for testing the quality of the parameterization and test the ability of the model to reproduce ULF wave power time series. Sampling is a better method for reproducing power over an extended time period as it retains the same overall distribution while mean values are better for predicting the power in a time series. The model predicts each hour in a time series better than the assumption that power persists from the preceding hour. Finally, we review other sources of diffusion coefficient uncertainty. Although this wave model is designed principally for the goal of improved radial diffusion coefficients to include in outer radiation belt diffusion based modeling, we anticipate that our model can also be used to investigate the occurrence of ULF waves throughout the magnetosphere and hence the physics of ULF wave generation and propagation
On high-speed turning of a third-generation gamma titanium aluminide
Gamma titanium aluminides are heat-resistant intermetallic alloys predestined to be employed in components suffering from high mechanical stresses and thermal loads. These materials are regarded as difficult to cut, so this makes process adaptation essential in order to obtain high-quality and defect-free surfaces suitable for aerospace and automotive parts. In this paper, an innovative approach for longitudinal external high-speed turning of a third-generation Ti-45Al-8Nb- 0.2C-0.2B gamma titanium aluminide is presented. The experimental campaign has been executed with different process parameters, tool geometries and lubrication conditions. The results are discussed in terms of surface roughness/integrity, chip morphology, cutting forces and tool wear. Experimental evidence showed that, due to the high cutting speed, the high temperatures reached in the shear zone improve chip formation, so a crack-free surface can be obtained. Furthermore, the use of a cryogenic lubrication system has been identified in order to reduce the huge tool wear, which represents the main drawback when machining gamma titanium aluminides under the chosen process condition
New Rotation Periods in the Pleiades: Interpreting Activity Indicators
We present results of photometric monitoring campaigns of G, K and M dwarfs in the Pleiades carried out in 1994, 1995 and 1996. We have determined rotation periods for 18 stars in this cluster. In this paper, we examine the validity of using observables such as X-ray activity and amplitude of photometric variations as indicators of angular momentum loss. We report the discovery of cool, slow rotators with high amplitudes of variation. This contradicts previous conclusions about the use of amplitudes as an alternate diagnostic of the saturation of angular momentum loss. We show that the X-ray data can be used as observational indicators of mass-dependent saturation in the angular momentum loss proposed on theoretical grounds
A Rewriting-Logic-Based Technique for Modeling Thermal Systems
This paper presents a rewriting-logic-based modeling and analysis technique
for physical systems, with focus on thermal systems. The contributions of this
paper can be summarized as follows: (i) providing a framework for modeling and
executing physical systems, where both the physical components and their
physical interactions are treated as first-class citizens; (ii) showing how
heat transfer problems in thermal systems can be modeled in Real-Time Maude;
(iii) giving the implementation in Real-Time Maude of a basic numerical
technique for executing continuous behaviors in object-oriented hybrid systems;
and (iv) illustrating these techniques with a set of incremental case studies
using realistic physical parameters, with examples of simulation and model
checking analyses.Comment: In Proceedings RTRTS 2010, arXiv:1009.398
Meningococcal genetic variation mechanisms viewed through comparative analysis of Serogroup C strain FAM18
Copyright @ 2007 Public Library of ScienceThe bacterium Neisseria meningitidis is commonly found harmlessly colonising the mucosal surfaces of the human nasopharynx. Occasionally strains can invade host tissues causing septicaemia and meningitis, making the bacterium a major cause of morbidity and mortality in both the developed and developing world. The species is known to be diverse in many ways, as a product of its natural transformability and of a range of recombination and mutation-based systems. Previous work on pathogenic Neisseria has identified several mechanisms for the generation of diversity of surface structures, including phase variation based on slippage-like mechanisms and sequence conversion of expressed genes using information from silent loci. Comparison of the genome sequences of two N. meningitidis strains, serogroup B MC58 and serogroup A Z2491, suggested further mechanisms of variation, including C-terminal exchange in specific genes and enhanced localised recombination and variation related to repeat arrays. We have sequenced the genome of N. meningitidis strain FAM18, a representative of the ST-11/ET-37 complex, providing the first genome sequence for the disease-causing serogroup C meningococci; it has 1,976 predicted genes, of which 60 do not have orthologues in the previously sequenced serogroup A or B strains. Through genome comparison with Z2491 and MC58 we have further characterised specific mechanisms of genetic variation in N. meningitidis, describing specialised loci for generation of cell surface protein variants and measuring the association between noncoding repeat arrays and sequence variation in flanking genes. Here we provide a detailed view of novel genetic diversification mechanisms in N. meningitidis. Our analysis provides evidence for the hypothesis that the noncoding repeat arrays in neisserial genomes (neisserial intergenic mosaic elements) provide a crucial mechanism for the generation of surface antigen variants. Such variation will have an impact on the interaction with the host tissues, and understanding these mechanisms is important to aid our understanding of the intimate and complex relationship between the human nasopharynx and the meningococcus.This work was supported by the Wellcome Trust through the Beowulf Genomics Initiative
New rotation periods in the Pleiades: Interpreting activity indicators
We present results of photometric monitoring campaigns of G, K and M dwarfs
in the Pleiades carried out in 1994, 1995 and 1996. We have determined rotation
periods for 18 stars in this cluster. In this paper, we examine the validity of
using observables such as X-ray activity and amplitude of photometric
variations as indicators of angular momentum loss. We report the discovery of
cool, slow rotators with high amplitudes of variation. This contradicts
previous conclusions about the use of amplitudes as an alternate diagnostic of
the saturation of angular momentum loss. We show that the X-ray data can be
used as observational indicators of mass-dependent saturation in the angular
momentum loss proposed on theoretical grounds.Comment: 24 pages, LaTex (AASTeX); includes 8 postscript figures and 4 Latex
tables. To appear in ApJ, Feb. 1, 1998. Postscript version of preprint can be
obtained from http://casa.colorado.edu/~anitak/pubs.htm
An Australian rental housing conditions research infrastructure
Each year the proportion of Australians who rent their home increases and, for the first time in generations, there are now as many renters as outright homeowners. Researchers and policy makers, however, know very little about housing conditions within Australia's rental housing sector due to a lack of systematic, reliable data. In 2020, a collaboration of Australian universities commissioned a survey of tenant households to build a data infrastructure on the household and demographic characteristics, housing quality and conditions in the Australian rental sector. This data infrastructure was designed to be national (representative across all Australian States and Territories), and balanced across key population characteristics. The resultant Australian Rental Housing Conditions Dataset (ARHCD) is a publicly available data infrastructure for researchers and policy makers, providing a basis for national and international research
Influence of respiratory rate and end-expiratory pressure variation on cyclic alveolar recruitment in an experimental lung injury model
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