8,406 research outputs found
Matching of spatially homogeneous non-stationary space--times to vacuum in cylindrical symmetry
We study the matching of LRS spatially homogeneous collapsing dust
space-times with non-stationary vacuum exteriors in cylindrical symmetry. Given
an interior with diagonal metric we prove existence and uniqueness results for
the exterior. The matched solutions contain trapped surfaces, singularities and
Cauchy horizons. The solutions cannot be asymptotically flat and we present
evidence that they are singular on the Cauchy horizons.Comment: LaTeX, 15 pages, 1 figure, submitted for publicatio
FMRI Clustering and False Positive Rates
Recently, Eklund et al. (2016) analyzed clustering methods in standard FMRI
packages: AFNI (which we maintain), FSL, and SPM [1]. They claimed: 1) false
positive rates (FPRs) in traditional approaches are greatly inflated,
questioning the validity of "countless published fMRI studies"; 2)
nonparametric methods produce valid, but slightly conservative, FPRs; 3) a
common flawed assumption is that the spatial autocorrelation function (ACF) of
FMRI noise is Gaussian-shaped; and 4) a 15-year-old bug in AFNI's 3dClustSim
significantly contributed to producing "particularly high" FPRs compared to
other software. We repeated simulations from [1] (Beijing-Zang data [2], see
[3]), and comment on each point briefly.Comment: 3 pages, 1 figure. A Letter accepted in PNA
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Correlates of Adult Sociometric Perception of Residential Groups of Emotionally Disturbed Children
The purpose of the present study is to determine whether adult supervisors of children's groups who accurately perceive the interpersonal structure of their groups are more able managers of their groups than are those adults who inaccurately judge the group's interpersonal structure
INVESTIGATING THE USE OF SAMPLE ENTROPY TO DETECT FATIGUE
Sample entropy can sensitively identify changes in biological signal regularity. The aim of this study was to investigate whether sample entropy could detect such change in human movement which may be attributable to fatigue or other factors. The regularity of kettlebell trajectories from simulated kettlebell sport competition performed by five experienced lifters was assessed using a novel moving window technique. Resultant entropy estimate trajectories indicate sensitivity to changes in regularity. Decrements in grip strength indicate this may be attributable to fatigue though other possibilities exist. The ability to easily model the resultant entropy trajectories is also demonstrated. The technique holds potential for use by practitioners though more work is required before implementation
Electrical Measurements on the Greenland Ice Sheet Project 2 Core
The Greenland Ice Sheet Project 2 (GISP2) electrical conductivity measurement (ECM) record is an indication of the concentration of H+ in the core. The ECM detected seasonal variations in the nitrate concentration of the core which were used to assist in dating the core by annual layer counting. Volcanic eruptions that produce acidic aerosols are recorded in the ECM record. Evidence of biomass burning is detected by the ECM because fire-related ammonium emissions neutralize the acids in the core. Rapid climate transitions associated with the Younger Dryas and Dansgaard/Oeschger interstadial events alter the concentration of alkaline dust and are detected by the ECM. The ECM has been used to develop stratigraphic ties between the GISP2 and the Greenland Ice Core Project cores. Users of the data should be aware of some instrument-related artifacts in the ECM record
Semiclassical charged black holes with a quantized massive scalar field
Semiclassical perturbations to the Reissner-Nordstrom metric caused by the
presence of a quantized massive scalar field with arbitrary curvature coupling
are found to first order in \epsilon = \hbar/M^2. The DeWitt-Schwinger
approximation is used to determine the vacuum stress-energy tensor of the
massive scalar field. When the semiclassical perturbation are taken into
account, we find extreme black holes will have a charge-to-mass ratio that
exceeds unity, as measured at infinity. The effects of the perturbations on the
black hole temperature (surface gravity) are studied in detail, with particular
emphasis on near extreme ``bare'' states that might become precisely zero
temperature ``dressed'' semiclassical black hole states. We find that for
minimally or conformally coupled scalar fields there are no zero temperature
solutions among the perturbed black holes.Comment: 19 pages; 1 figure; ReVTe
Speech synthesis by phonological structure matching.
This paper presents a new technique for speech synthesis
by unit selection. The technique works by specifying
the synthesis target and the speech database as phonological
trees, and using a selection algorithm which finds the
largest parts of trees in the database which match parts of
the target tree. The technique avoids many of the errors
made by prosody generation modules by incorporating
their operation in the selection implicitly. A technique
for using signal processing only when it is needed most
is also described. The technique produces better quality
speech than previous approaches and is also significantly
faster
Classification and Management of Wetlands in the Western Kentucky Coal Field
This is the first research report of a three-year project on wetland identification and management criteria in the western Kentucky coal field. The region is approximately 12,000 square kilometers and, due to its slight relief, contains many wetlands, some contiguous with surface coal mining operations. The overall objectives of the research project are 1) to identify, classify, and map wetlands in the western Kentucky coal field; 2) to evaluate the major biotic and abiotic factors that affect those wetlands; and 3) to develop strategies for the proper management of those wetlands.
The first report of this three-year project has involved the following tasks related to wetlands in the coal fields of western Kentucky: establishment of three intensive study sites in major wetlands for identification and assessment of management impacts, sampling tripe in May, July, and September to the intensive study sites, to measure water quality and ecological structure, development of a classification specifically for wetlands in western Kentucky and an application of the classification to the three intensive study sites, and development of conceptual models of the region, watersheds, and specific ecosystems, and preliminary simulations of a wetland model.
Our specific sites in western Kentucky are Cypress Creek Wetlands in Muhlenberg County, which are affected by mine drainage and channelization; Clear Creek Swamp in Hopkins County, which is affected by mine drainage and higher water levels; and Henderson Sloughs in Henderson County, which are affected by oil wells and clearing for agriculture. Preliminary analysis of field surveys demonstrates that several activities, particularly coal mining and oil \u27extraction, may affect the health of wetlands in western Kentucky. Drainage, logging, channelization, and impoundments have also caused significant alterations
Cloned defective interfering influenza virus protects ferrets from pandemic 2009 influenza A virus and allows protective immunity to be established
Influenza A viruses are a major cause of morbidity and mortality in the human population, causing epidemics in the winter, and occasional worldwide pandemics. In addition there are periodic outbreaks in domestic poultry, horses, pigs, dogs, and cats. Infections of domestic birds can be fatal for the birds and their human contacts. Control in man operates through vaccines and antivirals, but both have their limitations. In the search for an alternative treatment we have focussed on defective interfering (DI) influenza A virus. Such a DI virus is superficially indistinguishable from a normal virus but has a large deletion in one of the eight RNAs that make up the viral genome. Antiviral activity resides in the deleted RNA. We have cloned one such highly active DI RNA derived from segment 1 (244 DI virus) and shown earlier that intranasal administration protects mice from lethal disease caused by a number of different influenza A viruses. A more cogent model of human influenza is the ferret. Here we found that intranasal treatment with a single dose of 2 or 0.2 µg 244 RNA delivered as A/PR/8/34 virus particles protected ferrets from disease caused by pandemic virus A/California/04/09 (A/Cal; H1N1). Specifically, 244 DI virus significantly reduced fever, weight loss, respiratory symptoms, and infectious load. 244 DI RNA, the active principle, was amplified in nasal washes following infection with A/Cal, consistent with its amelioration of clinical disease. Animals that were treated with 244 DI RNA cleared infectious and DI viruses without delay. Despite the attenuation of infection and disease by DI virus, ferrets formed high levels of A/Cal-specific serum haemagglutination-inhibiting antibodies and were solidly immune to rechallenge with A/Cal. Together with earlier data from mouse studies, we conclude that 244 DI virus is a highly effective antiviral with activity potentially against all influenza A subtypes
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