1,152 research outputs found
Validation of an Impulse Measurement Technique with High Temporal and Spatial Resolutions
AbstractWe present a new experimental technique to measure the force-time history of high-velocity impacts and high pressure blast waves. The technique is based on the classic Hopkinson-type strain bar, coupled with an interferometric velocimeter instead of strain gauges. The major benefits of this setup are its accuracy, temporal resolution, and its imperviousness to electromagnetic interferences. We explain the keys concepts behind the technique and describe the experimental setup. We present experimental and numerical data as proof-of-concept and discuss preliminary studies on the effect of plastic deformation of the bar and its consequences on the interpretation of the measured impulse-history
Radio Triggered Star Formation in Cooling Flows
The giant galaxies located at the centers of cluster cooling flows are
frequently sites of vigorous star formation. In some instances, star formation
appears to have been triggered by the galaxy's radio source. The colors and
spectral indices of the young populations are generally consistent with short
duration bursts or continuous star formation for durations much less than 1
Gyr, which is less than the presumed ages of cooling flows. The star formation
properties are inconsistent with fueling by a continuously accreting cooling
flow, although the prevalence of star formation is consistent with repeated
bursts and periodic refueling. Star formation may be fueled, in some cases, by
cold material stripped from neighboring cluster galaxies
The development of emotion recognition from facial expressions and non-linguistic vocalizations during childhood
Sensitivity to facial and vocal emotion is fundamental to children's social competence. Previous research has focused on children's facial emotion recognition, and few studies have investigated non-linguistic vocal emotion processing in childhood. We compared facial and vocal emotion recognition and processing biases in 4- to 11-year-olds and adults. Eighty-eight 4- to 11-year-olds and 21 adults participated. Participants viewed/listened to faces and voices (angry, happy, and sad) at three intensity levels (50%, 75%, and 100%). Non-linguistic tones were used. For each modality, participants completed an emotion identification task. Accuracy and bias for each emotion and modality were compared across 4- to 5-, 6- to 9- and 10- to 11-year-olds and adults. The results showed that children's emotion recognition improved with age; preschoolers were less accurate than other groups. Facial emotion recognition reached adult levels by 11 years, whereas vocal emotion recognition continued to develop in late childhood. Response bias decreased with age. For both modalities, sadness recognition was delayed across development relative to anger and happiness. The results demonstrate that developmental trajectories of emotion processing differ as a function of emotion type and stimulus modality. In addition, vocal emotion processing showed a more protracted developmental trajectory, compared to facial emotion processing. The results have important implications for programmes aiming to improve children's socio-emotional competence
Automated measurement of redshift from mid-infrared low resolution spectroscopy
We present a new SED-fitting based routine for redshift determination that is
optimised for mid-infrared (MIR) low-resolution spectroscopy. Its flexible
template scaling increases the sensitivity to slope changes and small scale
features in the spectrum, while a new selection algorithm called Maximum
Combined Pseudo-Likelihood (MCPL) provides increased accuracy and a lower
number of outliers compared to the standard maximum-likelihood (ML) approach.
Unlike ML, MCPL searches for local (instead of absolute) maxima of a
'pseudo-likelihood' (PL) function, and combines results obtained for all the
templates in the library to weed out spurious redshift solutions. The
capabilities of MCPL are demonstrated by comparing its results to those of
regular ML and to the optical spectroscopic redshifts of a sample of 491
Spitzer/IRS spectra from sources at 0<z<3.7. MCPL achieves a redshift accuracy
dz/(1+z)<0.005 for 78% of the galaxies in the sample compared to 68% for ML.
The rate of outliers (dz/(1+z)>0.02) is 14% for MCPL and 22% for ML. chi^2
values for ML solutions are found to correlate with the SNR of the spectra, but
not with redshift accuracy. By contrast, the peak value of the normalised
combined PL (gamma) is found to provide a good indication on the reliability of
the MCPL solution for individual sources. The accuracy and reliability of the
redshifts depends strongly on the MIR SED. Sources with significant polycyclic
aromatic hydrocarbon emission obtain much better results compared to sources
dominated by AGN continuum. Nevertheless, for a given gamma the frequency of
accurate solutions and outliers is largely independent on their SED type. This
reliability indicator for MCPL solutions allows to select subsamples with
highly reliable redshifts. In particular, a gamma>0.15 threshold retains 79% of
the sources with dz/(1+z)<0.005 while reducing the outlier rate to 3.8%
(abridged).Comment: 23 pages, 12 figures, 5 tables. Accepted for publication in MNRA
Automated measurement of redshift from mid-infrared low resolution spectroscopy
We present a new SED-fitting based routine for redshift determination that is
optimised for mid-infrared (MIR) low-resolution spectroscopy. Its flexible
template scaling increases the sensitivity to slope changes and small scale
features in the spectrum, while a new selection algorithm called Maximum
Combined Pseudo-Likelihood (MCPL) provides increased accuracy and a lower
number of outliers compared to the standard maximum-likelihood (ML) approach.
Unlike ML, MCPL searches for local (instead of absolute) maxima of a
'pseudo-likelihood' (PL) function, and combines results obtained for all the
templates in the library to weed out spurious redshift solutions. The
capabilities of MCPL are demonstrated by comparing its results to those of
regular ML and to the optical spectroscopic redshifts of a sample of 491
Spitzer/IRS spectra from sources at 0<z<3.7. MCPL achieves a redshift accuracy
dz/(1+z)<0.005 for 78% of the galaxies in the sample compared to 68% for ML.
The rate of outliers (dz/(1+z)>0.02) is 14% for MCPL and 22% for ML. chi^2
values for ML solutions are found to correlate with the SNR of the spectra, but
not with redshift accuracy. By contrast, the peak value of the normalised
combined PL (gamma) is found to provide a good indication on the reliability of
the MCPL solution for individual sources. The accuracy and reliability of the
redshifts depends strongly on the MIR SED. Sources with significant polycyclic
aromatic hydrocarbon emission obtain much better results compared to sources
dominated by AGN continuum. Nevertheless, for a given gamma the frequency of
accurate solutions and outliers is largely independent on their SED type. This
reliability indicator for MCPL solutions allows to select subsamples with
highly reliable redshifts. In particular, a gamma>0.15 threshold retains 79% of
the sources with dz/(1+z)<0.005 while reducing the outlier rate to 3.8%
(abridged).Comment: 23 pages, 12 figures, 5 tables. Accepted for publication in MNRA
Geriatric Oral Health and Its Impact on Eating
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111258/1/j.1532-5415.1996.tb06419.x.pd
Probing radio source environments via HI and OH absorption
We present the results of HI and OH absorption measurements towards a sample
of radio sources using the Arecibo 305-m telescope and the GMRT. In total, 27
radio sources were searched for associated 21-cm HI absorption. One totally new
HI absorption system was detected against the radio galaxy 3C258, while five
previously known HI absorption systems, and one galaxy detected in emission,
were studied with improved frequency resolution and/or sensitivity. Our sample
included 17 GPS and CSS objects, 4 of which exhibit HI absorption. This
detection rate of ~25% compares with a value of ~40% by Vermeulen et al. for
similar sources. We detected neither OH emission nor absorption towards any of
the sources that were observed at Arecibo, and estimate a limit on the
abundance ratio of N(HI)/N(OH)>4x10^6 for 3C258. We have combined our results
with those from other available HI searches to compile a heterogeneous sample
of 96 radio sources consisting of 27 GPS, 35 CSS, 13 flat spectrum and 21 large
sources. The HI absorption detection rate is highest (~45%) for the GPS sources
and least for the large sources. We find HI column density to be anticorrelated
with source size, as reported earlier by Pihlstr\"om et al. The HI column
density shows no significant dependence on either redshift or luminosity, which
are themselves strongly correlated. These results suggest that the environments
of radio sources on GPS/CSS scales are similar at different redshifts. Further,
in accordance with the unification scheme, the GPS/CSS galaxies have an HI
detection rate of ~40% which is significantly higher than the detection rate
(~20%) towards the GPS/CSS quasars. Also, the principal (strongest) absorption
component detected towards GPS sources appears blue-shifted in ~65% of the
cases, in agreement with the growing evidence for jet-cloud interactions.Comment: Abridged abstract, 22 pages, 21 figures, moderately revised, accepted
for publication in MNRA
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Demonstration of enhanced warhead performance with more powerful explosives
Enhanced warhead performance has been demonstrated for several warhead configurations loaded with more powerful explosives. This paper presents experimental results from several warheads loaded with one of the new more powerful explosives, LX-19. The LX-19 formulation is a volume analog to LX-14 (HMX/Estane) that consists of 95.8 wt.% epsilon CL-20 formulated with 4.2 wt.% Estane binder. The LX-19 formulation, characterization, and evaluation efforts presseted in this paper are the result of several studies that have been ongoing since 1991. The warhead configurations that have been tested include a trumpet lined shaped charge, a hemispherical lined shaped cahrge, an EFP charge, and a fragmentation warhead, Performation improvements have been demonstrated with all configurations that were tested
What is said or how it is said makes a difference: role of the right fronto-parietal operculum in emotional prosody as revealed by repetitive TMS
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