155 research outputs found
Modern Instrumental Limits of Identification of Ignitable Liquids in Forensic Fire Debris Analysis
Forensic fire debris analysis is an important part of fire investigation, and gas chromatography–
mass spectrometry (GC-MS) is the accepted standard for detection of ignitable liquids in fire debris.
While GC-MS is the dominant technique, comprehensive two-dimensional gas chromatography–mass
spectrometry (GC GC-MS) is gaining popularity. Despite the broad use of these techniques, their
sensitivities are poorly characterized for petroleum-based ignitable liquids. Accordingly, we explored
the limit of identification (LOI) using the protocols currently applied in accredited forensic labs for
two 75% evaporated gasolines and a 25% evaporated diesel as both neat samples and in the presence
of interfering pyrolysate typical of fire debris. GC-MSD (mass selective detector (MS)), GC-TOF
(time-of-flight (MS)), and GC GC-TOF were evaluated under matched conditions to determine
the volume of ignitable liquid required on-column for correct identification by three experienced
forensic examiners performing chromatographic interpretation in accordance with ASTM E1618-14.
GC-MSD provided LOIs of ~0.6 pL on-column for both neat gasolines, and ~12.5 pL on-column
for neat diesel. In the presence of pyrolysate, the gasoline LOIs increased to ~6.2 pL on-column,
while diesel could not be correctly identified at the concentrations tested. For the neat dilutions,
GC-TOF generally provided 2 better sensitivity over GC-MSD, while GC GC-TOF generally
resulted in 10 better sensitivity over GC-MSD. In the presence of pyrolysate, GC-TOF was generally
equivalent to GC-MSD, while GC GC-TOF continued to show 10 greater sensitivity relative
to GC-MSD. Our findings demonstrate the superior sensitivity of GC GC-TOF and provide an
important approach for interlaboratory benchmarking of modern instrumental performance in fire
debris analysis
CO2/pH-responsive particles with built-in fluorescence read-out
yesA novel fluorescent monomer was synthesized to probe the state of CO2-responsive cross-linked polymeric particles. The fluorescent emission of this aminobromomaleimide-bearing monomer, being sensitive to protic environments, can provide information on the core hydrophilicity of the particles and therefore indicates the swollen state and size of the particles. The particles’ core, synthesized from DEAEMA (N,N-diethylaminoethyl methacrylate), is responsive to CO2 through protonation of the tertiary amines of DEAEMA. The response is reversible and the fluorescence emission can be recovered by simply bubbling nitrogen into the particle solution. Alternate purges of CO2 and N2 into the particles’ solution allow several ON/OFF fluorescence emission cycles and simultaneous particle swelling/shrinking cycles.British Petroleum Company (BP), Engineering and Physical Sciences Research Council (EPSRC
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International films and international markets: the globalisation of Hollywood entertainment, c.1921-1951
The international appeal of Hollywood films through the twentieth century has been a subject of interest to economic and film historians alike. This paper employs some of the methods of the economic historian to evaluate key arguments within the film history literature explaining the global success of American films. Through careful analysis of both existing and newly constructed data sets, the paper examines the extent to which Hollywood's foreign earnings were affected by: film production costs; the extent of global distribution networks; and also the international orientation of the films themselves. The paper finds that these factors influenced foreign earnings in quite distinct ways, and that their relative importance changed over time. The evidence presented here suggests a degree of interaction between the production and distribution arms of the major US film companies in their pursuit of foreign markets that would benefit from further archival-based investigation
The stellar halo of the Galaxy
Stellar halos may hold some of the best preserved fossils of the formation
history of galaxies. They are a natural product of the merging processes that
probably take place during the assembly of a galaxy, and hence may well be the
most ubiquitous component of galaxies, independently of their Hubble type. This
review focuses on our current understanding of the spatial structure, the
kinematics and chemistry of halo stars in the Milky Way. In recent years, we
have experienced a change in paradigm thanks to the discovery of large amounts
of substructure, especially in the outer halo. I discuss the implications of
the currently available observational constraints and fold them into several
possible formation scenarios. Unraveling the formation of the Galactic halo
will be possible in the near future through a combination of large wide field
photometric and spectroscopic surveys, and especially in the era of Gaia.Comment: 46 pages, 16 figures. References updated and some minor changes.
Full-resolution version available at
http://www.astro.rug.nl/~ahelmi/stellar-halo-review.pd
The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy
As part of the DART project we have used the ESO/2.2m Wide Field Imager in
conjunction with the VLT/FLAMES GIRAFFE spectrograph to study the detailed
properties of the resolved stellar population of the Fornax dwarf spheroidal
galaxy out to and beyond its tidal radius. We re-derived the structural
parameters of the Fornax dwarf spheroidal using our wide field imaging covering
the galaxy out to its tidal radius, and analysed the spatial distribution of
the Fornax stars of different ages as selected from Colour-Magnitude Diagram
analysis. We have obtained accurate velocities and metallicities from spectra
in the CaII triplet wavelength region for 562 Red Giant Branch stars which have
velocities consistent with membership in Fornax dwarf spheroidal. We have found
evidence for the presence of at least three distinct stellar components: a
young population (few 100 Myr old) concentrated in the centre of the galaxy,
visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age
population (2-8 Gyr old); and an ancient population (> 10Gyr),which are
distinguishable from each other kinematically, from the metallicity
distribution and in the spatial distribution of stars found in the
Colour-Magnitude Diagram. From our spectroscopic analysis we find that the
``metal rich'' stars ([Fe/H]> -1.3) show a less extended and more concentrated
spatial distribution, and display a colder kinematics than the ``metal poor''
stars ([Fe/H<-1.3). There is tentative evidence that the ancient stellar
population in the centre of Fornax does not exhibit equilibrium kinematics.
This could be a sign of a relatively recent accretion of external material.Comment: 32 pages, 23 figures. Accepted for publication in A&A. The data table
(Table 4) will be available in electronic form after publication. The full
resolution version can be downloaded from
http://www.astro.rug.nl/~gbattagl/battaglia_fullres.p
Fractures in myelomeningocele
BACKGROUND: In patients with myelomeningocele (MMC), a high number of fractures occur in the paralyzed extremities, affecting mobility and independence. The aims of this retrospective cross-sectional study are to determine the frequency of fractures in our patient cohort and to identify trends and risk factors relevant for such fractures. MATERIALS AND METHODS: Between March 1988 and June 2005, 862 patients with MMC were treated at our hospital. The medical records, surgery reports, and X-rays from these patients were evaluated. RESULTS: During the study period, 11% of the patients (n = 92) suffered one or more fractures. Risk analysis showed that patients with MMC and thoracic-level paralysis had a sixfold higher risk of fracture compared with those with sacral-level paralysis. Femoral-neck z-scores measured by dual-energy X-ray absorptiometry (DEXA) differed significantly according to the level of neurological impairment, with lower z-scores in children with a higher level of lesion. Furthermore, the rate of epiphyseal separation increased noticeably after cast immobilization. Mainly patients who could walk relatively well were affected. CONCLUSIONS: Patients with thoracic-level paralysis represent a group with high fracture risk. According to these results, fracture and epiphyseal injury in patients with MMC should be treated by plaster immobilization. The duration of immobilization should be kept to a minimum (<4 weeks) because of increased risk of secondary fractures. Alternatively, patients with refractures can be treated by surgery, when nonoperative treatment has failed
uvby-\beta photometry of high-velocity and metal-poor stars XI. Ages of halo and old disk stars
New uvby-\beta data are provided for 442 high-velocity and metal-poor stars;
90 of these stars have been observed previously by us, and 352 are new. When
combined with our previous two photometric catalogues, the data base is now
made up of 1533 high-velocity and metal-poor stars, all with uvby-\beta
photometry and complete kinematic data, such as proper motions and radial
velocities taken from the literature. Hipparcos, plus a new photometric
calibration for M_v also based on the Hipparcos parallaxes, provide distances
for nearly all of these stars; our previous photometric calibrations give
values for E(b-y) and [Fe/H]. The [Fe/H],V(rot) diagram allows us to separate
these stars into different Galactic stellar population groups, such as
old-thin-disk, thick-disk, and halo. The X histogram, where X is our
stellar-population discriminator combining V(rot) and [Fe/H], and contour plots
for the [Fe/H],V(rot) diagram both indicate two probable components to the
thick disk. These population groups and Galactic components are studied in the
(b-y)_o,M_v diagram, compared to the isochrones of Bergbusch & VandenBerg
(2001), to derive stellar ages. The two thick-disk groups have the mean
characteristics: ([Fe/H], V(rot), Age, \sigma_W') ~ (-0.7 dex, 120 km/s, 12.5
Gyr, 62.0 km/s), and ~(-0.4, 160, 10.0, 45.8). The seven most metal-poor halo
groups, -2.31 <= [Fe/H] <= -1.31, show a mean age of 13.0 +/-0.2 (mean error)
Gyr, giving a mean difference from the WMAP results for the age of the Universe
of 0.7 +/- 0.3 Gyr. These results for the ages and components of the thick disk
and for the age of the Galactic halo field stars are discussed in terms of
various models and ideas for the formation of galaxies and their stellar
populations.Comment: To be published in A&A, 24 pages with 13 figures. Paper X of series:
astro-ph/040363
Aboveground biomass density models for NASA's Global Ecosystem Dynamics Investigation (GEDI) lidar mission
NASA's Global Ecosystem Dynamics Investigation (GEDI) is collecting spaceborne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDI's footprint-level (similar to 25 m) AGBD (GEDI04_A) product, including a description of the datasets used and the procedure for final model selection. The data used to fit our models are from a compilation of globally distributed spatially and temporally coincident field and airborne lidar datasets, whereby we simulated GEDI-like waveforms from airborne lidar to build a calibration database. We used this database to expand the geographic extent of past waveform lidar studies, and divided the globe into four broad strata by Plant Functional Type (PFT) and six geographic regions. GEDI's waveform-to-biomass models take the form of parametric Ordinary Least Squares (OLS) models with simulated Relative Height (RH) metrics as predictor variables. From an exhaustive set of candidate models, we selected the best input predictor variables, and data transformations for each geographic stratum in the GEDI domain to produce a set of comprehensive predictive footprint-level models. We found that model selection frequently favored combinations of RH metrics at the 98th, 90th, 50th, and 10th height above ground-level percentiles (RH98, RH90, RH50, and RH10, respectively), but that inclusion of lower RH metrics (e.g. RH10) did not markedly improve model performance. Second, forced inclusion of RH98 in all models was important and did not degrade model performance, and the best performing models were parsimonious, typically having only 1-3 predictors. Third, stratification by geographic domain (PFT, geographic region) improved model performance in comparison to global models without stratification. Fourth, for the vast majority of strata, the best performing models were fit using square root transformation of field AGBD and/or height metrics. There was considerable variability in model performance across geographic strata, and areas with sparse training data and/or high AGBD values had the poorest performance. These models are used to produce global predictions of AGBD, but will be improved in the future as more and better training data become available
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