3,809 research outputs found
DESI Commissioning Instrument Metrology
The Dark Energy Spectroscopic Instrument (DESI) is under construction to
measure the expansion history of the Universe using the Baryon Acoustic
Oscillation technique. The spectra of 35 million galaxies and quasars over
14000 sq deg will be measured during the life of the experiment. A new prime
focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber
optic positioners. The fibers in turn feed ten broad-band spectrographs. We
will describe the methods and results for the commissioning instrument
metrology program. The primary goals of this program are to calculate the
transformations and further develop the systems that will place fibers within
5um RMS of the target positions. We will use the commissioning instrument
metrology program to measure the absolute three axis Cartesian coordinates of
the five CCDs and 22 illuminated fiducials on the commissioning instrument
Evaluation of the relationships between computed tomography features, pathological findings, and rrognostic risk assessment in gastrointestinal stromal tumors
Objectives The aim of this study was to correlate computed tomography (CT) findings with pathology in gastrointestinal stromal tumors (GISTs). Methods A retrospective evaluation of CT images of 44 patients with GISTs was performed. Computed tomography findings analyzed were location, size, margins, degree and pattern of contrast enhancement, angiogenesis, necrosis, signs of invasion, peritoneal effusion, peritoneal implants, surface ulceration, and calcifications. Associations between CT features and mitotic rate, Miettinen classes of risk, lesions size, and among CT features were investigated. χ 2 Test and Fisher test were performed. Results Mitotic rate was associated with margins (P = 0.016) and with adjacent organ invasion (P = 0.043). Pattern of contrast enhancement (P = 0.002), angiogenesis (P = 0.006), necrosis (P = 0.006), invasion of adjacent organs (P = 0.011), and margins (P = 0.006) were associated with classes of risk. Several associations (P < 0.05) between lesion size and CT features and among all the investigated CT features were found. Conclusions Computed tomography features could reflect GIST biology being associated with the mitotic rate and with classes of risk
Ariel - Volume 12 Number 1
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Les sables de Fontainebleau: a natural quartz reference sample and its characterisation
Fundamental studies on luminescence production
in natural quartz require samples
which can be studied by groups of laboratories
using complementary methods. In the framework
of a European collaboration studying
quartz luminescence, a sample originating
from the Fontainebleau Sandstone Formation
in France was selected for characterisation
and distribution to establish a starting point
for interlaboratory work. Here we report on
the preparation and characterisation work
undertaken before distribution with the aim
of ensuring that each laboratory received
comparable material. Material was purified to
enrich the quartz concentration, followed by
mineralogical screening by SEM and ICP-MS
analyses. Luminescence screening measurements
were undertaken at a single laboratory
(SUERC) to verify the suitability of the sample
for use within the study, and to establish the
level of homogeneity of subsamples prepared
for distribution. The sample underwent minimal
non-chemical pre-treatment by multiple
cycles of magnetic separation and annealing.
SEM analysis showed that the sample
consists mainly of SiO2. The luminescence
characterisation confirmed a dose sensitivity
of ca. 22,000–160,000 cts K−1 Gy−1 per 260–
290 grains for the 110â—¦C UV TL peak, well
developed low (here: 100–300◦C) temperature
(pre-dose) TL signals and high OSL sensitivities.
The grain to grain OSL response varies by
more than one order of magnitude. No significant
IRSL signal was observed. In summary,
the results from luminescence characterisation
confirm the suitability of the sample for the
luminescence experiments envisaged and have
established a basis for comparability in studies
conducted by a network of laboratories
Doppler-aware Odometry from FMCW Scanning Radar
This work explores Doppler information from a millimetre-Wave (mm-W)
Frequency-Modulated Continuous-Wave (FMCW) scanning radar to make odometry
estimation more robust and accurate. Firstly, doppler information is added to
the scan masking process to enhance correlative scan matching. Secondly, we
train a Neural Network (NN) for regressing forward velocity directly from a
single radar scan; we fuse this estimate with the correlative scan matching
estimate and show improved robustness to bad estimates caused by challenging
environment geometries, e.g. narrow tunnels. We test our method with a novel
custom dataset which is released with this work at
https://ori.ox.ac.uk/publications/datasets.Comment: Accepted to ITSC 202
Doppler-aware odometry from FMCW scanning radar
This work explores Doppler information from a millimetre-Wave (mm-W) Frequency-Modulated Continuous-Wave (FMCW) scanning radar to make odometry estimation more robust and accurate. Firstly, doppler information is added to the scan masking process to enhance correlative scan matching. Secondly, we train a Neural Network (NN) for regressing forward velocity directly from a single radar scan; we fuse this estimate with the correlative scan matching estimate and show improved robustness to bad estimates caused by challenging environment geometries, e.g. narrow tunnels. We test our method with a novel custom dataset which is released with this work at https://ori.ox.ac.uk/publications/datasets
Malignant Perivascular Epithelioid Cell Neoplasm (PEComa) of the Pelvis: A Case Report
AbstractPerivascular epithelioid cell neoplasms (PEComa) are rare mesenchymal tumors that can occur in any part of the body and have unpredictable pathological behavior. They are usually benign, but may be malignant. We present a case of malignant PEComa of the pelvic retroperitoneum treated with radical surgery
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Metallization and Modification of Low-k Dielectric Materials
Aluminum was deposited onto both Teflon AF and Parylene AF surfaces by chemical vapor deposition of trimethylaluminum. This work shows that similar thin film (100 Angstroms) aluminum oxide adlayers form on both polymers at the low temperature dosing conditions used in the studies. Upon anneal to room temperature and above, defluorination of the polymer surfaces increased and resulted in fluorinated aluminum oxide adlayers; the adlayers were thermally stable to the highest temperatures tested (600 K). Angle-resolved spectra showed higher levels of fluorination toward the polymer/adlayer interface region. Copper films were also deposited at low temperature onto Teflon AF using a copper hexafluoroacetylacetonate-cyclooctadiene precursor. Annealing up to 600 K resulted in the loss of precursor ligands and a shift to metallic copper. As with aluminum adlayers, some polymer defluorination and resulting metal (copper) fluoride was detected. Parylene AF and polystyrene films surfaces were modified by directly dosing with water vapor passed across a hot tungsten filament. Oxygen incorporation into polystyrene occurred exclusively at aromatic carbon sites, whereas oxygen incorporation into parylene occurred in both aromatic and aliphatic sites. Oxygen x-ray photoelectron spectra of the modified polymers were comparable, indicating that similar reactions occurred. The surface oxygenation of parylene allowed enhanced reactivity toward aluminum chemical vapor deposition. Silicon-carbon (Si-Cx) films were formed by electron beam bombardment of trimethylvinylsilane films which were adsorbed onto metal substrates at low temperatures in ultra-high vacuum. Oxygen was also added to the films by coadsorbing water before electron beam bombardment; the films were stable to more than 700 K, with increasing silicon-oxygen bond formation at elevated temperatures. Copper metal was sputter deposited in small increments onto non-oxygenated films. X-ray photoelectric spectra show three-dimensional copper growth (rather than layer-by-layer growth), indicating only weak interaction between the copper and underlying films. Annealing at elevated temperatures caused coalescence or growth of the copper islands, with spectra indicating metallic copper rather than copper oxide
Masked γ-SSL: learning uncertainty estimation via masked image modeling
This work proposes a semantic segmentation network that produces high-quality uncertainty estimates in a single forward pass. We exploit general representations from foundation models and unlabelled datasets through a Masked Image Modeling (MIM) approach, which is robust to augmentation hyper-parameters and simpler than previous techniques. For neural networks used in safety-critical applications, bias in the training data can lead to errors; therefore it is crucial to understand a network’s limitations at run time and act accordingly. To this end, we test our proposed method on a number of test domains including the SAX Segmentation benchmark, which includes labelled test data from dense urban, rural and off-road driving domains. The proposed method consistently outperforms uncertainty estimation and Out-ofDistribution (OoD) techniques on this difficult benchmark
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