896 research outputs found
Automated detection of block falls in the north polar region of Mars
We developed a change detection method for the identification of ice block
falls using NASA's HiRISE images of the north polar scarps on Mars. Our method
is based on a Support Vector Machine (SVM), trained using Histograms of
Oriented Gradients (HOG), and on blob detection. The SVM detects potential new
blocks between a set of images; the blob detection, then, confirms the
identification of a block inside the area indicated by the SVM and derives the
shape of the block. The results from the automatic analysis were compared with
block statistics from visual inspection. We tested our method in 6 areas
consisting of 1000x1000 pixels, where several hundreds of blocks were
identified. The results for the given test areas produced a true positive rate
of ~75% for blocks with sizes larger than 0.7 m (i.e., approx. 3 times the
available ground pixel size) and a false discovery rate of ~8.5%. Using blob
detection we also recover the size of each block within 3 pixels of their
actual size
Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms
We have measured the angular distribution of recoiling daughter nuclei
emitted from the Gamow-Teller decay of spin-polarized Rb. The
asymmetry of this distribution vanishes to lowest order in the Standard Model
(SM) in pure Gamow-Teller decays, producing an observable very sensitive to new
interactions. We measure the non-SM contribution to the asymmetry to be
= 0.015 0.029 (stat) 0.019 (syst), consistent with the SM
prediction. We constrain higher-order SM corrections using the measured
momentum dependence of the asymmetry, and their remaining uncertainty dominates
the systematic error. Future progress in determining the weak magnetism term
theoretically or experimentally would reduce the final errors. We describe the
resulting constraints on fundamental 4-Fermi tensor interactions.Comment: 11 pages, 13 figures; v2 published in Phys. Rev. C, with referee
clarifications and figures improved for black-and-whit
A new lateral flow assay to detect sIL-2R during T-cell mediated rejection after kidney transplantation
Kidney is the most frequently transplanted among all solid organs worldwide. Kidney transplant recipients (KTRs) undergo regular follow-up examinations for the early detection of acute rejections. The gold standard for proving a T-cell mediated rejection (TCMR) is a biopsy of the renal graft often occurring as indication biopsy, in parallel to an increased serum creatinine that may indicate deterioration of renal transplant function. The goal of the current work was to establish a lateral flow assay (LFA) for diagnosing acute TCMR to avoid harmful, invasive biopsies. Soluble interleukin-2 (IL-2) receptor (sIl-2R) is a potential biomarker representing the α-subunit of the IL-2 receptor produced by activated T-cells, e.g., after allogen contact. To explore the diagnostic potential of sIL-2R as a biomarker for TCMR and borderline TCMR, plasma and urine samples were collected from three independent KTR cohorts with various distinct histopathological diagnostic findings according to BANFF (containing 112 rsp. 71 rsp. 61 KTRs). Samples were analyzed by a Luminex-based multiplex technique and cut off-ranges were determined. An LFA was established with two specific sIL-2R-antibodies immobilized on a nitrocellulose membrane. A significant association between TCMR, borderline TCMR and sIL-2R in plasma and between TCMR and sIL-2R in urine of KTRs was confirmed using the Mann-Whitney U test. The LFA was tested with sIL-2R-spiked buffer samples establishing a detection limit of 25 pM. The performance of the new LFA was confirmed by analyzing urine samples of the 2nd and 3rd patient cohort with 35 KTRs with biopsy proven TCMRs, 3 KTRs diagnosed with borderline TCMR, 1 mixed AMR/TCMR rsp. AMR/borderline TCMR and 13 control patients with a rejection-free kidney graft proven by protocol biopsies. The new point-of-care assay showed a specificity of 84.6% and sensitivity of 87.5%, and a superior estimated glomerular filtration rate (eGFR) at the time point of biopsy (specificity 30.8%, sensitivity 85%)
Precision mass measurements of magnesium isotopes and implications on the validity of the Isobaric Mass Multiplet Equation
If the mass excess of neutron-deficient nuclei and their neutron-rich mirror
partners are both known, it can be shown that deviations of the Isobaric Mass
Multiplet Equation (IMME) in the form of a cubic term can be probed. Such a
cubic term was probed by using the atomic mass of neutron-rich magnesium
isotopes measured using the TITAN Penning trap and the recently measured
proton-separation energies of Cl and Ar. The atomic mass of
Mg was found to be within 1.6 of the value stated in the Atomic
Mass Evaluation. The atomic masses of Mg were measured to be both
within 1, while being 8 and 34 times more precise, respectively. Using
the Mg mass excess and previous measurements of Cl we uncovered a
cubic coefficient of = 28(7) keV, which is the largest known cubic
coefficient of the IMME. This departure, however, could also be caused by
experimental data with unknown systematic errors. Hence there is a need to
confirm the mass excess of S and the one-neutron separation energy of
Cl, which have both come from a single measurement. Finally, our results
were compared to ab initio calculations from the valence-space in-medium
similarity renormalization group, resulting in a good agreement.Comment: 7 pages, 3 figure
Neural Correlates of Behavioural Olfactory Sensitivity Changes Seasonally in European Starlings
Possibly due to the small size of the olfactory bulb (OB) as compared to rodents, it was generally believed that songbirds lack a well-developed sense of smell. This belief was recently revised by several studies showing that various bird species, including passerines, use olfaction in many respects of life. During courtship and nest building, male European starlings (Sturnus vulgaris) incorporate aromatic herbs that are rich in volatile compounds (e.g., milfoil, Achillea millefolium) into the nests and they use olfactory cues to identify these plants. Interestingly, European starlings show seasonal differences in their ability to respond to odour cues: odour sensitivity peaks during nest-building in the spring, but is almost non-existent during the non-breeding season.This study used repeated in vivo Manganese-enhanced MRI to quantify for the first time possible seasonal changes in the anatomy and activity of the OB in starling brains. We demonstrated that the OB of the starling exhibits a functional seasonal plasticity of certain plant odour specificity and that the OB is only able to detect milfoil odour during the breeding season. Volumetric analysis showed that this seasonal change in activity is not linked to a change in OB volume. By subsequently experimentally elevating testosterone (T) in half of the males during the non-breeding season we showed that the OB volume was increased compared to controls.By investigating the neural substrate of seasonal olfactory sensitivity changes we show that the starlings' OB loses its ability during the non-breeding season to detect a natural odour of a plant preferred as green nest material by male starlings. We found that testosterone, applied during the non-breeding season, does not restore the discriminatory ability of the OB but has an influence on its size
Image equalisation using an external brightness reference
After more than ten years in orbit at Mars, the coverage from the High
Resolution Stereo Camera (HRSC) on the European Space Agency’s Mars Express is
sufficient to begin constructing mosaic products on a global scale. We
describe our systematic processing procedure and, in particular, the technique
used to bring images affected by atmospheric dust into visual consistency with
the mosaic. We outline how the same method is used to produce a relative
colour mosaic which shows local colour differences. We demonstrate the results
and show that the techniques may also be applied to images from other orbital
cameras
A novel transparent charged particle detector for the CPET upgrade at TITAN
The detection of an electron bunch exiting a strong magnetic field can prove
challenging due to the small mass of the electron. If placed too far from a
solenoid's entrance, a detector outside the magnetic field will be too small to
reliably intersect with the exiting electron beam because the light electrons
will follow the diverging magnetic field outside the solenoid. The TITAN group
at TRIUMF in Vancouver, Canada, has made use of advances in the practice and
precision of photochemical machining (PCM) to create a new kind of charge
collecting detector called the "mesh detector." The TITAN mesh detector was
used to solve the problem of trapped electron detection in the new Cooler
PEnning Trap (CPET) currently under development at TITAN. This thin array of
wires etched out of a copper plate is a novel, low profile, charge agnostic
detector that can be made effectively transparent or opaque at the user's
discretion.Comment: 6 Pages. 6 Figures. Submitted to Nuclear Instruments and Methods in
Physics Research Section A: Accelerators, Spectrometers, Detectors and
Associated Equipmen
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