2,437 research outputs found
Sparse Control of Alignment Models in High Dimension
For high dimensional particle systems, governed by smooth nonlinearities
depending on mutual distances between particles, one can construct
low-dimensional representations of the dynamical system, which allow the
learning of nearly optimal control strategies in high dimension with
overwhelming confidence. In this paper we present an instance of this general
statement tailored to the sparse control of models of consensus emergence in
high dimension, projected to lower dimensions by means of random linear maps.
We show that one can steer, nearly optimally and with high probability, a
high-dimensional alignment model to consensus by acting at each switching time
on one agent of the system only, with a control rule chosen essentially
exclusively according to information gathered from a randomly drawn
low-dimensional representation of the control system.Comment: 39 page
Isotope shift in the Sulfur electron affinity: observation and theory
The electron affinities eA(S) are measured for the two isotopes 32S and 34S
(16752.9753(41) and 16752.9776(85) cm-1, respectively). The isotope shift in
the electron affinity is found to be positive, eA(34S)-eA(32S) = +0.0023(70)
cm-1, but the uncertainty allows for the possibility that it may be either
"normal" (eA(34S) > eA(32S)) or "anomalous" (eA(34S) < eA(32S)). The isotope
shift is estimated theoretically using elaborate correlation models, monitoring
the electron affinity and the mass polarization term expectation value. The
theoretical analysis predicts a very large specific mass shift that
counterbalances the normal mass shift and produces an anomalous isotope shift,
eA(34S)-eA(32S) = - 0.0053(24) cm-1. The observed and theoretical residual
isotope shifts agree with each other within the estimated uncertainties.Comment: 15 pages, 4 figure
The protein translocation systems in plants - composition and variability on the example of Solanum lycopersicum
Background: Protein translocation across membranes is a central process in all cells. In the past decades the molecular composition of the translocation systems in the membranes of the endoplasmic reticulum, peroxisomes, mitochondria and chloroplasts have been established based on the analysis of model organisms. Today, these results have to be transferred to other plant species. We bioinformatically determined the inventory of putative translocation factors in tomato (Solanum lycopersicum) by orthologue search and domain architecture analyses. In addition, we investigated the diversity of such systems by comparing our findings to the model organisms Saccharomyces cerevisiae, Arabidopsis thaliana and 12 other plant species.
Results: The literature search end up in a total of 130 translocation components in yeast and A. thaliana, which are either experimentally confirmed or homologous to experimentally confirmed factors. From our bioinformatic analysis (PGAP and OrthoMCL), we identified (co-)orthologues in plants, which in combination yielded 148 and 143 orthologues in A. thaliana and S. lycopersicum, respectively. Interestingly, we traced 82% overlap in findings from both approaches though we did not find any orthologues for 27% of the factors by either procedure. In turn, 29% of the factors displayed the presence of more than one (co-)orthologue in tomato. Moreover, our analysis revealed that the genomic composition of the translocation machineries in the bryophyte Physcomitrella patens resemble more to higher plants than to single celled green algae. The monocots (Z. mays and O. sativa) follow more or less a similar conservation pattern for encoding the translocon components. In contrast, a diverse pattern was observed in different eudicots.
Conclusions: The orthologue search shows in most cases a clear conservation of components of the translocation pathways/machineries. Only the Get-dependent integration of tail-anchored proteins seems to be distinct. Further, the complexity of the translocation pathway in terms of existing orthologues seems to vary among plant species. This might be the consequence of palaeoploidisation during evolution in plants; lineage specific whole genome duplications in Arabidopsis thaliana and triplications in Solanum lycopersicum
High spectral and spatial resolution X-ray transmission radiography and tomography using a Color X-ray Camera
High resolution X-ray radiography and computed tomography are excellent techniques for non-destructive characterization of an object under investigation at a spatial resolution in the micrometer range. However, as the image contrast depends on both chemical composition and material density, no chemical information is obtained from this data. Furthermore, lab-based measurements are affected by the polychromatic X-ray beam, which results in beam hardening effects. New types of X-ray detectors which provide spectral information on the measured X-ray beam can help to overcome these limitations. In this paper, an energy dispersive CCD detector with high spectral resolution is characterized for use in high resolution radiography and tomography, where a focus is put on the experimental conditions and requirements of both measurement techniques
Micro X-ray Fluorescence Imaging in a Tabletop Full Field-X-ray Fluorescence Instrument and in a Full Field-Particle Induced X-ray Emission End Station
A full field-X-ray camera (FF-XRC) was developed for performing the simultaneous mapping of chemical elements with a high lateral resolution. The device is based on a conventional CCD detector coupled to a straight shaped polycapillary. Samples are illuminated at once with a broad primary beam that can consist of X-rays or charged particles in two different analytical setups. The characteristic photons induced in the samples are guided by the polycapillary to the detector allowing the elemental imaging without the need for scanning. A single photon counting detection operated in a multiframe acquisition mode and a processing algorithm developed for event hitting reconstruction have enabled one to use the CCD as a high energy resolution X-ray detector. A novel software with a graphical user interface (GUI) programmed in Matlab allows full control of the device and the real-time imaging with a region-of-interest (ROI) method. At the end of the measurement, the software produces spectra for each of the pixels in the detector allowing the application of a least-squares fitting with external analytical tools. The FF-XRC is very compact and can be installed in different experimental setups. This work shows the potentialities of the instrument in both a full field-micro X-ray fluorescence (FF-MXRF) tabletop device and in a full field-micro particle induced X-ray emission (FF-MPIXE) end-station operated with an external proton beam. Some examples of applications are given as well
Searching for star-planet magnetic interaction in CoRoT observations
Close-in massive planets interact with their host stars through tidal and
magnetic mechanisms. In this paper, we review circumstantial evidence for
star-planet interaction as revealed by the photospheric magnetic activity in
some of the CoRoT planet-hosting stars, notably CoRoT-2, CoRoT-4, and CoRoT-6.
The phenomena are discussed in the general framework of activity-induced
features in stars accompanied by hot Jupiters. The theoretical mechanisms
proposed to explain the activity enhancements possibly related with hot Jupiter
are also briefly reviewed with an emphasis on the possible effects at
photospheric level. The unique advantages of CoRoT and Kepler observations to
test these models are pointed out.Comment: Invited review paper accepted by Astrophysics and Space Science, 13
pages, 5 figure
Hybrid SPECT/CT for the assessment of a painful hip after uncemented total hip arthroplasty
Background The diagnosis of hip pain after total hip replacement (THR)
represents a highly challenging question that is of increasing concern to
orthopedic surgeons. This retrospective study assesses bone scintigraphy with
Hybrid SPECT/CT for the diagnosis of painful THR in a selected cohort of
patients. Methods Bone SPECT/CT datasets of 23 patients (mean age 68.9 years)
with a painful hip after THR were evaluated. Selection of the patients
required an inconclusive radiograph, normal serum levels of inflammatory
parameters (CRP and ESR) or a negative aspiration of the hip joint prior to
the examination. The standard of reference was established by an
interdisciplinary adjudication-panel using all imaging data and clinical
follow-up data (>12 month). Pathological and physiological uptake patterns
were defined and applied. Results The cause of pain in this study group could
be determined in 18 out of 23 cases. Reasons were aseptic loosening (nâ=â5),
spine-related (nâ=â5), heterotopic ossification (nâ=â5), neuronal (nâ=â1),
septic loosening (nâ=â1) and periprosthetic stress fracture (nâ=â1). In (nâ=
5) cases the cause of hip pain could not be identified. SPECT/CT imaging
correctly identified the cause of pain in (nâ=â13) cases, in which the
integrated CT-information led to the correct diagnosis in (nâ=â4) cases,
mainly through superior anatomic correlation. Loosening was correctly assessed
in all cases with a definite diagnosis. Conclusions SPECT/CT of THA reliably
detects or rules out loosening and provides valuable information about
heterotopic ossifications. Furthermore differential diagnoses may be detected
with a whole-body scan and mechanical or osseous failure is covered by CT-
imaging. SPECT/CT holds great potential for imaging-based assessment of
painful prostheses
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector
The inclusive and dijet production cross-sections have been measured for jets
containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass
energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The
measurements use data corresponding to an integrated luminosity of 34 pb^-1.
The b-jets are identified using either a lifetime-based method, where secondary
decay vertices of b-hadrons in jets are reconstructed using information from
the tracking detectors, or a muon-based method where the presence of a muon is
used to identify semileptonic decays of b-hadrons inside jets. The inclusive
b-jet cross-section is measured as a function of transverse momentum in the
range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet
cross-section is measured as a function of the dijet invariant mass in the
range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets
and the angular variable chi in two dijet mass regions. The results are
compared with next-to-leading-order QCD predictions. Good agreement is observed
between the measured cross-sections and the predictions obtained using POWHEG +
Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet
cross-section. However, it does not reproduce the measured inclusive
cross-section well, particularly for central b-jets with large transverse
momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final
version published in European Physical Journal
Observation of associated near-side and away-side long-range correlations in âsNN=5.02ââTeV proton-lead collisions with the ATLAS detector
Two-particle correlations in relative azimuthal angle (ÎÏ) and pseudorapidity (Îη) are measured in âsNN=5.02ââTeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1ââÎŒb-1 of data as a function of transverse momentum (pT) and the transverse energy (ÎŁETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Îη|<5) ânear-sideâ (ÎÏâŒ0) correlation that grows rapidly with increasing ÎŁETPb. A long-range âaway-sideâ (ÎÏâŒÏ) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ÎŁETPb, is found to match the near-side correlation in magnitude, shape (in Îη and ÎÏ) and ÎŁETPb dependence. The resultant ÎÏ correlation is approximately symmetric about Ï/2, and is consistent with a dominant cosâĄ2ÎÏ modulation for all ÎŁETPb ranges and particle pT
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