910 research outputs found
The Drinfel'd twisted XYZ model
We construct a factorizing Drinfel'd twist for a face type model equivalent
to the XYZ model. Completely symmetric expressions for the operators of the
monodromy matrix are obtained.Comment: 15 pages, 4 figures, second preprint no. added, reference [14] added,
typos correcte
Symmetric informationally complete positive operator valued measure and probability representation of quantum mechanics
Symmetric informationally complete positive operator valued measures
(SIC-POVMs) are studied within the framework of the probability representation
of quantum mechanics. A SIC-POVM is shown to be a special case of the
probability representation. The problem of SIC-POVM existence is formulated in
terms of symbols of operators associated with a star-product quantization
scheme. We show that SIC-POVMs (if they do exist) must obey general rules of
the star product, and, starting from this fact, we derive new relations on
SIC-projectors. The case of qubits is considered in detail, in particular, the
relation between the SIC probability representation and other probability
representations is established, the connection with mutually unbiased bases is
discussed, and comments to the Lie algebraic structure of SIC-POVMs are
presented.Comment: 22 pages, 1 figure, LaTeX, partially presented at the Workshop
"Nonlinearity and Coherence in Classical and Quantum Systems" held at the
University "Federico II" in Naples, Italy on December 4, 2009 in honor of
Prof. Margarita A. Man'ko in connection with her 70th birthday, minor
misprints are corrected in the second versio
A Modality-Adaptive Method for Segmenting Brain Tumors and Organs-at-Risk in Radiation Therapy Planning
In this paper we present a method for simultaneously segmenting brain tumors
and an extensive set of organs-at-risk for radiation therapy planning of
glioblastomas. The method combines a contrast-adaptive generative model for
whole-brain segmentation with a new spatial regularization model of tumor shape
using convolutional restricted Boltzmann machines. We demonstrate
experimentally that the method is able to adapt to image acquisitions that
differ substantially from any available training data, ensuring its
applicability across treatment sites; that its tumor segmentation accuracy is
comparable to that of the current state of the art; and that it captures most
organs-at-risk sufficiently well for radiation therapy planning purposes. The
proposed method may be a valuable step towards automating the delineation of
brain tumors and organs-at-risk in glioblastoma patients undergoing radiation
therapy.Comment: corrected one referenc
A modality-adaptive method for segmenting brain tumors and organs-at-risk in radiation therapy planning
In this paper we present a method for simultaneously segmenting brain tumors and an extensive set of
organs-at-risk for radiation therapy planning of glioblastomas. The method combines a contrast-adaptive
generative model for whole-brain segmentation with a new spatial regularization model of tumor shape
using convolutional restricted Boltzmann machines. We demonstrate experimentally that the method is
able to adapt to image acquisitions that differ substantially from any available training data, ensuring its
applicability across treatment sites; that its tumor segmentation accuracy is comparable to that of the
current state of the art; and that it captures most organs-at-risk sufficiently well for radiation therapy
planning purposes. The proposed method may be a valuable step towards automating the delineation of
brain tumors and organs-at-risk in glioblastoma patients undergoing radiation therapy
A modality-adaptive method for segmenting brain tumors and organs-at-risk in radiation therapy planning
In this paper we present a method for simultaneously segmenting brain tumors and an extensive set of organs-at-risk for radiation therapy planning of glioblastomas. The method combines a contrast-adaptive generative model for whole-brain segmentation with a new spatial regularization model of tumor shape using convolutional restricted Boltzmann machines. We demonstrate experimentally that the method is able to adapt to image acquisitions that differ substantially from any available training data, ensuring its applicability across treatment sites; that its tumor segmentation accuracy is comparable to that of the current state of the art; and that it captures most organs-at-risk sufficiently well for radiation therapy planning purposes. The proposed method may be a valuable step towards automating the delineation of brain tumors and organs-at-risk in glioblastoma patients undergoing radiation therapy
Pharmacological characterisation of anti-inflammatory compounds in acute and chronic mouse models of cigarette smoke-induced inflammation
<p>Abstract</p> <p>Background</p> <p>Candidate compounds being developed to treat chronic obstructive pulmonary disease are typically assessed using either acute or chronic mouse smoking models; however, in both systems compounds have almost always been administered prophylactically. Our aim was to determine whether the prophylactic effects of reference anti-inflammatory compounds in acute mouse smoking models reflected their therapeutic effects in (more clinically relevant) chronic systems.</p> <p>Methods</p> <p>To do this, we started by examining the type of inflammatory cell infiltrate which occurred after acute (3 days) or chronic (12 weeks) cigarette smoke exposure (CSE) using female, C57BL/6 mice (n = 7-10). To compare the effects of anti-inflammatory compounds in these models, mice were exposed to either 3 days of CSE concomitant with compound dosing or 14 weeks of CSE with dosing beginning after week 12. Budesonide (1 mg kg<sup>-1</sup>; i.n., q.d.), roflumilast (3 mg kg<sup>-1</sup>; p.o., q.d.) and fluvastatin (2 mg kg<sup>-1</sup>; p.o., b.i.d.) were dosed 1 h before (and 5 h after for fluvastatin) CSE. These dose levels were selected because they have previously been shown to be efficacious in mouse models of lung inflammation. Bronchoalveolar lavage fluid (BALF) leukocyte number was the primary endpoint in both models as this is also a primary endpoint in early clinical studies.</p> <p>Results</p> <p>To start, we confirmed that the inflammatory phenotypes were different after acute (3 days) versus chronic (12 weeks) CSE. The inflammation in the acute systems was predominantly neutrophilic, while in the more chronic CSE systems BALF neutrophils (PMNs), macrophage and lymphocyte numbers were all increased (p < 0.05). In the acute model, both roflumilast and fluvastatin reduced BALF PMNs (p < 0.01) after 3 days of CSE, while budesonide had no effect on BALF PMNs. In the chronic model, therapeutically administered fluvastatin reduced the numbers of PMNs and macrophages in the BALF (p ≤ 0.05), while budesonide had no effect on PMN or macrophage numbers, but did reduce BALF lymphocytes (p < 0.01). Roflumilast's inhibitory effects on inflammatory cell infiltrate were not statistically significant.</p> <p>Conclusions</p> <p>These results demonstrate that the acute, prophylactic systems can be used to identify compounds with therapeutic potential, but may not predict a compound's efficacy in chronic smoke exposure models.</p
The GAPS Programme at TNG : XLVII. A conundrum resolved: HIP 66074b/Gaia-3b characterised as a massive giant planet on a quasi-face-on and extremely elongated orbit
The nearby mid-K dwarf HIP 66074 was recently identified as host to a candidate super-Jupiter companion on a similar to 300 day, almost edge-on, orbit, based on Gaia Data Release 3 (DR3) astrometry. Initial attempts at confirming the planetary nature of the signal based on publicly available radial-velocity (RV) observations uncovered an intriguing conundrum: the inferred RV semi-amplitude appears to be a factor of 15 smaller than the one predicted based on the Gaia solution (corresponding to a 7-M-Jup companion on a close to edge-on orbit). We present the results of intensive RV monitoring of HIP 66074 with the HARPS-N spectrograph. We detected the companion at the Gaia period, but with an extremely eccentric orbit (e = 0:948 +/- 0:004), a semi-amplitude K = 93.9(-7.0)(+9.4) m s(-1), and a minimum mass mb sin i(b) = 0.79 +/- 0.05 M-Jup. We used detailed simulations of Gaia astrometry with the DR3 time-span to show that the conundrum can be fully resolved by taking into account the combination of the initially sub-optimal RV sampling and systematic biases in the Gaia astrometric solution, which include an underestimation of the eccentricity and incorrect identification of orbital inclination, which has turned out to correspond to a close to face-on configuration (i less than or similar to 13 degrees). With an estimated mass in the approximate range of 3-7 M-Jup, we find that HIP 66074b (equivalent to Gaia-3b) is the first exoplanet candidate astrometrically detected by Gaia to be successfully confirmed based on RV follow-up observations
The GAPS Programme at TNG: XXVII. Reassessment of a young planetary system with HARPS-N: Is the hot Jupiter V830 Tau b really there?
Detecting and characterising exoworlds around very young stars (age10 Myr)
are key aspects of exoplanet demographic studies, especially for understanding
the mechanisms and timescales of planet formation and migration. However,
detection using the radial velocity method alone can be very challenging, since
the amplitude of the signals due to magnetic activity of such stars can be
orders of magnitude larger than those induced even by massive planets. We
observed the very young (2 Myr) and very active star V830 Tau with the
HARPS-N spectrograph to independently confirm and characterise the previously
reported hot Jupiter V830 Tau b ( m/s; ; d). Due to the observed
1 km/s radial velocity scatter clearly attributable to V830 Tau's
magnetic activity, we analysed radial velocities extracted with different
pipelines and modelled them using several state-of-the-art tools. We devised
injection-recovery simulations to support our results and characterise our
detection limits. The analysis of the radial velocities was aided by using
simultaneous photometric and spectroscopic diagnostics. Despite the high
quality of our HARPS-N data and the diversity of tests we performed, we could
not detect the planet V830 Tau b in our data and confirm its existence. Our
simulations show that a statistically-significant detection of the claimed
planetary Doppler signal is very challenging. Much as it is important to
continue Doppler searches for planets around young stars, utmost care must be
taken in the attempt to overcome the technical difficulties to be faced in
order to achieve their detection and characterisation. This point must be kept
in mind when assessing their occurrence rate, formation mechanisms and
migration pathways, especially without evidence of their existence from
photometric transits
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
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