405 research outputs found
Development of the opto-mechanical design for ICE-T
ICE-T (International Concordia Explorer Telescope) is a double 60 cm f/1.1
photometric robotic telescope, on a parallactic mount, which will operate at
Dome C, in the long Antarctic night, aiming to investigate exoplanets and
activity of the hosting stars. Antarctic Plateau site is well known to be one
of the best in the world for observations because of sky transparency in all
wavelengths and low scintillation noise. Due to the extremely harsh
environmental conditions (the lowest average temperature is -80C) the
criteria adopted for an optimal design are really challenging. Here we present
the strategies we have adopted so far to fulfill the mechanical and optical
requirements.Comment: 7 pages, 2 figures, contributed talk at 'An astronomical Observatory
at Concordia (Dome C, Antarctica) for the next decade', 11-15 May, Rome
(Italy
High power femtosecond source based on passively mode-locked 1055nm VECSEL and Yb-fibre power amplifier
We report 5 ns pulses at 160 W average power and 910 repetition rate from a passively mode-locked VECSEL source seeding an Yb-doped fibre power amplifier. The amplified pulses were compressed to 291 fs duration
Dynamic depletion in a Bose condensate via a sudden increase of the scattering length
We examine the time-dependent quantum depletion of a trapped Bose condensate
arising from a rapid increase of the scattering length. Our solution indicates
that a significant buildup of incoherent atoms can occur within a
characteristic time short compared with the harmonic trap period. We discuss
how the depletion density and the characteristic time depend on the physical
parameters of the condensate
Radiological prediction of positive circumferential resection margin in oesophageal cancer
Purpose
A positive circumferential resection margin (CRM) is regarded as a poor prognostic indicator in oesophageal cancer (OC) but its prediction can be challenging. MRI is used to predict a threatened CRM in rectal cancer but is not commonly performed in OC unlike PET/CT, which is now routinely used. Therefore, this study assessed the additional predictive value of PET-defined tumour variables compared with EUS and CT T-stage. The prognostic significance of CRM status was also assessed.
Materials and Methods
This retrospective study included 117 consecutive patients [median age 64.0 (range 24–78), 102 males, 110 adenocarcinomas, 6 squamous cell carcinoma (SCC), 1 neuro-endocrine] treated between 1st March 2012 and 31st July 2015. A binary logistic regression model tested 5 staging variables; EUS T-stage (≤T2 vs ≥ T3), CT T-stage (≤T2 vs ≥ T3), PET metabolic tumour length (MTL), PET metabolic tumour width (MTW) and the maximum standardised uptake value (SUVmax).
Results
The CRM was positive in 43.6%. Sixty-seven (57.3%) patients received neo-adjuvant chemotherapy (NACT), 31 patients (26.5%) underwent surgery alone and 19 patients (16.2%) had neo-adjuvant chemo-radiotherapy (NACRT). Median overall survival (OS) was 36.0 months (95% confidence interval (CI) 24.1–47.9) and the 2-year OS was 55.4%. A binary logistic regression model showed EUS ≥ T3 tumours were independently and significantly more likely to have a positive CRM than EUS ≤ T2 tumours (HR 5.188, 95% CI 1.265–21.273, p = 0.022). CT T-stage, PET MTL, PET MTW and SUVmax were not significantly associated with CRM status (p = 0.783, 0.852, 0.605 and 0.413, respectively). There was a significant difference in OS between CRM positive and negative groups (X2 4.920, df 1, p = 0.027).
Conclusion
Advanced EUS T-stage is associated with a positive CRM, but PET-defined tumour variables are unlikely to provide additional predictive information. This study demonstrates the continued benefit of EUS as part of a multi-modality OC staging pathway
Critical scaling of the a.c. conductivity for a superconductor above Tc
We consider the effects of critical superconducting fluctuations on the
scaling of the linear a.c. conductivity, \sigma(\omega), of a bulk
superconductor slightly above Tc in zero applied magnetic field. The dynamic
renormalization- group method is applied to the relaxational time-dependent
Ginzburg-Landau model of superconductivity, with \sigma(\omega) calculated via
the Kubo formula to O(\epsilon^{2}) in the \epsilon = 4 - d expansion. The
critical dynamics are governed by the relaxational XY-model
renormalization-group fixed point. The scaling hypothesis \sigma(\omega) \sim
\xi^{2-d+z} S(\omega \xi^{z}) proposed by Fisher, Fisher and Huse is explicitly
verified, with the dynamic exponent z \approx 2.015, the value expected for the
d=3 relaxational XY-model. The universal scaling function S(y) is computed and
shown to deviate only slightly from its Gaussian form, calculated earlier. The
present theory is compared with experimental measurements of the a.c.
conductivity of YBCO near Tc, and the implications of this theory for such
experiments is discussed.Comment: 16 pages, submitted to Phys. Rev.
A first estimate of triply heavy baryon masses from the pNRQCD perturbative static potential
Within pNRQCD we compute the masses of spin-averaged triply heavy baryons
using the now-available NNLO pNRQCD potentials and three-body variational
approach. We focus in particular on the role of the purely three-body
interaction in perturbation theory. This we find to be reasonably small and of
the order 25 MeV Our prediction for the Omega_ccc baryon mass is 4900(250) in
keeping with other approaches. We propose to search for this hitherto
unobserved state at B factories by examining the end point of the recoil
spectrum against triple charm.Comment: 18 figures, 21 page
Spontaneous chiral symmetry breaking in the linked cluster expansion
We investigate dynamical chiral symmetry breaking in the Coulomb gauge
Hamiltonian QCD. Within the framework of the linked cluster expansion we extend
the BCS ansatz for the vacuum and include correlation beyond the
quark-antiquark paring. In particular we study the effects of the three-body
correlations involving quark-antiquark and transverse gluons. The high momentum
behavior of the resulting gap equation is discussed and numerical computation
of the chiral symmetry breaking is presented.Comment: 13 pages, 9 figure
Teacher Ratings of Children's Behavior Problems and Functional Impairment Across Gender and Ethnicity:Construct Equivalence of the Strengths and Difficulties Questionnaire
The present study examined construct equivalence of the teacher Strengths and Difficulties Questionnaire and compared mean scores in an ethnically diverse sample of children living in the Netherlands. Elementary schoolteachers completed the Strengths and Difficulties Questionnaire for 2,185 children aged 6 to 10 years of the four largest ethnic groups in the Netherlands, namely native Dutch (n = 684) and Moroccan (n = 702), Turkish (n = 434), and Surinamese (n = 365) immigrant children. Multigroup confirmatory factor analysis suggested the factor structure of the Strengths and Difficulties Questionnaire to be invariant across children's ethnicity and gender. Additionally, the factor structure appeared to be similar for Dutch and Surinamese teachers. However, mean scores on emotional problems, hyperactivity, conduct problems, prosocial behavior, and impairment varied significantly according to ethnicity and gender. Mean scores on peer problems differed significantly for boys and girls, but not across ethnicity. Whether mean differences reflect a method bias or actual differences in classroom behaviors is discussed and needs further research
The Infrared Behaviour of the Pure Yang-Mills Green Functions
We review the infrared properties of the pure Yang-Mills correlators and
discuss recent results concerning the two classes of low-momentum solutions for
them reported in literature; i.e. decoupling and scaling solutions. We will
mainly focuss on the Landau gauge and pay special attention to the results
inferred from the analysis of the Dyson-Schwinger equations of the theory and
from "{\it quenched}" lattice QCD. The results obtained from properly
interplaying both approaches are strongly emphasized.Comment: Final version to be published in FBS (54 pgs., 11 figs., 4 tabs
Review article: MHD wave propagation near coronal null points of magnetic fields
We present a comprehensive review of MHD wave behaviour in the neighbourhood
of coronal null points: locations where the magnetic field, and hence the local
Alfven speed, is zero. The behaviour of all three MHD wave modes, i.e. the
Alfven wave and the fast and slow magnetoacoustic waves, has been investigated
in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null
points, for a variety of assumptions, configurations and geometries. In
general, it is found that the fast magnetoacoustic wave behaviour is dictated
by the Alfven-speed profile. In a plasma, the fast wave is focused
towards the null point by a refraction effect and all the wave energy, and thus
current density, accumulates close to the null point. Thus, null points will be
locations for preferential heating by fast waves. Independently, the Alfven
wave is found to propagate along magnetic fieldlines and is confined to the
fieldlines it is generated on. As the wave approaches the null point, it
spreads out due to the diverging fieldlines. Eventually, the Alfven wave
accumulates along the separatrices (in 2D) or along the spine or fan-plane (in
3D). Hence, Alfven wave energy will be preferentially dissipated at these
locations. It is clear that the magnetic field plays a fundamental role in the
propagation and properties of MHD waves in the neighbourhood of coronal null
points. This topic is a fundamental plasma process and results so far have also
lead to critical insights into reconnection, mode-coupling, quasi-periodic
pulsations and phase-mixing.Comment: 34 pages, 5 figures, invited review in Space Science Reviews => Note
this is a 2011 paper, not a 2010 pape
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