1,711 research outputs found
The GRAAL high resolution BGO calorimeter and its energy calibration and monitoring system
We describe the electromagnetic calorimeter built for the GRAAL apparatus at
the ESRF. Its monitoring system is presented in detail. Results from tests and
the performance obtained during the first GRAAL experiments are given. The
energy calibration accuracy and stability reached is a small fraction of the
intrinsic detector resolution.Comment: 19 pages, 14 figures, submitted to Nuclear Instruments and Method
Linear Ramps of Interaction in the Fermionic Hubbard Model
We study the out of equilibrium dynamics of the Fermionic Hubbard Model
induced by a linear ramp of the repulsive interaction from the metallic
state through the Mott transition. To this extent we use a time dependent
Gutzwiller variational method and complement this analysis with the inclusion
of quantum fluctuations at the leading order, in the framework of a slave
spin theory. We discuss the dynamics during the ramp and the issue of
adiabaticity through the scaling of the excitation energy with the ramp
duration . In addition, we study the dynamics for times scales longer
than the ramp time, when the system is again isolated and the total energy
conserved. We establish the existence of a dynamical phase transition analogous
to the one present in the sudden quench case and discuss its properties as a
function of final interaction and ramp duration. Finally we discuss the role of
quantum fluctuations on the mean field dynamics for both long ramps, where spin
wave theory is sufficient, and for very short ramps, where a self consistent
treatment of quantum fluctuations is required in order to obtain relaxation.Comment: v2: 19 pages, 14 figures, published versio
Planck LFI flight model feed horns
this paper is part of the Prelaunch status LFI papers published on JINST:
http://www.iop.org/EJ/journal/-page=extra.proc5/jinst The Low Frequency
Instrument is optically interfaced with the ESA Planck telescope through 11
corrugated feed horns each connected to the Radiometer Chain Assembly (RCA).
This paper describes the design, the manufacturing and the testing of the
flight model feed horns. They have been designed to optimize the LFI optical
interfaces taking into account the tight mechanical requirements imposed by the
Planck focal plane layout. All the eleven units have been successfully tested
and integrated with the Ortho Mode transducers.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in JINST. IOP Publishing Ltd is not responsible for
any errors or omissions in this version of the manuscript or any version
derived from it. The definitive publisher authenticated version is available
online at 10.1088/1748-0221/4/12/T1200
Planck-LFI radiometers' spectral response
The Low Frequency Instrument (LFI) is an array of pseudo-correlation
radiometers on board the Planck satellite, the ESA mission dedicated to
precision measurements of the Cosmic Microwave Background. The LFI covers three
bands centred at 30, 44 and 70 GHz, with a goal bandwidth of 20% of the central
frequency.
The characterization of the broadband frequency response of each radiometer
is necessary to understand and correct for systematic effects, particularly
those related to foreground residuals and polarization measurements. In this
paper we present the measured band shape of all the LFI channels and discuss
the methods adopted for their estimation. The spectral characterization of each
radiometer was obtained by combining the measured spectral response of
individual units through a dedicated RF model of the LFI receiver scheme.
As a consistency check, we also attempted end-to-end spectral measurements of
the integrated radiometer chain in a cryogenic chamber. However, due to
systematic effects in the measurement setup, only qualitative results were
obtained from these tests. The measured LFI bandpasses exhibit a moderate level
of ripple, compatible with the instrument scientific requirements.Comment: 16 pages, 9 figures, this paper is part of the Prelaunch status LFI
papers published on JINST:
http://www.iop.org/EJ/journal/-page=extra.proc5/jins
Performance of HPV DNA testing in the follow-up after treatment of high-grade cervical lesions, adenocarcinoma in situ (AIS) and microinvasive carcinoma
BACKGROUND: Over the last two decades it has become clear that distinct types of human papillomavirus (HPV), the so-called high-risk types (hrHPV), are the major cause of cervical cancer. The hrHPV-DNA testing has shown excellent performance in several clinical applications from screening to the follow-up of conservatively treated patients. METHODS: We conducted a systematic review of the recent literature on the performance of HPV DNA testing in follow-up after treatment of high-grade cervical lesions, adenocarcinoma in situ, and microinvasive carcinoma compared to Pap smear cytology. RESULTS: Observational studies have demonstrated that the high risk hrHPV-DNA test is significantly more sensitive (95%) compared to follow-up cytology(70%) in detecting post-treatment squamous intraepithelial high-grade lesions. Moreover, in patients treated conservatively for cervical adenocarcinoma in situ, the hrHPV-DNA test is the most significant independent predictor of recurrent disease or progression to invasive cancer, and the combination of viral DNA testing and cytology reaches 90% sensitivity in detecting persistent lesions at the first follow-up visit and 100% at the second follow-up visit. The cause of microinvasive squamous cervical carcinoma is increasingly treated with conservative therapies in order to preserve fertility, and an effective strategy allowing early detection of residual or progressive disease has become more and more important in post-treatment follow-up. Primary results seem to indicate that the median time for viral clearance is relatively longer compared with patients treated for CIN and suggest a prolonged surveillance for these patients. However, the potential clinical value of HPV-DNA testing in this clinical setting needs to be confirmed by further observations. CONCLUSIONS: The excellent sensitivity, negative predictive value, and optimal reproducibility of the hrHPV DNA testing, currently is considered a powerful tool in the clinicians’ hands to better manage post-treatment follow-up either in cervical squamous lesion or in situ adenocarcinoma
Planck-LFI: Design and Performance of the 4 Kelvin Reference Load Unit
The LFI radiometers use a pseudo-correlation design where the signal from the
sky is continuously compared with a stable reference signal, provided by a
cryogenic reference load system. The reference unit is composed by small
pyramidal horns, one for each radiometer, 22 in total, facing small absorbing
targets, made of a commercial resin ECCOSORB CR (TM), cooled to approximately
4.5 K. Horns and targets are separated by a small gap to allow thermal
decoupling. Target and horn design is optimized for each of the LFI bands,
centered at 70, 44 and 30 GHz. Pyramidal horns are either machined inside the
radiometer 20K module or connected via external electro-formed bended
waveguides. The requirement of high stability of the reference signal imposed a
careful design for the radiometric and thermal properties of the loads.
Materials used for the manufacturing have been characterized for thermal, RF
and mechanical properties. We describe in this paper the design and the
performance of the reference system.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in JINST. IOP Publishing Ltd is not responsible for
any errors or omissions in this version of the manuscript or any version
derived from it. The definitive publisher authenticated version is available
online at [10.1088/1748-0221/4/12/T12006]. 14 pages, 34 figure
Internal femoral osteosynthesis after external fixation in multiple-trauma patients
In this study the authors evaluate the results of internal synthesis of femoral fractures in polytraumatised patients initially treated by external fixation (EF). From January 2002 to December 2005, 39 femurs in 37 polytraumatised patients (average age 34.2 years, range 18-44) with closed fractures and an ISS>20 were initially treated with EF. There were three groups: Group A, 13 cases when conversion to internal osteosynthesis occurred after 4-7 days (average 5.6 days); Group B, 11 cases with a 4-6-month interval before internal osteosynthesis, and after investigation using MRI and scintigraphy with labelled leucocytes; Group C, the remaining cases treated definitively with EF. Time of healing, lower limb function, time of return to previous activities and short and long-term complications were evaluated at the follow-up. The average time of follow-up was 23 months. In Group A the time of bone healing was 123 days; there were no events of embolism but one case of pseudoarthrosis and one case of instrument failure. In Group B the time of bone healing was 274 days, with one case of pseudoarthrosis and one case of deep infection. In Group C the average healing time was 193 days, with 3 cases of screw (half-pin) osteolysis. Functional recovery was delayed by the presence of other fractures. EF is a simple, quick and safe procedure to stabilise fractures in polytraumatised patients. According to damage control orthopaedic (DCO) concepts, it is possible to replace EF with internal synthesis after an interval as this reduces the risks of internal osteosynthesis when performed in the emergency period. EF can also be maintained as definitive treatment but should a change to internal synthesis be needed, it is possible to do it safely after excluding bone infection
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