We report the results of the first major study of applying quantitative fluorescence polymerase chain reaction (QF-PCR) assays for the detection of major chromosome numerical disorders. The QF-PCR ...tests were performed on a total of 247 chorionic villus samples, which were analysed blind, without any knowledge of the results obtained using conventional cytogenetic analysis. The aims of this investigation were to evaluate the detection power and accuracy of this approach by testing a large number of fetal samples and to assess the diagnostic value of each of the chromosome specific small tandem repeat (STR) markers used. In addition, we introduced three more markers specific for chromosomes 13, 18, and X to allow an accurate analysis of samples homozygous for a particular STR. Fluorescent labelled primers were used to amplify 12 STRs specific for chromosomes 21, 18, 13, X, and the amylogenin-like DNA sequence AMXY, expressed on the X and Y chromosomes. In this blind study of 247 fetal samples, 222 were correctly diagnosed by QF-PCR as normal for each of the five chromosomes investigated; 20 were diagnosed by QF-PCR as trisomic for chromosomes 21, 18, or 13, in agreement with the cytogenetic tests. Only one false negative result was observed, probably owing to the mishandling of the sample, which had been transferred through three laboratories before being analysed by QF-PCR. The 247 samples also included four cases of mosaicism or translocation; one case of mosaic trisomy 21 was detected by QF-PCR and the other cases were not identified by QF-PCR. The results of this investigation provide clear evidence that the QF-PCR assays are powerful adjuncts to conventional cytogenetic techniques and can be applied for the rapid and accurate prenatal diagnosis of the most frequent aneuploidies.
Improving the knowledge of seismogenic faults requires the integration of geological, seismological, and geophysical information. Among several analyses, the definition of earthquake focal mechanisms ...plays an essential role in providing information about the geometry of individual faults and the stress regime acting in a region. Fault plane solutions can be retrieved by several techniques operating in specific magnitude ranges, both in the time and frequency domain and using different data.
The front-end (Level-0) electronics interface module for the LHCb Ring Imaging Čherenkov (RICH) detectors is described. This module integrates the novel hybrid photon detectors (HPDs), which ...instrument the RICH detectors, to the LHCb trigger, data acquisition (DAQ) and control systems. The system operates at 40MHz with a first-level trigger rate of 1MHz. The module design is presented and results are given for both laboratory and beam tests.
Amplitude models are constructed to describe the resonance structure of Formula omitted and Formula omitted decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the ...LHCb experiment, corresponding to an integrated luminosity of 3.0 Formula omitted. The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes Formula omitted and Formula omitted being prominent in Formula omitted and Formula omitted, respectively. Precise measurements of the lineshape parameters and couplings of the Formula omitted, Formula omitted and Formula omitted resonances are made, and a quasi model-independent study of the Formula omitted resonance is performed. The coherence factor of the decays is calculated from the amplitude models to be Formula omitted, which is consistent with direct measurements. These models will be useful in future measurements of the unitary-triangle angle Formula omitted and studies of charm mixing and Formula omitted violation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search for the decay Formula omitted is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of Formula omitted, collected by the LHCb experiment ...at centre-of-mass energies of 7 and 8 Formula omitted. The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of Formula omitted at Formula omitted confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Performance of the LHCb RICH photodetectors in a charged particle beam Adinolfi, M.; Aglieri Rinella, G.; Albrecht, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2007, Letnik:
574, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The Ring Imaging Cherenkov detectors of LHCb will use pixel Hybrid Photon Detectors to measure the spatial position of Cherenkov photons. The first six pre-production photon detectors have been ...tested in a beam, together with prototypes of the on-detector electronics. The tests were performed at CERN using
10
GeV
/
c
pions together with an
N
2
gas radiator as a source of Cherenkov light. With 1.1
m of radiator, around 10 photoelectrons were detected per track. The single-photon Cherenkov angle resolution was measured to be
1.66
±
0.03
mrad
, which is dominated by the pixelisation of the photon detector in the test-beam set-up. Both numbers agree with expectations.
Using decays to Formula omitted-meson pairs, the inclusive production of charmonium states in Formula omitted-hadron decays is studied with pp collision data corresponding to an integrated luminosity ...of Formula omitted, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by Formula omitted the inclusive branching fraction of a Formula omitted hadron to a charmonium state C that decays into a pair of Formula omitted mesons, ratios Formula omitted are determined as Formula omitted, Formula omitted, Formula omitted, Formula omitted, Formula omitted and Formula omitted. Here and below the first uncertainties are statistical and the second systematic. Upper limits at 90% confidence level for the inclusive production of X(3872), X(3915) and Formula omitted states are obtained as Formula omitted, Formula omitted and Formula omitted. Differential cross-sections as a function of transverse momentum are measured for the Formula omitted and Formula omitted states. The branching fraction of the decay Formula omitted is measured for the first time, Formula omitted. Here the third uncertainty is due to the branching fraction of the decay Formula omitted, which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse Formula omitted polarization is observed. The measurements allow the determination of the ratio of the branching fractions for the Formula omitted decays to Formula omitted and Formula omitted as Formula omitted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Several investigations are in progress with the aim of performing prenatal diagnosis of inherited disorders by noninvasive or minimally invasive techniques. The most important approaches are based on ...the detection of fetal nucleated cells in maternal blood, the analysis of fetal DNA present in maternal plasma, and the identification and isolation of fetal trophoblastic cellular elements shed into the uterine cavity and the endocervical canal. In this review, we discuss the methods that have been employed for the collection of the transcervical samples at an early stage of gestation and the techniques used for the identification of fetal cells. We also report the results of using endocervical cells for the detection of fetal chromosomal disorders by fluorescent in-situ hybridization and for performing prenatal diagnosis of fetal Rh(D) phenotypes. Recent investigations have also shown that--after the isolation of trophoblastic cells from maternal contaminants by micromanipulation--transcervical samples can be employed for the prenatal diagnosis of single gene defects, such as those causing thalassemia and sickle cell anemia. Although the present results are promising, further investigations are required to demonstrate the feasibility of performing accurate diagnosis of fetal diseases by this minimally invasive approach in all transcervical samples retrieved at an early stage of gestation.
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