Search results for "SAMPLE"

CEMS of insulators by use of gas-flow counters

1994

Gas-flow CEMS counters are usually designed in such a manner that the sample to be investigated is inserted into the counter and serves as the backing cathode. If the sample consists of an insulating material, serious problems are expected by charging-up effects similar to those appearing in Maze counters. These problems are discussed in detail. It could be shown by experiments with glass samples that their very low surface conductivity is sufficient to allow a defined operation of such gas-flow CEMS detectors. The electric field strength between the surface of the sample and the anode has to be equal or higher than that between the entrance window and the anode. This can be ensured by an a…

First tests of the applicability of gamma-ray imaging for background discrimination in time-of-flight neutron capture measurements

2015

In this work we explore for the first time the applicability of using $\gamma$-ray imaging in neutron capture measurements to identify and suppress spatially localized background. For this aim, a pinhole gamma camera is assembled, tested and characterized in terms of energy and spatial performance. It consists of a monolithic CeBr$_3$ scintillating crystal coupled to a position-sensitive photomultiplier and readout through an integrated circuit AMIC2GR. The pinhole collimator is a massive carven block of lead. A series of dedicated measurements with calibrated sources and with a neutron beam incident on a $^{197}$Au sample have been carried out at n_TOF, achieving an enhancement of a factor…

The positron distribution in a layered stack sample studied with the use of positron lifetime spectroscopy

2011

Abstract Computer simulation using GEANT4 codes indicates an enhancement of the fraction of implanted positrons stopped in the denser regions of a layered sample. However, positron lifetime measurements performed for layers of pure aluminum, silver and gold foils do not reveal this effect, indicating instead that backscattering plays an important role in determining the positron implantation profile in layered and/or heterogeneous samples.

Simulation studies of the laser ablation ion source at the SHIPTRAP setup

2020

Hyperfine interactions 241(1), 46 (2020). doi:10.1007/s10751-020-01708-0

Measurement of the Lifetime of Neutral Charmed Mesons

1984

Abstract The lifetime of neutral charmed particles photoproduced in emulsion has been measured. The lifetime value presented here was obtained from a sample of 22D 0 mesons, 18 of which have their charmed partner seen in emulsion. The sample is essentially background-free. The result obtained is τ D 0 =(2.11 +1.21 -0.63 )×10 13 s The D 0 mass derived from 8 3C events is m D 0 = 1856 ± 36 MeV/ c 2 .

Measurement of the rate of the decay KL→e+e−γ and observation of a form factor in this decay

1990

Abstract A large sample of Dalitz decays, K L → e + e − γ , has been observed. The branching ratio is Γ(K L →e + e − γ) Γ(K L → all )=(9.2±0.5±0.5)×10 −6 in good agreement with theoretical predictions. We observe an enhancement at high masses in the distribution of the invariant electron-positron pair mass, compared to the distribution expected from QED. This excess is interpreted as being due to virtual mesons contributing to the photon propagator.

NA48/62 latest results

2017

The NA62 experiment at the CERN SPS recorded in 2007 a large sample of K+ ? µ+?µ decays. A peak search in the missing mass spectrum of this decay is performed. In the absence of observed signal, the limits obtained on B(K+ ? µ+?h) and on the mixing matrix element |Uµ 4| are reported. The upgraded NA62 experiment started data taking in 2015. About 5×1011K+ decays have been recorded so far to measure the branching ratio of the K+ ? ?+?? decay. Preliminary results from the K+ ? ?+?? analysis based on about 5% of the 2016 statistics are reported.

A Cautionary Note on Incremental Fit Indices Reported by LISREL

2005

Abstract. Incremental fit indices (IFIs) are regularly used when assessing the fit of structural equation models. IFIs are based on the comparison of the fit of a target model with that of a null model. For maximum-likelihood estimation, IFIs are usually computed by using the χ2 statistics of the maximum-likelihood fitting function (ML-χ2). However, LISREL recently changed the computation of IFIs. Since version 8.52, IFIs reported by LISREL are based on the χ2 statistics of the reweighted least squares fitting function (RLS-χ2). Although both functions lead to the same maximum-likelihood parameter estimates, the two χ2 statistics reach different values. Because these differences are especi…

HUMAN CAPITAL IN GROWTH REGRESSIONS: HOW MUCH DIFFERENCE DOES DATA QUALITY MAKE?.

2000

We construct a revised version of the Barro and Lee (1996) data set for a sample of OECD countries using previously unexploited sources and following a heuristic approach to obtain plausible time profiles for attainment levels by removing sharp breaks in the data that seem to reflect changes in classification criteria. It is then shown that these revised data perform much better than the Barro and Lee (1996) or Nehru et al (1995) series in a number of growth specifications. We interpret these results as an indication that poor data quality may be behind counterintuitive findings in the recent literature on the (lack of) relationship between educational investment and growth. Using our prefe…

2020

This study examined the stability of reading difficulties (RD) from grades 2 to 6 and focused on the effects of measurement error and cut-off selection in the identification of RD and its stability with the use of simulations. It addressed methodological limitations of prior studies by (a) applying a model-based simulation analysis to examine the effects of measurement error and cut-offs in the identification of RD, (b) analyzing a non-English and larger sample, and (c) examining RD in both reading fluency and reading comprehension. Reading fluency and reading comprehension of 1,432 Finnish-speaking children were assessed in grades 2 and 6. In addition to the use of single cut-off points on…