Equivalent detector models for the simulation of efficiency response of an HPGe detector with PENELOPE code

ABSTRACT

In this work, some ‘equivalent’ models for the simulation of efficiency response of a High-Purity Germanium (HPGe) detector, installed inside a ‘low background’ bunker in the Engineering Department of the University of Palermo, were developed. The main feature was to attribute the uncertainties of the model to only one of the parameters, the dead layer of the detector, keeping unchanged the other data provided by the manufacturer. With this technique, using the Monte Carlo PENELOPE code in the 2011 version, the efficiency response was evaluated and compared with the previous one performed with MCNP5 code.

The validation of equivalent models is performed by comparing the simulation results with that of experimental spectrometric measurements of calibrated point sources and characterized volumetric sources such as a Marinelli beaker and an air filter reduced to a ‘packet-sample’.

The use of equivalent models makes the evaluation of efficiency curves with a Monte Carlo code easier and faster, and requires only a few experimental values for validation.     

Halogen bonding: a paradigm in supramolecular chemistry

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Endocrine-disrupting pollutants properties affecting their bioactivity,remediation, and detection

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Halogenation of the N-Terminus Tyrosine 10 Promotes Supramolecular Stabilization of the Amyloid-β Sequence 7–12

Here, we demonstrate that introduction of halogen atoms at the tyrosine 10 phenol ring of the DSGYEV sequence derived from the flexible amyloid-β N-terminus, promotes its self-assembly in the solid state. In particular, we report the crystal structures of two halogen-modified sequences, which we found to be stabilized in the solid state by halogen-mediated interactions. The structural study is corroborated by Non-Covalent Interaction (NCI) analysis. Our results prove that selective halogenation of an amino acid enhances the supramolecular organization of otherwise unstructured biologically-relevant sequences. This method may develop as a general strategy for stabilizing highly polymorphic peptide regions.     

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In this paper we first prove short time existence of a classical solution for the problem which describes the evolution by Gaussian curvature of a strictly convex hypersurface in . Then we give a proof of the existence of a viscosity solution for this problem in such a way as to define a generalized motion existing for each time. Received November 24, 1997     

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