Search results for " NEUTRON"
showing 10 items of 618 documents
Optical Properties of Natural and Synthetic Minerals
2015
The results of investigation of optical absorption and photoluminescence (PL) of topaz, beryl and yttrium aluminium garnet crystals doped with different concentrations of transition ions exposed to fast neutron irradiation and electron irradiation are presented. We suppose that irradiation leads to the formation of two types of complex centers: "Me2+-F+ (or F) centre" and complex centers, which consist of a cation vacancy and an impurity (iron, manganese and chromium) ion. Exchange interaction between radiation defects and impurity ions during neutron or electron irradiation gives rise to appearance of additional absorption and luminescence band broadening in investigated crystals.
Thermal Properties, Raman Spectroscopy and Tem Images of Neutron-Bombarded Graphite
2013
Neutron-irradiated graphite to a total dose of 3.6 × 1016 n cm−2 was studied by DSC, Raman spectroscopy and transmission electron microscopy (TEM). The Wigner energy of neutron-irradiated graphite was 9.5 J/g as measured by DSC; it was released with an exothermal peak at 220°C. The Raman spectroscopy has confirmed the expected effect caused by neutron irradiation of the graphite substrate. The TEM imaging has shown that neutron-irradiated graphite can be effectively exfoliated by sonication in comparison to pristine graphite, which under similar conditions does not exfoliate at all. The interstitial Frenkel defects in neutron-irradiated graphite are intercalated between the graphene layers …
Neutron flux and gamma dose measurement in the BNCT irradiation facility at the TRIGA reactor of the University of Pavia
2018
Abstract University of Pavia is equipped with a TRIGA Mark II research nuclear reactor, operating at a maximum steady state power of 250 kW. It has been used for many years to support Boron Neutron Capture Therapy (BNCT) research. An irradiation facility was constructed inside the thermal column of the reactor to produce a sufficient thermal neutron flux with low epithermal and fast neutron components, and low gamma dose. In this irradiation position, the liver of two patients affected by hepatic metastases from colon carcinoma were irradiated after borated drug administration. The facility is currently used for cell cultures and small animal irradiation. Measurements campaigns have been ca…
A measurement of the neutron to 199Hg magnetic moment ratio
2014
The neutron gyromagnetic ratio has been measured relative to that of the 199Hg atom with an uncertainty of 0.8 ppm. We employed an apparatus where ultracold neutrons and mercury atoms are stored in the same volume and report the result γn/γHg=3.8424574(30).
Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the University of Mainz
2010
To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma fi eld. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron fl ux measurements using gold foil activation and pin-diodes . Material and methods . When L- α -alanine is irradiated with ionizing …
EPR DOSIMETRY IN A MIXED NEUTRON AND GAMMA RADIATION FIELD
2004
Suitability of Electron Paramagnetic Resonance (EPR) spectroscopy for criticality dosimetry was evaluated for tooth enamel, mannose and alanine pellets during the 'international intercomparison of criticality dosimetry techniques' at the SILENE reactor held in Valduc in June 2002, France. These three materials were irradiated in neutron and gamma-ray fields of various relative intensities and spectral distributions in order to evaluate their neutron sensitivity. The neutron response was found to be around 10% for tooth enamel, 45% for mannose and between 40 and 90% for alanine pellets according their type. According to the IAEA recommendations on the early estimate of criticality accident a…
closo-borane conjugated regulatory peptides retain high biological affinity: synthesis of closo-borane conjugated Tyr(3)-octreotate derivatives for B…
2008
Despite the improvements in cancer therapy during the past years, high-grade gliomas and many other types of cancer are still extremely resistant to current forms of therapy. Boron neutron capture therapy (BNCT) provides a promising way to destroy cancer cells without damaging healthy tissue. However, BNCT in practice is still limited due to the lack of boron-containing compounds that selectively deliver boron to cancer cells. Since many neuroendocrine tumors show an overexpression of the somatostatin receptor, it was our aim to synthesize compounds that contain a large number of boron atoms and still show high affinity toward this transmembrane receptor. The synthetic peptide Tyr (3)-octre…
Receptor-mediated uptake of boron-rich neuropeptide y analogues for boron neutron capture therapy.
2014
Peptidic ligands selectively targeting distinct G protein-coupled receptors that are highly expressed in tumor tissue represent a promising approach in drug delivery. Receptor-preferring analogues of neuropeptide Y (NPY) bind and activate the human Y1 receptor subtype (hY1 receptor), which is found in 90% of breast cancer tissue and in all breast-cancer-derived metastases. Herein, novel highly boron-loaded Y1 -receptor-preferring peptide analogues are described as smart shuttle systems for carbaboranes as (10) B-containing moieties. Various positions in the peptide were screened for their susceptibility to carbaborane modification, and the most promising positions were chosen to create a mu…
Growth of beryllium oxide nano-structures during thermal treatment of neutron irradiated beryllium
2015
Beryllium oxide nano-structures grown during high temperature oxidation of neutron irradiated beryllium has been investigated. Oxidation of non - irradiated and neutron irradiated beryllium was performed in differential thermal analyzer in an atmosphere of air and its mixture with helium at temperatures up to 1050°C. Structure of beryllium and its oxide was studied by the means of scanning electron microscopy. The growth of beryllium oxide nano-structures – “labyrinth type” layers and nano-rods on the inner surfaces of neutron irradiated beryllium were observed by means of Scanning Electron Microscopy. The size of the rods was 10-100 nm in diameter and up to few micrometers in length. There…
Dynamics of supercooled confined water measured by deep inelastic neutron scattering
2017
In this paper, we present the results of deep inelastic neutron scattering (DINS) measurements on supercooled water confined within the pores (average pore diameter ~ 20 Ã ) of a disordered hydrophilic silica matrix obtained through hydrolysis and polycondensation of the alkoxide precursor Tetra-Methyl-Ortho-Silicate via the sol-gel method. Experiments were performed at two temperatures (250 K and 210 K, i.e., before and after the putative liquidâliquid transition of supercooled confined water) on a âwetâ sample with hydration h ~ 40% w/w, which is high enough to have water-filled pores but low enough to avoid water crystallization. A virtually âdryâ sample at h ~ 7% was also inve…