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Timeline of Constantin Daniel Negut

2017
Dec
01
Published new article




Article

Radiation processing for cultural heritage preservation – Romanian experience

Published: 01 December 2017 by Walter de Gruyter GmbH in Nukleonika

doi: 10.1515/nuka-2017-0037

Radiation sterilization has been considered a mass decontamination technique for biodegradable cultural heritage (CH) since its widespread application in the medical field. Initial experiments have revealed advantages, for example, efficiency and effectiveness, but also disadvantages, namely “side effects” concerning CH materials. More than 50 years later, the adequacy of ionizing radiation for some CH artefacts is still the subject of discussion. The main reason why is that science and industry are not yet able to provide a more efficient technique for treating mass decontamination. For wooden items, there is general agreement that the irradiation dose required for insect eradication is not damaging, even in the case of polychromed wood. For cellulose pulp (paper), there is a reduction in polymerization degree (DP) at the high doses necessary to stop the attack of fungi, but this should be considered taking into account the purpose of the treatment. Emergency or rescue treatments are necessary to mitigate the consequences of accidents or improper storage conditions. In some cases (archives), the value of written information is greater than the historical value of the paper support. For other materials, namely textiles, leather and parchment, less research has been published on the effect of ionizing radiation treatment. As a general rule, irradiation is not necessary when only a few CH elements are present that are affected by biological contamination since restorers can solve the problem by classical means. The need for radiation treatment arises when large collections (hundreds, thousands or even more elements) are heavily affected by the biological attack. In Romania, the IRASM gamma irradiator of IFIN-HH is receiving an increasing number of requests for CH treatment, mainly due to an intensive research programme concerning this topic and close liaison with CH owners or administrators. Besides reviewing the scientific results obtained in Romania and abroad, this paper presents some examples from experiences in Romania.

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2017
Apr
01
Published new article




Article

Irradiation free radicals in freshwater crayfish Astacus leptodactylus Esch investigated by EPR spectroscopy

Published: 01 April 2017 by Elsevier BV in Radiation Physics and Chemistry

doi: 10.1016/j.radphyschem.2016.12.008

1 Reads | 1 Citations
2017
Jan
01
Published new article






Chapter 19. Qualification and Certification of Ionizing Radiation Facilities

Published: 01 January 2017 by Royal Society of Chemistry (RSC) in Food Chemistry, Function and Analysis

doi: 10.1039/9781788010252-00383

Gamma, e-beam, and X-ray irradiators are equipment that delivers ionizing radiation, and their manufacture and operation are subjected to strict radiation safety regulations. This fact gives a good level of confidence on the reliance of the equipment. However, as for many other radiation processing applications, for food irradiation, it must be confirmed that the radiation processing consistently affords the expected results. This type of proof can be acquired by installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ) certificates. Most radiation processing applications have specific standards, guidelines, or regulations (i.e., radiation sterilization for medical devices for pharmaceuticals) with more or less detailed requirements for qualification. The goal is to prove that the equipment complies with its design specifications (IQ), the equipment performs as intended throughout its normal operation range (OQ), and the output of the radiation processing is consistently (effectively and reproducibly) achieved. This chapter describes the actions required for the qualification of gamma, e-beam, and X-ray irradiators with application to food irradiation and the different types of certifications that allow worldwide operation and aid the acceptance of food irradiation.

2 Reads | 0 Citations
2017
Jan
01
Published new article






ESR Standard Methods for Detection of Irradiated Food

Published: 01 January 2017 by Elsevier BV in Electron Spin Resonance in Food Science

doi: 10.1016/b978-0-12-805428-4.00001-5

This chapter presents electron spin resonance (ESR) spectroscopy as a detection method for irradiated food. In the first part the criteria to be fulfilled by a reliable detection method are summarized. ESR spectroscopy, which satisfies most of the detection criteria, can be used for a wide variety of irradiated foodstuffs and it is standardized for food containing bone, cellulose, and crystalline sugar. Typical spectra for these categories of foodstuffs are presented and discussed. The absence of “specific-to-irradiation” free radicals in the irradiated food or their poor stability can be a serious limitation for the detection of irradiation by ESR spectroscopy. In the last two decades, different improvements in the technique were proposed in order to overcome this problem. The most promising of them are discussed.

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2016
Dec
16
Published new article




Article

Synthesis and Structural Investigation of New Bio-Relevant Complexes of Lanthanides with 5-Hydroxyflavone: DNA Binding a...

Published: 16 December 2016 by MDPI in Molecules

doi: 10.3390/molecules21121737

In the present work, we attempted to develop new metal coordination complexes of the natural flavonoid 5-hydroxyflavone with Sm(III), Eu(III), Gd(III), Tb(III). The resultant hydroxo complexes have been characterized by a variety of spectroscopic techniques, including fluorescence, FT-IR, UV-Vis, EPR and mass spectral studies. The general chemical formula of the complexes is [Ln(C15H9O3)3(OH)2(H2O)x]·nH2O, where Ln is the lanthanide cation and x = 0 for Sm(III), x = 1 for Eu(III), Gd(III), Tb(III) and n = 0 for Sm(III), Gd(III), Tb(III), n = 1 for Eu(III), respectively. The proposed structures of the complexes were optimized by DFT calculations. Theoretical calculations and experimental determinations sustain the proposed structures of the hydroxo complexes, with two molecules of 5-hydroxyflavone acting as monoanionic bidentate chelate ligands. The interaction of the complexes with calf thymus DNA has been explored by fluorescence titration and UV-Vis absorption binding studies, and revealed that the synthesized complexes interact with DNA with binding constants (Kb) ~ 104. Human serum albumin (HSA) and transferrin (Tf) binding studies have also been performed by fluorescence titration techniques (fluorescence quenching studies, synchronous fluorescence spectra). The apparent association constants (Ka) and thermodynamic parameters have been calculated from the fluorescence quenching experiment at 299 K, 308 K, and 318 K. The quenching curves indicate that the complexes bind to HSA with smaller affinity than the ligand, but to Tf with higher binding affinities than the ligand.

0 Reads | 2 Citations
2014
Dec
01
Published new article




Article

Online Tests of an Optical Fiber Long-Period Grating Subjected to Gamma Irradiation

Published: 01 December 2014 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Journal

doi: 10.1109/jphot.2014.2337877

This paper reports the outcomes of the tests that we conducted as online measurements for the evaluation of one optical fiber long-period grating produced by a fusion technique in a single-mode radiation-hardened optical fiber, and subjected to gamma irradiation. During the irradiation, the grating temperature was monitored. Before the irradiation, the temperature sensitivity of the grating was 27.7 pm/°C, while the value of this parameter postirradiation was found to be 29.3 pm/°C. The spectral characteristics of the grating were measured (i) in the laboratory with an ANDO AQ6317C optical spectrum analyzer and (ii) online, for the first time, with a LUNA OBR 4600 backscatter reflectometer, operating in the frequency acquisition mode. Such online measurement enables the study of recovery effects during the irradiation. The wavelength dip of the grating shifted under gamma irradiation, with 16 pm/kGy for the maximum total dose of 45 kGy. At room temperature, the recovery of the irradiation-induced shift of the wavelength dip was almost complete in about 120 h, at a rate of 6.7 pm/h. Postirradiation heating of the sensor produced the reversing of the recovery effect. The investigation indicated that, up to 45 kGy, the grating is more sensitive to radiation than other optical fiber sensors.

1 Reads | 5 Citations
2012
Dec
01
Published new article




Article

Detection of irradiated frog (Limnonectes macrodon) leg bones by multifrequency EPR spectroscopy

Published: 01 December 2012 by Elsevier BV in Food Chemistry

doi: 10.1016/j.foodchem.2012.07.015

The free radicals of irradiated frog Limnonectes macrodon leg bones tissue were studied by electron paramagnetic resonance in both X and Q bands. The kinetic behaviour, the activation energy as well as the thermal stability of the radiation-induced radicals in bone tissue were investigated by means of both isothermal and isochronal annealing. Unirradiated bone tissue displayed the presence of Mn(2+) ions at both frequencies, while a week EPR singlet was evidenced only at 34 GHz. When irradiated with (60)Co gamma ray, the EPR spectra completely changed their patterns and intensity, the overall spectra provin, at both frequencies, to be typical axial ones. The 100°C isothermal annealing studies attested the existence of two different free radical species, significantly more labile than in the case of mammal bone tissues. At the same time, the Arrhenius plot of 15 kGy irradiated bones evidenced two different kinetic regimes with two different activation energies.

0 Reads | 1 Citations
2012
Oct
01
Published new article




Article

Irradiation effects on canvas oil painting: Spectroscopic observations

Published: 01 October 2012 by Elsevier BV in Radiation Physics and Chemistry

doi: 10.1016/j.radphyschem.2012.04.008

0 Reads | 1 Citations
2012
Oct
01
Published new article




Article

Defects induced by gamma irradiation in historical pigments

Published: 01 October 2012 by Elsevier BV in Journal of Cultural Heritage

doi: 10.1016/j.culher.2012.01.002

0 Reads | 4 Citations
2012
Aug
01
Published new article




Article

Establishing the irradiation dose for paper decontamination

Published: 01 August 2012 by Elsevier BV in Radiation Physics and Chemistry

doi: 10.1016/j.radphyschem.2011.11.063

0 Reads | 5 Citations
2012
Feb
01
Published new article




Article

Spectroscopic evaluation of painted layer structural changes induced by gamma radiation in experimental models

Published: 01 February 2012 by Elsevier BV in Radiation Physics and Chemistry

doi: 10.1016/j.radphyschem.2011.09.015

The degradation of cultural heritage objects by insects and microorganisms is an important issue for conservators, art specialists and humankind in general. Gamma irradiation is an efficient method of polychrome wooden artifacts disinfestation. Color changes and other modifications in the physical chemical properties of materials induced by gamma irradiation are feared by cultural heritage responsible committees and they have to be evaluated objectively and precisely. In this paper FTIR and FT-Raman spectroscopy methods were used to investigate the structural changes in some experimental models of tempera paint layers on wood following 11 kGy gamma irradiation at two dose rates. Radiation chemistry depends on the particular pigment, matrix formed by protein, resin (in case of varnished samples) and water presence. For the majority of painted layer in experimental models very small spectral variations were observed. Small changes in the FTIR spectra were observed for the raw sienna experimental model: for the higher dose rate the egg yolk protein oxidation peaks and the CH stretching bands due to lipids degradation products increased. Highlights► Experimental models of tempera paint layers on wood were γ-irradiated at two dose rates. ► Changes induced by γ-irradiation were evaluated by vibrational spectroscopy. ► Minor spectral variations of painted layer were observed. ► Raw sienna FTIR spectra showed little changes of egg yolk and lipids at higher dose rate. ► Gamma irradiation is recommended for disinfection of painted wooden artifacts.

0 Reads | 1 Citations
2011
May
01
Published new article




Article

EPR studies of the free radical kinetics in γ-rays irradiated Pleurotus ostreatus oyster mushrooms

Published: 01 May 2011 by Elsevier BV in Food Research International

doi: 10.1016/j.foodres.2011.02.034

0 Reads | 2 Citations
2010
Dec
01
Published new article




Article

EPR investigation of some desiccated Ascomycota and Basidiomycota gamma-irradiated mushrooms

Published: 01 December 2010 by Elsevier BV in Radiation Physics and Chemistry

doi: 10.1016/j.radphyschem.2010.07.005

0 Reads | 3 Citations
2010
Mar
01
Published new article




Article

Thermal desorption/gas chromatography/mass spectrometry approach for characterization of the volatile fraction from ambe...

Published: 01 March 2010 by Elsevier BV in Journal of Chromatography A

doi: 10.1016/j.chroma.2010.01.075

Research on the chemical composition of fossil resins has evolved during the last decades as a multidisciplinary field and is strongly oriented toward the correlation with their geological and botanical origin. Various extraction procedures and chromatographic techniques have been used together for identifying the volatile compounds contained in the fossil resin matrix. Hyphenation between thermal desorption (TD), gas chromatography (GC) and mass spectrometry detection (MS) has been chosen to investigate the volatile compounds fraction from ambers with a focus on Romanite (Romanian amber) and Baltic amber species. A data analysis procedure was developed for the main purpose of fingerprinting ambers based on the MS identity of the peaks generated by the volatile fraction, together with their relative percentual area within the chromatogram. Chromatographic data analysis was based entirely on Automated Mass Spectral Deconvolution &Identification System (AMDIS) software to produce deconvoluted mass spectra which were used to build-up a mixed mass spectra and relative retention scale library. Multivariate data analysis was further applied on AMDIS results with successful discrimination between Romanite and Baltic ambers. A special trial was conducted to generate pyrolysis "like" macromolecular structure breakdown to volatile compounds by gamma irradiation with a high absorbed dose of 500 kGy. Contrary to our expectations the volatile fraction fingerprints were not modified after irradiation experiments. A complementary non-destructive new approach by ESR spectroscopy was also proposed for discriminating between Romanite and Baltic ambers.

0 Reads | 4 Citations
2007
Jul
05
Published new article






Effects of gamma irradiation on the colour of pigments

Published: 05 July 2007 by SPIE-Intl Soc Optical Eng in Optical Metrology

doi: 10.1117/12.725967

The aim of this paper is to investigate the influence of gamma irradiation process on the colour of painted wood panels. Insects and micro-organisms are frequently identified enemies of cultural objects from museums and archives. Based on its biocide effect, gamma radiation could be used for decontamination and conservation purposes. Important advantages can be mentioned in its favour: no toxic or radioactive residues remained in the treated item; large amount of objects can be treated quickly; excellent reliability; attractive cost. In case of emergency radiation treatment in industrial facilities is probably the only method that can be used. There is also a potential side-effect. Interaction of gamma rays with any substance may change its chemical and physical properties. The change is proportional with the irradiation dose. In the case of paintings, eventually colour changes have to be evaluated. Such an approach actually establishes irradiation treatment limitations. A portable integrating sphere spectrophotometer was used for colour measurements. The results of colour analysis before and after the radiation treatment of the painted wood panels are reported and discussed.

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2004
Feb
01
Published new article




Article

Standardization of 68(Ge+Ga)

Published: 01 February 2004 by Elsevier BV in Applied Radiation and Isotopes

doi: 10.1016/j.apradiso.2003.11.054

The radionuclide 68Ga is mainly a positron emitter (89.2%), with a half-life of 67.7 min. It is used in nuclear medicine, being chemically extracted from the mixture 68(Ge+Ga); its precursor, 68Ge, disintegrates 100% by electron capture, with a half-life of 270.8d (Table of radionuclides, comments and Evaluation). A 4pibeta-gamma coincidence method was used for standardization, with a 4pi proportional beta-detector and a NaI(Tl) gamma detector. Registration of the capture radiations was avoided using foil absorption and a high beta threshold. Using supplementary foils for positron absorption, extrapolation graphs were obtained, with a mean slope of -4.4%. Care was taken to compensate for the loss of 68Ge during the preparation of solid sources for measurement. A combined uncertainty of 1.1% was estimated.

0 Reads | 2 Citations
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