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  • 1
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    Online Resource
    C-14 analysis of groundwater down to the millilitre level
    Elsevier BV ; 2013
    In:  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Vol. 294 ( 2013-01), p. 573-576
    Details
    In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier BV, Vol. 294 ( 2013-01), p. 573-576
    Type of Medium: Online Resource
    ISSN: 0168-583X
    URL: Article
    DOI: 10.1016/j.nimb.2012.03.038
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2013
    detail.hit.zdb_id: 1466524-4
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  • 2
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    GAS ION SOURCE PERFORMANCE OF THE ENVIRONMICADAS AT HEKAL LABORATORY, DEBRECEN, HUNGARY
    Cambridge University Press (CUP) ; 2021
    In:  Radiocarbon Vol. 63, No. 2 ( 2021-04), p. 499-511
    Details
    In: Radiocarbon, Cambridge University Press (CUP), Vol. 63, No. 2 ( 2021-04), p. 499-511
    Abstract: A coupled accelerator mass spectrometer–gas interface system has been successfully operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary, since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1, IAEA-C2, and IAEA-C7 standards. The performance of our instrumentation shows good agreement with other published gas-interface system data and also shows a quite good agreement with the nominal value of international standard samples. There is a measurable but quite small memory effect after modern samples, but this does not significantly affect the final results. Typical ion currents at the low energy side were between 10–15 µA with a 5% CO 2 in He mixing ratio. The relative errors average ±6% for samples greater than or equal to 10 µgC sample with mean count rates of 300 counts per microgram C for OxII. The blank is comparable with other systems, which is 0.0050 ± 0.0018 F 14 C or 34,000–47,000 yr BP, which allows for the routine measurement of both of small environmental and archeological samples.
    Type of Medium: Online Resource
    ISSN: 0033-8222 , 1945-5755
    URL: Article
    DOI: 10.1017/RDC.2020.109
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2028560-7
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  • 3
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    Isotope Analytical Characterization of Carbon-Based Nanocomposites
    Cambridge University Press (CUP) ; 2018
    In:  Radiocarbon Vol. 60, No. 4 ( 2018-08), p. 1101-1114
    Details
    In: Radiocarbon, Cambridge University Press (CUP), Vol. 60, No. 4 ( 2018-08), p. 1101-1114
    Abstract: Carbon-based nanomaterials of different dimensions (1–3D, tubes, bundles, films, papers and sponges, graphene sheets) have been created and their characteristic properties have been discussed intensively in the literature. Due to their unique advantageous, tunable properties these materials became promising candidates in new generations of applications in many research laboratories and, recently, in industries as well. Protein-based bio-nanocomposites are referred to as materials of the future, which may serve as conceptual revolution in the development of integrated optical devices, e.g. optical switches, microimaging systems, sensors, telecommunication technologies or energy harvesting and biosensor applications. In our experiments, we designed various carbon-based nanomaterials either doped or not doped with nitrogen or sulfur during catalytic chemical vapor deposition synthesis. Radio- and isotope analytical studies have shown that the used starting materials, precursors and carriers have a strong influence on the geometry and physico-/chemical characteristics of the carbon nanotubes produced. After determining the 14 C isotope constitution 53 m/m% balance was found in the reaction center protein/carbon nanotubes complex in a sensitive way that was prepared in our laboratory. The result is essential in determining the yield of conversion of light energy to chemical potential in this bio-hybrid system.
    Type of Medium: Online Resource
    ISSN: 0033-8222 , 1945-5755
    URL: Article
    DOI: 10.1017/RDC.2018.63
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 2028560-7
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  • 4
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    More Rapid 14 C Excursions in the Tree-Ring Record: A Record of Different Kind of Solar Activity at About 800 BC?
    Cambridge University Press (CUP) ; 2018
    In:  Radiocarbon Vol. 60, No. 4 ( 2018-08), p. 1237-1248
    Details
    In: Radiocarbon, Cambridge University Press (CUP), Vol. 60, No. 4 ( 2018-08), p. 1237-1248
    Abstract: Two radiocarbon ( 14 C) excursions are caused by an increase of incoming cosmic rays on a short time scale found in the Late Holocene (AD 774–775 and AD 993–994), which are widely explained as due to extreme solar proton events (SPE). In addition, a larger event has also been reported at 5480 BC (Miyake et al. 2017a), which is attributed to a special mode of a grand solar minimum, as well as another at 660 BC (Park et al. 2017). Clearly, other events must exist, but could have different causes. In order to detect more such possible events, we have identified periods when the 14 C increase rate is rapid and large in the international radiocarbon calibration (IntCal) data (Reimer et al. 2013). In this paper, we follow on from previous studies and identify a possible excursion starting at 814–813 BC, which may be connected to the beginning of a grand solar minimum associated with the beginning of the Hallstatt period, which is characterized by relatively constant 14 C ages in the period from 800–400 BC. We compare results of annual 14 C measurements from tree rings of sequoia (California) and cedar (Japan), and compare these results to other identified excursions, as well as geomagnetic data. We note that the structure of the increase from 813 BC is similar to the increase at 5480 BC, suggesting a related origin. We also assess whether there are different kinds of events that may be observed and may be consistent with different types of solar phenomena, or other explanations.
    Type of Medium: Online Resource
    ISSN: 0033-8222 , 1945-5755
    URL: Article
    DOI: 10.1017/RDC.2018.53
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 2028560-7
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  • 5
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    Sealed Tube Combustion Method with MnO 2 for AMS 14 C Measurement
    Cambridge University Press (CUP) ; 2018
    In:  Radiocarbon Vol. 60, No. 5 ( 2018-10), p. 1347-1355
    Details
    In: Radiocarbon, Cambridge University Press (CUP), Vol. 60, No. 5 ( 2018-10), p. 1347-1355
    Abstract: An effective sealed tube combustion method was designed with an MnO 2 oxidant for accelerator mass spectrometry radiocarbon (AMS 14 C) measurements. Different types of materials (oxalic acid, cellulose, sucrose, wood, collagen, graphite, and humic acid) were used to test the method. A normal borosilicate glass tube was used instead of quartz and the combustion was done at 550ºC. The yield of the combustion is above 98% even in the case of the less combustible material such as graphite. The MnO 2 reagent does not introduce detectable carbon contamination. The typical background is 0.29±0.20 pMC in the case of 200 µg carbon, measured as solid graphite target. With direct measurement of the CO 2 by gas ion source AMS, the method is applicable up to 50 µg of carbon with an acceptable (~1 pMC) 14 C background. A new type of tube cracker was developed for a quick chipless method of tube cracking and sample changing. In this way, the gas handling process takes only 5–6 min/sample.
    Type of Medium: Online Resource
    ISSN: 0033-8222 , 1945-5755
    URL: Article
    DOI: 10.1017/RDC.2018.110
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 2028560-7
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  • 6
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    Radiocarbon Map of a Bomb-Peak Labeled Human Eye
    Cambridge University Press (CUP) ; 2020
    In:  Radiocarbon Vol. 62, No. 1 ( 2020-02), p. 189-196
    Details
    In: Radiocarbon, Cambridge University Press (CUP), Vol. 62, No. 1 ( 2020-02), p. 189-196
    Abstract: The 14 C/ 12 C ratio of living organisms is largely determined by the 14 C/ 12 C ratio of consumed diet as well as by the atmospheric 14 C concentration together with the body’s metabolic processes. The measured 14 C content of living matter compared to the atmospheric radiocarbon level can provide invaluable information about developmental processes. Our aim was to determine the 14 C content of ten different tissues of the human eye using the 14 C bomb-pulse dating signature. The 14 C content of the atmosphere, so called 14 C “bomb-pulse” has labeled humanity offering an opportunity to determine these special formation, turnover and substitution courses in biology. The results allowed us to construct a 14 C map of the bomb-peak labeled human eye. According to the anatomical location of the tissues, an unexpected picture emerged as in moving from the outer parts towards the inner parts of the eye, the 14 C content of each tissue decreased. The data presented here are compatible with the view that the oldest parts of the eye are the sclera, the limbus and the cornea, in this order, and moving further inside, the youngest tissue of the eye is the retina.
    Type of Medium: Online Resource
    ISSN: 0033-8222 , 1945-5755
    URL: Article
    DOI: 10.1017/RDC.2019.78
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2028560-7
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  • 7
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    State and role of water confined in cement and composites modified with metakaolin and additives
    Elsevier BV ; 2023
    In:  Journal of Molecular Liquids Vol. 388 ( 2023-10), p. 122716-
    Details
    In: Journal of Molecular Liquids, Elsevier BV, Vol. 388 ( 2023-10), p. 122716-
    Type of Medium: Online Resource
    ISSN: 0167-7322
    URL: Article
    DOI: 10.1016/j.molliq.2023.122716
    RVK:
    VE 6350
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 1491496-7
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  • 8
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    Real-Time Sensing of Hydrogen Peroxide by ITO/MWCNT/Horseradish Peroxidase Enzyme Electrode
    Hindawi Limited ; 2016
    In:  Journal of Nanomaterials Vol. 2016 ( 2016), p. 1-11
    Details
    In: Journal of Nanomaterials, Hindawi Limited, Vol. 2016 ( 2016), p. 1-11
    Abstract: The accurate and sensitive determination of H 2 O 2 is very important in many cases because it is a product of reactions catalysed by several oxidase enzymes in living cells and it is essential in environmental and pharmaceutical analyses. The fabrication of enzyme protein activity based biosensors is a very promising way for this purpose because the function of biological molecules is very specific, sensitive, and selective. Horseradish peroxidase (HRP) is the most commonly used enzyme for H 2 O 2 detection because it can oxidize hydrogen atoms and, for example, xenobiotics in the presence of H 2 O 2 . In order to define the limit of detection (LOD) of H 2 O 2 we made calibrations with guaiacol and amplex red (AR), which are hydrogen donors of HRP. The accumulation of the reaction products, tetraguaiacol, and resorufin, respectively, then can be easily detected by absorption or emission (fluorescence) spectroscopy. In our experiments an enzyme electrode was fabricated from ITO (indium tin oxide), functionalized multiwalled carbon nanotubes (f-MWCNTs), and HRP. Although the enzyme activity was smaller by about two orders of magnitude when the enzyme was bound to the f-MWCNTs (ca. 10 −2  M H 2 O 2 /(M HRP·sec) compared to ca. 2 M H 2 O 2 /(M HRP·sec) and 5 M H 2 O 2 /(M HRP·sec) with AR and guaiacol in buffer solution), LOD of the H 2 O 2 decomposition was about 6 pM H 2 O 2 /sec and 10 pM H 2 O 2 /sec in the case of AR and guaiacol, respectively.
    Type of Medium: Online Resource
    ISSN: 1687-4110 , 1687-4129
    URL: Article
    DOI: 10.1155/2016/2437873
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2016
    detail.hit.zdb_id: 2229480-6
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  • 9
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    High-Precision Biogenic Fraction Analyses of Liquid Fuels by 14 C AMS at HEKAL
    Cambridge University Press (CUP) ; 2018
    In:  Radiocarbon Vol. 60, No. 5 ( 2018-10), p. 1317-1325
    Details
    In: Radiocarbon, Cambridge University Press (CUP), Vol. 60, No. 5 ( 2018-10), p. 1317-1325
    Abstract: The biocomponent ratio in liquid fuels as well as the usage of renewable resources for fuel consumption in the transport sector needs to be increased as a result of EU directive 2003/30/EC. Based on radiocarbon ( 14 C) measurements, it should be relatively simple and fast to measure the weight percentage of the fossil and biological sources by accelerator mass spectrometry (AMS) as recommended in the ASTM D 6866-12 and EN 16640 standards. In this study, a relatively easy and fast sample preparation and measurement method based on AMS measurements was developed at the Hertelendi Laboratory of Environmental Studies (HEKAL) using reference samples from the Hungarian MOL Nyrt. oil company. Considering the recent EU regulation for mixing rates of liquid fuels in the transport sector (0.7–2% biofuel content) and the projected higher rates (2–10% biofuel content), the method is applicable to determine fatty acid methyl ester (FAME) and/or hydrotreated vegetable oil (HVO) derived proportions of fuel blends with a 1σ uncertainty better than±0.3% m/m.
    Type of Medium: Online Resource
    ISSN: 0033-8222 , 1945-5755
    URL: Article
    DOI: 10.1017/RDC.2018.109
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 2028560-7
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