Photosynthetic reaction center/graphene bio-hybrid for low-power optoelectronics

Photosynthetic reaction center (pRC) purified from Rhodobacter sphaeroides 2.4.1 purple bacteria was deposited on a graphene carrier exfoliated from the liquid phase and layered on the surface of SiO2/Si substrate for optoelectronic application. Light-induced changes in the drain-source current vs. gate voltage are demonstrated. Dried photosynthetic reaction centers/graphene composite on SiO2/Si shows a photochemical/-physical activity, as a result of interaction with the current flow in the graphene carrier matrix. The current changes are sensitive to light, due to the contribution from the charge separation in the pRC, and to the applied gate and drain-source voltages

Dating of Total Soil Organic Matter Used in Kurgan Studies

From the 18th International Radiocarbon Conference held in Wellington, New Zealand, September 1-5, 2003.We investigated Csipo-halom, one of the kurgans that served as a burial place in the Hortobágy area of the Hungarian Great Plain. For pedological description and other studies of the protected mound and its surroundings, only a few monitoring drillings were permitted to get soil samples. On the basis of morphological and visual studies, the structure and layers of the mound were reconstructed. The Laboratory of Environmental Studies of the Institute of Nuclear Research at the Hungarian Academy of Sciences (INR/HAS) performed radiocarbon measurements of soil samples, applying a bulk combustion pretreatment method. The measured 14C ages of soil samples from reference points, such as the top layer of the mound, the center of mound body, the base layer of the mound, the near surroundings, and the distant surroundings, are in good agreement with the preliminary archaeological concept for this field and give substantial information about the rate of soil generation processes in this area.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Performance Test of a New Graphite Target Production Facility in ATOMKI

From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.We present our new graphite target production system, developed in the Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), for accelerator mass spectrometry (AMS) radiocarbon dating measurements. The system consists of a gas handling line and a graphite target production system. Results of AMS measurements, stable isotope mass spectrometry measurements, and gravimetric/pressure yield determinations have been used to find the proper conditions for the graphitization process. We have also investigated the 14C contamination and the memory effect of the system during the graphitization processes. This paper covers the details of these experiments and a discussion of the results.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Performance Test of a New Graphite Target Production Facility in ATOMKI

From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.We present our new graphite target production system, developed in the Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), for accelerator mass spectrometry (AMS) radiocarbon dating measurements. The system consists of a gas handling line and a graphite target production system. Results of AMS measurements, stable isotope mass spectrometry measurements, and gravimetric/pressure yield determinations have been used to find the proper conditions for the graphitization process. We have also investigated the 14C contamination and the memory effect of the system during the graphitization processes. This paper covers the details of these experiments and a discussion of the results.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Development of an Automatic Sampling Unit for Measuring Radiocarbon Content of Groundwater

From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.An automatic water sampling unit was developed to monitor the radioactive emission (radiocarbon and other corrosion and fission products) from nuclear facilities into the groundwater. Automatic sampling is based on the principal of ion exchange using built-in resin columns in the submerging samplers. In this way, even the short-term emissions can be detected. According to our experiments, the 14C activity concentrations and the 13C values of the samples made by the ion exchange method are systematically underestimated compared to the real values. The carbonate adsorption feature of the sampling unit was studied under laboratory and field conditions. For this purpose, a test method was developed. The observed sampling efficiencies and additionally some carbon contamination for the sampling method itself have to be taken into consideration when we estimate the amount of 14C contamination introduced into the groundwater from a nuclear facility. Therefore, a correction factor should be made for the 14C anion exchange sampling. With the help of this correction, the results converge to the expected value.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

The Bruneian record of “Borneo Amber”: A regional review of fossil tree resins in the Indo-Australian Archipelago

In this study we intend to provide an overview on fossilized tree resins (amber) commonly found in Southeast Asia, more particularly in the Indo-Australian Archipelago (IAA). These remains are often referred in literature as “Indonesian amber”, “Borneo amber” or simply as “dammar”. They are very common in the region and the Brunei Sultanate is no exception as most of its Neogene sedimentary successions contain amber-rich layers. Although amber is a common fossil in the country and in northern Borneo, to our knowledge it has not been studied in great detail so far. Here we present an account on the “Borneo Ambers” from Brunei, regarding their stratigraphic origin, basic physical properties, their interaction with the biosphere and their botanical origin using Fourier-transform infrared spectroscopy (FTIR). Additionally, a number of ambers and modern tree resins were analysed for their carbon isotope composition and a few were tested with gas chromatography. We discuss the results in a regional and global context, in comparison with available data from the IAA. The ambers come from four different lithostratigraphic units with an age range of 12 to 3 million years (middle Miocene to Pliocene). Recently reworked ambers from the coast, ambers from younger alluvial deposits, and several modern tree resins from Dipterocarpaceae and Araucariaceae (Agathis borneensis) were also included in the study. The >60 FTIR analyses of modern and fossil specimens suggest that all the Brunei ambers were produced by trees of Dipterocarpaceae. There is no indication of Agathis in the fossil record, in agreement with their lower abundance in the forests of Borneo. Modern and fossil dipterocarp resins were found to be different based on the following criteria: (1) Different reactions to solubility, hot needle and UV tests with faster reaction time and less fluorescence for the modern ones; (2) Clear distinction based on certain FTIR absorbance band ratios, mostly by those that represent carboxylic acids and esters (e.g., ~1700 and 1243 cm-1); (3) Modern resin yielded on an average 3‰ lower δ13C values, (4) Gas chromatography data reflect maturation differences among the samples. Although there is some overlap in the chemical results between the two groups, generally all these differences reflect different maturation stages of the resinous material and point towards loss of low δ13C components from the organic structure of the resin. The minor timewise decreasing trend in average δ13C from the late middle Miocene to late Miocene can be explained by (1) gradual changes in local environmental conditions, and/or (2) increased amount of less mature specimens among the younger samples. In contrast, the highest obtained δ13C values were found in the youngest Pliocene ambers. Instead of maturation bias this can be linked to environmental factors such as cooler-drier climate with increased seasonality, probably reflecting the onset of the northern hemisphere glaciation