| 1. |
- El-Seedi, Hesham R, et al.
(författare)
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Prehistoric peyote use : alkaloid analysis and radiocarbon dating of archaeological specimens of Lophophora from Texas
- 2005
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Ingår i: Journal of Ethnopharmacology. - : Elsevier BV. - 0378-8741 .- 1872-7573. ; 101:1-3, s. 238-242
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Tidskriftsartikel (refereegranskat)abstract
- Two archaeological specimens of peyote buttons, i.e. dried tops of the cactus Lophophora williamsii (Lem.) Coulter, from the collection of the Witte Museum in San Antonio, was subjected to radiocarbon dating and alkaloid analysis. The samples were presumably found in Shumla Cave No. 5 on the Rio Grande, Texas. Radiocarbon dating shows that the calibrated 14C age of the weighted mean of the two individual dated samples corresponds to the calendric time interval 3780-3660 BC (one sigma significance). Alkaloid extraction yielded approximately 2% of alkaloids. Analysis with thin-layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS) led to the identification of mescaline in both samples. No other peyote alkaloids could be identified. The two peyote samples appear to be the oldest plant drug ever to yield a major bioactive compound upon chemical analysis. The identification of mescaline strengthens the evidence that native North Americans recognized the psychotropic properties of peyote as long as 5700 years ago.
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| 2. |
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| 3. |
- Aldahan, Alan, et al.
(författare)
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Antropogenic I-129 in the Baltic Sea
- 2007
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Ingår i: Nuclear Instruments and Methods in Physic research Section B - Beam interactions with materials and atoms. ; B259, s. 491-495
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Tidskriftsartikel (refereegranskat)
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| 4. |
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| 5. |
- Intarasiri, S., et al.
(författare)
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Characterization of the crystalline quality of beta-SiC formed by ion beam synthesis
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 249, s. 851-855
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Tidskriftsartikel (refereegranskat)abstract
- The ion beam synthesis (IBS) technique is applied to form crystalline silicon carbide (SiC) for future optoelectronics applications. Carbon ions at 80 and 40 keV were implanted into (100) high-purity p-type silicon wafers at room temperature and 400 degrees C, respectively, to doses in excess of 10(17) ions/cm(2). Subsequent thermal annealing of the implanted samples was performed in a vacuum furnace at temperatures of 800, 900 and 1000 degrees C, respectively. Elastic recoil detection analysis was used to investigate depth distributions of the implanted ions and infrared transmittance (IR) measurement was used to characterize formation of SiC in the implanted Si substrate. Complementary to IR, Raman scattering measurements were also carried out. Levels of the residual damage distribution of the samples annealed at different temperatures were compared with that of the as-implanted one by Rutherford backscattering spectrometry (RBS) in the channeling mode. The results show that C-ion implantation at the elevated temperature, followed by high-temperature annealing, enhances the synthesis of crystalline SiC.
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| 6. |
- Intarasiri, S., et al.
(författare)
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RBS and ERDA determinations of depth distributions of high-dose carbon ions implanted in silicon for silicon-carbide synthesis study
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 249, s. 859-864
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Tidskriftsartikel (refereegranskat)abstract
- For ion beam synthesis of silicon carbide (SiC), a knowledge of the depth distribution of implanted carbon ions in silicon is crucial for successful development. Based on its simplicity and availability, we selected Rutherford backscattering spectrometry (RBS) as an analysis technique for this purpose. A self-developed computer program dedicated to extract depth profiles of lighter impurities in heavier matrix is established. For control, calculated results are compared with an other ion beam analysis (IBA) technique superior for studying lighter impurity in heavier substrate i.e. elastic recoil detection analysis (ERDA). The RBS was performed with a 1.7-MV Tandetron accelerator using He2+ as the probe ions. The ERDA was performed with a 5-MV Pelletron accelerator using I8+ as the probe ions. This work shows that the RBS-extracted data had no significant deviations from those of ERDA and simulations by SRIM2003 and SIMPL computer codes. We also found that annealing at temperatures as high as 1000 degrees C had quite limited effect on the redistribution of carbon in silicon.
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| 7. |
- Large, DJ, et al.
(författare)
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The influence of climate, hydrology and permafrost on Holocene peat accumulation at 3500 m on the eastern Qinghai-Tibetan plateau
- 2009
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 28:27-28, s. 3303-3314
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Tidskriftsartikel (refereegranskat)abstract
- Peatland of the eastern Qinghai–Tibetan Plateau lies at the convergence of the East Asian and Indian monsoon systems in eastern Asia. To understand the evolution of this peatland and its potential to provide new insights into the Holocene evolution of the East Asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near Hongyuan. The age-depth profile was determined using 16 14C-AMS age dates, the peat analysed for a range of environmental variables including carbon, nitrogen and hydrogen concentration, bulk density, δ13C and the associated spring water analysed for hydrogen and oxygen isotopes. The age-depth profile of the recovered peat sequence covers the period from 9.6 to 0.3 kyr BP and is linear indicating that the conditions governing productivity and decay varied little over the Holocene. Using changes in carbon density, organic carbon content and its δ13C, cold dry periods of permafrost characterised by low density and impeded surface drainage were identified. The low δ18O and δD values of the spring water emanating around the peat deposit, down to −13.8 and −102‰ (VSMOW), respectively, with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day. In view of the current annual mean air temperature of 1 °C this suggests conditions in the past have been conducive to permafrost. Inferred periods of permafrost correspond to independently recognised cold periods in other Holocene records from across China at 8.6, 8.2–7.8, 5.6–4.2, 3.1 and 1.8–1.5 kyr BP. The transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at Hongyuan are of longer duration than equivalent cold dry periods over central and eastern China. Light–dark banding peat on a scale of 15–30 years from 9.6 to 5.5 kyr BP may indicate a strong influence of decadal oscillations possibly the Pacific Decadal Oscillation and a potential link between near simultaneous climatic changes in the northwest Pacific, ENSO, movement of the Intertropical Convergence Zone and the East Asian Monsoon.
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| 8. |
- Mörner, Nils-Axel, et al.
(författare)
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Heimdall's stones at Vitemölla in Sweden and the chronology and stratigraphy of the surroundings
- 2009
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 91A:3, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- Heimdall's Stones at Vitemolla is an archaeological monument of stones arranged in circles and where sightlines can be identified of the sunrise and sunset at winter and summer solstices and spring and autumn equinoxes. Therefore, this stone monument is likely to have served as an archaeoastronomic observatory. It is founded in a fossil land surface now covered by half a metre of eolian sand. In order to date this sand drift, sediment coring was performed in the nearby Sandefloen bog. Seven levels were subjected to AMS C14 dating. The first sand drift, correlated with the sand drift covering Heimdall's Stones, was dated at 500-600 cal. bc. Consequently, the observatory has to date back to the Bronze Age, fitting well with its Sun cult and with the rock carvings recorded on the individual stones. At the seashore 500 m east of the observatory and the bog, we were able to reconstruct the sea-level changes. In conclusion, we combine the recorded sea-level changes with the C14-dated bog stratigraphy and the observed stratigraphy at Heimdall's Stones (covering an area of 500x500 m) into one unified picture. The chronostratigraphic position of Heimdall's Stones agrees well with the dating of the Kivik grave. The Vitemolla area is likely to have been an important cultural centre in the Bronze Age.
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