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R Grün

Publications and source records attributed to R Grün.

At least 19 recordsLinked to original sources
PubMed2001

Direct ESR dating of a Pliocene hominin from Swartkrans.

Two fragments of a hominin tooth (Australopithecus robustus) and two bovid teeth from the Hanging Remnant of the Swartkrans Formation were analysed with ESR. Research was complicated by the fact that the samples came from a curated collection and their precise provenance is unknown. The environmental dose rate was reconstructed by a series of in situ gamma spectrometric measurements and elemental analyses of a range of sediment samples. U-series isotopic analyses indicated that each of the teeth had a significantly different uranium uptake history, rendering the assumptive early U-uptake and linear U-uptake models ineffective. ESR and U-series data were combined to calculate open system ages, resulting in a best estimate of 1630+/-160 ka for the Hanging Remnant. An open-system model which provides the maximum age for given U-series and ESR measurements yielded an estimate of about 2100 ka. Two bovid teeth from Member 2, previously estimated to be between 1.0 and 2.0 Ma, yielded age estimates of between about 100 and 200 ka. No known geochemical processes are likely to explain this severe age underestimation. We conclude that these samples are of Middle to Upper Pleistocene age and their presence in Member 2 was either due to reworking or inadequate stratigraphical discrimination of these deposits.

Animals↗
PubMed2001

Border Cave revisited: a revised ESR chronology.

In view of a decade of progress in ESR dating we have revised the ESR chronology of Border Cave. A detailed gamma ray survey in 1994 and newly calculated beta attenuation data led to total dose rate estimations that are between 0 and 30% smaller than previously estimated. Accordingly, the resulting ESR age estimates are between 0 and 30% older. The ESR dates are now in good agreement with independent age estimates, particularly(14)C and amino acid racemization. New ESR dates for the lowermost dated sedimentary layer, 5 WA (white ash), indicate that the sedimentation of the sequence started around 200 ka ago.

Animals↗
PubMed2000

EPR spectrum deconvolution and dose assessment of fossil tooth enamel using maximum likelihood common factor analysis.

In order to determine the components which give rise to the EPR spectrum around g = 2 we have applied Maximum Likelihood Common Factor Analysis (MLCFA) on the EPR spectra of enamel sample 1126 which has previously been analysed by continuous wave and pulsed EPR as well as EPR microscopy. MLCFA yielded agreeing results on three sets of X-band spectra and the following components were identified: an orthorhombic component attributed to CO2-, an axial component (CO3(3-)), as well as four isotropic components, three of which could be attributed to SO2-, a tumbling CO2- and a central line of a dimethyl radical. The X-band results were confirmed by analysis of Q-band spectra where three additional isotropic lines were found, however, these three components could not be attributed to known radicals. The orthorhombic component was used to establish dose response curves for the assessment of the past radiation dose, D(E). The results appear to be more reliable than those based on conventional peak-to-peak EPR intensity measurements or simple Gaussian deconvolution methods.

Animals↗
PubMed1999

Australia's oldest human remains: age of the Lake Mungo 3 skeleton.

We have carried out a comprehensive ESR and U-series dating study on the Lake Mungo 3 (LM3) human skeleton. The isotopic Th/U and Pa/U ratios indicate that some minor uranium mobilization may have occurred in the past. Taking such effects into account, the best age estimate for the human skeleton is obtained through the combination of U-series and ESR analyses yielding 62,000+/-6000 years. This age is in close agreement with OSL age estimates on the sediment into which the skeleton was buried of 61,000+/-2000 years. Furthermore, we obtained a U-series age of 81,000+/-21,000 years for the calcitic matrix that was precipitated on the bones after burial. All age results are considerably older than the previously assumed age of LM3 and demonstrate the necessity for directly dating hominid remains. We conclude that the Lake Mungo 3 burial documents the earliest known human presence on the Australian continent. The age implies that people who were skeletally within the range of the present Australian indigenous population colonized the continent during or before oxygen isotope stage 4 (57,000-71,000 years).

Animals↗
PubMed1998

ESR and U-series analyses of teeth from the palaeoanthropological site of Hexian, Anhui Province, China.

ESR and U-series analyses of teeth from the palaeoanthropological site of Hexian which contained Homo erectus remains, illustrate the limited effectiveness of stand-alone ESR and U-series age estimates on faunal materials. The problem lies in the unknown U-uptake history causing very large uncertainties in the age results of both techniques. This study demonstrates the particular strength that lies in the integration of ESR and U-series dating analyses allowing the estimation of the U-uptake history. We obtained a combined ESR/U-series age estimate of 412 +/- 25 ka (average of six analyses on two teeth). This pinpoints the deposition of the faunal remains to the time of the transition between oxygen isotope stages 12 and 11. This is in agreement with the faunal composition which show a mixture of cold adapted northern mammals and more subtropical-tropical southern elements. The age also implies that the advanced Hexian Homo erectus occurred at a similar time as the less advanced Homo erectus specimens at Locality 1 at Zhoukoudian (LI-LIII).

Animals↗
PubMed1997

ESR analysis of teeth from the palaeoanthropological site of Zhoukoudian, China.

An ESR dating study on teeth collected from layers 3, 6/7 and 10 at Locality 1, Zhoukoudian provides results that are in general agreement with an earlier multi-dating study and confirm an age range of 300-550 ka for the Homo erectus remains in the Peking Man Cave. Uncertainties due to U-uptake and the external gamma dose rates do not allow very precise age estimates for the respective layers.

Animals↗
PubMed1996

Dated co-occurrence of Homo erectus and Gigantopithecus from Tham Khuyen Cave, Vietnam.

Tham Khuyen Cave (Lang Son Province, northern Vietnam) is one of the more significant sites to yield fossil vertebrates in east Asia. During the mid-1960s, excavation in a suite of deposits produced important hominoid dental remains of middle Pleistocene age. We undertake more rigorous analyses of these sediments to understand the fluvial dynamics of Pleistocene cave infilling as they determine how skeletal elements accumulate within Tham Khuyen and other east Asian sites. Uranium/thorium series analysis of speleothems brackets the Pleistocene chronology for breaching, infilling, and exhuming the regional paleokarst. Clast analysis indicates sedimentary constituents, including hominoid teeth and cranial fragments accumulated from very short distances and under low fluvial energy. Electron spin resonance analysis of vertebrate tooth enamel and sediments shows that the main fossil-bearing suite (S1-S3) was deposited about 475 thousand years ago. Among the hominoid teeth excavated from S1-S3, some represent Homo erectus and Gigantopithecus blacki. Criteria are defined to differentiate these teeth from more numerous Pongo pygmaeus elements. The dated co-occurrence of Homo erectus and Gigantopithecus blacki at Tham Khuyen helps to establish the long co-existence of these two species throughout east Asia during the Early and Middle Pleistocene.

Animals↗
PubMed1993

Mass-spectrometric U-series dates for Israeli Neanderthal/early modern hominid sites.

The nature of the relationship between Neanderthals and early modern Homo sapiens is controversial, yet it is fundamental to our understanding of early human evolution. The Middle Palaeolithic sites of Israel are critical to this debate, because unlike those of western Europe and Africa they contain both Neanderthal (at Tabun and Kebara for example) and anatomically modern hominids (as at Skhul and Qafzeh). Here we present new mass spectrometric 230Th/234U dates for dental fragments from the Middle Palaeolithic burial sites of Tabun, Qafzeh and Skhul. These data, combined with published ages from electron spin resonance (ESR), provide compelling evidence that the Tabun Neanderthals and Qafzeh early modern Homo sapiens were approximately coeval in the southern Levant some 100 +/- 5 kyr ago, but indicate that some of the Skhul material is younger. The study also shows that combined mass-spectrometric 230Th/234U and ESR dating is an invaluable technique for dating archaeological sites beyond the range of radiocarbon dating.

Animals↗
PubMed1992

Electron spin resonance (ESR) dating of the origin of modern man.

Many materials found in archaeological sites are able to trap electronic charges as a result of bombardment by radioactive radiation from the surrounding sediment. The presence of these trapped charges can be detected by electron spin resonance (ESR) spectroscopy: the intensity of the ESR signal is a measure of the accumulated dose and thus of the age. Tooth enamel is ubiquitous at archaeological sites and is well suited for ESR dating, with a precision of about 10-20%. This method has now been used to date many sites critical to the biological and cultural evolution of modern man. Dates for sites in Israel and Africa have demonstrated the existence of anatomically modern humans more than 100 ka ago.

Animals↗
PubMed1992

[Incidence and importance of thyroid gland changes in clinical patients].

The thyroid gland of 536 patients of a medical hospital in an iodine deficient area was investigated by ultrasound. According to the sonographic pattern and to the scintigraphic imaging the focal lesions were analysed as micro- or macrofollicular adenomas, autonomous adenomas, cysts and chalk. The prevalence of goitres was 37.7%. The prevalence of goitres was higher in women (45%) than in men (30%). Focal lesions could be observed in 27.6%, equally more often in women (36%) than in men (18.9%). The frequency of focal lesions increased with the age of the patients and with the volume of the thyroid gland. Autonomous adenomas were found three times more often in women than in men. Hyperthyroidism was only observed in patients with nodules larger than 4 cm in diameter. Sonographic screening examinations of the thyroid gland seem to be useful in all patients of a clinic of medicine because of the risk (25%) of iodine contamination by diagnostic measures.

Adolescent↗
PubMed1991

[Ultrasonic diagnosis of tumors of the cecum and ascending colon].

The results of preoperative ultrasound investigations were compared with the intraoperative findings in 42 patients (27 women, 15 men) operated on because of tumours of the cecum or colon ascendens. In 34 of 42 patients (i.e. 81%) the tumour could be correctly diagnosed by ultrasound. In 3 cases the investigator was not sure about imaging the tumour. Only in 5 cases (i.e. 12%) the tumour was not identified by ultrasound scanning. 4 out of these 5 patients had attended the hospital to be operated on because of a carcinoma of the rectum and the second carcinoma of the large bowel was found by chance intraoperatively. In 16 patients in whom the diagnosis of a large bowel carcinoma had not been established before, the tumour could be primarily diagnosed by ultrasound.

Adult↗