Jeroen W. Thompson

New radiometric ages for the bh-1 hominin from Balanica (Serbia): implications for understanding the role of the Balkans in Middle Pleistocene human evolution

Newly obtained ages, based on electron spin resonance combined with uranium series isotopic analysis, and infrared/post-infrared luminescence dating, provide a minimum age that lies between 397 and 525 ka for the hominin mandible BH-1 from Mala Balanica cave, Serbia. This confirms it as the easternmost hominin specimen in Europe dated to the Middle Pleistocene. Inferences drawn from the morphology of the mandible BH-1 place it outside currently observed variation of European Homo heidelbergensis. The lack of derived Neandertal traits in BH-1 and its contemporary specimens in Southeast Europe, such as Kocabaş, Vasogliano and Ceprano, coupled with Middle Pleistocene synapomorphies, suggests different evolutionary forces acting in the east of the continent where isolation did not play such an important role during glaciations.

Optically stimulated luminescence dosimetry with gypsum wallboard (drywall)

Gypsum wallboard (drywall) represents an attractive target for retrospective dosimetry by optically stimulated luminescence (OSL) in the event of a radiological accident or malicious use of nuclear material. In this study, wallboard is shown to display a radiation-induced luminescence signal (RIS) as well as a natural background signal (NS), which is comparable in intensity to the RIS. Excitation and emission spectra show that maximum luminescence intensity is obtained for stimulation with blue light-emitting diodes (470 nm) and for detection in the ultraviolet region (290-370 nm). It is necessary to decrease the optical stimulation power dramatically in order to adequately separate the RIS from the interfering background signal. The necessary protocols are developed for accurately measuring the absorbed dose as low as 500 mGy and demonstrate that the RIS decays logarithmically with storage time, with complete erasure expected within 1-4 d.

A method to transform a variable thermal regime to a physiologically equivalent effective temperature

We present a method to characterize variable thermal regimes in terms of an equivalent or effective temperature. Our method is based on a first order exponential transformation of a time series of temperatures to yield an exponentially-weighted mean temperature characteristic of the regime and independent of any particular species or end point. The resulting effective temperature or exponential mean, Te¯, offers an improved method for summarizing mean temperature where biological response scales exponentially to temperature. The exponential mean allows growth under varying thermal regimes to be predicted using constant temperature models and offers a compact descriptor communicating the growth capacity of variable thermal regimes. The method combines mathematical simplicity with translatability to different Q10 values without recourse to the underlining time series data. It also provides a quantitative baseline that improves on mean temperature by incorporating the effect of Jensens inequality and it remains applicable at near zero temperatures where thermal sums lack accuracy.

Single-aliquot EPR dosimetry of wallboard (drywall)

Electron paramagnetic resonance spectra and dose-response curves are presented for a variety of wallboard samples obtained from different manufacturing facilities, as well as for source gypsum and anhydrite. The intensity of the CO(3)(-) paramagnetic centre (G2) is enhanced with gamma radiation. Isothermal decay curves are used to propose annealing methods for the removal of the radiosensitive CO(3)(-) radical without affecting the unirradiated baseline. Post-irradiation annealing of wallboard prevents recuperation of the radiosensitive CO(3)(-) radical with additional irradiation. A single-aliquot additive dose procedure is developed that successfully measures test doses as low as 0.76 Gy.