The survival of PCR-amplifiable DNA in cow leather

We have investigated the survival of PCR-amplifiable mitochondrial and nuclear DNA in a small number of modern and medieval bovine leather samples. The results of this preliminary investigation demonstrate that, while no nuclear DNA can be PCR-amplified from any of the specimens, mitochondrial DNA can be amplified from all samples. To investigate this contrasting pattern of DNA survival further, we have vegetable-tanned cow skin in our own laboratory, and directly assayed the survival of PCR-amplifiable mitochondrial and nuclear DNA at each step of the process. The results indicate that nuclear DNA is reduced to sub-amplifiable levels as a result of the tanning baths, whereas amplifiable mitochondrial DNA survives the complete process. Our results suggest that old and archaeological bovine leather may represent a useful source of genetic information, although this information will most likely be limited to that which can be gained from mitochondrial DNA.     

Das Klima von Bayreuth

Zusammenfassung Das Klima von Oberfranken liegt in einem übergangsbereich zwischen ozeanisch und kontinental gepr?gten Klimaten. Der Beitrag stellt langj?hrig ermittelte Klimadaten und Klimatrends für die Stadt Bayreuth vor. Er geht auf die Herausforderungen ein, die sich daraus für die Stadtplanung ergeben, auch und besonders im Zusammenhang mit dem Klimawandel.     

Radiocarbon dating of prehistoric hearths in alpine northern Sweden: problems and possibilities

The chronology of prehistoric Sami settlement sites has previously been established by conventional radiocarbon dating of bulk charcoal samples associated with hearths from sunken hut floors (stállo-foundations). Here we present results of a comprehensive dating exercise of stállo-foundations in the alpine area of northern Scandinavia using Accelerator Mass Spectrometry (AMS) radiocarbon dating of charcoal. Over a 3 km² study area, AMS calibrated ages of hearth charcoal from 22 stállo-foundations across 12 sites securely date these features to between cal. AD 640 and AD 1180. Only small variations in age were found between charcoal samples from different areas of a given hearth. Statistical analysis of all the charcoal AMS radiocarbon dates obtained reveals that 12 stállo-foundations across nine sites are contemporaneous and date to the Viking Period (AD 800–AD 1050). The tightly constrained AMS-based chronology of stállo-foundations contrasts with the existing chronology based on conventional radiocarbon analysis, which places these features within a significantly greater time-frame of between AD 600 and AD 1900, with most dates ranging between AD 800 and AD 1350.This discrepancy is likely to result from the necessity of collecting composite hearth charcoal particles, which may originate from different phases of occupation, in order to achieve the required final carbon content for conventional radiocarbon analysis. We argue that the new AMS-based radiocarbon chronology of stállo-foundations presented here supersedes the existing chronology based on conventional (Gas Proportional counting) radiocarbon analysis and we advocate the use of AMS radiocarbon dating in future hearth investigations.     

Reproduction rates in multiregion modeling systems for HIV / AIDS

The persistence of HIV/AIDS has seen a revival of academic interest in the development of modeling systems to assist understanding the population dynamics of this infection. Moreover, it has become increasingly recognized that a key component of these systems for interpreting disease prevention is their reproduction rate, which provides an indication of whether an epidemic might start in a community described by a particular set of epidemiological characteristics. The properties of these rates have been explored in detail for models of a single risk behavior but not for multiregion formats that allow for the transfer of infection between geographical units. Therefore, in this paper I derive reproduction rates for a multiregion HIV/AIDS model together with their associated critical thresholds that estimate the minimum population of susceptibles necessary for an epidemic to begin. These statistics are interpreted for a simplified global setting representing regional variations in the potential onset of HIV/AIDS. In the discussion I examine the potential applicability of these results to understanding HIV/AIDS prevention.