Radioactive isotope analyses of skeletal materials in forensic science: a review of uses and potential uses

A review of information that can be provided from measurements made on natural and anthropogenic radionuclide activities in human skeletal remains has been undertaken to establish what reliable information of forensic anthropological use can be obtained regarding years of birth and death (and hence post-mortem interval (PMI)). Of the anthropogenic radionuclides that have entered the environment, radiocarbon (14C) can currently be used to generate the most useful and reliable information. Measurements on single bones can indicate whether or not the person died during the nuclear era, while recent research suggests that measurements on trabecular bone may, depending on the chronological age of the remains, provide estimates of year of death and hence PMI. Additionally, 14C measurements made on different components of single teeth or on teeth formed at different times can provide estimates of year of birth to within 1–2 years of the true year. Of the other anthropogenic radionuclides, 90Sr shows some promise but there are problems of (1) variations in activities between individuals, (2) relatively large analytical uncertainties and (3) diagenetic contamination. With respect to natural series radionuclides, it is concluded that there is no convincing evidence that 210Pb dating can be used in a rigorous, quantitative fashion to establish a PMI. Similarly, for daughter/parent pairs such as 210Po/210Pb (from the 238U decay series) and 228Th/228Ra (from the 232Th decay series), the combination of analytical uncertainty and uncertainty in activity ratios at the point of death inevitably results in major uncertainty in any estimate of PMI. However, observation of the disequilibrium between these two daughter/parent pairs could potentially be used in a qualitative way to support other forensic evidence

Combined Solar System and rotation curve constraints on MOND

The Modified Newtonian Dynamics (MOND) paradigm generically predicts that the external gravitational field in which a system is embedded can produce effects on its internal dynamics. In this communication, we first show that this External Field Effect can significantly improve some galactic rotation curves fits by decreasing the predicted velocities of the external part of the rotation curves. In modified gravity versions of MOND, this External Field Effect also appears in the Solar System and leads to a very good way to constrain the transition function of the theory. A combined analysis of the galactic rotation curves and Solar System constraints (provided by the Cassini spacecraft) rules out several classes of popular MOND transition functions, but leaves others viable. Moreover, we show that LISA Pathfinder will not be able to improve the current constraints on these still viable transition functions.Comment: 13 pages, 7 figures, accepted for publication in MNRA

Letter from Dr. Cathie

Letter regarding Dr. Koch speaking at 1957 Dallas AOA Convention

Seawater acidification more than warming presents a challenge for two Antarctic macroalgal-associated amphipods

Elevated atmospheric pCO2 concentrations are triggering seawater pH reductions and seawater temperature increases along the western Antarctic Peninsula (WAP). These factors in combination have the potential to influence organisms in an antagonistic, additive, or synergistic manner. The amphipods Gondogeneia antarctica and Paradexamine fissicauda represent prominent members of macroalgal-associated mesograzer assemblages of the WAP. Our primary objective was to investigate amphipod behavioral and physiological responses to reduced seawater pH and elevated temperature to evaluate potential cascading ecological impacts. For 90 d, amphipods were exposed to combinations of seawater conditions based on present ambient (pH 8.0, 1.5°C) and predicted end-of-century conditions (pH 7.6, 3.5°C). We recorded survival, molt frequency, and macroalgal consumption rates as well as change in wet mass and proximate body composition (protein and lipid). Survival for both species declined significantly at reduced pH and co-varied with molt frequency. Consumption rates in G. antarctica were significantly higher at reduced pH and there was an additive pH-temperature effect on consumption rates in P. fissicauda. Body mass was reduced for G. antarctica at elevated temperature, but there was no significant effect of pH or temperature on body mass in P. fissicauda. Exposure to the pH or temperature levels tested did not induce significant changes in whole body biochemical composition of G. antarctica, but exposure to elevated temperature resulted in a significant increase in whole body protein content of P. fissicauda. Our study indicates that while elevated temperature causes sub-lethal impacts on both species of amphipods, reduced pH causes significant mortality

Modified Baryonic Dynamics: two-component cosmological simulations with light sterile neutrinos

In this article we continue to test cosmological models centred on Modified Newtonian Dynamics (MOND) with light sterile neutrinos, which could in principle be a way to solve the fine-tuning problems of the standard model on galaxy scales while preserving successful predictions on larger scales. Due to previous failures of the simple MOND cosmological model, here we test a speculative model where the modified gravitational field is produced only by the baryons and the sterile neutrinos produce a purely Newtonian field (hence Modified Baryonic Dynamics). We use two component cosmological simulations to separate the baryonic N-body particles from the sterile neutrino ones. The premise is to attenuate the over-production of massive galaxy cluster halos which were prevalent in the original MOND plus light sterile neutrinos scenario. Theoretical issues with such a formulation notwithstanding, the Modified Baryonic Dynamics model fails to produce the correct amplitude for the galaxy cluster mass function for any reasonable value of the primordial power spectrum normalisation.Comment: 11 pages, 2 figures. Submitted to JCA

The wedding of modified dynamics and non-exotic dark matter in galaxy clusters

We summarize the status of Modified Newtonian Dynamics (MOND) in galaxy clusters. The observed acceleration is typically larger than the acceleration threshold of MOND in the central regions, implying that some dark matter is necessary to explain the mass discrepancy there. A plausible resolution of this issue is that the unseen mass in MOND is in the form of ordinary neutrinos with masses just below the experimentally detectable limit. In particular, we show that the lensing mass reconstructions of the clusters 1E0657-56 (the bullet cluster) and Cl0024+17 (the ring) do not pose a new challenge to this scenario. However, the mass discrepancy for cool X-ray emitting groups, in which neutrinos cannot cluster, pose a more serious problem, meaning that dark baryons could present a more satisfactory solution to the problem of unseen mass in MOND clusters.Comment: to appear in World Scientific, proceedings of DARK 200