Search for supernova-produced 60Fe in a marine sediment

An 60Fe peak in a deep-sea FeMn crust has been interpreted as due to the signature left by the ejecta of a supernova explosion close to the solar system 2.8 +/- 0.4 Myr ago [Knie et al., Phys. Rev. Lett. 93, 171103 (2004)]. To confirm this interpretation with better time resolution and obtain a more direct flux estimate, we measured 60Fe concentrations along a dated marine sediment. We find no 60Fe peak at the expected level from 1.7 to 3.2 Myr ago. However, applying the same chemistry used for the sediment, we confirm the 60Fe signal in the FeMn crust. The cause of the discrepancy is discussed.Comment: 15 pages, 5 figures, submitted to PR

Simulating ice core 10Be on the glacial–interglacial timescale

10Be ice core measurements are an important tool for paleoclimate research, e.g., allowing for the reconstruction of past solar activity or changes in the geomagnetic dipole field. However, especially on multi-millennial timescales, the share of production and climate-induced variations of respective 10Be ice core records is still up for debate. Here we present the first quantitative climatological model of the 10Be ice concentration up to the glacial–interglacial timescale. The model approach is composed of (i) a coarse resolution global atmospheric transport model and (ii) a local 10Be air–firn transfer model. Extensive global-scale observational data of short-lived radionuclides as well as new polar 10Be snow-pit measurements are used for model calibration and validation. Being specifically configured for 10Be in polar ice, this tool thus allows for a straightforward investigation of production- and non-production-related modulation of this nuclide. We find that the polar 10Be ice concentration does not immediately record the globally mixed cosmogenic production signal. Using geomagnetic modulation and revised Greenland snow accumulation rate changes as model input, we simulate the observed Greenland Summit (GRIP and GISP2) 10Be ice core records over the last 75 kyr (on the GICC05modelext timescale). We show that our basic model is capable of reproducing the largest portion of the observed 10Be changes. However, model–measurement differences exhibit multi-millennial trends (differences up to 87% in case of normalized to the Holocene records) which call for closer investigation. Focusing on the (12–37) b2k (before the year AD 2000) period, mean model–measurement differences of 30% cannot be attributed to production changes. However, unconsidered climate-induced changes could likely explain the model–measurement mismatch. In fact, the 10Be ice concentration is very sensitive to snow accumulation changes. Here the reconstructed Greenland Summit (GRIP) snow accumulation rate record would require revision of +28% to solely account for the (12–37) b2k model–measurement differences

From Gravitons to Gravity: Myths and Reality

There is a general belief, reinforced by statements in standard textbooks, that: (i) one can obtain the full non-linear Einstein's theory of gravity by coupling a massless, spin-2 field $h_{ab}$ self-consistently to the total energy momentum tensor, including its own; (ii) this procedure is unique and leads to Einstein-Hilbert action and (iii) it only uses standard concepts in Lorentz invariant field theory and does not involve any geometrical assumptions. After providing several reasons why such beliefs are suspect -- and critically re-examining several previous attempts -- we provide a detailed analysis aimed at clarifying the situation. First, we prove that it is \textit{impossible} to obtain the Einstein-Hilbert (EH) action, starting from the standard action for gravitons in linear theory and iterating repeatedly. Second, we use the Taylor series expansion of the action for Einstein's theory, to identify the tensor $\mathcal{S}^{ab}$, to which the graviton field $h_{ab}$ couples to the lowest order. We show that the second rank tensor $\mathcal{S}^{ab}$ is {\it not} the conventional energy momentum tensor $T^{ab}$ of the graviton and provide an explanation for this feature. Third, we construct the full nonlinear Einstein's theory with the source being spin-0 field, spin-1 field or relativistic particles by explicitly coupling the spin-2 field to this second rank tensor $\mathcal{S}^{ab}$ order by order and summing up the infinite series. Finally, we construct the theory obtained by self consistently coupling $h_{ab}$ to the conventional energy momentum tensor $T^{ab}$ order by order and show that this does {\it not} lead to Einstein's theory. (condensed).Comment: revtex; 19 pages; no figure

Population Regulation of Gypsy Moth (Lepidoptera: Lymantriidae) by Parasitoids: Does Spatial Density Dependence Lead to Temporal Density Dependence?

In 1987, four gypsy moth, Lymantria dispar, (L.) densities were established in eight 1-ha plots in western Massachusetts, ranging from 50,000 to 1.4 M neonates per hectare. Two tachinid parasitoid species, Compsilura concinnata (Meigen) and Parasetigena silvestris (Robineau-Desvoidy), exhibited spatial density-dependent parasistism and C. concinnata was the major source of gypsy moth mortality. This study investigated whether spatial density-dependent mortality in 1987 translated into temporal density-dependent mortality of experimental gypsy moth populations created the following year (1988). C. concinnata was responsible for the largest percentage of gypsy moth mortality again in 1988, however, overall mortality caused by C. concinnata in 1988 was considerably less than in 1987. Gypsy moth mortality caused by P. silvestris was greater in 1988. The killing power of either parasitoid in 1988 were not linearly related to the estimated density of the parasitoids produced in the previous year. We saw no evidence for a between-generation numerical response (1-ha scale) of either the generalist parasitoid, C. concinnata, or the specialist parasitoid, P. silvestris, between 1987 and 198

Burn Care in the Greek and Roman Antiquity

The last century brought about more rapid new developments in the treatment of burns, which significantly lowered the mortality of burn injuries. However, burns were already treated in antiquity, where the threshold from spirituality to scientific medicine originated. The existing literature on burn treatment is very limited and there are many cross-references, some of them incorrect. The aim of this work by an interdisciplinary team of historians and physicians is to offer a more precise reproduction of the burn treatment of Greek and Roman antiquity using original texts in context and with a modern scientific background. There are many sources from ancient doctors on the subject of burn treatment, as well as the treatment of burned-out wounds and frostbite, which have not yet been mentioned. The literature research also showed an understanding of scientific contexts in ancient medicine, such as antiseptics or rheology. Interestingly, there was a change in burn medicine from everyday Greek medicine to Roman military medicine with other burn patterns. The care of patients using analgetics and the therapy of burn shock arose from the literature. The ancient world is considered to be the foundation of medicine, but it is believed to have been based mainly on shamanism rather than science. However, already more than two millennia ago, burns were correctly assessed and treated according to today’s scientific standards and scientific relationships were recognized

Reality Conditions and Ashtekar Variables: a Different Perspective

We give in this paper a modified self-dual action that leads to the $SO(3)$-ADM formalism without having to face the difficult second class constraints present in other approaches (for example if one starts from the Hilbert-Palatini action). We use the new action principle to gain some new insights into the problem of the reality conditions that must be imposed in order to get real formulations from complex general relativity. We derive also a real formulation for Lorentzian general relativity in the Ashtekar phase space by using the modified action presented in the paper.Comment: 22 pages, LATEX, Preprint CGPG-94/10-

The 63^{63}Ni(n,γ\gamma) cross section measured with DANCE

The neutron capture cross section of the s-process branch nucleus $^{63}$Ni affects the abundances of other nuclei in its region, especially $^{63}$Cu and $^{64}$Zn. In order to determine the energy dependent neutron capture cross section in the astrophysical energy region, an experiment at the Los Alamos National Laboratory has been performed using the calorimetric 4$\pi$ BaF$_2$ array DANCE. The (n,$\gamma$) cross section of $^{63}$Ni has been determined relative to the well known $^{197}$Au standard with uncertainties below 15%. Various $^{63}$Ni resonances have been identified based on the Q-value. Furthermore, the s-process sensitivity of the new values was analyzed with the new network calculation tool NETZ.Comment: 11 pages, 13 page

Zur Stabilität dialektaler Formen.: Eine real- und apparent-time-Analyse remanenter Merkmale in den ruralen Basisdialekten Österreichs

Stability is an essential but frequently underrepresented fact in the study of language variation and change. Although in dialectology the distinction between “primary” and “secondary” dialect features initially led to a certain consideration of stable features as opposed to more dynamic ones, more recent empirical studies have not taken any notice of the former. The question of stability is nevertheless crucial for dialectology. For example, the extent of dialect loss cannot be assessed without establishing which forms are stable. The aim of this study is therefore to address this desideratum by investigating ten dialectal features in Austria’s rural dialects. All ten examples concern variables of the vowel system which show large phonetic differences between dialect and standard variants. On the basis of a comprehensive dialect survey, both a real- and an apparent-time study is conducted to examine the extent and the factors of dialectal stability and change. The study provides evidence for a surprisingly high degree of stability and continuity in Austria’s rural dialects. Changes are not only restricted to a few variables, but also limited (a) to a lexical factor – only a small group of lexemes is not completely stable –, and (b) to a regional factor – only some eastern parts of Austria show a higher degree of change. Other factors, such as the extent of the spatial distribution of a form or the phonetic distance to the standard, do not prove to be relevant for stability and change of the variables