Exact gravitational lensing and rotation curve

Based on the geodesic equation in a static spherically symmetric metric we discuss the rotation curve and gravitational lensing. The rotation curve determines one function in the metric without assuming Einstein's equations. Then lensing is considered in the weak field approximation of general relativity. From the null geodesics we derive the lensing equation and corrections to it.Comment: 12 pages, 1 figur

The Potential for Electromagnetic Metal Forming for Plane (Car Body) Components

Classical quasi-static technologies of sheet metal forming are not the only domain of the Fraunhofer Institute for Machine Tools and Forming Technology (IWU). It also delves into techniques for high-energy rate forming, such as gas generator technology, and it will be dedicating greater efforts to electromagnetic metal forming. Electromagnetic metal forming processes major potential for innovation and development in manufacturing car-body components since the benefits to be derived from this technique (such as extending the limitations of forming, enhancing spring back behavior, and delivering a high degree of flexibility in production) have this sector's key problems in mind. The Fraunhofer Institute for Machine Tools and Forming Technology focuses its research on coming up with technology, tool and plant strategies suitable for manufacturing medium-sized and large car-body components. There are two technological directions that IWU targets in this field of research. First of all, given the existing technical and physical process constraints, it is studying the possibilities of large-scale and partial deformation since both directions are of importance for the targeted products. However, these two approaches have very different requirements for designing and tools. The first approach forms components without preforming. Several forming steps are required for mapping typical car-body component shapes either with serial workstations or a flexible tool system. The partial electromagnetic metal forming approach means using integrated plant components, i.e. combining conventional press equipment with a magnetic forming plant. This can tap a potential that encompasses the technological benefits mentioned above while hiking productivity and scaling down the expenditures for investing in equipment

Low atmospheric CO2 levels during the Little Ice Age due to cooling-induced terrestrial uptake

Low atmospheric carbon dioxide (CO2) concentration during the Little Ice Age has been used to derive the global carbon cycle sensitivity to temperature. Recent evidence confirms earlier indications that the low CO2 was caused by increased terrestrial carbon storage. It remains unknown whether the terrestrial biosphere responded to temperature variations, or there was vegetation re-growth on abandoned farmland. Here we present a global numerical simulation of atmospheric carbonyl sulfide concentrations in the pre-industrial period. Carbonyl sulfide concentration is linked to changes in gross primary production and shows a positive anomaly during the Little Ice Age. We show that a decrease in gross primary production and a larger decrease in ecosystem respiration is the most likely explanation for the decrease in atmospheric CO2 and increase in atmospheric carbonyl sulfide concentrations. Therefore, temperature change, not vegetation re-growth, was the main cause of the increased terrestrial carbon storage. We address the inconsistency between ice-core CO2 records from different sites measuring CO2 and δ13CO2 in ice from Dronning Maud Land (Antarctica). Our interpretation allows us to derive the temperature sensitivity of pre-industrial CO2 fluxes for the terrestrial biosphere (γL = -10 to -90 Pg C K-1), implying a positive climate feedback and providing a benchmark to reduce model uncertainties

Atmos. Chem. Phys.

Measurements of the complete isotopic composition of atmospheric CO ((CO)-C-13, (CO)-C-14, (CO)-O-17, (CO)-O-18) have been carried out at the high northern latitude stations Spitsbergen, Norway, and Alert, Canada. The annual changes of the isotope signatures reflect the seasonally varying contributions from the individual CO sources and the OH sink. Short-term variability is small at the remote sampling locations. Nevertheless, the interannual variability is considerable, in particular for the summer minimum. The most prominent event was a strong increase in CO in 1998 that persisted for several months. Using the isotope signatures it is possible to clearly identify extraordinarily strong biomass burning during that season as the cause for this large-scale CO anomaly. In 1997, on the other hand, biomass burning emissions were very low, leading to an unusually low summer minimum and corresponding isotope signatures. The results underscore that monitoring of CO and its isotopic composition at remote high latitude stations is a valuable tool to better understand long- term variations of CO that are representative for the whole high northern latitude region

Using 14C, 13C, 18O and 17O isotopic variations to provide insights into the high northern latitude surface CO inventory

International audienceMeasurements of the complete isotopic composition of atmospheric CO (13 CO, 14 CO, C 17 O, C 18 O) have been carried out at the high northern latitude stations Spitsbergen, Norway, and Alert, Canada. The annual changes of the isotope signatures reflect the seasonally varying contributions from the individual CO sources and the OH sink. Short-term variability is small at the remote sampling locations. Nevertheless, the interannual variability is considerable, in particular for the summer minimum. The most prominent event was a strong increase in CO in 1998 that persisted for several months. Using the isotope signatures it is possible to clearly identify extraordinarily strong biomass burning during that season as the cause for this large-scale CO anomaly. In 1997, on the other hand, biomass burning emissions were very low, leading to an unusually low summer minimum and corresponding isotope signatures. The results underscore that monitoring of CO and its isotopic composition at remote high latitude stations is a valuable tool to better understand long-term variations of CO that are representative for the whole high northern latitude region