Transverse distinguishability of entangled photons with arbitrarily shaped spatial near- and far-field distributions

Entangled photons generated by spontaneous parametric down conversion inside a nonlinear crystal exhibit a complex spatial photon count distribution. A quantitative description of this distribution helps with the interpretation of experiments that depend on this structure. We developed a theoretical model and an accompanying numerical calculation that includes the effects of phase matching and the crystal properties to describe a wide range of spatial effects in two-photon experiments. The numerical calculation was tested against selected analytical approximations. We furthermore performed a double-slit experiment where we measured the visibility V and the distinguishability D and obtained $D^2 + V^2 = 1.43$. The numerical model accurately predicts these experimental results.Comment: 10 pages, 10 figure

P2N2-koordinierte Iridiumkomplexe für die enantioselektive Hydrierung von Ketonen

The work on hand describes the synthesis and characterization of various iridium analogues of well known Rh- and Ru-catalyst systems for the enantioselective hydrogenation of prochiral ketones. Particularly the catalytic potential of these and other predominantly P,N-coordinated cationic Ir(III)-compounds is investigated, thereby elucidating the correlation between the complexes' molecular structures (Variation of P- and N-Ligands), the product alcohol formed, the enantiomeric excess produced and the rate of hydrogenation. Considering the results of these investigations an alternative mechanism for the stereoselective hydrogantion of prochiral ketones with Ir(III)-catalysts is suggested.In der vorliegenden Arbeit werden verschiedene Iridiumanaloge bekannter Rh- und Ru-Katalysatorsysteme für die enentioselektive Hydrierung prochiraler Ketone synthetisiert und untersucht. Hierbei wird besonderes Augenmerk auf das katalytische Potential solcher und anderer kationischer Ir(III)-Verdindungen mit vorwiegender P,N-Koordination gelegt, wobei der Zusammenhang zwischen der Struktur des Katalysators (Variation der P- und N-Liganden) und gebildetem Produktalkohol, erzieltem Enantiomerenüberschuss und Hydriergeschwindigkeit erschlossen wird. Aufgrund der Erkenntnisse wird ein alternativer Mechanismus für die stereoselektive Hydrierung prochiraler Ketone mit Ir(III)-Katalysatoren aufgezeigt

Einfluss von Milchleistung und Nutzungsdauer auf den Product Carbon Footprint von Milch bei ökologisch wirtschaftenden Betrieben in Süddeutschland

Quantification and mitigation of greenhouse gas emissions is an intensively discussed topic. For dairy farms many studies consider a higher milk yield per cow for greenhouse gas mitigation but this often results in a reduction in herd fertility and thus more heifers are needed which may lead to more emissions in total. This paper presents the Product Carbon Footprint of 36 organic dairy farms and analyses the influence of milk yield per cow and longevity of dairy cows. Results are: (1) a product carbon footprint of 1,61 kg CO2eq/kg fat and protein corrected milk on average, (2) increasing milk yield per cow causes decreasing product carbon footprints (coefficient of determination 48 %) and (3) decreasing longevity per cow causes decreasing product carbon footprints but to a lower degree of influence (coefficient of determination 16 %). With regard to climate protection, not considering ethical aspects, a high milk yield per cow should be achieved rather than to focus on longevity

Erhebliche Effizienzpotenziale in der Färsenaufzucht der ökologischen Milchproduktion

In many organic farms there is a huge potential to increase efficiency in rearing heifers for replacement. This is the result of a study in 36 organic dairy farms with pasture from South Germany, which were analyzed economically in the years 2009 – 2011. In particular farms with high production efficiency and low production costs per heifer show decreased production times per cow for some months, but this effect is overcompensated by higher milk yields per cow. This is one reason why they perform economically better with regard to the dairy farm. The most important factors influencing the production costs per heifer are the costs for forage and labor. Based on the results of this study, more efficient rearing of heifers with lower production costs seems necessary and worthwhil