63 research outputs found
Post-synthetic Modification of DUT-5-based Metal Organic Frameworks for the Generation of Single-site Catalysts and their Application in Selective Epoxidation Reactions
New singleâsite catalysts based on mixedâlinker metalâorganic frameworks with DUTâ5 structure, which contain immobilized Co2+, Mn2+ and Mn3+ complexes, have successfully been synthesized via postâsynthetic modification. 2,2ââBipyridineâ5,5ââdicarboxylate linkers were directly metalated, while 2âaminoâ4,4ââbiphenyldicarboxylate linkers were postâsynthetically modified by their conversion to Schiffâbase ligands and a subsequent immobilization of the metal complexes. The resulting materials were used as catalysts in the selective epoxidation of transâstilbene and the activities and selectivities of the different catalysts were compared. The influence of various reaction parameters on conversion, yield and selectivity were investigated. Very low catalyst amounts of 0.02â
molâ% were sufficient to obtain a high conversion of transâstilbene using molecular oxygen from air as the oxidant. For cobaltâcontaining MOF catalysts, conversions up to 90â% were observed and, thus, they were more active than their manganeseâcontaining counterparts. Recycling experiments and hot filtration tests proved that the reactions were mainly catalyzed via heterogeneous pathways
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the
distribution of arrival directions of the cosmic rays with energies
eV. These show a correlation with the distribution
of nearby extragalactic objects, including an apparent excess around the
direction of Centaurus A. If the particles responsible for these excesses at
are heavy nuclei with charge , the proton component of the
sources should lead to excesses in the same regions at energies . We here
report the lack of anisotropies in these directions at energies above
(for illustrative values of ). If the anisotropies
above are due to nuclei with charge , and under reasonable
assumptions about the acceleration process, these observations imply stringent
constraints on the allowed proton fraction at the lower energies
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
Aircraft engine particulate matter emissions from sustainable aviation fuels: Results from ground-based measurements during the NASA/DLR campaign ECLIF2/ND-MAX
The use of alternative jet fuels by commercial aviation has increased substantially in recent years. Beside the reduction of carbon dioxide emission, the use of sustainable aviation fuels (SAF) may have a positive impact on the reduction of particulate emissions. This study summarizes the results from a ground-based measurement activity conducted in January 2018 as part of the ECLIF2 ND-MAX campaign in Ramstein, Germany. Two fossil reference kerosenes and three different blends with the renewable fuel component HEFA-SPK (Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene) were burned in an A320 with V2527-A5 engines to investigate the effect of fuel naphthalene aromatic content and the corresponding fuel hydrogen content on nonvolatile particle number and mass emissions
Synthetic biology to access and expand nature's chemical diversity
Bacterial genomes encode the biosynthetic potential to produce hundreds of thousands of complex molecules with diverse applications, from medicine to agriculture and materials. Accessing these natural products promises to reinvigorate drug discovery pipelines and provide novel routes to synthesize complex chemicals. The pathways leading to the production of these molecules often comprise dozens of genes spanning large areas of the genome and are controlled by complex regulatory networks with some of the most interesting molecules being produced by non-model organisms. In this Review, we discuss how advances in synthetic biology â including novel DNA construction technologies, the use of genetic parts for the precise control of expression and for synthetic regulatory circuits â and multiplexed genome engineering can be used to optimize the design and synthesis of pathways that produce natural products
Preface.
Plants use resources, i.e. carbon, nutrients, water and energy, either for growth or to defend themselves from biotic and abiotic stresses. This volume provides a timely understanding of resource allocation and its regulation in plants, linking the molecular with biochemical and physiological-level processes. Ecological scenarios covered include competitors, pathogens, herbivores, mycorrhizae, soil microorganisms, carbon dioxide/ozone regimes, nitrogen and light availabilities. The validity of the “Growth-Differentiation Balance Hypothesis” is examined and novel theoretical concepts and approaches to modelling plant resource allocation are discussed. The results presented can be applied in plant breeding and engineering, as well as in resource-efficient stand management in agriculture and forestry
MobiKAM, Messen und PrĂŒfen mit mobilen Kameras im Arbeitsraum von Produktionsmaschinen: Gemeinsamer Abschlussbericht. Förderkennzeichen BMBF 02PU2520-24
In the project MobiKAM, the foundation for a seeing machine as an integrated system has been developed. Similar to the way tools are integrated in the machine, the camera operates as a mobile, energy self-sufficient optical sensor being a new interchangeable machine element. In comparison to available techniques, a more flexible and advanced measuring and testing in the working area of production machinery is facilitated. In the sense of Plug-and-Work, the camera system is integrated the easiest way into the machine as well as into the control system. For the use in the working area of a production machine, a camera system has been developed which is resistant to concussions and contamination as well as electromagnetic disturbances. To grant convenient installation and handling of the camera the way it is practiced with tools, self-sufficient energy supply and wireless communication for the transmission of control signals and image data will be implemented. Latest energy storage systems as well as a highly efficient energy management system ensure lengthy operating times. The exemplary implementation for the solutions worked out will be tested for a machine tool and a woodworking machine
- âŠ