1,326 research outputs found
Direct Mechanocatalysis of Metal Catalysed Coupling Reactions in Ball Mills
Sustainability is an urgent need to secure the progress of our civilization and to reach it is getting more and more into common conscious. From a chemists viewpoint, this means the customary practices of the last centuries have to be overcome, chemicals and chemical processes must be designed safe and environmentally friendly without long term consequences while at the same time conserving resources. A main part within this is the reduction of toxic waste, often originated in solvents. To accomplish this, new paths have to be discovered. One possible path is mechanochemistry, which describes chemical reactions initiated by mechanical forces like milling balls and vessels in a ball mill. In this environment solubility is not required and thus turns the use of solvents obsolete. However, in mechanochemical catalytic reactions for instance catalyst complexes with ligands are used, that originally ensured solubility in the former reaction medium. Since no solubility is required in this solvent free reaction environment, the complexes can be simplified to salts or further to pure metal powder catalysts. Complexes, salts and powders alike are difficult to recycle from the reaction mixture, thwarting the aim of sustainability. A concept to overcome this drawback is direct mechanocatalysis that uses milling materials themselves made of the catalytic metal, likewise accounting for the catalyst and the energy input. The aim of the thesis on hand was to expand the concept towards new direct mechanocatalytic reactions and gain insights beyond the mere phenomenology. In detail, the palladium catalysed Suzuki coupling as well as the copper catalysed Ullmann reaction/coupling, and Glaser coupling were investigated
GCC-Plugin for Automated Accelerator Generation and Integration on Hybrid FPGA-SoCs
In recent years, architectures combining a reconfigurable fabric and a
general purpose processor on a single chip became increasingly popular. Such
hybrid architectures allow extending embedded software with application
specific hardware accelerators to improve performance and/or energy efficiency.
Aiding system designers and programmers at handling the complexity of the
required process of hardware/software (HW/SW) partitioning is an important
issue. Current methods are often restricted, either to bare-metal systems, to
subsets of mainstream programming languages, or require special coding
guidelines, e.g., via annotations. These restrictions still represent a high
entry barrier for the wider community of programmers that new hybrid
architectures are intended for. In this paper we revisit HW/SW partitioning and
present a seamless programming flow for unrestricted, legacy C code. It
consists of a retargetable GCC plugin that automatically identifies code
sections for hardware acceleration and generates code accordingly. The proposed
workflow was evaluated on the Xilinx Zynq platform using unmodified code from
an embedded benchmark suite.Comment: Presented at Second International Workshop on FPGAs for Software
Programmers (FSP 2015) (arXiv:1508.06320
Rhodium-catalysed hydroformylation of N-(2-propenyl)-β-lactams as a key step in the synthesis of functionalised N-[4-(2-oxoazetidin-1-yl)but-1-enyl]acetamides
Biologically relevant functionalised N-[4-(2-oxoazetidin-1-yl)but-1-enyl]acetamides have been prepared in a two-step approach starting from N-(2-propenyl)-beta-lactams, involving initial rhodium-catalysed hydroformylation followed by subjection of the obtained aldehydes to Staudinger reaction conditions after initial imination
BioHyTec: Biohybride Technologien in der Hauptstadtregion – Kompetenzbildung und Aufbau einer regionalen Wertschöpfungskette
Das Bundesministerium für Bildung und Forschung (BMBF) startete 1999 mit dem InnoRegio-Wettbewerb eine neuartige Förderinitiative unter der Leitidee „Innovative Impulse in den Neuen Ländern“. In zahlreichen Regionen wurden Aktivitäten in Gang gesetzt, um neue Formen der Zusammenarbeit von Menschen aus den unterschiedlichsten Bereichen zu entwickeln und damit die Wertschöpfung und Wettbewerbsfähigkeit in den ostdeutschen Regionen zu erhöhen. An dieser Ausschreibung nahmen in der Anfangsphase 444 Bewerberregionen teil. Nach der ersten Jury-Sitzung im Oktober 1999 wurden 50 InnoRegios ausgewählt, in einer Entwicklungsphase ihre Kernkompetenzen herauszufiltern und tragfähige Innovationskonzepte zu erarbeiten. Mit der zweiten Jury-Sitzung im Herbst 2000 fiel der Startschuss zur Umsetzungsphase. Zur Zeit werden vom BMBF 23 InnoRegios in den Neuen Ländern gefördert
8E-17 fractional laser frequency instability with a long room-temperature cavity
We present a laser system based on a 48 cm long optical glass resonator. The
large size requires a sophisticated thermal control and optimized mounting
design. A self balancing mounting was essential to reliably reach sensitivities
to acceleration of below < 2E-10 /g in all directions.
Furthermore, fiber noise cancellations from a common reference point near the
laser diode to the cavity mirror and to additional user points (Sr clock and
frequency comb) are implemented. Through comparison to other cavity-stabilized
lasers and to a strontium lattice clock an instability of below 1E-16 at
averaging times from 1 s to 1000 s is revealed
Conditioning a current source using OCCII-GIC for EIT systems
Multi-Frequency EIT has been developed to evaluate the permittivity spectrum of a medium using an improved Howland source. Stray capacitance reduces the output impedance, bandwidth of the data collection leading to erroneous measurements. To address this, we have designed a current source, which uses a novel OCCII - GIC to cancel stray capacitance. The system achieves high output impedance over a 5 MHz frequency range
Bewegung – vielseitige Medizin, die wirkt : dosierte körperliche Aktivität bei chronischen Erkrankungen steigert Gesundheit und Lebensqualität
Der Mensch ist dazu geschaffen, sich zu bewegen. Tut er es nicht, beispielsweise weil seine Arbeit ihn vor den Computerbildschirm zwingt und er seiner Nahrung nicht mehr hinterherjagen muss, wird er krank. So betrifft der "Altersdiabetes" inzwischen immer mehr Kinder und Jugendliche. Bei erwachsenen Männern, und zunehmend auch bei Frauen, führt die Kombination von Stress und Bewegungsarmut häufig zu Herz- und Kreislauferkrankungen. Frauen sind vor allem nach den Wechseljahren durch Osteoporose, Gebärmutterhals- und Brustkrebs bedroht. Erstmals sterben weltweit mehr Menschen an nicht übertragbaren Erkrankungen als an Infektionserkrankungen. Aber es gibt auch eine gute Nachricht: Regelmäßige körperliche Aktivität kann diesen chronischen Erkrankungen vorbeugen und spielt bei ihrer Therapie eine bedeutsame Rolle
A Reconfigurable Outer Modem Platform for Future Communications Systems
Future mobile and wireless communications networks
require flexible modem architectures with high performance.
Efficient utilization of
application specific flexibility is key to fulfill these
requirements.
For high throughput a single processor can not provide
the necessary computational power.
Hence multi-processor architectures become necessary.
This paper presents a multi-processor platform based on a new
dynamically reconfigurable application specific instruction set processor (dr-ASIP)
for the application domain of channel decoding.
Inherently parallel decoding tasks can be mapped onto individual processing nodes.
The implied challenging inter-processor communication is efficiently handled
by a Network-on-Chip (NoC) such that the throughput of each node is not degraded.
The dr-ASIP features Viterbi and Log-MAP decoding
for support of convolutional and turbo codes
of more than 10 currently specified mobile and wireless standards.
Furthermore, its flexibility allows for adaptation to future systems
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