The retro-ene reaction of gaseous immonium ions revisited

The retro-ene reaction is a common reaction of metastable immonium ions, leading to the expulsion of an alkene molecule. The kinetic energy release that accompanies this reaction decreases with alkyl substitution on the γ-carbon of the immonium ion. A number of authors have taken this result to indicate that the retro-ene reaction proceeds in a non-concerted manner via a carbocation intermediate. Using ab initio calculations to test this hypothesis we find that the retro-ene reaction is a concerted process, in which the reactant immonium ion is connected to the products via a single six-membered cyclic transition state. The calculated energy barriers and the measured kinetic energy releases are highly sensitive to alkyl substitution at the γ-position, which indicates that a substantial fraction of the positive charge of the transition state resides at the γ-carbon, not that the retro-ene reaction is a stepwise process with a carbocation intermediate

A codesign case study: implementing arithmetic functions in FPGAs

Different way of implementing and designing arithmetic functions for 16/32 bit integers in FPGA technology are studied. This also includes a comparison of four different design methods. The results are used to increase the overall system performance in a dedicated 3D image analysis prototype system by moving a vector length calculation from software to hardware. The conclusion is that by adding one relatively simple board containing two FPGA's in the prototype setup, the total computing time is reduced by 30 %. The total amount of image data, in this case 300 Mbyte which has to be transmitted via network, is reduced by a factor of two, and the required network bandwidth is reduced similarly. 1 Introduction This paper describes and analyses different ways of designing and implementing the arithmetic functions X 2 + Y 2 and p Z, where X and Y are 16 bit integers and Z is a 32 bit integer, in FPGA 1 technology. In a prototype setup, there is 2.5 ¯s available for calculating the..

Energy Spectrum of a constrained Quantum Particle and the Willmore Energy of the constraining Surface

Geometric and topological bounds are obtained for the first energy level gap of a particle constrained to move on a compact surface in 3-space. Moreover, geometric properties are found which allows for stationary and uniformly distributed wave functions to exist on the surface

A distributed-object infrastructure for corporate websites

A corporate website is the virtual representation of a cor-poration or organization on the Internet. Corporate web-sites face numerous problems due to their large size and complexity, and the nonscalability of the underlying Web infrastructure. Current solutions to these problems gener-ally rely on traditional scaling techniques such as caching and replication. These are usually too restrictive, however; taking a one-size-fits-all approach and applying the same solution to every document. We propose Globe as a founda-tion upon which to build scalable corporate websites, and introduce GlobeDoc, a website model based on Globe dis-tributed shared objects. This paper describes GlobeDoc, highlighting the design and technical details of the infras-tructure. 1