Cometabolic isoterpinolene formation from isolimonene by denitrifying Alcaligenes defragrans

Alcaligenes defragrans strains denitrify on monoterpenes with an unsaturated hydrocarbon structure. a new cometabolic reaction, the formation of isoterpinolene from isolimonene, was detected in cultures that grew on a monoterpene. The biotransformation of isolimonene, a monocyclic monoterpene with a sp(3)-hybridized C1 atom of the menthane skeleton, contrasts with the complete mineralization of monoterpenes with a sp(2)-hybridized C1 atom. This selectivity indicates a demand for a sp(2)-hybridized C1 atom as structural property for monoterpenes that can be oxidized by A. defragrans. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved

A local global question in automorphic forms

In this paper, we consider the \SL(2) analogue of two well-known theorems about period integrals of automorphic forms on \GL(2): one due to Harder-Langlands-Rapoport, and the other due to Waldspurger.Comment: 28 page

Network TraÆc behaviour in switched ethernet systems

Measurements on a high-performance switched Ethernet system are presented that reveal new insights into the statistical nature of le server and web server traÆc. Both le sizes and data requested from the web server are shown to match well a truncated Cauchy distribution. This is a distribution with heavy tails similar in nature to the commonly used Pareto distribution but with a much better t over smaller le/request sizes. We observe self similar characteristics in the traÆc at both servers and also at a CPU server elsewhere on the network. TraÆc from this server is predominantly targeted at the le and web servers, suggesting that self-similar properties at one point on a network are being propagated to other points. A simple simulation model of an isolated server is presented with Poisson arrivals and service (packet transmission) demands with the same Cauchy distribution as we observed. The departure process is shown to follow a power law and the corresponding power spectrum is shown to match extremely well that of the observed traÆc. This supports the suggested link between le/request size distribution and self-similarity. The resulting implication that self similarity and heavy tails are primarily due to server-nodes, rather than being inherent in o ered traÆc, leads to the possibility of using conventional queueing network models of performance. This idea is further supported by an additional simulation experiment and suitable models are proposed

Exploration of the network spun by website users

Using data stretching over more than 5 years for the website http://gallery.future-i.com/ this paper investigates basic properties of the popularity of pictures and the way users navigate through the website. We find that the rank frequency plot of the downloaded pictures follows a Zipf law. The download rate of individual popular pictures over time resembles that seen of infection rates of diseases. The graph created by successive downloads of pictures shows a power law that does not change over different time periods. We discuss how our findings can be modelled and how they are of importance to website performance

Evaluating and Optimising Models of Network Growth

Published versio

InGaAsP/InP undercut mesa laser with planar polyimide passivation

An undercut mesa laser is fabricated on an n + -InP substrate using a single step liquid phase epitaxy growth process and a planar structure is obtained by using a polyimide filling layer. The lasers operate at fundamental transverse mode due to a scattering loss mechanism. Threshold currents of 18 mA and stable single transverse mode operating at high currents are obtained

High-speed Schottky photodiode on semi-insulating GaAs

A high-speed GaAs photodiode has been fabricated on a GaAs semi-insulating substrate. The photodiode has an active area of 8 μm × 15 μm and a bandwidth in excess of 9 GHz. This Schottky photodiodes is suitable for monolithic integration with other optoelectronic components

Crystal structure of a ring-cleaving cyclohexane-1,2-dione hydrolase, a novel member of the thiamine diphosphate enzyme family

The thiamine diphosphate (ThDP) dependent flavoenzyme cyclohexane-1,2-dione hydrolase (CDH) (EC 3.7.1.11) catalyses a key step of a novel anaerobic degradation pathway for alicyclic alcohols by converting cyclohexane-1,2-dione (CDO) to 6-oxohexanoate and further to adipate using NAD(+) as electron acceptor. To gain insights into the molecular basis of these reactions CDH from denitrifying anaerobe Azoarcus sp. strain 22Lin was structurally characterized at 1.26 Å resolution. Notably, the active site funnel is rearranged in an unprecedented manner providing the structural basis for the specific binding and cleavage of an alicyclic compound. Crucial features include a decreased and displaced funnel entrance, a semi-circularly shaped loop segment preceding the C-terminal arm and the attachment of the C-terminal arm to other subunits of the CDH tetramer. Its structural scaffold and the ThDP activation is related to that observed for other members of the ThDP enzyme family. The selective binding of the competitive inhibitor 2-methyl-2,4-pentane-diol (MPD) to the open funnel of CDH reveals an asymmetry of the two active sites found also in the dimer of several other ThDP dependent enzymes. The substrate binding site is characterized by polar and non-polar moieties reflected in the structures of MPD and CDO and by three prominent histidine residues (His28, His31 and His76) that most probably play a crucial role in substrate activation. The NAD(+) dependent oxidation of 6-oxohexanoate remains enigmatic as the redox-active cofactor FAD seems not to participate in catalysis, and no obvious NAD(+) binding site is found. Based on the structural data both reactions are discussed