Spectrum of Sizes for Perfect Deletion-Correcting Codes

One peculiarity with deletion-correcting codes is that perfect $t$-deletion-correcting codes of the same length over the same alphabet can have different numbers of codewords, because the balls of radius $t$ with respect to the Levenshte\u{\i}n distance may be of different sizes. There is interest, therefore, in determining all possible sizes of a perfect $t$-deletion-correcting code, given the length $n$ and the alphabet size~$q$. In this paper, we determine completely the spectrum of possible sizes for perfect $q$-ary 1-deletion-correcting codes of length three for all $q$, and perfect $q$-ary 2-deletion-correcting codes of length four for almost all $q$, leaving only a small finite number of cases in doubt.Comment: 23 page

On Secure Workflow Decentralisation on the Internet

Decentralised workflow management systems are a new research area, where most work to-date has focused on the system's overall architecture. As little attention has been given to the security aspects in such systems, we follow a security driven approach, and consider, from the perspective of available security building blocks, how security can be implemented and what new opportunities are presented when empowering the decentralised environment with modern distributed security protocols. Our research is motivated by a more general question of how to combine the positive enablers that email exchange enjoys, with the general benefits of workflow systems, and more specifically with the benefits that can be introduced in a decentralised environment. This aims to equip email users with a set of tools to manage the semantics of a message exchange, contents, participants and their roles in the exchange in an environment that provides inherent assurances of security and privacy. This work is based on a survey of contemporary distributed security protocols, and considers how these protocols could be used in implementing a distributed workflow management system with decentralised control . We review a set of these protocols, focusing on the required message sequences in reviewing the protocols, and discuss how these security protocols provide the foundations for implementing core control-flow, data, and resource patterns in a distributed workflow environment

A critical review on modelling formalisms and simulation tools in computational biosystems

Integration of different kinds of biological processes is an ultimate goal for whole-cell modelling. We briefly review modelling formalisms that have been used in Systems Biology and identify the criteria that must be addressed by an integrating framework capable of modelling, analysing and simulating different biological networks. Aware that no formalism can fit all purposes we realize Petri nets as a suitable model for Metabolic Engineering and take a deeper perspective on the role of this formalism as an integrating framework for regulatory and metabolic networks.Research supported by PhD grant SFRH/BD/35215/2007 from the Fundacao para a Ciencia e a Tecnologia (FCT) and the MIT-Portugal program

The structure of the phenol-nitrogen cluster. A joint experimental and ab initio study

Contains fulltext : 59287.pdf (publisher's version ) (Open Access

Rotational isomers of hydroxy deuterated o- and m-cresols studied by ultraviolet high resolution experiments

Contains fulltext : 32948.pdf (author's version ) (Open Access)The laser induced fluorescence spectra of several torsional transitions of the S-1 ← S-0 electronic transition were recorded for the hydroxy deuterated o- and m- cresols. Both cis and trans rotamers were observed in a high resolution molecular beam experiment. The spectra were analyzed using a genetic algorithm assisted automatic assignment. The Hamiltonian used included rotational, torsional and rotation - torsion components. Both, high resolution rotationally resolved spectra and low resolution torsional frequencies, were combined to obtain the rotational constants, the direction of the methyl group axis, and the V-3 and V-6 barriers to internal rotation of the methyl top in the ground (S-0) and excited (S-1) states. The lifetime of the S-1 state is also reported. Quantum interference effects due to the interaction of the internal and overall rotation allowed for determination of the absolute sign of the angle between transition moment and the a principal axis

The structure of 4-methylphenol and its water cluster revealed by rotationally resolved UV spectroscopy using a genetic algorithm approach

Contains fulltext : 33146.pdf (publisher's version ) (Open Access)The structure of 4-methylphenol (p-cresol) and its binary water cluster have been elucidated by rotationally resolved laser-induced fluorescence spectroscopy. The electronic origins of the monomer and the cluster are split into four sub-bands by the internal rotation of the methyl group and of the hydroxy group in case of the monomer, and the water moiety in case of the cluster. From the rotational constants of the monomer the structure in the S-1 state could be determined to be distorted quinoidally. The structure of the p-cresol-water cluster is determined to be trans linear, with a O-O hydrogen bond length of 290 pm in the electronic ground state and of 285 pm in the electronically excited state. The S-1-state lifetime of p-cresol, p-cresol-d(1), and the binary water cluster have been determined to be 1.6, 9.7, and 3.8 ns, respectively. (C) 2005 American Institute of Physics

Structure and barrier to internal rotation of 4-methylstyrene in the S-0- and S-1-state

Contains fulltext : 33020.pdf (publisher's version ) (Closed access)The rotationally resolved spectrum of the electronic origin of methylstyrene has been studied in order to obtain the geometric structure and the barriers to methyl torsion in the electronic ground and excited state. The spectrum has been analyzed using an automated assignment based on the Genetic Algorithm. The geometry is found to be quinoidally distorted upon electronic excitation, what is typical for para-disubstituted aromatic compounds. The V-3 and V-6 barriers and the torsional constant F for both electronic states have been determined from a combined fit of low resolution torsional bands and high resolution torsionally perturbed rovibronic spectrum. © 2005 Elsevier B.V. All rights reserved