Journal Articles on Category: Mathematics and Statistics

The problem of protein structure prediction is one of the long-standing goals of Computational Biology. Although we are still not able to provide first principle solutions, several shortcuts have been discovered to compute the protein three-dimensional structure when similar protein sequences are available (by means of comparative modeling and remote homology detection). Nonetheless, these approaches can assign structures only to a fraction of proteins in genomes and ab-initio methods are still needed. One relevant step of ab-initio prediction methods is the reconstruction of the protein structures starting from inter-protein residue contacts. In this paper we review the methods developed so far to accomplish the reconstruction task in order to highlight their differences and similarities. The different approaches are fully described and their reported performances, together with their computational complexity, are also discussed.

Issn:19994893

Keywords: Protein folding ; contact map ; molecular modeling

Volume: 2

Pages: 76-92

In the last decade, governments around the world have been working to capture the vast potential of the Internet to improve government processes. However, the success of these efforts depends, to a great extent, on how well the targeted users for such services, citizens in general, make use of them. Even e-government brings a certain level of transparency and offers good scope for innovative ways of servicing, some people remain suspicious of IT use in relation with government. For this reason, the purpose of the presented study was to identify what factors could affect the citizens’ trust in e government services. The study was conducted by surveying 793 citizens from all Romanian regions. The findings indicate that citizen’s higher perception of technological and organisational trustworthiness, the quality and usefulness of e government services, the Internet experience and propensity to trust, directly enhanced the trust in e-government. Opposite, age and privacy concerns have a negative influence over trust.

Issn:18424562

Keywords: trust ; e-government ; information technologies ; trusting factors

Volume: 4

Pages: 31-44

Eyvind Wichmann and I were both graduate students at Columbia University in the fifties, a decade of remarkable creativity by a star-studded physics faculty, which included some ten Nobel Laureates. I share some reminiscences about our time there and explain the role played in our relationship by an eightball.

Issn:10726691

Keywords: Eyvind Wichmann ; Columbia University ; Nobel Laureates ; eightball ; billiard ball.

Volume: Conference

Pages: 197-206

We study the boundary symmetries of models of nonequilibrium physics where the steady state behaviour strongly depends on the boundary rates. Within the matrix product state approach to many-body systems the physics is described in terms of matrices defining a noncommutative space with a quantum group symmetry. Boundary processes lead to a reduction of the bulk symmetry. We argue that the boundary operators of an interacting system with simple exclusion generate a tridiagonal algebra whose irreducible representations are expressed in terms of the Askey-Wilson polynomials. We show that the boundary algebras of the symmetric and the totally asymmetric processes are the proper limits of the partially asymmetric ones. In all three type of processes the tridiagonal algebra arises as a symmetry of the boundary problem and allows for the exact solvability of the model.

Issn:18150659

Keywords: driven many-body systems ; nonequilibrium ; tridiagonal algebra ; Askey-Wilson polynomials

Volume: 4

Pages: 056

This paper deals with the applications of the method of semidiscretization in time to a nonlinear retarded differential equation with a nonlocal history condition. We establish the existence and uniqueness of a strong solution. Finally, we consider some applications of the abstract results.

Issn:01611712

Keywords:

Volume: 2004

Pages: 1943-1956

The chromatic sum of a graph is the smallest sum of colors among all proper colorings with natural numbers. The strength of a graph is the minimum number of colors necessary to obtain its chromatic sum. A natural generalization of chromatic sum is optimum cost chromatic partition (OCCP) problem, where the costs of colors can be arbitrary positive numbers. Existing results about chromatic sum, strength of a graph, and OCCP problem are presented together with some recent developments. The focus is on polynomial algorithms for some families of graphs and NP-completeness issues.

Issn:01611712

Keywords:

Volume: 2004

Pages: 1563-1573

In this paper we study the Hopf bifurcation for the tumor-immune system model with one delay. This model is governed by a system of two differential equations with one delay. We show that the system may have periodic solutions for small and large delays for some critical value of the delay parameter via Hopf bifurcation theorem bifurcating from the non trivial steady state.

Issn:10726691

Keywords: Tumor-Immune system competition ; delayed differential equations ; stability ; Hopf bifurcation ; periodic solutions.

Volume: Conference

Pages: 241-248

Of concern are suspension flows. These combine directed and random motions and are typically modelled by parabolic partial differential equations. Sometimes they can be better modelled (in terms of fitting the data generated by certain blood flow experiments) by hyperbolic equations, such as the telegraph equation, which have parabolic (or analytic) asymptotics.

Issn:10726691

Keywords: Suspensions ; telegraph equation ; Kac random walk ; semigroups of operators ; asymptotic analyticity ; Taylor dispersion ; furth-Ornstein-Taylor formula.

Volume: Conference

Pages: 39-50

The gradient flow approach to the Cahn-Hilliard and phase field models is developed, and some basic mathematical properties of the models, especially phase separation phenomena, are reviewed.

Issn:10726691

Keywords: Cahn-Hilliard equation ; phase-field equations ; phase separation ; gradient flows.

Volume: 2000

Pages: 1-26

Mathematics plays a major role in contemporary fisheries management. Stock assessments often depend on elaborate models used to set catch levels and address other policy objectives. In recent years, the collapse of various important fish stocks has caused some critics to suggest that mathematical models actually obscure the truth by narrowing scientific understanding to the realm of quantifiable events. In the words of one fisherman, ``Mathematics has highjacked the definition and position of real science.' In this paper, I present a number of typical fishery models, examine their limitations, discuss controversies about their use, and explore possible alternatives. I draw on examples from economics and investment theory to illustrate the problem of making credible predictions about an uncertain future. The constraints of the real world, where people care deeply about policy consequences, have altered my scientific perspective as an applied mathematician. This paper reflects the evolution of thought that has accompanied my experience working for 28 years at the Pacific Biological Station in Nanaimo, B.C., the host city for this conference.

Issn:10726691

Keywords: Fishery models ; state space models ; statistical decisions.

Volume: Conference

Pages: 143-158