A stochastic network with mobile users in heavy traffic

We consider a stochastic network with mobile users in a heavy-traffic regime. We derive the scaling limit of the multi-dimensional queue length process and prove a form of spatial state space collapse. The proof exploits a recent result by Lambert and Simatos which provides a general principle to establish scaling limits of regenerative processes based on the convergence of their excursions. We also prove weak convergence of the sequences of stationary joint queue length distributions and stationary sojourn times.Comment: Final version accepted for publication in Queueing Systems, Theory and Application

Changes in Predicted Muscle Coordination with Subject-Specific Muscle Parameters for Individuals after Stroke

Muscle weakness is commonly seen in individuals after stroke, characterized by lower forces during a maximal volitional contraction. Accurate quantification of muscle weakness is paramount when evaluating individual performance and response to after stroke rehabilitation. The objective of this study was to examine the effect of subject-specific muscle force and activation deficits on predicted muscle coordination when using musculoskeletal models for individuals after stroke. Maximum force generating ability and central activation ratio of the paretic plantar flexors, dorsiflexors, and quadriceps muscle groups were obtained using burst superimposition for four individuals after stroke with a range of walking speeds. Two models were created per subject: one with generic and one with subject-specific activation and maximum isometric force parameters. The inclusion of subject-specific muscle data resulted in changes in the model-predicted muscle forces and activations which agree with previously reported compensation patterns and match more closely the timing of electromyography for the plantar flexor and hamstring muscles. This was the first study to create musculoskeletal simulations of individuals after stroke with subject-specific muscle force and activation data. The results of this study suggest that subject-specific muscle force and activation data enhance the ability of musculoskeletal simulations to accurately predict muscle coordination in individuals after stroke

Densidades, tamanho de grupo e reprodução de emas no Pantanal Sul.

Este estudo sobre a ecologia das emas no Pantanal foi uma primeira experiência na região, e teve o objetivo de avaliar as possibilidades de utilização da espécie nas fazendas do Pantanal da Nhecolândia. A população estimada, através de um levantamento aéreo, foi de 6.500 emas adultas, em todo o Pantanal. Na fazenda Nhumirim foram encontrados 73 grupos de emas durante o estudo, e o número de grupos variou ao longo do ano, de 2 a 17 indivíduos. A razão sexual foi de 1 macho para 3,6 fêmeas. Os ninhos foram feitos pelos machos, em áreas abertas e em áreas fechadas. Nos 2 anos do estudo foram encontrados 26 ninhos, e o número de ovos variou de 5 a 25. O principal predador dos ninhos foi o tatu-peba. A população de emas no Pantanal está bem conservada e existe possibilidade do uso sustentado da espécie.bitstream/item/37302/1/BP55.pd

Strong "quantum" chaos in the global ballooning mode spectrum of three-dimensional plasmas

The spectrum of ideal magnetohydrodynamic (MHD) pressure-driven (ballooning) modes in strongly nonaxisymmetric toroidal systems is difficult to analyze numerically owing to the singular nature of ideal MHD caused by lack of an inherent scale length. In this paper, ideal MHD is regularized by using a $k$-space cutoff, making the ray tracing for the WKB ballooning formalism a chaotic Hamiltonian billiard problem. The minimum width of the toroidal Fourier spectrum needed for resolving toroidally localized ballooning modes with a global eigenvalue code is estimated from the Weyl formula. This phase-space-volume estimation method is applied to two stellarator cases.Comment: 4 pages typeset, including 2 figures. Paper accepted for publication in Phys. Rev. Letter

Nogmaals Petersburg langs de Vecht. Een vergelijking tussen twee plattegronden voor deze buitenplaats uit de Collectie Beudeker en uit de Collectie van Peter de Grote

The Peter the Great Year 1996 / 1997 resulted in a renewed interest in Peter the Great's country houses in the Netherlands in 1696/1697 and 1716/1717 and the places and persons he visited at that time. On several occasions he stayed at the country estate Petersburg along the Vecht, owned by his friend Christoffel Brants. Brants even had a Russian bathing stove built for him. Consequently, it is not surprising that in 1717 Peter the Great received a floor plan (with buildings) of Petersburg as a gift from Brants. The well-known collector of prints, naturalia and antiquities Christoffel Beudeker also came into possession of a floor plan of Petersburg. In the article both these floor plans (a site drawing and a model drawing) are accurately compared with each other and also with the views of Petersburg published in the well-known book De Zegepralende Vecht by A. de Leth and D. Stopendaal (1719). The draft drawing of the ‘architect’ Simon Schijnvoet proves to contain quite extensive information on the dimensioning of the site and buildings. It appears that Schijnvoet still focused on the Renaissance masters and classics. He provided the mathematical layout of the site with buildings with dimensions according to the harmonious proportions of tierce and quint, analogous to those of measurable, visible forms. What lent Petersburg a truly and typically Dutch technical ingenuity is the musical ensemble of ornamental gardens, kitchen gardens, cultivation gardens and lanes, canals and quays, smoothly melting into one another in a harmonious way. The various parts of the country estate are subsequently discussed and it is concluded that the draft drawing almost entirely corresponds to the situation executed, contrary to the situation drawn on the ‘clean drawing’ or model drawing. The latter was mainly an ornamental drawing that was probably hanging in the house. Attention is also paid to the possible influence that the draft of the Netherlands Petersburg may have had on the situation of country estates along the banks of rivers and the Finnish Gulf in St. Petersburg (compared to the situation along the Vecht) and possibly also on the layout of the site of the country estate Dalniye Doebki, designed by the Dutchman Steven van Zwieten. Just as Petersburg this country estate is defined by water systems transecting the entire site. Finally, an aerial photograph shows that a number of 18th-century structures are still quite clearly present below ground level at the site of Petersburg, such as the transverse basin behind the house, the round basins, some canals and the sight avenue. A landscape archaeological research might provide certainty as regards any other possibly present remains. In case of a positive result a proposal to designate Petersburg as an archaeological monument would be more justified

Nogmaals Petersburg langs de Vecht. Een vergelijking tussen twee plattegronden voor deze buitenplaats uit de Collectie Beudeker en uit de Collectie van Peter de Grote

The Peter the Great Year 1996 / 1997 resulted in a renewed interest in Peter the Great's country houses in the Netherlands in 1696/1697 and 1716/1717 and the places and persons he visited at that time. On several occasions he stayed at the country estate Petersburg along the Vecht, owned by his friend Christoffel Brants. Brants even had a Russian bathing stove built for him. Consequently, it is not surprising that in 1717 Peter the Great received a floor plan (with buildings) of Petersburg as a gift from Brants. The well-known collector of prints, naturalia and antiquities Christoffel Beudeker also came into possession of a floor plan of Petersburg. In the article both these floor plans (a site drawing and a model drawing) are accurately compared with each other and also with the views of Petersburg published in the well-known book De Zegepralende Vecht by A. de Leth and D. Stopendaal (1719). The draft drawing of the ‘architect’ Simon Schijnvoet proves to contain quite extensive information on the dimensioning of the site and buildings. It appears that Schijnvoet still focused on the Renaissance masters and classics. He provided the mathematical layout of the site with buildings with dimensions according to the harmonious proportions of tierce and quint, analogous to those of measurable, visible forms. What lent Petersburg a truly and typically Dutch technical ingenuity is the musical ensemble of ornamental gardens, kitchen gardens, cultivation gardens and lanes, canals and quays, smoothly melting into one another in a harmonious way. The various parts of the country estate are subsequently discussed and it is concluded that the draft drawing almost entirely corresponds to the situation executed, contrary to the situation drawn on the ‘clean drawing’ or model drawing. The latter was mainly an ornamental drawing that was probably hanging in the house. Attention is also paid to the possible influence that the draft of the Netherlands Petersburg may have had on the situation of country estates along the banks of rivers and the Finnish Gulf in St. Petersburg (compared to the situation along the Vecht) and possibly also on the layout of the site of the country estate Dalniye Doebki, designed by the Dutchman Steven van Zwieten. Just as Petersburg this country estate is defined by water systems transecting the entire site. Finally, an aerial photograph shows that a number of 18th-century structures are still quite clearly present below ground level at the site of Petersburg, such as the transverse basin behind the house, the round basins, some canals and the sight avenue. A landscape archaeological research might provide certainty as regards any other possibly present remains. In case of a positive result a proposal to designate Petersburg as an archaeological monument would be more justified

Density-functional theory of inhomogeneous electron systems in thin quantum wires

Motivated by current interest in strongly correlated quasi-one-dimensional (1D) Luttinger liquids subject to axial confinement, we present a novel density-functional study of few-electron systems confined by power-low external potentials inside a short portion of a thin quantum wire. The theory employs the 1D homogeneous Coulomb liquid as the reference system for a Kohn-Sham treatment and transfers the Luttinger ground-state correlations to the inhomogeneous electron system by means of a suitable local-density approximation (LDA) to the exchange-correlation energy functional. We show that such 1D-adapted LDA is appropriate for fluid-like states at weak coupling, but fails to account for the transition to a ``Wigner molecules'' regime of electron localization as observed in thin quantum wires at very strong coupling. A detailed analyzes is given for the two-electron problem under axial harmonic confinement.Comment: 8 pages, 7 figures, submitte