Effect of Thermal Undulations on the Bending Elasticity and Spontaneous Curvature of Fluid Membranes

We amplify previous arguments why mean curvature should be used as measure of integration in calculating the effective bending rigidity of fluid membranes subjected to a weak background curvature. The stiffening of the membrane by its fluctuations, recently derived for spherical shapes, is recovered for cylindrical curvature. Employing curvilinear coordinates, we then discuss stiffening for arbitrary shapes, confirm that the elastic modulus of Gaussian curvature is not renormalized in the presence of fluctuations, and show for the first time that any spontaneous curvature also remains unchanged.Comment: 26 pages, 2 figures, to appear in EPJ

A Capacity Supply Model for Virtualized Servers

This paper deals with determining the capacity supply for virtualized servers. First, a server is modeled as a queue based on a Markov chain. Then, the effect of server virtualization on the capacity supply will be analyzed with the distribution function of the server load.Markov chain, Weibull distribution, server, capacity supply

Getting access to the self: Effects of self-management therapy on the development of self-regulation and inhibitory control in obese adolescents

Background and aims: This study investigated the role of self-regulation competencies in general and specifically in a food-related context for the control of body weight in a three-year weight loss program. Methods: The sample consisted of 30 male and female adolescents (age range: 11–18 years) who participated in a three-year therapy program for severe obesity (mean BMI at the beginning of the intervention was 33.6). Assessment of self-regulation competencies was conducted at three different stages (1st–3rd graduation/class year). Therefore, three independent groups of adolescents (N = 10) at these different stages were tested (initial-to final-stage of therapy). At the time of testing the BMI of these groups significantly differed from 38.8 to 28.7. Analyses of covariance were performed to determine whether the adolescents also differed in self-regulation skills like “resistance to temptation” and food-related Stroop interference along with ameliorating their energy-balance regulation. Results: In addition to the main effects of age and body mass index, adolescents further displayed significant improvements of executive functions with respect to resistance to temptation and inhibition. Conclusions: Interventions aimed at enhancing energy-balance regulation in adolescents may further benefit from efforts to facilitate executive functions such as self-regulation and food-related cognitive inhibition

Interacting Crumpled Manifolds: Exact Results to all Orders of Perturbation Theory

In this letter, we report progress on the field theory of polymerized tethered membranes. For the toy-model of a manifold repelled by a single point, we are able to sum the perturbation expansion in the strength g of the interaction exactly in the limit of internal dimension D -> 2. This exact solution is the starting point for an expansion in 2-D, which aims at connecting to the well studied case of polymers (D=1). We here give results to order (2-D)^4, where again all orders in g are resummed. This is a first step towards a more complete solution of the self-avoiding manifold problem, which might also prove valuable for polymers.Comment: 8 page

Livro Digital Comemorativo aos 70 anos do ICBNA: as novas tecnologias preservando a história da inserção cultural estadunidense em Porto Alegre

Este artigo apresenta o processo criacional do livro digital comemorativo aos 70 anos do Instituto Cultural Brasileiro Norte-Americano - ICBNA. O texto atenta para a diversidade de fontes da instituição e como as mesmas foram adaptadas a “era digital”, buscando contribuir com a historiografia acerca do tema, revelando não apenas como se deu o processo de inserção cultural estadunidense na capital, mas também como a cultura e as novas tecnologias podem andar lado a lado na construção do conhecimento histórico e na preservação do patrimônio cultural.Sem bols

A Capacity Supply Model for Virtualized Servers

This paper deals with determining the capacity supply for virtualized servers. First, a server is modeled as a queue based on a Markov chain. Then, the effect of server virtualization on the capacity supply will be analyzed with the distribution function of the server load

Interacting crumpled manifolds

In this article we study the effect of a delta-interaction on a polymerized membrane of arbitrary internal dimension D. Depending on the dimensionality of membrane and embedding space, different physical scenarios are observed. We emphasize on the difference of polymers from membranes. For the latter, non-trivial contributions appear at the 2-loop level. We also exploit a ``massive scheme'' inspired by calculations in fixed dimensions for scalar field theories. Despite the fact that these calculations are only amenable numerically, we found that in the limit of D to 2 each diagram can be evaluated analytically. This property extends in fact to any order in perturbation theory, allowing for a summation of all orders. This is a novel and quite surprising result. Finally, an attempt to go beyond D=2 is presented. Applications to the case of self-avoiding membranes are mentioned

Phase structure of intrinsic curvature models on dynamically triangulated disk with fixed boundary length

A first-order phase transition is found in two types of intrinsic curvature models defined on dynamically triangulated surfaces of disk topology. The intrinsic curvature energy is included in the Hamiltonian. The smooth phase is separated from a non-smooth phase by the transition. The crumpled phase, which is different from the non-smooth phase, also appears at sufficiently small curvature coefficient $\alpha$. The phase structure of the model on the disk is identical to that of the spherical surface model, which was investigated by us and reported previously. Thus, we found that the phase structure of the fluid surface model with intrinsic curvature is independent of whether the surface is closed or open.Comment: 9 pages with 10 figure

The one-loop elastic coefficients for the Helfrich membrane in higher dimensions

Using a covariant geometric approach we obtain the effective bending couplings for a 2-dimensional rigid membrane embedded into a $(2+D)$-dimensional Euclidean space. The Hamiltonian for the membrane has three terms: The first one is quadratic in its mean extrinsic curvature. The second one is proportional to its Gaussian curvature, and the last one is proportional to its area. The results we obtain are in agreement with those finding that thermal fluctuations soften the 2-dimensional membrane embedded into a 3-dimensional Euclidean space.Comment: 9 page