Degree-constrained decompositions of graphs: Bounded treewidth and planarity

We study the problem of decomposing the vertex set V$V$ of a graph into two nonempty parts _V1,_V2$V_1,V_2$ which induce subgraphs where each vertex v∈_V1$v\in V_1$ has degree at least a(v)$a(v)$ inside _V1$V_1$ and each v∈_V2$v\in V_2$ has degree at least b(v)$b(v)$ inside _V2$V_2$. We give a polynomial-time algorithm for graphs with bounded treewidth which decides if a graph admits a decomposition, and gives such a decomposition if it exists. This result and its variants are then applied to designing polynomial-time approximation schemes for planar graphs where a decomposition does not necessarily exist but the local degree conditions should be met for as many vertices as possible.     

Degenerative process and cell death in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged female exposed to the acaricide permethrin

Ticks are ectoparasites of great medical and veterinary importance around the world and synthetic chemicals such as permethrin have been used for their control. This study provides a cytochemistry analysis of both degenerative and cell death processes in salivary glands of the brown dog tick Rhipicephalus sanguineus semi-engorged females exposed to 206, 1,031, and 2,062 ppm of permethrin. The results presented herein demonstrate that permethrin is a potent chemical acaricide that would act on the glandular tissue's morphophysiology in this tick species by eliciting severe changes in the acinus shape, intense vacuolation of the acinar cells' cytoplasm, marked glandular tissue disorganization, culminating in an advanced degenerative stage with consequent formation of many apoptotic bodies (cell death). In addition, permethrin induced major changes in the acinar cells' nucleus, such as a change both in its shape and size, chromatin marginalization, nuclear fragmentation, and appearance of picnotic nuclei, especially when the highest concentrations of the product were used. Thus, permethrin induced early degeneration of this tissue characterized by significant changes in the structure of acinar cells and production of enzymes related to the cell death process, in addition to interfering directly in the genetic material of these cells.     

Influences of the insertion method in glass ionomer cement porosity

The aim of this study was to evaluate the presence of porosities inside the glass ionomer cement (GIC) after different techniques of material insertion. MATERIAL AND METHOD: Specimens were prepared with high‐viscosity GIC Ketac Molar Easymix and divided into three groups according to the insertion method: spatula (PI), Centrix injector (CI), and low‐cost syringe (LCS). The specimens were fractured and observed with scanning electronic microscopy to quantitatively evaluate porosity inside the material using Image J Software. RESULTS: Statistical analysis, ANOVA application, and Tukey test to significance level of 5%, revealed that there was no statistical difference between the groups. CONCLUSION: Although the use of LCS has not decreased the porosity of the material, this insertion method is easy, accessible, and low cost, which makes it a viable alternative of use in the ART technique and in others bucal health programs. Microsc. Res. Tech., 2012. © 2012 Wiley Periodicals, Inc.     

A note on stabilization of locally damped wave equations with time delay

In this paper, we consider the wave equation with internal distributed time delay and local damping in a bounded and smooth domain Ω⊂Rⁿ. When the local damping acts on a neighborhood of a suitable part of the boundary of Ω, we show that an exponential stability result holds if the coefficient of the delay term is sufficiently small.     

Parallel option pricing on GPU: barrier options and realized variance options

This paper shows two examples of how the analysis of option pricing problems can lead to computational methods efficiently implemented in parallel. These computational methods outperform ??general purpose?? methods (i.e., for example, Monte Carlo, finite differences methods). The GPU implementation of two numerical algorithms to price two specific derivatives (continuous barrier options and realized variance options) is presented. These algorithms are implemented in CUDA subroutines ready to run on Graphics Processing Units (GPUs) and their performance is studied. The realization of these subroutines is motivated by the extensive use of the derivatives considered in the financial markets to hedge or to take risk and by the interest of financial institutions in the use of state of the art hardware and software to speed up the decision process. The performance of these algorithms is measured using the (CPU/GPU) speed up factor, that is using the ratio between the (wall clock) times required to execute the code on a CPU and on a GPU. The choice of the reference CPU and GPU used to evaluate the speed up factors presented is stated. The outstanding performance of the algorithms developed is due to the mathematical properties of the pricing formulae used and to the ad hoc software implementation. In the case of realized variance options when the computation is done in single precision the comparisons between CPU and GPU execution times gives speed up factors of the order of a few hundreds. For barrier options, the corresponding speed up factors are of about fifteen, twenty. The CUDA subroutines to price barrier options and realized variance options can be downloaded from the website http://www.econ.univpm.it/recchioni/finance/w13. A?more general reference to the work in mathematical finance of some of the authors and of their coauthors is the website http://www.econ.univpm.it/recchioni/finance/.     

On the differential benchmarking of promotional efficiency with machine learning modelling (II): Practical applications

The assessment of promotional sales with models constructed by machine learning techniques is arousing interest due, among other reasons, to the current economic situation leading to a more complex environment of simultaneous and concurrent promotional activities. An operative model diagnosis procedure was previously proposed in the companion paper, which can be readily used both for agile decision making on the architecture and implementation details of the machine learning algorithms, and for differential benchmarking among models. In this paper, a detailed example of model analysis is presented for two representative databases with different promotional behaviour, namely, a non-seasonal category (milk) and a heavily seasonal category (beer). The performance of four well-known machine learning techniques with increasing complexity is analyzed in detail here. In particular, k-Nearest Neighbours, General Regression Neural Networks, Multilayer Perceptron (MLP), and Support Vector Machines (SVM), are differentially compared. Present paper evaluates these techniques along the experiments described for both categories when applying the methodological findings obtained in the companion paper. We conclude that some elements included in the architecture are not essential for a good performance of the machine learning promotional models, such as the semiparametric nature of the kernel in SVM models, whereas other can be strongly dependent of the database, such as the convenience of multiple output models in MLP regression schemes. Additionally, the specificity of the behaviour of certain categories and product ranges determines the need to establish suitable and specific procedures for a better prediction and feature extraction.     

A survey of QoS architectures

Over the past several years there has been a considerable amount of research within the field of quality-of-service (QoS) support for distributed multimedia systems. To date, most of the work has been within the context of individual architectural layers such as the distributed system platform, operating system, transport subsystem and network layers. Much less progress has been made in addressing the issue of overall end-to-end support for multimedia communications. In recognition of this, a number of research teams have proposed the development of QoS architectures which incorporate QoS-configurable interfaces and QoS driven control and management mechanisms across all architectural layers. This paper examines the state-of-the-art in the development of QoS architectures. The approach taken is to present QoS terminology and a generalized QoS framework for understanding and discussing QoS in the context of distributed multimedia systems. Following this, we evaluate a number of QoS architectures that have emerged in the literature.     

A Peer-to-Peer Approach to Web Service Discovery

Web Services are emerging as a dominant paradigm for constructing and composing distributed business applications and enabling enterprise-wide interoperability. A critical factor to the overall utility of Web Services is a scalable, flexible and robust discovery mechanism. This paper presents a Peer-to-Peer (P2P) indexing system and associated P2P storage that supports large-scale, decentralized, real-time search capabilities. The presented system supports complex queries containing partial keywords and wildcards. Furthermore, it guarantees that all existing data elements matching a query will be found with bounded costs in terms of number of messages and number of nodes involved. The key innovation is a dimension reducing indexing scheme that effectively maps the multidimensional information space to physical peers. The design and an experimental evaluation of the system are presented.     

Fine structure of the male accessory glands of Triatoma rubrofasciata (De Geer, 1773) (Hemiptera, Triatominae)

Male of Triatoma rubrofasciata has four elongated sac-like reproductive mesodermic accessory glands, lined by an inner single layer of secretory cells, with basal plasma membrane infolds and short apical microvilli, and externally enveloped by a thin visceral muscle layer. The secretory cells have a well-developed rough endoplasmic reticulum, Golgi complex, mitochondria, and secretory granules. In one day old adult the gland cells are poorly developed, presenting small, electron-transparent secretory granules scattered among the rough endoplasmatic reticulum, whereas in three days old adult these cells have the cisternae of the rough endoplasmatic reticulum varing size degree, filled with granular electrondense content. In five days old males the secretory granules increase in diameter, being released to the gland lumen. Therefore, there is an increase of the secretory activity according to male maturation.