Testing high resolution ΣΔ ADC's by using the quantizer input as test access

A new solution to improve the testability of high resolution ΣΔ Analogue to Digital Converters (ΣΔ ADC's) using the quantizer input as test node is described. The theoretical basis for the technique is discussed and results from high level simulations for a 16 bit, fourth order, audio ADC are presented. The analysis demonstrates the potential to reduce the computational effort associated with test response analysis versus conventional techniques. If only SNR, THD and gain of the ΣΔ ADC are evaluated with the new proposed method the test time is already reduced by 20%.     

An analytical model of information dissemination for a gossip-based protocol

We develop an analytical model of information dissemination for a gossiping protocol that combines both pull and push approaches. With this model we analyse how fast an item is replicated through a network, and how fast the item covers the network. We also determine the optimal size of the exchange buffer, to obtain fast replication. Our results are confirmed by large-scale simulation experiments.     

Effect of hydrophilic–hydrophobic balance on biocompatibility of poly(methyl methacrylate) (PMMA)–hydroxyapatite (HA) composites

The purpose of this study is to put in evidence the correlation between hydrophilic/hydrophobic balance and biocompatibility of PMMA–HA composites, in order to select the best composites for futures clinical applications. For this purpose, PMMA–HA cements with different compositions were prepared and static contact angle measurements, water absorption and gingival fibroblasts cell culture were performed and discussed.     

Stress and memory retrieval in women: No strong impairing effect during the luteal phase.

Stress has been shown to impair delayed memory retrieval, but so far no study has been conducted solely with naturally cycling women. In a crossover design, 36 women (all in the luteal phase) participated in two experimental conditions (stress vs. control). Delayed memory retrieval of a wordlist learned 24 hours earlier was tested after stress or control treatment. Although stressed subjects showed a strong cortisol increase following stress, no influence on memory retrieval occurred. In an additional data analysis, subjects were split up into a cortisol responder and a cortisol nonresponder group. However, again no evidence for a stress-induced retrieval impairment became apparent. Similarly, no correlation was observed between the stress-induced cortisol increase and memory. This study failed to find an influence of stress on memory retrieval in women tested in the luteal phase. The findings are in contrast to our previous results obtained with men. Evidence is discussed that the luteal phase, which is characterized by elevated gonadal steroids, is associated with reduced glucocorticoid sensitivity. This might underlie the missing impact of stress on memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simulation of dynamic phenomena by cellular automata

This paper is aimed at showing how cellular automata can be conveniently employed to simulate dynamic phenomena, typically involving transportation, diffusion, or propagation problems. A cellular automaton can be viewed as made of two parts: a computational engine based on a proper discretization of the domain and charged with correctness and consistency controls, and a dynamic model constituted by transition functions that express cell behaviour. The adoption of cellular automata introduces a new means of spatial data modelling, in addition to those traditionally provided by GIS packages, resulting in the possibility of storing elements of dynamic knowledge in cellular maps: each cell is provided with the attributes that constitute its state, and groups of cells with the functions that describe their mutual interaction. The basic characteristics of cellular automata are discussed with reference to a significant application case, the study of tide propagation over a lagoon.     

Mass transfer coefficients for arranged packings with vertical walls under gas film control

Packings with vertical walls, especially structured packings, are distinguished by their high efficiency and low pressure drop per mass transfer unit. Yet for these types of packings there is still no universal relationship for calculating gas-film-controlled mass transfer coefficients. The present work proposes such an equation. For arranged and structured packings the new equation fits the experimental data, both new results and those taken from the literature, with a mean error of 9%.