Hardware reduction in digital delta-sigma modulators via error masking - part I: MASH DDSM

Two classes of techniques have been developed to whiten the quantization noise in digital delta-sigma modulators (DDSMs): deterministic and stochastic. In this two-part paper, a design methodology for reduced-complexity DDSMs is presented. The design methodology is based on error masking. Rules for selecting the word lengths of the stages in multistage architectures are presented. We show that the hardware requirement can be reduced by up to 20% compared with a conventional design, without sacrificing performance. Simulation and experimental results confirm theoretical predictions. Part I addresses MultistAge noise SHaping (MASH) DDSMs; Part II focuses on single-quantizer DDSMs..

Finite size effects in the presence of a chemical potential: A study in the classical nonlinear O(2) sigma model

In the presence of a chemical potential, the physics of level crossings leads to singularities at zero temperature, even when the spatial volume is finite. These singularities are smoothed out at a finite temperature but leave behind nontrivial finite size effects which must be understood in order to extract thermodynamic quantities using Monte Carlo methods, particularly close to critical points. We illustrate some of these issues using the classical nonlinear O(2) sigma model with a coupling β and chemical potential μ on a 2+1-dimensional Euclidean lattice. In the conventional formulation this model suffers from a sign problem at nonzero chemical potential and hence cannot be studied with the Wolff cluster algorithm. However, when formulated in terms of the worldline of particles, the sign problem is absent, and the model can be studied efficiently with the "worm algorithm." Using this method we study the finite size effects that arise due to the chemical potential and develop an effective quantum mechanical approach to capture the effects. As a side result we obtain energy levels of up to four particles as a function of the box size and uncover a part of the phase diagram in the (β,μ) plane. © 2010 The American Physical Society.

Alternative transcription factor sigma(B) is involved in regulation of biofilm expression in a Staphylococcus aureus mucosal isolate.

Rachid S, Ohlsen K, Wallner U, Hacker J, Hecker M, Ziebuhr W. Institut für Molekulare Infektionsbiologie, D-97070 Würzburg, Germany. Osmotic stress was found to induce biofilm formation in a Staphylococcus aureus mucosal isolate. Inactivation of a global regulator of the bacterial stress response, the alternative transcription factor sigma(B), resulted in a biofilm-negative phenotype and loss of salt-induced biofilm production. Complementation of the mutant strain with an expression plasmid encoding sigma(B) completely restored the wild-type phenotype. The combined data suggest a critical role of sigma(B) in S. aureus biofilm regulation under environmental stress conditions.

The alternative sigma factor sigma B of Staphylococcus aureus modulates virulence in experimental central venous catheter-related infections.

The impact of the alternative sigma factor sigma B (SigB) on pathogenesis of Staphylococcus aureus is not conclusively clarified. In this study, a central venous catheter (CVC) related model of multiorgan infection was used to investigate the role of SigB for the pathogenesis of S. aureus infections and biofilm formation in vivo. Analysis of two SigB-positive wild-type strains and their isogenic mutants revealed uniformly that the wild-type was significantly more virulent than the SigB-deficient mutant. The observed difference in virulence was apparently not linked to the capability of the strains to form biofilms in vivo since wild-type and mutant strains were able to produce biofilm layers inside of the catheter. The data strongly indicate that the alternative sigma factor SigB plays a role in CVC-associated infections caused by S. aureus.

Lean software management case study: Timberline Inc.

This paper is believed to be the first documented account of a full adoption of lean by a software company. Lean techniques were devised by Toyota and other manufacturers over the last 50 years. The techniques are termed lean because they require less resource to produce more product and exceptional quality. Lean ideas have also been successful in service industries and product development. Applying lean to software has been advocated for over 10 years. Timberline, Inc started their lean initiative in Spring 2001 and this paper records their journey, results and lessons learned up to Fall 2003. This case study demonstrates that lean thinking can work successfully for software developers. It also indicates that the extensive lean literature is a valuable source of new ideas for software engineering.

Lean software process

This paper shows how the concepts of lean manufacturing can be successfully applied to software development. The key lean concept is to have a minimum of work in progress, which forces problems into the open. The time is then taken to fix the production system so the errors will not occur again.

Lean principles and techniques for improving the quality and productivity of software development projects: a case study

Software product development is recognised as difficult due to the intangible nature of the product, requirements elicitation, effective progress measurement, and so forth. In this paper, we describe some of the challenges of software product development and how the challenges are being met by lean management principles and techniques. Specifically, we examine lean principles and techniques that were devised by Toyota and other manufacturers over the last 50 years. Applying lean principles to software development projects has been advocated for over ten years and it will be shown that the extensive lean literature is a valuable source of ideas for software development. A case study with a software development organisation, Timberline Inc., will demonstrate that lean principles and techniques can be successfully applied to software product development.

A review of the selective reduction of NOx, with hydrocarbons under lean-burn conditions with non-zeolitic oxide and platinum group metal catalysts

Research on the selective reduction of NOx with hydrocarbons under lean-burn conditions using non-zeolitic oxides and platinum group metal (PGM) catalysts has been critically reviewed. Alumina and silver-promoted alumina catalysts have been described in detail with particular emphasis on an analysis of the various reaction mechanisms that have been put forward in the literature. The influence of the nature of the reducing agent, and the preparation and structure of the catalysts have also been discussed and rationalised for several other oxide systems. It is concluded for non-zeolitic oxides that species that are strongly adsorbed on the surface, such as nitrates/nitrites and acetates, could be key intermediates in the formation of various reduced and oxidised species of nitrogen, the further reaction of which leads eventually to the formation of molecular nitrogen. For the platinum group metal catalysts, the different mechanisms that have been proposed in the literature have been critically assessed. It is concluded that although there is indirect, mainly spectroscopic, evidence for various reaction intermediates on the catalyst surface, it is difficult to confirm that any of these are involved in a critical mechanistic step because of a lack of a direct quantitative correlation between infrared and kinetic measurements. A simple mechanism which involves the dissociation of NO on a reduced metal surface to give N(ads) and O(ads), with subsequent desorption of N-2 and N2O and removal of O(ads) by the reductant can explain many of the results with the platinum group metal catalysts, although an additional contribution from organo-nitro-type species may contribute to the overall NOx reduction activity with these catalysts.

An investigation of catalysts for the on board synthesis of NH3. A possible route to low temperature NOx reduction for lean-burn engines

Platinum group metal catalysts have been investigated for the formation of NH3 from NO + H-2 at low temperatures in the absence and presence of CO. Although CO inhibits the formation of NH3, substantial amounts are still observed with a Pt catalyst. By combining Pt with a support (ceria-zirconia) that has low temperature NOx storage characteristics it has been shown in transient experiments that NH3 can be formed and stored in situ under rich conditions, and may then be used to reduce NOx under lean burn conditions.