The metallicity dependence of the Cepheid period-luminosity (PL) relation has been a controversial issue. The more commonly accepted view is that the PL relation is insensitive to metal abundance, while the period-luminosity-colour relation is fairly sensitive, as indicated by stellar pulsation models 1−4 (see also refs. 5,6). The direct observational evidence is scanty, however. Freedman and M...

FEAST, an ongoing study of the role of feedback in the software process, was prompted by various factors including the need to identify the mechanisms underpinning observed phenomena in a series of metrics-based studies of evolving software systems conducted during the seventies and eighties. Evidence to date indicates that feedback loop mechanisms play significant role in determining the perfo...

Processor technology is still dramatically advancing and promises further enormous improvements in processing data for the next decade. In contrast, much lower advances in moving data are expected such that the efficiency of many numerical software tools for Partial Differential Equations (PDEs) is restricted by the cost for memory access. In last year’s Research Report [7] we outlined the nume...

During the last years, tremendous progress has been achieved in the development of methods for a posteriori error control and grid adaptation related to numerical methods for solving Partial Differential Equations (PDEs). It turned out that sophisticated adaptivity techniques are a key ingredient for fast and reliable numerical simulations. Hereby, the emphasis has been put on methods utilising...

Arterial spin labeling (ASL) perfusion imaging provides direct and absolute measurement of cerebral blood flow (CBF). Arterial transit time is a related physiological parameter reflecting the duration for the labeled spins to reach the brain region of interest. Most of the existing ASL approaches to assess arterial transit time rely on multiple measurements at various postlabeling delay times, ...

This paper describes a high-level System Dynamics model of a real-world software evolution process. This process is evolving the kernel (low-level routines) of VME, the operating system of a long-lived and successful series of ICL mainframe computers. The model has been developed as part of the continuing FEAST project, which is investigating the role and impact of feedback in the global softwa...

Simulation-based education has gained popularity, yet many faculty members feel inadequately prepared to teach using this technique. Fellowship training in medical education exists, but there is little information regarding simulation or formal educational programs therein. In our institution, simulation fellowships were offered by individual clinical departments. We recognized the need for a f...

Feature learning forms the cornerstone for tackling challenging learning problems in domains such as speech, computer vision and natural language processing. In this paper, we build upon a novel framework called FEAST(Feature ExtrAction using Score function Tensors) which incorporates generative models for discriminative learning. FEAST considers a novel class of matrix and tensor-valued featur...

Guanosine 3',5'-bispyrophosphate (ppGpp), also known as "magic spot," has been shown to bind prokaryotic RNA polymerase to down-regulate ribosome production and increase transcription of amino acid biosynthesis genes during the stringent response to amino acid starvation. Because many environmental growth perturbations cause ppGpp to accumulate, we hypothesize ppGpp to have an overarching role ...

Context. The luminous Galactic Cepheid RS Puppis is unique in being surrounded by a dust nebula illuminated by the variable light of the Cepheid. In a recent paper in this journal, Kervella et al. (2008) report a very precise geometric distance to RS Pup, based on measured phase lags of the light variations of individual knots in the reflection nebula. Aims. In this commentary, we examine the v...