Piston-ring film thickness: theory and experiment compared

A review of the published literature has demonstrated a large variability and discrepancies in the measured and predicted values of piston-ring lubricating film thickness in internal combustion engines. Only 2 papers have been found that compare experiments in firing engines directly with outputs from sophisticated ring-pack lubrication models. The agreement between theory and experiment in these comparisons was limited, possibly because of inadequacies in the models and/ or inaccuracies of measurement. This paper seeks to contribute to the literature by comparing accurately calibrated experimental measurements of piston-ring film thickness in a firing engine with predictions from an advanced, commercial software package alongside details of the systematic analysis of the measurement errors in this process. Suggestions on how measurement accuracy could be further improved are also given. Measurements of oil film thickness with an error (standard deviation) of +/-15% have been achieved. It is shown that this error can be reduced further, by changes in the design and installation of the sensors. Detailed experimental measurements of film thickness under the top compression ring in a firing petrol engine have been made and compared with the predictions from a commercial, state-of-the art modelling package. The agreement between theory and experiment is excellent throughout the stroke in most cases, but some significant differences are observed at the lower load conditions. These differences are as yet unexplained, but may be due to the sensor topography influencing the hydrodynamic lubrication, lubricant availability, out-of-roundness in the cylinder, or squeeze effects. This a topic that requires further stud

Four Fermion Field Theories and the Chern-Simons Field: A Renormalization Group Study

In (2+1) dimensions, we consider the model of a $N$ flavor, two-component fermionic field interacting through a Chern-Simons field besides a four fermion self-interaction which consists of a linear combination of the Gross-Neveu and Thirring like terms. The four fermion interaction is not perturbatively renormalizable and the model is taken as an effective field theory in the region of low momenta. Using Zimmerman procedure for reducing coupling constants, it is verified that, for small values of the Chern-Simons parameter, the origin is an infrared stable fixed point but changes to ultraviolet stable as $\alpha$ becomes bigger than a critical $\alpha_c$. Composite operators are also analyzed and it is shown that a specific four fermion interaction has an improved ultraviolet behavior as $N$ increases.Comment: 9 pages, revte

Effective Field Theory of Gravity, Reduction of Couplings and the Renormalization Group

The structure of the renormalization group equations for the low energy effective theory of gravity coupled to a scalar field is presented. An approximate solution to these equations with a finite number of independent renormalized parameters can be found when the mass scale characteristic of the fluctuations in the geometry is much smaller than the Planck mass. The cosmological constant problem is reformulated in this context and some conditions on the matter field content and interactions required in order to have a sufficiently small cosmological constant are identified.Comment: 24 pages, Late

Your space or mine? : Mapping self in time

Peer reviewedPublisher PD

Feline Leukemia Virus and Other Pathogens as Important Threats to the Survival of the Critically Endangered Iberian Lynx (Lynx pardinus)

BACKGROUND: The Iberian lynx (Lynx pardinus) is considered the most endangered felid species in the world. In order to save this species, the Spanish authorities implemented a captive breeding program recruiting lynxes from the wild. In this context, a retrospective survey on prevalence of selected feline pathogens in free-ranging lynxes was initiated. METHODOLOGY/ PRINCIPAL FINDINGS: We systematically analyzed the prevalence and importance of seven viral, one protozoan (Cytauxzoon felis), and several bacterial (e.g., hemotropic mycoplasma) infections in 77 of approximately 200 remaining free-ranging Iberian lynxes of the Doñana and Sierra Morena areas, in Southern Spain, between 2003 and 2007. With the exception of feline immunodeficiency virus (FIV), evidence of infection by all tested feline pathogens was found in Iberian lynxes. Fourteen lynxes were feline leukemia virus (FeLV) provirus-positive; eleven of these were antigenemic (FeLV p27 positive). All 14 animals tested negative for other viral infections. During a six-month period in 2007, six of the provirus-positive antigenemic lynxes died. Infection with FeLV but not with other infectious agents was associated with mortality (p<0.001). Sequencing of the FeLV surface glycoprotein gene revealed a common origin for ten of the eleven samples. The ten sequences were closely related to FeLV-A/61E, originally isolated from cats in the USA. Endogenous FeLV sequences were not detected. CONCLUSIONS/SIGNIFICANCE: It was concluded that the FeLV infection most likely originated from domestic cats invading the lynx's habitats. Data available regarding the time frame, co-infections, and outcome of FeLV-infections suggest that, in contrast to the domestic cat, the FeLV strain affecting the lynxes in 2007 is highly virulent to this species. Our data argue strongly for vaccination of lynxes and domestic cats in and around lynx's habitats in order to prevent further spread of the virus as well as reduction the domestic cat population if the lynx population is to be maintained

Neuroscience and education: prime time to build the bridge

As neuroscience gains social traction and entices media attention, the notion that education has much to benefit from brain research becomes increasingly popular. However, it has been argued that the fundamental bridge toward education is cognitive psychology, not neuroscience. We discuss four specific cases in which neuroscience synergizes with other disciplines to serve education, ranging from very general physiological aspects of human learning such as nutrition, exercise and sleep, to brain architectures that shape the way we acquire language and reading, and neuroscience tools that increasingly allow the early detection of cognitive deficits, especially in preverbal infants. Neuroscience methods, tools and theoretical frameworks have broadened our understanding of the mind in a way that is highly relevant to educational practice. Although the bridge’s cement is still fresh, we argue why it is prime time to march over it

Pathogen reduction/inactivation of products for the treatment of bleeding disorders:what are the processes and what should we say to patients?

Patients with blood disorders (including leukaemia, platelet function disorders and coagulation factor deficiencies) or acute bleeding receive blood-derived products, such as red blood cells, platelet concentrates and plasma-derived products. Although the risk of pathogen contamination of blood products has fallen considerably over the past three decades, contamination is still a topic of concern. In order to counsel patients and obtain informed consent before transfusion, physicians are required to keep up to date with current knowledge on residual risk of pathogen transmission and methods of pathogen removal/inactivation. Here, we describe pathogens relevant to transfusion of blood products and discuss contemporary pathogen removal/inactivation procedures, as well as the potential risks associated with these products: the risk of contamination by infectious agents varies according to blood product/region, and there is a fine line between adequate inactivation and functional impairment of the product. The cost implications of implementing pathogen inactivation technology are also considered

Les idées de Paul Valery sur l’histoire et sur la politique

Une étude, même assez sommaire, de l’oeuvre de Valéry révèle que le Valéry de la Jeune Parque ou celui de Monsieur Teste a beaucoup en commun avec le Valéry de “La Conquête allemande” ou “La Politique de l’esprit”. C’est parce qu’il nous a semblé voir ce parallèle dans les divers aspects de son oeuvre, que nous avons choisi pour sujet de cette thèse l’aspect politique, historique et social de l’oeuvre de Valéry. Abstract in English: Even such a brief study of Valéry’s works reveals that the Valéry of the Jeune Parque or that of Monsieur Teste has a lot in common with the Valéry of “La Conquête allemande” or “La Politique de l’esprit.” It is because of the parallels in the various aspects of his works that for the subject of this thesis we chose to study the political, historical and social aspects of Valéry’s works. Advisor: Reino Virtane

Les idées de Paul Valery sur l’histoire et sur la politique

Une étude, même assez sommaire, de l’oeuvre de Valéry révèle que le Valéry de la Jeune Parque ou celui de Monsieur Teste a beaucoup en commun avec le Valéry de “La Conquête allemande” ou “La Politique de l’esprit”. C’est parce qu’il nous a semblé voir ce parallèle dans les divers aspects de son oeuvre, que nous avons choisi pour sujet de cette thèse l’aspect politique, historique et social de l’oeuvre de Valéry. Abstract in English: Even such a brief study of Valéry’s works reveals that the Valéry of the Jeune Parque or that of Monsieur Teste has a lot in common with the Valéry of “La Conquête allemande” or “La Politique de l’esprit.” It is because of the parallels in the various aspects of his works that for the subject of this thesis we chose to study the political, historical and social aspects of Valéry’s works. Advisor: Reino Virtane