Experimental Lagrangian Acceleration Probability Density Function Measurement

We report experimental results on the acceleration component probability distribution function at $R_\lambda = 690$ to probabilities of less than $10^{-7}$. This is an improvement of more than an order of magnitude over past measurements and allows us to conclude that the fourth moment converges and the flatness is approximately 55. We compare our probability distribution to those predicted by several models inspired by non-extensive statistical mechanics. We also look at acceleration component probability distributions conditioned on a velocity component for conditioning velocities as high as 3 times the standard deviation and find them to be highly non-Gaussian.Comment: submitted for the special issue of Physica D: "Anomalous Distributions" 11 pages, 6 figures revised version: light modifications of the figures and the tex

Reanalysis of Copernicus Measurements on Interstellar Carbon Monoxide

We used archival data acquired with the Copernicus satellite to reexamine CO column densities because self-consistent oscillator strengths are now available. Our focus is on lines of sight containing modest amounts of molecular species. Our resulting column densities are small enough that self-shielding from photodissociation is not occurring in the clouds probed by the observations. While our sample shows that the column densities of CO and H2 are related, no correspondence with the CH column density is evident. The case for the CH+ column density is less clear. Recent chemical models for these sight lines suggest that CH is mainly a by-product of CH+ synthesis in low density gas. The models are most successful in reproducing the amounts of CO in the densest sight lines. Thus, much of the CO absorption must arise from denser clumps along the line of sight to account for the trend with H2.Comment: 19 pages, 6 figures. Accepted for publication in Ap

Creative Thinking in eXtreme Programming

Agile methods such as eXtreme Programming have achieved an explosive interest in the software development community. They can be seen as a reaction to the more traditional and control-oriented methods, agile methods handle changes in design and requirements and they open up for creativity during the whole project lifecycle. The knowledge management in agile methods is also agile, it means that knowledge creation and sharing processes are simplified in comparison with other more comprehensive development methodologies. This paper is developed under the idea that agile software development can be enhanced by a better understanding of knowledge management and creativity. eXtreme Programming is analyzed from the perspective of the creativity, we believe that concepts related to creative teams (roles, structure, performance and purposes) are important insights about the use of agile methods in general and eXtreme Programming in particular.Keywords/Index Terms: Knowledge Management; Creativity; Software Engineering; Agile Methods; User-centered innovation

Survivin as a therapeutic target in Sonic hedgehog-driven medulloblastoma.

Medulloblastoma (MB) is a highly malignant brain tumor that occurs primarily in children. Although surgery, radiation and high-dose chemotherapy have led to increased survival, many MB patients still die from their disease, and patients who survive suffer severe long-term side effects as a consequence of treatment. Thus, more effective and less toxic therapies for MB are critically important. Development of such therapies depends in part on identification of genes that are necessary for growth and survival of tumor cells. Survivin is an inhibitor of apoptosis protein that regulates cell cycle progression and resistance to apoptosis, is frequently expressed in human MB and when expressed at high levels predicts poor clinical outcome. Therefore, we hypothesized that Survivin may have a critical role in growth and survival of MB cells and that targeting it may enhance MB therapy. Here we show that Survivin is overexpressed in tumors from patched (Ptch) mutant mice, a model of Sonic hedgehog (SHH)-driven MB. Genetic deletion of survivin in Ptch mutant tumor cells significantly inhibits proliferation and causes cell cycle arrest. Treatment with small-molecule antagonists of Survivin impairs proliferation and survival of both murine and human MB cells. Finally, Survivin antagonists impede growth of MB cells in vivo. These studies highlight the importance of Survivin in SHH-driven MB, and suggest that it may represent a novel therapeutic target in patients with this disease

Extremely red radio galaxies

At least half the radio galaxies at z>1 in the 7C Redshift Survey have extremely red colours (R-K>5), consistent with stellar populations which formed at high redshift (z>5). We discuss the implications of this for the evolution of massive galaxies in general and for the fraction of near-IR-selected EROs which host AGN, a result which is now being tested by deep, hard X-ray surveys. The conclusion is that many massive galaxies undergo at least two active phases: one at z~5 when the black hole and stellar bulge formed and another at z~1-2 when activity is triggered by an event such as an interaction or merger.Comment: 6 pages, 2 figures, to appear in the proceedings of the workshop on "QSO hosts and their environments", IAA, Granada, 10-12 Jan 2001, Ed. I. Marque

Like trainer, like bot? Inheritance of bias in algorithmic content moderation

The internet has become a central medium through which `networked publics' express their opinions and engage in debate. Offensive comments and personal attacks can inhibit participation in these spaces. Automated content moderation aims to overcome this problem using machine learning classifiers trained on large corpora of texts manually annotated for offence. While such systems could help encourage more civil debate, they must navigate inherently normatively contestable boundaries, and are subject to the idiosyncratic norms of the human raters who provide the training data. An important objective for platforms implementing such measures might be to ensure that they are not unduly biased towards or against particular norms of offence. This paper provides some exploratory methods by which the normative biases of algorithmic content moderation systems can be measured, by way of a case study using an existing dataset of comments labelled for offence. We train classifiers on comments labelled by different demographic subsets (men and women) to understand how differences in conceptions of offence between these groups might affect the performance of the resulting models on various test sets. We conclude by discussing some of the ethical choices facing the implementers of algorithmic moderation systems, given various desired levels of diversity of viewpoints amongst discussion participants.Comment: 12 pages, 3 figures, 9th International Conference on Social Informatics (SocInfo 2017), Oxford, UK, 13--15 September 2017 (forthcoming in Springer Lecture Notes in Computer Science

Fluid Particle Accelerations in Fully Developed Turbulence

The motion of fluid particles as they are pushed along erratic trajectories by fluctuating pressure gradients is fundamental to transport and mixing in turbulence. It is essential in cloud formation and atmospheric transport, processes in stirred chemical reactors and combustion systems, and in the industrial production of nanoparticles. The perspective of particle trajectories has been used successfully to describe mixing and transport in turbulence, but issues of fundamental importance remain unresolved. One such issue is the Heisenberg-Yaglom prediction of fluid particle accelerations, based on the 1941 scaling theory of Kolmogorov (K41). Here we report acceleration measurements using a detector adapted from high-energy physics to track particles in a laboratory water flow at Reynolds numbers up to 63,000. We find that universal K41 scaling of the acceleration variance is attained at high Reynolds numbers. Our data show strong intermittency---particles are observed with accelerations of up to 1,500 times the acceleration of gravity (40 times the root mean square value). Finally, we find that accelerations manifest the anisotropy of the large scale flow at all Reynolds numbers studied.Comment: 7 pages, 4 figure

NFC as an Alternative for Improving Videogame Development in Mobile Devices

La aparición de nuevas alternativas de interacción puede llevar a generar videojuegos cada vez más interesantes, este es el caso de la interacción con el teléfono móvil, especialmente la tecnología NFC. Sin embargo no existe un referente para conocer qué tipos de videojuegos serían los más apropiados para desarrollar con NFC. Por tanto, este artículo aporta una revisión de varias fuentes para determinar el estado actual de videojuegos con NFC para futuras referencias de generadores de contenido y emprendedores en el campo de los videojuegos; como contribuciones se tiene una revisión en varias fuentes a nivel comercial, bibliográfico y de tiendas de aplicaciones para generar el estado actual y el esquema de posibles videojuegos con los cuales NFC podría interactuar, determinando las categorías de videojuegos más apropiadas para desarrollar con dicha tecnología y proponiendo algunas características que NFC permite implementar.The emergence of new interaction alternatives can result in increasingly interesting videogames; this is the case of the interaction with the mobile phone, especially NFC technology. However, there is not a model to get to know the types of videogames that would be more appropriate to be developed with NFC. Therefore, this article provides a review of several sources to determine current state of videogames with NFC for future reference of content generators and entrepreneurs in the field of videogames; as a contribution, there is a review of several commercial, bibliographic sources and applications shops to generate current state and a scheme of potential videogames with which NFC could interact by determining categories of the most appropriate videogames to be developed with such a technology and proposing some features that can be implemented with the NFC