Invisible pushdown languages

Context free languages allow one to express data with hierarchical structure, at the cost of losing some of the useful properties of languages recognized by finite automata on words. However, it is possible to restore some of these properties by making the structure of the tree visible, such as is done by visibly pushdown languages, or finite automata on trees. In this paper, we show that the structure given by such approaches remains invisible when it is read by a finite automaton (on word). In particular, we show that separability with a regular language is undecidable for visibly pushdown languages, just as it is undecidable for general context free languages

Investigation Of Posttranscriptional Regulation After Global Brain Ischemia And Reperfusion Injury

The final cause of death in most patients revived after cardiac arrest is ischemia and reperfusion (I/R) injury in the brain. Survival after brain I/R injury depends on the expression of new stress response proteins such as heat shock protein 70 (HSP70). Little is known about why recovering neurons are able to express new stress response proteins while neurons that will die can transcribe RNA but do not translated protein in early reperfusion. Previous studies suggested that the mRNA-binding protein HuR may regulate hsp70 mRNA in reperfused neurons through a novel cytoplasmic structure, the mRNA granule. To determine the roles of HuR and the mRNA granule in reperfused neurons and to characterize global translation regulation, we 1) prevented mRNA granule formation in reperfused neurons or induced mRNA granules in uninjured neurons by pharmacological manipulation polysomes, 2. studied potential HuR posttranscriptional regulation mechanisms of facilitated nuclear export and polysome association, and 3. performed translation state analysis of reperfused neurons from hippocampal subregions CA1 and CA3. We found that mRNA granules can be prevented in reperfused neurons by locking mRNA onto polysomes with cycloheximide. In uninjured neurons, mRNA granules can be induced with puromycin, which promotes early translation termination and dissociation of ribosomes from mRNA. In hippocampal neurons after 10 minutes global brain ischemia and 8 hours reperfusion, HuR remained constant in nuclear and cytoplasmic fractions and unfractionated homogenate. Nucleocytoplasmic distribution of hsp70 mRNA was identical between ischemia-resistant CA3 and ischemia-vulnerable CA1 neurons at 8 hours reperfusion. HuR\u27s distribution on polysome profiles was unchanged after 8 hours reperfusion, and HuR did not localize to polysomes in response to I/R injury. Translation state analysis of CA1 and CA3 neurons showed that the two regions have largely different mRNA populations on their polysomes at 8 hours reperfusion, and polysome-bound mRNA from both regions was enriched in the adenine and uridine rich element (ARE), a 3\u27 untranslated region regulatory site. In conclusion, polysome-associated mRNA is necessary for mRNA granule formation. HuR may regulate expression of stress response proteins, but does not do so by any known mechanism. Ischemia-vulnerable CA1 and ischemia-resistant CA3 neurons have different mRNA populations associated with polysomes at 8 hours reperfusion after global ischemia, but both are enriched in AREs

Towards a Philosophy of Woodworking: Re-embracing Community and Quality Craftsmanship in Contemporary America

Since the Scientific Revolution of the seventeenth-century, humanity has appropriated the natural world for its uses, and only recently have we begun to understand the consequences of our actions. This misuse of the natural world has manifested itself thoroughly in all industries, including the woodworking field. To counteract this problem, I investigate its Cartesian philosophical underpinnings and propose a solution based upon the interconnected philosophy of the German Existentialist Martin Heidegger. Equipped with both the philosophy of Heidegger and concepts from the Deep Ecology movement (which insists upon the intrinsic value of all life on earth), I work to reformulate how woodworkers and tradesmen approach their craft. Before attempting this, however, I delve into a parallel field – that of organic agriculture – to investigate similarities in practical development. After a review of past woodworking philosophies, I develop six key concepts as well as a practical way forward for the woodworking community (based upon successes already witnessed in the organic movement). To conclude, I provide examples of how some aspects of this philosophy are already taking hold: most notably in vocational programs and small woodworking communities throughout our nation and the world

Teaching multidisciplinary engineering using concepts and technology of WSN

This paper discusses teaching and learning strategies of Wireless Sensor Networks technology in a new postgraduate subject run at the Faculty of Engineering and IT, University of Technology, Sydney. The aim is to present the role of using practice based and multidisciplinary methodologies in the context of new ICT technologies. This includes shared experiences, observations and common problems experienced in teaching new concepts and paradigms, standards, protocols and algorithms, embedded systems and sensor technologies. The theory of WSN is applied as a driver of system development for the group projects that students undertake in the subject. © 2012 IEEE

Large 2D Coulomb crystals in a radio frequency surface ion trap

We designed and operated a surface ion trap, with an ion-substrate distance of 500\mum, realized with standard printed-circuit-board techniques. The trap has been loaded with up to a few thousand Sr+ ions in the Coulomb-crystal regime. An analytical model of the pseudo-potential allowed us to determine the parameters that drive the trap into anisotropic regimes in which we obtain large (N>150) purely 2D ion Coulomb crystals. These crystals may open a simple and reliable way to experiments on quantum simulations of large 2D systems.Comment: 4 pages, 4 figure

The Optical Gravitational Lensing Experiment. Variable Stars in Globular Clusters - IV. Fields 104A-E in 47 Tuc

Five fields located close to the center of the globular cluster NGC 104=47 Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars -- 12 of them belong to the Small Magellanic Cloud (SMC) and 1 is a background object from the galactic halo. Twelve eclipsing binaries were identified -- 9 contact systems and 3 detached/semi-detached systems. Seven eclipsing binaries are located in the blue straggler region on the cluster color-magnitude diagram (CMD) and four binaries can be considered main-sequence systems. One binary is probably a member of the SMC. Eight contact binaries are likely members of the cluster and one is most probably a foreground star. We show that for the surveyed region of 47 Tuc, the relative frequency of contact binaries is very low as compared with other recently surveyed globular clusters. The sample of identified variables also includes 15 red variables with periods ranging from about 2 days to several weeks. A large fraction of these 15 variables probably belong to the SMC but a few stars are likely to be red giants in 47 Tuc. VI photometry for about 50 000 stars from the cluster fields was obtained as a by product of our survey.Comment: Latex file, l-aa style, 10 pages, 7 ps figures included. Submitted to A&A. Figure 8 available from ftp://sirius.astrouw.edu.pl/pub/jka/47Tuc/fig8.ps.