Method for detecting hydrogen gas

Method and transducer device for detecting presence of hydrogen ga

Pumping lemmas for classes of languages generated by folding systems

Geometric folding processes are ubiquitous in natural systems ranging from protein biochemistry to patterns of insect wings and leaves. In a previous study, a folding operation between strings of formal languages was introduced as a model of such processes. The operation was then used to define a folding system (F-system) as a construct consisting of a core language, containing the strings to be folded, and a folding procedure language, which defines how the folding is done. This paper reviews main definitions associated with F-systems and next it determines necessary conditions for a language to belong to classes generated by such systems. The conditions are stated in the form of pumping lemmas and four classes are considered, in which the core and folding procedure languages are both regular, one of them is regular and the other context-free, or both are context-free. Full demonstrations of the lemmas are provided, and the analysis is illustrated with examples.Comment: 12 pages, 6 figures. This is a preprint (pre-refereeing) version of a manuscript accepted for publication in Natural Computin

A note on the class of languages generated by F-systems over regular languages

An F-system is a computational model that performs a folding operation on strings of a given language, following directions coded on strings of another given language. This note considers the case in which both given languages are regular, and it shows that such F-system generates linear context-free languages. The demonstration is based on constructing a one-turn pushdown automaton for the generated language.Comment: Five pages, one figure. This article is a follow-up of arXiv:1910.08518[cs.FL

Position-Velocity Diagrams for the Maser Emission coming from a Keplerian Ring

We have studied the maser emission from a thin, planar, gaseous ring in Keplerian rotation around a central mass observed edge-on. The absorption coefficient within the ring is assumed to follow a power law dependence with the distance from the central mass as, k=k0r^{-q}. We have calculated position-velocity diagrams for the most intense maser features, for different values of the exponent q. We have found that, depending on the value of q, these diagrams can be qualitatively different. The most intense maser emission at a given velocity can either come mainly from regions close to the inner or outer edges of the amplifying ring or from the line perpendicular to the line of sight and passing through the central mass (as is commonly assumed). Particularly, when q>1 the position-velocity diagram is qualitatively similar to the one observed for the water maser emission in the nucleus of the galaxy NGC 4258. In the context of this simple model, we conclude that in this object the absorption coefficient depends on the radius of the amplifying ring as a decreasing function, in order to have significant emission coming from the inner edge of the ring.Comment: 13 pages, 7 figures, to appear in the 2007 July 20 issue of The Astrophysical Journa

HI observations of the nearest starburst galaxy NGC 253 with the SKA precursor KAT-7

We present HI observations of the Sculptor Group starburst spiral galaxy NGC 253, obtained with the Karoo Array Telescope (KAT-7). KAT-7 is a pathfinder for the SKA precursor MeerKAT, under construction. The short baselines and low system temperature of the telescope make it very sensitive to large scale, low surface brightness emission. The KAT-7 observations detected 33% more flux than previous VLA observations, mainly in the outer parts and in the halo for a total HI mass of $2.1 \pm 0.1$ $\times 10^{9}$ M$_{\odot}$. HI can be found at large distances perpendicular to the plane out to projected distances of ~9-10 kpc away from the nucleus and ~13-14 kpc at the edge of the disk. A novel technique, based on interactive profile fitting, was used to separate the main disk gas from the anomalous (halo) gas. The rotation curve (RC) derived for the HI disk confirms that it is declining in the outer parts, as seen in previous optical Fabry-Perot measurements. As for the anomalous component, its RC has a very shallow gradient in the inner parts and turns over at the same radius as the disk, kinematically lagging by ~100 km/sec. The kinematics of the observed extra planar gas is compatible with an outflow due to the central starburst and galactic fountains in the outer parts. However, the gas kinematics shows no evidence for inflow. Analysis of the near-IR WISE data, shows clearly that the star formation rate (SFR) is compatible with the starburst nature of NGC 253.Comment: 18 pages, 20 figures, 8 Tables. Accepted for publication to MNRA

Dugong stranding and suggestions for conservation: a tool to support endangered marine resource conservation

February 23-25, 2010, Phuket, ThailandThe study aimed to (a) provide record of dugong stranding and mortality, (b) conduct necropsy of dugong, (c) characterize the circumstantial causes of mortality and stranding and (d) determine the threats that impede dugong conservation.Secondary data available on strandings and mortality of dugong were utilized to confirm validity of data obtained from interview of fishfarmers. Record of logged and reported incidents of dugong strandings and mortality were also retrieved. Necropsy was done every time dugong mortality occurred. Information and data were kept in dugong data sheets. Preliminary results showed that from 2001 – 2008, six strandings of dugongs have been documented in Malita, Davao del Sur. All the six strandings occurred within an approximate 10 km stretch of coastline (from Brgy. Lacaron to Brgy. Tingolo) of Malita, Davao del Sur. One out of the six strandings was a female baby dugong. The other four were male adult dugong with a length of not less than 2m. The probable causes of death were mostly anthropogenic: victim of spear fishing, blasting, entangled in net and intentionally caught for food. Parasitism was also observed in one of the dugongs that was examined where the gut, stomach, intestine were heavily infested with round worms