Pulsar Timing and its Application for Navigation and Gravitational Wave Detection

Pulsars are natural cosmic clocks. On long timescales they rival the precision of terrestrial atomic clocks. Using a technique called pulsar timing, the exact measurement of pulse arrival times allows a number of applications, ranging from testing theories of gravity to detecting gravitational waves. Also an external reference system suitable for autonomous space navigation can be defined by pulsars, using them as natural navigation beacons, not unlike the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board a spacecraft with predicted pulse arrivals at a reference location (e.g. the solar system barycenter), the spacecraft position can be determined autonomously and with high accuracy everywhere in the solar system and beyond. We describe the unique properties of pulsars that suggest that such a navigation system will certainly have its application in future astronautics. We also describe the on-going experiments to use the clock-like nature of pulsars to "construct" a galactic-sized gravitational wave detector for low-frequency (f_GW ~1E-9 - 1E-7 Hz) gravitational waves. We present the current status and provide an outlook for the future.Comment: 30 pages, 9 figures. To appear in Vol 63: High Performance Clocks, Springer Space Science Review

Red Tides In the Gulf of Mexico: Where, When, and Why?

Independent data from the Gulf of Mexico are used to develop and test the hypothesis that the same sequence of physical and ecological events each year allows the toxic dinoflagellate Karenia brevis to become dominant. A phosphorus-rich nutrient supply initiates phytoplankton succession, once deposition events of Saharan iron-rich dust allow Trichodesmium blooms to utilize ubiquitous dissolved nitrogen gas within otherwise nitrogen-poor sea water. They and the co-occurring K. brevis are positioned within the bottom Ekman layers, as a consequence of their similar diel vertical migration patterns on the middle shelf. Upon onshore upwelling of these near-bottom seed populations to CDOM-rich surface waters of coastal regions, light-inhibition of the small red tide of similar to 1 ug chl l(-1) of ichthytoxic K. brevis is alleviated. Thence, dead fish serve as a supplementary nutrient source, yielding large, self-shaded red tides of similar to 10 ug chl l(-1). The source of phosphorus is mainly of fossil origin off west Florida, where past nutrient additions from the eutrophied Lake Okeechobee had minimal impact. In contrast, the P-sources are of mainly anthropogenic origin off Texas, since both the nutrient loadings of Mississippi River and the spatial extent of the downstream red tides have increased over the last 100 years. During the past century and particularly within the last decade, previously cryptic Karenia spp. have caused toxic red tides in similar coastal habitats of other western boundary currents off Japan, China, New Zealand, Australia, and South Africa, downstream of the Gobi, Simpson, Great Western, and Kalahari Deserts, in a global response to both desertification and eutrophication

NOAA Science Advisory Board, Review of National Center for Environmental Prediction Ocean Modeling

In response to a request from the National Oceanic & Atmospheric Administration (NOAA) National Weather Service, an Ocean Model Review Panel (ORMP) was commissioned by the NOAA Science Advisory Board (SAB), to address the following two-part Charge

Towards a Regional Coastal Ocean Observing System: an Initial Design for the Southeast Coastal Ocean Observing Regional Association

A conceptual design for a southeast United States regional coastal ocean observing system (RCOOS) is built upon a partnership between institutions of the region and among elements of the academic, government and private sectors. This design envisions support of a broad range of applications (e.g., marine operations, natural hazards, and ecosystem-based management) through the routine operation of predictive models that utilize the system observations to ensure their validity. A distributed information management system enables information flow, and a centralized information hub serves to aggregate information regionally and distribute it as needed. A variety of observing assets are needed to satisfy model requirements. An initial distribution of assets is proposed that recognizes the physical structure and forcing in the southeast U.S. coastal ocean. In-situ data collection includes moorings, profilers and gliders to provide 3D, time-dependent sampling, HF radar and surface drifters for synoptic sampling of surface currents, and satellite remote sensing of surface ocean properties. Nested model systems are required to properly represent ocean conditions from the outer edge of the EEZ to the watersheds. An effective RCOOS will depend upon a vital National Backbone (federally supported) system of in situ and satellite observations, model products, and data management. This dependence highlights the needs for a clear definition of the National Backbone components and a Concept of Operations (CONOPS) that defines the roles, functions and interactions of regional and federal components of the integrated system. A preliminary CONOPS is offered for the Southeast (SE) RCOOS. Thorough system testing is advocated using a combination of application-specific and process-oriented experiments. Estimates of costs and personnel required as initial components of the SE RCOOS are included. Initial thoughts on the Research and Development program required to support the RCOOS are also outlined

Saharan dust and phosphatic fidelity: A three-dimensional biogeochemical model of Trichodesmium as a nutrient source for red tides on the West Florida Shelf

The availability of iron within the surface waters of the broad, oligotrophic West Florida Shelf (WFS) controls periodic blooms of the pelagic marine cyanobacterium Trichodesmium. Summer delivery of Saharan dust provided adequate iron (Fe) to shift limitation of growth to the availability of phosphorus (P). Florida's rivers drain Miocene phosphorus deposits to provide the WFS with freshwater nutrient supplies at molar dissolved inorganic nitrogen/phosphate (DIN/PO 4) ratios of <6. These diazotrophs draw upon ubiquitous stocks of dissolved nitrogen gas, once stimulated by Fe-deposition within P-replete waters of the WFS. An extensive in situ data set collected between 1998 and 2001 (NEGOM/ECOHAB) provided plankton taxonomy, hydrographic, nutrient, dissolved organic matter (DOM), pigment, and optical properties on the shelf. We constructed a three-dimensional numerical model to analyze the impact of iron fertilization of the diazotroph Trichodesmium and the resultant effect upon the elemental cycles of N, P, and Fe. The coupled physical and ecological models show that the wet deposition of Fe-rich Saharan dust was necessary to stimulate enough nitrogen fixation to initialize the toxic red tide ( Karenia brevis) of ∼20 μg chl a l −1 that occurred in October 1999. The simulation suggests that the magnitude and longevity of the Trichodesmium population, and therefore this source of ‘new’ nitrogen, was controlled by both phosphorus and iron availability

Kamen'. Rivista di poesia e filosofia. S.Sini Membro del Comitato scientifico e redazionale Codice rivista: E194795 Issn: 2532-6546

\uabKamen\u2019\ubb nasce nel 1991. Il nome della rivista, dal russo \u41a\u430\u43c\u435\u43d\u44c: \u201cpietra\u201d, omaggio alla raccolta di versi di Osip Mandel'\u161tam, indica programmaticamente come fondamentale la scelta di rivolgersi alle tradizioni della poesia di pensiero a forte radicamento etico. Con scadenza semestrale e formula monografica \uabKamen\u2019\ubb costituisce un progetto internazionale plurimo e un\u2019ampia comunit\ue0 di ricerca sulle tradizioni europee ed extraeuropee. Si sono tradotti poeti di varie geografie, inediti o poco conosciuti in Italia; alcuni sono poi entrati nella redazione. Fra loro Karin Boye, Birgitta Trotzig, Christine Koschel, Maria Lain\ue0, Inger Christensen, Urszula Koziol, Lidija Vuk\u10devic, Innokentij Annenskij, Jurgis Baltru\u161aitis, Francisco Brines, Carlos Contramaestre, Herberto Helder, Paruir Sevak, Armenio Vi\ue9ira, Anastasio Lovo, Ant\uf3nio Ramos Rosa, Magnus William-Olsson. Per la poesia italiana sono stati pubblicati testi di Carlo Michelstaedter, Giacomo Noventa, Rodolfo Quadrelli, Alfonso Gatto, Giuseppe Pontiggia, Giancarlo Buzzi, Giampiero Neri, Guido Oldani, Pier Luigi Bacchini, Remo Pagnanelli, Anna Cascella, Nanni Cagnone, Cristina Annino, Elio Pecora, Roberto Piumini, Sandro Boccardi, Lino Angiuli, Assunta Finiguerra e altri. Nelle diverse sezioni della rivista \u201cPoesia\u201d, \u201cFilosofia\u201d, \u201cCritica\u201d, \u201cPoetiche\u201d, \u201cMateriali\u201d si sono ospitati testi e ricerche di/su Michelstaedter, Rebora, Dino Formaggio, Carlo Dionisotti. Vincenzo Gioberti, Adelchi Baratono, Edgardo Abbozzo, Dante Filippucci, Staffan Nihl\ue9n, David Fiesoli, Sergio Serapioni, Michail Bachtin, Grigorij Skovoroda, Gustav \u160pet, Grigorij Vinokur, Richard Weisberg, N. Scott Momaday, Viktor \u17dirmunskij, Darko Suvin e altri. Ricordiamo inoltre le nove selezioni di \u201cScritti sull\u2019umorismo dal 1860 al 1930\u201d pubblicate dal 2009 al 2013