Using discrete Darboux polynomials to detect and determine preserved measures and integrals of rational maps

In this Letter we propose a systematic approach for detecting and calculating preserved measures and integrals of a rational map. The approach is based on the use of cofactors and Discrete Darboux Polynomials and relies on the use of symbolic algebra tools. Given sufficient computing power, all rational preserved integrals can be found. We show, in two examples, how to use this method to detect and determine preserved measures and integrals of the considered rational maps.Comment: 8 pages, 1 Figur

Altimetric system: Earth observing system. Volume 2h: Panel report

A rationale and recommendations for planning, implementing, and operating an altimetric system aboard the Earth observing system (Eos) spacecraft is provided. In keeping with the recommendations of the Eos Science and Mission Requirements Working Group, a complete altimetric system is defined that is capable of perpetuating the data set to be derived from TOPEX/Poseidon, enabling key scientific questions to be addressed. Since the scientific utility and technical maturity of spaceborne radar altimeters is well documented, the discussion is limited to highlighting those Eos-specific considerations that materially impact upon radar altimetric measurements

Distribution and habitat associations of the Critically Endangered frog Walkerana phrynoderma (Anura: Ranixalidae), with an assessment of potential threats, abundance, and morphology

Distribuição e associações de habitat do anuro Criticamente Ameaçado Walkerana phrynoderma (Anura: Ranixalidae), com uma avaliação das ameaças potenciais, abundância e morfologia. Pouco se sabe sobre Walkerana phrynoderma, um anuro endêmico dos Montes Anamalai dos Ghats Ocidentais da Índia. Com o objetivo de aumentar nosso conhecimento do status da espécie na natureza, fornecemos informações básicas (i.e., distribuição, ameaças, características do habitat, padrões de atividade e abundância relativa). Foram feitas investigações por encontro visual, transectos e orçamento temporal no interior e entorno dos Montes Anamalai dos Ghats Ocidentais. A secreção da pele dos animais foi amostrada para determinar a presença/ausência de Batrachochytrium dendrobatidis, e foram registradas as características do habitat e do ambiente nos locais onde W. phrynoderma foi encontrada. Esses dados foram comparados com os dos locais em que a espécie estava aparentemente ausente. Walkerana phrynoderma está restrita às forestas perenifolias situadas entre 1300 e 1700 m a.s.l. na Reserva Anamalai Tiger e em Munnar; dessa forma, sua distribuição foi extendida do estado de Tamil Nadu para o estado vizinho de Kerala. As ameaças mais severas a essa espécia são o uso de pesticidas e perturbações antrópicas; B. dendrobatidis não foi detectado. Esse anuro norturno prefere bordas forestais e está associado com chãos de forestas bem sombreadas em áreas frescas próximo a riachos. Walkerana phrynoderma é raramente encontrada, enquanto sua congênere, W. leptodactyla, é mais comum. O impacto de perturbações antropogênicas, especialmente deposição de lixo e desenvolvimento de infraestrutura turística, deveria ser avaliado. A área de propriedade do Departamento de Florestas na periferia das áreas protegidas poderia ser designada como locais ecossensíveis para prevenir mudanças no uso da terra que pudessem ter um efeito adverso sobre W. phrynoderma.Distribution and habitat associations of the Critically Endangered frog Walkerana phrynoderma (Anura: Ranixalidae), with an assessment of potential threats, abundance, and morphology. Little is known about Walkerana phrynoderma, a frog endemic to the Anamalai Hills of the Western Ghats of India. Baseline information (i.e., distribution, threats, habitat characteristics, activity patterns, and relative abundance) is provided for this species, with the aim of improving our understanding of the status of the species in the wild. Visual-encounter, transect, and time-activity budget surveys were conducted in and around the Anamalai Hills of the Western Ghats. The frog skin was swabbed to determine the presence/absence of Batrachochytrium dendrobatidis, and habitat and environmental characteristics were recorded at sites where W. phrynoderma was found. These data were compared with those of sites apparently lacking this species that had suitable habitat. Walkerana phrynoderma is restricted to evergreen forests between 1300 and 1700 m a.s.l. in the Anamalai Tiger Reserve and at Munnar; thus, its range was extended from the state of Tamil Nadu to the adjoining state of Kerala. Pesticide runoff and human disturbance are the most severe threats to the species; B. dendrobatidis was not detected. This nocturnal anuran prefers forest edges and is associated with well-shaded forest foors in cool areas near freshwater streams. Walkerana phrynoderma is rarely encountered whereas its congener, W. leptodactyla, is more common. The impact of anthropogenic disturbances, especially waste disposal and development of tourism infrastructure, should be evaluated. The land that is owned by the Forest Department peripheral to the protected areas could be designated as eco-sensitive sites to prevent changes in land use that could have an adverse effect on W. phrynoderma

1862-08-04 Gideon Tucker and Rufus P. Tapley recommend George A. Deering for a position

https://digitalmaine.com/cw_me_16th_regiment_corr/1071/thumbnail.jp

Observation of charged nanograins at comet 67P/Churyumov‐Gerasimenko

Soon after the Rosetta Orbiter rendezvoused with comet 67P/Churyumov‐Gerasimenko at a solar distance of ~3.5 AU and began to fly in triangular‐shaped trajectories around it, the Ion and Electron Sensor detected negative particles at energies from about 100 eV/q to over 18 keV/q. The lower energy particles came from roughly the direction of the comet; the higher‐energy particles came from approximately the solar direction. These particles are interpreted as clusters of molecules, most likely water, which we refer to as nanograins because their inferred diameters are less than 100 nm. Acceleration of the grains away from the comet is through gas drag by the expanding cometary atmosphere, while acceleration back to the vicinity of the comet is caused partly by solar radiation pressure but mainly by the solar wind electric field. These observations represent the first measurements of energetic charged submicron‐sized dust or ice grains (nanograins) in a cometary environment.Key PointsFirst observation of charged nanograins from a cometNanograins are reflected by solar radiation pressure and accelerated by solar wind electric fieldsNanograins return to the vicinity of the comet after significant energizationPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113696/1/grl53313_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/113696/2/grl53313.pd

On the Lense-Thirring test with the Mars Global Surveyor in the gravitational field of Mars

I discuss some aspects of the recent test of frame-dragging performed by me by exploiting the Root-Mean-Square (RMS) orbit overlap differences of the out-of-plane component N of the orbit of the Mars Global Surveyor (MGS) spacecraft in the gravitational field of Mars. A linear fit of the full time series of the entire MGS data (4 February 1999-14 January 2005) yields a normalized slope 1.03 +/- 0.41 (with 95% confidence bounds). Other linear fits to different data sets confirm the agreement with general relativity. The huge systematic effects induced by the mismodeling in the martian gravitational field claimed by some authors are absent in the MGS out-of-plane record. The non-gravitational forces affect at the same level of the gravitomagnetic one the in-plane orbital components of MGS, not the out-of-plane one. Moreover, they experience high-frequency variations which does not matter in the present case in which secular effects are relevant.Comment: LaTex2e, 8 pages, no figures, no tables, 17 references. It refers to K. Krogh, Class. Quantum Grav., 24, 5709-5715, 2007 based on astro-ph/0701653. Final version to appear in CEJP (Central European Journal of Physics

Orbital Tests of Relativistic Gravity using Artificial Satellites

We reexamine non-Einsteinian effects observable in the orbital motion of low-orbit artificial Earth satellites. The motivations for doing so are twofold: (i) recent theoretical studies suggest that the correct theory of gravity might contain a scalar contribution which has been reduced to a small value by the effect of the cosmological expansion; (ii) presently developed space technologies should soon give access to a new generation of satellites endowed with drag-free systems and tracked in three dimensions at the centimeter level. Our analysis suggests that such data could measure two independent combinations of the Eddington parameters (beta - 1) and (gamma - 1) at the 10^-4 level and probe the time variability of Newton's "constant" at the d(ln G)/dt ~ 10^-13 yr^-1 level. These tests would provide well-needed complements to the results of the Lunar Laser Ranging experiment, and of the presently planned experiments aiming at measuring (gamma -1). In view of the strong demands they make on the level of non- gravitational perturbations, these tests might require a dedicated mission consisting of an optimized passive drag-free satellite.Comment: 17 pages, IHES/P/94/22 and CPT-94/P.E.302

On the possibility of measuring relativistic gravitational effects with a LAGEOS-LAGEOS II-OPTIS-mission

In this paper we wish to preliminary investigate if it would be possible to use the orbital data from the proposed OPTIS mission together with those from the existing geodetic passive SLR LAGEOS and LAGEOS II satellites in order to perform precise measurements of some general relativistic gravitoelectromagnetic effects, with particular emphasis on the Lense-Thirring effect.Comment: Abridged version. 16 pages, no figures, 1 table. First results from the GGM01C Earth gravity model. GRACE data include

Will the recently approved LARES mission be able to measure the Lense-Thirring effect at 1%?

After the approval by the Italian Space Agency of the LARES satellite, which should be launched at the end of 2009 with a VEGA rocket and whose claimed goal is a about 1% measurement of the general relativistic gravitomagnetic Lense-Thirring effect in the gravitational field of the spinning Earth, it is of the utmost importance to reliably assess the total realistic accuracy that can be reached by such a mission. The observable is a linear combination of the nodes of the existing LAGEOS and LAGEOS II satellites and of LARES able to cancel out the impact of the first two even zonal harmonic coefficients of the multipolar expansion of the classical part of the terrestrial gravitational potential representing a major source of systematic error. While LAGEOS and LAGEOS II fly at altitudes of about 6000 km, LARES will be placed at an altitude of 1450 km. Thus, it will be sensitive to much more even zonals than LAGEOS and LAGEOS II. Their corrupting impact \delta\mu has been evaluated by using the standard Kaula's approach up to degree L=70 along with the sigmas of the covariance matrices of eight different global gravity solutions (EIGEN-GRACE02S, EIGEN-CG03C, GGM02S, GGM03S, JEM01-RL03B, ITG-Grace02s, ITG-Grace03, EGM2008) obtained by five institutions (GFZ, CSR, JPL, IGG, NGA) with different techniques from long data sets of the dedicated GRACE mission. It turns out \delta\mu about 100-1000% of the Lense-Thirring effect. An improvement of 2-3 orders of magnitude in the determination of the high degree even zonals would be required to constrain the bias to about 1-10%.Comment: Latex, 15 pages, 1 table, no figures. Final version matching the published one in General Relativity and Gravitation (GRG

The disparity between species description and conservation assessment: A case study in taxa with high rates of species discovery

The IUCN Red List of Threatened Species (Red List) details the extinction risk of the world's species and presents an important biodiversity indicator for conservation policy. Its continued utility relies on it containing up-to-date information on the extinction risk of species. This requires both regular reassessments and the timely assessment of newly described species. We provide an overview of the status of amphibian Red List assessments to highlight the difficulties of keeping assessments updated for species groups with high rates of species description. Since the publication of the IUCN's Global Amphibian Assessment in 2004, description rates of new species and assessment rates were initially similar; yet while the former has remained consistent, the latter has recently sharply declined. Currently 61.3% of amphibian species are either Not Evaluated or have out-of-date assessments. The situation is particularly problematic in countries with the richest amphibian diversity, which typically have the highest rates of amphibian species discovery and face the greatest threats. Efforts to keep the Red List up-to-date are primarily limited by funding, we estimate that an annual investment of US $170,478–$319,290 is needed to have an up-to-date Red List for amphibians. We propose suggestions to increase assessment rates by improving the availability of data relevant to the process: authors of species descriptions or taxonomic revisions should publish information relevant to Red List assessments. Taxonomic journals should suggest inclusion of such information in their author guidelines. We suggest that contributors with significant input into assessments should be rewarded with co-authorship of published assessments