2,354 research outputs found
KOI-3158: The oldest known system of terrestrial-size planets
The first discoveries of exoplanets around Sun-like stars have fueled efforts to find ever smaller worlds evocative of Earth and other terrestrial planets in the Solar System. While gas-giant planets appear to form preferentially around metal-rich stars, small planets (with radii less than four Earth radii) can form under a wide range of metallicities. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the Universeâs history when metals were far less abundant. We report Kepler spacecraft observations of KOI-3158, a metal-poor Sun-like star from the old population of the Galactic thick disk, which hosts five planets with sizes between Mercury and Venus. We used asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that KOI-3158 formed when the Universe was less than 20 % of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the Universeâs 13.8-billion-year history, providing scope for the existence of ancient life in the Galaxy
An Ancient Extrasolar System with Five Sub-Earth-size Planets
The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the transit photometry. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that Kepler-444 formed when the universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the universe's 13.8 billion year history, leaving open the possibility for the existence of ancient life in the Galaxy. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation
Tropospheric gravity waves observed by three closely spaced ST radars
Clear-air radar experiments were carried out on the southern coast of France during the (ALPEX) Alpine experiment program vertically directed stratosphere-troposphere-radars were set up with spacings of about 5 to 6 km. The temporal and spectral characteristics of the vertical velocity fluctuations were examined. The horizontal and vertical properties of gravity waves in the lower atmosphere were analyzed. The techniques used and the first results from this wave study are described
Use of a Granulocyte Immunofluorescence Assay Designed for Humans for Detection of Antineutrophil Cytoplasmic Antibodies in Dogs with Chronic Enteropathies
Perinuclear antineutrophil cytoplasmic antibodies (pANCA) previously have been shown to be serum markers in dogs with chronic enteropathies, with dogs that have foodâresponsive disease (FRD) having higher frequencies of seropositivity than dogs with steroidâresponsive disease (SRD). The indirect immunofluorescence (IIF) assay used in previous publications is timeâconsuming to perform, with low interobserver agreement. Fortyâfour dogs with FRD, 20 dogs with SRD, 20 control dogs, and 38 softâcoated wheaten terrier (SCWT) or SCWTâcross dogs
Hyperinnervation Produces Inhibitory Interactions between Two Taste Nerves a
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74872/1/j.1749-6632.1987.tb43629.x.pd
Organic Food and Agriculture - Ethics
Organic food is produced without the use of synthetic fertilizers and pesticides. Four further exclusions in organic production are: genetically modified organisms (GMOs), irradiation, prophylactic antibiotics, and engineered nanoparticles. These six exclusions differentiate organic agriculture from chemical agriculture. Agriculture and food harvesting and production date back millennia, and until about a century ago that history is de facto organic. The Industrial Revolution ushered in an era of novel production strategies. Agriculture was not immune to new views of industrialization and reductionism. Advances in chemistry enabled some implementation of such views. Early in the diffusion of chemical farming practices, the Austrian mystic Rudolf Steiner (1865â1924) called for a differentiated agriculture free of these new synthetic chemical inputs. The terminology, theory, and practices of biodynamic agriculture evolved (in the 1920s and 1930s) from Steinerâs Agriculture Course of 1924. It was a guided evolution, coordinated by Ehrenfried Pfeiffer (1899â1961) in Switzerland. The UK agriculturist, Lord Northbourne (1896â1982), invited Pfeiffer to lead a conference on biodynamics at his farm in Kent (in 1939). The following year Northbourne published his manifesto of organic farming, âLook to the Land.â In that book, he coined the term âorganic farmingâ and wrote of a contest of âorganic versus chemical farmingâ.The ideas and ideals of organic farming quickly proliferated internationally off the back of Northbourneâs 1940 book. Organic farming is now practiced in at least 179 countries, accounts for 50.9 million agricultural hectares, and a market value of US$ 81.6 billion (âŹ75 billion)
Growth and Water Use of Perennial Ryegrass and Tall Fescue under Different Irrigation Treatments
Voyager spacecraft radio observations of Jupiter: Initial cruise results
Jupiter's low-frequency radio emission were detected by the planetary radio astronomy instruments onboard the two Voyager spacecraft. The emission is surprisingly similar in morphology but opposite in polarization to the high-frequency Jovian radio noise that were observed with ground-based telescopes for more than two decades. Several possible explanations for the behavior of the low-frequency emission are examined, but none of them is completely satisfactory
Non Melanoma Skin Cancer and Subsequent Cancer Risk
Introduction:
Several studies have shown an increased risk of cancer after non melanoma skin cancers (NMSC) but the individual risk factors underlying this risk have not been elucidated, especially in relation to sun exposure and skin sensitivity to sunlight. Purpose: The aim of this study was to examine the individual risk factors associated with the development of subsequent cancers after non melanoma skin cancer. Methods: Participants in the population-based New Hampshire Skin Cancer Study provided detailed risk factor data, and subsequent cancers were identified via linkage with the state cancer registry. Deaths were identified via state and national death records. A Cox proportional hazard model was used to estimate risk of subsequent malignancies in NMSC patients versus controls and to assess the potential confounding effects of multiple risk factors on this risk. Results: Among 3584 participants, risk of a subsequent cancer (other than NMSC) was higher after basal cell carcinoma (BCC) (adjusted HR 1.40 [95% CI 1.15, 1.71]) than squamous cell carcinoma (SCC) (adjusted HR 1.18 [95% CI 0.95, 1.46]) compared to controls (adjusted for age, sex and current cigarette smoking). After SCC, risk was higher among those diagnosed before age 60 (HR 1.96 [95% CI 1.24, 3.12]). An over 3-fold risk of melanoma after SCC (HR 3.62; 95% CI 1.85, 7.11) and BCC (HR 3.28; 95% CI 1.66, 6.51) was observed, even after further adjustment for sun exposure-related factors and family history of skin cancer. In men, prostate cancer incidence was higher after BCC compared to controls (HR 1.64; 95% CI 1.10, 2.46). Conclusions: Our population-based study indicates an increased cancer risk after NMSC that cannot be fully explained by known cancer risk factors
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