Properties and occurrence rates of KeplerKepler exoplanet candidates as a function of host star metallicity from the DR25 catalog

Correlations between the occurrence rate of exoplanets and their host star properties provide important clues about the planet formation processes. We studied the dependence of the observed properties of exoplanets (radius, mass, and orbital period) as a function of their host star metallicity. We analyzed the planetary radii and orbital periods of over 2800 $Kepler$ candidates from the latest $Kepler$ data release DR25 (Q1-Q17) with revised planetary radii based on $Gaia$~DR2 as a function of host star metallicity (from the Q1-Q17 (DR25) stellar and planet catalog). With a much larger sample and improved radius measurements, we are able to reconfirm previous results in the literature. We show that the average metallicity of the host star increases as the radius of the planet increases. We demonstrate this by first calculating the average host star metallicity for different radius bins and then supplementing these results by calculating the occurrence rate as a function of planetary radius and host star metallicity. We find a similar trend between host star metallicity and planet mass: the average host star metallicity increases with increasing planet mass. This trend, however, reverses for masses $> 4.0\, M_\mathrm{J}$: host star metallicity drops with increasing planetary mass. We further examined the correlation between the host star metallicity and the orbital period of the planet. We find that for planets with orbital periods less than 10 days, the average metallicity of the host star is higher than that for planets with periods greater than 10 days.Comment: 14 pages, 13 Figures, Accepted for publication in The Astronomical Journa

A new mechanism for negative refraction and focusing using selective diffraction from surface corrugation

Refraction at a smooth interface is accompanied by momentum transfer normal to the interface. We show that corrugating an initially smooth, totally reflecting, non-metallic interface provides a momentum kick parallel to the surface, which can be used to refract light negatively or positively. This new mechanism of negative refraction is demonstrated by visible light and microwave experiments on grisms (grating-prisms). Single-beam all-angle-negative-refraction is achieved by incorporating a surface grating on a flat multilayered material. This negative refraction mechanism is used to create a new optical device, a grating lens. A plano-concave grating lens is demonstrated to focus plane microwaves to a point image. These results show that customized surface engineering can be used to achieve negative refraction even though the bulk material has positive refractive index. The surface periodicity provides a tunable parameter to control beam propagation leading to novel optical and microwave devices.Comment: 6 pages, 7 figures in RevTex forma

Nanoengineering of a Negative-Index Binary-Staircase Lens for the Optics Regime

We show that a binary-staircase optical element can be engineered to exhibit an effective negative index of refraction, thereby expanding the range of optical properties theoretically available for future optoelectronic devices. The mechanism for achieving a negative-index lens is based on exploiting the periodicity of the surface corrugation. By designing and nanofabricating a plano-concave binary-staircase lens in the InP/InGaAsP platform, we have experimentally demonstrated at 1.55 microns that such negative-index concave lenses can focus plane waves. The beam propagation in the lens was studied experimentally and was in excellent agreement with the three-dimensional finite-difference time-domain numerical simulations.Comment: 4 pages, 4 figure

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AvailableSaline soils constitute 15% of global landmass and have direct influence on the production functions of the existing land uses. In India, 6.75 Mha area is salt-affected, out of which 2.92 Mha are saline soils. The menace, increasing with each passing year to the irrigated areas, has become a major concern. Agroforestry plays a pivotal role in biological amelioration and check in further expansion of such landmasses. It is always useful to have agroforestry models/systems for saline landmasses by involving multipurpose nitrogen-fixing tree species, fruit trees, halophytes, and arable crops of economic importance. The potential flora suitable to saline soils has been identified based on tolerance level and climatic adaptability. The successful planting methods, viz., ridge-trench, furrow, and subsurface planting with furrow irrigation, have also been assessed and recommended for saline soils. Plant adaptations to saline conditions involve complex physiological traits, metabolic pathways, and molecular gene networks. These adaptive mechanisms to such ecologies are basically governed by one of the three processes like exclusion, excretion, and accumulation among trees and/or crops. In true sense, reclamation processes also help to keep the salt away and/or within tolerable limits for growing flora in the rhizosphere. Productive service functions of plants can be obtained from saline soils by combining reclamation and management options in pragmatic way. Sequential, agrisilviculture, agrihorticulture, silvopastoral, multipurpose wood lots, saline aquaforestry, homestead gardens, and energy plantations are the biological and economical viable recommended farm agroforestry practices in saline soils. Prosopis cineraria (Khejri) for hot dryland, Eucalyptus tereticornis (Safeda), Melia composita (Dek), Aegle marmelos (Bael), Emblica officinalis (Aonla), and Carissa carandas (Karonda) for saline-irrigated area and Casuarina equisetifolia (Casuarina), Eucalyptus camaldulensis (Safeda), and Acacia nilotica (Babul) for coastal regions as agroforestry trees in system mode are successful in reclaiming the saline soils with economic gains for sustenance. The benefits of agroforestry can be grouped into biomass, soil/environment, and socioeconomic outputs. This chapter highlights the issues in the quantification of the systems’ output in terms of existing procedural protocols. The agroforestry has passed and transcends into variable phases with the advancement as subject. Therefore, plausible future of the agroforestry is presented by taking the cognizance of present needs and future challenges in general and particular about saline soils. The holistic approaches of agroforestry undoubtedly rehabilitate saline soils and certainly will give income in perpetuity, employment generation, food and nutritional security and environmental safety for inhabiting masses in arid and semiarid regions.Not Availabl

Abstracts: Golden Jubilee International Salinity Conference (GJISC-2019)

ICAR-Central Soil Salinity Research Institute (CSSRI) during its journey of 50 years, since its inception in 1969, has made impressive contributions in terms of development of technologies for reclamation of salt-affected soils and waters. Besides U.S. Soil Salinity Laboratory, CSSRI is the only institution in the World dedicated to development of technologies for salty land management for crop production. It has been in the forefront, for last five decades, in developing technologies for holistic management of salt-affected soils and waters, and extending them to millions of farmers through robust extension mechanisms. In the context of climate change, the institute is fully geared up to face new challenges for mitigation and adaptation for salt affected scenarios. With its first “International Symposium on Salt-Affected Soils”, which was organized in 1980, the foundation was laid for internationally collaborated efforts to mitigate soil salinity and transform lives of millions of farmers in salt-affected areas worldwide. Since 2009, the institute has been organizing national seminars regularly in collaboration with Indian Society of Soil Salinity and Water Quality (ISSSWQ), and also publishes Journal of Soil Salinity and Water Quality (JSSWQ), to disseminate salinity related research findings. On its Golden Jubilee anniversary, ICAR-CSSRI again proposes Golden Jubilee International Salinity Conference on “Resilient Agriculture in Saline Environments under Changing Climate: Challenges and Opportunities” during 7-9 February 2019 to bring together the national and international scientific fraternity for devising the future roadmap to address the salinity issues in the backdrop of climate change