3,021 research outputs found

    Understanding Acre for Cotton

    Get PDF
    The Food, Conservation, and Energy Act of 2008 was passed into law on May 22, 2008 with veto override votes in the House of Representatives and the Senate (House 2008). A difference between the 2002 and the 2008 bills is the newly instituted revenue-based counter-cyclical program called the Average Crop Revenue Election (ACRE) program available beginning crop year 2009. The ACRE program is offered as an alternative to the counter-cyclical payment (CCP) program that was in place during the 2002-2008 period. Beginning with the 2009 crop year, producers will have the option to enroll their farm in either the CCP program or the ACRE program. If ACRE is elected, producers cannot change program participation for the duration of the 2008 farm bill (ERS 2008). This is a very complex decision due to the number of variables that must be considered and depends on the individual farm situation. It requires that farms, rather than crops or commodities, enter the program, so that the decision relies on the impacts of program choice on farm income. That aside, understanding commodity situations is a first step toward understanding and making decisions on individual farm situations. The purpose of this briefing paper is to provide assistance in understanding the differences between the ACRE and CCP programs for one crop, cotton, in one state, Texas. The briefing paper will also show the results of a comparison between CCP and ACRE payments using a sample of actual farm data.Agricultural and Food Policy,

    The ion-induced charge-exchange X-ray emission of the Jovian Auroras: Magnetospheric or solar wind origin?

    Get PDF
    A new and more comprehensive model of charge-exchange induced X-ray emission, due to ions precipitating into the Jovian atmosphere near the poles, has been used to analyze spectral observations made by the Chandra X-ray Observatory. The model includes for the first time carbon ions, in addition to the oxygen and sulfur ions previously considered, in order to account for possible ion origins from both the solar wind and the Jovian magnetosphere. By comparing the model spectra with newly reprocessed Chandra observations, we conclude that carbon ion emission provides a negligible contribution, suggesting that solar wind ions are not responsible for the observed polar X-rays. In addition, results of the model fits to observations support the previously estimated seeding kinetic energies of the precipitating ions (~0.7-2 MeV/u), but infer a different relative sulfur to oxygen abundance ratio for these Chandra observations.Comment: 11 pages, 2 figures, 2 tables, submitted to ApJ Lette

    The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets

    Get PDF
    The size of a planet is an observable property directly connected to the physics of its formation and evolution. We used precise radius measurements from the California-Kepler Survey (CKS) to study the size distribution of 2025 Kepler\textit{Kepler} planets in fine detail. We detect a factor of ≥\geq2 deficit in the occurrence rate distribution at 1.5-2.0 R⊕_{\oplus}. This gap splits the population of close-in (PP < 100 d) small planets into two size regimes: RP_P < 1.5 R⊕_{\oplus} and RP_P = 2.0-3.0 R⊕_{\oplus}, with few planets in between. Planets in these two regimes have nearly the same intrinsic frequency based on occurrence measurements that account for planet detection efficiencies. The paucity of planets between 1.5 and 2.0 R⊕_{\oplus} supports the emerging picture that close-in planets smaller than Neptune are composed of rocky cores measuring 1.5 R⊕_{\oplus} or smaller with varying amounts of low-density gas that determine their total sizes.Comment: Paper III in the California-Kepler Survey series, accepted to the Astronomical Journa

    Molecular and Cellular Biology Animations: Development and Impact on Student Learning

    Get PDF
    Educators often struggle when teaching cellular and molecular processes because typically they have only two-dimensional tools to teach something that plays out in four dimensions. Learning research has demonstrated that visualizing processes in three dimensions aids learning, and animations are effective visualization tools for novice learners and aid with long-term memory retention. The World Wide Web Instructional Committee at North Dakota State University has used these research results as an inspiration to develop a suite of high-quality animations of molecular and cellular processes. Currently, these animations represent transcription, translation, bacterial gene expression, messenger RNA (mRNA) processing, mRNA splicing, protein transport into an organelle, the electron transport chain, and the use of a biological gradient to drive adenosine triphosphate synthesis. These animations are integrated with an educational module that consists of First Look and Advanced Look components that feature captioned stills from the animation representing the key steps in the processes at varying levels of complexity. These animation-based educational modules are available via the World Wide Web at http://vcell.ndsu.edu/animations. An in-class research experiment demonstrated that student retention of content material was significantly better when students received a lecture coupled with the animations and then used the animation as an individual study activity

    Climate Change and Biosphere Response: Unlocking the Collections Vault

    Full text link
    Natural history collections (NHCs) are an important source of the long-term data needed to understand how biota respond to ongoing anthropogenic climate change. These include taxon occurrence data for ecological modeling, as well as information that can be used to reconstruct mechanisms through which biota respond to changing climates. The full potential of NHCs for climate change research cannot be fully realized until high-quality data sets are conveniently accessible for research, but this requires that higher priority be placed on digitizing the holdings most useful for climate change research (e.g., whole-biota studies, time series, records of intensively sampled common taxa). Natural history collections must not neglect the proliferation of new information from efforts to understand how present-day ecosystems are responding to environmental change. These new directions require a strategic realignment for many NHC holders to complement their existing focus on taxonomy and systematics. To set these new priorities, we need strong partnerships between NHC holders and global change biologists

    The California-Kepler Survey. I. High Resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets

    Get PDF
    The California-Kepler Survey (CKS) is an observational program to improve our knowledge of the properties of stars found to host transiting planets by NASA's Kepler Mission. The improvement stems from new high-resolution optical spectra obtained using HIRES at the W. M. Keck Observatory. The CKS stellar sample comprises 1305 stars classified as Kepler Objects of Interest, hosting a total of 2075 transiting planets. The primary sample is magnitude-limited (Kp < 14.2) and contains 960 stars with 1385 planets. The sample was extended to include some fainter stars that host multiple planets, ultra short period planets, or habitable zone planets. The spectroscopic parameters were determined with two different codes, one based on template matching and the other on direct spectral synthesis using radiative transfer. We demonstrate a precision of 60 K in effective temperature, 0.10 dex in surface gravity, 0.04 dex in [Fe/H], and 1.0 km/s in projected rotational velocity. In this paper we describe the CKS project and present a uniform catalog of spectroscopic parameters. Subsequent papers in this series present catalogs of derived stellar properties such as mass, radius and age; revised planet properties; and statistical explorations of the ensemble. CKS is the largest survey to determine the properties of Kepler stars using a uniform set of high-resolution, high signal-to-noise ratio spectra. The HIRES spectra are available to the community for independent analyses.Comment: 20 pages, 19 figures, accepted for publication in AJ; a full version of Table 5 is included as tab_cks.csv and tab_cks.te

    The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars

    Get PDF
    We present stellar and planetary properties for 1305 Kepler Objects of Interest (KOIs) hosting 2025 planet candidates observed as part of the California-Kepler Survey. We combine spectroscopic constraints, presented in Paper I, with stellar interior modeling to estimate stellar masses, radii, and ages. Stellar radii are typically constrained to 11%, compared to 40% when only photometric constraints are used. Stellar masses are constrained to 4%, and ages are constrained to 30%. We verify the integrity of the stellar parameters through comparisons with asteroseismic studies and Gaia parallaxes. We also recompute planetary radii for 2025 planet candidates. Because knowledge of planetary radii is often limited by uncertainties in stellar size, we improve the uncertainties in planet radii from typically 42% to 12%. We also leverage improved knowledge of stellar effective temperature to recompute incident stellar fluxes for the planets, now precise to 21%, compared to a factor of two when derived from photometry.Comment: 13 pages, 4 figures, 4 tables, accepted for publication in AJ; full versions of tables 3 and 4 are include
    • …
    corecore