Chapter 1. The Nitrogen Cycle, Historical Perspective, and Current and Potential Future Concerns

Nitrogen (N) along with carbon and oxygen is the most complex and crucial of the elements essential for life. Supplementing grain and grass forage crops with organic and inorganic N fertilizers has long been recognized as a key to improving crop yields and economic returns. Globally. N fertilizer is largely used for cereal grain production and accounts for an estimated 40(1r of the increase in per capita food production in the past 50 years (Mosier et al.. 200 I). Smil (200 I) estimates that N fertilizer supplies up to 40% of the world\u27s dietary protein and dependence on N from the Haber-Bosch process will increase in the future. Nitrogen compounds also have been recognized for their many potential adverse impacts on the environment and health (Keeney. 2002)

Absolute Proper Motion of the Fornax Dwarf Spheroidal Galaxy from Photographic and HST WFPC2 Data

We have measured the absolute proper motion of the Fornax dwarf spheroidal galaxy from a combination of photographic plate material and HST WFPC2 data that provide a time baseline of up to 50 years. The extragalactic reference frame consists of 8 QSO images and 48 galaxies. The absolute proper motion is mu_alpha cos(delta) = 0.59 +-0.16 mas/yr and mu_delta = -0.15 +- 0.16 mas/yr. The corresponding orbit of Fornax is polar, with an eccentricity of 0.27, and a radial period of 4.5 Gyr. Fornax's current location is near pericenter. The direction of the motion of Fornax supports the notion that Fornax belongs to the Fornax-LeoI-LeoII-Sculptor-Sextans stream as hypothesized by Lynden-Bell (1976, 1982) and Majewski (1994). According to our orbit determination, Fornax crossed the Magellanic plane \~190 Myr ago, a time that coincides with the termination of the star-formation process in Fornax. We propose that ram-pressure stripping due to the passage of Fornax through a gaseous medium denser than the typical intragalactic medium left behind from the LMC may have caused the end of star formation in Fornax. The excess, anomalous clouds within the South Galactic pole region of the Magellanic Stream whose origin has long been debated in the literature as constituents of either the Magellanic Stream or of the extragalactic Sculptor group, are found to lie along the orbit of Fornax. We speculate that these clouds are stripped material from Fornax as the dwarf crossed the Magellanic Clouds' orbit.Comment: Accepted for publication in Astronomical Journal. The version with high resolution figures can be found at ftp://pegasus.astro.yale.edu/pub/dana/paper

Effects of nitrification inhibitors on chemical composition of plants: A review

The potential of nitrification inhibitors to improve N fertilizer efficiency is well recognized. However, their effects on crop quality have received much less attention. Recent literature pertaining to the effects of nitrification inhibitors on chemical composition of plants is reviewed. The topics examined include how the form of inorganic N and retardation of nitrification affects accumulation and content of protein and nitrogenous compounds, cations and anions, and organic acids. There is ample evidence to suggest that nitrification inhibitors hold promise to improve the quality of crops in situations where accumulation of NO− 3 or organic acids such as oxalic acid is a problem. There is need for future research to examine how nitrification retardation affects cation‐anion balance in plants under field conditions because experiments conducted under controlled conditions and in the field have at times given divergent results. Since the use of nitrification inhibitors is increasing, investigations to evaluate their use to improve crop quality In addition to quantity should receive priority

Nitrogen transformations in flooded rice soils

Transformations of soil and fertilizer N in lowland rice soils are reviewed in relation to improved N management and the N economy of lowland rice soils. Topics discussed include: nitrogen leaching, ammonium fixation and release, ammonia volatilization, N2 fixation, mineralization-immobilization, nitrification-denitrification, dissimilatory nitrate reduction, urea hydrolysis and critical pathways for control of nitrogen loss

Perspectives for research on development of nitrification inhibitors

A brief review of the present status and scope of research on nitrification inhibitors pertaining to agricultural production and environmental pollution is presented. An approach is advanced for identification and evaluation of nitrification inhibitors from indigenous resources. Concurrently, research to identify functional groups retarding nitrification would be conducted. These approaches will aid in developing inexpensive and effective materials for nitrification inhibition. Future research needs relating to nitrification inhibitors are also examined

Pheromone Exposure Influences Preoptic Arginine Vasotocin Gene Expression and Inhibits Social Approach Behavior in Response to Rivals but not Potential Mates

The nonapeptides arginine vasotocin (AVT) and vasopressin mediate a variety of social behaviors in vertebrates. However, the effects of these peptides on behavior can vary considerably both between and within species. AVT, in particular, stimulates aggressive and courtship responses typical of dominant males in several species, although it can also inhibit social interactions in some cases. Such differential effects may depend upon AVT influences within brain circuits that differ among species or between males that adopt alternative reproductive phenotypes and/or upon the differential activation of those circuits in different social contexts. However, to date, very little is known about how social stimuli that promote alternative behavioral responses influence AVT circuits within the brain. To address this issue, we exposed adult male goldfish to androstenedione (AD), a pheromonal signal that is released by both males and females during the breeding season, and measured social approach responses of males towards same- and other-sex individuals before and after AD exposure. In a second experiment, we measured AD-induced AVT gene expression using in situ hybridization. We found that brief exposure to AD induces social avoidance in response to rival males, but does not affect the level of sociality exhibited in response to sexually receptive females. Exposure to AD also increases AVT gene expression in the preoptic area of male goldfish, particularly in the parvocellular population of the preoptic nucleus. Together, these data suggest that AD is part of a social signaling system that induces social withdrawal specifically during male-male interactions by activating AVT neurons

From aptamer-based biomarker discovery to diagnostic and clinical applications: an aptamer-based, streamlined multiplex proteomic assay

Recently, we reported an aptamer-based, highly multiplexed assay for the purpose of biomarker identification. To enable seamless transition from highly multiplexed biomarker discovery assays to a format suitable and convenient for diagnostic and life-science applications, we developed a streamlined, plate-based version of the assay. The plate-based version of the assay is robust, sensitive (sub-picomolar), rapid, can be highly multiplexed (upwards of 60 analytes), and fully automated. We demonstrate that quantification by microarray-based hybridization, Luminex bead-based methods, and qPCR are each compatible with our platform, further expanding the breadth of proteomic applications for a wide user community

Very Isolated Early-Type Galaxies

We use the Karachentseva (1973) ``Catalogue of Very Isolated Galaxies'' to investigate a candidate list of >100 very isolated early-type galaxies. Broad-band imaging and low resolution spectroscopy are available for a large fraction of these candidates and result in a sample of 102 very isolated early-type galaxies, including 65 ellipticals and 37 S0 galaxies. Many of these systems are quite luminous and the resulting optical luminosity functions of the Es and early-types (E+S0s) show no statistical differences when compared to luminosity functions dominated by group and cluster galaxies. However, whereas S0s outnumber Es 4:1 in the CfA survey, isolated Es outnumber S0s by nearly 2:1. We conclude that very isolated elliptical galaxies show no evidence for a different formation and/or evolution process compared to Es formed in groups or clusters, but that most S0s are formed by a mechanism (e.g., gas stripping) that occurs only in groups and rich clusters. Our luminosity function results for ellipticals are consistent with very isolated ellipticals being formed by merger events, in which no companions remain. CHANDRA observations were proposed to test specifically the merger hypothesis for isolated ellipticals. However, this program has resulted in the observation of only one isolated early-type galaxy, the S0 KIG 284, which was not detected at a limit well below that expected for a remnant group of galaxies. Therefore, the hypothesis remains untested that very isolated elliptical galaxies are the remains of a compact group of galaxies which completely merged.Comment: 19 pages, 3 figures; AJ in pres