A Geochemical Study of a Marsh Environment

The goal of this study was twofold: 1) chemically to characterize a specific salt marsh, the sediments and associated biota and 2) to establish clear relationships between the chemical substances residing in the sediments and similar or identical substances occurring in the biological specimens. In this particular study it was felt that the hydrocarbons would yield the most significant organic geochemical information. These compounds are ubiquitous but minor components of all organisms. Though their function is not entirely understood, it is known that they are concentrated in the waxy coatings of plants and most likely aid in the protective mechanisms of plants. Among the several classes of biochemical materials, the hydrocarbons exhibit probably the greatest resistance to biological and chemical degradation and therefore may be preferentially concentrated and preserved in sedimentary environments. An extreme variety of specific hydrocarbons occurs naturally in plants and hence the possible combinations and distributions of these hydrocarbons are limitless. The stability and unique distributions of hydrocarbons ranks them as a very important tool in the correlation of biolipids and geolipids

A Geochemical Study of a Marsh Environment

The goal of this study was twofold: 1) chemically to characterize a specific salt marsh, the sediments and associated biota and 2) to establish clear relationships between the chemical substances residing in the sediments and similar or identical substances occurring in the biological specimens. In this particular study it was felt that the hydrocarbons would yield the most significant organic geochemical information. These compounds are ubiquitous but minor components of all organisms. Though their function is not entirely understood, it is known that they are concentrated in the waxy coatings of plants and most likely aid in the protective mechanisms of plants. Among the several classes of biochemical materials, the hydrocarbons exhibit probably the greatest resistance to biological and chemical degradation and therefore may be preferentially concentrated and preserved in sedimentary environments. An extreme variety of specific hydrocarbons occurs naturally in plants and hence the possible combinations and distributions of these hydrocarbons are limitless. The stability and unique distributions of hydrocarbons ranks them as a very important tool in the correlation of biolipids and geolipids

Genetic Structure of Halodule wrightii Populations from the Laguna Madre Region in the Western Gulf of Mexico

A random amplified polymorphic DNA assay was used to assess genetic variation in populations of the seagrass Halodule wrightii (Ascherson) from the western Gulf of Mexico. This region includes one of the world\u27s few hypersaline lagoons (Laguna Madre) and contains the vast majority of seagrasses on the Texas coast. Results indicate a moderate amount of genetic diversity among populations. The highest level (Hc= 0.33) was found in a population from Nueces Bay, a disturbed site in the Coastal Bend area, whereas the lowest was found in a Lower Laguna Madre population (Hc = 0.15). Genetic differentiation generally followed an isolation-by-distance model. The Nueces Bay population also showed the greatest degree of differentiation, whereas the Redflsh Bay and Lower Laguna Madre populations were relatively similar (φST = 0.091). Combined with previous results, we now have a rudimentary picture of genetic variation in this species from the Texas Gulf Coast

Application of Fiber Optic Instrumentation

Fiber optic sensing technology has emerged in recent years offering tremendous advantages over conventional aircraft instrumentation systems. The advantages of fiber optic sensors over their conventional counterparts are well established; they are lighter, smaller, and can provide enormous numbers of measurements at a fraction of the total sensor weight. After a brief overview of conventional and fiber-optic sensing technology, this paper presents an overview of the research that has been conducted at NASA Dryden Flight Research Center in recent years to advance this promising new technology. Research and development areas include system and algorithm development, sensor characterization and attachment, and real-time experimentally-derived parameter monitoring for ground- and flight-based applications. The vision of fiber optic smart structure technology is presented and its potential benefits to aerospace vehicles throughout the lifecycle, from preliminary design to final retirement, are presented

Structure and spectroscopy of CuH prepared via borohydride reduction

Copper(I) hydride (cuprous hydride, CuH) was the first binary metal hydride to be discovered (in 1844) and is singular in that it is synthesized in solution, at ambient temperature. There are several synthetic paths to CuH, one of which involves reduction of an aqueous solution of CuSO(4)·5H(2)O by borohydride ions. The product from this procedure has not been extensively characterized. Using a combination of diffraction methods (X-ray and neutron) and inelastic neutron scattering spectroscopy, we show that the CuH from the borohydride route has the same bulk structure as CuH produced by other routes. Our work shows that the product consists of a core of CuH with a shell of water and that this may be largely replaced by ethanol. This offers the possibility of modifying the properties of CuH produced by aqueous routes

Spinors, Inflation, and Non-Singular Cyclic Cosmologies

We consider toy cosmological models in which a classical, homogeneous, spinor field provides a dominant or sub-dominant contribution to the energy-momentum tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a field were to exist, appropriate choices of the spinor self-interaction would generate a rich variety of behaviors, quite different from their widely studied scalar field counterparts. We first discuss solutions that incorporate a stage of cosmic inflation and estimate the primordial spectrum of density perturbations seeded during such a stage. Inflation driven by a spinor field turns out to be unappealing as it leads to a blue spectrum of perturbations and requires considerable fine-tuning of parameters. We next find that, for simple, quartic spinor self-interactions, non-singular cyclic cosmologies exist with reasonable parameter choices. These solutions might eventually be incorporated into a successful past- and future-eternal cosmological model free of singularities. In an Appendix, we discuss the classical treatment of spinors and argue that certain quantum systems might be approximated in terms of such fields.Comment: 12 two-column pages, 3 figures; uses RevTeX

Advanced Fiber Optic-Based Sensing Technology for Unmanned Aircraft Systems

This presentation provides an overview of fiber optic sensing technology development activities performed at NASA Dryden in support of Unmanned Aircraft Systems. Examples of current and previous work are presented in the following categories: algorithm development, system development, instrumentation installation, ground R&D, and flight testing. Examples of current research and development activities are provided

Combinatorial localized dissolution analysis : application to acid-induced dissolution of dental enamel and the effect of surface treatments

A combination of scanning electrochemical cell microscopy (SECCM) and atomic force microscopy (AFM) is used to quantitatively study the acid-induced dissolution of dental enamel. A micron-scale liquid meniscus formed at the end of a dual barrelled pipette, which constitutes the SECCM probe, is brought into contact with the enamel surface for a defined period. Dissolution occurs at the interface of the meniscus and the enamel surface, under conditions of well-defined mass transport, creating etch pits that are then analysed via AFM. This technique is applied to bovine dental enamel, and the effect of various treatments of the enamel surface on acid dissolution (1 mM HNO3) is studied. The treatments investigated are zinc ions, fluoride ions and the two combined. A finite element method (FEM) simulation of SECCM mass transport and interfacial reactivity, allows the intrinsic rate constant for acid-induced dissolution to be quantitatively determined. The dissolution of enamel, in terms of Ca2+ flux (jCa2+), is first order with respect to the interfacial proton concentration and given by the following rate law: jCa2+=k0[H+], with k0=0.099±0.008 cm s−1. Treating the enamel with either fluoride or zinc ions slows the dissolution rate, although in this model system the partly protective barrier only extends around 10–20 nm into the enamel surface, so that after a period of a few seconds dissolution of modified surfaces tends towards that of native enamel. A combination of both treatments exhibits the greatest protection to the enamel surface, but the effect is again transient