Effects of Intensive N-K Fertilization on Exchangeable Ca and K in a Soil Profile

Over a 4-yr period fertilizers having three N and five K levels in a factorial arrangement were applied in a replicated, randomized complete block design to coastal bermudagrass (Cynodon dactylon L.) growing on a Pembroke silt loam just north of Fayetteville. In the spring of the fifth year (1972) soil samples were taken from a 3.67-m profile of each plot. Nine depth samples from the profile of each plot were analyzed for exchangeable K and Ca. Potassium fertilizer, especially at the higher rates, and where no N was applied, greatly increased exchangeable K levels only in the top 45 cm of the profile; however, exchangeable Ca levels were decreased markedly in these same upper soil layers, and increased greatly at lower levels in the profile. The first increment of N reduced this effect of K fertilizer on exchangeable Ca, probably because of increased plant growth that resulted from N fertilization; this increased growth removed a larger portion of the fertilizer K. At the higher N rate the net change in exchangeable Ca was greater, but more varied between K treatments, with the highest level of N and K resulting in a net loss of Ca from the 3.67-m profile sampled

Residual Effects of N-K Fertilization of Coastal Bermudagrass on Spring Populations of Weed Species

A Coastal bermudagrass (Cynodon dactylon L.) sod was treated during a five-year period with rates of N and K fertilizers ranging from none to high levels of both elements. In the spring of the sixth year differences in weed species and population densities among the treated plots were observed. Spring weed counts showed that high rates of N fertilizer reduced the number of weed species and the total broadleaf weed population density by 37 and 81%, respectively. The higher rates of K fertilizer also reduced the population density of common dandelion (Taraxacum officinale Weber) and yellow toadflax (Linaria vulgaris Hill),the two dominant broadleaf weed species. The grass weed population, predominantly crabgrass (Digitaria sanguinalis ,L. Scop.) was not affected significantly by either N or K fertilizer levels

Angular Misalignment Measurements for an Off-Plane Reflection Grating Module

We present an analysis of an alignment technique used for an off-plane reflection grating system that, if proven to be feasible, would ideally be utilized for future astronomical x-ray spectrometers. The use of reflection gratings allows for the production of both high throughput and spectral resolution. As such, they are a candidate grating technology for future soft X-ray spectroscopy missions. To be viable for these missions, however, a low-cost optical technique for co-aligning multiple gratings into a module for use in a spectrograph must be demonstrated. The off-plane grating module was built to contain fifteen gratings with proper relative alignment to one another for a converging X-ray beam. The module was coupled with a silicon pore optic mirror to produce a spectrum of reflected and diffracted light onto a CCD camera at the focal plane. The alignment performance of the module’s grating system was assessed both before and after a series of vibrational and thermal tests were conducted at the NASA Marshall Space Flight Center. Data reduction was done in order to identify the number and position of photon events from the diffraction spots for each grating, and raytracing analysis was conducted in order to calculate the induced grating-to-grating angular misalignments. Finally, these measurements were compared to theoretical alignment tolerances derived using analytical techniques. The grating system yielded misalignments within a factor of 2-3 of the analytical tolerances, which is very encouraging for a first attempt. Further refinement and troubleshooting is required to see whether or not this alignment technique can be used in the future

Angular Forces Around Transition Metals in Biomolecules

Quantum-mechanical analysis based on an exact sum rule is used to extract an semiclassical angle-dependent energy function for transition metal ions in biomolecules. The angular dependence is simple but different from existing classical potentials. Comparison of predicted energies with a computer-generated database shows that the semiclassical energy function is remarkably accurate, and that its angular dependence is optimal.Comment: Tex file plus 4 postscript figure

The Marshall Grazing Incidence X-Ray Spectrometer

No abstract availabl

Development Status of Adjustable X-Ray Optics with 0.5 Arcsecond Resolution

We report on the continuing development of adjustable, grazing incidence X-ray optics for 0.5 arcsec telescopes. Adjustable X-ray optics offer the potential for achieving sub-arcsecond imaging resolution while sufficiently thin and light-weight to constitute a mirror assembly with several square meters collecting area. The adjustable mirror concept employs a continuous thin film of piezoelectric material deposited on the back of the paraboloid and hyperboloid mirror segments. Individually addressable electrodes on the piezoelectric layer allow the introduction of deformations in localized "cells" which are used to correct mirror figure errors resulting from fabrication, mounting and aligning the thin mirrors, residual gravity release and temperature changes. We describe recent results of this development. These include improving cell yield to approx. 100 per cent, measurements of hysteresis and stability, comparisons of modeled and measured behavior, simulations of mirror performance, and the development and testing of conical Wolter- I mirror segments. We also present our plans going forward toward the eventual goal of achieving TRL 6 prior to the 2020 Decadal Review

Technology Requirements for a Square Meter, Arcsecond Resolution Telescope for X-Rays: The SMART-X Mission

Addressing the astrophysical problems of the 2020's requires sub-arcsecond x-ray imaging with square meter effective area. Such requirements can be derived, for example, by considering deep x-ray surveys to find the young black holes in the early universe (large redshifts) which will grow into the first super-massive black holes. We have envisioned a mission, the Square Meter Arcsecond Resolution Telescope for X-rays (SMART-X), based on adjustable x-ray optics technology, incorporating mirrors with the required small ratio of mass to collecting area. We are pursuing technology which achieves sub-arcsecond resolution by on-orbit adjustment via thin film piezoelectric "cells" deposited directly on the non-reflecting sides of thin, slumped glass. While SMART-X will also incorporate state-of-the-art x-ray cameras, the remaining spacecraft systems have no requirements more stringent than those which are well understood and proven on the current Chandra X-ray Observatory

Marshall Grazing Incidence

No abstract availabl

Identification of host cell factors required for intoxication through use of modified cholera toxin

We describe a novel labeling strategy to site-specifically attach fluorophores, biotin, and proteins to the C terminus of the A1 subunit (CTA1) of cholera toxin (CTx) in an otherwise correctly assembled and active CTx complex. Using a biotinylated N-linked glycosylation reporter peptide attached to CTA1, we provide direct evidence that ∼12% of the internalized CTA1 pool reaches the ER. We also explored the sortase labeling method to attach the catalytic subunit of diphtheria toxin as a toxic warhead to CTA1, thus converting CTx into a cytolethal toxin. This new toxin conjugate enabled us to conduct a genetic screen in human cells, which identified ST3GAL5, SLC35A2, B3GALT4, UGCG, and ELF4 as genes essential for CTx intoxication. The first four encode proteins involved in the synthesis of gangliosides, which are known receptors for CTx. Identification and isolation of the ST3GAL5 and SLC35A2 mutant clonal cells uncover a previously unappreciated differential contribution of gangliosides to intoxication by CTx.Fundação para a Ciência e a Tecnologia (Fellowship

Lynx Mission Concept Status

Lynx is a concept under study for prioritization in the 2020 Astrophysics Decadal Survey. Providing orders of magnitude increase in sensitivity over Chandra, Lynx will examine the first black holes and their galaxies, map the large-scale structure and galactic halos, and shed new light on the environments of young stars and their planetary systems. In order to meet the Lynx science goals, the telescope consists of a high-angular resolution optical assembly complemented by an instrument suite that may include a High Definition X-ray Imager, X-ray Microcalorimeter and an X-ray Grating Spectrometer. The telescope is integrated onto the spacecraft to form a comprehensive observatory concept. Progress on the formulation of the Lynx telescope and observatory configuration is reported in this paper