Biochemical processes in sagebrush ecosystems: Interactions with terrain

The objectives of a biogeochemical study of sagebrush ecosystems in Wyoming and their interactions with terrain are as follows: to describe the vegetational pattern on the landscape and elucidate controlling variables, to measure the soil properties and chemical cycling properties associated with the vegetation units, to associate soil properties with vegetation properties as measured on the ground, to develop remote sensing capabilities for vegetation and surface characteristics of the sagebrush landscape, to develop a system of sensing snow cover and indexing seasonal soil to moisture; and to develop relationships between temporal Thematic Mapper (TM) data and vegetation phenological state

A Revised Geometry for the Magnetic Wind of theta^1 Orionis C

Theta^1 Ori is thought to be a hot analog of Bp variables because its optical and UV line and X-ray continuum fluxes modulate regularly over the magnetic/rotational period. A flattened magnetosphere surrounding co-rotates with these stars, producing a periodic modulation of emission and absorption components of the UV resonance lines, as well as of optical H and He lines. In this paper we examine these modulations in detail and point out that the far-blue and near-red wings of C IV and N V resonance lines exhibit anticorrelated modulations, causing mild flux elevations at moderate redshifts at edge-on phase (phi=0.5). However, the lines do not exhibit rest-frame absorption features, the usual signatures of cool static disks surrounding Bp stars. We suggest that this behavior can be explained by the existence of two geometrically distinct wind regions separated by the local magnetic Alfven radius. Wind streams emerging outside this point are forced outward by radiative forces and eventually expand outward radially to infinity - this matter produces the far-blue wing absorptions at phi=0.5. Interior streams follow closed loops and collide at the magnetic equator with counterstreams. There they coalesce and fall back to the star along their original field lines - these are responsible for mild emissions at this same phase. The rapid circulation of the interior wind component back to the star is responsible for the absence of static disk features.Comment: 7 figure

Electron Beam Testing of Passivated Devices via Capacitive Coupling Voltage Contrast

By fundamental experiments and theoretical treatments a detailed understanding of the capacitive coupling voltage contrast {CCVC) has been gained, demonstrating that this technique is, in principle, applicable to a non-destructive testing of passivated integrated circuits (IC) by means of electron beams. In fact, however, several problems have to be eliminated in order to introduce this testing technique into a production line procedure. In a first step, preconditions have to be met. These are a primary electron (PE) energy where the electron yield is greater than one and a sufficiently low extraction field above the IC. Secondly, as CCVC vanishes within a certain time span caused by charge compensation during electron irradiation, several precautions have to be undertaken. To obtain unfalsified CCVC-micrographs a fast image recording and processing system has to be realized; for IC-internal waveform measurements suitable sampling electronics have to be developed. Besides this, the resulting measurement errors are classified and determined. These are the error due to charge compensation on the passivation layer during electron irradiation, the error due to an incomplete coupling of the line potential to the passivation surface and the error due to capacitive coupling cross talk from neighboring lines

Extremely low long‐term erosion rates around the Gamburtsev Mountains in interior East Antarctica

The high elevation and rugged relief (>3 km) of the Gamburtsev Subglacial Mountains (GSM) have long been considered enigmatic. Orogenesis normally occurs near plate boundaries, not cratonic interiors, and large‐scale tectonic activity last occurred in East Antarctica during the Pan‐African (480–600 Ma). We sampled detrital apatite from Eocene sands in Prydz Bay at the terminus of the Lambert Graben, which drained a large pre‐glacial basin including the northern Gamburtsev Mountains. Apatite fission‐track and (U‐Th)/He cooling ages constrain bedrock erosion rates throughout the catchment. We double‐dated apatites to resolve individual cooling histories. Erosion was very slow, averaging 0.01–0.02 km/Myr for >250 Myr, supporting the preservation of high elevation in interior East Antarctica since at least the cessation of Permian rifting. Long‐term topographic preservation lends credence to postulated high‐elevation mountain ice caps in East Antarctica since at least the Cretaceous and to the idea that cold‐based glaciation can preserve tectonically inactive topography

The engineering design integration (EDIN) system

A digital computer program complex for the evaluation of aerospace vehicle preliminary designs is described. The system consists of a Univac 1100 series computer and peripherals using the Exec 8 operating system, a set of demand access terminals of the alphanumeric and graphics types, and a library of independent computer programs. Modification of the partial run streams, data base maintenance and construction, and control of program sequencing are provided by a data manipulation program called the DLG processor. The executive control of library program execution is performed by the Univac Exec 8 operating system through a user established run stream. A combination of demand and batch operations is employed in the evaluation of preliminary designs. Applications accomplished with the EDIN system are described

Geometry Technology Module (GTM). Volume 2: Programmers' manual

For abstract, see N75-17120

Capacitive Coupling Voltage Contrast

Capacitive coupling voltage contrast (CCVC) allows electron-beam testing of passivated integrated circuits (IC) without radiation damage or prior, time-consuming specimen preparation. This effect occurs when low primary electron energies are used and the electron yield of the passivation layer is greater than 1. Signal changes in the relevant interconnections are transferred to the passivation surface via capacitive coupling, but they vanish there within the storage time due to electron irradiation. A physical model explains the dependence of CCVC on three parameters: electron irradiation, the passivation material and the signals within the IC. Computer simulations based on this model describe the experimentally-obtained dependencies of the storage time with precision and al low predictions to be made for using CCVC in electron beam testing. The requisite modifications to the electron beam testing system are described and the possible uses of CCVC for testing passivated devices within IC are demonstrated on the basis of examples

Natural age dispersion arising from the analysis of broken crystals, part II. Practical application to apatite (U-Th)/He thermochronometry

We describe a new numerical inversion approach to deriving thermal history information from a range of naturally dispersed single grain apatite (U-Th)/He ages. The approach explicitly exploits the information about the shape of the 4He diffusion profile within individual grains that is inherent in the pattern of dispersion that arises from the common and routine practice of analysing broken crystals. Additional dispersion arising from differences in grain size and in U and Th concentration of grains, and the resultant changes to helium diffusivity caused by differential accumulation and annealing of radiation damage, is explicitly included. In this approach we calculate the ingrowth and loss, due to both thermal diffusion and the effects of α-ejection, of helium over time using a finite cylinder geometry. Broken grains are treated explicitly as fragments of an initially larger crystal. The initial grain lengths, L0, can be treated as unknown parameters to be estimated, although this is computationally demanding. A practical solution to the problem of solving for the unknown initial grain lengths is to simply apply a constant and sufficiently long L0 value to each fragment. We found that a good value for L0 was given by the maximum fragment length plus two times the maximum radius of a given set of fragments. Currently whole crystals and fragments with one termination are taken into account. A set of numerical experiments using synthetic fragment ages generated for increasingly complex thermal histories, and including realistic amounts of random noise (5-15%), are presented and show that useful thermal history information can be extracted from datasets showing very large dispersion. These include experiments where dispersion arises only from fragmentation of a single grain (length 400μm and radius 75μm, c. 6-50% dispersion), including the effects of grain size variation (for spherical equivalent grain radii between 74-122 μm, c. 10-70% dispersion) and the combined effects of fragmentation, grain size and radiation damage (for eU between 5-150 ppm, c.10-107% dispersion). Additionally we show that if the spherical equivalent radius of a broken grain is used as a measure of the effective diffusion domain for thermal history inversions then this will likely lead to erroneous thermal histories being obtained in many cases. The viability of the new technique is demonstrated for a real data set of 25 single grain (U-Th)/He apatite ages obtained for a gabbro sample from the BK-1 (Bierkraal) borehole drilled through the Bushveld Complex in South Africa. The inversion produces a well constrained thermal history consistent with both the (U-Th)/He data and available fission track analysis data. The advantage of the new approach is that it can explicitly accommodate all the details of conventional schemes, such as the effects of temporally variable diffusivity, zonation of U and Th and arbitrary grain size variations, and it works equally effectively for whole or broken crystals, and for the most common situation where a mixture of both are analysed. For the routine application of the apatite (U-Th)/He thermochronometry technique with samples where whole apatite grains are rare our experiments indicate that 15-20 single grain analyses are typically required to characterise the age dispersion pattern of a sample. The experiments also suggest that picking very short crystal fragments as well as long fragments, or even deliberately breaking long crystals to maximise the age dispersion in some cases, would ensure the best constraints on the thermal history models. The inversion strategy described in this paper is likely also directly applicable to other thermochronometers, such as the apatite, rutile and titanite U-Pb systems, where the diffusion domain is approximated by the physical grain size