Real-time simulation clock

The invention is a clock for synchronizing operations within a high-speed, distributed data processing network. The clock is actually a distributed system comprising a central clock and multiple site clock interface units (SCIUs) which are connected by means of a fiber optic star network and which operate under control of separate clock software. The presently preferred embodiment is a part of the flight simulation system now in current use at the NASA Langley Research Center

The Possible Interstellar Anion CH2CN-: Spectroscopic Constants, Vibrational Frequencies, and Other Considerations

It is hypothesized that the A ^1B_1 <- X ^1A' excitation into the dipole-bound state of the cyanomethyl anion (CH2CN-) is proposed as the carrier for one diffuse interstellar band. However, this particular molecular system has not been detected in the interstellar medium even though the related cyanomethyl radical and the isoelectronic ketenimine molecule have been found. In this study we are employing the use of proven quartic force fields and second-order vibrational perturbation theory to compute accurate spectroscopic constants and fundamental vibrational frequencies for ^1A' CH2CN- in order to assist in laboratory studies and astronomical observations

Diagrammatic Coupled Cluster Monte Carlo

We propose a modified coupled cluster Monte Carlo algorithm that stochastically samples connected terms within the truncated Baker--Campbell--Hausdorff expansion of the similarity transformed Hamiltonian by construction of coupled cluster diagrams on the fly. Our new approach -- diagCCMC -- allows propagation to be performed using only the connected components of the similarity-transformed Hamiltonian, greatly reducing the memory cost associated with the stochastic solution of the coupled cluster equations. We show that for perfectly local, noninteracting systems, diagCCMC is able to represent the coupled cluster wavefunction with a memory cost that scales linearly with system size. The favorable memory cost is observed with the only assumption of fixed stochastic granularity and is valid for arbitrary levels of coupled cluster theory. Significant reduction in memory cost is also shown to smoothly appear with dissociation of a finite chain of helium atoms. This approach is also shown not to break down in the presence of strong correlation through the example of a stretched nitrogen molecule. Our novel methodology moves the theoretical basis of coupled cluster Monte Carlo closer to deterministic approaches.Comment: 31 pages, 6 figure

The effect of lens-induced anisometropia on sterolocalization

Little research has been done to study the effect of anisometropia on the ability of subjects to localize an object in space using binocular depth cues. Rendering a patient artificially anisometropic is similar to prescribing an unbalanced refraction or inducing anisometropia in a monovision contact lens fit. We investigated the effect of induced anisometropia on stereolocalization. Spectacle lenses were used to create the anisometropic conditions and all subjects were pretested for isometropia while wearing their best distance refractive corrections. Thirty-eight subjects judged the distance of a floating vectographic Quoit\u27s Ring target under varying amounts of anisometropia in a featureless field. The amounts of anisometropia induced ranged between 0.50 D and 1.75 D. The results indicate that there is no statistically significant difference in the ability to stereolocalize with up to 1.00 D of anisometropia, however, beyond this limit a statistically significant decrease in performance clearly exists

Techniques used for the analysis of oculometer eye-scanning data obtained from an air traffic control display

The methodology and techniques used to collect and analyze look-point position data from a real-time ATC display-format comparison experiment are documented. That study compared the delivery precision and controller workload of three final approach spacing aid display formats. Using an oculometer, controller lookpoint position data were collected, associated with gaze objects (e.g., moving aircraft) on the ATC display, and analyzed to determine eye-scan behavior. The equipment involved and algorithms for saving, synchronizing with the ATC simulation output, and filtering the data are described. Target (gaze object) and cross-check scanning identification algorithms are also presented. Data tables are provided of total dwell times, average dwell times, and cross-check scans. Flow charts, block diagrams, file record descriptors, and source code are included. The techniques and data presented are intended to benefit researchers in other studies that incorporate non-stationary gaze objects and oculometer equipment

Plant Species Disjunctions

The use of molecular data in the study of plant species disjunctions is reviewed and evaluated. The major reason for employing molecular information is to estimate genetic divergence between morphologically similar disjunct species. Flavonoid chemistry offers few advantages over morphology because it is difficult, if not impossible, to infer genetic divergence from the arrays of flavonoid compounds sequestered by two species. Also, flavonoids can, like morphological characters, undergo stasis. Rather direct evidence for this comes from the fact that extant and fossil species may have identical or nearly identical flavonoids. Enzyme electrophoresis is useful for estimating divergence between disjunct species at gene loci encoding soluble enzymes. Disjunct species pairs in several genera are highly divergent at isozyme loci despite their morphological similarity. Restriction site analysis of chloroplast DNA (cpDNA) has proven useful for measuring divergence between disjunct species. The conservative rate of nucleotide substitutions in cpDNA allows one to estimate (albeit with several assumptions) sequence divergence between the DNAs. Whether isozyme and cpDNA data can be used to estimate divergence times with reasonable confidence remains an open question. In two studies employing both methods, similar divergence times were calculated with each. As two species become more divergent at isozyme loci, the variance in estimates of divergence times becomes larger, and the calculated times become less certain. Despite limitations, enzyme electrophoresis and cpDNA restriction site data are valuable for estimating genetic divergence between disjunct species. Future studies of plant species disjunctions will likely include nucleic acid sequence data. The molecular information should always be part of a broader study of species disjunctions, including detailed investigations of morphological features, chromosome numbers, ecology, and the geological histories of the species