Electromagnetic Propagation Velocities in an Inhomogeneous or Random Atmosphere

This thesis is concerned primarily with determination of statistics for the velocities of propagation of an electromagnetic wave in a dispersive medium. The velocities of propagation are discussed in terms of a plane travelling wave solution of Maxwell\u27s equations obtained using the multiple Laplace transformation and complex inversion integrals. The types of dispersion discussed correspond to a magneto-ionic, electron displacement and polar resonances of the ionosphere and troposphere. The physical nature of the randomness of the dispersive index of refraction is derived from considerations of statistical turbulence theory. Expressions are then obtained for determining the mean, mean square and variance of the signal, group and phase velocity of an electromagnetic wave. It is proposed by S. M. Harris (IRE Trans. Vol. AP-9, No. 2, pp. 207-210, Mar., 1961) that the group velocity and phase velocity of an electromagnetic wave propagated in the ionosphere may be averaged to obtain a velocity estimate free of refraction to within second order refractive effects. The basis for this procedure is that for an operating frequency considerably above the critical frequencies of the ionospheric medium, the group velocity is slightly less than the velocity of light

My Budding Rose

https://digitalcommons.library.umaine.edu/mmb-vp/4416/thumbnail.jp

Laser-Doppler Measurements of the Decay of Velocity Fluctuations in Dilute Polymer Solutions

Finite disturbances were generated in a pipe containing water or a 20 ppm solution of Separan AP-30 in water by oscillating a sleeve at the wall. The sleeve amplitude in the axial direction varied from 0.5 to 2.0 inches and the frequency from 0.25 to 1.0 Hz. Downstream of the sleeve oscillations in the fluid velocity were measured with a laser Doppler flowmeter at various axial and radial positions to determine behavior at the lower frequency part of the stability curve for water. The response amplitude, phase angle and the mean velocities were measured for both fluids at Reynolds numbers from 500 to 2100. The water response was frequency dependent in the experimental range. Transitions from well defined velocity fluctuations following the disturbance frequency to random responses were noted as the frequency changed from 0.25 Hz to 1.0 Hz. The dilute polymer solutions showed reduced response amplitudes and always had well defined fluctuations indicating that the stability limit is at a higher frequency than that for water

Competency Levels of and Pre-service Training Received by County Cooperative Extension Service Agriculture Agents in Oklahoma Relative to Light Horses

Agricultural Educatio

Performance of a Quaternary Logic Design

This paper analyzes the performance of a quaternary logic circuit and its components. The multi-valued logic design consisting of two drivers and a transistor matrix is simulated using Mentor Graphic software. Functional operation of the circuit is shown and propagation delay and power consumption are determined. The design is dependent on the voltage values for the multi-valued logic. Three logic cases are investigated. The performance of the logic circuit as a quaternary difference calculator is described

The Importance of DNA Repair in Tumor Suppression

The transition from a normal to cancerous cell requires a number of highly specific mutations that affect cell cycle regulation, apoptosis, differentiation, and many other cell functions. One hallmark of cancerous genomes is genomic instability, with mutation rates far greater than those of normal cells. In microsatellite instability (MIN tumors), these are often caused by damage to mismatch repair genes, allowing further mutation of the genome and tumor progression. These mutation rates may lie near the error catastrophe found in the quasispecies model of adaptive RNA genomes, suggesting that further increasing mutation rates will destroy cancerous genomes. However, recent results have demonstrated that DNA genomes exhibit an error threshold at mutation rates far lower than their conservative counterparts. Furthermore, while the maximum viable mutation rate in conservative systems increases indefinitely with increasing master sequence fitness, the semiconservative threshold plateaus at a relatively low value. This implies a paradox, wherein inaccessible mutation rates are found in viable tumor cells. In this paper, we address this paradox, demonstrating an isomorphism between the conservatively replicating (RNA) quasispecies model and the semiconservative (DNA) model with post-methylation DNA repair mechanisms impaired. Thus, as DNA repair becomes inactivated, the maximum viable mutation rate increases smoothly to that of a conservatively replicating system on a transformed landscape, with an upper bound that is dependent on replication rates. We postulate that inactivation of post-methylation repair mechanisms are fundamental to the progression of a tumor cell and hence these mechanisms act as a method for prevention and destruction of cancerous genomes.Comment: 7 pages, 5 figures; Approximation replaced with exact calculation; Minor error corrected; Minor changes to model syste

Probing protein sequences as sources for encrypted antimicrobial peptides

Starting from the premise that a wealth of potentially biologically active peptides may lurk within proteins, we describe here a methodology to identify putative antimicrobial peptides encrypted in protein sequences. Candidate peptides were identified using a new screening procedure based on physicochemical criteria to reveal matching peptides within protein databases. Fifteen such peptides, along with a range of natural antimicrobial peptides, were examined using DSC and CD to characterize their interaction with phospholipid membranes. Principal component analysis of DSC data shows that the investigated peptides group according to their effects on the main phase transition of phospholipid vesicles, and that these effects correlate both to antimicrobial activity and to the changes in peptide secondary structure. Consequently, we have been able to identify novel antimicrobial peptides from larger proteins not hitherto associated with such activity, mimicking endogenous and/or exogenous microorganism enzymatic processing of parent proteins to smaller bioactive molecules. A biotechnological application for this methodology is explored. Soybean (Glycine max) plants, transformed to include a putative antimicrobial protein fragment encoded in its own genome were tested for tolerance against Phakopsora pachyrhizi, the causative agent of the Asian soybean rust. This procedure may represent an inventive alternative to the transgenic technology, since the genetic material to be used belongs to the host organism and not to exogenous sources

High speed jet noise research at NASA Lewis

The source noise portion of the High Speed Research Program at NASA LeRC is focused on jet noise reduction. A number of jet noise reduction concepts are being investigated. These include two concepts, the Pratt & Whitney ejector suppressor nozzle and the General Electric (GE) 2D-CD mixer ejector nozzle, that rely on ejectors to entrain significant amounts of ambient air to mix with the engine exhaust to reduce the final exhaust velocity. Another concept, the GE 'Flade Nozzle' uses fan bypass air at takeoff to reduce the mixed exhaust velocity and to create a fluid shield around a mixer suppressor. Additional concepts are being investigated at Georgia Tech Research Institute and at NASA LeRC. These will be discussed in more detail in later figures. Analytical methods for jet noise prediction are also being developed. Efforts in this area include upgrades to the GE MGB jet mixing noise prediction procedure, evaluation of shock noise prediction procedures, and efforts to predict jet noise directly from the unsteady Navier-Stokes equation

Automatic and controlled sentence production: a computational model

We present a computational model of sentence production that emulates variation of the output of lexicalization and grammatical encoding of the abstract pre-lexical message, in terms of complexity and accuracy of the generated sentence as well as fluency and cognitive costs of the sentence production. The model integrates approaches from routine action selection models built on Dual Systems Theory (Norman & Shallice, 1986) with ‘A Blueprint for the Speaker’ developed by Levelt (1989). The paper describes and justifies the model architecture, explores factors affecting language variation in production, and applies the model for testing relationship between complexity, accuracy, and fluency (CAF) of language production as debated within Second Language Acquisition (SLA) research. A simulation that generated 78,750 sentences provides evidence of the trade-off relationship between CAF parameters as speakers have to sacrifice performance on one of the CAF factors in order to improve the remaining two