Showing papers by "Virginia Tech published in 1977"

On the Unique Consistent Solution to the Likelihood Equations

Abstract: Existence of a unique consistent solution to the likelihood equations is obtained as a consequence of the Inverse Function Theorem. The approach differs from those already in the literature by showing existence and uniqueness in one argument. The argument deals directly with the vector parameter case rather than with extending single parameter arguments.

Peroxidase and its relationship to food flavor and quality: a review

Abstract: The effect of peroxidase on food flavor and quality is discussed, and its use as an index of blanching fruits and vegetables reviewed. Peroxidase is considered the most heat stable enzyme in plants. If inactivated, all ofher enzyme systems are usually inactivated in the product. There is an empirical relationship between residual peroxidase activity and the development of off-flavors and off-odors in foods. Peroxidase activity has been detected in products stored at — 18°C and under moisture conditions as low as 12.5% moisture. Any activity detected following severe heat treatments is usually due to the enzyme not being wholly inactivated. Inadequate thermal processing may result in regeneration of the enzyme.

Evolution of Anoline Lizard Display Behavior

Abstract: Based on my conceptual framework of anoline display behavior, I am suggesting the following evolutionary trends. Lateral presentation during display was probably promoted by monocular vision. Along with lateral presentation, postures evolved to increase lateral outline. These postures which magnified body size were probably of selective advantage within aggressive social contexts since larger animals tend to dominate smaller ones through bluff. Body movement evolved along with lateral orientation and size-enhancing postures. These movements would be most effective if they complemented lateral orientation. Effectors available for such movements were primarily pre-adapted for vertical motion. The patterns of movement generated were probably simple oscillatory bobbing movements by the head which were weakly stereotyped, interspecifically similar, appearing in many contexts, and having a weakly defined information content. Events having selective advantage for species recognition promoted stereotypy of bobbing behavior into species-unique displays; each species had its unique signature display which served in a manifold communicatory capacity. The signature display appeared in assertion, courtship, and challenge contexts. Its information content varied depending upon context and recipient of the display (e.g., male or female). Besides the stereotyped aspects of the display, certain features remained variable with potential information significance. Core variability (see text) promotes individual recognition and may be the origin of new unique display patterns as sibling species emerge. Display modifiers (see text) are variable display features shared by members of a population (many being shared interspecifically) that provide a graded appearance to display performance; modifiers can indicate level of arousal and facilitate interspecific communication. For some species display repertoire size seems to have evolved from a single display (signature display) to repertoires of multiple displays; these subsequent displays are generally restricted to aggressive interactions.

Maneuvering Target Tracking Using Adaptive State Estimation

Abstract: Two approaches to a nonlinear state estimation problem are presented. The particular problem addressed is that of tracking a maneuvering target in three-dimensional space using spherical observations (radar data). Both approaches rely on semi-Markov modeling of target maneuvers and result in effective algorithms that prevent the loss of track that often occurs when a target makes a sudden, radical change in its trajectory. Both techniques are compared using real and simulated radar measurements with emphasis on performance and computational burden.

The importance of perceived control: fact or fantasy?

Abstract: : A number of experimental investigations on both humans and animals are described. The results of these experiments, when taken together, lead to the conclusion that under certain conditions offering a choice can lead to the perception that one has control, which in turn significantly increases performance relative to those who do not perceive control. The implications and potential implications of these findings are discussed.

Edge Effects in Angle-Ply Composite Laminates*:

Abstract: This paper presents the results of a zeroth-order solution for edge effects in angle-ply composite laminates obtained using perturbation techniques and a limiting free body approach. The general solution for edge effects in laminates of arbitrary angle ply is applied to the special case of a (+ or - 45)s graphite/epoxy laminate. Interlaminar stress distributions are obtained as a function of the laminate thickness-to-width ratio and compared to finite difference results. The solution predicts stable, continuous stress distributions, determines finite maximum tensile interlaminar normal stress and provides mathematical evidence for singular interlaminar shear stresses in (+ or - 45) graphite/epoxy laminates.

Cosmological upper bound on heavy-neutrino lifetimes

Abstract: An upper bound on the lifetime of a massive, neutral, weakly interacting lepton, ${\ensuremath{ u}}_{H}$, is derived from standard big-bang cosmology. Saturation of the bound and reasonable assumptions about the weak interaction of the ${\ensuremath{ u}}_{H}$ then yield a prediction of approximately 10 MeV for its mass.

Classroom Reward Structures and Academic Performance

Abstract: Classroom reward structures refer to the performance criteria, contingencies, or standards that students must satisfy in order to receive presumably valued or reinforcing consequences such as prizes or high grades. The reward structure typical of most classrooms appears to be some compromise between indirect individual competition, in which grades are assigned to students based on their performances relative to those of their classmates (i.e., the curve), and individual reward contingencies, in which grades are assigned to students on the basis of how much material each student apparently masters (i.e., the percent mastery criterion). The typical classroom reward structure has been increasingly criticized as being less effective than alternative reward structures in strengthening the academic performances of students (e.g., Deutsch, 1949a, 1949b; Coleman, 1959; Spilerman, 1971; and Johnson & Johnson, 1974). The critics have urged more frequent use of group reward structures (i.e., group reward contingencies and intergroup competition) and less frequent use of individual reward structures (i.e., individual reward contingencies and individual competition) in schools. In addition, the critics have presented strong evidence that group reward structures more effectively strengthen certain process variables such as cooperation (i.e., collaboration and coordination), interpersonal attraction among group members, and positive attitudes towards tasks, as well as actual performance on tasks requiring cooperative interaction (i.e., interdependent tasks) such as group discussion and problem solving (e.g., Johnson & Johnson, 1974). However, attempts to demonstrate that group

Penetration and Breakup of Liquids in Subsonic Airstreams

Abstract: An experimental study of the penetration and breakup of liquid jets injected normal to high subsonic speed (A/=0.45 and 0.75) airstreams through injection ports of various geometries and sizes is reported. The measurement techniques were primarily optical, employing 2.5 x 10 ~3-sec photos to produce "streak" pictures for penetration measurements and 10 6 and 10 ~8-sec spark photos to show the details of the breakup process and some droplet size measurements. The penetration data were successfully correlated using groupings of the variables and parameters suggested by a simple analysis.

A Study of the Adsorption of Ni(II) and Cu(II) by Clay Minerals

Abstract: The adsorption of Ni(II) and Cu(II) on to the clay minerMs kaolinite, chlorite, and illite has been investigated. The quantity of Ni(II) at pH 6 and Cu(II) at pH 5 adsorbed has been found to vary in the manner chlorite > illite > kaolinite. Examination of the mode of bonding of the metal ions to the clay minerals using X-ray photoelectron spectroscopy (XPS) has been carried out. Compari- son of the binding energies for metal ions in octahedral sites in selected minerals (reference minerals) and in simple nickel and copper containing compounds with values for Ni(II) and Cu(II) adsorbed on chlorite indicate that nickel(II) is probably bound as the aquo ion while copper(II) may be adsorbed as Cu(OH) §

The expanding public sector: Wagner squared

Abstract: Government spending, as a share of total spending, has increased substantially in all democracies in the period since World War II. The common-sense inference from this record is that the real size of government has grown. Morris Beck (1976) has demonstrated that this inference is invalid. Because the "price of government services rose substantially more than the price index of total output" (p. 18), the real size of the public sector actually declined in a majority of Western democracies, and the increase was decidedly modest in others. For the United States, to take a single case, Beck's data show that the real size of the public sector grew from 20 percent of GDP in 1950 to 24 percent in 1970, a considerably smaller growth than would be indicated by the 31 percent share of public spending in GDP. From these results Beck optimistically infers that "in real terms, the era of public-sector growth in most developed economies may have ended" (p. 15). Our reading of the agreed-on data is different. We infer from the record that the growth of the public sector may have, indeed, changed its form, but that predictions of long-term developments must be viewed with considerable foreboding. The data may suggest that the public sector is "out of control" in the literal sense of this term.

Molecular orbital studies of geometries and spectra of minerals and inorganic compounds

Abstract: Extended Huckel molecular orbital theory (EHT) and simple, approximate Self-Consistent-Field MO methods are employed to explain the geometries of nontransition metal bearing minerals and inorganic compounds. The spectra of such minerals and the electronic structure of transition metal oxidic minerals are explained using the Self-Consistent-Field X α MO method.

Turbulent boundary layer with injection and surface roughness

Abstract: Experimental studies were conducted to measure directly the skin friction on an axisymmetric body with and without injection through the surface in a turbulent, low-speed flow. Measurements also were taken of velocity profiles and the axial turbulence intensity throughout the boundary layer. The axisymmetric model, with interchangeable solid, smooth and porous, slightly rough walls, was tested at ReL from 4.96 to 6.11xl0 6. Particular attention was paid to the law-of-the-wall region of the boundary layer. For both the law-of-the-wall and axial turbulent intensities, good correlation between the present experiment and previous experiment and theory was shown for the solid-wall data. Porous-wall tests with no injection showed an increase in the local skin friction and an attendant shift in the log region of the law-of-the-wall because of the slight roughness of the permeable-wall over the solid-wall values. For cases with blowing through the permeable wall, direct measurements of the skin friction showed a decrease over the unblown cases with the permeable wall. However, substantial blowing was required to reduce the skin friction below that obtained on the solid, smooth wall at the same conditions. The logarithmic region of the law-of-the-wall with blowing was found to be independent of the blowing rate over the range tested when compared to the porous, unblown wall results. These experimental data were used to construct extensions of both the Van Driest and Reichardt transport models. The Reichardt model proved more useful, and excellent results were achieved. A,A',B A +

Mirror-image response during the first two years of life.

Abstract: Children aged 1-24 months viewed themselves in planar or distorted mirrors that were either clear or partially occluded. Analysis of videotaped records revealed that interest in viewing one's face did not vary with age among the 1- to 24-month-old subjects. All performed the simple behaviors of observing themselves although the older ones performed more complex (related) behaviors. Neither the flat nor the distorted mirror exposure was preferred suggesting that the infant observes the general configuration of the face for its intrinsic interest. Specific developmental trends were noted in the kind and amount of activity during the 1st 2 years of life culminating in a sequence of behaviors that suggested self-recognition.

An empirical test of lord's theoretical results regarding formula scoring of multiple-choice tests

Abstract: In a recent article, Lord (1975) demonstrated that the conventional correction-forguessing formula2 is superior to number-right scoring as an estimator of true examinee performance on multiple-choice tests, when examinees respond according to specified rules. The explicit assumption made by Lord is that, when appropriate instructions are provided, the only difference between an answer sheet obtained under formula-scoring directions and the same answer sheet obtained under number-right scoring directions would be that omitted responses (if any) on the former answer sheet are replaced by random guesses on the latter. While this assumption is far more tenable than the usual assumption associated with formula scoring,-that examinees either know the answer and mark it, or guess randomly among all item choices-it does not avoid the possibility that the admonition against wild guessing may cause examinees in general, or examinees with certain personality characteristics, to refrain from providing answers to questions which they have better than a chance probability of marking correctly. This possibility has been suggested by several investigators (Votaw, 1936; Sheriffs and Boomer, 1954; Slakter, 1968b). However, Lord noted that in each of these studies, the reported directions to examinees were inappropriate for an adequate test of his assumption. In addition, he faulted the study by Slakter (1968a) because the examinees had an opportunity to discuss or look up answers to questions omitted under formula-scoring directions. Both of these limitations are avoided in the present study. Another factor that may result in differential compliance with formula-scoring directions is that some examinees may correctly judge that their expected score will not be adequate in a competitive examination, and may therefore choose to answer all or nearly all questions in the hope that luck, in the short run, will be on their side. To the extent that such examinees are present, Lord's assumption would be less tenable. Since there are at least two a priori reasons to suspect that certain students either cannot or will not comply with directions appropriate for formula scoring, this study was designed to test the validity of Lord's assumption in a typical test-taking situation.

Area automatic generation control by multi-pass dynamic programming

Abstract: Current research in Automatic Generation Control emphasizes coordination of the regulation and the economic dispatch functions into a single systems problem. A dynamic optimal control problem formulation has previously been suggested. In this paper optimal trajectories are found for up to five maneuverable generators, using a new multi-pass dynamic programming method to make such solutions feasible. Dynamic valve point loading and singular solutions are considered. Computer studies have applied the method to several examples, including sudden changes in area load, and supplying the morning rise in area load.

Scalloped and Planar Erosion Surfaces, Middle Ordovician Limestones, Virginia: Analogues of Holocene Exposed Karst or Tidal Rock Platforms

Abstract: Scalloped and planar erosion surfaces are developed at numerous stratigraphic levels above prograded tidal flat fenestral limestones and beneath more open marine skeletal limestones in the Middle Ordovician limestone sequence, Virginia. Scalloped surfaces consist of smooth curved basins (10 cm to over 1 m wide) with intervening steep, locally overhanging walls and sharp ridges. Relief is up to 30 cm. The scalloped surfaces pass laterally into planar erosional contacts. Erosional surfaces truncate grains and cements and rare incipiently brecciated (vadose) fabrics. Fossiliferous breccias occur rarely above contacts. Some contacts are bored locally and encrusted by calcareous algae and bryozoans. Erosional contacts between fenestral limestones and overlying skeletal beds are extremely s arp and there is no burrowing across the contacts. Locally, submarine hardgrounds converge onto scalloped/planar erosional contacts. The erosion surfaces are believed to have formed initially as exposed karst on supratidal, prograded, early lithified tidal flat limestones, as indicated by vadose features beneath some contacts. Further erosion in tidal rock platform environments is indicated by position of erosion surfaces beneath open marine carbonates, organic encrustation of contacts, local marine cements beneath some contacts, local bored contacts, and by reported higher rates of tidal erosion compared to subaerial erosion in the Recent. These surfaces do not appear to have been documented to any extent in ancient carbonate sequences. However, the abundance of such surfaces along modern coasts and in karst terrains, and in the Middle Ordovician limestones of Virginia, suggests that they might be more abundant elsewhere. Finally, these surfaces might be useful in defining paleoshorelines in the absence of tidal flat deposits.

Bacteriocin Production by Strains of Bacteroides Isolated from Human Feces and the Role of These Strains in the Bacterial Ecology of the Colon

Abstract: Several human fecal isolates of Bacteroides have been found to produce bacteriocins. The bacteriocin-producing strain T1-1 was studied in the most detail. Strain T1-1 belongs to the 0061-1 deoxyribonucleic acid (DNA) homology group of Bacteroides. This homology group phenotypically resembles Bacteroides thetaiotaomicron but has little DNA homology with it. The bacteriocin-producing strains T1-12 and T1-48 belong to the 3452-A DNA homology group. This group has DNA homology with B. thetaiotaomicron and Bacteroides ovatus. The bacteriocin-producing strain T1-42 remains unidentified in that it does not belong to any recognized DNA homology group of the saccharolytic intestinal bacteroides. The extracellular bacteriocin produced by strain T1-1 was specifically bactericidal for other bacteria within the genus Bacteroides. The highest bacteriocin titers (32 to 64) were produced in complex media, with only trace amounts being produced in a defined medium. The bacteriocin appeared to have a high molecular weight (>/=300,000) and was unusual because it was stable from pH 1 to 12 and only a 50% reduction in activity resulted after 15 min at 121 degrees C in an autoclave. It was inactivated by trypsin and Pronase. Strain T1-1 was isolated from all three fecal samples obtained over a 25-week period from an individual who was part of a National Aeronautics and Space Administration mock Skylab flight. Strains T1-12, T1-48, and T1-42 were isolated only from the first fecal sample. Each of these strains was immune to the bacteriocins produced by the others. These strains were found to coexist in the colon with a larger population of non-bacteriocin-producing, bacteriocin-susceptible strains of Bacteroides.