Academic literature on the topic 'LD5655.V851 1993.H467'

Of the estimated 1100 species of mealybugs, approximately 6% are described as possessing degenerative legs and antennae in the adult female developmental stage or having lost these structures altogether. Fifteen genera composing 63 species are often separated into their own taxonomic group based on these vestigial features (e.g., Sphaerococcinae), and are collectively known as the "legless" mealybugs. A comparative morphological analysis of adult females was undertaken to clarify the taxonomic placement of these species and to determine their relationships. Methods were included on collecting, preserving, slide-mounting, and measuring specimens, and on preparing illustrations. Keys to genera and species of "legless" mealybugs were developed. Reduction or loss of legs and antennae apparently occurred convergently in response to similar environmental conditions and was not found supportive of homogeneity in the "legless" group as a whole. However, the genera Chaetococcus Maskell, Idiococcus Takahashi & Kanda, Kermicus Newstead, Serrolecanium Shinji, Tangicoccus Kozar & Walter, and a newly established genus share many characteristics and were treated as the tribe Serrolecaniini Shinji. The adult females of 13 species contained in these genera were redescribed, with illustrations produced for 12. A phylogenetic analysis of the tribe showed that converse to simplification in appendages, adaptations in other features (e.g., latero-projecting lobes and a caudally-directed vulva) probably developed to increase reproductive success and survivorship. The genera Acinococcus Williams, Antonina Signoret, Antoninoides Ferris, Cypericoccus Williams, Nesticoccus Tang, Paludicoccus Ferris, Parapaludicoccus Mamet, Peridiococcus Williams, Pseudantonina Green, and Sphaerococcus Maskell are not closely related to one another or to members of the tribe Serrolecaniini based on adult female morphology. These 10 genera and their type species were redescribed, and illustrations produced for all but Nesticoccus sinensis Tang. Comments or redescriptions are provided for the 21 additional species that comprise these genera; however, the taxonomic placement of 18 additional species erroneously assigned to Pseudantonina and Sphaerococcus is uncertain. Lectotypes were designated for Antonina crawi Cockerell, A. graminis Parrott, A. phragmitis Marchal, A. purpurea Signoret, A. waterstoni Newstead, Jdiococcus bambusae Takahashi & Kanda, Pseudantonina bambusae Green, Pseudolecanium disticlium Kuwana, and Sphaerococcus ethelae Fuller. A replacement name was proposed for the junior homonym Antoninella Sulc. The species names Antonina anceps Green, Antonina maritima Green, and Jdiococcus maanshanensis Tang & Wu are considered junior synonyms. Two species of Serrolecanium were described, and a new genus was established for the placement of Serrolecanium jiuhuaensis Wu and Serrolecanium sasae (Siraiwa). Six new name combinations are also made.<br>Ph. D.

Supercritical fluid extraction (SFE) is becoming an attractive alternative to conventional solvent extraction for many reasons. These reasons include advantages of speed, the ability to be automated more easily than conventional solvent extractions and the lack of solvent disposal after the extraction has been performed. At this date SFE is performed in a multitude of ways with no one method out performing the others. The different ways in which SFE is performed is reviewed. Supercritical fluid extraction of analytes from aqueous solution has not received much attention. The design of a system which allows for the extraction of analytes from aqueous solution has been explored in this thesis. Several related areas (injection techniques for supercritical fluid chromatography and on-line SFE) were also developed. The injection port of a supercritical fluid chromatograph was modified to provide better ( more reproducible) sample introduction. For a 100 ppm 3,5-nitrobenzamide solution in methylene chloride the area reproducibility was increased from 3.2% RSD for the unmodified valve to 0.74% RSD for the modified valve. The method also resulted in a more narrow solvent front as well as an increase of 10% in the number of theoretical plates of the system. On-line SFE\SFC was explored as one possible configuration for the extraction of analytes from aqueous solution. Solvent elimination injection (SEI), was developed for SFC. The difference in vapor pressure between the analytes and solvent allowed for the solvent to evaporate and be transported form the system while the analytes were collected on various traps. After evaporation of the injection solvent the analytes were flushed onto a chromatographic column. SEI allowed for the reproducible injection of larger volumes of sample (solvent and analyte) into the system. SEI allowed for different hardware configurations to be tested without performing an actual supercritical fluid extraction. An off-line solid phase trapping system for SFE was developed. The system trapped the analytes from the SFE effluent onto a solid phase extraction cartridge. The cartridge could then be rinsed in a normal fashion to elute the analytes of interest. Trapping in this way was found to allow for faster extraction rates than liquid trapping. The efficiency of the trapping mechanism was found to be dependent upon the temperature of the trap, the chemical functionality of the phase bonded io the silica and the nature of the analytes. A system which allowed for the extraction of moderate volumes (3-5 mL) of aqueous solution was developed. A test solution of phenols was used to evaluate the system. The extractability of the phenols was found to be a function of pressure of the system and the chemical nature of the phenol. A decrease in extractability of the phenols was found to take place at pressures greater than 250 atm. The distribution coefficient of phenol was found to increase steadily through 400 atm. A decrease in surface area of the supercritica1 fluid passing through the aqueous solution was thought to be responsible for the apparent contradiction in behavior.<br>Ph. D.

Traditionally, in reliability design, the random variables acting on a system are assumed independent. This assumption is usually poor because in most real life problems the variables are correlated. The available information, most of the time, is limited to the first and second moments. Very few methods can handle correlation between the variables when the joint probability density function is unknown. There are no reports that provide information of the accuracy of these methods. This work presents an evaluative study of reliability under incomplete information, comparing three existing methods for calculating the probability of failure: The method presented by Ang and Tang which assumes the correlation between the variables to be invariant; Kiureghian and Liu/s method which accounts for the change in correlation and; Rackwitz's method under the assumption of independence. We have also developed a new algorithm to generate random samples of correlated random variables when the marginal distributions and correlation coefficients of these variables are specified. These samples can be used in IVlonte Carlo simulation which is a tool for comparison of the three methods described above. This Monte Carlo simulation approach is based on the assumption of normal joint probability density function as considered by Kiureghian and Liu. To examine if this approach is biased towards Kiureghian and Liu, a second Monte Carlo simulation approach with no assumption about the joint probability density function is developed and compared with the first one. Both methods that account for correlation show a clear advantage over the traditional approach of assuming that the variables are independent. Moreover, Kiureghian and Liu's approach proved to be more accurate in most cases than Ang and Tang's method. In this study, it is also shown that there is an error in calculating the safety index for correlated variables when either one of the methods in study is implemented, because the joint probability density function of the random variables is neglected.<br>Master of Science

The purpose of this study was two-fold: firstly, the MOCVD deposition behavior of Pb(thd)2 was studied in detail and a one-dimensional kinetic model was proposed to successfully predict the effect of processing conditions on the deposition rate profile for PbO. Assuming the surface reaction is the rate-limiting step in the process, the effective activation energy for the process, Ea, was found to be 82 kJ/mol while the preexponential rate constant was found to be 33 g/cm2/min (0.15 moVcm2/min). The process was found to consistently produce a combination of the high temperature, orthorhombic modification of lead monoxide with randomly oriented plates of tetragonal lead monoxide. TEM electron diffraction was used to investigate the crystal orientation of the individual plates which was found to be in the plane normal to the <201> zone. <p>Secondly, the deposition behavior of PbTi03 and the resulting film structure and properties were investigated. Pb(thd)2 was used in conjunction with titanium ethoxide (Ti(OEt)4) as a titanium source. Stoichiometric lead titanate films which were found to be smooth, specular and transparent, and well-adhered were deposited on a variety of substrates by careful control of the experimental conditions. Film structure, composition, and thickness were studied and correlated to changes in various experimental parameters. Additionally, a high temperature regime at which the film stoichiometry is relatively insensitive to experimental conditions was found to occur. The effects of post-annealing on the as-deposited films including compositional changes, morphological changes and crystal structure was also studied. Some problems were obtained with film peeling on the ruthenium oxide (Ru0₂)-coated substrates which could be alleviated somewhat by the use of (100) oriented silicon wafer rather than (111) oriented silicon; a possible mechanism to explain this behavior is also suggested. Optical properties were obtained using UV -VISNIR transmission and reflectance spectroscopy; the ferroelectric hysteresis behavior of the films was observed using standard R T -66 A test equipment.<br>Master of Science

This study examined a neglected area in long term care and adult day care research: staff development. The specific purposes of this study were to describe the provision of a comprehensive staff development program in adult day care centers in Virginia in order to (a) differentiate those centers providing only the minimum required inservice training from those centers providing more comprehensive staff development programs and (b) define what meaning is placed upon staff education programs by center administrators. <p>A mail survey design was used for this study. The questionnaire developed for the study has three sections: (a) center characteristics, (b) staff characteristics, and (c) the meaning of staff development. Quantitative analysis was conducted on the first two sections while qualitative analysis was used to examine the final section. A conceptual model for adult day care staff development programs was also developed for the study. The model was used to compare the staff development programs across adult day care centers in Virginia. The sample included all licensed adult day care center administrators in Virginia (n=43). The total response rate for this survey was 88%. <p>Results were discussed in terms of the provision of staff development programs, as well as the meaning that was placed on staff development by the responding center administrators. The results showed that much importance is placed upon staff development programs by the center administrators and they follow through with this by providing a well rounded staff development program for their staff.<br>Master of Science