The new programming discipline

Recently there has been substantial interest in promoting ‘Structured Programming’ as a means of writing more nearly error free programs. However since the chief advocates of structured programming use ALGOL or PASCAL, and disdain FORTRAN, there is a difficulty in communication. Since it is my perception that structured programming and the lessons to be learned from proofs of correctness can be applied in any language, including FORTRAN, I feel that these ideas should be promulgated to applied scientific programmers. Hence this paper will commence with a summary of the whole complex of ideas and practices that are subsumed under the term ‘Structured Programming’. Then some simple examples of top down design and programming will be given. Finally I will return to a discussion of some of the problems which are likely to be encountered in the use and promulgation of structured programming.     

Cerebrospinal fluid lipoproteins are more vulnerable to oxidation in Alzheimer’s disease and are neurotoxic when oxidized ex vivo

Brain regional oxidative damage is thought to be a central mechanism in the pathogenesis of Alzheimer’s disease (AD). Recent studies of cerebrospinal fluid (CSF) have suggested that increased lipid peroxidation of CSF and CSF lipoproteins also may occur in AD patients. In the present study, we determined the susceptibility of human CSF to ex vivo lipid peroxidation and tested the hypothesis that oxidized CSF lipoproteins may be neurotoxic. Whole CSF or a CSF lipoprotein fraction (d<1.210 g/mL) was oxidized with 2,2′-azobis(2-amidino-propane)dihydrochloride (AAPH), a hydrophilic free-radical generator. Kinetics of CSF lipid peroxidation were followed by a standard fluorescence product accumulation assay. Oxidation of AD CSF yielded significantly shorter fluorescent lag times than controls, indicating reduced antioxidant capacity. Electrophoretic mobilities of CSF apolipoproteins were specifically reduced upon oxidation of CSF with AAPH, suggesting that lipoproteins are primary targets of CSF lipid peroxidation. Cultured neuronal cells were exposed to physiological concentrations of isolated CSF lipoproteins oxidized with increasing concentrations of AAPH; the resulting neurotoxicity showed a significant linear AAPH concentration-response relationship. These results suggest that oxidized CSF lipoproteins may contribute to the pathogenesis of neurodegeneration in AD.     

Gossypol and gossypurpurin in cottonseed of different varieties ofG. barbadense andG. hirsutum,and variation of the pigments during storage of the seed

Summary Selected varieties of cottonseed comprising three Sea Island cottons, four Egyptian cottons, and 10 upland cottons providing two or more varieties having the following characteristics: short, intermediate, and long staple; low, intermediate, and high content of lipids; and low, intermediate, and high content of protein, were planted and grown under as nearly identical conditions as possible. The initial contents of moisture, lipids, nitrogen, gossypol, and gossypurpurin of the harvested seed were determined, after which samples of all of the seed were stored for a year under identical conditions and analyzed periodically for gossypol and gossypurpurin. A definite relation was found between the species of the seed and their content of gossypol and gossypurpurin. Sea Island and Egyptian seed of the speciesG. barbadense contained more gossypol and very much more gossypurpurin than seed of the speciesG. hirsutum. Within the speciesG. barbadense Sea Island seed contained more gossypol and less gossypurpurin than Egyptian seed. Gossypurpurin increased during storage of all of the seed whereas gossypol varied in a number of different ways, increasing in some, decreasing in others, and remaining relatively constant in a few samples of stored seed. A discussion is presented of the theoretical and practical implications of these observations. Presented at 39th Annual Meeting of the American Oil Chemists' Society in New Orleans, May 4–6, 1948. One of the laboratories of the Burean of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture. Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration, U. S. Department of Agriculture.     

Evaluation of In-Service Performance of Tom’s Creek Bridge Fiber-Reinforced Polymer Superstructure

The Tom’s Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load-carrying members. The project is intended to serve two purposes. First, by calculating bridge design parameters such as the dynamic load allowance, transverse wheel load distribution, and deflections under service loading, the Tom’s Creek Bridge aids in modifying current American Association of State Highway and Transportation Officials bridge design standards for use with FRP composite materials. Second, by evaluating the FRP girders after exposure to service conditions, the project begins to answer questions about the long-term performance of these advanced composite material beams when used in bridge design. This paper details the in-service analysis of the Tom’s Creek Bridge. Five load tests, at 6-month intervals, were conducted on the bridge. Using midspan strain and deflection data gathered from the FRP composite girders during these tests, the aforementioned bridge design parameters have been determined. The Tom’s Creek Bridge was determined to have a maximum dynamic load allowance, IM, of 0.90, a transverse wheel load distribution factor, g, of 0.101, and a maximum deflection of L/490. Two bridge girders were removed from the Tom’s Creek Bridge after 15 months of service loading. These FRP composite girders were tested at the Structures and Materials Research Laboratory at Virginia Tech for stiffness and ultimate strength and compared to preservice values for the same beams. These measurements indicate that, after 15 months of service, the FRP composite girders have not significantly changed in stiffness or ultimate moment capacity.     

Assessment and Modification of Flexibility of Cognitive Structures Created in University Courses

Students' organization of the knowledge that they acquire is an important factor in determining the degree to which it is retained and used. In the past we have used the "fill-in-the-structure" (FITS) task as a direct method of inferring students' cognitive structures of course content (Naveh-Benjamin, Lin & McKeachie, 1995). This study goes one step further by using the FITS task to assess the flexibility of students' cognitive structures of the material learned; that is, whether students are able to relate the same concepts in different ways when the concepts are embedded in two different conceptual frameworks. We assessed the flexibility of students' cognitive structures in three studies by asking students in an ecology course to complete two different structures, each based on a different major dimension in the course. Results of the first study showed that the FITS technique could be used to assess students' ability to use concepts learned in the course appropriately in two different frameworks. The flexibility measures obtained were positively related to academic performance. The second study demonstrated the usefulness of the technique in measuring the development of conceptual flexibility during the course. Finally, the third study employed the technique to show that students' flexible use of concepts can be enhanced by appropriate instruction. Copyright 1998 Academic Press.     

Fairness and Optimal Stochastic Control for Heterogeneous Networks

We consider optimal control for general networks with both wireless and wireline components and time varying channels. A dynamic strategy is developed to support all traffic whenever possible, and to make optimally fair decisions about which data to serve when inputs exceed network capacity. The strategy is decoupled into separate algorithms for flow control, routing, and resource allocation, and allows each user to make decisions independent of the actions of others. The combined strategy is shown to yield data rates that are arbitrarily close to the optimal operating point achieved when all network controllers are coordinated and have perfect knowledge of future events. The cost of approaching this fair operating point is an end-to-end delay increase for data that is served by the network.     

Optimal excitation wavelengths for discrimination of cervical neoplasia

Fluorescence spectroscopy has shown promise for the in vivo, real-time detection of cervical neoplasia. However, selection of excitation wavelength has in the past been based on in vitro studies and the availability of light sources. The goal of this study was to determine optimal excitation wavelengths for in vivo detection of cervical neoplasia. Fluorescence excitation-emission matrices (EEMs) were measured in vivo from 351 sites in 146 patients. Data were analyzed in pairs of diagnostic classes to determine which combination of excitation wavelengths yields classification algorithms with the greatest sensitivity and specificity. We find that 330-340-, 350-380-, and 400-450-nm excitation yield the best performance. The sensitivity and specificity for discrimination of squamous normal tissue and high-grade squamous intraepithelial lesion (HGSIL) were 71% and 77% on cross validation using three excitation wavelengths. These results are comparable with those found in earlier in vivo studies; however, in this study we find that the proportion of samples which are HGSIL influences performance. Furthermore stratification of samples within low-grade squamous intraepithelial lesion and HGSIL also appears to influence diagnostic performance. Future diagnostic studies should be carried out at these excitation wavelengths in larger groups so that data can be stratified by diagnostic subcategory, age and menopausal status. Similarly, large studies should be done in screening populations.