A Web‐based and Group Learning Environment for Introductory Environmental Engineering

The use of computer‐based technology is becoming more prevalent in the classroom. As a part of an educational research project sponsored by the GE Foundation, strategies for augmenting a course, Introduction to Environmental Engineering (CE 280), were investigated including cross‐disciplinary experiences in teamwork, design, and the use of advanced teaching technologies such as the web. Interactive tools to assist student learning were developed and refined. Efforts have focused on developing an extensive website, web‐based quizzes and homework assignments, and tutorials. Base groups were used to provide both intellectual and emotional support to students. This paper summarizes the development of this course and the impact of rapid feedback on the progression of student understanding.     

On the influence of N on residual microstrain in cryomilled Ni

The factors that influence the development of residual microstrain during milling in a liquid nitrogen atmosphere, defined hereafter as cryomilling, are investigated. The residual microstrains in cryomilled Ni, processed under various cryomilling conditions, were examined by X-ray diffraction (XRD) and analyzed through the single line approximation (SLA) method. The average residual microstrains are determined to be in the range of 2×10⁻³ to 6×10⁻³. The residual microstrain on the (200) plane is higher than those on the other planes by 33 pct. The residual microstrain and its anisotropy in Ni are reduced after heat treatment at 800 °C for 1 hour. The measured microstrain is proposed to evolve from the presence of N and O as impurity atoms in the Ni lattice. Both N and O are introduced from the environment and then their solubility in Ni is enriched via the generation of defects that occurs during cryomilling. The stable site for N and O atoms in Ni is the octahedral site, and the sizes of N and O atoms exceed those of the octahedral site of Ni by 48 and 16 pct respectively. Accordingly, a lattice strain field is expected around interstitial N atoms that are located at octahedral sites. By comparing the crystal structure around the octahedral site, the stable site for impurity N atoms, in the Ni lattice with that of Ni₃N structure, the lattice strains are estimated to be in the range of 5 to 15 pct. The result shows that the (200) plane has strains that are 2 times higher than those in other planes, and this is argued to be the reason for the measured anisotropy of residual strain in Ni after cryomilling.     

Glass fiber-filled thermoplastics. I. Wall and processing effects on rheological properties

A systematic study of wall effects on the shear viscosity of short glass fiber-filled polypropylene and polystyrene is presented. The dependence of these effects on capillary radius, shear rate, temperature, and polymer matrix is examined. The “true” viscosity curves of these materials (free from wall effects) can be obtained by an extrapolation procedure. Breakage of glass fibers in the high shear-rate processes of extrusion and injection molding lead to an appreciable reduction of the viscosity of these materials and is probably the more important effect to take into account in these processes.     

Correction factors for water-proofing sleeves in kilovoltage x-ray beams

This paper investigates the effect of the waterproofing sleeve on the calibration of kilovoltage photon beams (50-300 kV). The sleeve effect correction factor, ps has been calculated using the Monte Carlo method as the ratios of the air kerma in an air cavity of a cylindrical chamber without the waterproofing sleeve to that with a sleeve. Three sleeve materials have been studied, PMMA, nylon and polystyrene. The calculations were carried out using the EGS4 (Electron Gamma Shower version 4) code system with the application of a correlated-sampling variance-reduction technique. The results show that the sleeve correction factor for 1-mm thick nylon and polystyrene sleeves, ps varies from 0.992 to 1.000 and from 0.981 to 1.000, respectively, for the same beam quality range. The ps factor varies with sleeve thickness, beam quality and phantom depth. No significant dependence of the ps factor on field size and source-surface distance has been found. Measurements for PMMA, nylon and polystyrene sleeves of various thicknesses have also been carried out and show excellent agreement with Monte Carlo calculations.     

The murine Tcl1 oncogene: embryonic and lymphoid cell expression

In human leukemias and lymphomas nonrandom chromosomal rearrangements cause changes in cell growth and/or survival in such a way as to promote malignancy. The detailed study of the biochemical and genetic pathways altered in human cancer requires the identification or development of models to allow the study and manipulation of cancer gene function. Recently, the breakpoint gene TCL1, involved in chromosome translocations observed mostly in mature T-cell proliferations and chronic lymphocytic leukemias (CLL), was isolated and characterized, and showed to be part of a new gene family of proteins involved in these tumors. The murine Tcl1 gene, is similar in sequence to the murine and human MTCP1 gene also involved in T cell leukemias. The murine Tcl1 gene was shown to reside on mouse chromosome 12 in a region syntenic to human chromosome 14. Furthermore, we show that the murine Tcl1 gene is expressed early in mouse embryonic development and demonstrates expression in fetal hematopoietic organs as well as in immature T and B cells. Characterization of the murine Tcl1 gene will help in developing a mouse model of CLL and would provide the best opportunity to study and decipher the role of TCL1 in malignant transformation.     

Proton-exchange optical waveguides in Z-cut LiNbO/sub 3/ using toluic acid

Proton-exchanged planar waveguides were demonstrated in Z-cut LiNBO/sub 3/ using toluic acid as a new organic proton source. These waveguides exhibit a propagation loss of around 1 dB/cm, and a step refractive index profile with an index increase of 0.124 measured at 0.663 mu m. The diffusion rate was found to be lower than those obtained using the popular benzoic and phosphoric acids.<>     

An interactive graphics system for real-time investigation and multivariate data portrayal for complex pedigree data systems

GRIFFIN (graphics investigation of familial information), an interactive graphics system for exploratory investigation of data on individuals associated by familial relationships, was designed to provide genetic epidemiologists a flexible, rapidly responsive tool for viewing and guiding exploration of complex databases in the context of familiar pedigree structures. It graphically portrays both categorical and multivariate scalar data on individuals in those structures. The display can be inverted to show all ancestors and descendants of any individual the user designates. It provides cues to censored information when bushy pedigrees cannot be fully displayed without sacrificing legibility. These guide users on where to next invert the system. Investigators may translate/zoom the display, vary the mode of representing data, point to individuals to obtain displays of alphameric information about them, etc. Developed in Fortran using IBM's GDDM graphics subroutines for an IBM 3090 mainframe, GRIFFIN's design anticipates porting to smaller systems.     

Enhancement of oxide break-up by implantation of fluorine inpoly-Si emitter contacted p+-n shallow junctionformation

In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p⁺-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF₂-implanted device is much larger than that of the boron-implanted device