The greening of materials science and engineering

The field of materials science and engineering is advancing at a revolutionary pace. It is now generally recognized as being among the key emerging technological fields propelling our world societies into the twenty-first century. The driving forces for this revolutionary pace are at once social, economic, political, and technological. For example, relatively recent changes in United States federal policies in environmental control, hazardous waste management, and energy conservation along with heightened international trade competition have resulted in major changes in material processing and use patterns. These changing patterns are creating new requirements for material developments, substitutions, and associated processes. This paper traces the emergence of materials policy and technological developments through four sub-periods of history: the birth and development of engineering in the United States (1825–1900), the evolution of a national research infrastructure (1900–1945), the evolution of a national science policy (1945–1973), and the intensification of global interdependency (1973-present). Future trends in materials developments and future policy requirements are outlined. Technical Resources, of TRW, Inc., began his professional career in 1954 as a research metallurgist and reactor project engineer with General Electric Co. at the Hanford Atomic Products Operation in Richland, WA. In 1965 he joined Battelle Memorial Institute as a manager of the metallurgy research department and three years later became manager of the fuels and materials department. In 1970 Dr. Bement joined the faculty of Massachusetts Institute of Technology as professor of nuclear materials. From 1974 to 1976 he served as a member of the U.S.-U.S.S.R. Bilateral Exchange Program in Magnetohydrodynamics and was the organizer and principal investigator of the M.I.T. Fusion Technology Program. In 1976 Dr. Bement became Director of the Materials Sciences Office of the Defense Advanced Research Projects Agency and in 1979 was appointed Deputy Under-Secretary of Defense for Research and Engineering. Dr. Bement has co-authored one book, edited three books, and authored over 90 articles on materials science, energy, and defense technology. He is a Fellow of the American Nuclear Society, the American Society for Metals, and the American Institute of Chemists. In addition, he is a member of the American Institute for Mining, Metallurgical and Petroleum Engineers, and the American Society for Testing and Materials. He has received outstanding achievement awards from the Colorado Engineering Council in 1954, the Defense Advanced Research Projects Agency in 1977, and the Colorado School of Mines in 1984. In 1980 he was awarded the Distinguished Civilian Service Medal by the Secretary of Defense. He is a member of the National Academy of Engineering. Dr. Bement is chairman of the National Materials Advisory Board and a member of the Board of Army Science and Technology, the Board on Engineering Sciences, the Board on Assessment of National Bureau of Standards Programs, and the Board on Science and Technology for International Development of the National Research Council. Dr. Bement received an Engineer of Metallurgy (E. Met.) degree in 1954 from the Colorado School of Mines. He received an M.S. in Metallurgical Engineering from the University of Idaho in 1959, and a Ph.D. from the University of Michigan in 1963. He is a Lt. Colonel (ret.) in the U.S. Army Corps of Engineers. Dr. Bement and his family reside in Mayfield Village, OH.     

The effect of a zirconium strength differential on cladding collapse predictions

An investigation was made into the occurrence of a strength differential in the Zircaloy cladding of LWR fuels, and into the effect such a strength differential can have on the analytical predictions of cladding creep collapse during fuel densification. The strength differential, or SD, refers to the difference in the compressive and tensile yield strengths of a material. It was concluded that an SD in Zircaloy cladding can have a significant effect on cladding collapse predictions; inclusion of SD considerations in cladding creep down analysis can increase predicted collapse times by a factor of two.     

Role of the cytoskeleton during early development.

Oocytes, eggs, and embryos from a diverse array of species have evolved cytoskeletal specializations which allow them to meet the needs of early embryogenesis. While each species studied possesses one or more specializations which are unique, several cytoskeletal features are widely conserved across different animal phyla. These features include highly-developed cortical cytoskeletal domains associated with developmental information, microtubule-mediated pronuclear transport, and rapid intracellular signal-regulated control of cytoskeletal organization.     

Transformation of the amphibian oocyte into the egg: Structural and biochemical events

Amphibian oocytes, arrested in prophase I, are stimulated to progress to metaphase II by progesterone. This process is referred to as meiotic maturation and transforms the oocyte, which cannot support the early events of embryogenesis, into the egg, which can. Meiotic maturation entails global reorganization of cell ultrastructure: In the cell cortex, the plasma membrane flattens and the cortical granules undergo redistribution. In the cell periphery, the annulate lamellae disassemble and the mitochondria become dispersed. In the cell interior, the germinal vesicle becomes disassembled and the meiotic spindles form. Marked changes in the cytoskeleton and mRNA distribution also occur throughout the cell. All of these events are temporally correlated with intracellular signalling events: Fluctuations in cAMP levels, changes in pH, phosphorylation and dephosphorylation, and ion flux changes. Evidence suggests that specific intracellular signals are responsible for specific reorganizations of ultrastructure and mRNA distribution.     

Molecular cloning and immunologic reactivity of a novel low molecular mass antigen of Mycobacterium tuberculosis

Polypeptide Ags present in the culture filtrate of Mycobacterium tuberculosis were purified and evaluated for their ability to stimulate PBMC from purified protein derivative (PPD)-positive healthy donors. One such Ag, which elicited strong proliferation and IFN-gamma production, was further characterized. The N-terminal amino acid sequence of this polypeptide was determined and used to design oligonucleotides for screening a recombinant M. tuberculosis genomic DNA library. The gene (Mtb 8.4) corresponding to the identified polypeptide was cloned, sequenced, and expressed in Escherichia coli. The predicted m.w. of the recombinant protein without its signal peptide was 8.4 kDa. By Southern analysis, the DNA encoding this mycobacterial protein was found in the M. tuberculosis substrains H37Rv, H37Ra, Erdman, and "C" strain, as well as in certain other mycobacterial species, including Mycobacterium avium and Mycobacterium bovis BCG (bacillus Calmette-Guerin, Pasteur). The Mtb 8.4 gene appears to be absent from the environmental mycobacterial species examined thus far, including Mycobacterium smegmatis, Mycobacterium gordonae, Mycobacterium chelonae, Mycobacterium fortuitum, and Mycobacterium scrofulaceum. Recombinant Mtb 8.4 Ag induced significant proliferation as well as production of IFN-gamma, IL-10, and TNF-alpha, but not IL-5, from human PBMC isolated from PPD-positive healthy donors. Mtb 8.4 did not stimulate PBMC from PPD-negative donors. Furthermore, immunogenicity studies in mice indicate that Mtb 8.4 elicits a Th1 cytokine profile, which is considered important for protective immunity to tuberculosis. Collectively, these results demonstrate that Mtb 8.4 is an immunodominant T cell Ag of M. tuberculosis.     

Human purified protein derivative-specific CD4+ T cells use both CD95-dependent and CD95-independent cytolytic mechanisms

CTL, both CD4+ and CD8+, are essential in the eradication of intracellular pathogens. Data generated using murine T cells have suggested a critical role for CD95 (Fas, Apo-1) in CD4+ T cell-induced apoptosis of target cells. In contrast, CD8+ CTL predominantly use the perforin/granzyme lytic pathway. At present little is known about the mechanism of CD4+ CTL lytic function during intracellular infection in humans. We have used human CD4+ T cells specific for purified protein derivative (PPD) of Mycobacterium tuberculosis to explore whether CD95 is the dominant cytolytic mechanism. PPD-reactive CD4+ clones efficiently lysed Ag-pulsed autologous monocytes, adherent macrophages, and EBV-transformed B cells. Addition of an antagonistic CD95 Ab had a minimal effect on cytolysis, whereas addition of MgEGTA to block perforin/granzyme resulted in complete inhibition of killing. In contrast, lysis of activated peripheral blood B cells could be partially blocked with the antagonistic CD95 Ab. Supporting these observations, monocytes, macrophages, and EBV-transformed B cells were not lysed by an agonistic CD95 Ab. Activated B cells were readily lysed by the agonistic CD95 Ab. T cell clones triggered through the TCR with anti-CD3 were capable of lysing the CD95-sensitive Jurkat T cell line in a CD95-dependent manner, but were also able to release granzymes. We conclude that human CD4+ T cells are capable of lysing PPD-pulsed targets using both perforin/granzyme and CD95 pathways. The contribution of CD95 is strictly dependent on target cell susceptibility to CD95-mediated killing.     

Simulation of irradiation-induced creep in nickel

An experimental technique has been developed to simulate neutron irradiation-induced creep by charged particle bombardment. The experimental apparatus permits on-line computer monitoring of experimental parameters while temperature, stress, and flux are maintained at the desired levels. A typical result obtained with a 0.38 mm (0.015 in.) thick, high-purity nickel specimen bombarded with 22 MeV deuterons at 224°C (435°F) and at a stress of 345 MPa (50.12 ksi) is presented. The result demonstrates that charged particle irradiation can successfully be used to simulate irradiation-induced creep reproducibly in materials whose thickness is typical of nuclear fuel cladding.     

Temperature dependence of the zircaloy-4 strength-differential

An investigation was undertaken to determine the behavior of the strength-differential in the three principal directions of α-rolled, Zircaloy-4 plate as a function of temperature. The method of using Knoop hardness numbers to generate yield loci was employed in determining the magnitude of the strength-differential. It was found that the magnitude of the strength-differential was proportional to the concentration of basal poles along the direction of consideration and that it decreased in magnitude with increasing temperature. However, it remained of significant magnitude (≈85 MPa) in both the transverse and normal directions at light water reactor operating temperatures. Use of the elevated temperature, strength-differential data in clad creep down analyses demonstrated that the consideration of the strength-differential in clad creep analysis can increase predicted collapse times by a factor greater than two in pressurized water reactor fuel pins. It was also found that the strength-differential effect on such predictions is sensitive to clad texture.     

The greening of materials science and engineering

The field of materials science and engineering is advancing at a revolutionary pace. It is now generally recognized as being among the key emerging technological fields propelling our world societies into the twenty-first century. The driving forces for this revolutionary pace are at once social, economic, political, and technological. For example, relatively recent changes in United States federal policies in environmental control, hazardous waste management, and energy conservation along with heightened international trade competition have resulted in major changes in material processing and use patterns. These changing patterns are creating new requirements for material developments, substitutions, and associated processes. This paper traces the emergence of materials policy and technological developments through four sub-periods of history: the birth and development of engineering in the United States (1825–1900), the evolution of a national research infrastructure (1900–1945), the evolution of a national science policy (1945–1973), and the intensification of global interdependency (1973-present). Future trends in materials developments and future policy requirements are outlined.