Growth of SiO2 at room temperature with the use of catalyzed sequential half-reactions

Films of silicon dioxide (SiO2) were deposited at room temperature by means of catalyzed binary reaction sequence chemistry. The binary reaction SiCl4 + 2H2O --> SiO2 + 4HCl was separated into SiCl4 and H2O half-reactions, and the half-reactions were then performed in an ABAB ellipsis sequence and catalyzed with pyridine. The pyridine catalyst lowered the deposition temperature from >600 to 300 kelvin and reduced the reactant flux required for complete reactions from approximately 10(9) to approximately 10(4) Langmuirs. Growth rates of approximately 2.1 angstroms per AB reaction cycle were obtained at room temperature for reactant pressures of 15 millitorr and 60-second exposure times with 200 millitorr of pyridine. This catalytic technique may be general and should facilitate the chemical vapor deposition of other oxide and nitride materials.     

Quantitative morphological signatures define local signaling networks regulating cell morphology

Although classical genetic and biochemical approaches have identified hundreds of proteins that function in the dynamic remodeling of cell shape in response to upstream signals, there is currently little systems-level understanding of the organization and composition of signaling networks that regulate cell morphology. We have developed quantitative morphological profiling methods to systematically investigate the role of individual genes in the regulation of cell morphology in a fast, robust, and cost-efficient manner. We analyzed a compendium of quantitative morphological signatures and described the existence of local signaling networks that act to regulate cell protrusion, adhesion, and tension.     

Multi-party responses to environmental problems. A case of contaminated dairy cattle

This paper presents a framework for exploring the temporal and behavioral aspects of the responses of various involved parties that may lead to governmental intervention in situations involving exposure of the public to hazardous substances. The activities of key individuals are closely scrutinized. Relevance of the framework to agricultural and food concerns is also indicated. The exemplary case is the contamination of livestock in Michigan that began in 1973, but other cases are discussed that conform closely to the pattern described by the framework.George Morren is Associate Professor of Anthropology and Ecology in the Department of Human Ecology at Cook College, Rutgers, the State University of New Jersey, where he coordinates the International Environmental Studies Program. His areas of interest include tropical human ecology and social responses to hazards. He has done field research in Papua, New Guinea, northern Europe, and the U. S. and is currently studying public participation in environmental affairs in New Jersey and long term forest change in Papua, New Guinea. He is co-author (with Kathleen Wilson) ofSystems Approaches for Improvement in Agriculture and Resource Management, MacMillan, 1990.     

Spatial regulation of an E3 ubiquitin ligase directs selective synapse elimination

Stereotyped synaptic connectivity can arise both by precise recognition between appropriate partners during synaptogenesis and by selective synapse elimination. The molecular mechanisms that underlie selective synapse removal are largely unknown. We found that stereotyped developmental elimination of synapses in the Caenorhabditis elegans hermaphrodite-specific motor neuron (HSNL) was mediated by an E3 ubiquitin ligase, a Skp1-cullin-F-box (SCF) complex composed of SKR-1 and the F-box protein SEL-10. SYG-1, a synaptic adhesion molecule, bound to SKR-1 and inhibited assembly of the SCF complex, thereby protecting nearby synapses. Thus, subcellular regulation of ubiquitin-mediated protein degradation contributes to precise synaptic connectivity through selective synapse elimination.     

Sustainability and the moral community

Three views of sustainability are juxtaposed with four views about who the members of the moral community are. These provide points of contact for understanding the moral issues in sustainability. Attention is drawn to the preferred epistemic methods of the differing factions arguing for sustainability. Criteria for defining membership in the moral community are explored; rationality and capacity for pain are rejected as consistent criteria. The criterion of having interests is shown to be most coherent for explaining why all living humans belong to the moral community. This criterion allows inclusion of future generations as well, and extends to animals and plants membership in the moral community. Inferences are drawn that food sufficiency advocates hold only presently living persons to be full-fledged members of the moral community, but that this view is internally inconsistent. Stewards should agree that all living things are members of the moral community. A distinction between welfare interests and ulterior interests allows the steward to include the aims of those who argue for sustainability as community without committing some of their errors. Community advocates argue that essential values and virtues will be lost is the culture of agriculture is transformed. I argue that community advocates may fail to pass on our most important virtue — justice — without such a transformation.     

Small phytoplankton and carbon export from the surface ocean

Autotrophic picoplankton dominate primary production over large oceanic regions but are believed to contribute relatively little to carbon export from surface layers. Using analyses of data from the equatorial Pacific Ocean and Arabian Sea, we show that the relative direct and indirect contribution of picoplankton to export is proportional to their total net primary production, despite their small size. We suggest that all primary producers, not just the large cells, can contribute to export from the surface layer of the ocean at rates proportional to their production rates.