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  • Nature Publishing Group  (3,707)
  • American Geophysical Union (AGU)
  • Annual Reviews
  • 2000-2004  (4,669)
  • 1980-1984
  • 1935-1939
  • 2003  (4,669)
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  • 2000-2004  (4,669)
  • 1980-1984
  • 1935-1939
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  • 1
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    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 47-67 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Optical single transporter recording (OSTR) is an emerging technique for the fluorescence microscopic measurement of transport kinetics in membrane patches. Membranes are attached to transparent microarrays of cylindrical test compartments (TCs) ~0.1-100 mum in diameter and ~10-100 mum in depth. Transport across membrane patches that may contain single transporters or transporter populations is recorded by confocal microscopy. By these means transport of proteins through single nuclear pore complexes has been recorded at rates of 〈1 translocation/s. In addition to the high sensitivity in terms of measurable transport rates OSTR features unprecedented spatial selectivity and parallel processing. This article reviews the conceptual basis of OSTR and its realization. Applications to nuclear transport are summarized. The further development of OSTR is discussed and its extension to a diversity of transporters, including translocases and ATP-binding cassette (ABC) pumps, projected.
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  • 2
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 93-114 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Since mid-1990, with cloning and identification of several families of natural killer (NK) receptors, research on NK cells began to receive appreciable attention. Determination of structures of NK cell surface receptors and their ligand complexes led to a fast growth in our understanding of the activation and ligand recognition by these receptors as well as their function in innate immunity. Functionally, NK cell surface receptors are divided into two groups, the inhibitory and the activating receptors. Structurally, they belong to either the immunoglobulin (Ig)-like receptor superfamily or the C-type lectin-like receptor (CTLR) superfamily. Their ligands are either members of class I major histocompatibility complexes (MHC) or homologs of class I MHC molecules. The inhibitory form of NK receptors provides the protective immunity through recognizing class I MHC molecules with self-peptides on healthy host cells. The activating, or the noninhibitory, NK receptors mediate the killing of tumor or virally infected cells through their specific ligand recognition. The structures of activating and inhibitory NK cell surface receptors and their complexes with the ligands determined to date, including killer immunoglobulin-like receptors (KIRs) and their complexes with HLA molecules, CD94, Ly49A, and its complex with H-2Dd, and NKG2D receptors and their complexes with class I MHC homologs, are reviewed here.
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  • 3
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 161-182 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Recent years have witnessed a renaissance of fluorescence microscopy techniques and applications, from live-animal multiphoton confocal microscopy to single-molecule fluorescence spectroscopy and imaging in living cells. These achievements have been made possible not so much because of improvements in microscope design, but rather because of development of new detectors, accessible continuous wave and pulsed laser sources, sophisticated multiparameter analysis on one hand, and the development of new probes and labeling chemistries on the other. This review tracks the lineage of ideas and the evolution of thinking that have led to the actual developments, and presents a comprehensive overview of the field, with emphasis put on our laboratory's interest in single-molecule microscopy and spectroscopy.
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  • 4
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 135-159 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The lamba integrase, or tyrosine-based family of site-specific recombinases, plays an important role in a variety of biological processes by inserting, excising, and inverting DNA segments. Flp, encoded by the yeast 2-mum plasmid, is the best-characterized eukaryotic member of this family and is responsible for maintaining the copy number of this plasmid. Over the past several years, structural and biochemical studies have shed light on the details of a common catalytic scheme utilized by these enzymes with interesting variations under different biological contexts. The emergence of new Flp structures and solution data provides insights not only into its unique mechanism of active site assembly and activity regulation but also into the specific contributions of certain protein residues to catalysis.
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  • 5
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 285-310 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The past decade has witnessed increasingly detailed insights into the structural mechanism of the bacteriorhodopsin photocycle. Concurrently, there has been much progress within our knowledge pertaining to the lipids of the purple membrane, including the discovery of new lipids and the overall effort to localize and identify each lipid within the purple membrane. Therefore, there is a need to classify this information to generalize the findings. We discuss the properties and roles of haloarchaeal lipids and present the structural data as individual case studies. Lipid-protein interactions are discussed in the context of structure-function relationships. A brief discussion of the possibility that bacteriorhodopsin functions as a light-driven inward hydroxide pump rather than an outward proton pump is also presented.
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  • 6
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 375-397 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract G protein-coupled receptors (GPCRs) are integral membrane proteins that respond to environmental signals and initiate signal transduction pathways activating cellular processes. Rhodopsin is a GPCR found in rod cells in retina where it functions as a photopigment. Its molecular structure is known from cryo-electron microscopic and X-ray crystallographic studies, and this has reshaped many structure/function questions important in vision science. In addition, this first GPCR structure has provided a structural template for studies of other GPCRs, including many known drug targets. After presenting an overview of the major structural elements of rhodopsin, recent literature covering the use of the rhodopsin structure in analyzing other GPCRs will be summarized. Use of the rhodopsin structural model to understand the structure and function of other GPCRs provides strong evidence validating the structural model.
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  • 7
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 399-424 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The coupling of high-performance mass spectrometry instrumentation with highly efficient chromatographic and electrophoretic separations has enabled rapid qualitative and quantitative analysis of thousands of proteins from minute samples of biological materials. Here, we review recent progress in the development and application of mass spectrometry-based techniques for the qualitative and quantitative analysis of global proteome samples derived from whole cells, tissues, or organisms. Techniques such as multidimensional peptide and protein separations coupled with mass spectrometry, accurate mass measurement of peptides from global proteome digests, and mass spectrometric characterization of intact proteins hold great promise for characterization of highly complex protein mixtures. Advances in chemical tagging and isotope labeling techniques have enabled quantitative analysis of proteomes, and highly specific isolation strategies have been developed aimed at selective analysis of posttranslationally modified proteins.
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  • 8
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    Annual Review of Materials Research 33 (2003), S. 557-579 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Combinatorial methods provide a means for accelerating the discovery of fuel cell catalysts. The first example of parallel fuel cell catalysts screening was an indirect method that used fluorescent chemosensors to detect changes in pH in proximity to electrocatalyst spots. Serial direct electrochemical methods have been developed that use voltammetry, chronoamperometry, and scanning electrochemical microscopy. An array fuel cell screens catalysts simultaneously, using high-performance fuel cell components. Heuristic models based on mechanistic and spectroscopic studies provide guidance for library development, and detailed studies of discovered catalysts can help to refine these models. The remaining challenges are the development of high throughput synthetic methods that can enable the use of discovery level and focus level screening. Until these synthetic methods are developed, a greater emphasis should be placed on smaller libraries with design of experiment strategies leveraged with informatics and data mining.
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  • 9
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    Annual Review of Materials Research 33 (2003), S. 503-555 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The past 10 years have witnessed a tremendous acceleration in research devoted to non-fluorinated polymer membranes, both as competitive alternatives to commercial perfluorosulfonic acid membranes operating in the same temperature range and with the objective of extending the range of operation of polymer fuel cells toward those more generally occupied by phosphoric acid fuel cells. Important requirements are adequate membrane mechanical strength at levels of functionalization (generally sulfonation) and hydration allowing high proton conductivity, and stability in the aggressive environment of a working fuel cell, in particular thermohydrolytic and chemical stability. This review provides an overview of progress made in the development of proton-conducting hydrocarbon and heterocyclic-based polymers for proton exchange and direct methanol fuel cells and describes the various approaches made to polymer modification/synthesis and salient properties of the materials formed, including those relating to proton transport and proton conductivity, e.g., water diffusion and electro-osmotic drag. The microstructure, deduced from small angle X-ray and neutron diffraction measurements of representative non-fluorinated polymers is compared with that of perfluorosulfonic acid membranes. Different degradation mechanisms and aging processes that can result in chemical and morphological alteration are considered, and recent characterization of membrane-electrode assemblies (MEAs) in direct methanol and hydrogen-air (oxygen) fuel cells completes this review of the state of the art. While several types of non-fluorinated polymer membrane have demonstrated lifetimes of 500-4000 h, only a limited number of systems exist that hold promise for long-term operation above 100oC.1
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  • 10
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    Annual Review of Fluid Mechanics 35 (2003), S. 1-10 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 11
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    Annual Review of Fluid Mechanics 35 (2003), S. 45-62 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Drag reduction in wall-bounded flows can be achieved by transverse motions imposed by passive means, e.g., riblets, or by external forcing, such as wall oscillation or transverse traveling-wave excitation. In this article, we review possible physical mechanisms responsible for turbulent drag reduction and corresponding near-wall flow modification.
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  • 12
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    Annual Review of Fluid Mechanics 35 (2003), S. 89-111 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.
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  • 13
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    Annual Review of Fluid Mechanics 35 (2003), S. 135-167 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The issue of the physical mechanism(s) that control the efficiency with which the density field in stably stratified fluid is mixed by turbulent processes has remained enigmatic. Similarly enigmatic has been an explanation of the numerical value of ~0.2, which is observed to characterize this efficiency experimentally. We review recent work on the turbulence transition in stratified parallel flows that demonstrates that this value is not only numerically predictable but also that it is expected to be a nonmonotonic function of the Richardson number that characterizes preturbulent stratification strength. This value of the mixing efficiency appears to be characteristic of the late-time behavior of the turbulent flow that develops after an initially laminar shear flow has undergone the transition to turbulence through an intermediate instability of Kelvin-Helmholtz type.
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  • 14
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    Annual Review of Fluid Mechanics 35 (2003), S. 373-412 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Recent small-scale turbulence observations allow the mixing regimes in lakes, reservoirs, and other enclosed basins to be categorized into the turbulent surface and bottom boundary layers as well as the comparably quiet interior. The surface layer consists of an energetic wave-affected thin zone at the very top and a law-of-the-wall layer right below, where the classical logarithmic-layer characteristic applies on average. Short-term current and dissipation profiles, however, deviate strongly from any steady state. In contrast, the quasi-steady bottom boundary layer behaves almost perfectly as a logarithmic layer, although periodic seiching modifies the structure in the details. The interior stratified turbulence is extremely weak, even though much of the mechanical energy is contained in baroclinic basin-scale seiching and Kelvin waves or inertial currents (large lakes). The transformation of large-scale motions to turbulence occurs mainly in the bottom boundary and not in the interior, where the local shear remains weak and the Richardson numbers are generally large.
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  • 15
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    Annual Review of Fluid Mechanics 35 (2003), S. 469-496 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Increasing urbanization and concern about sustainability and quality of life issues have produced considerable interest in flow and dispersion in urban areas. We address this subject at four scales: regional, city, neighborhood, and street. The flow is one over and through a complex array of structures. Most of the local fluid mechanical processes are understood; how these combine and what is the most appropriate framework to study and quantify the result is less clear. Extensive and structured experimental databases have been compiled recently in several laboratories. A number of major field experiments in urban areas have been completed very recently and more are planned. These have aided understanding as well as model development and evaluation.
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  • 16
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    Annual Review of Fluid Mechanics 35 (2003), S. 295-315 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract It is classically assumed that the far field of a round turbulent jet discharging into quiescent fluid has a unique behavior characterized only by its momentum flux. However, there is now considerable evidence that different discharge conditions at the jet nozzle exit can give rise to very different far-field flows. Perhaps the most striking examples of these are the bifurcating and blooming jets produced by appropriate combinations of controlled axial and circumferential excitations at the nozzle exit. With the right excitations, a jet can be made to divide into two separate jets (bifurcating jet), each of which carries half the axial momentum and spreads in a manner similar to a single jet. Trifurcating jets can also be produced. Other excitations can produce blooming jets, in which the jet explodes into a shower of vortex rings, producing a far-field flow that is quite unlike a normal unexcited jet. Bifurcating and blooming jets exhibit much greater mixing than normal jets, suggesting possible applications in flow control. This article summarizes our work on bifurcating and blooming jets, which began with our discovery of them in the early 1980s and continued through the mid- 1990s. One of us (D.E.P.) continued exploration of flow control using excited jets, first at the McDonnell Douglas Corporation, and more recently at the Georgia Institute of Technology. The key to flow control is the manipulation of the large vortical structures in the near field of the jet. Ultimately this work, and that of others, led to full-scale testing of jet engine exhaust mixing control. There it was shown that the jet temperature downstream of the engine can be very significantly reduced by application of well-designed and easily implemented excitation at the engine discharge, thereby solving problems encountered during ground operations. Related jet control work by other investigators is included in this review.
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    Annual Review of Fluid Mechanics 35 (2003), S. 413-440 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The recent progress in three-dimensional boundary-layer stability and transition is reviewed. The material focuses on the crossflow instability that leads to transition on swept wings and rotating disks. Following a brief overview of instability mechanisms and the crossflow problem, a summary of the important findings of the 1990s is given.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 183-206 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Cyclooxygenases-1 and -2 (COX-1 and COX-2, also known as prostaglandin H2 synthases-1 and -2) catalyze the committed step in prostaglandin synthesis. COX-1 and -2 are of particular interest because they are the major targets of nonsteroidal antiinflammatory drugs (NSAIDs) including aspirin, ibuprofen, and the new COX-2-selective inhibitors. Inhibition of the COXs with NSAIDs acutely reduces inflammation, pain, and fever, and long-term use of these drugs reduces the incidence of fatal thrombotic events, as well as the development of colon cancer and Alzheimer's disease. In this review, we examine how the structures of COXs relate mechanistically to cyclooxygenase and peroxidase catalysis and how alternative fatty acid substrates bind within the COX active site. We further examine how NSAIDs interact with COXs and how differences in the structure of COX-2 result in enhanced selectivity toward COX-2 inhibitors.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 425-443 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Understanding the action of enzymes on an atomistic level is one of the important aims of modern biophysics. This review describes the state of the art in addressing this challenge by simulating enzymatic reactions. It considers different modeling methods including the empirical valence bond (EVB) and more standard molecular orbital quantum mechanics/molecular mechanics (QM/MM) methods. The importance of proper configurational averaging of QM/MM energies is emphasized, pointing out that at present such averages are performed most effectively by the EVB method. It is clarified that all properly conducted simulation studies have identified electrostatic preorganization effects as the source of enzyme catalysis. It is argued that the ability to simulate enzymatic reactions also provides the chance to examine the importance of nonelectrostatic contributions and the validity of the corresponding proposals. In fact, simulation studies have indicated that prominent proposals such as desolvation, steric strain, near attack conformation, entropy traps, and coherent dynamics do not account for a major part of the catalytic power of enzymes. Finally, it is pointed out that although some of the issues are likely to remain controversial for some time, computer modeling approaches can provide a powerful tool for understanding enzyme catalysis.
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    Annual Review of Materials Research 33 (2003), S. 263-288 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The use of low-energy electron microscopy (LEEM) to study reversible surface phase transitions is reviewed. Representative experiments are described that highlight the key advantages of LEEM: the ability to image surfaces in situ, at elevated temperature, with good spatial and temporal resolution. With these capabilities, the evolution of individual surface features-domains, facets, islands, steps, etc.-can be measured. Real-time and real-space imaging make LEEM a powerful tool for characterizing the thermodynamics and kinetics that govern surface phase transformations.
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    Annual Review of Materials Research 33 (2003), S. 233-261 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Anhydrous proton-conducting polymers usually consist of a more or less inert polymer matrix that is swollen with an appropriate proton solvent (in most cases, phosphoric acid). An outline of the different materials is provided, with a focus on PBI/H3PO4 blends that are currently most suitable for fuel cell applications. Also discussed are alternative concepts for fully polymeric materials, which establish proton conductivity as an intrinsic property using amphoteric heterocycles such as imidazole as a proton solvent. The development of some of the first polymers is described, and the fundamental relations between their material properties and conductivity are discussed. Closely related to this relatively new concept are mechanistic investigations focusing on intermolecular proton transfer and diffusion of (protonated) solvent molecules, the contributions of both transport processes to conductivity, and the dependence of these ratios on composition, charge carrier density, etc. Although the development of fully polymeric proton conductors is inseparably related to mechanistic considerations, relatively little attention has been paid to these concepts in the field of conventional membranes (hydrated ionomers, H3PO4-based materials). Consequently, their general relevance is emphasized, and according investigations are summarized to provide a more comprehensive picture of proton transport processes within proton exchange membranes.
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    Annual Review of Materials Research 33 (2003), S. 289-319 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The need to operate polymer electrolyte membrane (PEM) fuel cells at temperatures above 100oC, where the amount of water in the membrane is restricted, has provided much of the motivation for understanding the mechanisms of proton conduction at low degrees of hydration. Although experiments have not provided any direct information, numerous theoretical investigations have begun to provide the basis for understanding the mechanisms of proton conduction in these nano-phase-separated materials. Both the hydrated morphology and the nature of the confined water in the hydrophilic domains influence proton dissociation from the acidic sites (i.e., -SO3H), transfer to the water environment, and transport through the membrane. The following molecular processes are discussed in connection to their role in the conduction of protons in sulfonic acid-based polymer electrolyte membranes (PEMs): (a) local chemistry of the hydrophilic side chains; its effect on the dissociation of the proton and eventual stabilization (separation) of the proton in the water; (b) the presence of neighboring sulfonic acid groups on proton transfer; and (c) the effect of the distribution of the sulfonate groups on the transport of protons in the channels/pores of the membrane.
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    Annual Review of Materials Research 33 (2003), S. 333-359 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The structural and chemical parameters determining the formation and mobility of protonic defects in oxides are discussed, and the paramount role of high-molar volume, coordination numbers, and symmetry are emphasized. Symmetry also relates to the structural and chemical matching of the acceptor dopant. Y-doped BaZrO3-based oxides are demonstrated to combine high stability with high proton conductivity that exceeds the conductivity of the best oxide ion conductors at temperatures below about 700oC. The unfavorably high grain boundary impedances and brittleness of ceramics have been reduced by forming solid solutions with small amounts of BaCeO3, and an initial fuel cell test has demonstrated that proton-conducting electrolytes based on Y-doped BaZrO3 provide alternatives for separator materials in solid oxide fuel cells (SOFCs). These materials have the potential to operate at lower temperatures compared with those of conventional SOFCs, and the appearance of chemical water diffusion across the electrolyte at typical operation temperatures (T = 500-800oC) allows the use of dry methane as a fuel.
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    Annual Review of Materials Research 33 (2003), S. 321-331 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Recently, a number of papers about direct oxidation of methane and hydrocarbon in solid oxide fuel cells (SOFC) at relatively low temperatures (about 700oC) have been published. Even though the conversion of almost dry CH4 at 1000oC on ceramic anodes was demonstrated more than 10 years ago, the reports about high-current densities for methane oxidation at such low temperatures are indeed surprising. Several papers indicate that a catalytic effect (due to the mixed ionic and electronic conductivity) of CeO2-x is partially responsible for this effect. However, this seems to contradict previous reports, and thus this issue deserves further analysis.
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    Annual Review of Materials Research 33 (2003), S. 383-417 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The emphasis in this short review is to describe the materials issues involved in the development of present thermal barrier coatings and the advances necessary for the next generation, higher temperature capability coatings.
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    Annual Review of Materials Research 33 (2003), S. 361-382 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several recent experimental and numerical investigations have contributed to the improved understanding of the electrochemical mechanisms taking place at solid oxide fuel cell (SOFC) cathodes and yielded valuable information on the relationships between alterable parameters (geometry/material) and the cathodic polarization resistance. Efforts to reduce the polarization resistance in SOFCs can benefit from these results, and some important aspects of the corresponding studies are reviewed. Experimental results, particularly measurements using geometrically well-defined Sr-doped LaMnO3 (LSM) cathodes, are discussed. In regard to simulations, the different levels of sophistication used in SOFC electrode modeling studies are summarized and compared. Exemplary simulations of mixed conducting cathodes that show the capabilities and limits of different modeling levels are described.
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    Annual Review of Materials Research 33 (2003), S. 419-501 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This account reviews the discovery, synthesis, properties, and the latest research advances of carbon nanotubes developed over the past 12 years. Because of their remarkable electronic and mechanical properties, carbon nanotubes are unique and exciting. The field has been developed rapidly, and the number of publications per year is increasing almost exponentially. Various technological applications are likely to arise using nanotubes for fabrication of flat panel displays, gas storage devices, toxic gas sensors, Li+ batteries, robust and lightweight composites, conducting paints, electronic nanodevices, etc. Further experimental and theoretical research is still necessary so that novel technologies will become a reality in the early twenty-first century.
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    Annual Review of Materials Research 33 (2003), S. 215-231 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a review of atomic-scale defects (planar defects and dislocations) analysis using atom probe (AP) and field ion microscopy (FIM). A large part of the discussion is dedicated to the first atomic-scale observation of a Cottrell atmosphere by a three-dimensional atom probe method (3DAP). The nanoscale boron segregation to line dislocations and planar defects in a B2-ordered FeAl (40 at.%Al) is imaged in three dimensions of the real space. The boron-enriched Cottrell atmosphere is imaged in the close vicinity of an edge 001〉 dislocation as a rod 3 nm in diameter, around to the dislocation line.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 15-56 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: The galaxies of the Local Group serve as important laboratories for understanding the physics of massive stars. Here I discuss what is involved in identifying various kinds of massive stars in nearby galaxies: the hydrogen-burning O-type stars and their evolved He-burning evolutionary descendants, the luminous blue variables, red supergiants, and Wolf-Rayet stars. Primarily I review what our knowledge of the massive star population in nearby galaxies has taught us about stellar evolution and star formation. I show that the current generation of stellar evolutionary models do well at matching some of the observed features and provide a look at the sort of new observational data that will provide a benchmark against which new models can be evaluated.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 169-189 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: The first law of theoretical physics, the Newtonian law of gravitation, relies on the concept of action at a distance. The success of this law led to the concept being applied to electricity and magnetism, which were next to be explored in depth. Here the action at a distance had a limited success and ultimately had to be abandoned in favor of the increasingly more popular field theory. Nevertheless, in the 1940s, an attempt was made to revive the concept of action at a distance in a relativistically invariant way by Wheeler & Feynman (1945, 1949). It inspired a series of investigations in both electrodynamics and gravity in which the field concept was not used but the interaction was described as taking place directly between particles. As it impinged very intimately on cosmology, Hoyle was keenly interested in it. This review discusses the work by Hoyle, the author, and others on the development of electrodynamics and gravitation as direct particle theories. In this review, the author discusses how the work was started and went through stages of increasing sophistication, e.g., extending the Wheeler-Feynman electrodynamics to curved spacetime, its consequences in different cosmologies, and the issues arising from its quantization. The resolution of ultraviolet divergences in quantum electrodynamics is also briefly discussed. The parallel development of a Machian theory of gravitation followed the lead from electrodynamics. In both theories one sees a strong link between the large-scale structure of the universe and local physics, as might be expected from an action-at-a-distance framework.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 343-390 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Targeted laboratory astrophysics measurements are being conducted to address the needs of X-ray astronomy. The measurements are producing large sets of reliable atomic data, which include ionization and recombination cross sections for charge balance calculations, as well as line lists, excitation cross sections, and dielectronic recombination rates for interpreting X-ray line formation. Additional experiments focus on resolving specific puzzles posed by astrophysical observations, as well as on calibrating existing and developing new X-ray line diagnostics. We discuss the types of data produced and illustrate how the laboratory measurements support such missions as ASCA, EUVE, Chandra, XMM, and ASTRO-E2.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 517-554 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Photoionized clouds are ubiquitous. They define the endpoints of stellar evolution (H II regions and planetary nebulae), constitute the interstellar and intergalactic media, and are found in high redshift quasars and star-forming galaxies. The spectra of these objects are dominated by emission lines that are sensitive to details of the emitting gas. These details include the microscopic atomic processes that cause the gas to glow; the density, composition, and temperature of the gas; and the radiation field of the central continuum source. Large-scale numerical codes that incorporate all the needed physics and predict the observed spectrum have become essential tools in understanding these objects. This article reviews the current status of the numerical simulations of emitting gas, with particular emphasis on photoionized clouds and the underlying simplicity that governs these nebulae; the types of questions that can be addressed by today's codes; and the big questions that remain unanswered.
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    Annual Review of Fluid Mechanics 35 (2003), S. 169-182 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The modern study of a crowd as a flowing continuum is a recent development. Distinct from a classical fluid because of the property that a crowd has the capacity to think, interesting new physical ideas are involved in its study. An appealing property of a crowd in motion is that the nonlinear, time-dependent, simultaneous equations representing a crowd are conformably mappable. This property makes many interesting applications analytically tractable. In this review examples are given in which the theory has been used to provide possible assistance in the annual Muslim Hajj, to understand the Battle of Agincourt, and, surprisingly, to locate barriers that actually increase the flow of pedestrians above that when there are no barriers present. Modern developments may help prevent some of the approximately two thousand deaths that annually occur in accidents owing to crowding.The field of crowd motion, that is, the field of "thinking fluids," is an intriguing area of research with great promise.
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    Annual Review of Fluid Mechanics 35 (2003), S. 267-293 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The recent avalanche of research activity in the field of granular matter has yielded much progress. The use of state-of-the-art (and other) computational and experimental methods has led to the discovery of new states and patterns and enabled detailed tests of theories and models. The application of statistical mechanical methods and phenomenology has contributed to the understanding of the microscopic a nd macroscopic properties of granular systems. Some previously open problems seem to be solved. Fluidized granular systems (rapid granular flows), recently referred to as granular gases, are often modeled by hydrodynamic equations of motion, some of which are based on systematic expansions applied to the pertinent Boltzmann equation. The undeniable success of granular hydrodynamics is somewhat surprising in view of the lack of scale separation in these systems and the neglect of certain correlations in most derivations of the hydrodynamic equations. Microstructures have been recognized as key features of granular gases; explanations for their existence have been proposed, and many of their properties elucidated. Granular-gas multistability can often be traced back to microstructure dynamics. In spite of these and other impressive advances, this field still poses serious challenges.
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    Annual Review of Fluid Mechanics 35 (2003), S. 317-340 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Recent advances in achieving textbook multigrid efficiency for fluid simulations are presented. Textbook multigrid efficiency is defined as attaining the solution to the governing system of equations in a computational work that is a small multiple of the operation counts associated with discretizing the system. Strategies are reviewed to attain this efficiency by exploiting the factorizability properties inherent to a range of fluid simulations, including the compressible Navier-Stokes equations. Factorizability is used to separate the elliptic and hyperbolic factors contributing to the target system; each of the factors can then be treated individually and optimally. Boundary regions and discontinuities are addressed with separate (local) treatments. New formulations and recent calculations demonstrating the attainment of textbook efficiency for aerodynamic simulations are shown.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 1-25 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Mass spectrometry has provided a powerful method for monitoring hydrogen exchange of protein backbone amides with deuterium from solvent. In comparison to popular NMR approaches, mass spectrometry has the advantages of higher sensitivity, wider coverage of sequence, and the ability to analyze larger proteins. Proteolytic fragmentation of proteins following the exchange reaction provides moderate structural resolution, in some cases enabling measurements from single amides. The technique has provided new insight into protein-protein and protein-ligand interfaces, as well as conformational changes during protein folding or denaturation. In addition, recent studies illustrate the utility of hydrogen exchange mass spectrometry toward detecting protein motions relevant to allostery, covalent modifications, and enzyme function.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 27-45 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Cations are bound to nucleic acids in a solvated state. High-resolution X-ray diffraction studies of oligonucleotides provide a detailed view of Mg2+, and occasionally other ions bound to DNA. In a survey of several such structures, certain general observations emerge. First, cations bind preferentially to the guanine base in the major groove or to phosphate group oxygen atoms. Second, cations interact with DNA most frequently via water molecules in their primary solvation shell, direct ion-DNA contacts being only rarely observed. Thus, the solvated ions should be viewed as hydrogen bond donors in addition to point charges. Finally, ion interaction sites are readily exchangeable: The same site may be occupied by any ion, including spermine, as well as by a water molecule.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 69-92 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Although protein function is thought to depend on flexibility, precisely how the dynamics of the molecule and its environment contribute to catalytic mechanisms is unclear. We review experimental and computational work relating to enzyme dynamics and function, including the role of solvent. The evidence suggests that fast motions on the 100 ps timescale, and any motions coupled to these, are not required for enzyme function. Proteins where the function is electron transfer, proton tunneling, or ligand binding may have different dynamical dependencies from those for enzymes, and enzymes with large turnover numbers may have different dynamical dependencies from those that turn over more slowly. The timescale differences between the fastest anharmonic fluctuations and the barrier-crossing rate point to the need to develop methods to resolve the range of motions present in enzymes on different time- and lengthscales.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 115-133 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The OB-fold domain is a compact structural motif frequently used for nucleic acid recognition. Structural comparison of all OB-fold/nucleic acid complexes solved to date confirms the low degree of sequence similarity among members of this family while highlighting several structural sequence determinants common to most of these OB-folds. Loops connecting the secondary structural elements in the OB-fold core are extremely variable in length and in functional detail. However, certain features of ligand binding are conserved among OB-fold complexes, including the location of the binding surface, the polarity of the nucleic acid with respect to the OB-fold, and particular nucleic acid-protein interactions commonly used for recognition of single-stranded and unusually structured nucleic acids. Intriguingly, the observation of shared nucleic acid polarity may shed light on the longstanding question concerning OB-fold origins, indicating that it is unlikely that members of this family arose via convergent evolution.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 469-492 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The observation of liquid-liquid immiscibility in cholesterol-phospholipid mixtures in monolayers and bilayers has opened a broad field of research into their physical chemistry. Some mixtures exhibit multiple immiscibilities. This unusual property has led to a thermodynamic model of "condensed complexes." These complexes are the consequence of an exothermic, reversible reaction between cholesterol and phospholipids. In this quantitative model the complexes are sometimes concentrated in a separate liquid phase. The phase separation into a complex-rich phase depends on membrane composition and intensive variables such as temperature. The properties of defined cholesterol-phospholipid mixtures provide a conceptual foundation for the exploration of a number of aspects of the biophysics and biochemistry of animal cell membranes.
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    Annual Review of Materials Research 33 (2003), S. 29-54 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Interfacial adhesion plays a central role in a number of technologically important applications. Quantitatively measuring the adhesion of an interface and understanding the processes and controlling mechanisms of energy dissipation is not always a straightforward task, however. It is often not enough to know that an interface in a particular application is weak and prone to failure because it can be difficult to accurately recreate that interface with a bulk specimen and derive a meaningful adhesion value. Rather, a fundamental knowledge of the processes that actually contribute to the interfacial strength is important, so that, when bulk specimens are prepared, care can be taken to eliminate energy-absorbing processes that are not present in the actual application. Accordingly, this paper reviews some of the literature highlighting the contributing factors that control interfacial adhesion. The focus is on those models that describe the detailed mechanisms of the energy-absorbing processes and on some of the experimental data that illustrates those models.
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    Annual Review of Materials Research 33 (2003), S. 1-27 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The hydrogen economy is fast approaching as petroleum reserves are rapidly consumed. The fuel cell promises to deliver clean and efficient power by combining hydrogen and oxygen in a simple electrochemical device that directly converts chemical energy to electrical energy. Hydrogen, the most plentiful element available, can be extracted from water by electrolysis. One can imagine capturing energy from the sun and wind and/or from the depths of the earth to provide the necessary power for electrolysis. Alternative energy sources such as these are the promise for the future, but for now they are not feasible for power needs across the globe. A transitional solution is required to convert certain hydrocarbon fuels to hydrogen. These fuels must be available through existing infrastructures such as the natural gas pipeline. The present review discusses the catalyst and adsorbent technologies under development for the extraction of hydrogen from natural gas to meet the requirements for the proton exchange membrane (PEM) fuel cell. The primary market is for residential applications, where pipeline natural gas will be the source of H2 used to power the home. Other applications including the reforming of methanol for portable power applications such as laptop computers, cellular phones, and personnel digital equipment are also discussed. Processing natural gas containing sulfur requires many materials, for example, adsorbents for desulfurization, and heterogeneous catalysts for reforming (either autothermal or steam reforming) water gas shift, preferential oxidation of CO, and anode tail gas combustion. All these technologies are discussed for natural gas and to a limited extent for reforming methanol.
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    Annual Review of Materials Research 33 (2003), S. 55-90 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Chemical reactivity at heterophase interfaces is reviewed with a special focus on metal-oxide and oxide-oxide interfaces. Equilibrium chemistry of interfaces is discussed in terms of processes at the macroscopic and atomic level. The dependency on thermodynamic and crystallographic variables is described and illustrated by experimental results. Any reaction-related motion of an interface is associated with numerous transport and reaction steps that include not only atom transfer across the interface, chemical reactions between species and defects and phase transitions, but also steps accommodating lattice mismatch and volume changes. Faceting and morphology evolution of interfaces are included in the considerations.
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    Annual Review of Materials Research 33 (2003), S. 91-128 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The performance of the oxide-ion electrolyte of a solid oxide fuel cell (SOFC) is critical to the development of an intermediate-temperature system. Although yttria-stabilized zirconia is the electrolyte used in SOFCs under commercial development, other candidate materials are now available, and there remains a strong motivation to search for new, improved oxide-ion electrolytes. The leading contenders are discussed not only with respect to their oxide-ion conductivity, but also with respect to mechanical and chemical compatibility with the electrodes and the working environment at each electrode.
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    Annual Review of Materials Research 33 (2003), S. 129-154 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The main obstacles to greater commercialization of polymer electrolyte fuel cells are mostly related to the low-proton conductivity at low-relative humidity of the known ionomeric membranes, to their high methanol permeability and poor mechanical properties above ~130oC. A possible solution for these problems has been found in the development of composite membranes, where particles of suitable fillers are dispersed in the ionomer matrix. The preparation methods for obtaining composite membranes are described, and recent work dealing with composite ionomeric membranes containing silica, heteropolyacids, layered metal phosphates, and phosphonates is reviewed. Finally, new strategies for the preparation of nano-composite membranes and for the filling of porous polymeric membranes with highly conductive zirconium phosphonates are described. The expected influence of size and orientation of these particles on membrane properties, such as conductivity and permeability to methanol, is also discussed.
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    Annual Review of Materials Research 33 (2003), S. 169-182 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Solid oxide fuel cells operating at temperatures below 800oC require the use of supported thin film solid electrolytes. A variety of processing methods are reviewed that can deliver electrolyte films with satisfactory performance. These include vapor phase, sol-gel, and powder methods such as colloidal deposition. An important consideration is that a number of these processing methods may not meet the low cost required by commercialization. The most cost-effective methods are considered to be simple powder methods combined with co-firing.
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    Annual Review of Materials Research 33 (2003), S. 155-168 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Methanol oxidation in the cathode compartment of the fuel cell, which occurs during the oxygen-reduction reaction on Pt-based cathodes, constitutes a significant performance loss in the direct methanol fuel cells. Over the past decade, four types of methanol-resistant oxygen-reduction catalysts have been developed to circumvent this problem. Among these, transition-metal chalcogenides, and in particular RuSe, have shown effective selectivity to oxygen-reduction reaction in the presence of methanol. These catalysts not only can enhance the performance of the conventional direct methanol fuel cells but also could provide a route to develop mixed-reactants direct methanol fuel cells, which could be highly cost-effective in comparison with the conventional direct methanol fuel cells. This article is a brief update on the preparation, characterization, and implications of methanol-resistant oxygen-reduction catalysts.
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    Annual Review of Materials Research 33 (2003), S. 183-213 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract After a brief survey of fuel cell types, attention is focused on material requirements for SOFC and PEMFC stacks, with an introductory section on materials technology for reformers. Materials cost and processing, together with durability issues, are emphasized as these now dominate materials selection processes for prototype stack units. In addition to optimizing the cell components, increasing attention is being given to the composition and processing of the bipolar plate component as the weight and volume of the relevant material has a major influence on the overall power density and cost of the fuel cell stack. It is concluded that the introduction of alternative materials/processes that would enable PEMFC stacks to operate at 150-200oC, and IT-SOFC stacks to operate at 500-700oC, would have a major impact on the successful commercialization of fuel cell technology.
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    Annual Review of Materials Research 33 (2003), S. 581-610 
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The use of chemical potential diagrams to examine interface chemistry is discussed in terms of the chemical reactions among oxides and associated interdiffusion across the interface. The driving force for both processes can be determined from the chemical potential values. The geometrical features of the chemical potential diagrams can be related to the valence stability of binary oxides and the stabilization energy of double oxides from the constituent oxides. The materials compatibility in solid oxide fuel cell materials is discussed with a focus on a lanthanum manganite cathode and a yttria-stabilized zirconia (YSZ) electrolyte. Emphasis is placed on the valence numbers of manganese in the fluorite solid solution and the perovskite oxides, which have been derived by thermodynamic analysis of the magnitude of the stabilization energy/interaction parameters as a function of ionic size for respective valence numbers. The change of manganese valence on La2Zr2O7 formation and Mn dissolution in YSZ are discussed in relation with the oxygen evolution/adsorption process. Oxygen flow associated with electrochemical reactions exhibits markedly different features depending on the direction of the polarization, which can lead to drastic changes in the interface chemistry (precipitation or interdiffusion).
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 1-14 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Astrophysics has been an important part of my personal and scientific life three times. The first was in 1938 when I did work on stellar energy production. The second was a joyful period nearly 30 years later when that work was rewarded with the Nobel Prize in physics. And the third has lasted over the time since my retirement in 1975 during which Gerry Brown and I have had a very satisfactory collaboration exploring various aspects of supernovae and, more recently, binary pairs.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 117-167 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Blueshifted absorption lines in the UV and X-ray spectra of active galaxies reveal the presence of massive outflows of ionized gas from their nuclei. The "intrinsic" UV and X-ray absorbers show large global covering factors of the central continuum source, and the inferred mass loss rates are comparable to the mass accretion rates. Many absorbers show variable ionic column densities, which are attributed to a combination of variable ionizing flux and motion of gas into and out of the line of sight. Detailed studies of the intrinsic absorbers, with the assistance of monitoring observations and photoionization models, provide constraints on their kinematics, physical conditions, and locations relative to the central continuum source, which range from the inner nucleus (~0.01 pc) to the galactic disk or halo (~10 kpc). Dynamical models that make use of thermal winds, radiation pressure, and/or hydromagnetic flows have reached a level of sophistication that permits comparisons with the observational constraints.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 465-515 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Old, cool white dwarfs convey valuable information about the early history of our Galaxy. They have been used to determine the age of the galactic disk, several open clusters, and a globular cluster. We review the current understanding of the physics of cool white dwarfs, including their mass distribution, chemical evolution, magnetism, and cooling. We also examine the role of white dwarfs as tracers of various stellar populations, both in terms of observational searches and theoretical models.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 429-463 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Giant planets have now been discovered around other stars, and it is only a matter of time until Earth-sized planets are detected. Whether any of these planets are suitable for life depends on their volatile abundances, especially water, and on their climates. Only planets within the liquid-water habitable zone (HZ) can support life on their surfaces and, thus, can be analyzed remotely to determine whether they are inhabited. Fortunately, current models predict that HZs are relatively wide around main-sequence stars not too different from our sun. This conclusion is based on studies of how our own planet has evolved over time. Earth's climate has remained conducive to life for the past 3.5 billion years or more, despite a large increase in solar luminosity, probably because of previous higher concentrations of CO2 and/or CH4. Both these gases are involved in negative feedback loops that help to stabilize the climate. In addition to these topics, we also briefly discuss the rise of atmospheric O2 and O3, along with their possible significance as indicators of life on other planets.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 57-115 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Stellar clusters are born embedded within giant molecular clouds (GMCs) and during their formation and early evolution are often only visible at infrared wavelengths, being heavily obscured by dust. Over the past 15 years advances in infrared detection capabilities have enabled the first systematic studies of embedded clusters in galactic molecular clouds. In this article we review the current state of empirical knowledge concerning these extremely young protocluster systems. From a survey of the literature we compile the first extensive catalog of galactic embedded clusters. We use the catalog to construct the mass function and estimate the birthrate for embedded clusters within ~2 kpc of the sun. We find that the embedded cluster birthrate exceeds that of visible open clusters by an order of magnitude or more indicating a high infant mortality rate for protocluster systems. Less than 4-7% of embedded clusters survive emergence from molecular clouds to become bound clusters of Pleiades age. The vast majority (90%) of stars that form in embedded clusters form in rich clusters of 100 or more members with masses in excess of 50 Mo. Moreover, observations of nearby cloud complexes indicate that embedded clusters account for a significant (70-90%) fraction of all stars formed in GMCs. We review the role of embedded clusters in investigating the nature of the initial mass function (IMF) that, in one nearby example, has been measured over the entire range of stellar and substellar mass, from OB stars to substellar objects near the deuterium burning limit. We also review the role embedded clusters play in the investigation of circumstellar disk evolution and the important constraints they provide for understanding the origin of planetary systems. Finally, we discuss current ideas concerning the origin and dynamical evolution of embedded clusters and the implications for the formation of bound open clusters.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 391-427 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: In this contribution, a review is presented on the ample data obtained on post-AGB stars, both on the central stars and their circumstellar material. The fast evolutionary phase is characterized by a rapid change in the properties of the objects, but the variety is so large that there is yet no clear consensus on how the detailed studies of individual objects are linked together by evolutionary channels. The absence of strong molecular veiling in the photospheres of the central stars, together with a spread in intrinsic metallicity make post-AGB stars very useful in constraining AGB chemical evolutionary models. We discuss the surprisingly wide variety of chemical signatures observed. The onset in the creation process of the panoply of structures and shapes observed in planetary nebulae occurs during the short post-AGB evolution, but the physical nature of the processes involved is still badly understood. In the rapidly growing field of circumstellar mineralogy, post-AGB stars have their story to tell and also the molecular envelope changes significantly due to dilution and hardening of the stellar radiation. The real-time evolution of some objects suffering a late thermal flash is reviewed and their possible link to other hydrogen-deficient objects is discussed. Any review on stellar evolution has a section on binaries and this contribution is no exception because binaries make up a significant fraction of the post-AGB stars known to date.
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    Annual Review of Fluid Mechanics 35 (2003), S. 11-21 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Full-scale icing experiments and, therefore, certification time and cost can be significantly reduced by developing calculation methods to evaluate the aircraft and system performance for a wide range of icing conditions. This article summarizes calculation methods for icing that include ice accretion, ice system performance, and icing effects on aircraft.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 207-235 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Structural and thermodynamic characterizations of a variety of intra- and intermolecular interactions stabilizing/destabilizing protein systems represent a major part of multidisciplinary efforts aimed at solving the problems of protein folding and binding. To this end, volumetric techniques have been successfully used to gain insights into protein hydration and intraglobular packing. Despite the fact that the use of volumetric measurements in protein-related studies dates back to the 1950s, such measurements still represent a relatively untapped yet potentially informative means for tackling the problems of protein folding and binding. This notion has been further emphasized by recent advances in the development of highly sensitive volumetric instrumentation that has led to intensifying volumetric investigations of protein systems. This paper reviews the volumetric properties of proteins and their low-molecular-weight analogs, in particular, discussing the recent progress in the use of volumetric data for studying conformational transitions of proteins as well as protein-ligand, protein-protein, and protein-nucleic acid interactions.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 237-256 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract This review focuses on cofactor-ligand and protein-protein interactions within the photosystem I reaction center. The topics include a description of the electron transfer cofactors, the mode of binding of the cofactors to protein-bound ligands, and a description of intraprotein contacts that ultimately allow photosystem I to be assembled (in cyanobacteria) from 96 chlorophylls, 22 carotenoids, 2 phylloquinones, 3 [4Fe-4S] clusters, and 12 polypeptides. During the 15 years that have elapsed from the first report of crystals to the atomic-resolution X-ray crystal structure, cofactor-ligand interactions and protein-protein interactions were systematically being explored by spectroscopic and genetic methods. This article charts the interplay between these disciplines and assesses how good the early insights were in light of the current structure of photosystem I.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 257-283 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Lipid raft microdomains were conceived as part of a mechanism for the intracellular trafficking of lipids and lipid-anchored proteins. The raft hypothesis is based on the behavior of defined lipid mixtures in liposomes and other model membranes. Experiments in these well-characterized systems led to operational definitions for lipid rafts in cell membranes. These definitions, detergent solubility to define components of rafts, and sensitivity to cholesterol deprivation to define raft functions implicated sphingolipid- and cholesterol-rich lipid rafts in many cell functions. Despite extensive work, the basis for raft formation in cell membranes and the size of rafts and their stability are all uncertain. Recent work converges on very small rafts 〈10 nm in diameter that may enlarge and stabilize when their constituents are cross-linked.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 335-373 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Molecular docking is an invaluable tool in modern drug discovery. This review focuses on methodological developments relevant to the field of molecular docking. The forces important in molecular recognition are reviewed and followed by a discussion of how different scoring functions account for these forces. More recent applications of computational chemistry tools involve library design and database screening. Last, we summarize several critical methodological issues that must be addressed in future developments.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 311-334 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Acetylcholine binding protein (AChBP) has recently been identified from molluskan glial cells. Glial cells secrete it into cholinergic synapses, where it plays a role in modulating synaptic transmission. This novel mechanism resembles glia-dependent modulation of glutamate synapses, with several key differences. AChBP is a homolog of the ligand binding domain of the pentameric ligand-gated ion-channels. The crystal structure of AChBP provides the first high-resolution structure for this family of Cys-loop receptors. Nicotinic acetylcholine receptors and related ion-channels such as GABAA, serotonin 5HT3, and glycine can be interpreted in the light of the 2.7 A AChBP structure. The structural template provides critical details of the binding site and helps create models for toxin binding, mutational effects, and molecular gating.
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    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 445-468 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Active transport of cations is achieved by a large family of ATP-dependent ion pumps, known as P-type ATPases. Various members of this family have been targets of structural and functional investigations for over four decades. Recently, atomic structures have been determined for Ca2+-ATPase by X-ray crystallography, which not only reveal the architecture of these molecules but also offer the opportunity to understand the structural mechanisms by which the energy of ATP is coupled to calcium transport across the membrane. This energy coupling is accomplished by large-scale conformational changes. The transmembrane domain undergoes plastic deformations under the influence of calcium binding at the transport site. Cytoplasmic domains undergo dramatic rigid-body movements that deliver substrates to the catalytic site and that establish new domain interfaces. By comparing various structures and correlating functional data, we can now begin to associate the chemical changes constituting the reaction cycle with structural changes in these domains.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 191-239 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: We review the origin, evolution, and physical nature of hot gas in elliptical galaxies and associated galaxy groups. Unanticipated recent X-ray observations with Chandra and XMM indicate much less cooling than previously expected. Consequently, many long-held assumptions must be reexamined or discarded and new approaches must be explored. Chief among these are the role of heating by active galactic nuclei, the influence of radio lobes on the hot gas, details of the cooling process, possible relation between the hot and colder gas in elliptical galaxies, and the complexities of stellar enrichment of the hot gas.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 241-289 
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: This review surveys the observed properties of interstellar dust grains: the wavelength-dependent extinction of starlight, including absorption features, from UV to infrared; optical luminescence; infrared emission; microwave emission; optical, UV, and X-ray scattering by dust; and polarization of starlight and of infrared emission. The relationship between presolar grains in meteorites and the interstellar grain population is discussed. Candidate grain materials and abundance constraints are considered. A dust model consisting of amorphous silicate grains, graphite grains, and polycyclic aromatic hydrocarbons is compared with observed emission and scattering. Some issues concerning evolution of interstellar dust are discussed.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 555-597 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: The status of our current understanding of angular momentum transport in accretion disks is reviewed. The last decade has seen a dramatic increase both in the recognition of key physical processes and in our ability to carry through direct numerical simulations of turbulent flow. Magnetic fields have at once powerful and subtle influences on the behavior of (sufficiently) ionized gas, rendering them directly unstable to free energy gradients. Outwardly descreasing angular velocity profiles are unstable. The breakdown of Keplerian rotation into MHD turbulence may be studied in some numerical detail, and key transport coefficients may be evaluated. Chandra observations of the Galactic Center support the existence of low luminosity accretion, which may ultimately prove amenable to global three-dimensional numerical simulation.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 599-643 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Helioseismology has transformed our knowledge of the Sun's rotation. Earlier studies revealed the Sun's surface rotation, but now a detailed observational picture has been built up of the internal rotation of our nearest star. Unlike the predictions of stellar-evolution models, the radiative interior is found to rotate roughly uniformly. The rotation within the convection zone is also very different from prior expectations, which had been that the rotation rate would depend primarily on the distance from the rotation axis. Layers of rotational shear have been discovered at the base of the convection zone and in the subphotospheric layers. Studies of the time variation of rotation have uncovered zonal-flow bands, extending through a substantial fraction of the convection zone, which migrate over the course of the solar cycle, and there are hints of other temporal variations and of a jet-like structure. At the same time, building on earlier work with mean-field models, researchers have made great progress in supercomputer simulations of the intricate interplay between turbulent convection and rotation in the Sun's interior. Such studies are beginning to transform our understanding of how rotation organizes itself in a stellar interior.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 291-342 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: The launches of the Chandra X-Ray Observatory in June 1999 and the XMM-Newton Observatory in December 1999 opened a new era in X-ray astronomy. Both of these missions incorporate novel diffraction grating spectrometers that are providing the first high-resolution X-ray spectra of most classes of astrophysical sources. The spectra obtained to date exhibit a wealth of discrete detail, yielding sensitive constraints on physical conditions in the emitting plasmas. We review the essential characteristics of these instruments, the basics of X-ray spectral formation in cosmic sources, and the exciting new results that have emerged from Chandra and XMM-Newton grating observations of a wide variety of astrophysical systems.
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    Annual Review of Astronomy and Astrophysics 41 (2003), S. 645-668 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Weak gravitational lensing provides a unique method to map directly the distribution of dark matter in the universe and to measure cosmological parameters. This cosmic-shear technique is based on the measurement of the weak distortions that lensing induces in the shape of background galaxies as photons travel through large-scale structures. This technique is now widely used to measure the mass distribution of galaxy clusters and has recently been detected in random regions of the sky. In this review, we present the theory and observational status of cosmic shear. We describe the principles of weak lensing and the predictions for the shear statistics in favored cosmological models. Next, we review the current measurements of cosmic shear and show how they constrain cosmological parameters. We then describe the prospects offered by upcoming and future cosmic-shear surveys as well as the technical challenges that have to be met for the promises of cosmic shear to be fully realized.
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    Annual Review of Fluid Mechanics 35 (2003), S. 23-43 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The more violent impacts of water waves on walls create velocities and pressures having magnitudes much larger than those associated with the propagation of ordinary waves under gravity. Insight into these effects has been gained by irrotational-flow computations and by investigating the role of entrained and trapped air in wave impacts. This review focuses on the results of theoretical work, making particular note of the value of considering pressure impulse, and highlights the aspects that are poorly understood.
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    Annual Review of Fluid Mechanics 35 (2003), S. 63-88 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper reviews recent advances in our understanding of the origin and hierarchy of organized flow structures in fluidized beds, distinction between bubbling and nonbubbling systems, and stages of bubble evolution. Experimental data and theory suggest that, at high particle concentrations, the particle-phase pressure arising from flow-induced velocity fluctuations decreases with increasing concentration of particles. This, in turn, implies that nonhydrodynamic stresses must be present to impart stability to a uniformly fluidized bed at very high particle concentrations. There is ample evidence to support an argument that, in commonly encountered gas-fluidized beds, yield stresses associated with enduring particle networks are present in the window of stable bed expansion, where the particles are essentially immobile until bubbling commences. However, some recent data on gas-fluidized beds of agglomerates of cohesive particles suggest that there exists a window of bed expansion where the bed does manifest a smooth appearance to the naked eye and the particles are mobile; at higher gas velocities the bed bubbles visibly. The mechanics of such beds remain to be fully explained.
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    Annual Review of Fluid Mechanics 35 (2003), S. 113-133 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A review is given of the stability of complex fluids subject to homogeneous states of shearing, a research field that is scarcely two decades old. For the benefit of fluid mechanicians, a brief, somewhat historical overview is presented of material instability in elastoplastic solids, where one finds a considerable body of experiment and a rich source of theoretical concepts including Hadamard instability, strain localization, and nonlocal constitutive models. A survey is then given of recent theoretical and experimental studies of instability with shear banding in various complex fluids, including micellar solutions, particulate suspensions, and rapidly sheared granular media. Various stability analyses are encapsulated in a mathematical dynamical-systems model for constitutive equations of the rate-type, and a general linear-stability theory is given for viscoelastic fluids in unbounded homogeneous shear flows. A general form of (Kelvin) wave-vector stretching is shown to play a key role in the growth of Fourier modes, as illustrated by recent computations for granular shear flow. The Fourier description also provides an explicit representation of higher-gradient (nonlocal) effects as higher-order powers of wave number.
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    Annual Review of Fluid Mechanics 35 (2003), S. 183-227 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Turbulence is ubiquitous in atmospheric clouds, which have enormous turbulence Reynolds numbers owing to the large range of spatial scales present. Indeed, the ratio of energy-containing and dissipative length scales is on the order of 105 for a typical convective cloud, with a corresponding large-eddy Reynolds number on the order of 106 to 107. A characteristic trait of high-Reynolds-number turbulence is strong intermittency in energy dissipation, Lagrangian acceleration, and scalar gradients at small scales. Microscale properties of clouds are determined to a great extent by thermodynamic and fluid-mechanical interactions between droplets and the surrounding air, all of which take place at small spatial scales. Furthermore, these microscale properties of clouds affect the efficiency with which clouds produce rain as well as the nature of their interaction with atmospheric radiation and chemical species. It is expected, therefore, that fine-scale turbulence is of direct importance to the evolution of, for example, the droplet size distribution in a cloud. In general, there are two levels of interaction that are considered in this review: (a) the growth of cloud droplets by condensation and (b) the growth of large drops through the collision and coalescence of cloud droplets. Recent research suggests that the influence of fine-scale turbulence on the condensation process may be limited, although several possible mechanisms have not been studied in detail in the laboratory or the field. There is a growing consensus, however, that the collision rate and collision efficiency of cloud droplets can be increased by turbulence-particle interactions. Adding strength to this notion is the growing experimental evidence for droplet clustering at centimeter scales and below, most likely due to strong fluid accelerations in turbulent clouds. Both types of interaction, condensation and collision-coalescence, remain open areas of research with many possible implications for the physics of atmospheric clouds.
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    Annual Review of Fluid Mechanics 35 (2003), S. 229-265 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This review describes some of the important developments in the numerical investigation of transition to turbulence in wall-bounded and free shear flows during the past decade. The evolution of numerical techniques and models as well as the advances in our theoretical understanding of the physics of laminar-turbulent transition that were achieved using these tools are described. For wall-bounded flows, particular emphasis is placed on investigations studying various scenarios of "bypass transition" in flows that are asymptotically stable. A brief review of investigations into receptivity and control of transitional flows is included.
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    Annual Review of Fluid Mechanics 35 (2003), S. 341-372 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We provide an overview of level set methods, introduced by Osher and Sethian, for computing the solution to fluid-interface problems. These are computational techniques that rely on an implicit formulation of the interface, represented through a time-dependent initial-value partial-differential equation. We discuss the essential ideas behind the techniques, the coupling of these techniques to finite-difference methods for incompressible and compressible flow, and a collection of applications including two-phase flow, ship hydrodynamics, and ink-jet-printhead design.
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    Annual Review of Fluid Mechanics 35 (2003), S. 441-468 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We review the most important theoretical and numerical results obtained in the realm of shell models for the energy-turbulent cascade. We mainly focus here on those results that had or will have some impact on the fluid-dynamics community. In particular, we address the problem of small-scale intermittency by discussing energy-helicity interactions, energy-dissipation multifractality, and universality of intermittency, i.e., independence of anomalous scaling exponents from large-scale forcing and boundary conditions. A multifractal-based description of multiscale and multitime correlation functions in turbulence is also presented. Finally, we also briefly review the analytical difficulties, and hopes, of calculating anomalous exponents.
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    Annual Review of Entomology 48 (2003), S. 29-50 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Vibratory signals of plant-dwelling insects, such as land bugs of the families Cydnidae and Pentatomidae, are produced mainly by stridulation and/or vibration of some body part. Signals emitted by the vibratory mechanisms have low-frequency characteristics with a relatively narrow frequency peak dominant around 100 Hz and differently expressed frequency modulation and higher harmonics. Such spectral characteristics are well tuned to the transmission properties of plants, and the low attenuation enables long-range communication on the same plant under standing wave conditions. Frequencies of stridulatory signals extend up to 10 kHz. In some groups, vibratory and stridulatory mechanisms may be used simultaneously to produce broadband signals. The subgenual organ, joint chordotonal organs, campaniform sensilla and mechanoreceptors, such as the Johnston's organ in antennae, are used to detect these vibratory signals. Species-specific songs facilitate mate location and recognition, and less species-specific signals provide information about enemies or rival mates.
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    Annual Review of Entomology 48 (2003), S. 51-72 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Insect-plant interactions involving the cultivated tomato and its relatives in the genus Lycopersicon have been intensively studied for several decades, resulting in one of the best documented and in-depth examples of the mechanistic complexities of insect-plant interactions, which encompass both herbivores and their natural enemies. Trichome-mediated defenses are particularly significant in L. hirsutum f. glabratum and have been extensively implicated in negative tritrophic effects mediated by direct contact of parasitoids and predators with trichomes, as well as indirect effects mediated through their hosts or prey. Both constitutive and inducible defense traits of L. esculentum exert effects on selected parasitoids and predators. The effects of any particular plant defense trait on parasitoids and predators depend on the specific attributes of the plant trait and the details of the physical, biochemical, and behavioral interaction between the natural enemy, its host (prey), and the plant.
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    Annual Review of Entomology 48 (2003), S. 111-139 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract The century-old discovery of the role of Anopheles in human malaria transmission precipitated intense study of this genus at the alpha taxonomy level, but until recently little attention was focused on the systematics of this group. The application of molecular approaches to systematic problems ranging from subgeneric relationships to relationships at and below the species level is helping to address questions such as anopheline phylogenetics and biogeography, the nature of species boundaries, and the forces that have structured genetic variation within species. Current knowledge in these areas is reviewed, with an emphasis on the Anopheles gambiae model. The recent publication of the genome of this anopheline mosquito will have a profound impact on inquiries at all taxonomic levels, supplying better tools for estimating phylogeny and population structure in the short term, and ultimately allowing the identification of genes and/or regulatory networks underlying ecological differentiation, speciation, and vectorial capacity.
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    Annual Review of Entomology 48 (2003), S. 163-184 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Secretions of male accessory glands contain a variety of bioactive molecules. When transferred during mating, these molecules exert wide-ranging effects on female reproductive activity and they improve the male's chances of siring a significant proportion of the female's offspring. The accessory gland secretions may affect virtually all aspects of the female's reproductive activity. The secretions may render her unwilling or unable to remate for some time, facilitating sperm storage and ensuring that any eggs laid will be fertilized by that male's sperm. They may stimulate an increase in the number and rate of development of eggs and modulate ovulation and/or oviposition. Antimicrobial agents in the secretions ensure that the female reproductive tract is a hospitable environment during sperm transfer. In a few species the secretions include noxious chemicals. These are sequestered by developing eggs that are thereby protected from predators and pathogens when laid.
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    Annual Review of Entomology 48 (2003), S. 211-234 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Comparative analysis of the complete genome sequences of 13 baculoviruses revealed a core set of 30 genes, 20 of which have known functions. Phylogenetic analyses of these 30 genes yielded a tree with 4 major groups: the genus Granulovirus (GVs), the group I and II lepidopteran nucleopolyhedroviruses (NPVs), and the dipteran NPV, CuniNPV. These major divisions within the family Baculoviridae were also supported by phylogenies based on gene content and gene order. Gene content mapping has revealed the patterns of gene acquisitions and losses that have taken place during baculovirus evolution, and it has highlighted the fluid nature of baculovirus genomes. The identification of shared protein phylogenetic profiles provided evidence for two putative DNA repair systems and for viral proteins specific for infection of lymantrid hosts. Examination of gene order conservation revealed a core gene cluster of four genes, helicase, lef-5, ac96, and 38K(ac98), whose relative positions are conserved in all baculovirus genomes.
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    Annual Review of Entomology 48 (2003), S. 261-281 
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Ideally, integrated pest management should rely on an array of tactics. In reality, the main technologies in use are synthetic pesticides. Because of well-documented problems with reliance on synthetic pesticides, viable alternatives are sorely needed. Physical controls can be classified as passive (e.g., trenches, fences, organic mulch, particle films, inert dusts, and oils), active (e.g., mechanical, polishing, pneumatic, impact, and thermal), and miscellaneous (e.g., cold storage, heated air, flaming, hot-water immersion). Some physical methods such as oils have been used successfully for preharvest treatments for decades. Another recently developed method for preharvest situations is particle films. As we move from production to the consumer, legal constraints restrict the number of options available. Consequently, several physical control methods are used in postharvest situations. Two noteworthy examples are the entoleter, an impacting machine used to crush all insect stages in flour, and hot-water immersion of mangoes, used to kill tephritid fruit fly immatures in fruit. The future of physical control methods will be influenced by sociolegal issues and by new developments in basic and applied research.
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    Annual Review of Entomology 48 (2003), S. 307-337 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Until the 1990s, Amblyomma americanum was regarded primarily as a nuisance species, but a tick of minor importance as a vector of zoonotic pathogens affecting humans. With the recent discoveries of Ehrlichia chaffeensis, Ehrlichia ewingii, and "Borrelia lonestari," the public health relevance of lone star ticks is no longer in question. During the next 25 years, the number of cases of human disease caused by A. americanum-associated pathogens will probably increase. Based on current trajectories and historic precedents, the increase will be primarily driven by biological and environmental factors that alter the geographic distribution and intensity of transmission of zoonotic pathogens. Sociologic and demographic changes that influence the likelihood of highly susceptible humans coming into contact with infected lone star ticks, in addition to advances in diagnostic capabilities and national surveillance efforts, will also contribute to the anticipated increase in the number of recognized cases of disease.
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  • 83
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    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
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    Notes: Abstract Controversy exists over ecological risks in classical biological control. We reviewed 10 projects with quantitative data on nontarget effects. Ten patterns emerged: (a) Relatives of the pest are most likely to be attacked; (b) host-specificity testing defines physiological host range, but not ecological range; (c) prediction of ecological consequences requires population data; (d) level of impact varied, often in relation to environmental conditions; (e) information on magnitude of nontarget impact is sparse; (f) attack on rare native species can accelerate their decline; (g) nontarget effects can be indirect; (h) agents disperse from agroecosystems; (i) whole assemblages of species can be perturbed; and (j) no evidence on adaptation is available in these cases. The review leads to six recommendations: Avoid using generalists or adventive species; expand host-specificity testing; incorporate more ecological information; consider ecological risk in target selection; prioritize agents; and pursue genetic data on adaptation. We conclude that retrospective analyses suggest clear ways to further increase future safety of biocontrol.
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    Annual Review of Entomology 48 (2003), S. 425-453 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Recent application of biochemical and molecular techniques to study the genesis of scolytid aggregation pheromones has revealed that bark beetles are primarily responsible for the endogenous synthesis of widely occurring pheromone components such as ipsenol, ipsdienol, and frontalin. Because many of the chemical signals are isoprenoids, the roles of the mevalonate biosynthetic pathway and the enzyme HMG-CoA reductase (HMG-R) have been investigated. This has led to the identification of endothelial cells in the anterior midgut as the site of synthesis and to the concept that de novo pheromone biosynthesis is regulated in part by the positive effect of juvenile hormone III (JHIII) on gene expression for HMG-R. Both the pronounced regulation by JHIII and the expression pattern of eukaryotic HMG-R argue against synthesis of these pheromones by prokaryotes. As the mevalonate pathway and its regulation have been studied in few other insects, broader issues addressed through the study of scolytid pheromone biosynthesis include major step versus coordinate regulation of the pathway and a genomics approach to elucidating the entire pathway and the mode of action of JHIII.
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    Annual Review of Entomology 48 (2003), S. 485-503 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract FMRFamide-related peptides (FaRPs) contain a C-terminal RFamide but unique N-terminal extensions. They are expressed throughout the animal kingdom and affect numerous biological activities. Like other animal species, Drosophila melanogaster contains multiple genes that encode different FaRPs. The ease of genetic manipulations, the availability of genomic sequence data, the existence of established bioassays, and its short lifespan make D. melanogaster a versatile experimental organism in which to investigate peptide processing, functions, and signal transduction pathways. Here, the structures, precursor organizations, distributions, and activities of FaRPs encoded by D. melanogaster FMRFamide (dFMRFamide), myosuppressin (Dms), and sulfakinin (Dsk) genes are reviewed, and predictions are made on their signaling pathways and biological functions.
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    Annual Review of Entomology 48 (2003), S. 521-547 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Investigations of plant-herbivore interactions continue to be popular; however, a bias neglecting root feeders may limit our ability to understand how herbivores shape plant life histories. Root feeders can cause dramatic plant population declines, often associated with secondary stress factors such as drought or grazing. These severe impacts resulted in substantial interest in root feeders as agricultural pests and increasingly as biological weed control agents, particularly in North America. Despite logistical difficulties, establishment rates in biocontrol programs are equal or exceed those of aboveground herbivores (67.2% for aboveground herbivores, 77.5% for belowground herbivores) and root feeders are more likely to contribute to control (53.7% versus 33.6%). Models predicting root feeders would be negatively affected by competitively superior aboveground herbivores may be limited to early successional habitats or generalist root feeders attacking annual plants. In later successional habitats, root feeders become more abundant and appear to be the more potent force in driving plant performance and plant community composition. Aboveground herbivores, even at high population levels, were unable to prevent buildup of root herbivore populations and the resulting population collapse of their host plants. Significant information gaps exist about the impact of root feeders on plant physiology and secondary chemistry and their importance in natural areas, particularly in the tropics.
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    Annual Review of Entomology 48 (2003), S. 549-577 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract The interactions of two economically important gall midge species, the rice gall midge and the Hessian fly, with their host plants, rice and wheat, respectively, are characterized by plant defense via R genes and insect adaptation via avr genes. The interaction of a third gall midge species, the orange wheat blossom midge, with wheat defense R genes has not yet exhibited insect adaptation. Because of the simple genetics underlying important aspects of these gall midge-grass interactions, a unique opportunity exists for integrating plant and insect molecular genetics with coevolutionary ecology. We present an overview of some genetic, physiological, behavioral, and ecological studies that will contribute to this integration and point to areas in need of study.
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    Annual Review of Entomology 48 (2003), S. 73-88 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract This review addresses the problems insects and ticks face to feed on blood and the solutions these invertebrates engender to overcome these obstacles, including a sophisticated salivary cocktail of potent pharmacologic compounds. Recent advances in transcriptome and proteome research allow an unprecedented insight into the complexity of these compounds, indicating that their molecular diversity as well as the diversity of their targets is still larger than previously thought.
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    Annual Review of Entomology 48 (2003), S. 89-110 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Nervous system function is entirely dependent on the intricate and precise pattern of connections made by individual neurons. Much of the insightful research into mechanisms underlying the development of this pattern of connections has been done in insect nervous systems. Studies of developmental mechanisms have revealed critical interactions between neurons and glia, the non-neuronal cells of the nervous system. Glial cells provide trophic support for neurons, act as struts for migrating neurons and growing axons, form boundaries that restrict neuritic growth, and have reciprocal interactions with neurons that govern specification of cell fate and axonal pathfinding. The molecular mechanisms underlying these interactions are beginning to be understood. Because many of the cellular and molecular mechanisms underlying neural development appear to be common across disparate insect species, and even between insects and vertebrates, studies in developing insect nervous systems are elucidating mechanisms likely to be of broad significance.
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    Annual Review of Entomology 48 (2003), S. 141-161 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Many of the most harmful parasitic diseases are transmitted by blood-feeding insect vectors. During this stage of their life cycles, selection pressures favor parasites that can manipulate their vectors to enhance transmission. Strategies may include increasing the amount of contact between vector and host, reducing vector reproductive output and consequently altering vector resource management to increase available nutrient reserves, and increasing vector longevity. Manipulation of these life-history traits may be more beneficial at some phase of the parasite's developmental process than at others. This review examines empirical, experimental, and field-based evidence to evaluate examples of changes in vector behavior and physiology that might be construed to be manipulative. Examples are mainly drawn from malaria-infected mosquitoes, Leishmania-infected sandflies, and Trypanosoma-infected tsetse flies.
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    Annual Review of Entomology 48 (2003), S. 185-209 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Birds host many lineages of symbiotic mites, but the greatest diversity is shown by the three superfamilies of astigmatan feather mites: Analgoidea, Pterolichoidea, and Freyanoidea. Members of this diphyletic grouping have colonized all parts of the avian integument from their ancestral nidicolous habitat. Whereas some clearly feed on feather pith or skin, acting as parasites, other feather mites are paraphages and consume feather oils without causing structural damage. Sexual dimorphism in feather mites is often extreme, and little is known of the function of many elaborate male structures. Abundance and location of vane-dwelling mites is affected by season, temperature, light, humidity, and host body condition. Because transmission between hosts usually depends on host body contact, it is unsurprising that feather mite phylogeny often parallels host phylogeny; however, recent cladistic analyses have also found evidence of host-jumping and "missing the boat" in several mite lineages.
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    Annual Review of Entomology 48 (2003), S. 235-260 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Genomics is the study of the structure and function of the genome: the set of genetic information encoded in the DNA of the nucleus and organelles of an organism. It is a dynamic field that combines traditional paths of inquiry with new approaches that would have been impossible without recent technological developments. Much of the recent focus has been on obtaining the sequence of entire genomes, determining the order and organization of the genes, and developing libraries that provide immediate physical access to any desired DNA fragment. This has enabled functional studies on a genome-wide level, including analysis of the genetic basis of complex traits, quantification of global patterns of gene expression, and systematic gene disruption projects. The successful contribution of genomics to problems in applied entomology requires the cooperation of the private and public sectors to build upon the knowledge derived from the Drosophila genome and effectively develop models for other insect Orders.
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    Annual Review of Entomology 48 (2003), S. 283-306 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Lacking a comprehensive fossil record, solitary representatives of the taxa, and/or a definitive phylogeny of closely related insects, comparison of the life history and social biology of basal, living groups is one of the few available options for developing inferences regarding the early eusocial evolution of ants and termites. Comparisons of a select group of basal formicid and isopteran taxa suggest that the reproductive organization of colonies and their patterns of division of labor were particularly influenced, in both groups, by nesting and feeding ecology. Opportunities for serial inheritance of the nest structure and colony population by kin may have been significant in the evolution of multiple reproductive forms and options. Disease has been a significant factor in the evolution of social organization in ants and termites, but the adaptive mechanisms of infection control differ. Evaluations of the convergent and divergent social biology of the two taxa can generate novel domains of research and testable hypotheses.
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    Annual Review of Entomology 48 (2003), S. 339-364 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Neonicotinoids, the most important new class of synthetic insecticides of the past three decades, are used to control sucking insects both on plants and on companion animals. Imidacloprid (the principal example), nitenpyram, acetamiprid, thiacloprid, thiamethoxam, and others act as agonists at the insect nicotinic acetylcholine receptor (nAChR). The botanical insecticide nicotine acts at the same target without the neonicotinoid level of effectiveness or safety. Fundamental differences between the nAChRs of insects and mammals confer remarkable selectivity for the neonicotinoids. Whereas ionized nicotine binds at an anionic subsite in the mammalian nAChR, the negatively tipped ("magic" nitro or cyano) neonicotinoids interact with a proposed unique subsite consisting of cationic amino acid residue(s) in the insect nAChR. Knowledge reviewed here of the functional architecture and molecular aspects of the insect and mammalian nAChRs and their neonicotinoid-binding site lays the foundation for continued development and use of this new class of safe and effective insecticides.
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    Annual Review of Entomology 48 (2003), S. 397-423 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract There are three major classes of insect genetic systems: those with diploid males (diplodiploidy), those with effectively haploid males (haplodiploidy), and those without males (thelytoky). Mixed systems, involving cyclic or facultative switching between thelytoky and either of the other systems, also occur. I present a classification of the genetic systems of insects and estimate the number of evolutionary transitions between them that have occurred. Obligate thelytoky has arisen from each of the other systems, and there is evidence that over 900 such origins have occurred. The number of origins of facultative thelytoky and the number of reversions from obligate thelytoky to facultative and cyclic thelytoky are difficult to estimate. The other transitions are few in number: five origins of cyclic thelytoky, eight origins of obligate haplodiploidy (including paternal genome elimination), the strange case of Micromalthus, and the two reversions from haplodiploidy to diplodiploidy in scale insects. Available evidence tends to support W.D. Hamilton's hypothesis that maternally transmitted endosymbionts have been involved in the origins of haplodiploidy. Bizarre systems of extrazygotic inheritance in Sternorrhyncha are not easily accommodated into any existing classification of genetic systems.
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    Annual Review of Entomology 48 (2003), S. 455-484 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Gustatory receptors associated with feeding in phytophagous insects are broadly categorized as phagostimulatory or deterrent. No phytophagous insect is known that tastes all its essential nutrients, and the ability to discriminate between nutrients is limited. The insects acquire a nutritional balance largely "adventitiously" because leaves have an appropriate chemical composition. Sugars are the most important phagostimulants. Plant secondary compounds are most often deterrent but stimulate phagostimulatory cells if they serve as host-indicating sign stimuli, or if they are sequestered for defense or used as pheromone precursors. The stimulating effects of chemicals are greatly affected by other chemicals in mixtures like those to which the sensilla are normally exposed. Host plant selection depends on the balance of phagostimulatory and deterrent inputs with, in some oligophagous and monophagous species, a dominating role of a host-related chemical. Evolution of phytophagy has probably involved a change in emphasis in the gustatory system, not fundamentally new developments. The precise role of the gustatory systems remains unclear. In grasshoppers, it probably governs food selection and the amounts eaten, but in caterpillars there is some evidence that central feedbacks are also involved in regulating the amount eaten.
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    Annual Review of Immunology 21 (2003), S. 29-70 
    ISSN: 0732-0582
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract CD8 T cells respond to viral infections but also participate in defense against bacterial and protozoal infections. In the last few years, as new methods to accurately quantify and characterize pathogen-specific CD8 T cells have become available, our understanding of in vivo T cell responses has increased dramatically. Pathogen-specific T cells, once thought to be quite rare following infection, are now known to be present at very high frequencies, particularly in peripheral, nonlymphoid tissues. With the ability to visualize in vivo CD8 T cell responses has come the recognition that T cell expansion is programmed and, to a great extent, independent of antigen concentrations. Comparison of CD8 T cell responses to different pathogens also highlights the intricate relationship between microbially induced innate inflammatory responses and the kinetics, magnitude, and character of long-term T cell responses. This review describes recent progress in some of the major murine models of CD8 T cell-mediated immunity to viral, bacterial, and protozoal infection.
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    Annual Review of Immunology 21 (2003), S. 139-176 
    ISSN: 0732-0582
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract A functional immune system requires the selection of T lymphocytes expressing receptors that are major histocompatibility complex restricted but tolerant to self-antigens. This selection occurs predominantly in the thymus, where lymphocyte precursors first assemble a surface receptor. In this review we summarize the current state of the field regarding the natural ligands and molecular factors required for positive and negative selection and discuss a model for how these disparate outcomes can be signaled via the same receptor. We also discuss emerging data on the selection of regulatory T cells. Such cells require a high-affinity interaction with self-antigens, yet differentiate into regulatory cells instead of being eliminated.
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    Annual Review of Immunology 21 (2003), S. 265-304 
    ISSN: 0732-0582
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract In the absence of antiretroviral treatment, HIV-1 establishes a chronic, progressive infection of the human immune system that invariably, over the course of years, leads to its destruction and fatal immunodeficiency. Paradoxically, while viral replication is extensive throughout the course of infection, deterioration of conventional measures of immunity is slow, including the characteristic loss of CD4+ T cells that is thought to play a key role in the development of immunodeficiency. This conundrum suggests that CD4+ T cell-directed viral cytopathicity alone cannot explain the course of disease. Indeed, recent advances now indicate that HIV-1 pathogenesis is likely to result from a complex interplay between the virus and the immune system, particularly the mechanisms responsible for T cell homeostasis and regeneration. We review these data and present a model of HIV-1 pathogenesis in which the protracted loss of CD4+ T cells results from early viral destruction of selected memory T cell populations, followed by a combination of profound increases in overall memory T cell turnover, damage to the thymus and other lymphoid tissues, and physiological limitations in peripheral CD4+ T cell renewal.
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    Annual Review of Immunology 21 (2003), S. 425-456 
    ISSN: 0732-0582
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract IL-13 was first recognized for its effects on B cells and monocytes, where it upregulated class II expression, promoted IgE class switching and inhibited inflammatory cytokine production. It was also thought to be functionally redundant with IL-4. However, studies conducted with knockout mice, neutralizing antibodies, and novel antagonists demonstrate that IL-13 possesses several unique effector functions that distinguish it from IL-4. Resistance to most gastrointestinal nematodes is mediated by type-2 cytokine responses, in which IL-13 plays a dominant role. By regulating cell-mediated immunity, IL-13 modulates resistance to intracellular organisms including Leishmania major, Leishmania mexicana, and Listeria monocytogenes. In the lung, IL-13 is the central mediator of allergic asthma, where it regulates eosinophilic inflammation, mucus secretion, and airway hyperresponsiveness. Manipulation of IL-13 effector function may also prove useful in the treatment of some cancers like B-cell chronic lymphocytic leukemia and Hodgkin's disease, where IL-13 modulates apoptosis or tumor cell growth. IL-13 can also inhibit tumor immunosurveillance. As such, inhibitors of IL-13 might be effective as cancer immunotherapeutics by boosting type-1-associated anti-tumor defenses. Finally, IL-13 was revealed as a potent mediator of tissue fibrosis in both schistosomiasis and asthma, which indicates that it is a key regulator of the extracellular matrix. The mechanisms that regulate IL-13 production and/or function have also been investigated, and IL-4, IL-12, IL-18, IFN-gamma, IL-10, TGF-beta, TNF-alpha, and the IL-4/IL-13 receptor complex play important roles. This review highlights the effector functions of IL-13 and describes multiple pathways for modulating its activity in vivo.
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