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  • 1
    Electronic Resource
    Electronic Resource
    Studies of local structure of Cm3+ in borosilicate glass using laser and x-ray spectroscopic methods and computational modeling (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1489-1496 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The local environment of Cm3+ in a borosilicate glass has been probed by a combination of laser spectroscopy, structural modeling, and extended x-ray absorption fine structure (EXAFS) spectroscopy. The Stark splitting for the Cm f–f state transitions is significantly larger than the inhomogeneous line broadening that results from the disordered environment. As a result, the Cm optical spectrum can be fit using an effective operator Hamiltonian to obtain a set of crystal-field parameters. The fitting procedure, which requires the use of a descent-in-symmetry approach, provides a set of parameters for a best fit within tetragonal symmetry. These parameters are then linked to the local environment of Cm through exchange-charge modeling (ECM) of crystal field interactions. Cm in our borosilicate glass is best modeled with six oxygen ions with approximately tetragonal symmetry, and at an average distance of 2.31 (3) Å. The results of crystal-field modeling are supported by EXAFS results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480687
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  • 2
    Electronic Resource
    Electronic Resource
    Anaesthetic machine checklists 1 (2001)
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 56 (2001), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.2001.2279-6.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effusive-flow characterization of arbitrary size and geometry target/vapor transport systems: RIB applications : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 786-788 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The principal factors that limit intensities of short-lived radioactive ion beams produced by the isotope separator on-line technique are time delays due to diffusion of radioactive species from solid or liquid target materials and their effusive-flow transport to the ion source. Although diffusion times can be reduced by proper design of short diffusion length, highly refractory targets, effusive-flow times are more difficult to assess. After diffusion from the target material, the species must travel through the target material and vapor transport system to the ion source. The time required for effusive-flow transport to the ion source depends on the conduction path, chemical reactions between the species and target material and materials of construction, as well as the physical size and geometry of the transport system. We have developed a fast valve (0.1 ms closing time) for introducing gaseous or vapor-state species into the target/vapor transport/ion source/system that permits measurement of effusive-flow times for any gaseous or vaporous species (chemically active or chemically inactive) through any vapor transport system, independent of size and geometry. Characteristic times are determined from the exponential decay of the momentum analyzed ion beam intensity for the species during effusive flow through the vapor transport system under evaluation. This article describes the effusive-flow apparatus and presents characteristic time spectra and characteristic effusive-flow time data for noble gases flowing through a serial-flow target reservoir system. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430868
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  • 4
    Electronic Resource
    Electronic Resource
    Electron tunneling detected by electrostatic force (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3615-3617 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method is introduced for measuring the tunneling of electrons between a specially fabricated scanning probe microscope tip and a surface. The technique is based upon electrostatic force detection of charge as it is transferred to and from a small (10−17 F) electrically isolated metallic dot on the scanning probe tip. The methods for dot fabrication, charging, and discharging are described and electron tunneling to a sample surface is demonstrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1330568
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  • 5
    Electronic Resource
    Electronic Resource
    Retroelements contribute to the excess low-copy-number DNA in pine (2000)
    Springer
    Molecular genetics and genomics 264 (2000), S. 47-55 
    Details
    ISSN: 1617-4623
    Keywords: Genome organization Reassociation kinetics Retroelements Gymnosperms Pinus taeda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Excess DNA in the single-copy component is rarely recognized as a contributor to the C-value paradox yet the single-copy component of the pine genome is reported to comprise over 3000 Mb of DNA, in large excess over the estimated 100 Mb required for gene expression. Two hypotheses regarding the factors that might contribute to the excess low-copy-number DNA were tested. The first hypothesis proposes that the excess low-copy kinetic component is actually overestimated by reassociation data analysis. To test this, a previously published C0t curve for Pinus strobus was reanalyzed using a new estimate of genome size based on laser flow cytometry. Part of the excess low-copy-number DNA in the pine genome could be attributed to the choice of parameters used in the analysis of the reassociation data. The second hypothesis holds that diverged retrotransposons contribute to the excess low-copy DNA. Sequences randomly sampled from single-copy and low-repetitive kinetic components of the P. taeda genome were characterized. Twelve of 46 fragments cloned from these fractions were found to show sequence similarity to retroelements; hence diverged retroelements contribute to the excess low-repetitive kinetic component in the pine genome. Similarity search was shown to be a conservative method for identifying retroelements, and thus the number of retroelements in the low-copy component was actually underestimated. Most of the retroelements in this fraction were nonfunctional, divergent from known retroelement families and previously reported only for flowering plants. Divergent retrotransposons are thus a major factor contributing to the expansion of the low-repetitive DNA component in higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000279
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  • 6
    Electronic Resource
    Electronic Resource
    Endomorphins: Localization, release and action on rat dorsal horn neurons (2000)
    Springer
    Journal of biomedical science 7 (2000), S. 213-220 
    Details
    ISSN: 1423-0127
    Keywords: μ-Opiate receptors ; Excitatory postsynaptic currents ; Inhibitory postsynaptic currents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Endomorphin (Endo) 1 and 2, two tetrapeptides isolated from the bovine and human brain, have been proposed to be the endogenous ligand for the μ-opiate receptor. A multi-disciplinary study was undertaken to address the issues of localization, release and biological action of Endo with respect to the rat dorsal horn. First, immunohistochemical studies showed that Endo-1- or Endo-2-like immunoreactivity (Endo-1- or Endo-2-LI) is selectively expressed in fiber-like elements occupying the superficial layers of the rat dorsal horn, which also exhibit a high level of μ-opiate receptor immunoreactivity. Second, release of immunoreactive Endo-2-like substances (irEndo) from the in vitro rat spinal cords upon electrical stimulation of dorsal root afferent fibers was detected by the immobilized antibody microprobe technique. The site of release corresponded to laminae I and II where the highest density of Endo-2-LI fibers was localized. Lastly, whole-cell patch clamp recordings from substantia gelatinosa (SG) neurons of rat lumbar spinal cord slices revealed two distinct actions of exogenous Endo-1 and Endo-2: (1) depression of excitatory and/or inhibitory postsynaptic potentials evoked by stimulation of dorsal root entry zone, and (2) hyperpolarization of SG neurons. These two effects were prevented by the selective μ-opiate receptor antagonist β-funaltrexamine. The localization of endomorphin-positive fibers in superficial layers of the dorsal horn and the release of irEndo upon stimulation of dorsal root afferents together with the observation that Endo inhibits the activity of SG neurons by interacting with μ-opiate receptors provide additional support of a role of Endo as the endogenous ligand for the μ-opiate receptor in the rat dorsal horn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255468
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  • 7
    Electronic Resource
    Electronic Resource
    Ice Shelf Microbial Ecosystems in the High Arctic and Implications for Life on Snowball Earth (2000)
    Springer
    Naturwissenschaften 87 (2000), S. 137-141 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract  The Ward Hunt Ice Shelf (83°N, 74°W) is the largest remaining section of thick (〉10 m) landfast sea ice along the northern coastline of Ellesmere Island, Canada. Extensive meltwater lakes and streams occur on the surface of the ice and are colonized by photosynthetic microbial mat communities. This High Arctic cryo-ecosystem is similar in several of its physical, biological and geochemical features to the McMurdo Ice Shelf in Antarctica. The ice-mats in both polar regions are dominated by filamentous cyanobacteria but also contain diatoms, chlorophytes, flagellates, ciliates, nematodes, tardigrades and rotifers. The luxuriant Ward Hunt consortia also contain high concentrations (107–108 cm–2) of viruses and heterotrophic bacteria. During periods of extensive ice cover, such as glaciations during the Proterozoic, cryotolerant mats of the type now found in these polar ice shelf ecosystems would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001140050692
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  • 8
    Electronic Resource
    Electronic Resource
    Predicting age-age genetic correlations in tree-breeding programs: a case study of Pinus taeda L. (2000)
    Springer
    Theoretical and applied genetics 100 (2000), S. 199-206 
    Details
    ISSN: 1432-2242
    Keywords: Key words Age-age genetic correlations ; Phenotypic correlations ; Conifers ; Tree breeding ; Woody perennials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A meta-analysis of 520 parents and 51,439 individuals was used to develop two equations for predicting age-age genetic correlations in Pinus taeda L. Genetic and phenotypic family mean correlations and heritabilities were estimated for ages ranging from 2 to 25 years on 31 sites in the southern U.S. and Zimbabwe. Equations for predicting age-age correlations based on P. taeda populations from west and east of the Mississippi River proved statistically different. Both predictive equations proved conservative for validation datasets consisting of younger tests in the U.S. and Zimbabwe. Age-dependent log-linear predictive equations were favored over growth-dependent equations. All P. taeda predictive equations based on genetic correlations favored earlier selection when compared to a generalized conifer predictive equation based on phenotypic correlations. The age-age correlations structure showed stability independent of planting density and across a wide range of family sizes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050027
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  • 9
    Electronic Resource
    Electronic Resource
    Thermogravimetric Evidence of Nickel or Copper Isomorphously Substituted into a Zeolite (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 329-338 
    Details
    ISSN: 1572-8943
    Keywords: copper ; fluoride ; isomorphous substitution ; nickel ; ZSM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis of pure silica ZSM-5 has been modified to produce highly crystalline material in the protonated form, necessary for catalytic activity, directly from a low water fluoride gel. Tetrahedrally co-ordinated divalent species of nickel and copper have been synthesised as salts of large organic cations and increasing mole fractions incorporated into the zeolite gels. The products have been analysed and characterised using simultaneous thermogravimetric and derivative thermogravimetric analysis (TG-DTG). The thermal decomposition under nitrogen of the metal associated cations, tetraethylammonium (TEA+), occluded within the zeolite channels is indicative and characteristic of the incorporation of heteroatoms into the zeolite framework. Anomalous losses in the systems can be explained by Jahn–Teller distortions. The mass losses increased with increased metal loading and were consistent with those reported in full water system, analysis also confirmed that the material was hydrophobic and thermally stable. Analysis by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR) and Atomic Absorption Spectroscopy (AAS) has confirmed the reliability of TG-DTG as a diagnostic tool. The maximum levels of substitution achieved were (mass%) Ni 3.93 and Cu 4.38.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010133822423
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  • 10
    Electronic Resource
    Electronic Resource
    QUOROM – another step forwards (2000)
    Springer
    Annals of oncology 11 (2000), S. 921-922 
    Details
    ISSN: 1569-8041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008330316212
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