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  • 1
    Digitale Medien
    Digitale Medien
    A rheometer for the measurement of a high shear modulus covering more than seven decades of frequency below 50 kHz (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5019-5031 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new rheometer is described. It consists of a transducer unit supplied with an electric impedance analyzing unit. The transducer unit converts a mechanical impedance into an electrical impedance by the piezoelectric effect. A detailed quantitative analysis of the interaction between the sample and the transducer is given. The real and imaginary parts of the shear modulus of a viscoelastic sample can be found in the frequency range of 1 mHz–50 kHz, modulus range of 0.1 MPa–10 GPa, and the temperature range of 150–300 K. The sample volume is 0.3 cm3 and the strain amplitude is exceedingly small. The small size of the transducer allows for good temperature control and equilibration. It has a simple construction based on inexpensive components. Results on the supercooled liquid 2-metyl-2,4-pentandiol at the glass transition obtained by the method are included. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1146126
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  • 2
    Digitale Medien
    Digitale Medien
    Determination of Nonvolatile Organic Carbon in Aquifer Solids After Carbonate Removal by Sulfurous Acid (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 35 (1997), S. 0 
    Details
    ISSN: 1745-6584
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Energietechnik , Geologie und Paläontologie
    Notizen: The precise determination of total organic carbon (TOC) in aquifer materials is important in the estimation of retardation coefficients for organic compound transport. Commonly used methods for TOC determination after carbonate removal by acidification include: weight loss on ignition of solids at 550° C, acid-dichromate oxidation, and combustion at 800–950° C. Since carbonate carbon frequently is more abundant than organic carbon all TOC methods depend on efficient and complete carbonate removal prior to the TOC quantification step. A method for the determination of TOC in aquifer solids involving carbonate removal by 0.73 M sulfurous acid and subsequent combustion at 800° C was tested on solids from three aquifers and on mineral standards. The carbon quantification by combustion and infrared detection of CO2 was accurate at solid organic carbon contents between 30 and 10,000 μgC/g. The acid treatment added small amounts of carbon to the sample, and siderite removal was incomplete. For samples without siderite or dolomite, the accuracy of TOC determinations was enhanced by grinding the solids. Measurement of very low TOC contents (50–100 /μgC/g) requires supplementary testing of grinding and acid treatment effects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1745-6584.1997.tb00053.x
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  • 3
    Digitale Medien
    Digitale Medien
    Changes in trace metal species and other components of the rhizosphere during growth of radish (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Changes in the properties of soil solution in the rhizosphere of developing radish plants were investigated. Variations in these properties were expected to affect the distribution and speciation of metals in the soil and soil solution. Applications of essential nutrients were linked to plant transpiration rates and prevented excess addition of nutrient ions, so that subtle changes in soil solution composition would not be obscured. Soil solution pH, the concentration of dissolved organic carbon (DOC) and the concentrations of major and trace elements in solution were found to vary over time. Strict control of fertilizer additions led to the maintenance of a relatively low ionic strength in the soil solution, and under such conditions trace metal solubility appeared to be highy influenced by the concentration of DOC. A chemical speciation analysis was performed which showed that, while dissolved Cd and Zn were largely uncomplexed in unplanted soil, Cd and Zn in the rhizosphere existed mainly as complexed forms. It is hypothesized that this is partly a result of Ca-metal-ligand equilibrium in solution, with higher Ca concentrations in unplanted soil leading to more of the Cd and Zn in solution existing in the uncomplexed state. Changes in the concentrations of uncomplexed Cd and Zn with time gave the best correlations with changes in plant uptake of these metals over time, supporting the hypothesis that plants mainly absorb the free metal ion from soil solution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00577.x
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  • 4
    Digitale Medien
    Digitale Medien
    A Putative New Retrovirus Associated with Multiple Sclerosis and the Possible Involvement of Epstein-Barr Virus in This Disease (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 724 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb38903.x
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  • 5
    Digitale Medien
    Digitale Medien
    Local interneurons and information processing in the olfactory glomeruli of the moth Manduca sexta (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 385-399 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Inhibition ; Local interneurons ; Manduca sexta ; Olfaction ; Synaptic interactions ; Antennal lobe
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Intracellular recordings were made from the major neurites of local interneurons in the moth antennal lobe. Antennal nerve stimulation evoked 3 patterns of postsynaptic activity: (i) a short-latency compound excitatory postsynaptic potential that, based on electrical stimulation of the antennal nerve and stimulation of the antenna with odors, represents a monosynaptic input from olfactory afferent axons (71 out of 86 neurons), (ii) a delayed activation of firing in response to both electrical- and odor-driven input (11 neurons), and (iii) a delayed membrane hyperpolarization in response to antennal nerve input (4 neurons). Simultaneous intracellular recordings from a local interneuron with short-latency responses and a projection (output) neuron revealed unidirectional synaptic interactions between these two cell types. In 20% of the 30 pairs studied, spontaneous and current-induced spiking activity in a local interneuron correlated with hyperpolarization and suppression of firing in a projection neuron. No evidence for recurrent or feedback inhibition of projection neurons was found. Furthermore, suppression of firing in an inhibitory local interneuron led to an increase in firing in the normally quiescent projection neuron, suggesting that a disinhibitory pathway may mediate excitation in projection neurons. This is the first direct evidence of an inhibitory role for local interneurons in olfactory information processing in insects. Through different types of multisynaptic interactions with projection neurons, local interneurons help to generate and shape the output from olfactory glomeruli in the antennal lobe.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00193512
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  • 6
    Digitale Medien
    Digitale Medien
    Chemical communication in heliothine moths (1995)
    Springer
    Journal of comparative physiology 177 (1995), S. 545-557 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Interneuron ; Odor coding ; Olfaction ; Pheromone ; Tobacco budworm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The chemical and temporal features of the sex-pheromone emitted by Heliothis virescens females are encoded by a diverse array of output pathways from the male-specific macroglomerular complex (MGC) in the antennal lobe. Most output neurons (29 out of 32) were activated by antennal stimulation with the principal component of the sex-pheromone blend of this species, (Z)-11-hexadecenal. Six neurons were excited solely by this component, 8 neurons also responded to the second essential blend component, (Z)-9-tetradecenal, and 14 neurons displayed equivalent responses to the two. Many neurons also effectively encoded the onset and duration of the stimulus. In one additional neuron, a prolonged excitatory response (synergism) was evoked only by the blend of the two components, indicating that some MGC neurons function as ‘blend detectors’. In contrast to the situation in Helicoverpa zea, none of the MGC neurons in H. virescens responded selectively to (Z)-9-tetradecenal, suggesting that these two noctuid species employ different neural strategies to encode information about their respective pheromone blends. Three MGC-output neurons responded selectively to (Z)-11-hexadecenyl acetate, an odorant released by some sympatric species that disrupts normal upwind flight to pheromones. Thus, changes in the attractant and deterrent chemical signals, as well as the physical features of these odor plumes, are encoded in the MGC across a diverse parallel array of output pathways to the protocerebrum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00207184
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  • 7
    Digitale Medien
    Digitale Medien
    Structure and function of antennal lobe neurons in the male turnip moth, Agrotis segetum (Lepidoptera: Noctuidae) (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 547-562 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Olfaction ; Moth ; Pheromone ; Intracellular morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Interneurons with dendritic branches in the antennal lobe of the male turnip moth, Agrotis segetum (Schiff., Lepidoptera: Noctuidae), were investigated with intracellular recording and staining methods. Seventeen projection neurons that transmit information from the antennal lobe to higher centers in the brain displayed dendritic arbors in the male specific macroglomerular complex (MGC) and responded to chemical components of the female sex pheromone used in species-specific sexual communication. Most of the projection neurons responded to several of the pheromone components tested, and a precise correlation between the location of the dendritic arborization and the physiological response could not be demonstrated. One MGC-projection neuron fit the definition of “blend specialist”. It did not respond to the individual components of the behaviorally active pheromone blend, but showed a strong response to the components when combined in the species-specific blend. Some of the projection neurons also showed clear responses to phenylacetaldehyde, a flower-produced compound and/or to (E)-2-hexenal, a common green-leaf volatile. In eight neurons, the axonal projection could be followed to the calyces of the mushroom body, and subsequently to the inferior lateral protocerebrum. Four local interneurons were characterized both morphologically and physiologically. Each neuron arborized extensively throughout the antennal lobe, and each responded to one or several of the pheromone compounds, and/or to one or both of the plant-produced compounds. One of the local interneurons responded exclusively to the pheromone blend, but not to the individual components.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00199476
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  • 8
    Digitale Medien
    Digitale Medien
    Investigation of fusion reactions in palladium and titanium tritide using galvanostatic, coulometric, and hydrogen permeation techniques (1990)
    Springer
    Journal of fusion energy 9 (1990), S. 299-304 
    Details
    ISSN: 1572-9591
    Schlagwort(e): Hydrogen-permeation techniques ; coulometric techniques ; hydrogen ; palladium ratio ; hydrogen absorption efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract We describe several electrochemical methods used to investigate the possibility of cold fusion phenomena in palladium and titanium tritide cathodes. We performed long-term (up to 77 days) electrolysis experiments with electrochemical cells of the University of Utah type at current densities as high as 1 A/cm2, while monitoring neutron and tritium levels. With some cells, we pulsed the current to determine if neutron bursts would result. In another cell, we used titanium tritide as the cathode to determine if D-T reactions yielding neutrons would occur. In no instance were levels of neutrons or tritium significantly above background except in the titanium tritide cell where isotopic exchange, occcurring between the electrode and the electrolyte, resulted in significant tritium levels. We also combined x-ray photoelectron spectroscopy (XPS) and electrochemical hydrogen permeation experiments to determine the effectiveness of various Pd surface treatment procedures on the resultant electrochemical hydrogen absorption efficiency. Electroanalytical and thermal desorption/gas analysis techniques indicated the maximum loading of H in Pd was to a ratio of H∶Pd=0.8.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01059246
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  • 9
    Digitale Medien
    Digitale Medien
    Effect of geochemical conditions on fate of organic compounds in groundwater (1996)
    Springer
    Environmental geology 27 (1996), S. 335-346 
    Details
    ISSN: 1432-0495
    Schlagwort(e): Organic compounds ; Groundwater
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract In situ microcosms were successfully used to study the degradation of a range of organic compounds in two pristine aquifers, one aerobic (Vejen) and one anaerobic (Villa Farm). Degradation and sorption behavior in the laboratory column microcosms packed with Villa Farm sediment was very similar to that in the in situ microcosms. However, when the columns were packed with quartz and equilibrated with aerated Villa Farm groundwater, behavior mirrored that at Vejen, indicating that oxygen rather than sediment or groundwater composition was the critical parameter. The aromatic and polyaromatic compounds (benzene, toluene,o-xylene, naphthalene) degraded under aerobic conditions only. The organochlorine compounds (trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,4-dichlorobenzene and 1,2-dichlorobenzene) showed little or no sign of degradation either aerobically or anaerobically. Interpretation of the data was complicated by strong sorption to the Villa Farm sediment but tetrachloromethane, nitrobenzene, ando-nitrophenol appeared to degrade under anaerobic conditions only. Phenol degraded rapidly under both sets of conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00766703
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  • 10
    Digitale Medien
    Digitale Medien
    Intrapulmonary Drug Delivery of Salmon Calcitonin (1997)
    Springer
    Calcified tissue international 61 (1997), S. 345-347 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Key words: Osteoporosis, Hypercalcemia, Anti-resorptive
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: SUMMARY Calcitonin (CT) and other bone-active peptides have been restrained in clinical use by the need for parenteral administration. Although nasal and other transmucosal routes can be used for CT treatment, bioavailability and bioactivity of the peptide thus delivered are limited. We have evaluated the intrapulmonary route (IP) for the delivery of salmon calcitonin (SCT) in normal subjects. SCT was administered with a dry powder delivery inhaler. For comparison, each subject also received intramuscular (IM) SCT. Inhaled SCT produced significant hypocalcemia in all subjects as did injected SCT, and the peptide could be readily measured in serum by immunoassay. Compared by dose, IP SCT had 66% of the bioactivity and 28% of the bioavailability of IM SCT. This intrapulmonary route of administration should enhance the clinical acceptability of SCT and could also be applicable to other bone-active peptides.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002239900345
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