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  • Springer  (44)
  • Cell Press  (26)
  • Blackwell Publishing Ltd  (6)
  • 2000-2004  (76)
  • 1
    Electronic Resource
    Electronic Resource
    Enantioselective hydrogenation of pyruvate esters in the mesoporous environment of Pt-MCM-41 (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 351-357 
    Details
    ISSN: 1572-9028
    Keywords: enantioselective hydrogenation ; platinum ; cinchonidine ; catalyst modifier ; pyruvate hydrogenation ; MCM-41 ; Pt-MCM-41 preparation ; Pt-MCM-41 characterisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pt-MCM-41 catalysts having loadings of up to 2% Pt have been synthesised using three strategies: (i) direct synthesis from a Pt2+-containing gel, (ii) exchange of Na+ in Al-MCM-41 (containing 8% aluminium) for Pt2+, (iii) exchange of H+ in H-MCM-41 (containing 1% aluminium) for Pt2+. HRTEM confirmed the retention of the mesoporous structure in the active catalysts and gave information on Pt particle size and location. 27Al NMR provided information on the movement of aluminium within the structure during catalyst preparation. Enantioselective hydrogenation of methyl and ethyl pyruvate was catalysed by cinchonidine-modified Pt-MCM-41 at 293 K and elevated hydrogen pressures; performance was compared to that provided by the standard reference catalyst EUROPT-1. Catalysts prepared by strategies (i) and (ii) performed best, giving values of the enantiomeric excess comparable to those afforded by EUROPT-1 at rates moderated by an order of magnitude by mass transfer effects. Performance was impaired when Pt particle size in the mesopores was so small that conditions favoured racemic reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1027215007012
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  • 2
    Electronic Resource
    Electronic Resource
    The protective effects of hypoxia-induced hypometabolism in the Nautilus (2000)
    Springer
    Journal of comparative physiology 170 (2000), S. 261-268 
    Details
    ISSN: 1432-136X
    Keywords: Key words Nautilus ; Hypometabolism Hypoxia ; Blood gases ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Specimens of Nautilus pompilius were trapped at depths of 225–300 m off the sunken barrier reef south-east of Port Moresby, Papua New Guinea. Animals transported to the Motupore Island laboratory were acclimated to normal habitat temperatures of 18 °C and then cannulated for arterial and venous blood sampling. When animals were forced to undergo a period of progressive hypoxia eventually to encounter ambient partial pressure of oxygen (PO2) levels of ∼10 mmHg (and corresponding arterial PO2's of ∼5 mmHg), they responded by lowering their aerobic metabolic rates to 5–10% of those seen in resting normoxic animals. Coincident with this profound metabolic suppression was an overall decrease in activity, with brief periods of jet propulsion punctuating long periods of rest. Below ambient PO2 levels of 30–40 mmHg, ventilatory movements became highly periodic and at the lowest PO2 levels encountered, ventilation occasionally ceased altogether. Cardiac output estimated by the Fick equation decreased during progressive hypoxia by as much as 75–80%, and in the deepest hypometabolic states heart rates slowed to one to two cycles of very low amplitude per minute. By the end of 500 min exposure to ambient PO2 levels of 10 mmHg or less, the anaerobic end products octopine and succinate had increased significantly in adductor muscle and heart, respectively. Increased concentrations of octopine in adductor muscle apparently contributed to a small intracellular acidosis and to the development of a combined respiratory and metabolic acidosis in the extracellular compartment. On the other hand, increases in succinate in heart muscle occurred in the absence of any change in cardiac pHi. Taken together, we estimate that these anaerobic end products would make up less than 2% of the energy deficit arising from the decrease in aerobic metabolism. Thus, metabolic suppression is combined with a massive downregulation of systemic O2 delivery to match metabolic supply to demand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600000096
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  • 3
    Electronic Resource
    Electronic Resource
    AERIAL VIDEOGRAMMETRY FROM A TETHERED AIRSHIP TO ASSESS MANATEE LIFE-STAGE STRUCTURE (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 16 (2000), S. 0 
    Details
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Aerial videogrammetry from an airship tethered to a boat was used to assess the life-stage structure of manatees in the Blue Waters area of the Homosassa River on the west coast of central Florida. Individual frames of videos were loaded onto a computer and lengths of manatees measured using graphics software. All images of manatees were measured independently by three observers. Measurements were transformed to total manatee lengths by calculating the ratio between the measurements of a reference object of known length and the measurement of the manatee. Length estimates were highly variable but were unbiased with respect to observer. Results of an analysis of variance suggested that the hypothesis that lengths differed among days and among observers should not be rejected. Life-stage structures were represented in three schemes. One scheme-which included four life stages: dependent calves, juveniles, animals in tramsition between juvenile and adult, and adults-was included to provide the most information without sacrificing confidence in the life-stage distribution. Overall, the video system was effective at capturing images of manatees for life-stage characterization and, with improvements in image resolution, could become a valuable tool for photo-identification in sight-resight experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1748-7692.2000.tb00955.x
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  • 4
    Electronic Resource
    Electronic Resource
    HIGH PERFORMANCE TURNING CAPABILITIES DURING FORAGING BY BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 20 (2004), S. 0 
    Details
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Large predators should have difficulty catching small prey because small animals demonstrate greater maneuverability and agility compared to large animals. The ability of a predator to capture small prey indicates locomotor strategies to compensate for inequities in maneuverability. Bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida feed on fish at least one order of magnitude smaller than themselves. To examine the locomotor strategies involved in prey capture, the foraging movements of these dolphins were videotaped from overhead using a remotely-controlled camera suspended from a helium-filled aerostat, which was tethered to an observation vessel. Dolphins were observed to rapidly maneuver during chases of fish in open water or around patches of rooted vegetation. Video analysis of the chase sequences indicated that the dolphins could move the rostrum through small radius turns with a mean value of 0.20 body lengths and with a minimum value of 0.08 body lengths. Mean rate of turn was 561.6°/sec with a maximum rate measured at 1,372.0°/sec. High turning rates with small turning radii were primarily the result of maneuvers in which the dolphin rolled 90° and rapidly flexed its body ventrally. The ability of dolphins to change body orientation in multiple rotational axes provides a mechanism to reduce turning radius and increase turning rate to catch small, elusive prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1748-7692.2004.tb01175.x
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  • 5
    Electronic Resource
    Electronic Resource
    SHORT-TERM EFFECTS OF BOAT TRAFFIC ON BOTTLENOSE DOLPHINS, TURSIOPS TRUNCATUS, IN SARASOTA BAY, FLORIDA (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 17 (2001), S. 0 
    Details
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Coastal cetaceans are subject to potential injury or disturbance from vessels. In Sarasota, Florida, where about 120 resident bottlenose dolphins, Tursiops truncatus, share the inshore waters with over 34,000 registered boats, disturbance potential is high. We assessed specific behavioral responses of individual dolphins to boat traffic. We conducted focal animal behavioral observations during opportunistic and experimental boat approaches involving 33 well-known identifiable individual bottlenose dolphins. Dolphins had longer interbreath intervals (IBI) during boat approaches compared to control periods (no boats within 100 m). Treatment IBI length was inversely correlated with distance to the nearest boat in opportunistic observations. During 58 experimental approaches to 18 individuals, a video system suspended from a tethered airship was used to observe subsurface responses of focal dolphins as boats under our control, operating at specified speeds, were directed near dolphins. Dolphins decreased interanimal distance, changed heading, and increased swimming speed significantly more often in response to an approaching vessel than during control periods. Probability of change for both interanimal distance and heading increased when dolphins were approached while in shallow water. Our findings provide additional support for the need to consider disturbance in management plans for cetacean conservation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1748-7692.2001.tb01292.x
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  • 6
    Electronic Resource
    Electronic Resource
    A PLATFORM FOR CONTINUOUS BEHAVIORAL AND ACOUSTIC OBSERVATION OF FREE-RANGING MARINE MAMMALS: OVERHEAD VIDEO COMBINED WITH UNDERWATER AUDIO (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 17 (2001), S. 0 
    Details
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1748-7692.2001.tb00992.x
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  • 7
    Electronic Resource
    Electronic Resource
    FOREST GROWTH IMPACT ON PEAK SNOW PACK MEASUREMENTS AT LONG TERM SNOW COURSES (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 40 (2004), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Snow course surveys in late winter provide stream-flow forecasters with their best information for making water supply and flood forecasts for the subsequent spring and summer runoff period in mountainous regions of western North America. Snow survey data analyses are generally based on a 30-year “normal” period. It is well documented that forest cover changes over time will affect snow accumulation on the ground within forests. This paper seeks to determine if forest cover changes over decades at long term snow courses decrease measured peak snow water equivalent (SWE) enough to affect runoff prediction. Annual peak SWE records were analyzed at four snow courses in two different forest types having at least 25 years of snowpack data to detect any decreases in SWE due to forest growth. No statistically significant decreases in annual peak SWE over time were found at any of these four snow courses. The wide range of annual winter precipitation and correspondingly highly variable peak snowpack accumulation, as well as many other weather and site variables, masked any minor trends in the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.2004.tb01044.x
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  • 8
    Electronic Resource
    Electronic Resource
    Prevention of lethal respiratory vaccinia infections in mice with interferon-α and interferon-γ (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 40 (2004), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The antiviral efficacy of interferons (IFNs) was evaluated using a vaccinia intranasal infection model in mice in this study. We provide evidence that intranasal administration of IFN-α and IFN-γ (days −1 to +3) resulted in 100 and 90% survival against a lethal respiratory vaccinia infection (8 LD50) in mice, respectively; whereas no animals in the placebo group survived through the study period (21 days). The IFN treatment consisted of a single daily dose of 5×103 U per mouse for 5 consecutive days. The efficacy of IFN-γ was evident even when the IFN-γ treatments started 1–2 days after infection and when a lower dose (2×103 U per mouse) was used. The treatment of IFN-α and IFN-γ reduced the virus titers in the lungs of infected mice by 1000–10,000-fold, when the administration started 1 day after infection. Our data suggest that IFN-α and IFN-γ are effective in protecting vaccinia-infected mice from viral replication in lungs and mortality, and may be beneficial in other human orthopoxvirus infections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0928-8244(03)00358-4
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  • 9
    Electronic Resource
    Electronic Resource
    Synergic interactions in a urania–titania catalyst for isobutene partial oxidation (2000)
    Springer
    Catalysis letters 70 (2000), S. 183-186 
    Details
    ISSN: 1572-879X
    Keywords: uranium ; isobutene oxidation ; titania
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The partial oxidation of isobutene has been studied over titania-supported uranium oxide catalysts which exhibit a strong synergy between UOx and support phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018801804706
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  • 10
    Electronic Resource
    Electronic Resource
    Ions in Aqueous Acetic Acid Mixtures: Solvent Reorganization around Protons and Gibbs Energies of Transfer from Water (2000)
    Springer
    Journal of solution chemistry 29 (2000), S. 271-287 
    Details
    ISSN: 1572-8927
    Keywords: Ions ; solvent mixtures ; Gibbs energies of transfer ; acetic acid-water mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The photo-absorbing, basic sensor, 4-nitroaniline, has been used to determine theequilibrium constant for solvent reorganization around the proton in mixtures ofvarying composition of water with acetic acid. In all the mixtures used, theself-ionization of the acetic acid was suppressed. In contrast to mixtures of waterwith the related ethanol or acetone, this equilibrium is shifted more toward thewater-solvated species as the mole fraction x 2 of the cosolvent increases. TheGibbs energy of transfer of protons from water into the mixture ΔG o t (H+) can bederived with the aid of this equilibrium constant for the solvent reorganization.Using ΔG o t (H+), ΔG o t (i) for i denoting anions and other cations can be evaluated.In comparison the ΔG o t (i) for cations have lower negative values than when eitherethanol or acetone is added to water. Correspondingly, for halide anions, thepositive ΔG o t (i) with added acetic acid are rather less than is found with eitherethanol or acetone added. The influence on the ion-solvent interaction of bothelectron withdrawing hydroxy and carbonyl groups in acetic acid may beresponsible for this. Although ΔG o t (i) for C10− 4 and Re0− 4 are also positive, both picrateions and OH− give negative values with acetic acid added to water. With picrateions, the hydrophobic effect of the carbon ring produces stabilization in themixture relative to water. With OH−, complete conversion to acetate anionsoccurs. As is found with other cosolvents, the contribution of the charge onacetate anion to ΔG o t (CH3COO−) is found to increase as x 2 rises. The aciddissociation constant K a for acetic acid is found to decrease slowly as x 2 rises to0.5, followed by a rapid decrease for x 2 greater than 0.7 where dimerization ofacetic acid occurs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005102517584
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