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  • 1
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Auditory tuning curves of a small songbird, the great tit (Parus major), and of its principal avian predator, the European sparrowhawk (Accipiter nisus), were determined by an operant positive reinforcement conditioning procedure, using the method of constant stimuli. Thresholds were measured by the criterion of a 50% correct response and a d′ of 1.5 for intra- and interspecific comparison, respectively. The best frequency of both species was 2 kHz, the hawk being 6.5 dB SPL more sensitive than the tit. Although the high-frequency cutoff was very similar in both species, at 8 kHz the great tit was about 30 dB more sensitive than the sparrowhawk. The hearing abilities of the prey and its predator are discussed with reference to the acoustic alarm communication of great tits confronted with sparrowhawks. Two alarm calls lie in the frequency range of the best hearing of both the hawk and the tits: the mobbing call and a call given in response to a nearby hawk when fleeing from it. In contrast, the “seeet” call, an alarm call given mainly in response to distant flying sparrowhawks, can only be heard well by the tit. The implications of these results for hypotheses concerning the evolution of alarm calls in small songbirds are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1536
    Keywords: Membrane ; thin liquid film ; bilayer ; optical method ; three-layer model ; lipid film
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The total thickness of thin lipid films can be determined by the method of absolute or relative reflectance measurements. The film is described by the symmetrical three-layer model. By assuming equal refractive indices for the hydrocarbon layer and for the organic solution, the thickness and refractive index of the head group layer can be estimated.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 267 (1989), S. 839-843 
    ISSN: 1435-1536
    Keywords: Gelatin ; surfactant ; bindingisotherm ; surfactant-selectiveelectrode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A surfactant-selective eletrode in which the membrane is an o-nitrotoluene phase containing a dissolved complex of cetyltrimethylammonium-dodecyl sulfate has been applied to investigations of the interaction between gelatin and alkyl sulfates as well as gelatin and alkyltrimethylammoniumions in dilute aqueous solutions. The binding isotherms were obtained by comparing emf-values obtained for surfactant in water to the electrode potentials in gelatin solutions plotted in terms of surfactant concentration. The binding of alkyl sulfates was measured as a function of pH at constant free surfactant concentration. At pH values ≥ 7 the degree of binding is indpendent of the pH of the solution. The level of binding of alkyl sulfates to gelatin increases strongly with increasing chain length of the alkyl sulfate. At pH values ≤ 6 the extent of binding increases steeply with decreasing pH. Octyl sulfate shows a very low level of binding even at low pH. Cationics show much weaker interactions with gelatin than anionic surfactants of comparable alkyl chain length.
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  • 4
    ISSN: 1437-2320
    Keywords: CT-scan ; malformations and inflammatory diseases ; orbita ; orbitocranial tumors ; sonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Standardized sonography and CT scanning have distinct advantages and disadvantages in the evaluation of patients with orbital diseases. Echography provides an efficient screening examination in patients presenting with signs and symptoms of orbital pathology. It allows the detection, localization, measurement and in almost 80% differentiation of orbital lesions. High resolution CT scanning gives an excellent topographic display of masses in the orbit. In visualization of intracranial causes of orbital processes and demonstration of changes in the posterior third of the orbit, in the orbital bones and the periorbital sinuses it is superior to ultrasonography.
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  • 5
    ISSN: 1435-1536
    Keywords: Gelatin ; surfactant ; octadecanoic acid ; dynamic behaviour ; monolayer ; radio-tracer technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using the radio-tracer technique the dynamic behaviour of a14C-octadecanoicacid monolayer spread on a gelatin adsorption layer was investigated. The experimental set-up and conditions are given. It was shown that the dynamic behaviour significantly differs form that of a14C-octadecanoic-acid monolayer spread on a 10−2 M/dm3 HCl solution. The differences were explained on the basis of the ionic interactions of the octadecanoic acid monolayer with the gelatin. The aimed blocking of the ionic groups of the gelatin by means of an anionic (SDS) and a cationic (CTAB) surfactant lead to the result that the dynamic behaviour of the spread monolayer did not differ from that spread on a gelatin-free aqueous solution. So the addition of SDS and CTAB to the gelatin solution dependent upon the concentration used, leads to mixed surfactant/gelatin complexes or to the formation of a multilayer system consisting on an octadecanoic monolayer on the top of a gelatin-surfactant complex adsorption layer. The restriction of the interaction between the spread monolayer and the gelatin by both surfactants could be explained as the result of a sterical hindrance.
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  • 6
    ISSN: 1435-1803
    Keywords: hypertension ; estrogen treatment ; spontaneously hypertensive rats ; life-span ; sex difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 2 series of experiments on 144 SHRSP, the influence of treatment with different doses of 17-betaestradiolbenzoate (EB) (0.031, 0.125, 0.5 mg/kg EB or placebo) on the development of hypertension from the 9th to 22nd week of life (increase of blood pressure (BP) of untreated male rats from 178 to 252 mm Hg and of untreated female rats from 151 to 192 mm Hg) and in well established hypertension from the 23th to 36th weeks of life (male untreated rats 238 mm Hg (prior to the observation)) was investigated. In both series, observation periods consisted of a therapy phase of 14 weeks and a follow-up phase of the same duration. The untreated female rats had a longer life-span (88.5 weeks) than the untreated male rats (68.0 weeks). The estrogen treatment of female animals had an effect on BP only with the highest dose of EB and had no effect on the life-span of the animals. However, in male rats, the development of hypertension was inhibited by EB. Male rats treated at an earlier stage had a life-span equal to that of the female animals. When hypertension was already well-established treatment with EB had an antihypertensive effect in male rats (BP fall: 27–36 mm Hg), but no prolongation of the life-span was obtained.
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  • 7
    ISSN: 1435-1536
    Keywords: adsorption kinetics ; ionic surfactants ; electric double layer influence ; theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetic equation to describe the adsorption process of ionic surfactants (derived in part 1) will be solved numerically. The results show the effect of parameters such as ion valencyz, thickness of theDL x −1, and surfactant parametersΓeq,K, andK ads on the adsorption process. The results can be used to decide whether the model can explain experimental data on charged surfactant molecules or not.
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  • 8
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: One of the basic prerequisites for rational and high quality production of plastic parts is a tool layout tailored to the production process. To date, both design and construction have generally been based on values acquired by experience. This first, necessitates highly qualified personnel and second, involves what is frequently time consuming and costly finishing work. Experience acquired so far with computer-aided layout of injection molds shows that even a designer with little experience reaches the target more quickly and more reliably. At the same time he is able to draw on the results of intricate calculation and simulation methods which he was unable to apply in the past for reasons of time alone. This paper thus sets out the possibilities currently open and the experience available for computer-aided mold layout. The chief point of focus here is a system for the layout of injection molds. Working on from this system, however, the potentials for computer application are presented for blow mold- and foaming mold-design. After finding the mold principle, mold layout essentially divides up into two major areas, namely dimensioning calculations (CAE) and compilation of production documents (CAD). In dimensioning, the different functional elements of the mold are calculated. The aids that have been developed and the potentials of computer-aided dimensioning are presented with examples from the fields of rheological, thermal, and mechanical mold layout. Computer-aided rheological layout divides up into two steps. The first gives information on qualitative filling behavior (filling picture, flow paths) and the second provides quantitative results (pressures, shear stresses, temperatures). Computer-aided thermal layout similarly divides up into part steps. These are a rough overall energy balance, a rough layout of the tempering system, a segmented layout, and a homogeneity check, which involves simulating the temperature conditions in the mold by means of difference methods. When it comes to mechanical layout of the mold, programs are available for deformation calculations on basic cases and these will frequently be sufficient. For more complex cases of loading and deformation, a finite element program is used. Graphic data processing units can be used to supply extra facilities - first, to provide an aid for the simulation programs in dimensioning and second, to rationalize the compilation of the production documents. An illustration of a CAD workplace is given, incorporating the necessary computer configuration and peripherals. Compiling production documents is essentially a problem of variant design. The variants in this case are the individual components of the mold and a number of standardized accessories that can be called up as “standardized components.” The mold cavity, however, always has to be a free design. All programs are dialogue driven and are in a standardized manner so that even designers with no data processing experience can use the computer as an aid. The CAD/CAE system presented duly fulfils all these requirements. It allows the designer, at a single computer work station, to carry out both simulation and dimensioning calculations, to obtain information on material data, and to compile production documents on the basis of variant and free design. This provides the designer with a readily manageable aid and makes a considerable contribution towards improving the design result. Finally, the capacity of different computer concepts and the CAE/CAD/CAM systems on the market are discussed. For the future it will be possible to establish a computer-aided link between the different areas of design, from development of the molded part, via mold design and production, through setting the processing parameters of the injection molding machine.
    Additional Material: 43 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: By using particle electrophoresis and quantitative analysis the interaction of anionic surfactants (sodium dodecylculfate, sodium decylbenzene sulfonate) with a hydrocarbon-grown yeast and a commercial baker's yeast has been investigated to obtain further informations about the chemical composition of the surface region (3-6 nm) of the cell wall of this yeasts. A correlation is found between the chemical composition and the different adsorption behaviour of various batches of the same yeasts. It was found that surface-localized hydrophobic glycoproteins, probably proteophosphomannan are responsible for the strong pH dependent adsorption behaviour of a typical Candida species.In contrast the cell surface of a typical Saccharomyces species was strongly hydrophilic and showed no surfactant adsorption.This can be explained by the presence of a polysaccharide probably phosphomannan in the surface region only.The implication of proteins in the adsorption process is confirmed by model experiments too.The models for the yeast cell wall proposed by LAMPEN and KIDBY et al. were critically discussed in terms of our results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Behinderung und letztliche Blockierung der normalen Schmelzkristallisation von zentralen Ethylenoxid[EO]-Blöcken durch Methylmethacrylat-(MMA)-Endblöcke ansteigender Läange in Triblockcopolymeren vom Typ ABA, anionisch auf einem neuen Weg synthetisiert, wurden mit Hilfe der differentiellen Scanning-Calorimetrie und der Röntgenstreuung untersucht. Experimentelle Untersuchungen des Glasiihergangs, der Keimbildung bei tiefen Temperaturen und der morphologischen Zehn-Nanometer-Struktur werden eingeschlossen. Geringe Mengen (Prozentbereich) langer Homo-PEO-Ketten können in einer ABA-Matrix kristallisieren, welche sonst normal nicht kristallisierbar ist. Aus den Experimenten wird geschlossen, daß in den untersuchten Systemen mit PEO-Molekiilmassen bis zu 50 000 g/mol eine Bewegung der Kettenenden notwendig ist fur die Schmelzkristallisation unter normalen Bedingungen.
    Notes: Hindering and final blocking of the normal melt crystallization in central ethylene oxide (EO) blocks by methyl methacrylate (MMA) end blocks of increasing lengths in ABA type triblock copolymers synthesized anionically in a new way are investigated by differential scanning calorimetry and X-ray scattering. Experimental studies of glass transitions, low temperature nucleation, and the morphologic ten-nanometer structure are included. Low percentage amounts of long homo-PEO chains can crystallize in an ABA matrix which otherwise is not normally crystallizable. It is concluded from the experiments that in our systems with PEO molecular masses up to 50 000 g/mol the motion of the chain ends is necessary for melt crystallization under normal conditions.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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