Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (24)
  • Articles: DFG German National Licenses  (24)
  • Wiley-Blackwell  (24)
  • 1
    ISSN: 0886-1544
    Keywords: immunofluorescence ; video-enhanced contrast microscopy ; protrusions ; lamellipodia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The formation of lamellipodia in migrating cells involves dynamic processes that occur in a cyclic manner as the leading edge of a cell slowly advances. We used video-enhanced contrast microscopy (VEC) to monitor the motile behavior of cells to classify protrusions into the temporal stages of initial and established protrusions (Fisher et al.: Cell Motility and the Cytoskeleton 11:235-247, 1988), and to monitor the fixation of cells. Multiple parameter fluorescence imaging methods (DeBiasio et al.: Journal of Cell Biology 105:1613-1622, 1987; Waggoner et al.: Methods in Cell Biology, Vol. 30, Part B, pp. 449-478, 1989) were then used to determine and to map accurately the distributions of actin, myosin and microtubules in specific types of protrusions. Initial protrustions exhibited no substructure as evidenced by VEC and actin was diffusely arranged, while myosin and microtubules were absent. Newly established protrusions contained diffuse actin as well as actin in microspikes. There was a delay in the appearance of myosin into established protrusions relative to the presence of actin. Microtubules were found in established protrusions after myosin was detected, and they were oriented parallel to the direction of migration. Actin and myosin were also localized in fibers transverse to the direction of migration at the base of initial and established protrusions. Image analysis was used to quantify the orientation of actin fibers relative to the leading edge of motile cells. The combined use of VEC, multiple parameter immunofluorescence, and image analysis should have a major impact on defining complex relationships within cells.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0021-8995
    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 , Physics
    Notes: The transesterification reaction in the molten state of ester groups of ethylene vinyl acetate (EVA) copolymers and ethylene acrylic ester (EMA) copolymers has been used to crosslink the chains of this polymeric system. The relative EVA copolymers (or EMA copolymers) concentration dependence of the network formation by co-crosslinking of EVA/EMA miscible blends has been assessed. EVA/EMA networks were characterized by swelling experiments, rheological measurements, and determination of the extent of the reaction through a chromatographic technique. All results can be compared in a master curve. The influence of the polydispersity and the microstructure of EVA and EMA samples was put in evidence. On the other hand, a scaling law (v2∼Mc-3/5) was observed in agreement with predictions of the Flory-Rhener expression. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The transesterification reaction catalyzed by dibutyltin oxide has been used to crosslink miscible blends (at about 200°C) of ethylene vinyl acetate (EVA) and ethylene methyl acrylate (EMA) copolymers. Then, microwave heating at 2.45 GHz with the fundamental TE01 mode was used for activation of this crosslinking reaction. The microwave treatment was carried out in a continuous process through a resonant cavity on line with a twin screw extruder equipped with a strip die or a circular die, which imposed the shape of the samples in the waveguide. Therefore, a shape factor due to the geometry of the samples and their orientation with respect to the electromagnetic field was defined. Last, this technique was applied to the microwave crosslinking of an EVA/EMA blend dispersed in a polypropylene matrix and consequently offers a new route to control the morphology of the polymer blends.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 47 (1975), S. 61-77 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: When the ozonisation of bulk or suspension poly(vinylchloride) is carried out in tetrachloroethane solution between 0-120°C the molecular weight decreases continuously and the rate of breaking of chains deduced from the intrinsic viscosity variation is constant under isothermal conditions. Whatever the time and temperature of ozonisation may be, at every breaking, β and α chlorinated acid groups are introduced which have been characterized by infrared spectroscopy, high resolution NMR spectroscopy and potentiometric titration in dimethylformamide. Besides these functions, peroxide groups have also been identified and their concentration has been determined for different times and temperatures of ozonisation.This study permits to propose two mechanisms to explain the breaking of chains. The first implies the previous dehydrochlorination of the polymer and the second the formation of unstable peroxides which by decomposition cause the breaking of chains.
    Notes: Quelle que soit la nature du polychlorure de vinyle (masse ou suspension) l'action de l'ozone en milieu homogène dans le tétrachloroéthane provoque la décroissance continue de la masse moléculaire dans le domaine de température 0-120°C et la vitesse de coupure des chaînes déduite des variations de viscosité est constante en conditions isothermes.Quels que soient le temps et la température d'ozonisation, à chaque point de coupure apparaissent des fonctions acides α et β chlorées qui ont été caractérisées par spectroscopie infra-rouge, RMN haute résolution et dosage potentiométrique en milieu diméthylformamide. Outre ces fonctions, des peroxydes ont égé également identifiés dans le polymère et on a suivi leur concentration en fonction des conditions d'ozonisation.Cette étude permet de proposer deux mécanismes pour expliquer la coupure des chaînes, l'un suppose une déhydrochloruration préalable du polymère et l'autre la formation de peroxydes instables qui en se décomposant provoqueraient la coupure des chaînes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0021-8995
    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 , Physics
    Notes: Whatever the state of the iron compounds as smoke suppressant during the combustion of poly(vinyl chloride), they lead rapidly to native αFe2O3 in the char residue left after dehydrochlorination. It causes incandescence of the char residue and catalyzes its oxidation into carbon monoxide and carbon dioxide that contributes to decreasing the amount of available carbon for the soot formation after self-ignition. FeCl2 and FeCl3 are the precursors of αFe2O3, which is the true compound as smoke suppressant. Nevertheless, as intermediate, iron chlorides are able to modify the degradation processes, and they favor the formation of light tars instead of heavy tars. For that reason the iron compounds cause the formation of smoke at lower temperature than for pure PVC, but, as αFe2O3 is formed, the smoke production levels off and then decreases. The higher the ease of the iron compounds to give chlorides through reaction with HCI and further native αFe2O3, the higher the ease of the additive to cause the oxidation of the char residue sooner and in consequence to decrease the smoke level. In the PVC combustion three main steps may be distinguised: dehydrochlorination step between 200-300°C; tars aerosols formation from the char residue between 300°C and self-ignition; at temperature higher than self-ignition, formation of soot from the previous tars as precursors.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 1544-1550 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Plastic profile die design is a complex task because of cross section area and shape changes occurring after die exit. Dimensions of the profile are increased by the extrudate swell phenomenon and decreased by drawdown and shrinkage. An experimental study on the effect of processing conditions on extrudate swell and on the shape of a rectangular profile was done for rigid poly(vinyl chloride), PVC, and high density polyethylene, HDPE, resins. Extrudate swell was found to be a strong decreasing function of residence time in the die and also, for short dies, of entrance geometry. For PVC, equilibrium swell increased with melt temperature. The differences in swelling for the two polymers are explained with the help of creep/recovery data obtained on a stress rheometer. Drawdown, die land length, and melt temperature were shown to have an important effect on the shape of a rectangular profile. Decreasing the die land and increasing the melt temperature had the effect of increasing preferably the thickness while drawdown, by inhibiting the swelling, decreased the thickness.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The stereoselective substitution of chlorine atoms was used to graft anthracene and phenyl groups onto the poly(vinyl chloride) (PVC) backbone as ultraviolet (UV) tracers for the assessment of the residence time distribution (R.T.D) of PVC chains during the extrusion of rigid and plasticized PVC. The residence time distribution obtained using these-grafted tracers was compared with that obtained using a free UV tracer (anthracene). The polymeric tracer had a narrower R.T.D and a shorter mean residence time. This difference of behavior between a free and grafted tracers was attributed to the compatibility of these tracers with the PVC.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Transesterification may be used to crosslink a copolymer such as ethylene vinyl acetate with poly(ethylene acrylate-co-propylene) in the presence of dibutyltin oxide as a catalyst. A rheological study of the mechanism of this exchange reaction has been made: The kinetics of the crosslinking reaction was determined by studying the time and temperature dependence of the dynamic storage modulus G′(t, T)ω. Kinetic curves obtained for different reactive blends (EVA, PP/EVA, and PPf/EVA) allowed for the evaluation of the activation energy of the reaction and, thus, specified the appropriate parameters (temperature and time) for carrying out this reaction in a molten state.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The linear viscoelastic behavior of commercial broad-distribution polypropylenes is studied. The samples underwent different controlled peroxide degradation rates, so they exhibit different molecular distributions. The relaxation spectrum is obtained by assuming that it takes the shape of a Log-Normal distribution. It is in agreement with the linear viscoelasticity theory by providing limiting values, contrary to other models. Moreover, the ratio τw/τn which takes place in this law is very useful to distinguish the synthesis differences of the samples when the Melt Flow Index alone cannot.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Using an integral nonlinear constitutive equation including the Log-Normal relaxation spectrum, the fiber-spinning behavior of commercial polypropylenes is studied. The relaxation spectrum is strongly related to the molecular weight distribution. Moreover, by means of a finite element analysis, simulated stress and velocity profiles are obtained either in isothermal or nonisothermal cases. In the isothermal case, broadening the relaxation spectrum leads to more pronounced curvature of the velocity profile. In the nonisothermal case, the critical draw ratio is sensitive to the mean relaxation time which depends on both average molecular weight and distribution breadth. It is shown that increasing the average relaxation time leads to a less rapid growth of the velocity. Furthermore, this effect is less pronounced when the relaxation spectrum is wider.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...