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  • 1
    Electronic Resource
    Electronic Resource
    Some effects of cocatalyst structure on the anionic polymerization of ε-caprolactam (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 1363-1369 
    Details
    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: N-Acetyl, N-butyryl, N-stearyl, N-benzoyl, N-4-methoxybenzoyl, and N-4-nitrobenzoyl caprolactams were prepared and used as cocatalysts for the anionic polymerization of caprolactam. The results of these studies indicate that all of the cocatalysts used, except N-acetylcaprolactam, exert a steric effect which lowers both the rate and degree of polymerization. The N-benzoyl derivative appeared to be a slightly better cocatalyst than the N-4-methoxybenzoyl derivative. This may be due to the fact that the N-benzoyl group is the more electron-attracting group. N-4-Nitrobenzoylcaprolactam was unstable under the reaction conditions employed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080326
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  • 2
    Electronic Resource
    Electronic Resource
    Some effects of cocatalyst structure on the anionic polymerization of ∊-caprolactam. II.From the theses of R. P. Scelia and S. E. Schonfeld which were submitted in partial fulfillment of the requirements for the degree of Master of Science. (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 1299-1313 
    Details
    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: A study of the effect of catalyst (base) concentration and N-acylcaprolactam cocatalyst size and substitution on the fast anionic polymerization of caprolactam indicated that a steric effect due to cocatalyst size exists, and perhaps an electronic effect due to cocatalyst substitution was noted. The rate of polymerization, degree of polymerization, and yield of polymer are related to these effects. It was also noted that at high base concentrations, the rate and degree of polymerization along with the product yields all decrease. These latter observations suggest that reinterpretation of some of the reaction mechanism data may be important if polymer degradation is not an appreciable factor during the reaction.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070110726
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  • 3
    Electronic Resource
    Electronic Resource
    Transport of liquids in structurally modified polyethylene (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 897-933 
    Details
    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: Cast linear polyethylene films subjected to dry and solvent annealing display markedly different sorption and difusion barrier properties than do untreated films. The subsequent sorption of liquid o- and p-xylene and cis- and trans-acetylene dichloride per unit volume of amorphous polymer increases as the annealing temperature and/or treating solvent concentration increases. Integral diffusivities calculated from sorption and steady-state permeation rates show a monotonic increase with sorption per unit volume of amorphous polymer. The concentration dependence, however, is less marked than observed in similar systems at low permeant activity. Apparently the above treatment reduces the effective crosslinking imposed by the crystallites on the amorphous polymer chains through disentangling and incorporating some of these chains into crystallites. Thus the polymer is capable of a greater degree of swelling when brought into contact with a compatible liquid in a spite of a higher degree of crystallinity. The low concentration dependence of the diffusivities is probably due to heterogeneous distribution of excess permeant in a treated film. If the excess permeant were preferentially sorbed in regions of low polymer concentration then the above observations could be explained. Long-duration, osmotic stress-induced swelling and recrystallization have been cited to account for time-dependent permeation rates in treated and untreated films.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080229
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  • 4
    Electronic Resource
    Electronic Resource
    Computer analysis of the human embryo growth curve: Differences between published ultrasound findings on living embryos in utero and data on fixed specimens (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 237 (1993), S. 400-407 
    Details
    ISSN: 0003-276X
    Keywords: Human embryo ; Crown-rump length ; Greatest length ; Computer analysis ; Vaginal ultrasound ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Accurate information on the normal growth rate of the human embryo is fundamental to a better understanding of the embryonic period of pregnancy. Crown-rump length measured previously in utero (N = 227) with vaginal ultrasound in 107 in vitro fertilization (IVF) or gamete intrafallopian transfer (GIFT) singleton pregnancies was compared to the greatest length of fixed human embryos from the Carnegie collection, of known developmental stage whose postovulatory ages were estimated from menstrual histories. Average crown-rump length in utero was 60% of the greatest length of the fixed specimens prior to postovulation day 33, but were equal after postovulation day 40. The growth rate of in utero embryos and fixed specimens, analyzed by computer using exponential equations, was compared to linear and polynomial equations used in previously published embryo growth tables. The exponential equation, length = exp(a + b/age), fit in utero measurements best, while the equation length = exp[a + b/exp(age)] fit the fixed specimens best. Differences between length in utero and in fixed specimens may be related to distortion of the fixed embryos resulting from the formalin fixation, to ultrasound distortion, to curling of the embryo, or to incorrectly estimated ages of the fixed specimens. Study of human embryos in utero is now practical with vaginal ultrasound. © 1993 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092370313
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of the parotid gland in the little brown bat (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 210 (1984), S. 491-502 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The ultrastructure of the parotid gland was examined in the little brown bat. The seromucous acinar cells contained abundant granules of variable morphology. These granules were characterized by a submembranous dense layer consisting of fine parallel slats. In some bats, the matrix of the granules was structureless, whereas in others it consisted of closely packed but randomly arranged bundles of tubules. The intercalated ducts had a highly developed rough endoplasmic reticulum, often containing large numbers of intracisternal granules. In contrast, only a few secretory granules were present in the supranuclear cytoplasm. The striated ducts, which exhibited the characteristic basal striations consisting of vertically oriented mitochondria and highly folded plasmalemmas, contained numerous small dense granules in a subluminal band. These granules had a paracrystalline substructure with a periodicity of 8 nm. Excretory ducts strongly resembled striated ducts. They showed the same kind of basal striations and about half their constituent cells contained small paracrystalline granules.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092100310
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  • 6
    Electronic Resource
    Electronic Resource
    Craze growth and healing in polystyrene (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 2541-2560 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of craze growth and craze healing were studied by dark-field optical microscopy in monodisperse molecular weight polystyrene (PS) that varied in molecular weight from 88,000 to 1,334,000. The following observations were made. (1) G1 the virgin growth rate, decreased rapidly with increasing molecular weight until Mn ∼ 200,000 and then remained constant. (2) G1 decreased with increasing craze density. (3) The growth rates of approaching craze tips decreased when the craze tips overlapped, and the effect was less for crazes whose parallel growth paths were greater than 40 μm apart. (4) Complete craze healing was observed by comparison of the nucleation times, τ2, and growth rates, G2, of healed individual crazes with the craze kinetics of the virgin sample. (5) The extent of healing was characterized using four cases in which τ and G were measured as a function of healing time, temperature, constant stress, and molecular weight. (6) Craze healing times were found to increase with molecular weight and were analyzed in terms of the modified molecular weight of the craze zone. (7) Significant bond rupture was determined to occur during crazing by comparison of healing times with stress relaxation and diffusion data. (8) Craze healing studies provide insight into both crack healing and fracture of glassy polymers.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090251209
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  • 7
    Electronic Resource
    Electronic Resource
    Preconcentration and determination of lead(II) at crown ether and cryptand containing chemically modified electrodes (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 13-21 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemically modified electrodes (CMEs) containing incorporated crown ether and cryptand ligands as modifiers were evaluated for their ability to preconcentrate metal cations prior to quantitation by conventional voltammetric methods. Stable CMEs were formed for 18-crown-6, dibenzo-18-crown-6, poly(dibenzo-18-crown-6), dibenzo-24-crown-8, and 2.2.2-cryptand by mixing the desired amount of the ligand into carbon paste. The resulting electrodes exhibited complexing capabilities that were similar to those of the free ligands. In particular, the CMEs were very reactive toward Pb2+ and Hg2+. Pb2+ uptake was sufficiently strong that a detection limit of 1 μM was obtained following a 20-sec exposure to the sample and transfer to a blank electrolysis solution for differential pulse voltammetric analysis. Accurate quantitation of micromolar levels of Pb in water and urine reference standards was achieved at the CMEs by means of a simple procedure requiring minimal sample preparation. Finally, the analytical characteristics of CME preconcentration were directly compared to those of the electrodeposition approach ordinarily employed in stripping voltammetry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010104
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  • 8
    Electronic Resource
    Electronic Resource
    Electrochemical characterization of aminated PVC-based ion-selective membranesDedicated to the memory of Prof. Wilhelm Simon. (1993)
    Weinheim : Wiley-Blackwell
    Electroanalysis 5 (1993), S. 725-730 
    Details
    ISSN: 1040-0397
    Keywords: Ion selective electrodes ; pH sensors ; aminated PVC ; impedance measurements ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric and impedance characteristics of a large number of pH sensitive, piperazine-based aminated PVC membranes are summarized. The main goal of the work was to predict the differences between “good” and “bad” responsive potentiometric pH membranes with very similar overall nitrogen contents. The only conclusion gained previously from other methods was that the N content should be between 0.5 and 0.8% for Nernstian response. The detailed analysis of the data show that a given N content of the basic material is a necessary but not a sufficient requirement with respect of the quality of potentiometric response. Conditions for appropriate pH response of the membrane are formulated in terms of surface and bulk impedance characteristics. The ideal pH response of an optimized aminated PVC membrane, which corresponds to a minimum surface impedance, is presented. The primary importance of surface amines relative to bulk amines (the conformation and distribution of active sites) is proven in a simple experiment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140050904
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  • 9
    Electronic Resource
    Electronic Resource
    Evaluation of copper-based electrodes for the analysis of aminoglycoside antibiotics by CE-EC (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 1145-1151 
    Details
    ISSN: 1040-0397
    Keywords: Copper electrode ; Antibiotics ; Capillary electrophoresis ; Aminoglycosides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aminoglycoside antibiotics including gentamicin, bekanamycin, tobramycin, lincomycin, neomycin, kanamycin, and ribostamycin have been determined by CE-EC with copper clectrodes. Both copper wall-jet electrodes (WJEs) and copper on-capillary electrodes (OCEs) were evaluated. The OCEs provided μM detection limits, superior stability and reproducibility (2-3% relative standard deviation in oxidation current), and a simple instrumental set-up without the need for capillary/electrode alignment. The analytical capabilities of the Cu-OCE were examined, following the optimization of CE conditions, for the seven aminoglycosides above; and the practical utility of this approach was demonstrated through the determination of aminoglycoside antibiotics in three pharmaceutical preparations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140091502
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  • 10
    Electronic Resource
    Electronic Resource
    Use of a new fluorescent probe, seminaphthofluorescein-calcein, for determination of intracellular pH by simultaneous dual-emission imaging laser scanning confocal microscopy (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 164 (1995), S. 9-16 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A new pH indicator, seminaphthofluorescein (SNAFL)-calcein acetoxymethyl ester, was used for intracellular pH (pHi) measurement in living MDCK cells with a laser scanning confocal microscope (LSCM) equipped with an Argon/Krypton laser and dual-excitation and dual-emission (FITC/Texas Red) filter set. SNAFL-calcein excitation maxima are ∼492/540 nm (acid/base) and emission maxima are ∼535/625 nm (acid/base) with a pKa value at ∼7.0. The absorption/emission spectra of SNAFL-calcein indicate that the ratio of emission intensities of its basic/acidic forms is pH dependent. With an Argon/Krypton LSCM, we were able to monitor the acidic and basic forms of this dye simultaneously using dualexcitation (488/568 nm) and dual-emission (525-614 nm/∼615 nm) wavelengths (λs). The simultaneous dual-excitation/emission LSCM system allows for efficient recording of pHi dynamics (time resolution ≍ 1 sec) in living cells. We have analyzed emission stability of the dye at different temperatures (22°C and 37°C) and constant pH, and at the same temperature (22D°C) but various pHs (6.6, 7.0, and 7.4). Bleaching rate is slightly higher at 37°C than that at 22°C. The basic form of the dye (λEm ≍ 625 nm) has a slightly higher bleaching rate than the acidic form (λEm ≍ 535 nm) in standard culture medium (pH 7.3) at either 22°C or 37°C. The pHi in MDCK cells calculated from ratio images (535 nm/625 nm) was 7.19 ± 0.03 (mean ± SEM, n = 20). Calibration experiments show that the useful pH range of SNAFL-calcein appears to be between 6.2 and 7.8, as the dye is difficult to calibrate outside this pH range. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041640103
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