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  • 1
    Electronic Resource
    Electronic Resource
    The characteristics of local application of retinoic acid to the regenerating axolotl limb (1985)
    Springer
    Development genes and evolution 194 (1985), S. 228-235 
    Details
    ISSN: 1432-041X
    Keywords: Retinoic acid ; Vitamin A ; Limb regeneration ; Pattern formation ; Axolotls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The work described here is concerned with the effects of local application of retinoic acid to the regenerating limb, administered in silastin blocks. Using 14 C RA we have shown that its rate of diffusion into medium was the same as into regenerating limbs and that the curve of percent loss shows a fast rise tailing off to a plateau. RA caused specific alterations in the proximodistal axis of the regenerate such that complete limbs could be produced from distal amputation planes. Increasing concentrations of RA caused regeneration to commence from increasingly more proximal levels. The effect of time of administration after amputation on proximodistal duplication has been investigated as well as position effects with silastin blocks placed either at the anterior, posterior or dorsal poles of the blastema. These data permitted an estimate of the absolute amount of RA needed to cause alterations in the proximodistal axis −2 to 16 μg per limb or 1 ng per cell. Supernumerary limbs were also induced by these local implants and here there was a distinct position effect with the dorsal side causing the highest frequency. This reveals a possible effect of RA on the anteroposterior axis of regenerating limbs, but some of these supernumeraries were thought to arise from the irritant action of RA rather than a specific effect on pattern formation. The relevance of these results to those obtained on other systems is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848251
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  • 2
    Electronic Resource
    Electronic Resource
    Extraction of mixed solutes: I. Separation of formic and hydrochloric acids. II. Separation of acetic and sulfuric acids (1961)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 7 (1961), S. 456-462 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In many complex systems in solvent extraction a second solute is often present or is added to promote extraction of the first solute. Previous studies showed that the electrolyte sulfuric acid can be considered as a salting-out agent for extraction of formic acid from water by methyl isobutyl ketone.In the present work two systems were studied: (I) hydrochloric acid-formic acid-water-methyl isobutyl ketone and (II) sulfuric acid-acetic acid-water-methyl isobutyl ketone. Selectivities of over 200 were found favoring the extraction of formic over hydrochloric acid, and values of over 6,000 favoring the acetic over the sulfuric acid were found. The data for extraction of formic acid were correlated by the Setschenow equation. A similar type of equation was found for extraction of acetic acid in system II.The results indicate that the electrolyte hydrochloric acid can also be considered as a salting-out agent for formic acid. The data show that sulfuric is more effective than hydrochloric acid in salting-out the formic acid. This is in qualitative agreement with experimental data in other systems employing sulfate and chloride electrolytes and with the theoretical equation derived by Debye and McAuley. About 28% less sulfuric acid is needed to salt-out a given amount of acetic acid when compared with salting-out the same amount of formic acid.The changes in activity coefficient of the acetic acid in the aqueous phase with additions of sulfuric acid were measured in system II. These activity coefficient changes could account for only about 39% of the increase in distribution ratio of the acetic acid. A possible explanation for this is that the molecular species of the acetic acid in the organic and aqueous phases changed when sulfuric acid was added to the water phase.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690070323
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  • 3
    Electronic Resource
    Electronic Resource
    Azide photoresists for projection photolithography (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 491-493 
    Details
    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 spectral sensitivity of bisazide sensitized rubbers has been extended to 5000Å by the addition of p-azidocinnamylidene derivatives of cyclohexanone. The photoresists were suitable for projection exposure at 4050 and 4350 Hg lines. The photospeed of the compositions is enhanced by increasing the unsaturation of the polymer component. Speed increase could also be obtained by exposure of the films at elevated temperatures.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760140705
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