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  • 1970-1974  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Proximate Composition of Freshwater Fish — Grass Carp, Puntius gonionotus and Tilapia (1971)
    Springer
    Hydrobiologia 37 (1971), S. 361-366 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The proximate analyses of freshwater fish — Grass carp (Ctenopharyngodon idellus), Puntius gonionotus and Tilapia (male hybrid) are compared. Dried meals from eviscerated freshwater fish contained 57.36–75.92% protein; 4.48–31.84% fat and 10.68–22.88% ash. The results indicate that Tilapia had a higher fat content than gonionotus and grass carp, the latter having the lowest fat content. The reverse is true for protein, ash and minerals like sodium, phosphorus and potassium. The composition of grass carp feeding on different diets, such as Hydrilla verticillata, Napier grass (Pennisetum purpureum) and tapioca leaves (Manihot utilissins) indicated only a slight difference in protein content but a significant difference in fat and ash. The tabulated results show that grass carp and goniotus were of higher nutritive value when compared to the Tilapia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015581
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  • 2
    Electronic Resource
    Electronic Resource
    Preliminary studies on the composition of major ions of some fish ponds of Malacca in Malaysia (1971)
    Springer
    Hydrobiologia 37 (1971), S. 537-543 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper presents data on the ionic composition of tropical pond waters. The discussion is on the major cations calcium (6.58 p.p.m.) and sodium (3.79 p.p.m.) and the anions bicarbonate (20.24 p.p.m.) and sulphate (21.69 p.p.m.). Some ponds have extremely low alkalinity (10 to 27 p.p.m.) and most of the ponds have poor dissolved calcium content (2.5 to 9.9 p.p.m.). Their pHs lie between 6.71 to 7.70 except the control pond F1 which has a pH of 5.21. The chemical data show differences in the ionic composition between the various ponds of different sizes. The differences can be due to the accumulated organic matter, types of fish stocked and the supplementary feeds used in the ponds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018819
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  • 3
    Electronic Resource
    Electronic Resource
    Stereospecific bulk polymerization of methyl methacrylate initiated by its tactic polymers (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 989-1001 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl methacrylate (MMA) was polymerized by radical initiation at 90°C by its own preformed tactic polymers, i.e., conventional (c-PMMA), isotactic (i-PMMA), and syndiotactic (s-PMMA) PMMA, and also by a preformed 1:1 stereocomplex of i-PMMA and s-PMMA. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR spectra and viscometry. Higher polymerization rates were obtained in the presence of stereo-regular PMMA than in the presence of c-PMMA. Moreover, it appeared that i-PMMA promoted the formation of s-PMMA, and conversely s-PMMA the formation of i-PMMA, especially in the initial stages of the reaction. A higher M̄v of the preformed polymer yielded a higher rate and a higher stereospecificity of the polymerization. No polymerization took place in the absence of performed PMMA. The results support a replica mechanism proposed by Szwarc, in which polymerization is preceded by a specific arrangement of monomeric units along the polymeric chain into a distinctive pattern. Such arrangement coupled with a strong tendency of the isotactic and syndiotactic species to associate may lead to the present stereospecific replica polymerization. This association is demonstrated by rapid gelation during polymerization and by lowering of reduced viscosity in very dilute mixtures of i-PMMA and s-PMMA in MMA.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110506
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  • 4
    Electronic Resource
    Electronic Resource
    Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). IV. Influence of solvent type (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2975-2989 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C or 35°C in various solvents in the presence of stereoregular poly(methyl methacrylate) (PMMA). The occurrence of stereospecific replica polymerization appeared to be related to the capability of stereoassociation of isotactic and syndiotactic PMMA. The solvents can be roughly divided into three types. Type A solvents are polar solvents, which promote stereoassociation resulting in gelation and precipitation. Examples are dimethylformamide, dimethyl sulfoxide, and acetone. Type B solvents are nonpolar aromatic solvents like benzene and toluene, wherein stereoassociation is weaker but still leads to gelation. Type C solvents are very good solvents, in which stereoassociation does not occur. Chloroform and dichloromethane belong to this class. In solvents of type A as well as type B, polymerization in the presence of i-PMMA as a polymer matrix was syndiospecific. However, in the presence of s-PMMA as a polymer matrix the polymerization was isospecific only in type A solvents. The syndiotactic or isotactic triad contents of the polymer formed could be as high as ca. 90% at low conversions. In solvents of type C, polymerization in the presence of stereoregular PMMA proceeds according to a normal radical mechanism. Syndiotacticity was always less than 70%. Stereocomplexes formed in situ during replica polymerization were partly crystalline as detected by x-ray diffraction. The highest crystallinity was detected in those formed in type A solvents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170111116
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  • 5
    Electronic Resource
    Electronic Resource
    Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). II. Syndiotactic PMMA as matrix (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1003-1011 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed syndiotactic PMMA (sMA) with about 90% syndiotactic triads and of different M̄v, viz., sMA-1, 1.6 × 105; sMA-2, 3.0 × 105; and sMA-3, 8.7 × 105. The MMA:sMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. In all cases isotactic PMMA (i-PMMA) was produced, especially in the initial reaction stages, which associated with the syndiotactic substrate to form acetone-insoluble 1:2 i/s-stereocomplexes. The isotacticity decreased with conversion and was highest in the presence of sMA-3. Characterization of the acetone-soluble fractions indicated that i,s-stereoblock polymers were also produced. From these results it is concluded that this reaction can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i-PMMA and s-PMMA to associate. With sMA of M̄v below about 1.2 × 105, no i-PMMA is formed; in other words, no replica polymerization occurs. For polymerizations in the presence of sMA-2, the critical M̄v of propagating chains, with has to be exceeded before stereoassociation is strong enough to effectuate replica polymerization, has been estimated to be 0.6 × 105.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110507
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  • 6
    Electronic Resource
    Electronic Resource
    Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). III. Influence of temperature (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1013-1024 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl methacrylate (MMA) was polymerized by radical initiation at 0, 25, 50, 75 and 100°C in DMF in the presence of preformed isotactic PMMA (iMA) or preformed syndiotactic PMMA (sMA) with different M̄v and also without preformed PMMA (“blank” polymerizations). From the tacticities of the formed polymers it is concluded that blank polymerization does not conform to simple Bernoulli statistics, but follows at least first-order Markov statistics. The formation of long syndiotactic sequences in the presence of iMA and long isotactic sequences in the presence of sMA denotes still higher-order Markov statistics. The stereoregulating action is improved by higher M̄v of the preformed polymer (matrix) and lower reaction temperature. These influences can be explained by assuming an equilibrium between polymer growth on the matrix and in the “free” solution. For polymerizations in the presence of iMA or sMA below 300°K, the differences in activation enthalpies (ΔHs/i
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110508
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  • 7
    Electronic Resource
    Electronic Resource
    Radical polymerization of methyl methacrylate in the presence of isotactic poly(methyl methacrylate) (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 1031-1049 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed isotactic PMMA (iMA) with about 90% isotactic triads and different M̄v's, viz., iMA-1: 7.2 × 105; iMA-2, 5.0 × 105; iMA-3, 3.5 × 105; iMA-4, 1.25 × 105; and iMA-5, 1.15 × 105. The MMA:iMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. It is found that the M̄v of the polymer formed ran parallel to the M̄v of iMA. In all cases syndiotactic PMMA (s-PMMA) was produced which associated with the isotactic substrate to form acetone-insoluble stereocomplexes. The syndiotactic polymers probably consist of long syndiotactic and heterotactic sequences. The syndiotacticity decreased with conversion and was generally highest in the presence of iMA-1. With iMA-1 even the formation of some additional i-PMMA (in the acetone-insolubles) was indicated, especially in the later stages of the polymerization. Characterization of the acetone-soluble fractions indicated that i,s-stereoblock polymers were also produced, of which the persistence ratios ρ increased with the M̄v of iMA. From these results it is concluded that this reaction differs from the conventional radical polymerization and can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i- and s-PMMA to associate. The formation of i,s-stereoblock polymers and additional i-PMMA indicates that s-PMMA in its turn can also act as a polymer matrix.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1972.150100408
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