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  • General Chemistry  (1,332)
  • Inorganic Chemistry  (830)
  • Physics  (430)
  • Cell & Developmental Biology
  • 1980-1984
  • 1965-1969  (2,776)
  • 1967  (2,776)
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  • 1980-1984
  • 1965-1969  (2,776)
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  • 1
    Unknown
    New York : Academic Press
    Keywords: DDC 515/.353 ; LC QA371 ; Differential equations, Partial ; Physics
    Pages: Online-Ressource (xi, 335 pages)
    ISBN: 9780126546569
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 121 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 121 (1967), S. 55-70 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Light and electron microscopical studies allow a descriptive account to be given of he morphogenesis of the egg chamber of Drosophila melanogaster. The study demonstrates that the mitotic products of a single cystoblast generate a branching chain of 16 inter-connected cystocytes. Two specific cystocytes enter meiotic prophase, while the rest become nurse cells. The two pro-oocytes form synaptinemal complexes in their nuclei. However, one of the two cells later switches back into the nurse cell developmental pathway. The elongation of the synaptinemal complexes is described, and estimates are made of the time involved in their formation. These complexes continue to be synthesized long after the DNA replication which gives the oocyte its 4C DNA content. This finding implies that at least some genetic crossing over follows DNA replication. Evidence is presented that cells undergoing crossing over are most efficient in repairing radiation-induced chromosomal breaks. Suggestions are given as to the mechanisms by which (1) cell division is inhibited once 16 cystocytes are formed, (2) the future cleavage planes of cystocytes are programmed, (3) the pro-oocytes are differentiated from nurse cells, and (4) the oocyte is chosen from the twin pro-oocytes. The contrasting behaviors of the oocyte and nurse cell nucleoli are described. During oogenesis nucleolar synthesis of ribosomal RNAs is suppressed in the oocyte and concurrently stimulated in the nurse cells. It follows that the nurse nuclei are the major sources of the prodigious quantities of ribosomes found in the ooplasm of the mature oocyte.
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  • 4
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The enigmatic lophophoral organs of phoronids are demonstrated to by accessory sex glands. In the hermaphroditic Phoronis vancouverensis, each mature adult has two pairs of such glands: female nidamental glands that facilitate the temporary brooding of the embryos and male accessory spermatophoral organs that function in spermatophore elaboration. Functional males of Phoronopsis harmeri have complex accessory spermatophoral organs while females of this non-brooding dioecious species lack accessory sex glands.In both species, coelomic spermatozoa are accumulated within the nephridia and passed en masse into the partially enclosed spermatophoral organs. There each sperm mass is molded into a characteristic shape and encased in one or more membranes before release as a spermatophore into the ambient water. The structure of the spermatophore is characteristic for each species and is correlated with the functional morphology of the distinctive spermatophoral organs.The existence of spermatophores, the non-primitive nature of the spermatozoa, and additional features of reproductive biology dictate that fertilization is internal in these species, but attempts to determine the means of sperm transfer proved futile. Reproductive potential and behaviour of male Phoronopsis, means of gamete segregation in Phoronis, and general pattern of reproductive biology for both phoronids were also studied.
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  • 5
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 121 (1967), S. 241-254 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The middle ear and the cochlea have been described in 20 representatives from the superfamily Phyllostomatoidea of the suborder Microchiroptera. Various measurements have been made and the results compared by means of graphs. The ultrasonic pulses used by these bats for echolocation have been recorded and analysed. Generally, the structure of the cochlea does not show extreme modifications as found in some other superfamilies that have previously been discussed.
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  • 6
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The study of the ultrastructure of the kidney tubules of the crocodile was made to compare the cellular structure with the capacity for electrolyte resorption and the ability to create an osmotic gradient across the tubular wall. The crocodile tubular cells were found to differ from the mammalian tubular cells in that they do not have basal infoldings, but instead have open lateral spaces between the cells, similar in many aspects to those found in the mammalian gallbladder. The physiological role of these lateral spaces in solute and fluid transfer is discussed.
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  • 7
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to follow the movement of cells involved in the proliferative response induced by wounding, changes in the cell population of three regions of normal and injured frog lens epithelium were studied with respect to DNA synthesis and mitosis using autoradiography following intraperitoneal injection of H-3-thymidine. The injured lenses comprised two groups: one subjected to labeled thymidine at 40 hours post-injury when the proliferative response begins, the other at 72 hours when the proliferative response is at its peak. Lenses were fixed at increasing intervals after injection.The data show that a central injury initiates proliferation in a large number of cells; this response appears at first mainly among the cells in the outlying proliferative (pre-equatorial) zone, as judged by the number of labeled nuclei and mitoses seen there in the first few hours after injection in the 40 hour preparations. At later intervals labeled cells and mitoses appear centrally adjacent to the wound. And in the 72 hour preparations, the greatest concentration of reactive cells is adjacent to the wound. There is also thinning out of labeled cells in the proliferative zone and greater dilution of exposed emulsion grains over nuclei adjacent to the wound with time, suggesting that outlying cells migrate centrally, dividing en route. However, interpretation of these data is limited by the finding that H-3-thymidine injected intraperitoneally into the frog is not cleared rapidly from the circulation; the serum after 24 hours retains about 20% of the radioactivity (measured by scintillation counting) present at 15 minutes post-injection.
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  • 8
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study, the condensation of the three thoracic and 11 abdominal segmental ganglia to form a prothoracic and central nerve mass during embryogenesis is described. During katatrepsis, many changes occur in the organization of these ganglia; this study suggests that some of these changes are caused by mechanical forces acting on the ventral nerve cord at this time. The ventral nerve cord begins its anterior migration and coalescence ten hours after katatrepsis and is completed 63 hours later. The central ganglion is made up of the meso- and metathoracic ganglia and seven abdominal ganglia. Intrasegmental median cord nuclei are shown to form glial elements in the median sagittal plane of the neuropile and in the longitudinal connectives. Intersegmental median cord neuroblasts migrate into the posterior gangliomeres but, apparently, degenerate soon after katatrepsis. Lateral cord cells bordering on the neuropile form a glial investment that surrounds this fiber tract region. Peripheral lateral cord cells are shown to form the cells of the outer ganglionic sheath, the perineurium.
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  • 9
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 122 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 10
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Five types of sense organs have been found on the antennal flagellum of Forficula auricularia Linnaeus: (1) tactile hairs; (2) long, thick-walled chemoreceptors; (3) short, thick-walled chemoreceptors; (4) thin-walled chemoreceptors and (5) coeloconic chemoreceptors. Earlier workers have placed the first three of these in a single class. The structural characteristics and distribution of these five kinds of sensilla on the antenna are described. All of the types except the third have been reported previously for other species but short, thick-walled chemoreceptors have not been described before. They are remarkable for the presence of (1) a broad pad-Like structure that absorbs dyes readily at the distal end of the peg and (2) a spheroid body, over a micron in diameter, on the dendrite of each olfactory neuron at the point where it narrows to assume the structure of a cilium. The antennal sense organs of a few specimens of Chelisoches morio (Fabricius), Labidura riparia (Pallas) and Euborellia annulipes (Lucas) were also examined.
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  • 11
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 122 (1967), S. 115-130 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The origin of the internal carotid artery in the lizards Tiliqua occipitalis and Trachysaurus rugosus has been shown to be both extremely variable and complex. In the dense connective tissue investing the junction of the internal carotid artery and the summit of the carotid arch are groups of cells associated with sinusoids derved from arterioles arising from the neighboring great vessels. The conspicuous epithelioid cells in these groups resemble the mammalian carotid body glomus and amphibian α cells. Nerve fibers showing no obvious synaptic specializations pass to and over these cell groups. It is suggested that these cell groups and sinusoids are comparable to mammalian carotid body glomeruli. A similar group of cells has been described in the concavity of the summit of the fourth aortic arch. This cell group, however, gives a distinct chromaffin reaction.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 121 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 13
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 121 (1967), S. 179-207 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Detailed descriptions are presented of morphogenetic and histogenetic events occurring in the membranous and bony labyrinths, sensory areas, acoustic ganglia, and acoustic centers of the hindbrain of the chick embryo, stages 11 to 45. Major morphogenetic changes occur between stage 11 and stage 30. During this period primordial ganglionic neuroblasts are segregated from the otic epithelium and differentiate into the bipolar neuroblasts of the vestibular and cochlear ganglia, neuroblasts of the alar plate in the acoustic region of the rhombencephalon differentiate, migrate, and are organized into acoustic nuclei, and the otic cup closes to form a vesicle which undergoes complicated structural changes to become a labyrinth. Morphological events in neural structures are closely followed by structural changes in the labyrinth. Minor morphological changes continue to occur through stage 44. The histogenetic period, stage 26 to 38, is the same for all parts of the acoustic apparatus. Minor histogenetic events occur up to hatching. In this period, differentiation of ganglionic and central neurones precedes differentiation of sensory cells.
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  • 14
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 122 (1967), S. 19-33 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ovary in Callosobruchus analis consists of telotrophic ovarioles with the so called nurse cells confined to one chamber at the anterior end of the ovariole. There are three types of lipids in the ovary: (1) L1 bodies that are present in the early oocytes, in the posterior prefollicular tissue and in the follicular epithelium and contain unsaturated phospholipids; (2) L2 bodies that have a complete or incomplete sheath of phospholipids and a triglyceride core; (3) L3 bodies that are formed of highly saturated triglycerides. Lipids are absent from the trophic tissue. In a mature oocyte the L1 and L2 bodies are cortical in distribution while the L3 bodies are centrally located.The mitochondria contain lipoproteins with RNA. The yolk spheres are acid mucopolysaccharides and protein in nature. The precursors of the yolk spheres appear first in the cortical coplasm and are absent from the follicular epithelium or the trophic tissue. The nucleolus of the oocyte shows evidence of extrusions that are believed to pass into the ooplasm.There are no nutritive cords connecting the trophic tissue to the oocytes; nor is there any evidence of any histochemically demonstrable nutritive material being contributed to the oocyte by the trophic tissue. The circumstantial evidence points towards a contribution of the raw materials to the oocyte by the haemolymph either through or in between the follicular epithelium in some soluble form or as submicroscopic particles.
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  • 15
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Parenteral administration of methylcellulose causes massive splenomegaly and hemolytic anemia in rats. The red pulp of the spleen is markedly cellular due mainly to: (1) large numbers of voluminous free macrophages containing methylcellulose-induced vacuoles, (2) an increase in the number of plasma cells and (3) stasis of blood evidenced by a large number of erythrocytes and platelets in vessels, sinuses and cords. White pulp changes are usually less marked. Here the major change is the presence of macrophages containing methylcellulose-induced inclusions. The slow circulatory time in the spleen and the increase in macrophages may cause the hemolytic anemia observed in these animals.
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  • 16
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The squirrel monkey uterine cervix was studied macroscopically and microscopically in intact and ovariectomized monkeys. The effect in ovariectomized monkeys of estradiol dipropionate or progesterone of both given after estrogen priming was studied by PAS staining.The lower portion of the cervix was dilated to form a vestibule into which projected fibromuscular colliculi which arose from the isthmic end of the cervix. The stratified squamous epithelium of the vagina was continuous through the external os with a similar epithelium lining the vestibule and covering the external surfaces of the colliculi. The transitional zone between the stratified epithelium and columnar cells was variable. The colliculi were covered internally with mucosal folds of columnar epithelium continuous with those of the endocervical canal.Glycogen concentration in the smooth muscle did not fluctuate markedly, irrespective of the hormones used. Glycogen granules were more numerous in the stratified squamous epithelium. Malt-diastase-resistant material appeared to be more abundant in the columnar epithelium and glandular lumina when the monkeys received both hormones than when they received solely estrogen or progesterone.
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  • 17
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A detailed gross anatomical study of the innervation of the respiratory muscles was made on twenty mature, male, Single Comb White Leghorn chickens. The aim was to demonstrate the general pattern and degree of terminal branching of the intercostal and lumbar nerves that innervate respiratory muscles.The point of entry for all nerves was on the medial face of the proximal third of the belly of the muscles, except for the transversus abdominis and costopulmonary muscles. The nerves were not always accompanied by blood vessels at the point of entry but both were invariably related at their terminal branches within the muscle belly and the tendon or aponeurosis. Within the muscle, primary, secondary, tertiary, and quarternary subdivisions of nerves coursed parallel to the muscle fibers, but some were tortuous. Plexus formation and/or segmental nerve anastomosis was most evident in strongly active expiratory and inspiratory muscles, i.e., all abdominal muscles and the m. costisternalis pars major.A craniocaudal gradient in the size and development of the contractile mass of the intercostal muscles was observed. The mm. intercostales interni increased in size in the caudal intercostal spaces, while the reverse was true for the mm. intercostales externi. Variable forms and sizes of lateroventral abdominal muscles were observed and the m. rectus abdominis was consistently present.The mm. intercostales interni and externi received branches from both the nn. intercostales interni and externi.
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  • 18
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 123 (1967), S. 71-83 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ctenophore, Vallicula multiformis (V. multiformis) (Rankin), can reproduce asexully by segregating pieces of tissue from its periphery. These pieces of tissue then differentiate to form new individuals. In 99% of the cases the pieces of tissue form normal animals; however in 1% of the cases they form “half animals” which have only one set of tentacles (the animal normally has two sets of tentacles). V. multiformis can also regenerate its apical organ, and one or both sets of tentacles.By cutting V. multiformis in half through the apical organ along the sagittal plane it is possible to produce “half animals” in 30% of the cases. “Half animals” can reproduce asexually. In 6% of the cases the new individuals which form from them differentiate as “half animals.” A part of a “half animal” that contains an apical organ will regenerate as a “half animal” while a part that does not contain an apical organ will regenerate as a normal individual. If one removes the apical organ from a “half animal,” it will regenerate it. A part of this animal containing the regenerated apical organ will regenerate as a “half animal.” If one removes the apical organ from a “half animal” and replaces it with the apical organ of a normal individual, the part containing the apical organ will regenerate as a normal individual. The results of these experiments are discussed in terms of possible mechanisms that control the process of regeneration.
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  • 19
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The venom glands of several species of elapid snakes are described. The main venom gland consists of many tubules which usually contain large amounts of secretion product. The accessory gland surrounds the entire venom duct and is usually composed of uniform mucous epithelium. The epithelium lining the tubules of the accessory gland of Naja naja is composed of two distinct types of cells. Histochemical tests indicate that the main venom gland reacts with mercury bromphenol blue and PAS but not with alcian blue. The accessory gland reacts with PAS and alcian blue, and not with mercury bromphenol blue. Treatment of sections with sialidase demonstrates the presence of a sialomucin in the accessory gland. Stimulation of the muscles associated with the venom gland offers an indication of the venom expulsion mechanism of Bungarus caeruleus. A comparison of the venom apparatus of elapid and viperid snakes emphasizes marked differences in the internal anatomy of the venom glands, muscles associated with the gland, and arrangement of glandular components. The morphological differences and dissimilar venom expulsion mechanisms support the recent view of the polyphyletic origin of venomous snakes.
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  • 20
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 123 (1967), S. 441-461 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An electron microscopic study of the functional mesonephros in the 8-day chick embryo revealed the following features of the nephron:Proximal tubule cells. Nuclei are spherical and basally oriented. Mitochondri are round or elongate with clear-cut cristae. Intramitochondrial granules occur sporadically. The Golgi complex, lying adjacent to the nucleus in apical cytoplasm, consists of flattened lamellae and associated secretion droplets. The cytoplasm is filled with ribosomes which occasionally are spiral in arrangement. Characteristic microvilli project from the apical end of cells. Basal regions of the cells are bounded by a homogeneous basement membrane. Adjacent epithelial cells are separated at their base by wide intercellular spaces. Interdigitating processes between cells are common in this area. At their apices, cells are joined by junctional complexes.Distal tubule cells. Nuclei are round and centrally located. Microvilli are sparse and usually absent. When present, they are short and blunt. Cells are closely allied at their base and joined tightly at their apices. Interdigitating processes are not as prevalent as in proximal tubules. Infoldings of the plasma membrane are prominent and compartmentalize mitochondria.Glomerulus. Endothelial cells are elongate, bordering the capillary lumen, and their membranes contain definite slit-pores. Epithelial pedicels extend from the cell body, intergiditate with each other and rest on the capillary basement membrane. The latter consists of three layers resembling those in adults.The similarity in the fine structural characteristics between chick mesonephros and adult metanepros corroborates the holonephric theory of vertebrate kidney evolution.
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  • 21
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The forms of the tectorial membrane and its connections to the ciliary tufts of the hair cells have been studied in detail in 18 species of lizards and, less thoroughly, in three others. This group, which represents eight lizard families, exhibits three forms of tectorial membrane: a complete form that connects to all parts of the auditory papilla, an abbreviated form that makes this connection only in one limited region of the papilla, and a dendritic form in which the distal portion of the membrane subdivides into strands reaching all the hair cells.Sometimes the tectorial membrane connects directly with the tufts of the hair cells, but more often it makes this connection through intermediary structures. Seven types of such intermediary structures have been identified (if we include the sallet, which is not “intermediate” in a strict sense).Detailed descriptions are given of the various forms of tectorial membrane structures and their variations along the auditory papilla in 12 lizard species. The description for Iguana iguana is offered as representative of the iguanid pattern found in ten members of this family.Consideration is given to the functioning of the tectorial membrane, and also of the sallet, in the process of hair-cell stimulation.
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  • 22
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: There were no lymphatic vessels and lymph nodes demonstrable in adult and larval Rana catesbeiana by a method that adequately demonstrated the same in mammals. Although the parenchymal arrangement in the lymphomyeloid organs is not exactly the same as in mammalian hemal nodes, nonetheless the vascular patterns of the lymph glands and jugular bodies are prima facie evidence that they function as blood-filtering organs among other probable functions. The vascular pattern of the lymph gland is that of a rete mirabile, particularly a venous portal system, inasmuch as the afferent and efferent vessels are venous in character and interposed between them is a labyrinth of sinusoids. This is not the case, though, in the adult organs. The vascular pattern of the jugular bodies is very much like the spleen, viz., artery-capillary-sinusoid-vein sequence. It is doubtful, however, if the propericardial and procoracoid bodies ever filter blood, because the smallest blood vessels in them are capillary in type Because of the absence of a well-defined capsule in some parts of the propericardial body, similarly to lymphoid follicles, especially in the mammalian gastrointestinal tract, it is probable that it filters tissue fluid. The last two organs are apparently mainly blood cell-forming organs. It is inferred from the vascular connections of the larval and the adult lymphomyeloid organs that they are not genetically related. This aspect was analyzed from earlier developmental data, but actual follow-up of the larval organs to the adult stage is still in progress.
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  • 23
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    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1327-1328 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 24
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 23-35 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyacrylamide having a fluorescent residue at the chain end was prepared by polymerization of acrylamide in the presence of a fluorescent dye. The segmental motion of the chain end in dilute solution was studied by the fluorescence polarization method on the fluorescent polyacrylamide conjugates thus obtained. The linear relation between 1/p and T/η0 held for every sample studied in aqueous media, where p is the degree of polarization of the fluorescence, T is the absolute temperature, and η0 is the viscosity of the medium. The mean relaxation time 〈ρ〉 of the conjugate was evaluated from these data as a function of the molecular weight of the conjugate. The value of 〈ρ〉 increased slightly with molecular weight, varying from 3.3 × 10-9 to 7 × 10-9 sec. The absolute values of 〈ρ〉 and its molecular weight dependence suggest that 〈ρ〉 represents the mean rotational relaxation time for the cooperative motion of about ten monomeric units at the chain end. The effect of the mean extension of polymer chain on the segmental motion was found to be negligible.
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  • 25
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 37-45 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescence polarization method has been used to study the micro-Brownian motion of a terminal segement of a polymer chain in concentrated solutions. A new apparatus for determining the fluorescence intensity and its polarization degree was designed. By using this apparatus, the rotational relaxation time 〈ρ〉 of the terminal segment of the fluorescent conjugates of polyacrylamide in aqueous polyacrylamide solutions was obtained as a function of polymer concentration from 0 to 65%, molecular weight of the conjugate from 3.5 × 104 to 3 × 105, and temperature from 10 to 30°C. The logarithm of 〈ρ〉 increased approximately linearly with increasing polymer concentration. This increase in 〈ρ〉, amounting to a factor of 20 times, was less marked than that in macroscopic viscosity. At concentrations less than 30%, 〈ρ〉 depended appreciably on the molecular weight of the conjugate.
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  • 26
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 47-61 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyethylene networks were prepared by γ-irradiation of linear polyethylene, both molten and crystalline. The elastic and photoelastic properties of the networks were studied at high temperatures, i.e., in the molten state. The equilibrium swelling was also measured in several solvents. Values of the crosslinking efficiency G of γ-radiation, the molecular, weight Me between entanglements, the optical anisotropy α of the equivalent random link, and the polymer-solvent interaction parameter μ are deduced. Samples prepared by irradiation in the amorphous state showed markedly non-Gaussian elastic behavior. The presence of a large non-Gaussian term in the optical anisotropy is also deduced. The value of α obtained for swollen samples, which showed substantially Gaussian elastic behavior, was 3.9 × 10-24 cm.3, about one-half of that obtained for dry samples. It corresponds to an equivalent random link of only about 5 CH2 units, on the basis of Denbigh's values for bond polarizabilities. The samples prepared by irradiation in the crystalline state showed lower values for α, which also depended upon the degree of crosslinking. This is attributed to the nonrandom chain configurations prevailing at the time of crosslinking. The same samples were found to show more nearly Gaussian elastic behavior, which is attributed to the same cause.
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  • 27
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 63-81 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Detailed structure analysis of the polyoxymethylene molecule was carried out by the method of three-dimensional Fourier synthesis. The diffraction data were measured on a highly ordered polyoxymethylene sample prepared from a single crystal of tetraoxane by solid-state radiation polymerization. By assuming the anisotropic thermal factors for the oxygen and carbon atoms and taking into account the contribution of the hydrogen atoms, good agreement between the observed and calculated structure factors was obtained; the R factor is 8.8%. The distance between the oxygen atom and the helix axis r(O) = 0.671 A. is slightly shorter than r(C) = 0.691 A. The bond distance C—O = 1.421 A., the angle ∠COC = 112°24′, and ∠OCO = 110°49′. All the internal rotation angles of the skeletal bonds are 78°13′. It is deduced from the experimental results that each crystallite of polyoxymethylene is composed of only one type of helix, right-handed or left-handed.
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  • 28
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 83-87 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relation of the high-frequency elastic moduli of semicrystalline polymers to volume fraction crystallinity is correctly described by the Hashin-Shtrikman theory, without any disposable constants, as a function of the ratio of the modulus of the amorphous to that of the crystalline phase. Hence the (high-frequency) reduced modulus of semicrystalline polymers is largely a function of the temperature T/Tg. The importance of T/Tm for the modulus of the crystalline phase precludes the existence of a single universal reduced modulus versus temperature curve.
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  • 29
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 239-262 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The infrared absorption spectra of selected crystalline and noncrystalline bands were studied in bulk-crystallized specimens of linear polyethylene which encompassed the extremely wide density range of 0.92-0.99 g./cm.3. The analysis of the data obtained at room temperature yield degrees of crystallinity by infrared methods which are in very good accord with the values deduced from the density measurements. Studies of the infrared spectra as a function of temperature give fusion curves which are in agreement with those obtained by thermodynamic methods. However, in order to obtain these latter results cognizance must be taken of the large negative temperature coefficient of the specific extinction coefficients of the crystalline bands from room temperature to the melting point. The necessary data to account for this phenomena were obtained from studies of the spectra of the n-paraffin, C94H190, where molecular crystals are formed. Analysis of the two gauche bands, at 1352 and 1303 cm.-1, which are assigned to the noncrystalline regions demonstrate that for bulk-crystallized samples of lowest densities the intensity ratio at room temperature is identical to that expected from the pure melt at this temperature. The conclusion is thus reached that the noncrystalline regions in these cases and the pure melt are structurally very similar. For samples of higher density, where the crystallite size is comparable to the extended chain length, the intensity ratio of the two gauche bands is altered. This change could reflect a change in the sequential distribution of gauche bonds. This intensity ratio for crystals formed from dilute solution is very similar to that for the high-density bulk-crystallized material and indicates a similarity in structure of the noncrystalline regions in the two cases.
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  • 30
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 277-288 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To investigate the solution properties of polyethylene, which has the simplest structure of the vinyl polymers, experiments were made with a magnetically suspended equilibrium ultracentrifuge. Preliminary studies were carried out with a polystyrene-chloroform system at 25°C. and a polystyrene-methylcyclohexane system at 68°C. (which is close to the theta temperature) in order to check the difficulties involved in the flotation equilibrium in the former case and the high temperature measurement in the latter. However, no trouble was encountered in either system, and the results were discussed and compared with earlier results for polystyrene solutions. It was found that chloroform is a good solvent for polystyrene, and the measured weight-average molecular weight is somewhat smaller than the value obtained in a theta solvent. After overcoming some technical difficulties involved in studies at higher temperatures, we carried out experiments on polyethylene in α-chloronaphthalene at 130°C. The results are considered reasonable by comparison with results obtained by other methods. The sample employed, Marlex 50 of melt index 0.7, has a wide molecular weight distribution: i.e., Mz/Mw = 5.2 and Mz+1/Mz = 2.4.
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  • 31
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 289-300 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Accurate measurements of stress relaxation after steady-state flow have been carried out, in the Newtonian flow region, for a polystyrene and a poly(methyl methacrylate) melt, with a cone-and-plate rotational rheometer. From the stress relaxation σ(t) versus t curves the relaxation spectra H were calculated by means of the first approximation equation: \documentclass{article}\pagestyle{empty}\begin{document}$ H = - ({1 \mathord{\left/ {\vphantom {1 {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}} \right. \kern-\nulldelimiterspace} {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}\ln t $\end{document}. The shear stress-shear rate curves, σ versus \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma } $\end{document} were also measured, in large ranges of shear rates, for the same melts, and from these data the relaxation spectra H were obtained by means of equations given by Faucher and Ferry. The Faucher equation, \documentclass{article}\pagestyle{empty}\begin{document}$ H = - \dot \gamma ^2 d{\sigma \mathord{\left/ {\vphantom {\sigma d}} \right. \kern-\nulldelimiterspace} d}\dot \gamma ^2 $\end{document}, has been found to give results which compare satisfactorily with those obtained from the first approximation equation. It has been found that the Ferry equation has to be modified for comparable agreement.
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  • 32
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 315-322 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of polydispersity on liquid-liquid phase equilibrium in systems containing polymer, solvent, and nonsolvent is investigated numerically in the Flory-Huggins approximation for several special cases. The resulting phase diagrams indicate that, except in the immediate vicinity of the critical region, the degree of swelling of a polymer precipitate phase with a given number-average molecular weight is essentially independent of polydispersity.
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  • 33
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 399-415 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The statistical mechanical treatment of polymeric chains in terms of the largest eigenvalue of the product of statistical weight matrices for the rotational interactions of skeletal bonds of the repeat unit becomes excessively complicated if the repeat unit spans more than three or four skeletal bonds. Moreover, such treatment is necessarily limited to chains in which the number of repeat units is indefinitely large. Newer methods are readily applicable to chains of any degree of polymerization comprising repeat units of any realizable length. If interdependence of neighboring bond rotations is confined to bond pairs within a given unit, rotations about a pair of bonds belonging to neighboring units being mutually independent, further simplifications may be introduced without sacrifice of rigor. Polyamides, in which rotation about bonds on opposite sides of the amide group are independent, are polymers of this type. Adherence of the amide group to the planar trans conformation favors a more extended configuration of the chain, but this effect is dominated by the smaller steric repulsions affecting rotations about bonds which are first, second, and third neighbors of the amide group. It is for this reason that the characteristic ratio 〈r2〉0〉/nl2 for poly(hexamethylene adipamide), ca. 6.0 according to experimental results of Saunders, is less than the value, 8.0, for polymethylene at 25°C. The characteristic ratios and molecular dipole moments are computed as functions of the degree of polymerization. The poly(εaminocaproamide) chain also is treated.
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  • 34
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 461-470 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Proceeding from the work of Zimm and Stockmayer and of Benoit, a general formula is derived for the calculation of the radius of gyration of block and graft copolymers. It appears that with linear block copolymers the ratio of the mean-square radius of gyration and the mean-square end-to-end distance is usually not far from 1/6. With a great number of blocks the difference from 1/6 can entirely be neglected. Also the influence of the composition of the molecules on the scattered light intensity has been considered.
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  • 35
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 639-652 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The primary reaction of oxygen with irradiated polyethylene has been followed by observing the rapid disappearance of the ultraviolet absorption bands at 258 and 285 mμ, bands attributed to the allyl and dienyl free radicals. A mathematical theory based on diffusion equations has been developed by means of which a quantitative estimate of the total initial free-radical concentration can be made. From the shape of the free-radical decay curve it can be concluded that the initial oxygen-free-radical reactions occur about three times as frequently in the amorphous regions as in the crystalline.
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  • 36
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 653-662 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aromatic poly(amic acids) derived from pyromellitic dianhydride and 4,4′,-diaminodiphenyl ether were characterized by dilute solution techniques. Number-average molecular weights M̄n of 13 samples ranged from 13,000 to 55,000 (DP 31-131). Weight-average molecular weights M̄w of 21 samples ranged from 9,900 to 266,000. The ratio M̄w/M̄n was between 2.2 and 4.8. Heterogeneous polymerization yielded higher molecular weight polymer than homogeneous polymerization. The molecular weight could be varied systematically by control of stoichiometric imbalance. Use of very pure monomers and solvent gave polymers of relatively high number-average molecular weight (∼50, 000) and the most probable molecular weight distribution M̄w/M̄n = 2. Impure monomers and/or solvent resulted in lower number-average molecular weight (M̄n ≅ 20,000-30,000) and wider distributions (M̄w/M̄n = 3-5). The Mark-Houwink relation obtained was [η] = 1.85 × 10-4M̄w0.80 The exponent is characteristic of moderately extended solvated coils. The unperturbed chain dimensions (r02/M)1/2 were 0.848 A., and the steric factor σ was 1.24 which is close to the limiting value of unity for an equivalent chain with free internal rotations. The sedimentation constant-molecular weight relation was S0 = 2.70 × 10-2M̄w0.39. This exponent is consistent with the Mark-Houwink exponent.
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  • 37
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 705-710 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent precision measurements of the heats of combustion of atactic and isotactic polystyrene permit an unequivocal calculation of the enthalpy difference in the bulk amorphous forms of the two isomers of this polymer. Contributions to this quantity arise mainly from the differences in nonbonded interactions in the two configurations but may also contain terms relating to higher energy conformations and to intermolecular interactions. The thermochemical and NMR data of specific polymers and of simple molecules are discussed in a comparison with model compound calculations. The thermochemical method has potentially important applications in studying molecular interactions in stereoregular polymers.
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  • 38
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The Tian-Calvet microcalorimeter has been used to measure the heat of solution of atactic polystyrene in toluene at 30°C. By using a special technique for polymer sample preparation, it has been possible to measure directly the difference in conformational energy of the polystyrene chain at different temperatures, from 30 to 100°C. and to calculate its contribution to the specific heat.
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  • 39
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 761-769 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The α, β, and γ transitions at temperatures between -200 and +100°C. of crosslinked aromatic and aliphatic epoxy polymers were determined from damping and shear modulus data, and compared with their fluorine containing analogs. Loci of segmental relaxation are suggested at various temperatures, and similarities between aliphatic and fluorocarbon segments, and polyethylene and polytetrafluoroethylene are discussed. Two systems of structurally similar monomers 2,2,3,3,4,4-hexafluoropentane diglycidyl ether-1,5 and 1,4-butane diglycidyl ether, and 2,2-bis(4-glycidyl phenyl ether)hexafluoropropane and 2,2-bis(4-glycidyl phenyl ether) propane were polymerized with the aid of two diamine curing agents, namely, ethylenediamine and m-xylylenediamine. Polymers of the aromatic diepoxides showed transitions with peaks at -56°C. and above +70°C. Three main peaks were registered for the aliphatic and fluorocarbon diepoxides: at -125 and at -100°C., at -56°C., and at 0°C. It is suggested that the Tg is affected by an interdependence of relaxation of all components of the polymer main chain.
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  • 40
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    Journal of Morphology 121 (1967), S. 1-18 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Catostomus macrocheilus, a sucker, and Poecilia reticulata, a live-bearer, are subjected to dissimilar mechanical stresses while most of their bony structures are forming. Osteogenesis occurs in the sucker when it is a free-living larva, whereas in the livebearer it occurs intrafollicularly. The first-formed bones ofboth species are those that meet functional demands and are subjected to the greatest stresses. These are the movable bones associated with the acts of respiration and feeding, and some of the axial bones. The cranial roof is the last to calcify. The primary differences in osteogenesis of the two species, such as in the vertebral column and caudal fin, can be correlated with differences in stress. Surface forces on calcifiable tissue perhapsassist in the deposition of calcium salts.
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  • 41
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: Histological serial sections of spleens from the adult raccoon (Procyon lotor) and woodchuck (Marmota monax) were processed for microscopic examination. Observations related to various aspects of the internal vascular pattern in the spleen of the raccoon and woodchuck demonstrated features that were characteristic of the respective animal. The spleen of the raccoon possess well-developed ellipsoid sheaths, whereas these same structures were not as prominent in the spleen of the woodchuck. The spleen of both mammals examined demonstrated the presence of an anastomosing series of venous sinuses within the red pulp tissue and may be classified as sinusal in nature.
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  • 42
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    Journal of Morphology 121 (1967), S. 19-28 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the column of hydra, tissues continually move away from a region located just underthe whorl of tentacles. Above this subtentacular region, tissues proceed into the hypostome and tentacles; below it tissues pass into the buds or continue down the stalk. These movements represent a steady state pattern of tissue renewal in which column growth is balanced by tissue loss at the body extremities. But the existence of a subtentacular zone in which tissue appears stationary does not necessarily indicate that growth is restrictedto this region, as is commonly stated.The body column of hydra can be viewed as an expanding cylinder whose elongation is balanced by tissue loss at the two ends. In such a body there must be one region from whichtissue appears to emanate, regardless of how growth is distributed along the cylinder. Only the rates at which tissues move will be characteristic of the underlying growthpattern. In Hydra littoralis, the measured rates of tissue movement down the gastric column are consistent with the distributions of mitotic figures, which indicate that growth is spread out along the column.
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  • 43
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    Journal of Morphology 121 (1967), S. 71-80 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Profiles of fresh chick lenses of 5, 8, 11, 14, 17 and 20 days embryological age were photographed and from tracings of these profiles, volumes were calculated using a formula for volume of a solid of revolution. Accurate volumes were also obtained by assuming the lens to be two half oblate spheroids of different minor axis, or, better, two half-solids of profile (x/a)k + (y/b)k = 1. In addition, the k in this equation described well the curvature of the lens profiles and thus provided a quantitative measure of developing lens shape. Lens diameter, depth and shift of equatorial diameter upon lens axis as a function of age were also studied.
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  • 44
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    Topics: Biology , Medicine
    Notes: Ductuli efferentes in four examined genera of family Didelphidae are organized into highly convoluted tubules, located within a conical body adjacent to the vascular plexus supplying the testis. They have yellowish-green color in the adult Didelphis virginiana and grey pink color in other genera. The ductuli efferentes in all examined animals are lined by very low columnar cells, covered by microvilli or booth cilia and microvilli.Histochemical analysis reveals several types of cytoplasmic granules in the genera examined. A single sperical body about 1.5 μ in diameter is found in epithelial cells of the four eyed opossum (genus Philander); this body stains positively for RNA and non-histone protein, and appears granular under the electron microscope, without a limiting membrane. Abundant cytoplasmic bodies in the Virginia opossum show strong reactions for SH groups; these granules may be responsible for the green color of the ductuli in this species. Ultrastructural studies show that the morphology of membrane limited granules in the ductuli of the examined genera is characteristic for each genus. Abundant pinocytotic vacuoles in the apices of these cells and a strongly positive alkaline phosphatase reaction suggest a marked absorptive activity of epithelial cells.
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  • 45
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: The fine structure of the nerve cell types in the white planarian Procotyla fluviatilis were described. Ganglion cells comprise the major portion of the brain. These cells are irregular in shape with several cytoplasmic processes and contain ribosomes, a sparse endoplasmic reticulum, microtubules, lysosomes, and a Golgi apparatus with numerous small vesicles. Granule-containing cells are situated in the peripheral regions of the brain and along the nerve cords. These cells contain ribosomes, rough-surfaced endoplasmic reticulum and a Golgi apparatus with associated dense granules. The granules occupy most of the cytoplasm and are ∼ 750A in diameter with moderately dense contents, ∼ 750A with opaque contents, and ∼ 1000A with contents of medium density. These granules are similar to those in the nervous systems of higher animals that contain epinephrine, norepinephrine, and neurosecretory substance, respectively. Each cell contains predominantly one type of granule although there is some intermixing of granules and intermediate types between the three most abundant granules. Small clear vesicles, resembling cholinergic synaptic vesicles, and all types of dense granules occur in the neuropil and within nerve endings.
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  • 46
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    Journal of Morphology 122 (1967), S. 169-173 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Histological examination of the fibrous and cellular connective tissue components of the periodontal ligament in the Caiman and the Alligator reveals the presence of reticular fibrillae, collagenic, elastic, and oxytalan fibers, as well as fibrocytes, osteoblasts, cementoblasts and epithelial rests. The oxytalan fibers differentiated by the peracetic acid aldehyde-fuchsin method are most numerous in the coronal region, radiating from the primary cementum into the periodontal ligament a short distance. Oxytalan fibers in fewer numbers are found interspersed between the oblique and the horizontal principal fiber bundles. Inasmuch as the crocodilian teeth have continuous replacement and thus a relatively short functional life, the oxytalan fibers of the Caiman and the Alligator appear to be proportionally fewer in number than they are in the mammalian periodontal tissues. The presence of the oxytalan fibers and epithelial rests in the Order Crocodilia (Crocodilia) adds to the number of dental structures shared with the Class Mammalia (Mammalia) (mammals) such as a stellate reticulum, a primary and secondary cementum and a periodontal ligament. This furnishes additional histological evidence for evaluation of the phylogenetic position of this group.
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  • 47
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Histochemical methods, especially azo dye methods for detecting acid phosphomonoesterase activity were applied to normal, regenerating and denervated, amputated limbs from larval Amblystoma maculatum. Efforts were made to control inactivation of enzymic activity and diffusion of both enzyme and reaction product. “Base-line” values for enzymic activity were determined for normal limbs. Activity appeared most intense in macrophages, less intense in epidermis and cartilage matrix. Some activity was detected in Schwann cells, peri- and endoneurium and muscle fibers form normal limbs. Enzymic activity in regenerating limbs was strongest within macrophages which appeared in increased numbers especially in early stages. Wound tissue showed little increased activity. As the blastema formed, increased enzymic activity was detected in epidermis and within increased numbers of macrophages. Chondrocytes showed increased activity especially during cartilage matrix deposition. Amputated, denervated limbs showed large numbers of active macrophages beneath and within epidermis and along muscle. As regression commenced, areas of cartilage matrix breakdown showed increased enzymic activity but, in general, greatest activity was in macrophages. The various possible roles of acid phosphomonoesterase activity in the specific biological situations dealt with are considered in light of such observations.
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  • 48
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    Journal of Morphology 122 (1967), S. 249-263 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Adult newts, Triturus viridescens, were treated with from 1.0-10.0 μg/g body weight of actinomycin D one day before amputation of both forelimbs. Mean survival times ranged from over 50 days in newts treated with 1.0 μg/g to 13.2 days in animals given 10.0 μg/g body weight of actinomycin. Low doses little altered the course of regeneration, but animals treated with over 2.0 μg/g never formed blastemas. In another series, animals were given doses of 2.5 μg/g body weight of actinomycin D at intervals from 14 days before to 30 days after amputation. It was found that certain signs of toxicity (loss of equilibrium) are related to the time of administration of the drug whereas others (hemorrhage into the limb stumps) are restricted to a definite phase of the regenerative process. Early administration of actinomycin completely inhibits regeneration whereas later treatment results in a considerably lessened effect. The postamputational stages which are basically destructive in nature are not noticeably affected by actinomycin D, but the phases of dedifferentiation, blastema formation and redifferentiation are strongly inhibited.
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  • 49
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    Journal of Morphology 122 (1967), S. 345-365 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The major events associated with the morphogenesis of the amphibian alimentary tract are described and illustrated with a series of photomicrographs that present a continuous account of the differentiation process from its onset at stage 38 until the initiation of feeding at stage 46. Histological evidence is presented for the normal disappearance of the midgut region of the archenteron and the de novo formation of the intestine through the yolk mass. The mechanics of intestinal lumen formation are discussed in terms of the dynamic autonomous actions and interactions of the endoderm and the splanchnic mesoderm. The opening of the intestinal lumen as a consequence of cytolysis or cellular digestion is discounted. The relation of the present observations to the previously described polar endoderm cells is considered.
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  • 50
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    Journal of Morphology 123 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 51
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The bullfrog, Rana catesbeiana, possesses lympho-myeloid and epithelial structures that are morphologically similar in some respects to lymph nodes of mammals. These organs are present during the entire life cycle of the frog, however, the structures that are present during larval stages do not appear to be morphological precursors of adult organs. According to certain terms used previously by other investigators, two major organs are present throughout the larval stages: the lymph gland and the ventral cavity body. In the adult, the jugular body, the epithelial body, the precoracoid and propericardial bodies are found in the ventral neck region in contrast to the lateral and ventral arrangement of the lymph gland and ventral cavity body in larvae. The function of these organs is not known but it is believed that they play a role in the production of certain blood cells, particularly lymphocytes, and they may be involved in some aspects of the differentiation and maintenance of the immune response capacity.
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  • 52
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The morphology and possible functional significance of cytoplasmic filaments associated with herpes-like viruses of the frog renal carcinoma is described. Filaments, invariability arranged in elongated bundles or sheaths, individually measure approximately 30 mμ in diameter, and are composed of finely granular, proteinaceous material. During the viral maturation sequence, this material is believed to be deposited on the surface of the capsid, thereby possibly providing the virus with a defensive coating prior to ergression from the cell.
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  • 53
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    Journal of Morphology 123 (1967), S. 109-119 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of Stannius corpuscles in the teleost Colisa lalia is described. Certain cells of the mesonephric tubules differentiate and proliferate to form buds which evaginate and finally become separated from the structure of origin. The separated cellular masses undergo further histologic differentiation to attain the adult structures.The corpuscles in C. laha, in contrast to some other teleosts, develop only from mesonephric tubules. A possible explanation for the different types of distribution of Stannius corpuscles in teleosts is suggested, and the possible homology of these structures with part of the adrenal cortex or higher vertebrates is discussed.
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  • 54
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    Journal of Morphology 123 (1967), S. 157-171 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the epidermal generations throughout the sloughing cycle of Anolis carolinensis is essentially the same as that described for other squamates, whether studied in control or hormone-injected animals. Readily identifiable granules in the clear layer of this and other lizard species emphasize the eventual hardening of this layer prior to its separation from the subjacent Oberhautchen, which brings about sloughing. Eosinophils are described for the first time in the lacunar tissue of lizard, but their functional role remains problematical. Daily 25 μg injections of prolactin (alone or in combination with gonadotropins) raise the frequency of sloughing by shortening the resting phase as compared with controls and animals receiving 1.0 I.U./day injections of gonadotropins. The duration of the proliferation-renewal phase and the pattern of histological changes occurring therein is unchanged by experimental treatments. The results show that neither endogenous nor exogenous gonadotropins affect the sloughing frequency, but exogenous prolactin produces a similar effect to that described for thyroxine. Although the mechanisms of action are unknown, the results provide another example of the cutaneous action of prolactin in vertebrates.
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  • 55
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    Journal of Morphology 123 (1967), S. 559-567 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Hemolymph cells of Orconectes virilis were stained during the months of August to November by a variety of histological and histochemical techniques. Cells were classified as hyaline cells, small granulocytes, and large granulocytes. Presence of mitochondrial enzymes was indicated by tests for succinic dehydrogenase and cytochrome oxidase. Reaction to test for the hydrolytic enzyme, leucine acylnaphthylamidase was intense in the granules of the large granulocytes. The PAS reaction indicated a mucopolysaccharide at the cell membrane. Lipid was found in all three hemolymph cell types of Orconectes virilis at the time of this study.
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  • 56
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The ultrastructural changes occurring during the differentiation of the pancreatic acinar cell were studied in White Leghorn chick embryos from the onset of pancreatic morphogenesis on day 3 of incubation (day 3) to hatching. Generally, the changes included a loss of some structures, the addition of others and modification of existing structures. Numerous cytoplasmic filaments which were present in the early migrating cells of the pancreatic bud were no longer present on day 5. The nucleoli enlarged temporarily on days 5-6 and then resumed a reduced size. The Golgi apparatus enlarged by day 6 and remained this way throughout the embryonic period. Associated with these changes was the initial appearance of the zymogen granules on day 5. The endoplasmic reticulum was present initially in both the smooth and the rough forms. The rough form and the outer nuclear membrane were both initially studded intermittently with aggregates of ribosomes. Subsequently, there was an increase in the number of attached ribosomes, an increase in the amount of rough reticulum and a decrease in smooth membranes. The ribosomes attached to the membranes appeared to augment the large free ribosome population characteristic of the early cells. Mitochondria did not appear to increase in number but there was an increase in size. The granules varied in kind, number and size with developmental age. The first granules formed (days 3-5) appeared to be miniatures of the mature type. Subsequently, a heterogeneity of granule morphologies was present.
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  • 57
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    Notes: The content and synthesis of ribonucleic acid (RNA) and protein was studied by microphotometry and autoradiography in the developing pancreatic acinar cells of White Leghorn chick embryos. These findings were correlated with previously reported changes in ultrastructural components. Shortly before or concomitant with zymogen granulation, RNA synthesis increased, in association with increases in the amount of nucleolar and cytoplasmic protein. The cytoplasmic fraction was transitory, whereas the accumulated nucleolar protein was maintained and was soon followed by an increase in nucleolar RNA. Concomitantly, a decrease in chromosomal RNA was observed, with the total amount of nuclear RNA staying constant. When zymogen first appeared, nucleoli were greatly enlarged due to large amounts of RNA and protein; total cellular RNA and protein had decreased slightly, in association with a decrease in cell volume. Subsequent development presented smaller nucleoli with decreased amounts of RNA and protein. Total cellular RNA increased due to its accumulation in the cytoplasm, probably as ribosomes. The accumulation of zymogen and the enlargement of other cellular structures contributed to an increase in total cellular protein. Prior to hatching, total cell RNA and protein decreased in amount, probably due to a reduction in cell volume through cell division.
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  • 58
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    Journal of Morphology 123 (1967), S. 213-230 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Seventy-seven hearts from one species of bat, Eidolon helvum Kerr, have been examined as a preliminary step in correlating cardiac form the and function in relation to flight in mammals. The supposition is that the heart, like the upper limbs and pectoral girdle, will show deviations from the common mammalian plan because of the animal's unusual way of life.The first thing that happens in flight, as in any form of exercise, is an immense increase in venous return to the heart. The architecture of the sinus venarum of the right atrium and of the right ventricle in the region of the atrioventricular valve, including the position of the papillary muscles, may be related to prevention of rapid overdistension of the right side of the heart. The walls of the inflow and outflow tracts of the right ventricle are exceptionally smooth, an anatomical feature that may have significance in that friction may be reduced. The left side of the heart resembles that of other mammals more closely.
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  • 59
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    Notes: We have examined the fine structure of injured, repairing and regenerating tissues of the amputated forelimbs of the adult newt: observations were made on wound epithelium, nerves, striated muscle, the regeneration blastema, connective tissues and cartilage.The wound epithelium shows little modulation from the adjacent epidermis: a subjacent glycocalyx and hemidesmosomes are initially absent. Some cells reveal phagocytic activity. As regeneration progresses, a glycocalyx, hemidesmosomes, and an adepidermal reticulum of fibers develop.Nerve fiber degeneration and regeneration lie side by side in the same nerve bundle. Myelin degeneration is evident within 24 hours; neural connective tissues loosen and fibers appear to spread apart.Striated muscle fibers display a nonuniform response to trauma, due to unequal degree of injury inflicted by amputation. The moderately and greatly injured fibers lose their distal fibril organization. There is a numerical increase in mitochondria, and occasionally a pyknotic nucleus is present. The myofiber glycocalyx appears to resist destruction, even when cell degeneration is extensive. Satellite cells have been observed intimately in contact with injured myofibers. Myogenesis is accompanied by an increase in collagen fibrillogenesis associated with adjacent fibroblasts. Many of these latter cells appear to contain intracellular fibrils: the significance of these observations are discussed, and a basis for intracellular fibrillogenesis and tropocollagen accretion is proposed.The fine structure of the regeneration blastema cell agrees with the description offered by others for the adult newt limb regeneration.Early prochondral condensation of blastema cells is described briefly.
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  • 60
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1313-1316 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 61
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. i 
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    Keywords: Physics ; Polymer and Materials Science
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  • 62
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1-21 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Light-scattering, viscometric and osmometric studies have been carried out on dilute solutions of polycarbonate fractions both in a good solvent and in theta solvents. The data span the molecular weight interval 5 〈 10-3M 〈 760. It has been concluded that: (1) the overall behavior in dilute solution is consistent with a flexible chain conformation; (2) the ratio of the unperturbed mean-square radius to the molecular weight, or to the number of chain elements, is larger than commonly observed for vinyl polymers; (3) the ratio of the unperturbed radius to the radius calculated for a chain with free rotation about valence bonds has the unusually small value 1.3; and (4) the hydrodynamic behavior of the chain may reflect partical draining affects.
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  • 63
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 125-142 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Degradation of poly(ethylene oxide) (PEO) by violent stirring was studied in various solvents. The chain scission or the limit of the degradation was measured, and the effects of solvents, polymer concentration, stirring speed and degree of polymerization (DP) were investigated. It was found that the number of bonds broken per polymer chain was independent of the concentration but increased with the stirring speed and with decrease in the DP. The rate was much affected by the solvent used, being larger in a poor solvent. It was also found that the rate could be represented either by Jellinek's or Ovenall's rate equations, which have been applied to the ultrasonic degradation of polymers in solution.
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  • 64
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 165-177 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal expansion and dielectric relaxation of polyacrylonitrile were measured in the temperature range from -75 to 152°C. at frequencies from 30 cps to 3 Mc./sec. The thermal expansion curve and the temperature dependence of logarithmic relaxation time both show an inflection at 85°C. An x-ray study by Bohn reveals that this inflection comes from the thermal expansion of the paracrystalline phase of this polymer, and consequently the transition at 85°C. and the associated relaxation are ascribed to molecular motion in the paracrystalline phase. The relaxation strength increases with increasing temperature above this point. The transition is caused by freezing of the bending vibration of chains whereas the relaxation results from rotational vibration. The length of segments in this phase is roughly estimated to be ca. 100 A. by comparing the observed relaxation strength with the theory developed on the basis of the above considerations.
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  • 65
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 179-193 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to explain the observed nonvanishing limiting value of dynamic intrinsic viscosity of polymer solutions at ω = ∞ one has considered the necklace model with finite resistance to the rate of coil deformation introduced long ago by Cerf for the study of gradient dependence of intrinsic viscosity and streaming birefringence. The calculation need not take into account change of hydrodynamic interaction as a consequence of coil deformation because the experimental data are always either obtained at very low gradient or extrapolated to zero gradient so that in the experiment the macromolecule has the same conformation as in the solution at rest. The model indeed yields a finite [η]′ω = ∞ in good agreement with experiments on polystyrene in Aroclor. According to the theory [η]′ω = ∞/[η]0 decreases with increasing molecular weight as M-1 and M-1/2 for the free-draining and impermeable coil, respectively. The absolute limiting value [η]∞′, therefore turns out to be nearly independent of M, at least for small values of internal viscosity. From the observed value [η]∞′/[η0] one can obtain the coefficient of internal viscosity of the macromolecule. The value for polystyrene in Aroclor calculated from dynamic experiments on rather concentrated solutions is close to that derived by Cerf from streaming birefringence observations of polystyrene in a series of solvents of widely differing viscosity.
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  • 66
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 225-229 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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  • 67
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 301-313 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polarized infrared measurements were made on polymer samples to obtain the structural changes occurring during the orientation process. The absorbances of the infrared bands were measured by determining the three components of the absorbance. Two components were obtained directly with plane-polarized light while the third is obtained by tilting the sample and extrapolating. Corrections were made for machine optics polarization, sample birefringence, polarizer inefficiency, anisotropy of the index of refraction, and scattering from the film surface. Data are reported for polyethylene obtained from cold-drawn specimens as a function of draw temperature. Polyethylene exhibits no strain-induced crystallization as a result of the chain-alignment process. Annealing of the drawn samples reperfects the distorted crystals.
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  • 68
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 323-331 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusion coefficient of 1,1,2-trichlorotrifluoroethane (TTE) in a liquid polybutene was determined at 25°C. as a function of concentration over the range 1.0-19.5 g. TTE/100 cc. The diffusion coefficient increase with increasing TTE concentration, rising continuously from 3 × 10-8 cm.2/sec. at the lowest concentration to 15 × 10-8 cm.2/sec. at the highest. The magnitudes of the diffusion coefficients indicate that the diffusion mechanism for small molecules in polymeric media must afford vastly greater opportunities for diffusion than the Stokes-Einstein relation allows. Similarly, self-diffusion coefficients for the liquid polymer are much lower than the observed mutual diffusion coefficients. An explanation for this behavior is presented.
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  • 69
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 333-342 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of long-chain branching must be considered in gel permeation chromatography to evaluate the molecular weight polydispersity of branched polyethylenes. Osmotic molecular weights of fractions of branched polyethylene were correlated with elution volumes; weight-average and number-average molecular weights of a branched polyethylene were determined. Molecular weight changes on crosslinking polyethylene by ionizing radiation are accompanied by branching and cannot be simply interpreted by gel permeation chromatography.
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  • 70
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 343-360 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of detailed measurements of osmotic pressure, light scattering, and viscosity of poly(vinyl chloride) solutions are used to establish the molecular weight dependence of [η] and A2, to estimate the unperturbed dimensions of the poly(vinyl chloride) molecule, and to analyze critically the [η]-M correlations published hitherto.
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 391-393 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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  • 72
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 555-568 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A simple differential, isothermal calorimeter has been built to study the thermodynamics of interactions associated with a variety of polymer solution processes. The calorimeter is readily operated at temperatures ranging from ambient to about 200°C., temperature adjustments are rapid, and the apparatus is rugged enough to permit application to commercial process studies. Though less sensitive than microcalorimeters, it represents an attractive combination of satisfactory accuracy, speed, and flexibility of operation. The operation of the calorimeter is demonstrated by measurements of the heat of solution of sodium chloride in water and the heats of solution of various polyolefins in Tetralin and α-chloronaphthalene. The latter tend to confirm the presence of polymer aggregates in chloronaphthalene solutions below the thermodynamic melting temperature of the polymer.
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  • 73
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 583-596 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The optical and mechanical properties of poly(vinyl chloride) film were examined by observing both the stress and birefringence during stretching at constant rate, during relaxation at constant length and during a dynamic birefringence experiment. Experiments were also done by varying the temperature at constant length. The changes in birefringence are interpreted in terms of changes in negative distortional birefringence, changes in positive orientation birefringence, and possible reversible changes in birefringence with temperature arising from conformational changes in the polymer chain and changes in the contribution of birefringent crystals.
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  • 74
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 597-613 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of crystalline morphology of isotactic polypropylene crystallized from dilute solutions on its molecular weight and growing conditions and the mechanism of crystal growth were studied by electron microscopy and electron diffraction. Lathshaped lamellar crystals 150-300 A. in thickness are obtained from fractionated polypropylene powders of Mw (average molecular weight) = 600,000 and 240,000, but not from the samples of Mw = 82,000 and 44,000, by means of isothermal crystallization at 130°C. for 20 hr. in dilute α-chloronaphthalene solution (0.005 wt.-%). Precipitation of the fractionated polypropylene sample of Mw = 82,000 from a dilute solution of carbitol gives typical dendritic crystals under the same isothermal crystallizing conditions as mentioned above. The mode of chain folding in these crystals based on the orientation and the crystal structure of the lamellar crystals agrees with that proposed by Sauer, Morrow, and Richardson. From the morphological observations, the mechanism of growth pertinent to polypropylene lamellar crystals is presumed to be as follows: fibrils at first aggregate, then the molecular chains are folded to form small lamellae, and then these small lamellae accumulate compactly to grow to large, lath-shaped, lamellar crystals.
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 795-798 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 799-816 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The concentration of solvent in the gel phase of a swelling polystyrene-divinylbenzene copolymer bead has been measured as a function of the radius by optical interference techniques. It is found that an appreciable gradient exists even shortly after the core disappears. Results are presented for two cases: a very lightly crosslinked bead that exhibits negligible birefringence while swelling, and a more tightly crosslinked network in which the birefringence must be considered. It is also found that the refractive index of the unswollen bead is considerably less than that found by extrapolation from the swollen state; this effect is reasonable when the “free volume” in the bulk polymer is considered.
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 817-828 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dispersion of birefringence in oriented amorphous polymers is discussed. It is shown that for polystyrene, the birefringence can be considered as the product of an orientation function and a function of the wavelength of the light. This leads to a method for expressing the birefringence dispersion as a function that is characteristic of the polymer. This function is determined for polystyrene, and from it the birefringence at infinite wavelength is found to be 11% lower than that measured with the mercury green line (5461 A.).
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  • 78
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 829-838 
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular dimensions of polydipropylsiloxamer were studied by intrinsic viscosity measurements in toluene and in 2-pentanone. The relationships between the molecualr weight and the intrinsic viscosity were found to be: [η]25°C., toluene = 4.35 × 10-4 M0.58; [η]θ(10°C.), toluene = 1.09 × 10-3 M0.5; [η]θ(76°C.), 2-pentanone = 8.71 × 10-4 M0.5. This held reasonably well for molecular weights from 25,000 to 3000,000. The root-mean-square end-to-end length ratio, (r02/M)1/2 as calculated from the constant K, exceeds the free rotation value by approximately 100%. The disparity is greater than that found with polydimethylsiloxamer, indicating a lower degree of flexibility for the polydipropylsiloxamer. This is largely due to the short range steric interaction between near neighboring units of the chain. Gel permeation chromatography was also employed to demonstrate the lower degree of flexibility for polydipropylsiloxamer as compared with polydimethylsiloxamer.
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 839-852 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The present study is concerned with some network properties of polyurethane elastomers in which stability is acheived via physical crosslinkages such as microcrystallites or secondary bonding. The techniques of isothermal, thermo-, and photoelasticity have been used to gain better insight into the mechanisms which occur during the deformation of these materials. It was found that stable networks are obtained only after mechanical and thermal conditioning. The well-known stress lowering which is observed during the second deformation is manifested primarily in the entropy component of the retractive force. This implies that the stress lowering results from a reduction in the number of effective network chains and not from time-dependent effects or crystallinity changes. Depending upon the chemical structure of the material, both positive and negative energy components of the force have been found.
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  • 80
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 875-889 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An extension of the results of a previous to higher molecular weights is made. The viscoelastic parameters ηt, Je, τm, and Em are found experimentally through stress relaxation tests. The predictions of the Rouse-Bueche (RB) theory and its modified Ferry, Landel, Williams (FLW) form concerning the molecular weight dependencies of these perameters are compared with the data. It is found that the RB and FLW predictions are not rigorously obeyed.
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  • 81
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 891-898 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Living polystyrene was grafted on fractions of poly(methyl methacrylate) by an anionic grafting reaction. Unreacted polystyrene was separated by fractional precipitation. The composition of copolymer, i.e., the molecular weight of main chains and side chains, was determined. The influence of molecular weight and structure of graft copolymers on the intrinsic viscosity of solutions was examined. This may be expressed in the form [η] = KMagn. The dependence between a and n in this equation was established.
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  • 82
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 853-874 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In earlier work we have indicated a superposition principle for moderately concentrated mixtures (c ≲ 2/[η]) in good and poor solvents. By an examination of data on a number of vinyl polymers and cellulose derivatives in good as well as poor solvents, the validity of this principle is extended to concentrated solutions (c ≲ 50%). The characteristic concentration factor γ is proportional to M-a1 over the whole concentration range, with 0.47 ≤ a1 ≤ 1.10 being larger for good than for poor solvents, the result obtained earlier. Significant deviations from this relationship are noted in good solvents for those low molecular weights at which deviations from the usual intrinsic viscosity relationship occur. This may be related to the expansion factor of the polymer coil. On the basis of these results, the concentration and molecular weight dependence of the viscosity in the concentrated solution can be related to each other in terms of the parameter a1 and thus to thermodynamic characteristics. In this manner a bridge between the relatively dilute and concentrated regions is established. Currently used semiempirical expressions are analyzed in terms of these results. For the polystyrene-cyclohexane systems and θ - 9 ≦ T ≦ θ + 3, γ can be identified with the critical concentration for phase separation. Provided an “entanglement” concentration ce exists, in the neighbourhood of which the concentration dependence of the viscosity changes reapidly, γ can alternatively be shown to be proportional to ce, or ce ∝ M-a1. The temperature reduction scheme suggested earlier remains to be investigated.
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  • 83
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular weight M and concentration c dependencies of the zero-shear viscosity (η) were measured over wide ranges of M and c for concentrated solutions of linear and branched poly(vinyl acetate) as well as of polystyrene under θ conditions. The log η versus log M and log η versus log c curves for a given system can be superposed by the horizontal shift along the abscissa, giving smooth master curves. From the shift factors the ratio of two exponents β and α, which appear in the following equation, can be evaluated: η = K′(cρ)αMβ, where ρ is the density of the solution and K′ is a constant at constant temperature. The evaluated values of β/α for the systems under θ conditions are equal to or very close to 0.50 as was anticipated from the previous work. The above superposition method was also applied to available viscosity data, and it was found that β/α had a good correlation with a in [η] = KMa. This indicates that the individual molecules in concentrated solutions maintain the same individuality as in dilute solutions, and might be a positive support to the packed sphere model proposed previously by the authors. The effect of solvent on the molecular weight and the concentration dependencies of viscosity was also discussed.
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  • 84
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 915-927 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The homopolymer and many of the copolymers of N-acrylylglycinamide yield thermally reversible gels in water. These systems are uniquely suitable for studying synthetic photographic gelatin substitutes and for understanding the mechanism of the gelation process. Polymerization of N-acrylylglycinamide has been studied under a variety of conditions. The homopolymer is aggregated in dilute aqueous solution and probably molecularly dispersed in 2M thiocyanate solution. At concentrations of several per cent, in water, thermally reversible gels are formed whose melting points rise with increasing concentration and increasing molecular weight. The heat of gelation crosslinking has been calculated to be -8.8 kcal./mole of crosslinks. Introduction of small amounts of carboxyl groups into the polymer raises the melting points of the aqueous gels. The effect of various organic and inorganic reagents on gelation is presented. The ability to prepare copolymers which can be flocculated has been demonstrated as well as the usefulness of the monomer in certain types of photoresist systems. Copolymerization with acrylic acid and β-aminoethyl vinyl ether has been studied, and the r1 and r2 values for these systems have been calculated as well as Q and e values for N-acrylylglycinamide.
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  • 85
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1013-1028 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the species of counterion on the polyelectrolyte behavior and the conformation of poly-L-methionine S-methylsulfonium salts in aqueous solution was studied by viscometric, electrochemical, and optical measurements. The degree of binding of small counterions to charged polyions increases in the sequence: chloride ≲ bromide 〈 iodide 〈 thiocyanate. The conformations of chloride and bromide salts are independent of polymer concentration. On the contrary, iodide and thiocyanate salts indicate a conformational transition, probably from a random-coil conformation to an intermolecularly stabilized β-form, with the increase of polymer concentration. The results suggest the existence of a strong specific interaction between counterion and macroion in iodide and thiocyanate salt solutions at high polymer concentration.
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  • 86
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 991-1012 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Single-crystal preparations of polyethylene were treated with the selective oxidizing agent, fuming nitric acid. The degraded products were examined as regards layer thickness (by low-angle x-ray studies), chemical and weight changes, recrystallization and annealing treatments, and by broadline NMR, as part of a systematic investigation aimed at clarifying the nature of disordered material in single crystals. It emerges that there is a disordered-mobile region along the fold surface of the crystals in agreement with other parallel works along similar lines. In a more detailed analysis we can now decompose the nitric acid attack into components affecting the basal and side surfaces, respectively. Taking into account the recrystallization-annealing observations, we infer that the fold surface is heterogeneous with folds of more than one kind. These results were combined with a preliminary molecular weight distribution study by gel permeation chromatography. Taking into account all the available evidence, we are led to suggest a composite structure where surface looseness, coresponding to long loops and hairs, is superimposed on the more regular folded surface. This model is in the process of being tested. The problems concerning the assignment of a value to the amount of surface looseness are being discussed. In addition, a discontinuity in the thermal behavior of the crystals between 75 and 80°C. has been detected.
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  • 87
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1029-1042 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This paper is devoted to the determination of the number of intermolecular bonds in a polymer crosslinked according to the following process: (1) crosslinking in the usual isotropic state, (2) additional crosslinking of the strained primary network. The Flory equation for swelling in solvents has been modified in order to take into account the oriented state of the initial network at the time of secondary crosslinking. The combination of this equation with those relating the modulus of elasticity and the dimensions of the relaxed sample to the deformation of the primary network at the time of secondary crosslinking leads to different possible evaluations of the number of intermolecular bonds. Their significance is discussed. The equations thus established are tested with natural rubber samples vulcanized according to the above-mentioned process. The validity of the number of crosslinks thus calculated is discussed; a partial degradation of the primary network occurs during the second crosslinking. Its influence is taken into account by using the approximated equations proposed by Flory. The efficiency of the vulcanizing agent (TMTD) is consequently shown to be practically independent of the deformation of the primary network at the time of secondary crosslinking.
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  • 88
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1043-1053 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low-angle light-scattering patterns were obtained on ionotropic gels formed by the diffusion of Ca++ into a polygalacturonate sol. Near the sol-gel boundary, diffraction patterns were obtained which indicated organized structures with repeating units of 1100, 250, and 12.5 μ. Microscopic investigations confirmed that at this gel boundary capillaries run parallel to each other and perpendicular to the direction of diffusion. The diameter of capillaries was 12 μ while their length was in the 1000 μ range. Short interconnecting capillaries were about 200-300 μ in length. Inside the gel, in the more highly crosslinked parts, a disorientation occurs during the aging process with the partial disappearance of capillaries. However, at the gel-sol and gel-semipermeable membrane boundaries, the highly organized structures remain even during prolonged aging. The kinetics of the gel formation was also investigated.
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  • 89
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1061-1066 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Osmotic pressures of aqueous solutions of poly(diethylaminoethyl methacrylate) hydrochloride, in equilibrium with a precipitate of the un-ionized polybase, at various concentrations of polymer and NaCl in solution and at different values of pH are derived from emf measurements and the “cell” theory for polyelectrolytes. Single-ion activities are evaluated according to two procedures. The first is based on measurements with ion-specific electrodes versus a calomel electrode. The second makes use of a salt bridge, but assumes that the co-ions have activity coefficients equal to the mean activity coefficient of the salt in a polyelectrolyte-free solution of the same concentration. The results show that the calculated values of the osmotic pressures are consistent with those obtained by the exact integration of the Gibbs-Duhem relationship, when the first procedure is employed. If, however, the single-ion activities are evaluated by the second procedure, the osmotic pressures obtained are consistently lower by about 10%. These differences arise because the two methods yield different values of the activity coefficients of the single ions.
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  • 90
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1079-1086 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic strain-optical coefficient of low-density polyethylene is found to decrease with increasing frequency and increase with increasing temperature (at temperatures up to 60°C.). It is found that a series of curves representing the real, K′, and imaginary, K″, parts of the frequency variation of the strain-optical coefficient obtained at various temperatures up to 60°C. may be superposed by translation along the frequency axis. The temperature dependence of the shift factor corresponds to an Arrhenius type equation with an activation energy of the order of 25 kcal./mole. This may be compared with the similar value obtained by Takayanagi for the αc′ mechanical loss and with the dynamic x-ray diffraction values reported by Kawaguchi et al., but is somewhat lower than the value of 34 kcal./mole reported by Onogi et al. from birefringence relaxation studies. Takayanagi has ascribed the αc′ peak to cooperative motion of crystalline and amorphous regions of the sort that might be involved in the suggested sliding of lamellae over each other. At temperatures higher than 80°C., horizontal superposition is not possible.
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  • 91
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    Keywords: Physics ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The time-dependent birefringence has been measured simultaneously with the stress relaxation on quenched and annealed low-density polyethylene at various temperatures from 10 to 70°C. The strain-optical coefficient increases generally with increasing time, and approaches the equilibrium value, which depends upon the temperature. When the strain-optical coefficient at a fixed time is plotted against temperature, it first increases and then decreases after passing through a maximum at Tmax with increasing temperature. The higher the degree of crystallinity, the higher are the equilibrium values of the strain-optical coefficient and Tmax. The curves for strain-optical coefficient versus time and relaxation modulus versus time below Tmax can be superposed well by a horizontal shift along the abscissa. The optical shift factor obeys the original WLF equation, while the mechanical shift factor is much larger than the optical one. The molecular mechanisms corresponding to this dispersion of the strain-optical coefficient and viscoelastic αc absorption peak near Tmax are discussed.
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  • 92
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1145-1156 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theory of rate processes has been applied by Eyring to the plastic flow of solids, but he considers only the case of simple shear. Some assumptions concerning a generalization of this theory for an arbitrary strain tensor are here proposed and discussed. The components of the deformation and the work done by the deviator of the stress during the elementary flow process are evaluated. According to these results, it can be proved that the yield condition of Huber, Hencky, and von Mises is valid when there is no hydrostatic stress. The discrepancy between the yield stresses corresponding to tensile and compressive tests is explained by the influence of the hydrostatic component and evaluated by taking account of the amount of free volume required for an elementary jump. The calculated value agrees with the experimental data. Measurements of the inclination of Lüder's bands and deformation components on poly(vinyl chloride) flat bars strained by tensile tests are in good agreement with the proposed theory.
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  • 93
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1157-1175 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Equations are developed for predicting the distributions of degree of substitution and block length in substitution copolymers which result when homopolymers are subjected to substitution reactions. Several different cases are treated differing in complexity from entirely random substitution to substitution affected by substituents already present on the same and on the neighboring repeat units. The equations are then applied to chlorinated polyethylene as an example of their use.
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  • 94
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1177-1187 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanism of carbon black reinforcement was studied by examining stress-strain properties of preswollen (i.e., cured in the swollen state then deswollen) SBR-1500 vulcanizates and the effect of heat treatment on such samples. It was found that the supercoiling of molecular chains leads to a purely viscous response at low elongations. On heating of preswollen samples, molecular rearrangement at the carbon black surface occurs, leading to a considerable increase in modulus. The activation energy of that process was determined by using the superposition principle.
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  • 95
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The standard methods of measuring the elastic properties of polymer melts are briefly reviewed and a method of measuring another combination of viscoelastic properties, the melt strength, is described. Data are presented on the melt strength of various types of polyethylene resins and on ionomer resins. The effects on various viscoelastic properties of branching or of the addition of fine fibrils of Teflon perfluorocarbon resin are reported.
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  • 96
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1293-1295 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 97
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    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1283-1292 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of microstructure on crystallizability of polyoctenamers prepared by R3Al-WCl6 catalyst was studied. The results indicate that polyoctenamers with a broad range of trans-vinylene content do crystallize. The measured melting points are dependent on the trans-vinylene content. From the dependence of melting temperature on copolymer composition, a value of 73 ± 2°C. for the melting point and a molar heat of fusion ΔHu of 3520 cal./mole are calculated for 100% trans-polyoctenamer. From the melting point depression in the presence of diluent, a value for ΔHu of 4800 cal./mole is obtained.
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  • 98
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Current theories of polymer flow processes often sacrifice realistic molecular models for simplicity of their mathematical equations. An analysis of what might happen to molecules of more realistic sizes and shapes under shear flow, shows the importance of the rapid Brownian motion of chain segments, the elastic deformations of polymer random coils, and the dissipation of this elastic random coil energy by the relatively slow slippage of the chains past each other at a few entanglements where steric hindrance causes long relaxation times. This makes the energy loss depend on the time at each local deformation, and not on the overall shear rate. At high shear rates this model leads to “cluster flow” and low loss cyclic deformations, rather than the high loss processes of steady-state shear. This model gives reasonable qualitative explanations for many anomalous flow properties, and it has predicted new effects that have since been observed.
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  • 99
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    Journal of Morphology 121 (1967) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 100
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An electron microscope study of oocyte maturation in the mouse revealed that some mitochondria undergo gradual transformation in their ultrastructural appearance. In very young oocytes these mitochondria were already found to contain vacuoles, one in each such organelle. In somewhat older oocytes more mitochondria displayed vacuoles which generally appeared to be getting larger. These intramitochondrial vacuoles were found to be essentially optically empty structures surrounded by a single membrane. In favorable sections someof the developing vacuoles had a bottle-shaped appearance, the constricted end of which was attached to the inner limiting membrane of the mitochondrion. With further maturation of the oocytes vacuoles having a pear-shaped appearance became evident. An hypothesis was presented outlining the mode of formation of these vacuoles by expansion of the individual cristae. Intramitochondrial transformations occuring during both oogenesis and spermatogenesis in mammals were reviewed.
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