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  • 1970-1974  (91)
  • 1965-1969
  • 1890-1899
  • 1970  (91)
  • Computational Chemistry and Molecular Modeling  (64)
  • Electron microscopy
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Years
  • 1970-1974  (91)
  • 1965-1969
  • 1890-1899
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 132 (1970), S. 107-157 
    ISSN: 1432-0568
    Keywords: Differentiation ; Down feathers ; Electron microscopy ; Keratinization ; Keratohyalin granules ; Periderm granules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The morphology of the developing chick feather germ (down feather) was studied at the ultrastructural level from 8 to 18 days of incubation. The process of keratinization in the developing feather germ was described, discussed and compared to keratinization in mammalian skin and hair. This study has shown that: 1. Apico-basal gradients of differentiation and different cell types are recognizable at the ultrastructural level in the developing feather germ. 2. The hypothesis that keratin is synthesized de novo by ribosomes is probably correct, because the largest number of these organelles is present at the time when keratin formation is most prominent. 3. Intercellular gaps in the developing feather germs facilitate the reorientation and rearrangement of different cell types into definitive feather structures. 4. The sources of nutrition and energy for the completion of keratinization during later developmental stages of feather germs are the supportive and the barb medullary cells and large stores of glycogen. 5. Keratohyalin granules are not precursors of feather keratin, since no such structures were observed in feather germs. 6. Two distinct modes of keratinization occur in feather germs. Keratinization in sheath cells is similar to that which occurs in mammalian epidermal cells. Barb and barbule cell keratinization resembles that of hair. 7. The basal lamina is probably involved in transport of synthetic material from the pulp cavity to the epidermal cells. The lamina may also provide mechanically strong connections between the feather germ and the dermis. It is suggested that desmosomal tonofilaments provide a framework which orients the synthesis of keratin. It is also suggested that the periderm granules provide mechanically weak areas in the sheath and facilitate the fragmentation of this structure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 130 (1970), S. 216-233 
    ISSN: 1432-0568
    Keywords: Guinea-pig ; Placenta ; Syncytiotrophoblast ; Fetal capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wurde elektronenmikroskopisch die reife Hauptplacenta von 31 Meerschweinchen untersucht. Die Ergebnisse zeigen, daß das Organ aus, drei morphologisch unterscheidbaren Gebieten aufgebaut ist: Interlobär- und, Randsyncytium, Läppchenperipherie und Läppchenzentrum. Zwischen diesen Zonen befinden sich noch zwei Übergangszonen, die die Eigenschaften der angrenzenden Hauptgebiete haben. Das Interlobär- und Randsyncytium enthält keine fetalen Capillaren, besitzt, aber teilweise ein sehr gut entwickeltes endoplasmatisches Reticulum mit zum Teil parallel angeordneten Zisternen sowie vielen Einschlüssen und verschiedenartigen vacuolären Gebilden. Nach dem Vorkommen dieser Bestandteile unterscheiden wir vier unregelmäßig verteilte Syncytioplasmazonen: a) mit vielen Vacuolen, b) mit vielen Filamenten, c) mit Vacuolen und Filamenten und d)— am häufigsten — Gebiete, die fast frei von derartigen Strukturen sind. Der Trophoblast besitzt an der den mütterlichen Lacunen zugewandten Oberfläche viele Mikrovilli und unterschiedliche polypartige Gebilde. Die Läppchenperipherie ist reich an fetalen Capillaren. Die Trophoblastbalken sind dünn und zeigen unterschiedlichen Organellengehalt. Oft kommen viele Vesikel vor. Das endoplasmatische Reticulum ist um die mitochondrien angeordnet. Das Läppchenzentrum zeigt häufig eine vacuolisierte, netzartige Struktur. Im Syncytiotrophoblast sowie in den Endothelzellen werden ausgedehnte endoplasmatische Zisternen gesehen. Die Oberfläche der fetalen Capillaren besitzt viele polypartige Gebilde. In funktioneller Hinsicht wird das Rand- und Interlobärsyncytium mit der Proteinsynthese in Zusammenhang gebracht. Trotz des Fehlens embryonaler Gefäße können sich hier Resorptionsvorgänge abspielen (positive ATP'ase-Reaktion). In der Läppchenperipherie überwiegt möglicherweise der Austausch der Atemgase und niedermolekularer Substanzen. Das Läppchenzentrum scheint wieder in Beziehung zum Proteinaustausch und zum Lipidumsatz zu stehen. Es gibt Hinweise, daß über alle Placentazonen hinweg eine lebhafte Cytoplasmaströmung erfolgt.
    Notes: Summary The mature main placenta of 31 guinea-pigs was investigated by means of electron microscopy. It is shown that the organ consists of 3 morphologically different regions, i.e. interlobar and marginal syncytium, lobular periphery and lobular centre. Between these regions there are 2 transitional zones having the morphological characteristics of both adjacent main regions. The interlobar and marginal syncytium is devoid of fetal capillaries However, in some parts it has an extremely developed endoplasmic reticulum, in parts of which the cisternae are arranged in parallel. In addition it has many inclusions and various vacuolated structures. According to the presence or absence of these structures four irregularly distributed syncytioplasma zones can be distinguished: a) containing large numbers of vacuoles, b) containing large numbers of filaments, c) containing vacuoles and filaments and d)— the main group —regions which are almost entirely free from these structures. On the surface facing the maternal lacunae the trophoblast has an abundance of microvilli as well as various polypoid structures. The lobular periphery is rich in fetal capilaries. The trabeculae of the trophoblast are thin and show a varying of organelles. Frequently large numbers of vesicles are observed. The endoplasmic reticulum is arranged around the mitochondria. The lobular centre frequently shows a vacuolized net-like structure. Extensive endoplasmic cisternae are observed in the syncytiotrophoblast as well as in the endothelial cells. The surface of the fetal capillaries shows an abundance of polypoid structures. From a functional point of view it seems likely that the interlobar and marginal syncytium is involved in protein synthesis. Despite the lack of fetal capillaries, absorptive processes can take place in this region. It is suggested that the main function of the lobular periphery is exchange of the respiratory gases and of substances of low molecular weight. The lobular centre seems to be associated with protein synthesis and lipid turnover.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 10 (1970), S. 276-282 
    ISSN: 1432-1106
    Keywords: Chlorpromazine ; Rabbit hypothalamus ; Glycogen ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The tuber cinereum of hypothalamus, cerebral cortex, cerebellar cortex and caudate nucleus of rabbits were examined under the electron microscope following intramuscular administration of chlorpromazine with special consideration of ultrastructural changes in amount and distribution of glycogen granules in their hypothalamus. In these regions, normal astrocytes and their processes contain glycogen granules diffusely scattered in the cytoplasm. In the neurons of the normal hypothalamus and cerebellar cortex, glycogen granules are seen in some presynaptic endings and distal parts of dendrites but not in the perikaryal cytoplasm. In the tuber cinereum of the hypothalamus, after chlorpromazine administration, abundant glycogen granules accumulate at the postsynaptic sites, especially in peripheric parts of dendrites, and clusters of glycogen granules appear in the perikaryal cytoplasm of the nerve cells. These findings are interpreted as an increase of glycogen in these cellular regions and the suggestion is made that chlorpromazine inhibits the glycolytic metabolism in the distal parts of dendrites, particularly at postsynaptic sites and in the perikarya of nerve cells of the hypothalamus.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 11 (1970), S. 387-391 
    ISSN: 1432-1106
    Keywords: Trifluoperazine ; Rabbit pallidum ; Glycogen ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following administration of trifluoperazine (a psychotropic drug of the phenothiazine group), the brains of rabbits were examined by electron microscopy, with special reference to the glycogen changes in the globus pallidus, and were compared with the normal materials. After seven days' intramuscular injections of trifluoperazine (10 mg/kg/day), abundant glycogen granules were accumulated in dendrites of pallidum. Those animals showed extrapyramidal symptoms throughout the period. The administration of the drug might inhibit either neural activity or the glycolytic metabolism in dendrites of the pallidum.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 10 (1970), S. 1-16 
    ISSN: 1432-1106
    Keywords: Cerebral cortex ; Laminar lesions ; Degeneration ; Dendrites ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The morphological characteristics of dendrites in layers of the cerebral cortex above laminar lesions induced by ionizing particle irradiation have been studied in the striate field of rat at various survival times. Within two weeks following irradiation an increasing number of dendrites display unusual alterations inferred to be signs of degeneration. Degenerating dendrites can be characterized by a dense cytoplasmic matrix, disruption of mitochondria, presence of dense bodies, irregular outline and a marked alteration of the plasmalemma in its dimensions and staining properties. Some degenerating dendrites possess a large accumulation of dense subsynaptic material and are contacted by synapses with enlarged and altered synaptic clefts. A few dendrites contain extensive membranous whorls. Engulfment by reactive astrocyte processes is a common feature and often includes the presynaptic axonal knob, but only the degenerating dendrite has been observed within glial cytoplasm. The inference that the majority of degenerating dendrites in this material are apical dendrites of pyramidal cells suggests that either shaft synapses are common for these cells, protuberances may retract during degeneration, or spines are lost due to loss of afferent terminals.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 11 (1970), S. 528-538 
    ISSN: 1432-1106
    Keywords: Visual pathway ; Hypothalamus ; Arcuate nucleus ; Rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Degenerating nerve fibres and boutons were searched with the aid of the electron microscope in the arcuate nucleus of rats 2–7 days after bilateral destruction of the retina. In the arcuate nucleus of the control animals as well as in the operated animals, 4 types of boutons were distinguished on the basis of vesicular contents and glial ensheathment. In the operated animals changes interpreted as degenerating were found in small myelinated axons and boutons of type II (boutons containing both synaptic and granular vesicles). The changes were similar to those described in the literature as the “dark” type of degeneration in experimentally interrupted axons and boutons. Similar changes were not found in the unoperated animals. The conclusion is reached, that a small number of fibres of the optic tract reach the arcuate nucleus to terminate here.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 111 (1970), S. 316-345 
    ISSN: 1432-0878
    Keywords: Electron microscopy ; Histophysiology of median eminence ; Avian neurohypophysis ; Neurosecretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé Les effets de l'adénohypophysectomie et de diverses sollicitations de l'axe hypothalamo-hypophysio-corticosurrénalien sur l'ultrastructure de l'Eminence Médiane (E.M.) ont été étudiés chez le Pigeon. 1. Chez le Pigeon entier, l'Eminence Médiane Caudale (E.M.C.) se distingue de l'Eminence Médiane Rostrale (E.M.R.) essentiellement par l'absence dans les deux couches les plus externes (couches palissadique et superficielle) de l'E.M.C. de granules de gros calibres (1600 à 1900 Å), la rareté de granules de diamètre moyen (1200–1400 Å) et la prédominance de petites vésicules à cœur dense de 600–800 Å. 2. La préhypophysectomie entraine: a) dans l'E.M.R. la quasi disparition de granulations dans les deux couches externes; b) dans l'E.M.C. la ≪vidange≫ de nombreux axones, mais un enrichissement relatif, parmi les granulations restantes, des granulations de gros calibre (1600–1900 Å) aux dépens des granules de plus petit calibre. 3. Un shock insulinique entraine des modifications du même ordre: a) déplétion des granules denses, limitée dans ce cas à la portion la plus antérieure des deux couches externes de l'E.M.R.; b) enrichissement relatif des granulations de moyen (1200–1400 Å) et de gros (1600–1900 Å) calibre dans l'E.M.C. avec, en plus dans l'E.M.C., un enrichissement en vésicules de type synaptique. 4. Un traitement à la métopirone produit un accroissement du nombre des granulations de moyen (1200–1400 Å) calibre dans les couches externes de l'E.M.R. et de l'E.M.C., et un enrichissement important de l'E.M.C. en vésicules de type synaptique. 5. Le traitement à la prednisolone conduit à un enrichissement très marqué des couches externes de l'E.M.R. en grains de 1200–1400 Å, et à un enrichissement des couches externes de l'E.M.C. en granulations de 1000 Å. Ces résultats sont discutés dans la perspective des régulations hypothalamo-corticotropes, particulièrement en ce qui concerne les granules de 1200–1400 Å.
    Notes: Summary The effects of adenohypophysectomy, and of several experimental interventions on the hypothalamo-pituitary-adrenal cortical axis have been studied in relation to the fine structure of the median eminence in the pigeon. 1. In control animals, the following morphological features of the caudal median eminence (C.M.E.) distinguish it from the rostral median eminence (R.M.E.): a) the absence in both external layers of the C.M.E. of large (1,600–1,900 Å) electron-dense granules, b) the presence in the C.M.E. of a small number of medium-size (1,200–1,400 Å) granules, and c) the predominance in the C.M.E. of small (600–800 Å) dense-core vesicles. 2. Adenohypophysectomy leads to: a) almost complete disappearance of electron-dense granules in both external layers of the R.M.E., and b) “emptying” of numerous axons and a relative increase in the number of large (1,600–1,900 Å) granules in the C.M.E. 3. Insulin shock produces modifications similar to those of adenohypophysectomy. The depletion of electron-dense granules from the axons is, however, restricted to the most anterior part of the R.M.E., and, in the C.M.E., the relative increase in the number of larger granules affects the 1,200–1,400 Å and the 1,600–1,900 Å size granules. 4. Metopirone enhances the number of medium-size (1,200–1,400 Å) granules in the external layers of both the R.M.E. and the C.M.E. and causes a significant increase in the number of synaptic-like vesicles in the C.M.E. 5. Prednisolone treatment leads to a marked enrichment of the external layers of the R.M.E. with 1,200–1,400 Å granules, and of the external layers of the C.M.E. with 1,000 Å granules. These results have been discussed with special reference to the hypothalamic control of the adrenocorticotropic function, especially reviewing the role of the 1,200–1,400 Å granules.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 106 (1970), S. 451-472 
    ISSN: 1432-0878
    Keywords: Hemocytopoiesis ; Insects ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Mikroskopische Beobachtungen an normalen „phagozytären Geweben“ (im Sinne der älteren Autoren) entlang des dorsalen Diaphragmas der beiden Orthopteren-Arten Gryllus bimaculatus und Locusta migratoria zeigen übereinstimmend, daß diese Bildungen eine hematopoietische Struktur haben. Bei beiden Arten entwickeln sich die blutbildenden Stammzellen aus einer großen Anzahl sog. Retikularzellen mesodermalen Ursprungs, die den Retikularzellen der blutbildenden Gewebe der Vertebrata sehr stark ähneln. Wie bei den Vertebrata differenzieren sich bei den Insekten die Blutzellen in sog. isogenen Zellgruppen von gleichem Typus und gleichem Entwicklungsstadium. Die starke phagozytäre Neigung der Retikularzellen erklärt, warum die blutbildenden Gewebe der Orthoptera von den älteren Autoren als phagozytäre Organe angesprochen wurden. Die hämatopoietische Differenzierung der Retikularzellen in reife Blutzellen (Haemozyten) findet entweder in einem lockeren Gewebe entlang des dorsalen Blutgefäßes, wie bei Locusta, statt, oder im inneren mehrerer, an das Herz gebundener, hoch organisierter blutbildender Organe, wie bei Gryllus, die noch stärker an die klassischen Strukturen der Vertebrata erinnern. Wir beschreiben im einzelnen beide Strukturtypen, insbesondere bei Gryllus die Einteilung der Organe in einen Cortex, in dem sich die Blutzellen bilden, und eine Medulla, in welcher sich die reifen Haemozyten ansammeln können. Nach starken Blutverlusten zeigen besonders die blutbildenden Gewebe von Gryllus eine dramatische Stimulierung der Hämatopoiese an; die Punktion der hämatopoietischen Organe kann also ebenfalls experimentell nachgewiesen werden.
    Notes: Summary Microscopic observations of the normal “phagocytic tissues” (in the sense of the classic authors) of the dorsal diaphragm in the two Orthopterans Gryllus bimaculatus and Locusta migratoria unequivocally demonstrate the hematopoietic nature of these cellular accumulations. In the two species, the hematopoietic elements develop from a large number of so-called reticular cells of mesodermic origin, which resemble closely the reticular cells of the hematopoietic organs of Vertebrates. As it is the case in Vertebrates, the differentiation of the hematopoietic elements into mature blood cells occurs in the two Orthopterans also in isogenic cell islets. The phagocytic activity of the reticular cells explains the fact that these organs were classically considered in the Orthopterans as simple phagocytic organs. The hematopoietic differentiation of the reticular cells can occur either in a poorly organized, loose tissue located along the dorsal vessel, as is the case in Locusta, or in a group of highly organized hematopoietic organs, as in Gryllus, which resemble far more the classical hematopoietic structures of Vertebrates. We give a detailed description of both types of organization, especially of the subdivision in Gryllus, of the hematopoietic organs into a cortex, where the haemocytes differentiate, and a medulla, where they can accumulate. After severe hemorrhages, the hematopoietic organs of Gryllus show all the features of a dramatic stimulation of hematopoiesis; their function can thus be experimentally demonstrated.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 106 (1970), S. 523-538 
    ISSN: 1432-0878
    Keywords: Ependyma ; Intracytoplasmic lipid bodies ; Histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Bei erwachsenen Feuersalamandern und bei Salamanderlarven konnten in Ependymzellen sowie in subependymären Zellelementen des Gehirns und Rückenmarks zahlreiche rundliche intrazytoplasmatische Körper von starker Osmiophilie beobachtet werden, deren Durchmesser bis zu 12 μ betrug. Vereinzelt fanden sich diese voluminösen Gebilde auch im Cytoplasma von Satellitenzellen der Hirnnerven- und Spinalganglien. Das histochemische Verhalten und das Ultrastrukturbild der intrazytoplasmatischen Körper sprechen dafür, daß sie hauptsächlich aus Lipiden bestehen. Ihre funktionelle Bedeutung konnte bisher nicht eindeutig geklärt werden.
    Notes: Summary The ependymal and subependymal cells of the ventricular system and the central canal in adult und larval salamanders contain numerous unusually large intracytoplasmic osmiophilic spherical bodies with a diameter of up to 12 μ. Sporadically the bodies are found within satellite cells of peripheral ganglia. Histochemical and ultrastructural examination suggests that the bodies consist mainly of lipids. Their functional significance is unknown.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 109 (1970), S. 384-397 
    ISSN: 1432-0878
    Keywords: Heart muscle cells ; Electron microscopy ; Quantitative ; Asphyxia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Normale und hypoxische Herzmuskelzellen aus der Wand des linken Ventrikels der Ratte wurden quantitativ-morphologisch anhand von elektronenmikroskopischen Längsschnitten nach Perfusionsfixierung untersucht. In normalen Zellen waren alle Myofibrillen relaxiert, die mittlere Sarcomerlänge betrug 2,2 μm. Die Schnittfläche wurde zu 55% von Myofibrillen, zu 27% von Mitochondrien und zu 18% von Grundplasma und Reticulum eingenommen. Die zwischen den Myofibrillen liegenden Mitochondrien waren längsoval und im Mittel 2,3mal so lang wie breit. Es bestand kein Unterschied zwischen subendokardial und subepikardial gelegenen Zellen. 10 min nach Erstickung der Tiere waren in den sonst unauffälligen Muskelzellen die Glycogengranula vermindert. Nach 20 min führte die Hypoxie zu einer Zunahme der relativen Schnittfläche der Mitochondrien um etwa 16% und zu einer beginnenden Kontraktur der Myofibrillen (Sarcomerlänge 2,0 μm). 20 min Hypoxie in Hypothermie (25–30°C intrathorakal) veränderte die normale Zellstruktur dagegen kaum. Wenn die Herzen während der 20 min dauernden Hypoxie in Normothermie mit einer procainhaltigen sauerstoff- und glucosefreien Blutersatzlösung durchspült wurden, waren die Myofibrillen relaxiert, die Schwellung der Mitochondrien dagegen wurde nicht reduziert. 30 min nach Erstickung wurde die Kontraktur stärker (Sarcomerlänge 1,7 μm). Nach 60 min bildeten sich Superkontraktionsknoten, einzelne Myofibrillen waren in Höhe der I-Bänder unterbrochen. Die Cristae der Mitochondrien wichen auseinander, die Schnittfläche der Mitochondrien hatte um 27% zugenommen. Während in Normotherapie eine Asphyxie des Tieres bereits nach 10 min die Herzmuskelzellen funktionell schwer schädigt, ist die Schädigung morphologisch erst nach 20 min eindeutig. Das bedeutet, daß für die elektronenmikroskopische Präparation eine Hypoxie von unter 10 min bedeutungslos ist. Hinsichtlich der morphologischen Manifestationszeit für die Unterbrechung der Sauerstoffversorgung stimmen unsere Befunde an Herzmuskelzellen gut mit vergleichbaren Angaben an Leberzellen überein.
    Notes: Summary In heart muscle cells of the left ventricle of rats the distribution of cell organelles and their reaction to hypoxia were investigated by electron microscopy. In normal hearts fixed by perfusion with aldehydes, the mean sarcomere length was 2.2 μm. 27% of the longitudinal sectional area was occupied by mitochondria, 55% by myofibrils and 18% by sarcoplasmic reticulum and ground plasm. The mitochondria situated in rows between the fibrils were oval and measured 2.3 times more in length than in width. There was no difference between cells from subendocardial and subepicardial regions. 10 min hypoxia (complete occlusion of the trachea) did not affect the appearance of muscle cells but diminished the number of glycogen granules. After 20 minutes the area occupied by mitochondria was increased by 16%, the mitochondria between the myofibrils were more spherical and only 1.5 times longer than wide. The sarcomeres shortened to 2.0 μm. With hypothermia (25–30°C) hypoxia of 20 minutes duration did not affect the cell structure. Perfusion of the heart by a saline solution, which contained procaine but neither oxygen nor glucose, for 20 minutes prevented shortening of the sarcomeres but not swelling of the mitochondria. 30 minutes after occlusion of the trachea the myofibrils shortened to a sarcomere length of 1.7 μm. After 60 minutes irregularly and excessively contracted myofibrils appeared and some sarcomeres were interrupted at the level of the I-bands. In some of the swollen mitochondria the cristae were widely separated. The increase of the area occupied by mitochondria was 27%. Asphyxia affects heart muscle cells severely with respect to function within 10 min, but morphologically it takes 20 min before a definite effect can be noticed. As to the time after which lack of oxygen is manifested morphologically, our results are consistent with findings in liver cells.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 109 (1970), S. 431-449 
    ISSN: 1432-0878
    Keywords: Contractile ring ; Cytokinesis ; Cell division ; Cytochalasin B ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Techniques of individual cell selection and precise ultramicrotomy have been employed to demonstrate that the contractile ring of cleaving HeLa cells is a transitory cytoplasmic organelle of distinctive fine structure and location. The contractile ring is an uninterrupted annulus encircling the equator of dividing cells exactly where the cleavage furrow forms. It is about 10 microns wide, up to 0.2 microns in thickness, and is composed exclusively of circumferentially aligned thin filaments 40–70 Å in diameter. Contractile ring filaments appear to be associated with the overlying plasma membrane. Controlled experiments with a mold metabolite (cytochalasin B) reveals that within a few minutes the drug abolishes the ability of HeLa cells to undergo cytokinesis. Cytochalasin B seems to decompose the contractile ring. It has no other clearly identifiable effects on other cell structures, notably the mitotic apparatus. Cytochalasin B is the only drug known which selectively inhibits cytokinesis in animal cells. In conclusion, the contractile ring is the most likely organelle responsible for cytokinesis in HeLa cells. Similar organelles probably occur in all cleaving animal cells. Successful cleavage depends upon the structural and functional integrity of the contractile ring.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 110 (1970), S. 153-165 
    ISSN: 1432-0878
    Keywords: Reptiles ; Skin ; Keratin ; Electron microscopy ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The different patterns of keratin formation that have evolved in the class Reptilia are all variations of a common process. In Squamata (snakes and lizards), a sequence of layers composed of α or β keratin is formed periodically, after which the old epidermal generation is shed. In Chelonia (turtles and tortoises), the epidermis of the shell is composed of only β keratin, whereas the skin of the neck and leg is composed exclusively of α keratin. Molting in toto does not occur and shedding is a continuous process comparable to that in avian and mammalian epidermis. In Crocodilia (crocodiles, caimans, alligators) there is only a single layer of cornified cells, but the composition of the layer varies in different parts of the scale. The hinge regions have many of the morphological characteristics of α and β keratin whereas the center resembles β keratin. The living cells beneath contain accumulations of keratohyalin. There are four ultrastructural characteristics of a keratinized α layer: 1) cellular outlines remain distinct, 2) a thickened plasma membrane forms during keratinization, 3) 80 Å filaments embedded in an amorphous matrix can be seen, and 4) PAS-positive material accumulates in extracellular spaces between the desmosomes. The β layer exhibits none of these features. Instead the cells more or less (depending on species) coalesce into a compact layer which becomes attenuated in the hinge regions. A 30 Å filament pattern can be seen. The mesos layer of squamates resembles the hinge region of crocodilians, exhibiting a combination of the characteristics of both α and β keratin.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 106 (1970), S. 309-321 
    ISSN: 1432-0878
    Keywords: Red nucleus ; Substantia nigra ; Neuroglia ; Pericytes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of perivascular and perineuronal cells in the substantia nigra and red nucleus was studied in Nissl, silver carbonate, and electron microscopic preparations. In light microscopic preparations of the red nucleus and substantia nigra oligodendrocytes and astrocytes are located adjacent to blood vessels and nerve cells. Pericytes are also found adjacent to blood vessels. Scattered perineuronal oligodendrocytes and astrocytes are present in the magnocellular portion of the red nucleus and in the substantia nigra, whereas a distinguishing morphological feature of the parvocellular portion of the red nucleus is the clustering of perineuronal oligodendrocytes around a single neuron. In the present electron micrographs of the red nucleus and substantia nigra oligodendrocytes are separated from the vascular basement membrane (basal lamina) by astrocyte processes and therefore are not truly perivascular. Pericytes are easily identified by the basement membrane which encompasses their cell bodies and processes. Characteristic of the neuropil in the red nucleus are astrocytic processes that approximate dendrites. In contrast, astrocytic processes in the substantia nigra rarely contact dendrites which are covered by a mosaic of synaptic endings. A “third type of neuroglial element” is also present in the neuropil of the substantia nigra and the red nucleus.
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  • 14
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    Cell & tissue research 108 (1970), S. 324-338 
    ISSN: 1432-0878
    Keywords: Human myocardium ; Innervation ; Nerve endings ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscope studies of axons, distributing singly or in small bundles in the human ventricular and atrial myocardium, indicate a few per-cent of the axon profiles to be significantly large in diameter (1.5–3.0 μ). They are characteristically packed with a profuse number of mitochondria along with large granular vesicles, glycogen rosettes, lysosomic bodies; and some of them terminate on a “specific terminal cell” (Knoche and Schmitt). These mitochondria-rich, large axons are assumed to be terminal portions of the cardiac afferents. About half of the axons encountered in the ventricle and 2/3 in the atrium are non-vesiculated, usually less than 0.5 μ. in diameter. The varicosities containing numerous vesicles are mostly 0.5–1.5 μ in diameter and are assumed to be terminal portions of the cardiac efferents. The ratio between the number of axon profiles containing small granular vesicles and that of axon profiles containing agranular vesicles without small granular vesicles is 2∶1 in the ventricular myocardium and 1∶1.7 in the atrial myocardium.
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  • 15
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    Cell & tissue research 109 (1970), S. 33-45 
    ISSN: 1432-0878
    Keywords: Testis ; Interstitial cells ; Reptiles ; Hormone Production ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé L'ultrastructure des cellules interstitielles du testicule de Lacerta vivipara a été étudiée entre le printemps et l'automne pendant deux années. Le retioulum endoplasmique lisse, et les mitochondries à crêtes tabulaires sont les organites les plus remarquables comme dans les autres cellules productrices de stéroïdes, mais les liposomes et l'appareil de Golgi sont bien représentés aussi. Les variations ultrastructurales les plus significatives apparaissent entre le printemps et le début de l'été. Au printemps, alors que les caractères sexuels secondaires sont hypertrophiés, un système remarquable de vésicules et de vacuoles se développe à partir du reticulum et probablement aussi du Golgi. Au début de l'été, lorsque les caractères sexuels secondaires sont atrophiés, les vacuoles sont moins nombreuses et le reticulum forme un réseau dense de tubules typiques, souvent étroitement associés aux liposomes; les crêtes mitochondriales sont gonflées. Ces images sont discutées en fonction de l'activité saisonnière d'élaboration d'hormones. L'hypertrophie des systèmes membranaires au printemps correspond probablement à la production ou (et) à l'excrétion des hormones androgènes. Au début de l'été, la cellule n'élabore pas d'androgènes, mais n'est peut-être pas complètement inactive: elle pourrait stocker des précurseurs hormonaux.
    Notes: Summary Interstitial cells of the testis of Lacerta vivipara have been studied electronmicroscopically in animals obtained between spring and autumn. Smooth endoplasmic reticulum and mitochondria with tubular cristae are the most prominent organels, lipid droplets and Golgi apparatus being also well developed. The most significant ultrastructural changes occur between spring and the beginning of summer. In spring, during the hypertrophy of secondary sexual characters, a conspicuous system of vesicles and vacuoles originates from the smooth endoplasmic reticulum and probably also from the Golgi apparatus. At the beginning of summer, when secondary sexual characters are atrophied, vacuoles are less prominent and the smooth endoplasmic reticulum consists of a dense network of typical tubules, often closely associated with the lipid droplets; the cristae of the mitochondria are swollen. These ultrastructural findings are discussed in relation to the production of hormones. The hypertrophy of membrane systems in spring corresponds presumably to production or (and) release of androgen hormones. In the beginning of summer the cell does not produce androgens, but probably is not completely inactive: it may store precursors of hormones.
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  • 16
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Gastropoda ; Fluorescence ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Durch Vergleich fluoreszenz- und elektronenmikroskopischer Untersuchungen am zentralen Nervensystem von Planorbarius corneus L. wird nachgewiesen, daß in den Schlundringganglien Neurosekretzellen vorkommen (Nachweis mit Pseudoisocyaninchlorid), die mit Nervenzellen nicht identisch sind, die durch ihren hohen Gehalt an biogenen Aminen auffallen (Nachweis durch die Methode von Falck und Owman, 1965). Es können daher im Schlundring von Planorbarius corneus peptiderge und aminerge Neurosekretzellen unterschieden werden. Die PSC-positiven Neurosekretzellen enthalten elektronendichte Elementargrana und die aminergen Neurone „dense-core“ Vesikel. Der Nachweis biogener Amine in einigen Nervenzellen von Planorbarius corneus spicht für deren chemische Identität mit Transmittersubstanzen, ihre hohe Konzentration aber für eine Abgabe in die Körperflüssigkeit.
    Notes: Summary The neurosecretory system of the snail Planorbarius corneus has been investigated by fluorescence and electron microscopy. With the fluorochrome Pseudoisocyanin the established neurosecretory system in the cerebral ganglia and single neurosecretory cells in the other ganglia show an intensive yellow fluorescence. Electron micrographs reveal the presence of electron dense granules (elementary granules) in the pericarya and the axons of neurones which have the same localisation in the ganglia as the pseudoisocyanin-positive cells. The fluorescence technique for biogenic amines produces yellow and green fluorescence within neurons and in the neuropil and nerves. The fluorescence obtained in determinable areas and neurones correlates well with the electron microscopic location of “dense-core” vesicles within the pericarya and axons of cells in even the same areas. It is discussed, that in this animal both types of cells are so-called “neurosecretory cells”, because the high content of elementary granules in the “peptidergic neurosecretory cells” and of “dense-core” vesicles in the “aminergic neurosecretory cells” is an indication for secretion of these products in neurohaemal areas (circulatory channels).
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  • 17
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    Cell & tissue research 110 (1970), S. 321-335 
    ISSN: 1432-0878
    Keywords: Thymus ; Lymphocyte ; Analysis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Thymic small lymphocytes of dd-mice were qualitatively and quantitatively studied by electron microscopy. Differences in fine structure were revealed between cortical and medullary small lymphocytes. Cortical small lymphocytes are rounded in cell outline with a round nucleus. The cytoplasm surrounding the nucleus as a narrow rim is scanty and appears relatively dense due to an abundance of free ribosomes. The cell organelles are not well developed. On the other hand, medullary small lymphocytes are more irregular in shape with uneven cell membranes. Their nuclei are also more irregular in outline with frequent infoldings of the nuclear membrane. The cytoplasm is more abundant and paler with less numerous ribosomes. The cell organelles are better developed. Quantitative analysis was made of both cortical and medullary small lymphocytes by means of the point counting method. The nuclei of both cortical and medullary small lymphocytes are almost the same in size (a diameter of 4.9 μ). The cell sizes are different between cortical and medullary lymphocytes: cortical small lymphocytes with a diameter of 5.5 μ were smaller than medullary ones with a diameter of 6.4 μ. Cortical small lymphocytes are very sensitive to the destructive effects of hydrocortisone, whereas the medullary ones are resistant. Periarteriolar lymphoid sheath in the splenic white pulp, which is known to be a thymus-dependent area, contains small lymphocytes that were similar in cytological details to medullary small lymphocytes of the thymus. In the light of the recent knowledge about a recirculating long-lived small lymphocyte pool, it appears probable that medullary small lymphocytes represent a contribution to the pool and that small lymphocytes with a long life span can be cytologically identified by electron microscopy.
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  • 18
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    Cell & tissue research 110 (1970), S. 386-400 
    ISSN: 1432-0878
    Keywords: Autonomic nerves ; Perineurial sheath ; Termination ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Das Perineurium kleiner Mesenterial- und Trachealnerven besteht aus einer Lage platter, beiderseits von einer Basalmembran umschlossener Zellen. Im Bereich von Abzweigungen kleiner Nerven bildet das Perineurium ein gekammertes, stark kollagenfibrillenhaltiges Hüllensystem. Die Endigung der einschichtigen Perineuralhülle hat die Form einer in das Interstitium geöffneten Röhre. Im ansatznahen Drittel des Mesenteriums und in der Schleimhaut der Trachea wurden ausschließlich perineuriumfreie Nerven gefunden. Es liegt nahe, diese perineuriumfreien Bezirke zu funktionellen Endräumen zusammenzufassen. In perineuriumfreien Bezirken wird das gehäufte Auftreten von Nervenauftreibungen mit Vesikeln, die Transmittersubstanz enthalten, und Mitochondrion beobachtet. Die erhobenen Befunde werden mit den an dickem Perineurium gewonnenen Ergebnissen verglichen und diskutiert.
    Notes: Summary The perineurial sheath of small tracheal and mesenteric nerves consists of a layer of flat, basement membrane coated cells. Its ramifications form a complicated layered system, interspersed with collagen fibrils. The tube formed by the thin perineurial sheath ends openly, which affords communication between the respective interstitial spaces. The mesenteric nerves close to the duodenum as well as the nerves in the vicinity of the tracheal epithelium show no perineurial sheath. Peripheral nerves lacking a perineurial layer seem to be close to their terminations. Their fibers show varicosities containing transmitter vesicles and mitochondria with longitudinally orientated cristae. Our results are compared with those found in thick, multilayered perineurial sheaths and functional differences are discussed.
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  • 19
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    Cell & tissue research 111 (1970), S. 51-63 
    ISSN: 1432-0878
    Keywords: Purkinje cell ; Golgi apparatus ; Dendrites ; Differentiation ; Histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of postnatal differentiation of the Golgi apparatus, the nucleus, the perikaryon, and the dendrites was studied in Purkinje cells of the rat cerebellum for 30 days after birth using histochemical, histological, and electron microscopic methods. The Golgi apparatus during differentiation undergoes morphological and positional changes. From the 1st to 7th postnatal day, the Golgi apparatus is found in a supranuclear position, and is connected with the axes of differentiating primary dendrites by beam-like processes. From days 8 to 11 this connection disappears, and most of the Golgi apparatus assumes a lateronuclear and infranuclear position. After the 11th or 12th day, the Golgi apparatus is found in perinuclear and peripheral cytoplasmic positions. The formation of granular endoplasmic reticulum occurs in the vicinity of the perinuclear Golgi apparatus. The differentiation of cell and nuclear forms requires approximately 20 days. The morphological changes of differentiation are discussed in relation to the participation of the Golgi apparatus in the differentiation of dendrites and in the formation of the granular endoplasmic reticulum.
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  • 20
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    Cell & tissue research 111 (1970), S. 149-159 
    ISSN: 1432-0878
    Keywords: Rabbit ovum ; Fertilization ; Pronucleus ; Cleavage ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fertilized ova were flushed from the Fallopian tubes of New Zealand White rabbits at 15 to 30 hours after mating and examined with the electron microscope. Between 21 and 22 hours intact pronuclei with extensive interdigitation of apposing surfaces were found in most ova. In some, an appearance suggesting internuclear communication was observed. In other ova disrupted pronuclear membranes surrounded centrally placed chromosome aggregates. In still others an advanced cleavage furrow was already present. By 23 hours all ova were in the two-cell stage.
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  • 21
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    Cell & tissue research 103 (1970), S. 382-397 
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Newborn rat ; Stereology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure of the zona glomerulosa and the zona fasciculata of the newborn rat adrenal cortex has been studied by the light and the electron microscope. The ultrastructural features of the cells of both zones are described. By morphometric methods the relative volumes occupied by mitochondria and by lipid droplets have been evaluated. The “membrane profile concentration” (i.e. the average number of microns of smooth reticulum profiles per square micron of cytoplasm) has been also measured. The most significant ultrastructural differences between the cells of the two zones concern the mitochondria, the lipid droplets, and the smooth endoplasmic reticulum. The mitochondria show typical lamellar cristae in the elements of the zona glomerulosa, and vesicular cristae in the cells of the zona fasciculata. They occupy the same relative volume in both elements. The lipid droplets and the smooth reticulum show no qualitative differences in the two cell types, but they are found in a larger amount in the cells of the zona fasciculata. These ultrastructural findings are discussed in relation to the numerous biochemical data, suggesting that the cells of the zona glomerulosa are resting elements at birth, while the cells of the zona fasciculata are active steroid-secreting elements already in late gestation.
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  • 22
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    Cell & tissue research 103 (1970), S. 398-409 
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Newborn rat ; Electron microscopy ; Lysosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structural changes of the zona juxtamedullaris of the rat adrenal cortex at birth, have been examined by the light and the electron microscope. In this zone clusters of medullary cells lying among the strands of cortical tissue were observed. In the inner portion of the zona juxtamedullaris two types of adrenocortical cells were found: light and very-dark cells. The latter are smaller than the light cells and are always in close connection with the medullary tissue. The ultrastructural features of the very-dark cells suggest that these elements are in degeneration. This finding supports the hypothesis that at birth there is a partial degeneration of the rat zona juxtamedullaris, i.e. the zone corresponding to the “fetal zone” of some mammalian species. It is proposed that in all mammalian species at birth there is a partial regression of the zona juxtamedullaris and that the regression of the “fetal zone” is only the quantitative increase of this phenomenon. This hypothesis is discussed in relation to numerous data demonstrating that there are enzymatic conditions in the rat during fetal life, which permit a discrete hypertrophy of the adrenal cortex.
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  • 23
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    Cell & tissue research 103 (1970), S. 341-350 
    ISSN: 1432-0878
    Keywords: Catecholamines ; Brain ; Insects ; Electron microscopy ; Cytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the brain of the cockroach Periplaneta americana, the beta lobes of the corpora pedunculata respond with an intense positive reaction to a specific fluorescence histochemical method for catecholamines. The fluorescence reaction disappears completely after prolonged treatment of the cockroaches with reserpine. An ultrastructural examination of the beta lobes in formaldehyde-glutaraldehyde-osmium fixed preparations reveals the presence of two types of fibres: 1) Fibres and nerve endings containing small clear vesicles and sligthly larger vesicles with a semi-dense content. The appearance and size distribution of these vesicles ist not affected by treatment with reserpine. 2) Fibres containing larger and denser vesicles, but practically no clear vesicles. The size distribution of these dense vesicles is only slightly affected by treatment of the cockroaches with reserpine. If brain slices are incubated in a medium containing noradrenaline or α-methyl-noradrenaline and fixed in permanganate, small vesicles with electron-dense central cores show up, similar to those which have been described in vertebrate adrenergic nerve fibres (“small granular vesicles”). They are confined to one of the two types of fibres (a and b) visible in these preparations, namely to type b, whose correspondence with type 2 fibres of formaldehyde-glutaraldehyde-osmium fixed preparations is discussed.
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  • 24
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    Cell & tissue research 104 (1970), S. 345-357 
    ISSN: 1432-0878
    Keywords: Photoreceptor ; Lumbricus ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Die Feinstruktur der Photorezeptorzellen in der Epidermis, in kleineren Nervenästen und im Zerebralganglion von Lumbricus terrestris wurde untersucht. Das Vorhandensein eines zentralen, intrazellulären Lumens (Phaosom), das mit Mikrozotten gefüllt ist, erinnert in der Struktur der Photorezeptorzelle des Regenwurms an Lichtsinneszellen von Hirudo. Außer Mikrozotten findet man im Phaosom einige Zilien vom Typ 9×2+0; solche Zilien sind von den Mikrozotten strukturell unabhängig. Durch eine Aufzweigung des Phaosoms in kleinere Buchten, die tief in das umgebende Zytoplasma eindringen, erhält es ein labyrinthartiges Aussehen. Glatte Zisternen in Gruppen von 2 bis 5 wurden oft um das Phaosom im Zytoplasma beobachtet. Charakteristische Bestandteile der Zelle sind noch Vesikel und Vakuolen, die mit einer Substanz von wechselnder Elektronendichte gefüllt sind. Die Photorezeptorzellen werden von Gliazellen und Gliafortsätzen umgeben, die an vielen Stellen die Zelloberfläche tief einstülpen (Trophospongium).
    Notes: Summary Photoreceptor cells in the epidermis and nerve branches of the prostomium and in the cerebral ganglion of Lumbricus terrestris were investigated with the electron microscope. The photoreceptor cell is similar to the visual cell of Hirudo by having a central intracellular cavity (phaosome) filled with microvilli. Besides microvilli, several sensory cilia can also be found in the phaosome but they are structurally independent of the microvilli. A gradual branching of the phaosome cavity into smaller cavities makes its sectional profile extremely labyrinthic. Flattened smooth-surfaced cisternae in stacks of 2 to 5 are frequently observed around the phaosome. Characteristic constituents of the cytoplasm are vesicles and vacuoles filled with a substance of varying density. The photoreceptor cell is covered by glial cells or by their processes which at many places deeply invaginate the cell surface (trophospongium).
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  • 25
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    Cell & tissue research 105 (1970), S. 176-187 
    ISSN: 1432-0878
    Keywords: Ependyma ; Salamandra maculosa ; Neuronal elements ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Zwischen den eigentlichen Ependymzellen des Zentralkanals adulter Feuersalamander kommen amphorenartig gestaltete Elemente vor, die sich aufgrund ihrer synaptischen Kontakte mit Axonendigungen als Neurone identifizieren lassen. Diese intraependymalen Nervenzellen weisen einen apikalen Fortsatz auf, der sich mit einer warzen- oder knotenförmigen Protrusion in das Lumen des Zentralkanals erstreckt. Die Protrusion ist gewöhnlich mit stereozilienartigen Ausläufern besetzt. Die funktionelle Bedeutung der beschriebenen neuronalen Elemente konnte bisher nicht geklärt werden.
    Notes: Summary The ependyma of the canalis centralis of adult salamanders was examined by electron microscopy. Between the ependymal cells occur amphora-like elements identifiable as neurons by their synaptic contacts with axon terminals. These intraependymal nerve cells exhibit an apical outgrowth extending into the lumen of the canalis centralis with a wart-like or knob-like protrusion. The latter usually bears extensions resembling stereocilia. The functional significance of the neuronal elements is still unknown.
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  • 26
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    Cell & tissue research 105 (1970), S. 515-525 
    ISSN: 1432-0878
    Keywords: Cuticle ; Rotifer ; Development ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural studies of developing Asplanchna brightwelli embryos support the following hypothetical scheme of cuticle formation. First the external hypodermal membrane invaginates, and deposition of a dense intracellular layer commences next to this membrane. Then the rough endoplasmic reticulum synthesizes fibrous protein which is transferred to the Golgi complex. Here polysaccharide is synthesized and added to the protein, and the resulting filamentous complex is enclosed in large irregularly shaped vesicles which bud off from the Golgi elements. Maturation of the filamentous material to condensed cuticle material occurs as the vesicles move to the invaginations. Each vesicle fuses with an invagination, thus forming a hypodermal bulb; then the cuticle material is discharged through the neck of the bulb to its extracellular location. After the bulbs are formed, new, smaller, spherical vesicles begin to bud off from the Golgi elements. They too contain the filamentous complex which is refined to condensed cuticle material as the vesicles near the bulb. These vesicles fuse with the hypodermal bulbs contributing the cuticle and membrane necessary for the growth of the hypodermis of the embryo and newborn animal. Ruthenium red staining has confirmed that the cuticle consists of glycoprotein.
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  • 27
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    Documenta ophthalmologica 28 (1970), S. 191-200 
    ISSN: 1573-2622
    Keywords: Acomys Cahirinus ; Retinal capillary basement membrane width ; Age modifications ; Electron microscopy ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé L étude morphométrique des capillaires rétiniens de souris à piquants de différents âges (3, 6, 12 et 36 mois) a démontré un épaississement des membranes basales et un élargissement des diamètres capillaires en fonction de l'âge et, en outre, l'existence d'une corrélation positive entre ces deux paramètres.
    Abstract: zusammenfassung Die morphometrische Untersuchung von Retinakapillaren verschieden Alter (3, 6, 12 und 36 Monate) Stachelmäuse (Acomys cahirinus) ergab eine altersabhängige Zunahme sowohl der Basalmembrandicke als auch des Kapillardurchmessers. Zudem wurde eine positive Korrelation zwischen diesen beiden Parametern gefunden.
    Notes: Abstract Specimens of four age groups of non-diabetic, non-obese spiny mice (Acomys Cahirinus), 3, 6, 12, 36 months old respectively, were examined for changes in retinal capillaries. Morphometrical evaluation of electron-micrographs allowed to conclude that capillary basement membrane width, as well as capillary diameter, increase during ageing: the values in the four different age groups were found to be 656, 925, 1098, 1772 Ångström units for the average basement membrane width, and 3,72, 4,08, 4,58, 5,60 microns for average capillary diameter. The differences between the age groups proved to be significant at a p 〈 0,01. Furthermore, a positive correlation between capillary diameter and capillary basement membrane width seems to be highly probable.
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  • 28
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 4 (1970), S. 97-107 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 29
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    International Journal of Quantum Chemistry 4 (1970), S. 431-450 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A one-centre CI wave function for HeH+ reported by Stuart and Matsen for 0.1 ≤ R ≤ 5.0 has been analysed in detail from the viewpoint of molecular formation. Further, by means of a natural orbital analysis, it was possible to obtain some measure of the electron correlation contained within such wave functions for various R values. These effects were illustrated by means of a series of difference maps for the electron density. One- and two-particle expectation values were obtained as a function of R. Thus, it was possible to study several aspects of the influence of the proton on the electron charge cloud as we pass from He through to the united atom Li+. The occupation numbers within the natural expansions were compared with those which arise from a similar analysis of a two-centre wave function for HeH+. The “character” of such wave functions for HeH+, and also for He and Li+, were analysed and compared.
    Additional Material: 5 Ill.
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  • 30
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    International Journal of Quantum Chemistry 4 (1970), S. 465-486 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quadrupolar and octupolar distortion of the ions in the He-sequence caused by an external electro-magnetic field has been studied by a variation-perturbation method in the Hartree-Fock scheme. For certain frequencies singularities appear in the response of the system to the perturbation. Approximate representations for the excited d and f states have been obtained from a study of these resonances. Such a perturbation calculation has the advantage that representations of the different excited states are obtained independently. The orthogonality to all the lower lying levels of the same symmetry is not required. The only source of inaccuracy implicit in the procedure lies in the improper consideration of the inter-electronic interaction. This is corrected for by an independent calculation, which is again formulated in terms of a perturbation treatment. The resulting wave functions for the excited states are accurate in the Hartree-Fock model. Expectation values of several operators have been calculated with these corrected wave functions.
    Additional Material: 1 Ill.
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  • 31
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    International Journal of Quantum Chemistry 4 (1970), S. 365-387 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The utility of the separated electron pair (SEP) model (strongly orthogonal geminals) is examined quantitatively, for pyramidal and planar nuclear configurations of the NH3 molecule. The best SEP wave function computed for each species is capable of recovering about half of the correlation energy obtained by a fairly accurate configuration interaction (CI) calculation, (corresponding to roughly 25% of the total molecular correlation energy). It is illustrated that the model can be systematically extended with only a modest effort to yield more accurate results (about 40% of the total correlation energy). The fact that the corrections to the SEP model have a simple physical interpretation suggests that this model may be a useful starting point for “brute force” CI calculations on larger chemical systems.
    Additional Material: 23 Tab.
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  • 32
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    International Journal of Quantum Chemistry 4 (1970) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 33
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    International Journal of Quantum Chemistry 4 (1970), S. 451-452 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 34
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    International Journal of Quantum Chemistry 4 (1970), S. 503-518 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations using a small Gaussian basis set, including 3d orbitals on the sulphur atom, have been performed on the fluorosulphate radical and the related ions SO3F+ and SO3F-. A new SCF procedure is described and applied to the open shell cases discussed here. The results are compared with recent CNDO calculations and with the experimental transition energies of the radical.
    Additional Material: 4 Tab.
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  • 35
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    International Journal of Quantum Chemistry 4 (1970), S. 519-527 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polikanov's perturbation method for the solution of the radial Schrödinger equation is shown to be equivalent to the usual Rayleigh-Schrödinger method but with full normalization instead of intermediate noralization. The energy corrections are shown to be the same to all orders. The computational advantages of Polikanov's method are discussed. The method is illustrated by considering the two-electron ions in the Hartree-Fock approximation.
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  • 36
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    International Journal of Quantum Chemistry 4 (1970), S. 533-539 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mathematical model of a molecule is proposed. The electronic structure is described using a molecular orbital wave function constructed from a small number of spherical Gaussians with optimized parameters. The models exhibit the desirable properties of numerical stability, objectivity and transferability. Results are given for CH4, C2H6, cyclo-propane, H2O, CH2O and C2H4. They can be given a chemical interpretation in terms of chemical bonds, lone pairs and atomic cusps.
    Additional Material: 6 Tab.
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  • 37
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    International Journal of Quantum Chemistry 4 (1970), S. 1-3 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A perturbation variation treatment of two-electron atoms using exp (-αr〈 - βr〉) as the zeroth order wave function is presented. The parameters α and β are variationally determined and the results are compared with the “physical” choice α = Z, β = Z - 1, and with Z-1 theory. The energy is given through fifth order in the perturbation.
    Additional Material: 1 Tab.
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  • 38
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    International Journal of Quantum Chemistry 4 (1970), S. 529-532 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The systems C2H4F+ and C2H4CH3+ have been investigated by the SCF-MO-P (LCGO) method. It will be shown that the results agree with the empirical rule of Markownikoff. An explanation of the rule of Markownikoff is given by means of the computed results.
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  • 39
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    International Journal of Quantum Chemistry 4 (1970) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 40
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    International Journal of Quantum Chemistry 4 (1970), S. 579-586 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed study of the performance of the Morse, the Hulburt--Hirschfelder and the Lippincott potential energy functions has been carried out by comparing them with the Rydberg-Klein-Rees potential energy curves for a number of electronic states of various diatomic molecules. Further, by employing the above potential energy functions, the radial Schrödinger equation has been solved for the vibrational energy levels, G(v), and the vibrational wave functions, ψv. The latter have been employed to determine the rotational constants, Bv, for the individual vibrational energy levels. Then the molecular constants, we, wexe, weye, Be, αe and γe for the various electronic states, have been computed by using the values of G(v) and Bv. A comparison of the molecular constants derived in this manner with the experimental ones reveals better agreement, in most cases, than that reported by previous workers.
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  • 41
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    International Journal of Quantum Chemistry 4 (1970) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 42
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of the MC-LCAO-MO approach, described in the preceding paper, is further applied to the benzene cation. Through the iteration process the π-electron energies and the molecular shapes are computed for the ground and two lowest excited states of the cation in both D6h and D2h geometries. A remarkable fact obtained is that a comparatively small variation of the geometrical structure (c. 0.010 - 0.013 Å bond length difference) brings about a considerable change of the energy value (c. 0.85 - 1.25 eV).The π-electronic excitation energies obtained from the iteration process are compared with the transition energies calculated from the usual method in which the structures of the excited states are assumed to be the same as the corresponding ground state structures. The difference in the excitation energy between the cation and the anion, and the CI effect on the excited states, are discussed. It is found that the doubly excited configurations play an important role in CI, which is somewhat different from that of the singly excited configurations. The stabilization energy due to the Jahn-Teller distortion is estimated for the ground state of the cation.
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  • 43
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    International Journal of Quantum Chemistry 4 (1970), S. 149-172 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is the aim of the present paper to give a mathematically oriented foundation of BW-perturbation theory, which is along the lines of Kato's previous work for RS-perturbation theory. For this purpose we firstly derive the expressions of BW-perturbation theory by the use of the contour integral method (Kap. I). In Kap. II sufficient criteria for the convergence of BW-perturbation theory are derived and applied to the 1/Z-expansion of the isoelectronic series of the He atom. The characteristic differences of the derivation and convergence properties of the two different kinds of perturbation theory are discussed in detail.
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  • 44
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    International Journal of Quantum Chemistry 4 (1970), S. 219-221 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 45
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for solving the Hartree-Fock problem in a finite basis set is derived, which permits each orbital to be expanded in a different basis. If the basis set for each orbital φi contains the basis functions for the preceding orbitals, φi-1, φi-2,… φ1, then the φi form an orthonormal set. One advantage over the standard Hartree-Fock method is that a different long range behavior for each orbital, as for example is required in the Hartree-Fock-Slater method, can be forced. A calculation on the ground state of beryllium is performed using the nested procedure. Very little energy is lost because of nesting, and the node in the 1s orbital disappears.
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  • 46
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    International Journal of Quantum Chemistry 4 (1970), S. 389-395 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A group-theoretical method is presented whereby the number and identity of the non-zero components of a property tensor in a (molecular or crystalline) environment of low symmetry may be determined.
    Additional Material: 4 Tab.
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  • 47
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    International Journal of Quantum Chemistry 4 (1970), S. 427-429 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analytical conditions are obtained and discussed under which the vibronic equations for dimers can be decoupled.
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  • 48
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An upper bound for E0, which has been derived from the conjugate eigenvalue problem by Hall, is discussed. It is emphasized that the bound is only guaranteed when V is negative-definite. An alternative bound is presented which is free from this restriction, and the underlying iterative procedure is given. Hall's result is generalized to admit internuclear distances, and the theory is illustrated by a one-dimensional system with delta-function potentials. Some disadvantages of the approach are mentioned.
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  • 49
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    International Journal of Quantum Chemistry 4 (1970), S. 625-630 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extended Gaussian orbital basis set calculations have been carried out on an assumed staggered and eclipsed classical geometrical configuration of C2H5+. The best total energies obtained for these geometries were -78.170692 a.u. and -78.170674 a.u. respectively, corresponding to a barrier to internal rotation of 1.8 × 10-5 a.u. or 11 kcal/mole. An analysis of the charge density matrix indicates that charge is distributed in these molecules in a manner consistent with the concept of hyperconjugation.
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  • 50
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    International Journal of Quantum Chemistry 4 (1970), S. 631-631 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 51
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    International Journal of Quantum Chemistry 4 (1970), S. 57-72 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polarization of closed shells in an alternant radical due to the field of its unpaired electron is discussed. It is shown that the Hartree-Fock solution is unstable relative to a small perturbation caused by polarization of closed shells in a long polyene radical. Its ground state is found to be antiferromagnetic with a forbidden zone in the spectra of one-particle excitations.
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  • 52
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    International Journal of Quantum Chemistry 4 (1970), S. 73-87 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic structure of the benzyl radical in its ground state has been computed using a model Hamiltonian due to Pariser-Parr with full configuration interaction as well as with different truncated configurational sets built on SCF open-shell orbitals. The correlation energy corresponding to this model was found to be equal to -0.929722 eV. With the singly excited configurations only 18% of this energy is taken into account. By extending the basis to include the doubly excited configurations one can account for 94% of the correlation energy. An analysis of the accuracy of the proton hyperfine splitting calculation caused by inaccurate computation of the wave function is given. If only singly and even doubly excited configurations are taken into account one cannot hope to obtain splittings with an accuracy of more than 0.5 g. Inclusion of triply excited configurations lowers this error by one order. In addition, the use of the simple McConnell relation may lead to an error in splitting calculations of no less than 1.5 g.
    Additional Material: 9 Tab.
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  • 53
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    International Journal of Quantum Chemistry 4 (1970), S. 89-95 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Self-consistent perturbation theory is introduced to facilitate making small, simultaneous variations in orbital exponents. This is accomplished by interpreting these variations as perturbations on the quantum mechanical system. The minimum-energy condition yields a set of linear equations for the desired exponential corrections.
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  • 54
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    International Journal of Quantum Chemistry 4 (1970), S. 121-121 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 55
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    International Journal of Quantum Chemistry 4 (1970), S. 173-189 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further energies for types of N2O4 valence structures (or valence formulae) are reported. The results indicate that two sets of formulae might give satisfactory distributions of the mobile σ-electrons. These are (i)Resonance between covalent and ionic formulae ((B) and (D) of Part II[8]);(ii)A non-paired spatial orbital formula ((F) of Part II [8]).One estimate of the σ-bond order for the NN bond is 0.4-0.5. For this, (i) is to be preferred, because it involves a much lower energy than (ii). But should the order be about 0.7, the energies of (i) and (ii) are similar, and both descriptions are satisfactory.The ionic formula of (i) involves non-localized bonding for the NO2+ moiety. It may be replaced by a formula with localized bonds, and an almost identical energy.
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  • 56
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    International Journal of Quantum Chemistry 4 (1970), S. 257-270 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of upper and lower bounds to the first few eigenvalues of a very large or infinite tridiagonal matrix H is studied. Those eigenvalues of a comparison-matrix Mn which are lower than a characteristic limit, together with the corresponding eigenvalues of the variational matrix Hn are shown to bracket exact eigenvalues of H. Mn differs from Hn only in the last off-diagonal element and is easily obtained from H. Sufficient conditions for lower bounds are based on a low estimate of the characteristic limit. For increasing dimensions n, the lower bounds approach the exact eigenvalues from below. As a numerical illustration, brackets to the known eigenvalues of the harmonic oscillator with a linear perturbation are calculated.
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  • 57
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    International Journal of Quantum Chemistry 4 (1970), S. 271-287 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the criterion for maximizing the projection of localized bond orbitals onto the space spanned by the occupied MO's, a method for constructing hybrid orbitals of a molecule is described. For illustration purposes the method is applied to single-determinant closed shell wave functions, calculated by means of ab initio and semiempirical procedures, for the molecules of methane, acetylene, ethylene, ethane, propylene, butadiene, ammonia and hydrogen cyanide. The predictions of hybridization are briefly discussed.
    Additional Material: 6 Tab.
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  • 58
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    International Journal of Quantum Chemistry 4 (1970), S. 347-353 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The charge on each atom of some ethers and chloro-substituted ethers, their dipole moments and the quadrupole coupling constants of the chloroethers have been calculated with the method suggested by Del Re. There appears to be an intimate connection between the charge density on the oxygen atoms and the capacity of forming hydrogen bond.
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  • 59
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    International Journal of Quantum Chemistry 4 (1970), S. 5-20 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper the minimum principle proposed for atomic systems by Hall, Hyslop and Rees [1] is generalized to molecules. It is shown that this generalization retains the advantage of admitting the use of a larger class of trial wave functions, for example those with discontinuities, than is possible in the usual minimum energy principle. The further advantage that the upper bounds obtained by this treatment are always at least as good as those of the Rayleigh-Ritz method is also preserved.The theory is applied to the H2+ ion, potential energy curves are obtained for various “cut-off” wave functions, and the equilibrium internuclear distance is calculated. The optimization of the “cut-off” region so that the upper bound is minimized is also discussed.
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  • 60
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    International Journal of Quantum Chemistry 4 (1970), S. 413-425 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fifth-rank molecular polarization tensors are discussed in terms of their tensor group which includes both the spatial symmetry and the permutation symmetry of the suffixes. This latter may be described by certain four-dimensional point groups, which in the nontotally symmetric cases may be projected into three-dimensional space. The study leads to a determination of the number of independent components of these tensors and a discussion of the types of phenomena which they may be expected to produce.
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  • 61
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    International Journal of Quantum Chemistry 4 (1970), S. 541-543 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Tab.
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  • 62
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Z-expansion of two-electron systems is analyzed with the Padé technique with emphasis on establishing analytical properties of the function E(Z) formally associated with the power series expansion. The concept of critical point in this connection is stressed. For this sequence it occurs at Zc = 0.911246 with E(Zc) = -0.415184. The structure of E(Z) for Z 〈 Zc is investigated.The use of Padé approximants to extrapolate values of electron affinities is emphasized.
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  • 63
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    International Journal of Quantum Chemistry 4 (1970), S. 613-623 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Schrödinger equation for helium is written as a generalized eigenvalue equation and this is solved perturbatively for the ground state. The zero order equation is taken to be that of a “six-dimensional hydrogen atom” since, in generalized eigenvalue form, this has a discrete spectrum. Although the zero-order wave function is very poor and gives only 86% of the energy the perturbation procedure is able to improve this to 99% through third-order.
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  • 64
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  • 65
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    International Journal of Quantum Chemistry 4 (1970), S. 289-295 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Hartree-Fock equations are derived in the MO-LCAO approximation for the case when the integrals (except overlap integrals) over the atomic orbitals are charge-dependent. It is shown that inclusion of the overlap matrix in the iterative procedure gives equations which are too complicated for the simple model under consideration. The approach is applied to the VESCF method in the PPP scheme.
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  • 66
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    International Journal of Quantum Chemistry 4 (1970), S. 337-339 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 67
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    International Journal of Quantum Chemistry 4 (1970) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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  • 68
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A multi-configuration LCAO-MO approach using a π-bond order-bond length linear relation is introduced to predict the geometrical structures for the electronic ground and excited states of unsaturated hydrocarbons. The procedure is designed to include configuration interaction in each iterative computation where the π-electron approximation is employed under the Pariser-Parr type semi-empirical treatment.The π-bond order-bond length relation is determined as rpq = 1.523 - 0.193Ppq, when the bond lengths of ethylene, benzene and naphthalene are used and the groundstate functions including the singly and doubly excited configurations are taken into account to obtain the bond orders Ppq.The iterative calculation is applied to the ground state and the two lowest excited states of the benzene anion in both D6h and D2h molecular geometries. The geometrical structures and the π-electron energies are computed for the ground and excited states of the anion; for the latter, two types of configuration species are used. It is found that the first lowest excited state is not subjected to the Jahn-Teller effect and the calculated excited state energies do not agree with the observed values (c. 1.0 ∼ 2.5 eV higher than the observed values). The latter point is discussed in detail. It is also found that the resultant ground state energy depression due to configuration mixing is not very large and the two types of configuration species used give different CI effects on the energy levels of the two lowest excited states of the anion.Finally, the stabilization energy due to the Jahn-Teller distortion is estimated for the ground state of the anion.
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  • 69
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    International Journal of Quantum Chemistry 4 (1970), S. 333-335 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extended method of calculation has been applied to calculate the inter-level differences of the shell of 3d-electrons in the iron group atomic system. The hydrogen-like radial orbitals have been used. The results are compared with those obtained by ordinary methods of calculation as well as with experimental data.
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  • 70
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    International Journal of Quantum Chemistry 4 (1970), S. 355-363 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the approximate calculation of matrix elements with respect to projected Hartree-Fock wave functions is proposed. The method is tested on some calculations in the many-parameter AMO method. It is found that the approximation reduces the amount of work, involved in the evaluation of the energy, by a factor of five and that it reproduces the exact values to within a few per cent.
    Additional Material: 3 Tab.
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  • 71
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    International Journal of Quantum Chemistry 4 (1970), S. 397-411 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe the correlation diagram of a linear crystal, in the traditional framework of the vibronic coupling. All lattice normal modes, except the symmetrical mode, are coupled to the excitation transfer. We therefore propose an iterative method, where every mode “sees” an effective coupling arising from the interaction of the other modes with the electronic excitation. This method is applied to a simple case (the pentamer) and the results are compared with the exact solution. In the weak coupling case this procedure gives the vibronic band structure and in the strong coupling case, the electronic band accompanied by vibrational excitations. These results show that the method employed represents an interpolation approach.
    Additional Material: 4 Ill.
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  • 72
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    International Journal of Quantum Chemistry 4 (1970), S. 487-501 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Wave functions expressed as antisymmetrized products of strongly orthogonal geminals have been evaluated for H2O, NH3 and CH4. The geminals have been expressed as linear combinations of 2 × 2 detors constructed with localized SCF-MO's. Several ground state observables have been computed together with the electric polarizabilities and magnetic susceptibilities. In addition, a configuration interaction calculation limited to all possible double group excitations has been carried out.
    Additional Material: 1 Ill.
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  • 73
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    International Journal of Quantum Chemistry 4 (1970), S. 545-559 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Successive partitioning technique, when based on a modified bordering method for solving a system of linear equations and a relation for the inverse of a partitioned matrix leads to Feenberg's perturbation theory. This sheds light on the properties of the expansion, its bracketing properties and the nature of the “counting operators” used sometimes in this connection.
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  • 74
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    International Journal of Quantum Chemistry 4 (1970), S. 603-612 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Li2 molecule is treated both with the method of moments and with the method of energy variation for the following distances of the nuclei R = 2aH, 4aH, 6aH, 8aH and 10aH. The calculations have been performed with the Hartree-Fock method (HF) and with the method of pseudo-potentials (PSP). The results show that the HF method and PSP method lead practically to the same result. This may be important in the treatment of more complicated molecules.
    Additional Material: 1 Ill.
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  • 75
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    International Journal of Quantum Chemistry 4 (1970), S. 123-124 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 76
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    International Journal of Quantum Chemistry 4 (1970) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 77
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    International Journal of Quantum Chemistry 4 (1970), S. 139-147 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In an earlier paper (Bibliography [1]) it has been shown that approximate representations of excited states of atoms can be obtained from the study of the singularities in the dynamic polarizability. Starting with these wave functions a more accurate calculation of the excited states in the Hartree-Fock scheme can be made by a perturbation treatment. The resulting wave functions yield significantly improved energy values. The 21P, 31P and 41P states of the He sequence up to C4+ are studied. The expectation values of a number of operators are calculated. The results obtained by the present method compare favourably with other elaborate calculations.
    Additional Material: 4 Tab.
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  • 78
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 79
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    International Journal of Quantum Chemistry 4 (1970), S. 203-215 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio molecular orbital calculations of the electronic structure of the sulphate ion have been performed in which three Gaussian-type functions are used to simulate each member of a minimal basis of Slater-type orbitals. Comparative calculations on H2S show that such a basis excellently reproduces the properties of the valence electrons given by calculations in a Slater basis. The expansion of the basis by the addition of sulphur 3d orbitals results in a large decrease in the molecular energy (1 a.u.) and has a pronounced effect on the ordering and energy of the molecular orbitals. The results of a number of semiempirical schemes are discussed in the light of these results.
    Additional Material: 7 Tab.
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  • 80
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    International Journal of Quantum Chemistry 4 (1970), S. 297-313 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A practical method for finding multi-configurational SCF wave functions is proposed. The basic equation is equivalent to the Brillouin theorem; comparison with the usual SCF equations obtained through effective hamiltonians gives an interpretation of the offdiagonal Lagrange multipliers. Numerical applications to Formaldehyde in a minimum Slater-type orbital basis with four different variational wave functions are reported. The molecular orbitals found in these calculations are localized on the chemical bonds. The largest contributions to the energy are obtained from π-π and dispersion-type σ-π correlation.
    Additional Material: 7 Tab.
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  • 81
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    International Journal of Quantum Chemistry 4 (1970), S. 341-341 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 82
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    International Journal of Quantum Chemistry 4 (1970), S. 341-342 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 83
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    International Journal of Quantum Chemistry 4 (1970), S. 223-243 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A large configuration-interaction calculation has been performed to determine the wave function, energy, and molecular properties of CO. The most important configurations were used to obtain the natural geminals and their occupation numbers. A pair-energy approach to the correlation energy was attempted with results which differ significantly from the configuration-interaction results.
    Additional Material: 9 Tab.
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  • 84
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    International Journal of Quantum Chemistry 4 (1970), S. 561-570 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is pointed out that if a many-electron antisymmetric wave function is expanded as a sum of spin-product functions, each multiplied by a function of coordinates, the resulting functions of coordinates have many of the same useful features found with the symmetric and antisymmetric functions representing singlet and triplet states in a two-electron system. For finding the energy, or any function of coordinates only, in the approximation in which spin-orbit interaction is neglected, one such function of coordinates can be used, the spins being disregarded. Simple procedures allow one to find matrix components of such operators as S2 and L . S from the functions of coordinates. These procedures are much easier to visualize than the use of projection operators, the permutation group, or other methods in current use. The general procedures are illustrated by application to the three-electron problem of the lithium atom, as treated by Lunell, Kaldor, and Harris, and their application to the contact hyperfine structure is pointed out.
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  • 85
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    International Journal of Quantum Chemistry 4 (1970), S. 587-602 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propagator or Green's function methods are used to analyze the time-dependent Hartree-Fock model. The non-hermitian matrix problem for the time-dependent Hartree-Fock solution is reduced to a problem related only to hermitian matrices. Particular attention is given to the calculation of oscillator strength in different approximations. The connection between the stability of the Hartree-Fock solution and the solution of the time-dependent Hartree-Fock problem is demonstrated. The results of numerical calculations are given for aniline, azulene and pyridine.
    Additional Material: 3 Ill.
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  • 86
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A group-theoretical method for determining the permitted states of polyatomic molecules, proceeding from given atomic states in which the spin-orbit interaction has been taken into account, is proposed.
    Additional Material: 2 Ill.
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  • 87
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    International Journal of Quantum Chemistry 4 (1970), S. 127-138 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Self-consistent pseudo-eigenvalue equations are explicitly derived for the iterative extended Hückel method with use of the minimum-energy criterion. It is shown that inclusion of the overlap matrix in the iterative procedure gives equations that are too complicated for the simple model under consideration. An expression for the total energy is derived, and it is shown that if the eigenvalues of the pseudo-eigenvalue equations are interpreted as ionization potentials and electron affinities, then the empirical parameters of the Hamiltonian matrix must be reinterpreted. The connection with the Hartree-Fock equations is mentioned. It is proposed that minimizing the energy in the VESCF method should be done in a manner similar to the one used in the iterative Hückel methods. Numerical applications to benzene and pyridine have been made.
    Additional Material: 5 Tab.
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  • 88
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    International Journal of Quantum Chemistry 4 (1970), S. 191-202 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: SCGF calculations are reported for the ground state of ethylene, formaldehyde, acetylene and hydrogen cyanide. A minimum basis of contracted Gaussians was used and optimum hybridization was determined for each of the molecules by systematic variation of the hybridization parameters until the total electronic energy was a minimum. Properties of CH bonds as well as CC, CO and CN σ and π bonds are discussed in some detail. The results show that the assumption of transferable framework integrals β, basic to all semiempirical methods of calculating molecular wave functions, is strictly justified within the SCGF method.
    Additional Material: 2 Ill.
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  • 89
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    International Journal of Quantum Chemistry 4 (1970) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 90
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    International Journal of Quantum Chemistry 4 (1970), S. 315-332 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy bands of sodium have been calculated by the augmented-plane wave method and carried to self-consistency for both a non-spin-dependent and spin-dependent potential. The results are compared with those of previous calculations and with experimental data. It was found that the energy gaps introduced by the spin-dependent potential remained when the calculations were carried to self-consistency. Analysis of the present results involved comparison of the spin-dependent method with Löwdin's Alternant Molecular Orbital method and with Overhauser's Spin-Density-Wave model, and an analogy is drawn between the spin-dependent calculation and spin-polarized atomic calculations. By calculating the total energies as a functional of the self-consistent charge desity, it was determined that the spin-polarized crystal state had a lower energy than the state obtained from the non-spin-dependent potential. The approximations used in the calculations are discussed.
    Additional Material: 3 Ill.
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  • 91
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    International Journal of Quantum Chemistry 4 (1970), S. 342-345 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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