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  • Immunohistochemistry
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  • 2015-2019
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  • 101
    ISSN: 1432-0878
    Keywords: Tubouterine junction ; Innervation ; Immunohistochemistry ; Acetylcholinesterase ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The innervation of the bovine tubouterine junction was studied in sexually mature heifers using antisera against various neuronal markers and a modified acetylcholinesterase method. The vast majority of the nerve fibres in the bovine tubouterine junction belongs to the sympathetic nervous system; peptidergic and cholinergic fibers are restricted to characteristic locations. The endosalpinx in the adovarian portion of the terminal tubal segment is poorly innervated. The mucosa of the aduterine portion and of the tubouterine transitinal region proper receives a strikingly dense innervation, which is observed mainly in combination with a strong vascularisation of specialised mucosal structures. In the endometrium, perivascular nerves accompany the ascending spiral arteries but sporadic contacts between nerve fibres and uterine glands are also observed. From the muscular coat the inner longitudinal layer of the terminal tubal segment is more richly supplied by nerve fibres than the intermediate circular and outer longitudinal layers of the tubouterine junction. No changes in the innervation pattern were seen during the different stages of the sexual cycle.
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  • 102
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 273 (1993), S. 533-545 
    ISSN: 1432-0878
    Keywords: Immunohistochemistry ; Neurotransmitters ; Neuromodulators ; Histamine ; Visual system ; Nervous system, central ; Cupiennius salei (Arachnida)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In this study, immunohistochemistry on Vibracut sections is used to demonstrate anti-histamine immunoreactivity in the brain of the spider, Cupiennius salei (Keys.) (Ctenidae). We describe a system of histamine-immunoreactive neurons within the central nervous system that consists of six omnisegmental neurons. These histamine-immunoreactive neurons form two subgroups: a dorsal system with two cells per hemisphere and a ventral system with only one cell per hemisphere. The cells have extended arborizations in the motor and sensory areas of all neuromeres in the suboesophageal ganglionic mass. We have also found histamine immunoreactivity in the photoreceptors of C. salei and suggest that histamine is a neurotransmitter of photoreceptors in all arthropods, since it is also known to occur in the photoreceptors of the other main arthropod taxa (Merostomata, Crustacea, and Insecta).
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  • 103
    ISSN: 1432-0878
    Keywords: Connexin43 ; Gap junction ; Muscularis externa ; Intestine ; Coronary artery ; Immunohistochemistry ; Mouse ; Dog ; Man ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Electron-microscopic studies have revealed a heterogeneous distribution of gap junctions in the muscularis externa of mammalian intestines. This heterogeneity is observed at four different levels: among species; between small and large intestines; between longitudinal and circular muscle layers; and between subdivisions of the circular muscle layer. We correlated results obtained with two immunomethods, using an antibody to the known gap-junctional protein (connexin43) with ultrastructural findings, and further evaluated the respective sensitivity of these two approaches. For comparative reasons we also included the vascular smooth muscle of coronary arteries into our study. Two versions of the immunotechnique (peroxidase-antiperoxidase and fluorescence methods) were applied to frozen sections of murine, canine, and human small and large intestines, as well as to pig coronary artery. In the small intestine of all three species a very strong reactivity marked the outer main division of the circular muscle layer, while the longitudinal muscle layer as well as the inner thin division of the circular muscle layer were negative. In murine and human colon both muscle layers were negative, while in canine colon the border layer between the circular muscle and the submucosa reacted strongly, and scattered activity was found in the portion of the circular muscle layer (one tenth of its thickness) closest to the submucosa. The remainder of the circular muscle layer and the entire longitudinal muscle layer were negative in the canine colon. In the coronary artery we could not confirm the positive, specific labeling reported by other investigators (l.c.). In conclusion, we found close correlations at all four above-mentioned levels in the distribution of gap junctions in the gut musculature, as determined by binding of anticonnexin43 in comparison to conventional ultrastructural studies. Since no significant immunostaining was found in (i) the outer border of the circular muscle layer of the canine colon and (ii) the border layer between the submucosa and the circular muscle layer of human colon, where rare gap junctions have been identified at the ultrastructural level, we conclude that the electron-microscopic analysis is the more sensitive of the two methods.
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  • 104
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 272 (1993), S. 383-389 
    ISSN: 1432-0878
    Keywords: Mammary gland ; Growth inhibitor ; Epithelium ; Cell types ; Differentiation ; Immunocytochemistry ; Immunohistochemistry ; Cow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Localization of a mammary-derived growth inhibitor (MDGI) in the bovine mammary gland was verified by light-and electron-microscopic methods. Expression of MDGI, which is known to inhibit the growth of mammary epithelial cell lines in vitro, was found to be highest in the late pregnant and in the lactating state. A combination of immunohistochemical and immunocytochemical methods with semi- and ultrathin resin sections revealed marked variations in MDGI staining. High MDGI levels were predominantly detectable in epithelial cells with large milk fat droplets. Distinct cell types that were almost free of label could be identified among bovine mammary epithelial cells that always exhibited high MDGI levels. Similar results were obtained when using a serum-free organ culture system in which MDGI was hormonally induced in cell types of comparable differentiation state. The specific occurrence of the growth inhibitor in developing alveoli and certain cell types points to the association between MDGI expression and functional differentiation in the normal mammary gland.
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  • 105
    ISSN: 1432-0878
    Keywords: Basic fibroblast growth factor ; Trigeminal ganglion ; Immunohistochemistry ; Electron microscopy ; In situ hybridization histochemistry ; Vibrissae ; Hair ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have characterized an antiserum against basic fibroblast growth factor (bFGF) by immunoblot, investigated the location of bFGF-like immunoreactivity (bFGF-IR) in the trigeminal sensory system and perioral skin endowed with vibrissae, and demonstrated the site of bFGF mRNA expression in the vibrissae by in situ hybridization histochemistry. Light-microscopic immunohistochemistry has demonstrated that bFGF-IR is present not only in trigeminal ganglion neurons and their central and peripheral processes, but also in cells of the matrix, external root sheath and papillae of vibrissae and the stratum basale of the stratified squamous epithelium of the skin. Electron microscopy has revealed intense bFGF-IR mainly in cytoplasmic regions, other than the lumen of rough endoplasmic reticulum and the Golgi apparatus, in trigeminal ganglion neurons, in fibroblast-like cells in the papillae, and in capsules of vibrissae. In contrast, actively proliferating and/or differentiating cells in the matrix of vibrissae have intensely stained euchromatin and weakly labeled cytoplasm that, unlike that of the aforementioned cells, contain immunoreaction products in discrete spots less than 100 nm in diameter, implying the generation of different molecular forms of bFGF in cells of the matrix and papillae. Moreover, the accumulation of bFGF in the euchromatin appears to take place in cells at non-mitotic stages (possibly interphases), characterized by a conspicuous nucleolus and well-developed nuclear envelope. A digoxigenin-labeled cRNA probe for the demonstration of bFGF mRNA gives conspicuous hybridization signals mainly in the matrix of vibrissae. These findings suggest that bFGF is involved in the growth and differentiation of matrix cells during certain periods of the cell cycle and that it acts as a non-mitogenic mediator in the adult trigeminal sensory system.
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  • 106
    ISSN: 1432-0878
    Keywords: Chromogranins ; Serotonin ; Histamine ; Regulatory peptides ; Gut ; Monoclonal antibodies ; Immunohistochemistry ; Podarcis sicula (Lacertilia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution, argyrophilia, and the possible amine/peptide co-localizations in endocrine cells immunoreactive (IR) to antisera against chromogranin A (CgA) and chromogranin B (CgB) in the alimentary tract of the lizard Podarcis sicula have been investigated using novel monoclonal antibodies. Many CgA-IR and CgB-IR cells were found in the tract, except in the distal small intestine. Almost all chromogranin-IR cells (Cgs-IR) were also argyrophilic with parallel intensity. Some CgA-IR and CgB-IR cells did not display co-localized amines or peptides. CgA or CgB or both were found co-localized, with some local differences, in almost all serotonin-IR, histamine-IR, substance P-IR and gastric peptide tyrosine tyrosine (PYY)-IR cells. Moreover, both Cgs were co-localized only in some somatostatin-IR cells, whereas neurotensin-IR, gastrin/cholecystokinin-IR, pancreatic polypeptide-IR and intestinal PYY-IR cells did not show any co-localization with Cgs. The presence of Cgs in the endocrine cells was heterogeneous with regard to the complex interrelationship with their amine/peptide content. Consequently, Cgs cannot be considered as universal “markers” of all endocrine cell types.
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  • 107
    ISSN: 1432-0878
    Keywords: Serotonin ; Alimentary canal, insect ; Stomatogastric neryous system ; Immunohistochemistry ; Bioassay ; Electron microscopy ; Leptinotarsa decemlineata (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immunohistochemical studies showed that the alimentary canal of Leptinotarsa decemlineata receives serotoninergic innervation from different neurons in the central and stomatogastric nervous system. The foregut is innervated by the frontal ganglion. Four of the 6–8 large neurons present in this ganglion have axons which run to the musculature of the oesophagus, crop, sphincter, and frontal area of the midgut. They are accompanied by axons from neurons in the suboesophageal ganglion, and by axons from as yet unidentified non-immunoreactive neurons in thebrain and/or the ventral nerve cord. The posterior part of the midgut is essentially devoid of serotoninergic innervation. The hindgut is innervated by two large neurons in the caudal tip of the last abdominal ganglion. The axons always run to the circular and longitudinal muscles of the crop, the circular muscles of the sphincter, and the longitudinal muscles of the hindgut. Immunohistochemical electron microscopy suggests that exocytosis of the immuno-labelled vesicles may occur at some distance from the muscle fibres, implying a neurohormonal release of this neurochemical. A bioassay used to demonstrate the type of effect of serotonin on isolated hindguts in vitro, indicated a clear inhibitory effect on spontaneous contractions at concentrations of 10-8–10-5 M. This effect was dose-dependent. Axons found in association with the cryptonephridial system on the hindgut might be involved in the control of diuresis although we have not tested this possibility experimentally.
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  • 108
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 274 (1993), S. 115-125 
    ISSN: 1432-0878
    Keywords: Autonomic innervation ; Immunohistochemistry ; Intestine, large ; Myenteric plexus ; Neurons ; Neuropeptide colocalization ; Bufo marinus (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution of intrinsic enteric neurons and extrinsic autonomic and sensory neurons in the large intestine of the toad, Bufo marinus, was examined using immunohistochemistry and glyoxylic acid-induced fluoresecence. Three populations of extrinsic nerves were found: unipolar neurons with morphology and location typical of parasympathetic postganglionic neurons containing immunoreactivity to galanin, somatostatin and 5-hydroxytryptamine were present in longitudinally running nerve trunks in the posterior large intestine and projected to the muscle layers and myenteric plexus throughout the large intestine. Sympathetic adrenergic fibres supplied a dense innervation to the circular muscle layer, myenteric plexus and blood vessels. Axons containing colocalized calcitonin gene-related peptide immunoractivity and substance P immunoreactivity distributed to all layers of the large intestine and are thought to be axons of primary afferent neurons. Five populations of enteric neurons were found. These contained immunoreactivity to vasoactive intestinal peptide, which distributed to all layers of the large intestine; galanin/vasoactive intestinal peptide, which projected to the submucosa and mucosa; calcitonin gene-related peptide/vasoactive intestinal peptide, which supplied the circular muscle, submucosa and mucosa; galanin, which projected to the submucosa and mucosa; and enkephalin, which supplied the circular muscle layer.
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  • 109
    ISSN: 1432-0878
    Keywords: Serotonin (5-HT) ; Neurohemal systems ; Immunohistochemistry ; Electron microscopy ; Targeted release ; Leptinotarsa decemlineata (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We analyzed the anatomy of two diffuse neurohemal systems for serotonin in the head of the Colorado potato beetle Leptinotarsa decemlineata by means of immunohistochemistry. One system is formed by axons from two bilateral pairs of neurons in the frontal margin of the suboesophageal ganglion that enter the ipsilateral mandibular nerve, emerge from this nerve at some distance from the suboesophageal ganglion, and cover all branches of the mandibular nerve with a dense plexus of immunoreactive axon swellings. The other system is formed by axons from two large neurons in the frontal ganglion that enter the ipsilateral frontal connectives, emerge from these connectives, and form a network of axon swellings on the labroforntal, pharyngeal, and antennal nerves and on the surface of the frontal ganglion. Immunohistochemical electron microscopy demonstrated that the axon swellings are located outside the neural sheaths of the nerves and hence in close contact with the hemolymph. We therefore suggest that these plexuses represent extensive neurohemal systems for serotonin. Most immunoreactive terminals are in direct contact with the hemolymph, and other terminals are closely associated with the muscles of the mandibles, labrum, and anterior pharynx, as well as with the salivary glands, indicating that these organs are under serotoninergic control.
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  • 110
    ISSN: 1615-2573
    Keywords: Plasminogen activator inhibitor-1 (PAI-1) ; Immunohistochemistry ; Coronary atherosclerosis ; Intima ; Acute myocardial infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Immunohistochemical localization of plasminogen activator inhibitor-1 (PAI-1) was studied using the streptavidin-biotin method in human atherosclerotic coronary arteries. The patients (one male and two females), whose ages ranged from 61 to 78 years, died of anteroseptal acute myocardial infarction without having received any thrombolytic therapy. PAI-1 immunoreactivities (IRs) were mainly detected in the endothelial cells, smooth muscle cells, and collagen fibers of the coronary arterial intima and not in thrombi. Remarkable immunohistochemical staining was seen in intimal collagen fibers. In one patient, intimal PAI-1 IRs partly bordered a thrombus and surrounded a large atheroma rich in cholesterol crystals. Our results suggest that PAI-1 is present in both cellular and extracellular components of human coronary atherosclerotic lesions.
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  • 111
    Electronic Resource
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    Springer
    Environmental biology of fishes 38 (1993), S. 197-208 
    ISSN: 1573-5133
    Keywords: Elasmobranchs ; Holocephalans ; Neuropeptides ; Brain ; Immunohistochemistry ; Reproduction ; Vertebrates ; Evolution ; Chondrichthyes ; Sharks ; Skates ; Ratfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Gonadotropin-releasing hormone (GnRH) is thought to play a fundamental role in the reproduction of cartilaginous fishes. The primary structures of the only form of GnRH in ratfish,Hydrolagus colliei, and one of four forms of GnRH in dogfish,Squalus acanthias, have recently been shown to be identical to a form originally isolated from birds (chicken GnRH-II). Phylogenetic studies indicate that this chicken GnRH-II molecule is the most highly conserved GnRH family member in vertebrates; it is present in animals from cartilaginous fishes to marsupials. However, the presence of four immunoreactive forms of GnRH inS. acanthias, but only one form inH. colliei suggests that the two subclasses of these species diverged a long time ago. Immunocytochemical localization of GnRH shows that it is found in the brains of all chondrichthyans examined to date. GnRH cell bodies and fibers were found in specific patterns throughout the brain in our studies of dogfish shark and black skate,Bathyraja kincaidii. The lack of immunoreactive GnRH fibers in the median eminence and the unique arrangement of the pituitary in Chondrichthyes suggest that transport of GnRH from the brain to the pituitary gonadotropes occurs in the systemic circulation. The use of this unconventional route is further supported by markedly higher levels of serum GnRH in ratfish compared with other vertebrates.
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  • 112
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    International journal of legal medicine 106 (1993), S. 35-40 
    ISSN: 1437-1596
    Keywords: Ki 67 ; Wound age ; Immunohistochemistry ; Ki 67 ; Wundalter ; Immunhistochemie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung In Paraffinschnitten von 77 menschlichen Hautwunden mit einer Überlebenszeit zwischen 3 Std und 7 Monaten wurde das Ki 67-Antigen mit einem monoklonalen Antikörper (MIB) immunhistochemisch dargestellt. Die neugebildete Epidermis zeigte lediglich einzelne, positiv reagierende Keratinozyten, eine verstärkte Reaktivität im Vergleich zu unverletzten Hautarealen war nicht feststellbar. Die epidermalen Basalzellschichten, die dem ursprünglichen Epitheldefekt benachbart waren, wiesen jedoch eine unterschiedlich ausgeprägte Anfärbbarkeit auf. Eine Aussage zum Wundalter war anhand der Zahl positiv reagierender Basalzellen wegen der beträchtlichen intra- wie auch inter-individuellen Streubreite der Befunde nicht möglich. Eine relevant erhöhte Zahl positiv reagierender fibroblastärer Zellen im Wundgebiet verglichen mit unverletzter Dermis trat erstmals in einer 1,5 Tage überlebten Wunde auf und war in allen untersuchten Wunden ab 6 Tagen Überlebenszeit bis zu einem Wundalter von 1,5 Monaten zu beobachten. Lediglich die älteste untersuchte Läsion (Wundalter 7 Monate) zeigte keine relevante Zahl Ki 67-exprimierender Fibroblasten im Narbengewebe. Positive Befunde belegen somit eine Überlebenszeit von mindestens 1,5 Tagen. Das Fehlen einer erhöhten Zahl positiv anfärbbarer fibroblastärer Zellen in einer ausreichenden Anzahl von Präparaten weist auf ein Wundalter unter ca. 6 Tagen hin, kann ein solches allerdings nicht mit letzter Sicherheit beweisen.
    Notes: Summary A total of 77 human skin wounds with a post-infliction interval between 3 h and 7 months were investigated and the proliferation marker antigen Ki 67 was visualized in paraffin sections using a specific monoclonal antibody (MIB). The re-built epidermal layer covering the former lesional area showed only a few basal cells positively staining for Ki 67 antigen. No enhanced reactivity was found when compared to uninjured skin. In basal cells of the epidermis adjacent to the wound area, however, varying numbers of positive cells occurred, but no information useful for a reliable time estimation of skin wounds could be obtained due to the considerable variability in the number of Ki 67 positive epidermal basal cells found in non-damaged skin. Fibroblastic cells in the wound area revealed an increased number of Ki 67-positive sites which could first be detected in a 1.5-day-old skin lesion. Positive results could be obtained in every specimen investigated after a post-infliction interval of 6 days up to 1.5 months. Only the scar tissue of the oldest wound examined (wound age 7 months) revealed no increase in the number of positively staining fibroblasts. Therefore, positive results indicate a wound age of at least approximately 1.5 days and the lack of an increased number of positive fibroblastic cells in a sufficient number of specimens indicates at a wound age of less than 6 days, but cannot totally exclude longer post-infliction intervals.
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  • 113
    ISSN: 1573-0832
    Keywords: Delayed hypersensitivity reactions ; Immunohistochemistry ; Paracoccidioidomycosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The density and distribution of T cells, T helper cells, macrophages and B cells at the site of skin tests with a cytoplasmicParacoccidioides brasiliensis antigen (paracoccidioidin) was studied at 24 and 48 h post-challenge in 10 patients with the chronic form of paracoccidioidomycosis and in 5 non-infected individuals. The in situ study was carried out using immunoperoxidase techniques and monoclonal antibodies. The controls showed negative skin test. In the patients, the great majority of the cells in the perivascular foci were T cells (CD43-positive cells) making up 47% and 48.6% of the total number of cells at 24 and 48 h respectively. Most of the T cells showed a T helper phenotype (CD45RO-positive cells). Approximately 25% of the cells were macrophages (CD68-positive cells) and there were very few B lymphocytes (CD20-positive cells). The present data on the microanatomy of paracoccidioidin skin test sites were consistent with a delayed type hypersensitivity pattern. Our results were comparable to those reported on skin tests for other granulomatous chronic diseases.
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  • 114
    Electronic Resource
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    Springer
    European archives of oto-rhino-laryngology and head & neck 250 (1993), S. 240-244 
    ISSN: 1434-4726
    Keywords: External auditory canal ; Adenoid cystic carcinoma ; Ceruminous glands ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Specimens from five cases of adenoid cystic carcinoma of the external auditory canal were studied by immunohistochemical staining, and findings were compared with those from adjacent non-neoplastic tissues containing ceruminous glands. In the ceruminous gland, cytokeratin showed diffuse positive staining, while myoepithelial cells were stained for smooth muscle actin, desmin, S-100 protein and vimentin. The epithelial markers used were cytokeratin, carcinoembryonic antigen and secretory component and stained at various densities the inner cells of the tubular component and ductlining cells in the cibriform component of tumor tissues. In contrast, the muscular markers, smooth muscle actin and desmin, and the mesenchymal marker, vimentin, were positive in the outer cells of the tubular component and in the cyst-lining cells of the cribriform component. S-100 protein immunoreactivity showed pradoxical results; positive findings occurred in the myoepithelial cells of the ceruminous glands and in the inner cells of the tubular component and duct-lining cells of the cribriform component of the tumor. Present findings demonstrate that adenoid cystic carcinoma of the external auditory canal had dual epithelial and myoepithelial differentiation and can mimic the ceruminous glands of the auditory canal.
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  • 115
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    European archives of oto-rhino-laryngology and head & neck 250 (1993), S. 133-139 
    ISSN: 1434-4726
    Keywords: Lysozyme ; Lactoferrin ; Sinusitis ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Immunohistochemistry was used to study the localization of lysozyme (LZ) and lactoferrin (LF) in the human sinus mucosa during recurrent and chronic sinusitis. Serous cells of submucosal mixed glands and polymorphonuclear leukocytes both displayed a strongly positive staining reaction to both LZ and LF in the normal mucosa. A positive though weak staining for LZ and LF could also be found occasionally within goblet cells. In the mucosa from patients with recurrent or chronic sinusitis, the staining reaction to LZ appeared to intensify in goblet cells. Furthermore, an increased immunoreactivity of glands vis-à-vis LZ and LF was also noted occasionally. Atypical glands were frequently found in mucosa from patients with chronic sinusitis. The epithelium of these latter glands often showed an intense staining reaction to LF, but a rather weak reaction to LZ. The results of the present study suggest that the observed increase in LZ and LF secreting activity of goblet cells, epithelial cells and newly formed atypical glands may play a part in the defense mechanism of the sinus mucosa during the course of chronic sinusitis.
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  • 116
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    European journal of plastic surgery 16 (1993), S. 227-230 
    ISSN: 1435-0130
    Keywords: Giant cerebriform naevus ; Scalp lesions ; Skin expansion ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Giant cerebriform naevi (GCN) are rare scalp lesions which require surgery because of their growth potential and possible malignant behaviour. Three cases of GCN underwent excision and primary repair of the scalp. In one case secondary repair by skin expansion was performed. The histological and immunohistochemical studies showed both melanocytic and neuroid differentiation of the growing cells and characterized the lesions as GCNs. S-100 protein, neurono specific enolase and somatostatin-like cell immunostains were in agreement with the neuroectodermal histogenesis of GCNs suggesting their hamartomatous nature.
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  • 117
    ISSN: 1861-387X
    Keywords: Atypical teratoid/rhabdoid tumor ; Fourth ventricle ; Immunohistochemistry ; Ultrastructure ; Basal lamina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Atypical teratoid/rhabdoid tumor (AT/RT), a recently established central nervous system tumor entity, occurs in children and is more malignant than medulloblastoma/primitive neuroectodermal tumors (PNET). We report here a case of AT/RT in a male infant who was 9 months old at the time of diagnosis. Magnetic resonance imaging revealed that the tumor occupied the fourth ventricle, and at surgery it was found to adhere to the floor of the fourth ventricle. After subtotal removal of the tumor mass, chemotherapy and radiotherapy were performed, but the patient died about 8 months after the diagnosis following rapid regrowth of the residual tumor. Light-microscopically, the tumor was composed mainly of nests of rhabdoid cells with fields of PNET. Occasional mesenchymal and epithelial fields were also evident. Immunohistochemically, these rhabdoid cells were positive for vimentin, epithelial membrane antigen, smooth-muscle actin, cytokeratin, and S-100 protein, and less frequently for glial fibrillary acidic protein. Electron-microscopically, the typical rhabdoid cells contained whorled bundles of intermediate filaments in their cytoplasm. Occasionally, such rhabdoid cells were covered partially by basal lamina at their stromal interface. These findings are typical of AT/RT. Although it is well known that AT/RT often arises in the posterior fossa, detailed reports of cases affecting the fourth ventricle are rare. In this case, the ultrastructural relationship between rhabdoid cells and the basal lamina, which has not so far been described in AT/RT, was of great interest when the nature of the rhabdoid cells was considered.
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  • 118
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 47 (1993), S. 405-423 
    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 numerical method is developed to obtain sequences of functions converging to the eigenfunctions of a Schrödinger operator in the Hilbert space L2(-∞, ∞), whose norm is used to introduce the criterion of convergence in the norm and we show that it guarantees the accurate computation of expected values of a symmetric operator. The method consists in solving the Dirichlet problem associated to the eigenvalue problem in the interval [-n, n] by the Ritz method, whose convergence to both eigenvalues and eigenfunctions is guaranteed by the compactness criterion. Using the asymptotic perturbation theory in L2(-∞, ∞), we prove the convergence of both eigenvalues and eigenfunctions of the Dirichlet problem to those of the unbounded system when the interval [-n, n] is expanded. The method is applied to the harmonic oscillator, the Mitra potential, as well as to the potential V(r) = r and the Coulomb and Yukawa potentials; in each case, the convergence of eigenvalues and eigenfunctions is shown. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Tab.
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  • 119
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 47 (1993), S. 425-435 
    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 present a relativistic theory for the nuclear spin-spin coupling tensor within the polarization propagator approach using the particle-hole Dirac-Coulomb-Breit Hamiltonian and the full four-component wave function. We give explicit expressions for the coupling tensor in the random-phase approximation, neglecting the Breit interaction. A purely relativistic perturbative electron-nuclear Hamiltonian is used and it is shown how the single relativistic contribution to the coupling tensor reduces to Ramsey's three second-order terms (Fermi contact, spin-dipole, and paramagnetic spin-orbit) in the nonrelativistic limit. The principal propagator becomes complex and the leading property integrals mix atomic orbitals of different parity. The well-known propagator expressions for the coupling tensor in the nonrelativistic limit is obtained neglecting terms of the order c-n (n ≥ 1). © 1993 John Wiley & Sons, Inc.
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  • 120
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 47 (1993), S. 437-448 
    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, we present a symmetrical and adiabatic reaction path for hydrogen transfer from methane by methyl by an ab initio method using the 6-31G** basis set with the MP2 corrections for UHF/6-31G** optimized geometries. The theoretical barrier is fitted with the symmetric Eckart function. We, then, take thermal averages of the rate constant (k) considering the discrete nature of the C-H oscillators and the continuous character of the various low-frequency modes of the composite system. Finally, we present a linear relation between log k and temperature. It is shown that this relation gives a good description of the kinetic results of both thermal and photochemical H-transfer reactions in the region of low temperatures. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 151-159 
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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: In the regime of the molecular-orbital theory, a new approach beyond of the Hartree-Fock approximations is proposed. By an appropriate introduction of the quantum fluctuation into the molecular electronic ground state, the Hartree-Fock equations plus Gaussian fluctuation are obtained. Basically, the procedure proposed consists of an adequate utilization of the Gaussian approximation of the Ising model on a lattice (K.G. Wilson et al., Phys. Rep. C 12, 76 (1974)). It leads to an effective nonlinear Hamiltonian for the molecule for studying nonlinear problems in the molecular electronic structure. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 185-200 
    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 review and update a recently developed one-particle theory of N-electron systems that bears a certain resemblance to density functional (DF) theory and has been put forward by the present author. As distinct from DF theory, the new one-particle scheme applies to any N-electron eigenstate including the ground state. For the latter case, the key equations become identical to those familiar from the Kohn-Sham version of DF theory. The theory given here constitutes the basis for a consistent treatment of normal conductivity and superconductivity, which will be discussed in Part II of this article. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 161-183 
    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: An explicitly connected commutator expansion for the average value of an observable in the coupled-cluster theory is derived. Specifically, it is shown that the expectation value of an operator for the state Ψ, related to the Fermi vacuum Φ by the exponential Ansatz ψ = eT Φ, is expressed as a finite commutator series containing the cluster operator T and an auxiliary operator S, defined by a linear equation involving again a finite commutator series in T. The above result is applied to derive the explicitly connected commutator form of the order-by-order many-body perturbation theory (MBPT) expansion for the expectation values and density matrices. We also show how the commutator expansion derived by us can be used as a basis for size-extensive infinite-order summation techniques. An operator technique of eliminating the nonlocal, “off-energy shell” denominators from MBPT expressions is proposed and applied to obtain compact commutator formulas for the expectation values of one- and two-electron operators through the fourth and third order, respectively, and for the correlation energy through the fifth order of perturbation theory. © 1993 John Wiley & Sons, Inc.
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  • 125
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    International Journal of Quantum Chemistry 48 (1993), S. 201-209 
    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 show that a consistent N-electron theory of a solid can within the Born-Oppenheimer (BO) approximation lead only to normal conductivity or to an insulating state. If one leaves the BO approximation by turning on electron-phonon interaction, one can establish a lower-lying new ground state that has the characteristic properties of the Bardeen-Cooper-Schrieffer (BSC) ground state. We demonstrate that an (N + Nn)-particle Schrödinger equation that describes the motion of N electrons and Nn nuclei of a solid can lead only to phonon-induced superconductivity. © 1993 John Wiley & Sons, Inc.
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  • 126
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  • 127
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    International Journal of Quantum Chemistry 48 (1993), S. 219-224 
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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 energy levels in sodium atoms with quarks attached to the nucleus are obtained using the configuration interaction method. It is found that the calculated 3p (2P) → 3s (2S) electronic transition in the Na-1/3 quark-atom system is in agreement with that predicted by extrapolation of experimental data. Also, ionization potentials of fractionally charged sodium atoms are discussed. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 225-232 
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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: A survey is given of the resemblance theorems associated with various types of orthonormalization procedures having different kinds of symmetry properties appearing in the current literature. It is shown that the proofs for the minimum properties are closely connected with the fact that the Hilbert-Schmidt norm of an operator is always nonnegative and has the lowest value equal to zero. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 233-238 
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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: Electric-field maps of certain anions and cations of adenine and guanine have been studied. The results are compared with those of neutral adenine and guanine. In all cases, the geometries were fully optimized using the MNDO molecular orbital method and the fields were computed using Mulliken charges. Reactivities and hydrogen-bonding pattern predicted by electric fields, including those of cations, are in satisfactory agreement with experiment. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 239-247 
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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: In this paper, a general method is presented that allows the derivation of the expansion coefficients of the product of two orthogonal functions provided the generating function is known. For the three classical orthogonal polynomials, the Laguerre, the Hermite, and the Legendre polynomials, the coefficients blmn with φmφn = ∑lblmnφl are derived. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 211-218 
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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: When second-order Jahn-Teller couplings become strong along “streambeds” on potential energy surfaces, instability reflected in negative curvature along a symmetry-lowering distortion coordinate can take place. The point where such negative curvature sets in is usually not a transition state because the gradient of the potential is usually large there. In this paper, it is demonstrated how to use the local energy, local gradient, local Hessian, and knowledge of how quickly the curvature for the symmetry-breaking mode evolves along the streambed (i.e., the derivative of this curvature) to predict how far to move in the symmetry-breaking mode in search of the desired transition state. It is shown that the Hessian matrix evaluated at the symmetry-broken geometry suggested by this analysis has only one negative eigenvalue. Because this analysis is based on a local approximation to the potential, its predictions are, of course, approximate. As such, they only “suggest” the proper direction and magnitude that one should “step” to move toward a transition state. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 249-256 
    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 electronegativity perturbation theory up to the fourth order has been used to study the preferred isomer of linear triatomic molecules. Systems with 10-16 valence-electron systems are discussed and our results are in good agreement with the experiment. The only exception is the isomers of PNO. The usefulness of the perturbation theory is briefly discussed. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 257-265 
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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: Recurrence relations are derived for the evaluation of two-electron repulsion integrals (ERIs) over Hermite and spherical Gaussian functions. Through such relations, a generic ERI or ERI derivative may be reduced to “basic” integrals, i.e., true and auxiliary integrals involving only zero angular momentum functions. Extensive use is made of differential operators, in particular, of the spherical tensor gradient Ylm(∇). Spherical Gaussians, being nonseparable in the x, y, and z coordinates, were not included in previous formulations. The advantages of using spherical Gaussians instead of Cartesian or Hermite Gaussians are briefly discussed. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 48 (1993), S. 267-276 
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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 chain-length dependencies of 2Ag and 1Bu excitation energies as well as their unexpected inversion observed experimentally in trans-polyenes have so far been explained satisfactorily only in terms of configuration interactions within the standard Pariser-Parr-Pople (PPP) parametrization scheme with at least double excitations involving prohibitively large computational labor for long polyenes. A simpler calculation allowing nonzero differential overlap and employing restricted (first-order) single-excitation configuration interaction with chain-length-dependent screened potential is shown to provide an adequate alternative for the studies of those basic spectroscopic features of polyene excited states. The screening factor is parametrized in accordance with the chain-length-dependent behavior of the electrical polarizabilities of polyenes derived within the standard PPP approximation scheme. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 225-225 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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    International Journal of Quantum Chemistry 45 (1993), S. 189-207 
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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 atomic statement of the principle of stationary action determines the theorems that establish the mechanics of an atom in a molecule. The atomic torque, power, and current theorems are derived. They, along with the atomic force, virial, and continuity theorems, provide a complete description of the behavior of matter at the atomic level, including the effects of electric and magnetic fields. The atomic power theorem, for example, enables one to determine the atomic or molecular source of the creation and dissipation of power in combustion or in an explosion. An atom in a molecule is an open system and an atomic equation of motion for an observable contains a component corresponding to the flux in its current density through the atomic surface. The differential form of each theorem yields an equation of motion for the corresponding property density in which the same surface flux appears as a divergence of the current density. The differential and integrated atomic theorems complement those for the total system, enabling one to relate the property to its atomic components and ultimately to a local contribution from each element in real space. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 235-250 
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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: In 1940, Kramers derived an expression for the rate constant of chemical reactions in viscous media. In this theory, chemical reactions are modeled as Brownian processes in the presence of potential barriers. The derivation of the rate constant is based on the solution of the Smoluchowski equation, a Fokker-Planck-type equation in position space. Kramers' theory has been confirmed for reactions in systems ranging from nuclear processes to biochemical problems. The reaction rate can be obtained from the diffusion currents appearing in the Smoluchowski equation. A Smoluchowski-type equation in position space, similar to the one applied by Kramers, has been used to find a nonlinear Schrödinger equation (NLSE) for dissipative, frictionally damped systems, taking into account wave-particle duality. For several potentials, the NLSE can be solved exactly, and analytic expressions for the currents, appearing in the Smoluchowski equation and necessary to determine the rate constants, can be obtained. These currents are not only stationary, but can also be time-dependent. It will be shown that, essentially, the determination of the time-dependence of the currents can be reduced to the solution of Newton-type equations of motion. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 263-294 
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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: This paper considers a Husimi representation of quantum mechanics in which the (stationary) state of a system or ensemble is described by a Husimi function and an observable is described by a phase space function or distribution such that the expectation value of the observable is given by an integral over phase space of the product of that function or distribution and the Husimi function. The density matrix, Wigner function, and Husimi function are considered to be alternative ways of describing the state of a system or ensemble, and methods of recovering the Wigner function or density matrix from the Husimi function are discussed. The classical limits of the Wigner and Husimi functions and of the relationship between them are considered. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 333-347 
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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 nonlocal weighted density approximation (WDA) to the exchange and kinetic energy functionals of many-electron systems proposed several years ago by Alonso and Girifalco in the context of density functional theory is used to compute, within the framework of the spherical jellium model, the ground-state electronic density, chemical potential, and total energy of neutral and negatively and positively charged sodium clusters containing up to N = 800 atoms. From these calculations, we study the behavior of the total energies per atom, chemical potentials, ionization potentials, I(N), and electron affinities, A(N). These results are compared with analogous calculations using the well-known Thomas-Fermi-Weizsäcker-Dirac (TFWD) approximation for the kinetic (TFW) and exchange (D) energy functionals. Calculations including the local density approximation (LDA) to the correlation energy in both WDA and TFWD functionals are also presented. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 363-383 
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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: We derived the necessary conditions to which the vector coupling coefficients (VCC) amn and bmn, describing atomic L, S-multiplets of pMdN and dNs1 configurations (1 ≤ N ≤ 9, 1 ≤ M ≤ 5), should satisfy. It is shown that for two-open-shell systems under consideration the unknown VCC should satisfy not only usual restrictions resulting from the spheric symmetry, but also some additional equation introduced in the present paper in the form of a postulate. VCC obtained were used for the ab initio calculations (by the general SCF coupling operator method) of several transitionmetal atoms and ions with electronic configurations 3d14p1, 3p43d3, and 3p53d3. To check the presented theory, we carried out a detailed comparison between these results and analogous data, obtained by the atomic Roothaan-Hartree-Fock method [2]. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 385-390 
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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 an atom or molecule is expressed in terms of hyperspherical coordinates. The eigenfunction is expanded in a series of orthonormal complete sets: Yλ,μ(Ω), eigenfunctions of generalized angular momentum scalar operator, and Lvn, generalized Laguerre polynomials. The recurrence relation of the expansion coefficients are derived and the eigenvalues can be obtained from the secular equation. © 1993 John Wiley & Sons, Inc.
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    Topics: Chemistry and Pharmacology
    Notes: We have calculated certain dynamic polarizabilities (for both real and imaginary frequencies) for H, He, and H2 and the dispersion-energy coefficients for long-range interactions between them. We have done so in a sum-over-states formalism with explicitly electron-correlated wave functions to describe the states. To be precise, we have determined the dipole (α1), quadrupole (α2), and octupole (α3) polarizabilities of H and He for real frequencies (ω) in a range between zero and the first electronic-transition frequency and for imaginary frequencies (iω) on a 32-point Gauss-Legendre grid running from zero to ħω = 20 Eh, and for H2, we have found the dipole (α), quadrupole (C), and dipole-octupole (E) polarizability tensors for the same real and imaginary frequencies. The dispersion-energy coefficients, obtained by combining the sum-over-states for-malism for the polarizabilities with analytic integration over ω, gave values of C6, C8, and C10 for the atom-atom systems; C06, C26, C08, C28, and C48 for the atom-diatom systems; and C6, C′6 and C″6 for the H2—H2 system. Nearly all the results are considered to be more reliable than those hitherto published and some have been obtained for the first time, e.g., C(iω), E(ω), and E(iω) for H2 and C08, C48, and C48 for the H—H2 system. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 403-403 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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    International Journal of Quantum Chemistry 45 (1993), S. 445-470 
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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: In this paper, the efficient evaluation of the atomic integrals I =∫r1ar2br3cr23λr13μr12νe-αr1-βr2-γr3dτ with one or two factors rij-2 is described. These integrals are necessary for a lower-bound calculation for Li-like systems using the method of variance minimization or Temple's formula. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 409-431 
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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: Coupled-cluster equations for the calculation of the nonexpanded (fully damped) dispersion energy are derived. These equations are solved in the ring approximation using the Møller-Plesset expansion in terms of the fluctuation potentials WA and WB for the individual molecules. Numerical results of high-order perturbative calculations for the He, H2, LiH, H2O, and HF dimers are presented and compared with the converged results computed using the same basis sets. It is found that the convergence of the Møller-Plesset expansion of the dispersion energy in the ring approximation is very fast. The padé approximants still accelerate this already good convergence. For all complexes studied in this paper, the sum of the corrections through the second-order in WA + WB reproduces over 99% of the converged value. The sum of third- and higher-order corrections in the ring approximation is found to be one or two orders of magnitude smaller than the sum of second-order terms not included in the ring approximation and, therefore, may be safely neglected. Thus, it appears that a second-order calculation, which does not require iterating coupled-cluster equations or solving random phase approximation equations, offers the best compromise between accuracy and computational requirements. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 471-484 
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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 integrity bases for representations of the nuclear permutation groups Sn (n = 3,4) in the space of internal coordinates describing AXn molecules are determined. This allows optimal expressions of the molecular potential energy functions in terms of internal coordinates that are totally symmetric with respect to permutations of indistinguishable nuclei. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 45 (1993), S. 491-505 
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    International Journal of Quantum Chemistry 45 (1993), S. 489-490 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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  • 153
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    International Journal of Quantum Chemistry 45 (1993), S. 563-572 
    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 p-version finite element method has been used to calculate second-order pair and total correlation energies for closed-shell Mg and Ar. Comparison with the best results found in the literature suggests that the present values are the most accurate and that the method should perform comparatively better for heavier elements. © 1993 John Wiley & Sons, Inc.
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  • 154
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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: Some topics in relativistic quantum chemistry are reviewed with special emphasis on 4-currents and 4-potentials. It is shown that, both in molecular quantum theory and in solid-state physics, calculations can include relativistic and magnetic effects by means of 4-currents without an excessive increase in complication, provided that 4-component Dirac spinors are used rather than the Pauli approximation. © 1993 John Wiley & Sons, Inc.
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  • 155
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    International Journal of Quantum Chemistry 45 (1993), S. 587-590 
    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: Consider two orbital sets χk, k = 1…m and η1, 1 = 1…n, which are mutually nonorthogonal. Provided that n 〉 m, at least n - m orbitals of the set {η} can be orthogonalized to the set {χ} by a transformation within the set {η}. The orthogonalization of the remaining orbitals of {η} to the set {χ} requires a transformation in which the χk appear explicitly. The orthogonalization of one orbital set to another is relevant for SCF optimizations in a truncated basis set, in the presence of frozen occupied orbitals. Examples are frozen core calculations, ECP calculations, and embedded cluster calculations, where the cluster is embedded in a frozen environment. A simple orthogonalization scheme, which makes use of a corresponding orbital transformation, is presented. It is suggested that with a small, well-defined extension of the set {η} the complete orthogonalization can be done with a transformation in which the {χ} do not appear explicitly. © 1993 John Wiley & Sons, Inc.
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  • 156
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    International Journal of Quantum Chemistry 48 (1993), S. 67-80 
    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: Ground state electron correlation is introduced into the one-particle propagator via coupled cluster theory. This defines a similarity transformation of the Hamiltonian, which leads to the complete separation of the ionization and electron attachment aspects of the propagator. The latter makes it possible to solve for each property independently. Furthermore, the frequency (or energy) dependence which characterizes propagator theory is eliminated by introducing a wave operator formalism. It is shown that this procedure is equivalent to the summation of certain types of terms in the electron propagator perturbation expansion to infinite order. Finally, the resulting equations are found to be equivalent to those of the Fock-space coupled-cluster (or equivalently the equation of motion coupled-cluster) method, which provides an explicit wave function for each state, demonstrating the connection between these different approaches for the calculation of ionization potentials and electron affinities. Understanding this relationship permits new and powerful approximations to be proposed. © 1993 John Wiley & Sons, Inc.
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  • 157
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    International Journal of Quantum Chemistry 48 (1993), S. 155-162 
    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: 7 Tab.
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  • 158
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    International Journal of Quantum Chemistry 45 (1993), S. 71-85 
    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 variational principle for the transition matrix is considered. Conception of the MC SCF (in particular, CASSCF) approach for the transition matrix is proposed as a solution of the variational problem on the optimal evolution of a packet of two stationary states with some additional conditions. An ordinary MC SCF method for a single state is a special case of the proposed approach. Some aspects of the solving of the equations for the optimal transition matrix are treated. The method can be used in atomic and molecular calculations of transition energies, oscillator strengths, and other properties. © 1993 John Wiley & Sons, Inc.
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  • 159
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    International Journal of Quantum Chemistry 45 (1993), S. 105-114 
    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: Some operators considered conventionally as Hermitian are not strictly Hermitian for the freeelectron states known especially in the case of solids. The consequences of this fact on the closure property are examined. © 1993 John Wiley & Sons, Inc.
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  • 160
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    International Journal of Quantum Chemistry 45 (1993), S. 115-117 
    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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  • 161
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    International Journal of Quantum Chemistry 45 (1993), S. 123-132 
    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 barriers to internal rotation about the N—C bond of formamide and the formamide-H2O complex have been examined by ab initio quantum chemistry methods. Both self-consistent field and correlated approaches have been utilized to determine the geometries, energies, and local harmonic vibrational frequencies of the minimum-energy and transition-state structures of these two systems. We find that formamide's rotation barrier of 14-15 kcal/mol is increased to 16-18 kcal/mol when a single H2O molecule is attached. This result contrasts with the effect of a single H2O solvent molecule on the barrier to tautomerization of formamide (to form formamidic acid HN—CHOH) for which a barrier lowering of ca. 20 kcal/mol has been observed. The rotation barriers obtained for formamide and for its H2O complex are compared with barriers obtained experimentally in various solvents. © 1993 John Wiley & Sons, Inc.
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  • 162
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    International Journal of Quantum Chemistry 45 (1993), S. 167-176 
    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 new formulation of the eigenvector equations for certain polymeric molecules is given. The electronic bands for the infinite molecules are deduced. For the finite molecules, the use of ghost molecules allows an exact specialization of the infinite to the finite eigenvector equations. The complete solution of the equations depends on the solution of a simple transcendental equation. Approximate solutions of this equation are given that bracket the accurate solutions so that, for molecules with many repeated moieties, the approximations become good. The general theory is illustrated by applications to the chrysene series and to the polyphenyls. © 1993 John Wiley & Sons, Inc.
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  • 163
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    International Journal of Quantum Chemistry 48 (1993), S. 269-285 
    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 exploit the unitary group formalism in formulating a multiconfigurational single-reference coupled cluster method for cases involving one or two electrons in open shells. The linear version of CCSD theory for the simple open shell case and for low lying singlet states of closed shell systems are considered in detail. The entire formalism is related to the unitary group based CISD method, and explicit expressions for size-extensivity corrections, leading to the L-CCSD formalism, are given. An illustrative example of the minimum basis set model of the BeH radical is also presented. © 1993 John Wiley & Sons, Inc.
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  • 164
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    International Journal of Quantum Chemistry 48 (1993), S. 303-308 
    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: This article gives an improved derivation for U(n1 + n2) ⊃ U(n1) × U(n2), SN1+N2 ⊃ SN1 × SN2, and other transformation coefficients by using a series of elementary Racah transformations. These transformation coefficients can be expressed generally in terms of a product of segments containing 6j symbols and easily calculated. Possible segment factors are given in Table I. © 1993 John Wiley & Sons, Inc.
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  • 165
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    International Journal of Quantum Chemistry 48 (1993), S. 309-319 
    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 electronic structure calculations, carried out in conjunction with rigorous analysis of the resulting wavefunctions, demonstrate that the electronic factors responsible for the unusual stability of the 1,3-dimethylimidazol-2-ylidene carbene are directly related to the substantial σ-backdonation from the carbenic carbon to the adjacent nitrogen atoms. The π-donation is found to play only a minor role, ruling out the presence of significant stabilization due to ylidic resonance structures. The unusually large proton affinity of the carbene is explained by the extra π-electron stabilization of the corresponding 1,3-dimethylimidazolium cation. The MP2/6-311++G** level of theory is found to be sufficient for accurate predictions of the geometries of the imidazol-2-ylidene carbenes. © 1993 John Wiley & Sons, Inc.
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  • 166
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    International Journal of Quantum Chemistry 48 (1993), S. 331-341 
    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
    Notes: Vibration frequencies for 2-aminoethanol, neutral glycine, glycolic acid, n-propylamine, n-propanol, and propionic acid were calculated on the ab-initio RHF level with a variety of standard basis sets including polarization and diffuse functions. Experimental frequencies, if available, are compared with these data and basis set suitability is discussed on the basis of this comparison. © 1993 John Wiley & Sons, Inc.
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  • 167
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    International Journal of Quantum Chemistry 48 (1993), S. 355-361 
    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 kinetic energy component is shown to be a well-defined quantity in the divide-and-conquer method. This kinetic energy converges to the conventional Kohn-Sham kinetic energy when the numbers of the “buffer atoms” for subsystems increase. Numerical results from sample calculations confirm that the kinetic energy component converges to the Kohn-Sham value as the basis set increases. © 1993 John Wiley & Sons, Inc.
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  • 168
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    International Journal of Quantum Chemistry 48 (1993), S. 479-490 
    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: Results of an ab initio SCF (4-31G) study of the potential energy surface of 4-aminobutanol are reported. Four different intramolecular hydrogen bonds are present in the various local minima: N … H—O, N—H … O, C4—H … O, N … H—C1. These interactions are discussed and compared with those present in the homologues 3-aminopropanol and 2-aminoethanol. © 1993 John Wiley & Sons, Inc.
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  • 169
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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: Many-body perturbation theory is applied to the nitrogen triple bond for bond distances ranging from the atomic regime to about 0.6a0 shorter than equilibrium. A full-optimized reaction space model is used to compute orbital spaces with an even-tempered gaussian-type basis set and also with a nominal Bagus-Gilbert Slater-type basis set. Conservation of orbital angular momentum in the atomic regime leads to perturbative theory for Hartree-Fock plus proper dissociation. Angular momentum conservation can also be enforced with a scaled Slater-Condon parameter. Third-order dissociation energies and spectroscopic constants approach limits of the chosen basis sets. © 1993 John Wiley & Sons, Inc.
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  • 170
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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 structure of 2,3-diketopiperazine in a crystal phase (P21/c), modeled by a 13-molecule cluster surrounded by point charges, was completely optimized using standard gradient procedures. The (ab initio) MIA approach was used to perform the SCF step, which using a 4-21G basis set, involves calculations using 1092 basis functions. Results are in very good agreement with experimental (X-ray) data, in contrast to a previous study in which a model was used consisting of only point charges. © 1993 John Wiley & Sons, Inc.
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  • 171
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    International Journal of Quantum Chemistry 46 (1993), S. 87-100 
    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: Hartree-Fock calculations of the molecular geometry and electronic properties (ionization potentials) of bare Nin clusters (n = 3, 7, 13, and 25) and nickel clusters bearing a chemisorbed CH3 radical are reported. A basis of double-zeta quality on light atoms including carbon and a model core potential along with double-zeta plus polarization auxiliary basis set for nickel atoms have been used. Computed properties serve to assess cluster-size convergence when nickel atoms core electrons are described with [1s-3d] pseudopotentials. In spite of their simplicity, results with these potentials are in good agreement with previously reported theoretical and experimental data on seven-atom clusters. This suggests that the cluster-model approach to surface bonding using simple pseudoopotentials can lead to meaningful results and tractable computationl times when applied to larger chemisorbed organic molecules. Thus, this approach may be adequate to help find out direct experimental evidence of the interfacial bonding for grafted structures obtained under cathodic electropolymerization of acrylonitrile on nickel surfaces. © 1993 John Wiley & Sons Inc.
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  • 172
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    International Journal of Quantum Chemistry 46 (1993), S. 101-107 
    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
    Notes: There exist problems in condensed-matter theory that require evaluating infinite Bloch sums of multipolar potential r-l-1Yl,m(θ,ϕ) on a periodic lattice. For an arbitrary multipolar order l, tractable formulas are given for summing such interactions on a two-dimensional Bravais lattice and evaluating their Bloch sums at a point outside as well as inside the plane of the lattice. The approach used is the Ewald method, which consists of separating the original series in rapidly converging sums in reciprocal and real spaces. Computational aspects of the present formulation are briefly reviewed. © 1993 John Wiley & Sons, Inc.
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  • 173
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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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  • 174
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    International Journal of Quantum Chemistry 46 (1993), S. 271-294 
    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 Structure and the energy of the stable conformations of the two possible stereochemical configurations of 2,4-diphenylpentane are obtained using the ab initio molecular orbital theory. The objective was to mimic the possible structures and determine the corresponding energies of the dyads of syndiotactic and isotactic polystyrene and, consequently, to study the interactions between the phenyl groups. The results of complete geometry optimization showed significant changes in geometrical parameters compared with those expected from the ideal hydrocarbon structure. The steric strain is most pronounced in some of the gauche conformations where large (approximately 40°) distortions of the backbone torsional angles and/or simultaneous phenyl group rotations in the range of 30°-40° away from its global minimum position may occur. In addition to the discussion of the geometrical parameters, the corresponding dipole moments are also calculated and differences related to the various structures and discussed. © 1993 John Wiley & Sons. Inc.
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  • 175
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    International Journal of Quantum Chemistry 46 (1993), S. 319-333 
    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 eigenvalues of the Schrödinger equation with a polynomial potential are calculated accurately by means of the Rayleigh-Ritz variational method and a basis set of functions satisfying Dirichlet boundary conditions. The method is applied to the well potentials having one, two, and three minima. It is shown, in the entire range of coupling constants, that the basis set of trigonometric functions has the capability of yeilding the energy spectra of unbounded problems without any loss of convergence providing that the boundary value α remains greater than a critical value αcr. Only the computation of the nearly degenerate states of multiwell oscillators requires dealing with a relatively large truncation order. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 46 (1993), S. 339-341 
    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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  • 177
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    International Journal of Quantum Chemistry 46 (1993), S. 119-125 
    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 lowest-energy N4 is computed ab initio to be the planar C2h(3Bu) open-chain structure 13. The open-chain N4 singlet-state structures dissociate on geometry optimization. The tetraazatetrahedrane Td structure 1 and the tetrazete D2h structure 2 are minima at MP2/6-31G*. However, both are higher in energy than 13 (24.1 and 21.2 Kcal/mol [UQCISD) (T)(full)/6-311+G*//MP2/6-31G* + ZPE(MP2/6-31G)*, respectively]. The energy of 13 is 157.5 kcal/mol higher than that of two N2(1∑g+ molecules [UQCISD(T)(Full)/6-311+G*//MP2/6-31G*] © 1993 John Wiley & Sons, Inc.
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  • 178
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    International Journal of Quantum Chemistry 46 (1993), S. 671-671 
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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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  • 179
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    International Journal of Quantum Chemistry 46 (1993), S. 673-674 
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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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  • 180
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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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  • 181
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    International Journal of Quantum Chemistry 48 (1993), S. 815-826 
    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: Many xenobiotics containing N or S heteroatoms are metabolized by the cytochrome P450s, leading to a variety of products which can be toxic, carcinogenic, or detoxifying. Thus, it is important to try to establish molecular criteria that modulate competitive product formation for these types of compounds. In the absence of 3D structures for the P450 isozymes that are responsible for the oxidations of N- and S-containing compounds, we have focused here on the characterization and identification of possible electronic and thermodynamic factors that could be modulators of different types of product formation. Specifically, the competition among N-oxidation, N-hydroxylation and Cα-hydroxylation for three amines were examined. Similarly, three thioethers were studied for their internal competition between S-oxidation and Cα-hydroxylation. The results obtained indicate that the stability of the cation radical intermediate formed by the one electron transfer mechanism is not a determinant of differences in product distribution between the two types of compounds. Rather, relative product stability appears to be a significant modulator of product distribution explaining why S-oxide formation is favored over N-oxide and why Cα-hydroxylation is usually favored over N-oxide formation in amines. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 46 (1993), S. 711-734 
    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: This work analyses the adequacy of an analytical electrostatic energy formulation within the CNDO framework to predict the stable conformations of large molecular complexes. Comparisons are made with abinitio results for small systems such as water-formamide, methanol-water-imidazole, or guanine-cytosine and with AM1 results for two large systems: a molecular tweezer + the 9-methyladenine complex and a model active site of the α-chymotrypsin and its ligand complex. This approach is efficient in providing reliable confromers for large molecular systems in a very fast way. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 46 (1993), S. 425-474 
    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 introduce a method for the explicit computation of the eigenvalue problem of the evolution operator of mixing dynamical systems. The method is based on the subdynamics decomposition of the Brussels-Austin groups directed by Professor I. Prigogine. We apply the method to three different representatives of mixing systems, namely, the Renyi maps, baker's transformations, and the Friedrichs model. The obtained spectral decompositions acquire meaning in suitable rigged Hilbert spaces that we construct explicitly for the three models. The resulting spectral decompositions show explicitly the intrinsic irreversibility of baker's transformations and Friedrichs model and the intrinsically probabilistic characters of the Renyi maps and baker's transformations. The dynamical properties are reflected in the spectrum because the eigenvalues are the powers of the Lyapunov times for the Renyi and baker systems and include the lifetimes for the Friedrichs model. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 46 (1993), S. 483-498 
    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 new base pair (called κ-π) of Watson-Crick type, with a H-bond pattern different from that in A-T and G-C base pairs, has been recently synthesized and shown to be stable and incorporable into duplex DNA and RNA by polymerases. This new basepair, which contains three H-bonds, is compared with G-C, in the framework of modern dynamical theory of quantum nonlocality and quantum correlations. Connection with the traditional treatment of proton transfer in DNA base pairs, which uses the adiabatic approximation, is explicitly made. As a result, the dynamics of the H-bond pattern of G-C is shown to exhibit a specific quantum mechanical phase stability, which is clearly missing in the case of κ-π. This finding is discussed and illustrated, also in connection with recent quantum chemical calculations of proton transfers in DNA base pairs. Additionally, certain speculations concerning the “evolutionary advantage” of G-C with respect to κ-π are briefly considered. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 46 (1993), S. 475-481 
    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: Band structure with a quasicontinuum of electronic states near the Fermi surface (FS) of a solid-state matter indicates overlapping regions of the electronic and phonon spectra: (εP - εQ) ≈ ℏωv. This simple fact has an important impact on the theoretical aspects of the description and a study of an electronic structure and physical properties of a matter since velocities of the nuclei and electrons are on the same scale. The motion of the electrons is not adiabatic and the description of the electronic structure of a system cannot be based on the assumption of the validity of Born-Oppenheimer approximation. For nonadiabatic systems in contrast to the descripton of adiabatic systems [(εp - εQ) 〉 ℏωv], an effect of the finite mass of the electrons, i.e.· nonadiabatic corrections, cannot be calculated by a perturbation theory due to the divergency of a perturbation expansion. Quasiparticle transformation technique has disclosed the unexpected effects of nonadiabaticity on the electronic structure and physical properties of matter. The aspects of superconductivity are discussed. © 1993 John Wiley & Sons, Inc.
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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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  • 187
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    International Journal of Quantum Chemistry 46 (1993), S. 499-504 
    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 advocated that the H-bond patterns of the standard C-G and A-T base pairs have an evolutionary advantage over any other H-bond scheme accommodated within the Watson-Crick-type geometry. A suggested proof of the statement is given by the Longuet-Higgins' sign-reversing loop argument. The present analysis indicates a close relation with self-organizational principles. © 1993 John Wiley & Sons, Inc.
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  • 188
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    International Journal of Quantum Chemistry 46 (1993), S. 505-510 
    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: Some elementary properties of a general linear operator, which is defined on a Hilbert space but is not necessarily self-adjoint, are briefly reviewed: the classical canonical form, the bi-orthogonality theorem, the bivariational principle, the spectral resolution of the resolvent, and the properties of exponential forms. © 1993 John Wiley & Sons, Inc.
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  • 189
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    International Journal of Quantum Chemistry 46 (1993), S. 515-518 
    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: Squeezed states are normally studied in configuration space or using the Glauber formalism for the coherent states. Here we show that the use of the Fock-Bargmann space can lead to more general solutions, especially in the case of squeezed states associated with the square of field amplitude. The relations that we obtain are completely general and several well-known, approximate results can be obtained as the limit cases of our approach.© 1993 John Wiley & Sons, Inc.
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  • 190
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    International Journal of Quantum Chemistry 46 (1993), S. 535-576 
    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: An ab initio method for the calculation of atomic and molecular electronic wave functions is presented. The “Optimized-Basis-Set Multiconfiguration Spin-Coupled” (OBS-MCSC) method may be viewed either as a multiconfiguration generalization of the spin-coupled approach or as a nonorthogonal variant of the MCSCF method. In addition, the OBS-MCSC method optimizes the basis-set exponential parameters simultaneously with all other variational parameters, through a second-derivative minimization procedure. Explicit analytic expressions for the required first and second derivatives of the energy with respect to all variational parameters are obtained. Test calculations prove the capability of the method to yield compact yet accurate electronic wave functions.© 1993 John Wiley & Sons, Inc.
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  • 191
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    International Journal of Quantum Chemistry 46 (1993), S. 583-587 
    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 Colle-Salvetti second-order reduced density matrix (2-matrix) is an approximation to the 2-matrix obtained from a wave function that is a product of a reference wave function containing little or no correlation times a product of correlation factors that are functions of the coordinates of pairs of electrons. A formal proof is given for the non-N-representability for the Colle-Salvetti 2-matrix using the nonnegativity condition of the 2-matrix. The nonnegativity condition of the particle-hole overlap matrix (G matrix) is also not satisfied. The proof is valid for Colle-Salvetti 2-matrices obtained from both the Hartree-Fock and small multiconfigurational-self-consistent-field wave functions. Even though the Colle-Salvetti 2-matrix is not N-representable, it does satisfy the Pauli principle component of the G-matrix condition because it reduces to an N-representable first-order reduced density matrix. © 1993 John Wiley & Sons, Inc.
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  • 192
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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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  • 193
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    International Journal of Quantum Chemistry 46 (1993), S. 593-607 
    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 unrestricted complete active space self-consistent field (UCASSCF) function is defined, and a proof that a UCASSCF eigenfunction of the spin operator S2 is a CASSCF function is given. The spin-contamination for an unrestricted Hartree-Fock (UHF) function is evaluated by using Araki angle operators, and the UHF function is then projected on the restricted open-shell Hartree-Fock (ROHF) space. The present analysis has deep consequences since it implies that the only non-spin-contaminated UHF functions are the ROHF functions. This is illustrated in a calculation of the spin density of He2+. © 1993 John Wiley & Sons, Inc.
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  • 194
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    International Journal of Quantum Chemistry 46 (1993), S. 609-622 
    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 hydrogen atom in a semi-infinite space limited by a hyperboloidal boundary, with the nucleus at a focus, is investigated as a model of an atom on the surface of a solid. The energy eigenvalues, hyperfine structure, and electric dipole moment of the system are evaluated for different focal distances and eccentricities of the boundary. It is shown that the system tends to become infinitely degenerate at the ionization threshold as the boundary closes in approaching the nucleus. This model includes as special cases the corresponding models in the literature with plane and paraboloidal boundaries. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 195
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    International Journal of Quantum Chemistry 46 (1993), S. 623-634 
    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 structure and energetics of the complexes formed between SCO/He and SCO/N2 were investigated using ab initio wave functions at both the SCF and correlated levels of theory with a medium-sized polarized basis set. The energy of the T-structure for SCO⃛He was found to be lower than the energy of the corresponding linear complexes with He bonded to the oxygen or sulfur atoms. Two linear structures for SCO⃛ He were found to be nearly isoenergetic. There is only a small difference in energy between the T-structure for SCO⃛N2 and the OCS⃛N—N colinear structure, with the T-structure being the lowest. The electron correlation contributions to the interaction energy were calculated using Möller-Plesset perturbation theory at the MP2, MP3 and SDTQ-MP4 levels. Analysis shows the importance of the triple excitations in these complexes. © 1993 John Wiley & Sons, Inc.
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  • 196
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    International Journal of Quantum Chemistry 46 (1993), S. 635-649 
    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: Three hierarchically ordered topological factors, i.e., atom connectivity, centrality, and cyclicity, were found to control the number of self-returning walks (SRWS) associated with every atom in the molecule. The reversal of their order was observed in a few cases where the central location of atoms had a stronger influence than did their connectivity on the number of SRWS. Three atomic topological indices, i.e., the Morgan extended connectivity, the Balaban, Mekenyan, and Bonchev hierarchical extended connectivity, the Randić atomic path code, were found to closely match the ordering of atoms in molecules determined by their number of SRWS. New atomic graph invariants fi = lim SRWin/SRWn and ti = fi · SRW2 were specified and may find application in QSAR and QSPR. The ti indices are nonintegers close to atomic valence. The fi indices represent the limit of the number of SRWS of length n for the atom i, SRWin, normalized by dividing it by the total number of SRWS for the molecule. In the case of Hückel MO considerations, these invariants were shown to be numerically equal to the partial electronic charges of the lowest occupied molecular orbital (LOMO). A new class of isocodal atoms (atoms having the same number of SRWns) was observed, i.e., atoms that become isocodal only at n ≥ 1. A number of open questions following from these findings were formulated, including the possibility for a topological modeling of electron correlation. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 47 (1993), S. 213-223 
    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 a numerical experiment, the dynamics of natural decay of a metastable state is shown to be strongly affected by the presence of an external time-varying electric field of high intensity. The metastable state, depending upon its level width, is shown to be stabilized by a near-resonant electric field. The applied field may even cause population transfer to a neighboring bound level that is not directly populated by the natural decay process. The effects of continuous and pulsed perturbations are both analyzed numerically, and perturbation, theoretically. © 1993 John Wiley & Sons, Inc.
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  • 198
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    International Journal of Quantum Chemistry 47 (1993), S. 225-229 
    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 previously described optimization of small Gaussian expansions, to be employed for the computation of many-center two-electron integrals over Slater basis sets, has been extended, with some refinements, up 4d orbitals. © 1993 John Wiley & Sons, Inc.
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  • 199
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    International Journal of Quantum Chemistry 47 (1993), S. 177-183 
    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: An attempt has been made to study the effect of a nonuniform positive background on the ground-state energy of a nonmagnetic Wigner lattice. The background is modified with a variable “ripple” parameter in the background charge, represented by a Yukawa-type charge distribution. Our calculation shows that a Yukawa-type background leads to a lower ground-state energy value compared to a Gaussian-type and constant positive background. © 1993 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 47 (1993), S. 231-238 
    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 helical region of the potential energy surface of blocked α-aminoisobutyric acid (Aib) dipeptide has been studied by using ab initio and semiempirical quantum mechanical methods, as well as force-field-derived methods. Depending on the method, an α-helix or a 310-helix is found to be the energy minimum. The conformations obtained from computations performed at the ab initio quantum mechanical level, as well as by using the AMBER force field, are in excellent agreement with X-ray data. Semiempirical results display some important differences with regard to experimental data. On the other hand, the CVFF force field predicts no energy minimum in the helical region of the Aib potential energy surface. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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