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  • Magnetic resonance imaging
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  • 2000-2004
  • 1985-1989  (1.410)
  • 1935-1939
  • 1920-1924
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 299-302 
    ISSN: 1279-8517
    Schlagwort(e): Cryomicrotomy ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé La réalisation de coupes congelées dont l'épaisseur varie entre 5 et 50 μm, sur prélèvements cadavériques humains frais et non décalcifiés a été mise au point en Suède par l'un des auteurs en 1983. Cette technique permet d'obtenir des images anatomiques de haute définition qui ont été corrélées avec des coupes en IRM réalisées à des intervalles de 20 μm.
    Notizen: Summary The performance of frozen sections of a thickness varying between 5 and 50 μm in fresh undecalcified cadaveric human specimens was perfected in Sweden by one of the authors in 1983. This technique makes it possible to obtain anatomic images of high definition which were correlated with MRI sections made at intervals of 20 μm.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 303-314 
    ISSN: 1279-8517
    Schlagwort(e): Magnetic resonance imaging ; Ultrasonography ; Heart
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Les auteurs présentent un travail de corrélation entre l'aspect anatomique du cœur et les images obtenues en imagerie par résonance magnétique (IRM) et en échographie. Six cœurs ont été étudiés par IRM puis découpés suivant les mêmes plans de coupe. Les résultats sont présentés et comparés aux données obtenues in vivo chez des volontaires à la fois en IRM et en échographie. La corrélation entre images IRM de pièces anatomiques et coupes anatomiques est excellente, les plus fins détails anatomiques étant reproduits. L'utilisation de coupes en double obliquité permet l'obtention d'incidences similaires à celle de l'échographie. Ces mêmes incidences peuvent être obtenues in vivo. L'étude morphologique du cœur est ainsi extrêmement précise, de même que l'étude des volumes cardiaques.
    Notizen: Summary The authors present a correlation study between the anatomy of the heart and its appearance with magnetic resonance imaging (MRI) and ultrasonography (US). Six hearts were studied by MR, then sliced along the same planes. The results are presented and compared with the data obtained in volunteers by MRI and ultrasonography. The correlation between the MRI of isolated hearts and their anatomic slices is excellent, the thiniest anatomic details are reproduced. The use of double oblique slices provides incidences similar to those of ultrasonography. The same incidences can be obtained in vivo. The morphologic study of the heart by these imaging techniques is thus very precise, as well as the study of cardiac volumes.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 65 (1987), S. 101-109 
    ISSN: 1432-1440
    Schlagwort(e): Blood Pressure ; Hypertension ; Salt ; Sodium ; Genetics ; Twin Model ; Salt Restriction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To examine the effect of genetic variance on blood pressure, sodium homeostasis, and its regulatory determinants, we studied 37 pairs of monozygotic twins and 18 pairs of dizygotic twins under conditions of volume expansion and contraction. We found that, in addition to blood pressure and body size, sodium excretion in response to provocative maneuvers, glomerular filtration rate, the renin-angiotensin system, and the sympathetic nervous system are influenced by genetic variance. To elucidate the interaction of genetic factors and an environmental influence, namely, salt intake, we restricted dietary sodium in 44 families of twin children. In addition to a modest decrease in blood pressure, we found heterogeneous responses in blood pressure indicative of sodium sensitivity and resistance which were normally distributed. Strong parent-offspring resemblances were found in baseline blood pressures which persisted when adjustments were made for age and weight. Further, mother-offspring resemblances were observed in the change in blood pressure with sodium restriction. We conclude that the control of sodium homeostasis is heritable and that the change in blood pressure with sodium restriction is familial as well. These data speak to the interaction between the genetic susceptibility to hypertension and environmental influences which may result in its expression.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-0460
    Schlagwort(e): Neurogenic dysphagia ; Magnetic resonance imaging ; Computed tomography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Dysphagia due to CNS pathology usually stems from one of two patterns of disease: (1) bilateral corticobulbar tract dysfunction (“pseudobulbar palsy”) or (2) pontomedullary dysfunction (“bulbar palsy”). Computed tomography (CT) has proved to be useful for evaluating the brainstem in patients with neurogenic dysphagia. Nonetheless, artifacts are common in CT imaging of the posterior fossa. Also, direct sagittal imaging is not usually obtainable by CT in adult patients. Magnetic resonance imaging (MRI), in contrast to CT, simultaneously gathers sequential images in the same plane and can obtain direct reconstructions in any plane of interest. MRI has proven to be more sensitive than CT in demonstrating lesions of the brain, such as demyelinating (e.g., multiple sclerosis) and ischemic diseases, (Brant-Zawadzki et al. 1984, Bradley et al. 1984, Bydder et al. 1982, Sheldon et al. 1985) as well as neoplastic masses that may produce neurogenic dysphagia (Lee et al. 1985, Zimmerman et al. 1986). Five patients with dysphagia are reported for whom MRI was valuable in detecting and characterizing their lesions of the brainstem and the cerebral hemispheres.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 107-121 
    ISSN: 1279-8517
    Schlagwort(e): Magnetic resonance imaging ; Liver ; Topographic anatomy ; Frontal (coronal) sections
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Habituellement, les coupes frontales du foie en résonance magnétique sont moins utilisées que les coupes passant par les autres plans de l'espace. Des coupes frontales du tronc en résonance magnétique intéressant le foie, réalisées chez plus de 80 patients pour des indications diverses, ont été confrontées avec des coupes frontales du tronc faites sur 10 cadavres. Un schéma général de l'anatomie du foie étudiée dans le plan frontal a été établi. Les coupes frontales en résonance magnétique permettent de faire une très bonne estimation de la morphologie et du volume du foie, et d'en reconnaître les variations individuelles. Elles montrent bien certains rapports inférieurs du foie. Surtout, les coupes frontales en résonance magnétique permettent d'identifier la plupart des principales veines du foie, veines sus-hépatiques et branches de la veine porte et de bien étudier toute la portion rétro-hépatique de la veine cave inférieure. Certaines images vasculaires sont retrouvées presque constamment d'un sujet à l'autre sur les coupes. Le foie droit se prête mieux à cette étude que le foie gauche, en raison de sa morphologie et de la disposition de ses veines. Les coupes frontales du foie en résonance magnétique représentent un moyen privilégié pour étudier l'anatomie du foie. Associées à des coupes transversales, elles permettent de préciser le siège et les rapports veineux à l'intérieur du foie d'un processus pathologique, en vue d'une hépatectomie.
    Notizen: Summary In general, frontal sections of the liver in magnetic resonance imaging are used less than sections passing through other planes of space. Frontal sections of the trunk in magnetic resonance imaging involving the liver, performed in over 80 patients for various reasons, were compared with frontal sections of the trunk made in 10 cadavers. A general schema was established of the anatomy of the liver studied in the frontal plane. Frontal sections in magnetic resonance imaging make it possible to form a very good estimate of the structure and size of the liver, and to recognize individual variations. They clearly show certain inferior relations of the liver. In particular, frontal sections in magnetic resonance imaging make it possible to identify most of the main veins of the liver, the main lobar veins and branches of the portal vein, and to properly study the entire retrohepatic portion of the inferior vena cava. Some of the vascular images were found almost constantly in the sections of the various subjects. The right lobe of the liver is more accessible to such study than the left by reason of its structure and its venous arrangements. Frontal sections of the liver in magnetic resonance imaging constitute a preferential method for studying the anatomy of the liver. Together with transverse sections, they make it possible to specify the site and venous relations of a pathologic process within the liver, with a view to hepatectomy.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 141-149 
    ISSN: 1279-8517
    Schlagwort(e): Magnetic resonance imaging ; Thoracic aorta ; Gated acquisition ; Oblique slices ; Flow Phenomena
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Les auteurs présentent les résultats d'une investigation concernant l'imagerie par résonance magnétique de l'aorte thoracique d'après l'étude de huit volontaires et d'un patient suspect de maladie de Takayasu mais ayant une aorte morphologiquement normale. Des coupes axiales, frontales, sagittales et obliques ont été réalisées et les résultats morphologiques sont présentés. De plus, les principaux phénomènes de flux sont expliqués et des exemples de chacun sont montrés.
    Notizen: Summary The authors present the results of magnetic resonance imaging (MRI) in the investigation of the anatomy of the thoracic aorta in a group of eight volunteers and in one patient with presumptive Takayasu's disease but with normal aorta. Transaxial, coronal, sagittal and oblique slices were made and the morphologic results are presented. Major flow phenomena are also discussed and some examples given.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-1920
    Schlagwort(e): Colloid cyst of the third ventricle ; Third ventricle ; Brain tumor ; Computer tomography ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Two cases of colloid cyst of the third ventricle are reported. Their computed tomographic (CT), magnetic resonance (MR) and neuropathological features are presented. The MR findings were different in the two cases for reasons not yet fully explained, full biochemical and biophysical analyses of the cyst contents not being available. Neuropathologically, the only significant difference was the abundant presence of cholesterin crystals in the colloid of case 1 and their absence in case 2. One of our cases is also peculiar from a CT point of view, since it was primarily hypodense and did not enhance on intravenous contrast administration.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 120-126 
    ISSN: 1432-1920
    Schlagwort(e): Magnetic resonance imaging ; Cerebral infections
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 18 patients with cerebral infections were investigated with a 1.5 Tesla-Magnetom. The results are compared to CT-findings obtained at the same time. In the majority of cases (n=11) MR is superior to CT because it allows earlier detection of the disease, a more exact definition of the spread and a more detailed representation of complex inflammatory processes. MRI should rank first among all examination methods, especially in the determination of herpes simplex-encephalitis as it allows earlier detection and treatment of this disease.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-1920
    Schlagwort(e): Magnetic resonance imaging ; Systemic lupus erythematosus ; Behcet's disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We performed MR (magnetic resonance) brain imaging on 24 patients with a systemic vasculitis. MRI proved to be a sensitive method for detecting brain lesions (clinically silent or manifest) in these patients. The most frequent abnormalities were periventricular lesions seen in 12 cases. Such changes are not specific for vascular disease, and are often seen in multiple sclerosis. However, additional changes were commonly seen which suggested the correct diagnosis.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1432-1920
    Schlagwort(e): Magnetic resonance imaging ; Gadolinium-DTPA (Gd-DTPA) ; Brain infarction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Five patients (1 female and 4 males) with cerebral infarction of 4 h to 27 months duration were studied 9 times with magnetic resonance (MR) using Gd-DTPA. Spin-echo (SE) MR images (MRI) were obtained before and after the administration of Gd-DTPA, and correlative CT scans were performed on the same day. In 2 cases, 4 h and 27 months after the ictus, there was no enhancement with Gd-DTPA. There was faint enhancement in 2 cases with cerebral infarction of about 24h duration and obvious enhancement in all cases in the subacute stage. Compared with enhanced CT, MR using Gd-DTPA demonstrated more obvious enhancement of infarcted areas. MR enhancement using Gd-DTPA showed a gradual increase and the accumulated Gd-DTPA in infarcted areas slowly diffused to the periphery. MR enhancement with Gd-DTPA is similar to that of enhanced CT, but may be more sensitive in the detection of blood brain barrier breakdown.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 7-9 
    ISSN: 1432-1920
    Schlagwort(e): Carotid artery ; Magnetic resonance imaging ; Blood flow
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A Siemens 0.5 Tesla Magnetic Resonance Imaging (MRI) system was used with the saddle head coil and transverse scout localization for imaging 10 normal cervical carotid artery bifurcations in the sagittal plane. Good to excellent visualization of the flow voids and vessel contours was accomplished in all cases. Careful technique and patient cooperation are required.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 127-129 
    ISSN: 1432-1920
    Schlagwort(e): Brain, diseases ; Brain, white and gray matter ; Magnetic resonance imaging ; Computed tomography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Twelve MR scans performed on seven patients with neurosarcoidosis are presented. The most common abnormalities were ventricular enlargement (four patients) and diffuse periventricular white matter changes (three patients). Infarcts were seen in three patients and mass lesion in one. The lesions were seen in both T1 and T2 weighted images. The results are compared with CT findings. MRI seems to be more sensitive than CT in detecting white matter changes and infarcts. Ventricular enlargement and granulomas were equally well seen with both modalities.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 246-251 
    ISSN: 1432-1920
    Schlagwort(e): Temporal bone abnormalities ; Fracture skull base ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In seven patients with temporal bone fractures examined by both CT and MRI, thin section CT proved superior to MRI in demonstrating the full extent of the fractures and the status of the ossicular chain. MR studies were able to demonstrate fractures, when these fractures contained blood or CSF, and the presence of ossicular dislocation in one case where the middle ear was completely filled with CSF or blood. Admixture of air in the middle ear gave a false impression of ossicular dislocation, while air in the fracture obscured portions of it. MR proved superior to CT in the evaluation of intracranial contents by showing 5 additional subdural hematomas, 2 epidural hematomas and 2 hemorrhagic contusions.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 277-282 
    ISSN: 1432-1920
    Schlagwort(e): Paraganglioma ; Catecholamines ; Glomus jugulare ; Sphenopalatine ganglion ; Computed tomography ; Magnetic resonance imaging ; Angiography ; Embolisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Three intracranial catecholamine-secreting paragangliomas are described. They involved a glomus jugulare, a sphenopalatine ganglion and the clivus and upper cervical spine respectively. The extent of the tumours was shown by CT and MRI. They were all highly vascular with a substantial blood supply from systemic arteries which was subjected to particulate embolisation, followed in two cases by surgery. The importance of studying any tumour which could possibly be a paraganglioma for hormonal and, especially, for catecholamine secretion prior to any invasive procedure, including angiography and embolisation, is emphasised: all such procedures should be covered with catecholamine blocking agents and, in addition, carefully monitored with resuscitation facilities immediately available.
    Materialart: Digitale Medien
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  • 15
    ISSN: 1432-1920
    Schlagwort(e): Trans-sphenoidal hypophysectomy ; Cavernous sinography ; Computed tomography ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Imaging studies in 47 patients who were to undergo trans-sphenoidal surgery were analysed with reference to the vascular structures in the parasellar region. The results of cavernous sinography, dynamic contrast enhanced Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) showed good correlation with each other and with the appearances found at operation. CT and MRI, both non-invasive investigations, are therefore reliable preliminary screening methods for identifying the small proportion of patients on whom other imaging techniques need to be performed.
    Materialart: Digitale Medien
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  • 16
    ISSN: 1432-1920
    Schlagwort(e): Multiple scleosis, diagnosis of ; Magnetic resonance imaging ; Vascular brain disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Disseminated lesions in the white matter of the cerebral hemispheres and confluent lesions at the borders of the lateral ventricles as seen on MRI are both considered acceptable paraclinical evidence for the diagnosis of multiple sclerosis. Similar changes are, however, also found in vascular diseases of the brain. We therefore aimed at identifying those additional traits in the infratentorial region, which in our experience are not frequently found in cerebrovascular pathology. We evaluated MR brain scans of 68 patients and found pontine lesions in 71% of cases with a clinically definite diagnosis (17 out of 24) and in 33% of cases with a probable diagnosis (14 out of 43). Lesions in the medulla oblongata were present in 50% and 16%, respectively, and in the midbrain in 25% and 7%, respectively. With rare exceptions all brainstem lesions were contiguous with the cisternal or ventricular cerebrospinal fluid spaces. In keeping with post-mortem reports the morphological spectrum ranged from large confluent patches to solitary, well delineated paramedian lesions or discrete linings of the cerebrospinal fluid border zones and were most clearly depicted from horizontal and sagittal T2 weighted SE-sequences. If there is a predilection for the outer or inner surfaces of the brainstem, such lesions can be considered an additional typical feature of multiple sclerosis and can be more reliably weighted as paraclinical evidence for a definite diagnosis.
    Materialart: Digitale Medien
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  • 17
    ISSN: 1432-1920
    Schlagwort(e): Positron emission tomography ; Magnetic resonance imaging ; Cerebrovascular disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Combined Positron Emission Tomography (PET) and Proton Magnetic Resonance Imaging (MRI) study were performed in six patients with chronic supratentorial stroke to investigate whether remote hypometabolic regions revealed by PET showed any abnormality on MRI. Either regional oxygen consumption (n=4) or glucose utilization (n=2) were measured using PET and the 15O steady state 18FGD technique, respectively. Four patients, with deeply located brain lesions, showed a significant metabolic reduction in the overlying cerebral cortex. In the remaining two patients, affected by a large cortical infarct, there was a significant crossed cerebellar hypometabolism. The MRI weighted by the parameters spin density (ϱ), spin lattice (T1) and spin-spin (T2) relaxation times were obtained employing various sequences in the same subjects. In no patient did the MRI show any contrast modification in these hypometabolic remote regions, suggesting that subtle loss of tissue and/or biochemical change do not underlie the reduction in metabolic rate.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 403-405 
    ISSN: 1432-1920
    Schlagwort(e): Magnetic resonance imaging ; Pelizaeus ; Merzbacher disease ; Cerebral sclerosis diffuse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Pelizaeus-Merzbacher's disease is a progressive encephalopathy with demyelination of the cerebral white matter. The diagnosis can not be made on clinical or biological grounds: pathological investigation is necessary to confirm tigroid demyelination. CT scanning failed to visualize this type of anomaly but detection is now possible with the advent of magnetic resonance imaging (MRI). The authors studied the case of a boy who, at the age of 8 presented with symptoms characteristic of the disease: rotatory nystagmus, progressive encephalopathy, and inherited X-linked recessive traits. Magnetic resonance imaging revealed a high signal in the supra-tentorial white matter and the usual contrast was inverted. The authors believe that MRI can make an important contribution to the diagnosis of the disease.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 69-75 
    ISSN: 1432-198X
    Schlagwort(e): Blood pressure ; Essential hypertension ; Genetics ; Epidemiology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This paper presents a review of the genetic transmission of normal blood pressure and of essential hypertension. Familial aggregation of normal blood pressure has been reported in adults, in children and even in newborns. Blood pressure aggregation phenomenon, however, is the result of both a genetic component and shared environmental factors. More specific for each etiological factor were the studies of blood pressure aggregation in twins and in adopted children. Attention was focused on the Montreal Adoption Study. In essential hypertension, a Japanese study is reviewed showing the occurrence of hypertension in the offspring of hypertensive parents. The heterogeneity of essential hypertension is underlined and two of the multiple etiological factors are particularly considered for their genetic component: the response to salt intake and erythrocyte cation fluxes. The conclusion from the literature reviewed is that essential hypertension is a polygenic disease transmitted by polygenic systems.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 136-139 
    ISSN: 1432-198X
    Schlagwort(e): IgA nephropathy ; Genetics ; Complement ; C4 ; Glomerulonephritis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract C4 and factor B typing were performed in 37 pediatric patients with primary IgA nephropathy. Null alleles for C4B occurred with a frequency of 26% in patients, as compared to 15% in healthy controls (NS). The phenotype of C4B deficiency (homozygous C4B null), however, was found in 16% of patients and 4% of controls (P〈0.05). Comparison of observed C4B phenotypes with those predicted from the Hardy-Weinberg equilibrium also confirmed an excess of C4B deficiency (P〈0.0005). In contrast, there was no evidence of distortion in the frequencies of the C4A null allele or phenotype, or of the factor B alleles. The data suggest that C4B deficiency may be one of multiple interacting factors contributing to the development of this glomerulopathy.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 397-404 
    ISSN: 1432-198X
    Schlagwort(e): Cystic kidneys ; Genetics ; Prenatal diagnosis ; Linkage studies ; Potter sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Despite the high incidence of cystic kidney diseases, affected families are not usually well informed of the inheritance of these disorders. Genetic counselling must be based on precise diagnostic criteria. Detailed information on the different types of cystic kidney disease is summarized, including clinical features, pathology, radiology, prenatal diagnosis and the risk of recurrence. In addition, a genetic interpretation is given of the Caroli syndrome, Potter sequence as well as congenital hepatic fibrosis.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Pediatric nephrology 1 (1987), S. 436-438 
    ISSN: 1432-198X
    Schlagwort(e): Alport's syndrome ; Genetics ; Heterogeneity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The pattern of inheritance in Alport's syndrome has been controversial for some time. Recent studies have clarified the mode of inheritance in this disease. Alport's syndrome is a heterogeneous disorder made up of a number of genetically distinct syndromes, with an autosomal dominant, an X-linked dominant and a rare autosomal recessive form. Clinical analysis shows that there are many distinct forms with or without nerve deafness, and with early or late occurrence of end-stage renal disease.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Skeletal radiology 16 (1987), S. 635-643 
    ISSN: 1432-2161
    Schlagwort(e): Giant cell tumor ; Bone neoplasms ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In six cases of giant cell tumor the magnetic resonance (MR) images obtained with various pulse sequences and field strengths were compared to the corresponding computed tomography (CT) scans and plain roentgenograms. MRI was superior to CT and plain films in demonstrating areas of tissue inhomogeneity within the tumor as well as soft tissue extension. CT was superior in demonstrating cortical thinning. Multiplanar imaging capability and visualization of articular cartilage may demonstrate intra-articular tumor spread. The characteristic MRI findings with short TR/TE (T1-weighting) and long TR/TE (T2-weighting) are described. We also describe one case where serial MR scans were used to assess response to therapy.
    Materialart: Digitale Medien
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  • 24
    ISSN: 1432-2161
    Schlagwort(e): Magnetic resonance imaging ; Bone neoplasms ; Chondroblastoma ; Clear cell chondrosarcoma ; Iliopsoas bursa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Three cases of lytic, calcified epiphyseal lesions with plain film and computed tomography features suggestive of chondroblastoma were imaged by magnetic resonance imaging. Histopathologic correlation was obtained in each case. Two cases of chondroblastoma showed low signal intensity on both short (TR600/TE20ms) and long (TR2500/TE80ms) spin echo (SE) images. The third case, a clear cell chondrosarcoma, demonstrated increased signal intensity on moderately T2 weighted (TR2500/TE40ms) images. These findings suggest that magnetic resonance imaging may be helpful in distinguishing these lesions.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Skeletal radiology 16 (1987), S. 23-29 
    ISSN: 1432-2161
    Schlagwort(e): Osteosarcoma ; Magnetic resonance imaging ; Pulsing sequences ; Appearances and clinical value
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Early magnetic resonance (MR) experience in the evaluation of 14 consecutive long bone intramedullary osteosarcomas demonstrates the need for T1 and T2 weighted pulsing sequences in the staging of this disease. Intramedullary disease is best depicted by coronal T1 weighted pulsing sequences and subtle extra-compartmental discase by T2 weighted axial imaging. Both high intensity and low intensity intra-medullary signals were noted on T2 weighting, while all T1 weighted pulsing sequences showed intra-medullary disease to have low signal intensity. Extraosseous tumor on T2 weighting usually had a high signal, and disease extent was therefore sharply demarcated from uninvolved muscle and its relationship to vessels confidently assessed. MR appears optimally suited for local staging of osteosarcoma, further enhancing the role of radiology in planning limbsalvage surgical techniques.
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  • 26
    ISSN: 1432-2161
    Schlagwort(e): Magnetic resonance imaging ; Soft tissues, magnetic resonance studies ; Muscles, neoplasms ; Juvenile fibromatosis, magnetic resonance studies ; Sedation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We report the time-dependent magnetic resonance imaging (MRI) changes that resulted from an intramuscular injection of a commonly-used pediatric sedation regimen (“DPT”). These changes at the site of injection consist of a focal abnormality characterized by a slight increase in signal intensity on T1 weighted images and markedly increased signal intensity on T2 weighted images. Alterations in signal are detectable almost immediately after the injection and progress over the first 31 hours. This abnormality, which could be mistaken for real disease, persists up to 36 days following injection.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 146 (1987), S. 283-287 
    ISSN: 1432-1076
    Schlagwort(e): Pena-Shokeir I syndrome ; Facial anomalies ; Ankylosis ; Pulmonary hypoplasia ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Two siblings whose clinical and pathologic features were consistent with the “Syndrome of camptodactyly, multiple ankyloses and pulmonary hypoplasia” originally described by Pena and Shokeir were examined at autopsy. Additional features were intrauterine growth retardation, immaturity of the central nervous system (CNS) and atrophy of skeletal muscles. Our data suggest that CNS damage may cause the complicated phenotypic abnormalities of the syndrome.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 146 (1987), S. 205-208 
    ISSN: 1432-1076
    Schlagwort(e): Lissencephaly ; Agyria ; Pachygyria ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In a patient with clinical manifestations suggestive of brain malformation, computer-assisted tomography (CT) showed lissencephaly: agyria, pachygyria, absent opercularization, and colpocephaly. The patient did not have seizures or a typical EEG of hypsarrhythmia. By magnetic resonance imaging (MRI), using a long inversion-recovery sequence, it was possible to verify the CT-findings and to demonstrate heterotopic grey matter and missing claustrum. By MRI it was much easier to estimate the altered ratio of grey and white matter. High grey-white matter contrast of inversion-recovery scans and the possibility of imaging the brain in sagittal, coronal and transverse planes make MRI the method of choice for the evaluation of lissencephaly and other brain malformations. In this case it helped to verify lissencephaly as one aspect of an unknown clinical entity of type-I-lissencephaly, defective structure of lymphatic nodes, a polyarthritis-like clinical picture, hypodontia, and flaring of the ribs.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 146 (1987), S. 550-554 
    ISSN: 1432-1076
    Schlagwort(e): Epilepsy ; Genetics ; Myoclonic-astatic seizures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This paper presents case reports of patients suffering from myoclonic-astatic and stimulus-sensitive myoclonic seizures, respectively. It gives details of clinical and EEG data in the pertinent families. This is discussed in the context of controversial nosographic concepts of epilepsies with myoclonic seizures, and of the results of extensive family investigations. The findings demonstrate the decisive importance of hereditary factors in the pathogenesis of myoclonic and myoclonic-astatic epilepsy, the genetic background of which is probably polygenic.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 146 (1987), S. 49-50 
    ISSN: 1432-1076
    Schlagwort(e): Intra-abdominal testis ; Localization ; Orchiopexy ; Laparoscopy ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A survey was made of 30 pediatric urologists for their current practice. Localization, important for operative approach, is done by venography and arteriography; ultrasonography, computed tomography and magnetic resonance imaging; and laparoscopy, the last most often immediately before operation. The preferred operation is the long-loop was orchiopexy; two-stage orchiopexy and microsurgical autotransplantation are alternatives.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 234 (1987), S. 172-176 
    ISSN: 1432-1459
    Schlagwort(e): Spinal epidural lipomatosis ; Hypothyroidism ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Epidural lipomatosis usually occurs as a complication of steroid therapy. This report includes the first description of a case secondary to hypothyroidism. Adults in all age groups can be affected and present with progressive signs and symptoms of spinal cord or cauda equina compression. The dorsal aspect of the thoracic spine is most commonly involved, usually in its total extent. Spine radiographs are normal and myelography poorly delineates the nature and extent of abnormality. While computed tomography can provide information about the nature of the spinal mass, magnetic resonance imaging is the investigation of choice. Extensive decompressive laminectomy is useful but the results are variable. Correction of underlying endocrine abnormality can reverse the process. The need for early diagnosis of this disorder is therefore emphasized.
    Materialart: Digitale Medien
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  • 32
    ISSN: 1432-1459
    Schlagwort(e): Progressive multifocal leucoencephalopathy ; Magnetic resonance imaging ; Interferon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Progressive multifocal leucoencephalopathy was diagnosed by magnetic resonance imaging (MRI) and brain biopsy in a 44-year-old woman, for whom therapeutic trials with various antiviral agents were made. Despite early diagnosis and treatment, her neurological deterioration and extension of MRI-detectable lesions were not halted for a period of about 8 months. After the introduction of intrathecal β-interferon therapy, her neurological status and MRI findings became stable and showed minimal improvement. Early diagnosis of this fatal disorder is important and intrathecal interferon therapy should be considered.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 149 (1987), S. 36-42 
    ISSN: 1432-072X
    Schlagwort(e): Catabolite repression ; Genetics ; Malate dehydrogenase ; Molecular cloning ; Sequence ; CRP binding site ; Escherichia coli
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The malate dehydrogenase gene of Escherichia coli, which is susceptible to catabolite and anaerobic repression, has been cloned using plasmic pLC32-38 of Clarke and Carbon (1976). The nucleotide sequence was determined of a 2.47 kbp fragment, containing the mdh structural gene. All information necessary for expression of the mdh structural gene was mapped within a 1.3 kbp SphI-BstEII fragment. Compared with the untransformed wild type, transformations with pUC19 vector, containing this fragment, gave up to 40-fold more malate dehydrogenase activity in both E. coli wild type and mdh mutant recipients. Catabolite repression was not affected in the transformants. A possible CRP binding site in the promotor region of the mdh gene provides evidence for a co-regulation with fumA gene, the structural gene of fumarase, which is also subject to catabolite repression. The structures for transcription initiation and termination were similar to those previously described for E. coli. Amino acid sequence homologies between pro- and eucaryotic malate dehydrogenases are discussed.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Child's nervous system 3 (1987), S. 225-227 
    ISSN: 1433-0350
    Schlagwort(e): Rathke's cleft cyst ; Suprasellar cyst ; Pituitary cyst ; Computed tomography ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Two cases of Rathke's cleft cyst are presented. The cysts showed as high-density lesions on plain CT with slight enhancement with contrast medium. They appeared as a hyperintense mass in the T1-weighted magnetic resonance images. Preoperative diagnosis is very important because different sellar cystic lesions require different treatment.
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  • 35
    ISSN: 1432-2161
    Schlagwort(e): Wrist ; Magnetic resonance imaging ; Surface coil ; Normal anatomy ; Cadaveric correlation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Magnetic resonance imaging (MRI) provided adequate depiction of carpal soft tissue structures in normal volunteers, as well as accurate anatomic correlation with cadaveric specimens. Using a high field strength system and surface coil techniques, the intricate anatomy of the wrist was best defined on long TR short TE images. However, from a practical view, T1 weighted images (TR 600 ms, TE 25 ms) were most useful because of short imaging times, satisfactory image quality, and the absence of motion artifacts. The coronal plane provided the clearest definition of important structures. Potential diagnostic limitations exist due to the inability of MRI ot clearly delineate articular cartilage, joint capsules, and small interosseous ligmaents. The presence of intra-articular fluid in both living subjects and cadaveric specimens, however, allowed for fine depiction of these structures on T2 weighted images.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 234 (1987), S. 344-347 
    ISSN: 1432-1459
    Schlagwort(e): CNS vasculitis ; Small vessel ; Recurrent cerebral bleeding ; Magnetic resonance imaging ; Immunosuppressive therapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A patient with CNS vasculitis limited to small vessels is described. Initial spinal cord involvement with paraparesis was followed by multifocal cerebral and cerebellar involvement, depicted by magnetic resonance imaging (MRI). She also had recurrent cerebral bleeding. A diagnosis of vasculitis was made by cerebral biopsy. Immunosuppressive therapy resulted in clinical improvement and resolution of the MRI abnormalities.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 234 (1987), S. 401-407 
    ISSN: 1432-1459
    Schlagwort(e): Multiple sclerosis ; Tetraparesis ; Paraparesis ; Spinal tumour ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The clinical, neuroradiological, electrophysiological and CSF findings of seven patients with slowly progressive paraparesis or tetraparesis are presented. In all patients, the results of the tests performed, including evoked potentials, CT scanning, oligoclonal bands in the CSF and myelography, were normal or inconclusive and did not lead to the correct diagnosis of the aetiology. In contrast, magnetic resonance imaging (MRI) provided the diagnosis of the causative process: multiple sclerosis in four cases, meningioma of the craniocervical junction or upper thoracic spinal cord in two cases, and upper cervical cord low-grade astrocytoma in one case. The patients with tumour could be treated effectively. Without MRI, however, the correct diagnosis would have been delayed. T2-weighted spin-echo scans provided maximal sensitivity for the detection of MS plaques, although they lacked specificity for a special disease. Several morphological criteria during MRI were helpful in differentiating Binswanger's disease, leucodystrophy and adrenoleucodystrophy from MS. It is concluded that at present MRI is the only non-invasive test with which to screen reliably the craniocervical junction and the upper cervical level, both of which are diagnostically difficult regions. The case histories also demonstrate that MRI is essential in all patients where a full clinical evaluation of the suspected spinal segment is not possible. “Pure spinal MS” is a misleading diagnosis and should not be accepted without confirmation by MRI. MRI has to be performed early enough to permit timely treatment of spinal and brain-stem disorders.
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  • 38
    ISSN: 1432-1459
    Schlagwort(e): Syringomyelia ; Syringomyelic syndrome ; Metrizamide CT myelography ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The clinical features of 31 cases of syringomyelic syndrome, confirmed by metrizamide CT myelography (CTM) or magnetic resonance imaging (MRI), were analysed. Bilateral suspended sensory disturbance, previously regarded as a characteristic feature, was encountered in only 2 cases (6.5%). Thirteen patients (41.9%) showed no motor deficits of the upper limbs and 7 patients (22.6%) did not have weakness or atrophy in any of the four extremities. Cervical segmental signs were absent in 7 cases (22.6%) and in 2 (6.5%) signs were only present in the lower limbs. Scoliosis and foot deformity, such as pes cavus or equinovarus, were seen in 17 (54.8%) and 5 cases (16.1%) respectively. These skeletal abnormalities were initial symptoms in some childhood cases. In syringomyelic syndrome, clinical features are variable with many atypical clinical manifestations, apart from the previously recognized characteristic clinical features.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 235 (1987), S. 95-98 
    ISSN: 1432-1459
    Schlagwort(e): Haemangioblastoma ; Magnetic resonance imaging ; Gadolinium-DTPA ; Angio-MRI
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Magnetic resonance imaging (MRI) patterns of 11 haemangioblastomas examined with a 1.5-T scanner are described. MRI was as effective as contrast-enhanced CT in the detection of vascular tumour components, but was less sensitive than angiography. MRI was superior to CT in delineating the exact extent of the lesions, for example contact with the arachnoid surface. Even if a cystic tumour component is absent, MRI can provide helpful criteria for differential diagnosis; in particular, T2 values allow differentiation from meningiomas. In three patients additionally administered gadolinium (Gd) diethylenetriaminepenta-acetic acid (DTPA) the angiomatous parts of the tumour showed a remarkable decrease in T1 value, but the time dependence of the enhancement was not the same as that seen in dynamic CT.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 73 (1987), S. 440-444 
    ISSN: 1432-2242
    Schlagwort(e): Secale cereale L. ; Genetics ; α-Amylase ; Isozymes ; Modifiers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Fifteen inbred lines of rye, F1 and F2 progenies from crosses between lines were studied using polyacrylamide gel electrophoresis. Conventional genetic analysis of α-amylase zymograms showed that the 19 bands detected in the endosperm of germinating caryopses were controlled by three linked structural loci and one independent modifying locus, which influenced the electrophoretic mobility of isozymes. Two codominant alleles were found at the α-Amy1, α-Amy2 structural loci and the M-α-Amy modifying locus while the α-Amy3 locus had three alleles. Double-banded expression of the α-amylase alleles was probably due to the simultaneous presence of modified and unmodified forms of isozymes on the zymogram.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 74 (1987), S. 177-187 
    ISSN: 1432-2242
    Schlagwort(e): Barley ; Grain development ; Mutants ; Ultrastructure ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Eleven Na-azide induced barley shrunken endosperm mutants expressing xenia (sex) were characterized genetically and histologically. All mutants have reduced kernel size with kernel weights ranging from 11 to 57% of the wild type. With one exception, the mutant phenotypes are ascribable to single recessive mutant alleles, giving rise to a ratio of 3∶1 of normal and shrunken kernels on heterozygous plants. One mutant (B10), also monofactorially inherited, shows a gene dosage dependent pattern of expression in the endosperm. Among the 8 mutants tested for allelism, no allelic mutant genes were discovered. By means of translocation mapping, the mutant gene of B10 was localized to the short arm of chromosome 7, and that of B9 to the short arm of chromosome 1. Based on microscopy studies, the mutant kernel phenotypes fall into three classes, viz. mutants with both endosperm and embryo affected and with a non-viable embryo, mutants with both endosperm and embryo affected and with a viable embryo giving rise to plants with a clearly mutant phenotype, and finally mutants with only the endosperm affected and with a normal embryo giving rise to plants with normal phenotype. The mutant collection covers mutations in genes participating in all of the developmental phases of the endosperm, i.e. the passage from syncytial to the cellular endosperm, total lack of aleurone cell formation and disturbance in the pattern of aleurone cell formation. In the starchy endosperm, varying degrees of cell differentiation occur, ranging from slight deviations from wild type to complete loss of starchy endosperm traits. In the embryo, blocks in the major developmental phases are represented in the mutant collection, including arrest at the proembryo stage, continued cell divisions but no differentiation, and embryos deviating only slightly from the wild type.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 74 (1987), S. 439-444 
    ISSN: 1432-2242
    Schlagwort(e): Wheat ; Callus ; Regeneration ; Tissue culture ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Calli were initiated from immature embryos of nine lines of hexaploid wheat (Triticum aestivum L. em. Thell). These were the euploid lines Chinese Spring and Cappelle-Desprez, a line of Chinese Spring ditelocentric for the long arm of 4B, four substitution lines of Chinese Spring in which chromosome 4B has been replaced by its homologues from different wheat varieties and substituted into Chinese Spring and a substitution line of Besostaya I 4B into Cappelle-Desprez. The calli from these lines were found to differ in their growth rates and morphogenic and regenerative activities. The substitution of different 4B chromosomes into Chinese Spring significantly increased morphogenesis and shoot regeneration from callus. The potential for developing wheat lines with improved culture characteristics is discussed.
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  • 43
    ISSN: 1617-4623
    Schlagwort(e): E. coli ; Genetics ; Polysaccharide biosynthesis ; Secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Transposon and deletion analysis of the cloned K1 capsule biosynthesis genes of Escherichia coli revealed that approximately 17 kb of DNA, split into three functional regions, is required for capsule production. One block (region 1) is required for translocation of polysaccharide to the cell surface and mutations in this region result in the intracellular appearance of polymer indistinguishable on immunoelectrophoresis to that found on the surface of K1 encapsulated bacteria. This material was released from the cell by osmotic shock indicating that the polysaccharide was probably present in the periplasmic space. Insertions in a second block (region 2) completely abolished polymer production and this second region is believed to encode the enzymes for the biosynthesis and polymerisation of the K1 antigen. Addition of exogenous N-acetylneuraminic acid to one insertion mutant in this region restored its ability to express surface polymer as judged by K1 phage sensitivity. This insertion probably defines genes involved in biosynthesis of N-acetylneuraminic acid. Insertions in a third block (region 3) result in the intracellular appearance of polysaccharide with a very low electrophoretic mobility. The presence of the cloned K1 capsule biosynthesis genes on a multicopy plasmid in an E. coli K-12 strain did not increase the yields of capsular polysaccharide produced compared to the K1+ isolate from which the genes were cloned.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 208 (1987), S. 279-287 
    ISSN: 1617-4623
    Schlagwort(e): NAD metabolism ; Regulation ; nadR ; Salmonella typhimurium ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nadR locus (99 min) controls the transcription of several genes involved with either the biosynthesis (nadAB) or recycling (pncB) of NAD in Salmonella typhimurium. Point mutations in this locus were found to cause defects either in the transport of nicotinamide mononucleotide (PnuA-), the regulation of nadAB (NadR-) or both transport and regulation (PnuA-NadR-). Deletions or insertions into nadR always resulted in the PnuA- NadR- phenotypes. Merodiploids constructed with various combiminations of PnuA-, NadR- or PnuA-NadR- strains indicate a single complementation group. The results suggest the NadR product is a bifunctional regulatory protein. Operon fusions to lacZ (nadR:: Mud1-8) were used to show that nadR is not autoregulated and is transcribed in a clockwise direction. The gene was also cloned and located within a 2 kb EcoR1-BglII fragment.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    International journal of anthropology 2 (1987), S. 141-149 
    ISSN: 1824-3096
    Schlagwort(e): Absolute finger ridge count ; Genetics ; Dermatoglyphics ; India ; Major gene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In order to test the hypothesis of a major gene effect on absolute total finger ridge count (ATFRC), the nature of relationship between mean ATFRC and its variability was evaluated in a series of 47 population samples from India. Regression analysis showed that both the standard deviation and the coefficient of variation are significantly related to mean ATFRC, and about 35% of the variation in ATFRC is explained by the dependent variable coefficent of variation. These results support the hypothesis of a major gene effect on the trait ATFRC.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 18 (1987), S. 249-256 
    ISSN: 1573-5133
    Schlagwort(e): Developmental rate ; Genetics ; Inheritance ; Meristic ; Salmonidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Deviations from morphological intermediacy in six first generation hybrids between three hatchery strains of rainbow trout, raised in a common environment, are reported. Hybrids have higher mean counts of four meristic characters than their maternal parental strain in a significantly greater number of cases (18 out of 24). Furthermore, eight of eleven hybrid indices are not intermediate. These results are discussed in reference to several mechanisms and models proposed to account for observed responses of meristic characters to environmental and genetic influences.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Langenbeck's archives of surgery 372 (1987), S. 952-952 
    ISSN: 1435-2451
    Schlagwort(e): Magnetic resonance imaging ; Aortic aneurysms ; Dissections ; Kernspintomographie ; Aortenaneurysmen ; Dissektionen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Um die diagnostische Wertigkeit der Kernspintomographie (KST) im Bereich der Aortenchirurgie zu überprüfen, wurden 47 Untersuchungen (22 prä-, 25 postoperativ) bei 28 Patienten mit aortalen Aneurysmen und Dissektionen durchgeführt. Präoperativ konnte die Grösse des Aneurysmas, intramuraler Thrombus, perivasculäre Strukturen, assoziierte Prozesse grösserer Gefässabgänge dargestellt werden. Nachweis einer Dissektion und Differenzierung von wahren und falschen Lumen war immer möglich. Postoperativ wurde das Operationsergebnis dokumentiert und die KST als Verlaufskontrolle eingesetzt. Aufgrund der hohen räumlichen Auflösung in jeder gewünschten Schnittebene, der Nichtinvasivität, der Vermeidung von Röntgenstrahlen und Kontrastmittel stellt die KST eine wertvolle Erweiterung des diagnostischen Instrumentariums für den Bereich aortaler Erkrankungen dar.
    Notizen: Summary For diagnostic evaluation of magnetic resonance imaging (MRI) of aortic disease, 47 examinations (22 pre-, 25 postoperatively) were performed in 28 patients with aortic aneurysms and dissections. Preoperatively, the extent of the aneurysm, intramural thrombus, perivascular structures, and associated process of major side branches could be documented. Diagnosis of dissection and differentiation of true and false lumen were always possible. Postoperatively, the operative result could be imaged and MRI was used for follow-up. As there is a high spatial solution in every section desired, non-invasiveness, and no X-rays or contrast material, MRI is a valuable enrichment to the diagnostic armamentarium of aortic pathology.
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    European archives of oto-rhino-laryngology and head & neck 243 (1987), S. 424-428 
    ISSN: 1434-4726
    Schlagwort(e): Chondroma ; Skull base ; Nasopharynx ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We report a case of an extracranial chondroma of the skull base. This tumor occupied mainly the skull base, the nasopharynx and the parapharyngeal space. Magnetic resonance imaging was effective in diagnosis and determining the extent of the lesion. Total extirpation of the lesion was performed via an external cervical approach. A survey of the available literature revealed only three similar cases treated to date.
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  • 49
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 1-1 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 33-44 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The theory of MCSCF and CI energy derivatives with respect to geometrical variations is briefly reviewed with special attention given to the MCSCF and MRCI energy gradients. A computational procedure is proposed for MRCI energy gradients that does not require the solution to any “coupled-perturbed MCSCF” equations, it does not require any expensive direct-CI matrix-vector products involving derivative integrals, and it does not require any derivative integrals to be transformed from the AO basis to the MO basis. An additional feature is that it does not require any changes to existing MCSCF gradient evaluation programs in order to compute MRCI gradients. The only difference in the two cases is the exact nature of the data passed to the gradient evaluation program from the previous steps in the computational procedure. The additional effort required to compute the entire MRCI energy gradient vector is approximately that required for one additional iteration of the MRCI diagonalization procedure and for one additional MCSCF iteration. For large scale MRCI wave functions, the MRCI energy gradient evaluation should only require about 10% of the effort of computing the wave function itself. This computational procedure removes a major computational botleneck of potential energy surface evaluation.
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  • 51
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 65-71 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preliminary results are presented for transition probabilities in the H + H2 system derived from an adiabatic representation in terms of surface functions on hyperspheres. Special attention is given to the resonance structure for transition probabilities in the first vibrational level.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 99-112 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Low-lying excitation energies from the ground state of Be were calculated using a basis set of 61 Cartesian Gaussian functions. Three approximations were employed: the time-dependent Hartree-Fock (TDHF), second-order equations-of-motion (EOM), and multiconfigurational time-dependent Hartree-Fock (MCTDHF). The TDHF excitation energies are 0.5-1.1 eV lower than experiment, and the EOM values are 0.3-1.2 eV lower than experiment, whereas the MCTDHF excitation energies deviate on the absolute average from experiment by only 0.03 eV. We found that in an MCTDHF calculation, any proper MCSCF stationary point is a good reference (i.e., initial) state, not just the ground state. Experimental values for oscillator strength are accurately known only for the 2s2X1S → 2s2p1P0 transition. The TDHF value and the MCTDHF value agree with experiment, but the EOM value does not. The agreement of the TDHF value with experiment seems to be coincidental, because for higher lying transitions the TDHF values differ by approximately a factor of two or more from the more accurate MCTDHF. Frequency independent polarizabilities, α(0), were also calculated with the TDHF, HRPA, and MCTDHF and frequency dependent polarizabilities, β(ω), were calculated with the MCTDHF. No experimental data for Be polarizabilities exist, but we expect the MCTDHF values to be among the most accurate calculations available.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 53
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 941-950 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A version of the CNDO/1 method has been outlined that includes dominant relativistic effects. The method utilizes a nonempirical parametrization based on atomic Dirac-Fock calculations. The goal of this QR-CNDO/1 method lies in its applicability to molecules consisting of arbitrary atoms (z = 1-118). Applications to molecular geometries and ionization potentials for 50 molecules are presented.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987) 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 13-18 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: According to the formulas obtained in the preceding paper, it may be used for all types of the hybridization with any set of azimuthal quantum numbers l, l = 0 through l = 5, and a complete theoretical data of bond angles and bond strengths are shown in this paper.
    Zusätzliches Material: 2 Tab.
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  • 56
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 71-86 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the unitary-group formulation of quantum chemistry, the spin-projected, configuration-state spaces of quantum chemistry are realized by the irreducible representation spaces (IRS) of the freeon unitary group U(n), where n is the number of freeon orbitals. The Pauli-allowed IRS are labeled by the partitions [λ] = [2(N/2)-s, 12S], where N and S are the particle number and the spin, respectively. The generator-state approach (GSA) to the unitary-group formulation consists of (1) the construction of the overcomplete, nonorthonormal generator basis for each IRS; (2) the Lie-algebraic computation of matrix elements over generator states; (3) the Moshinsky-Nagel construction of the complete, orthonormal Gel'fand basis in terms of the generator basis; and (4) the computation of matrix elements over Gel'fand states in terms of matrix elements over generator states.
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  • 57
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987) 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 181-191 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It has been shown that an easier procedure to the study of molecular electrostatic potentials than the prevalent monopole isopotential approach is to use a dipole as the mapping device: allow the dipole to move on a geometrical surface enclosing the molecule such that the distance between the surface and the nearest atoms of the molecule (closest distance of approach) is fixed, say at 2 Å, calculate the electrostatic interaction energy between the molecule and the dipole at different points of the surface, and let the dipole orient itself along the minimum energy direction and treat these minimum energies as the desired electrostatic potentials. Thus the favorable binding sites of a given molecule for other species along with their relative orientations can be obtained. This procedure has been applied to the nucleic acid bases using the necessary input data from two independent sources. Thus success of the procedure in predicting important features of molecular electrostatic potentials has been demonstrated.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 59
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A systematic examination of the components of the interaction energy, obtained with the Kitaura and Morokuma method, for nine H-bonded dimers without and with counterpoise corrections (CP) is presented. The nine dimers Hn A … HBHm correspond to all the possible combinations of HF, H2O, and NH3 as electron donors and electron acceptors. The interaction energy and the corresponding components have been computed over a sizable interval of intermolecular distances with five basis sets (STO-3G, MINI-1, 3-21G, 4-31G, 6-31G**) selected among those most extensively used to study interactions in larger systems. The CP corrections to the ΔE components have been obtained with a method, implemented in our group, which permits assignment to the pertinent components of ΔE of a physically reasonable portion of the CP correction even though different CP corrections are adopted. We examine here three versions of the CP correction, namely, the full CP correction (i.e., the original version of Boys and Bernardi) and CP corrections limited to the virtual space of the partner or to the electron donor only. The resulting data are employed to assess the basis set dependence of several models of hydrogen bonding (the electrostatic model, the semiclassical model, etc.) both with and without CP corrections.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 60
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A detailed analysis of the ΔE(R) curves for nine hydrogen bonded dimers involving HF, H2O, and NH3 as partners, computed with five basis sets (STO-3G, MINI-1, 3-21G, 4-31G, and 6-31G**) and subjected to counterpoise (CP) corrections with three different methods is reported. Using several criteria and tests, the positive effect of full CP corrections for the description obtained with all the basis sets (with the exception of the STO-3G one) is pointed out. The CP correction at the 6-31G** levels is still sizable and improves the results with respect to the estimated Hartree-Fock limits of ΔE(Req) and Req. The results obtained with the application of the full CP correction to the MINI-I energies are of relatively good quality. The STO-3G energies at the SCF level are, on the contrary, overcorrected by the full CP correction and slightly improved by “limited” CP corrections: this basis set, however, is not recommended for calculations of geometries and stabilization energies of H-bonded dimers of this size.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 295-312 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An accurate analytical electron density for the beryllium atom is obtained by using a fast and systematic method recently developed and tested for the neon atom. Asymptotic conditions both at the nucleus and at large distances are obeyed. A point-by-point comparison between our density and the one obtained from an almost “exact” configuration interaction wave function shows that differences are less than 0.5% for r between 0 and 5 bohrs and less than 1 % up to 9 bohrs. The accuracy of the density is also assessed by comparing results of density moments and x-ray scattering factors.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 361-375 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We discuss a procedure for calculating numerical Hartree-Fock orbitals that can be applied to polyatomic systems. This approach is formulated in momentum space to avoid Coulomb singularities and uses fast Fourier transforms to solve integral convolutions. Results for a number of simple systems are presented.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 405-415 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Binding of Zn2+ to imidazole (Im) and methyl imidazole (MeIm) is studied by ab initio methods as a model for the effect of cation binding on tautomeric energies. Gradient energy optimized conformations were obtained for all neutral and ionic structures, including the deprotonated molecules and the ylides. The N3—H tautomer of MeIm is calculated to be more stable than N1—H by about 1 kcal/mole. However, binding of a Zn2+ cation to the available nitrogen site is found to reverse the order of binding, leaving N1—H more stable by 1 kcal/mole. Binding of Zn2+ produces a significant perturbation in the electronic structure, a smaller shift in the equilibrium conformation of the imidazole ring, and only a small absolute shift in the relative tautomer energies. Methyl substitution at C5 has a small effect on both conformation and energetics.A high-energy ylide tautomer is produced by moving the proton bound to C2 to the N1 atom. The binding of Zn2+ to the C2 site is substantially stronger than to the N1 site, yielding nearly isoenergetic ZnIm2+ conformations for binding to either N or C atoms. For the deprotonated salts the lowest energy conformation has the C2—N3 bond bridged by Zn2+.
    Zusätzliches Material: 7 Tab.
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  • 64
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 425-427 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It is made clear that two different statements in the literature concerning energy derivatives are completely compatible by deriving them as two different interpretations of the same equation. Some other aspects of these results are also discussed.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 435-443 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Accurate methods for computing energies and electronic properties of atoms and molecules have been derived from direct treatment of localized pairs of electrons. The conceptual development and implementation of such methods is reviewed.
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  • 66
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 473-489 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rigorous derivation of the energy density functional is proposed within the framework of the spinfree, or spin-restricted formulation of the energy density functional theory. It is shown particularly that the kinetic energy density functional is given by a sum of the Weizsacker term and the so-called “modified” Thomas-Fermi one. The variational principle is formulated for the energy density functional theory in terms of the Euler-Lagrange equation, and the virial theorem is proposed.
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  • 67
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 591-594 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The time-dependent Schrouml;dinger equation for the oscillator H = α(t)p2 + β(t)x2 + γ(t)x is exactly solved. The time evolution operator is easily obtained by means of an operator algebra and the quantum-mechanical equations of motion. The problem is reduced to solving the classical equations of motion. The method is shown to apply to multidimensional oscillators.
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 445-453 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A modified Bohr orbit procedure is used to calculate the energies for the 1S ground state and the 2P, 3D, and 4F excited states of the helium atom. The energies are calculated from \documentclass{article}\pagestyle{empty}\begin{document}$ {{\int\limits_0^\pi {E\left(\Phi \right)P\left(\Phi \right)d\Phi } } \mathord{\left/ {\vphantom {{\int\limits_0^\pi {E\left(\Phi \right)P\left(\Phi \right)d\Phi }} {\int\limits_0^\pi {P\left(\Phi \right)d\Phi } }}} \right. \kern-\nulldelimiterspace} {\int\limits_0^\pi {P\left(\Phi \right)d\Phi } }} $\end{document}, in which E(φ) is the Bohr orbit energy for angle φ between the position vectors \documentclass{article}\pagestyle{empty}\begin{document}$ \vec r_1 $\end{document} r1 and \documentclass{article}\pagestyle{empty}\begin{document}$ \vec r_2 $\end{document} r2, and P(φ) is a probability function for this angle. Numerical procedures are used to evaluate the integrals. Energies that range between -2.9082 and -2.9054 au are calculated for the 1S state (cf. -2.9037 au, exact). The Bohr energies for the excited states are -2.1318, -2.1240, -2.0562, -2.0555, -2.0314, and -2.0312 au, which are generally close to the exact energies of -2.1332, -2.1239, -2.0557, -2.0557, -2.0313, and -2.0313 au for the 23P, 21P, 33D, 31D, 43F and 41F states. Some relationships that exist between the Bohr theory and the Schrödinger local energies are discussed. Approximate Bohr orbit estimates for the energies of the 2P states of He, Li+,…,Ne8+ are reported.The invariance of the two-electron Bohr hamiltonian with respect to the interchange of the electron coordinates leads to two classical probability functions when the orbit quantum numbers for the two electrons differ.
    Zusätzliches Material: 4 Tab.
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 463-470 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Valence-bond calculations are reported for the isoelectronic series of molecules and ions: N2, CO, BF, NO+ and CN-. The most important structures are N≡N, C=O, Bπ—F, N+=O and C=N. Hybridization of the 2s and 2p orbitals is important. Only two or three structures are required to obtain an energy lower than that obtained with the molecular orbital approximation. Structures in which the electronegative element loses a σ-orbital or gains a π-orbital are favored. π-bonds tend to be favored over σ-bonds. The bond in NO+ resembles that in CO, whereas that in CN- resembles the bonding in N2.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 471-487 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ab initio SCF, CI, CEPA, and MCSCF techniques are compared and contrasted in a theoretical study of the 1s core ionized Li2 molecule from the point of view of core hole localization. In agreement with earlier studies of symmetric core ionized molecules, SCF theory is found to give a physically reasonable description of core ionization only when symmetry breaking is allowed. This results in a dramatic lowering of the energy of the core ionized state and hence of the ionization potential. By extension, CI wave functions that are developed in terms of a broken symmetry SCF reference plus its single and double excitations are found to perform significantly better than those constructed from symmetry adapted SCF orbitals. Alternatively, if the full point group symmetry is to be retained, a multiconfigurational treatment is called for and, in agreement with the conclusions of an analogous study on O2 [H. Ågren, P.S. Bagus, and B.O. Roos, Chem. Phys. Letters 82, 505(1981)], it is found that a modestly sized MCSCF wave function is capable of accounting for the energetic effects of symmetry breaking. Potential energy curves for Li2 and several states of core ionized Li2 have been calculated, allowing predictions of the adiabatic ionization potential and vibrational, satellite, and Auger structures in the photoelectron spectrum of Li2 to be made.
    Zusätzliches Material: 4 Ill.
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 489-505 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A practical algorithm is described for generating a set of symmetry- and spin-adapted antisymmetrized products of molecular orbitals (SAAPs) which form an orthogonal basis for a full active configuration space. The spin-adaptation is completely general. The space-symmetry adaptation is accomplished for the groups C∞v and D∞v.
    Zusätzliches Material: 4 Tab.
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  • 72
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 685-697 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A complete description of the rotational isomerism of monothioformic acid is presented. Ab initio results concerning the barrier heights and the energy difference between the stable isomers are in good agreement with the experimental data. A reduced potential function deduced from our calculations has been used to characterize the kinetics and thermodynamics of the rotational isomerization. The reported ab initio values of equilibrium constants are in good agreement with the experimental ones. From the analysis of the available experimental data, we have found that the free energy and enthalpy behavior are quite similar and that no noticeable entropy contributions are involved in the internal rotation, in agreement with previous studies on unimolecular isomerization processes.
    Zusätzliches Material: 3 Ill.
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 723-723 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 1-1 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 85-103 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The equilibrium geometry, stabilization energy, and electric polarizability of formic acid, formamide, and the three possible cyclic hydrogen-bonded pairs are obtained by ab initio calculations using the STO-3G, 4-31G, and 6-31G** bases. These three properties are found to be very much dependent on the basis set extension. The polarizability of the dimers is found to be basically additive in contribution from the monomeric moieties.
    Zusätzliches Material: 5 Ill.
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  • 76
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 133-147 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the course of conformational motions of molecules the changes in shapes of electronic charge distributions follow that of the nuclear framework. However, this coupling between the changes in the nuclear geometry and electron density may depend on the actual nuclear displacement; the coupling may be weak or strong for a given conformational motion. It is of some interest to analyze how faithfully the charge density variations follow the nuclear displacements in a family of conformational rearrangements. In certain cases small conformational changes may induce large changes in the shape of charge density distributions, while in other cases large and qualitatively important conformational changes may involve qualitatively inessential distortions in the shape of electron distributions. In this article we describe a new classification of conformations based on those domains of nuclear configuration space within which the „shape groups“ (symmetry independent homology groups) of the electric charge density remain invariant. Such an analysis might be valuable when seeking correlations between molecular structure and certain biological or biochemical activities.
    Zusätzliches Material: 5 Ill.
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  • 77
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 211-219 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Practical aspects of the calculation of the proton transfer process in a model of the active site of the thiol protease papain are explored with basis sets of different sizes. Results from ab initio calculations with the STO-3G, 4-31G, 6-31G, 6-31G* basis set, and a 6-31G basis set augmented with polarization functions on the sulfur atom are compared for their performance in describing the proton transfer energy. The nature of the convergence of the calculated properties of the potential curve for proton transfer with the increase in basis set indicates the need for a split-valence basis set and for polarization functions on the sulfur in order to achieve an appropriate description of this system. Correlation corrections to the calculated energies are shown to contribute significantly to the characteristics of the proton transfer energy curve.
    Zusätzliches Material: 4 Ill.
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 281-288 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The scope of multistep modeling (MSM) is expanded by adding a least-squares minimization step in the procedure to fit backbone reconstruction consistent with a set of C-alpha coordinates. The analytical solution of Phi and Psi angles, that fits a C-alpha x-ray coordinate [1] is used for tyr-tRNA synthetase. Phi and Psi angles for the region where the above mentioned method fails, are obtained by minimizing the difference in C-alpha distances between the computed model and the crystal structure in a least-squares sense. We present a stepwise application of this part of MSM to the determination of the complete backbone geometry of the 321 N terminal residues of tyrosine tRNA synthetase to a root mean square deviation of 0.47 Å from the crystallographic C-alpha coordinates.
    Zusätzliches Material: 7 Ill.
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  • 79
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 325-330 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have examined an application of the weighted identification number in the QSAR study of the toxicity of aliphatic ethers on mice. The results obtained are superior to those achieved by the connectivity index.
    Zusätzliches Material: 3 Tab.
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  • 80
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987) 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 13-14 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 89-97 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ab initio self-consistent-field electronic state calculations have been carried out for an interstitial-iron-substitutional-boron impurity pair complex in silicon. The calculations do not provide support for the currently accepted microscopic ionic model for the pair. Rather, we have shown that the covalent effects play a basic role in determining the physical properties of the complex.
    Zusätzliches Material: 3 Ill.
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  • 83
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 115-129 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By analyzing the convergence properties of the lattice sums in the exchange part of the restricted Hartree-Fock orbital energy, we isolate the source of the nonanalytic behavior of a partially occupied band at the Fermi energy. This analysis shows how an extended system behaves qualitatively differently from a finite system but also provides a possibility of following the development of nonanalyticity as the size of the system grows.
    Zusätzliches Material: 3 Ill.
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  • 84
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 163-170 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The aromatic (A) and quinoid (Q) forms of polythiophene (PT) have entirely different energy gaps: ∼0.5 eV for the quinoid form and ∼2 eV for the aromatic form, respectively. The energy gaps and stability of derivatives of PT are studied by total MNDO geometry optimization using energy band theory for the total energy calculations followed by a Hückel energy band calculations to approximate the energy band structure. Addition of fused rings to PT reverses the order of stability of the aromatic and quinoid isomers and the ordering in the size of the energy gaps. Small energy gap polymers are suggested on the basis of the calculations.
    Zusätzliches Material: 3 Ill.
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  • 85
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 191-198 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemical reactions and conformational changes of N-atom systems can be described as displacements in a (3N-6)-dimensional metric configuration space M provided with a global metric. Although space M has a metric, it is not in general a vector space; it is a topological space. In contrast to the commonly used internal configuration spaces based on bond length/bond angle internal coordinates, and having no global metrics, within space M each internal configuration of the nuclei of the molecule corresponds to one and only one point of the space. This property of M is advantageous when analyzing chemical reactions. The global metric of M ensures that differences between any two internal configurations can be interpreted as a distance in this space that allows one to provide M with coordinate systems by turning M into a manifold with boundary. Certain formal reaction paths show some counterintuitive behavior within this space: they may undergo a formal reflection at some points of M. A condition, the tangent criterion, is used for the diagnosis of such reaction paths and for the determination of special nuclear configurations where such reflections occur.
    Zusätzliches Material: 3 Ill.
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  • 86
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 649-662 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Energies and geometries for a number of small hydrogen bonded dimers have been calculated by semiempirical method based on a perturbation approach. Results have been compared with experimental and the best theoretical data. A quite good description of equilibrium configurations has been obtained in every case when local multipoles from sufficiently accurate wave functions have been used. Hydrogen bond lengths have not been predicted with sufficient precision. Results indicate, however, that it should be possible to achieve improvement in the framework of the applied calculation scheme by modification of the parameter values.
    Zusätzliches Material: 4 Ill.
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  • 87
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 283-295 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We examine the photoaddition of hydroxylazoaromatic compounds and related thione analogs with olefins. By examining the properties of the lowest lying singlet and triplet states, we conclude that the product distribution is best described by the unpaired spin density of the triplet state. This suggests that absorption of light by the aromatic is followed by conversion into the triplet, and this triplet is the active precursor. Since unrestricted molecular orbital calculations are easily performed on the lowest triplet of these aromatics, prediction of possible products is straightforward.
    Zusätzliches Material: 7 Ill.
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  • 88
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 267-282 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hydrogen addition to acetylene has been studied by molecular orbital methods with the unrestricted Hartree-Fock (HF)approach and with Møller-Plesset (MP) perturbation theory up to fourth order using the 6-31G*, 6-31G**, and 6-311G** basis sets. For each basis set a number of points along an approximate reaction path were calculated by fixing the attacking H—C distance and optimizing all of the remaining parameters. At these geometries, single point MP4 calculations with and without spin projection were carried out, yielding the position, height, and shape of the addition barrier at the various levels of calculation with each of the three basis sets. The results of this approach were confirmed by a grid search of the region near the transition state using the 6-31G* basis set. The unprojected MP2, MP3, and MP4 barriers are too narrow and are 10-20 kcal/mol too high. With spin projection, the barriers are much lower and broader. At the PMP4SDTQ/6-311G** level, with zero point energy calculated at UHF/6-31G*, the vibrationally adiabatic barrier at 0 K is 4.0 kcal/mol, and the attacking H—C distance is 2.0 Å.
    Zusätzliches Material: 6 Ill.
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  • 89
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 313-319 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We explore the implications of static disorder on electron transfer (ET) in a microscopically inhomogeneous polar medium, where the environment of each solute is characterized by a single dielectric relaxation time, τ, with the distribution function of τ being related to the complex dielectric susceptibility. For the interesting situation of solvent-controlled ET, the decay of the population probability is nonexponential, which can be expressed in terms of a cumulant expansion. The microscopic decay function can be related to the macroscopic step-response function of the dielectric medium.
    Zusätzliches Material: 1 Ill.
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  • 90
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 355-362 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A self-consistent model capable of describing the interaction of a metal electrode/liquid electrolyte interface is presented. As in a real system, a capacity maximum shifted towards positive charges is obtained from the model. The metal is represented by the planar uniform background model (jellium). The solvent is described by a polar liquid whose response to charge is accounted for in terms of the local approximation. The interaction between the metal and ions is modelled by a charged plane placed near the metal surface. Charge neutrality of the whole system is preserved. The present model is a good approximation for highly concentrated solutions.
    Zusätzliches Material: 3 Ill.
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  • 91
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 733-737 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this paper we outline briefly how microlocal analysis can be applied to give a general approach to the mathematical theory of resonances in the semiclassical limit. We also describe recent results about the asymptotic behavior of resonances generated by closed trajectories and stationary points in the classical flow.
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  • 92
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 739-746 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this paper we make explicit constructions of a family Aθ of intertwining operators between the Schrödinger operator Hv = -Δ + v(x) and H0 = -Δ. The wave operators and the scattering matrix are expressed in terms of the Aθ, and some methods of inverse scattering are described.
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  • 93
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 707-731 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Examples from music and nuclear, as well as atomic and molecular, physics are given to introduce and illustrate the resonance concept. Some fundamental concepts of scattering theory such as the differential and the total cross section are presented. The concept of the collision complex is illustrated with a light particle scattering reaction in nuclear physics. The concept of channels is introduced, and this formalism (which is so far empirical in nature) is dressed in the language of quantum mechanics. Finally I show that our descriptions of phenomena in nuclear physics can also be used in atomic and molecular physics.
    Zusätzliches Material: 18 Ill.
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  • 94
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The analytic energy gradient method that we have recently implemented for CCSD wave functions is applied to fully optimize the pyramidal C3v and planar D3h structures of ammonia. Using a double-zeta plus polarization basis set, results for harmonic vibrational frequencies, infrared intensities, and dipole moments have been obtained. Comparison with different levels of truncated configuration interaction suggests that CCSD values are of better than CISD quality and generally closer to CISDTQ results.
    Zusätzliches Material: 3 Tab.
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  • 95
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 539-545 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Effective core potentials are utilized in conjunction with polarization propagator calculations of excited state properties. The propagator method employed is based on an antisymmetrized geminal power wave function as the reference state. Calculations are presented on the low-lying excited states of HF and NaH. All-electron and valence-electron results are compared for HF. The choice of basis set is found to be very important for obtaining good results.
    Zusätzliches Material: 6 Ill.
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  • 96
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 569-572 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The nonadiabatic energy correction term of the hydrogen molecule at large separation is discussed to determine whether or not the nuclear motion induces the inter-atomic interaction potential. Nonadiabatic vibrational motion of nuclei induces the internal charge polarization of atoms to give the novel correction term to the London R-6 force. The correction term is (4/M) (1/R3), which is important at large R despite the overwhelming magnitude of nuclear mass.
    Zusätzliches Material: 1 Ill.
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  • 97
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 755-794 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: As an extension of the recent atomic work of Krylstedt et al. [1, 2], we propose the synthesis of the static exchange plus polarization model within the multiple scattering Xα formalism and the exterior complex rotation method for the study of shape resonances occurring in molecular collisional systems. The bound state multiple scattering Xα method is reviewed with special attention to the form of the various wave functions for the different molecular regions. In connection with the inclusion of continuum electron exchange into the scattering model, we analyze a possible solution to the problem of asymptotical behavior caused by the local density-based free electron gas approximation used in this case. We also propose a method to fix the cutoff parameter, inherent in the polarization potential, for symmetry-related molecular participants in the scattering process, thereby obtaining a possible predictive power for the one-parameter scattering model.Titchmarsh-Weyl's theory is used to formally connect the above formulation to scattering theory. The theoretical difficulties in obtaining a unique meromorphic continuation of the S matrix are investigated in connection with the requirements on the actual potential to be exterior dilation analytic. Furthermore, the occurrence of asymptotic quantum numbers is noted and discussed in conjunction with muffin tin-like approximations and related exterior complex rotated schemes.It is found that the electron exchange part of the nonstatic one-body potential exhibits a functional form that is not exterior dilation analytic, albeit the general electron and nuclear many-body problem involving Coulomb forces are dilation analytic. Although the immediate consequences indicate a rotation angle (θ) dependence on the S matrix continuation, a uniquely defined assignment of the cutoff parameter r0 = r0(θ) makes the present nonstatic model “exterior dilation analytic” in the sense that it mimics the dilation analytic structure of the full many-body problem at the same time obeying “asymptotic” spherical symmetry via the associated constant of evolution. However, in the static exchange approximation the above difficulties are shown to be circumvented via a certain reformulation, leading to a regular analytic asymptotic form for the interaction potential.
    Zusätzliches Material: 1 Ill.
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  • 98
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987) 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 841-845 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the present article we show how the bound states of the Coulomb potential may be associated with resonances that occur when this potential is perturbed by a barrier potential. The main idea is to trace the bound states on successive switching on of the barrier perturbation. It is found that those bound states that are localized inside the barrier are highly sensitive to variation with respect to the barrier height, whereas those that are localized outside are less sensitive. However, there are certain intervals for the barrier height when the role of being “a state localized inside the barrier” is shifted from one bound state to another. The result can be pictured as a “relay race,” where the “deliveries of the baton” are carried out over corresponding avoided crossings. The baton is ultimately handed over to a shape-type resonance state.
    Zusätzliches Material: 3 Ill.
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  • 100
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 847-853 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl substitutents located peri to bay-region benzo rings of polycyclic aromatic hydrocarbons generally reduce or eliminate carcinogenic activity, most likely because such substituents force the hydroxyl groups of dihydrodiol intermediates to adopt preferentially pseudodiaxial, rather than pseudodiequatorial, conformations. Empirical force field calculations have been employed to examine the influences of peri and other positional substituents on hydroxyl conformation, taking naphthalene, anthracene, and phenanthrene as model compounds. For the unsubstituted naphthalene and anthracene dihydrodiols, the pseudodiequatorial conformation is preferred. This preference is reduced by adjacent methyl substitution and reversed by peri methyl substitution. Because of steric crowding the phenanthrene bay-region dihydrodiol preferentially adopts a pseudodiaxial conformation. The results are discussed in relation to recent experimental evidence.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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