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  • Artikel: DFG Deutsche Nationallizenzen  (6.926)
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  • 1
    ISSN: 1432-1440
    Schlagwort(e): Kidney ; Glomerulus ; Mesangium ; Mesangial failure ; Electron microscopy ; Animal models
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We present a structural analysis of the ability of the biomechanical unit consisting of mesangium and glomerular basement membrane to maintain normal capillary architecture in the face of mechanical challenges due to high intraglomerular pressures. Capillary support function may be considered in terms of the stabilization of local form (development of wall tension against capillary dilation) and global form (centripetal fixation of capillary loops to maintain higher order form). The pathologic consequences of the loss of this support are illustrated by way of experimental models of mechanical mesangial failure. Such failure may express itself as mesangial widening, increased transmesangial macromolecule “traffic,” ballooning of capillary segments, and unfolding of capillary loops. Mechanisms are described by which these structural changes may lead to segmental glomerular sclerosis.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 70 (1992), S. S127 
    ISSN: 1432-1440
    Schlagwort(e): Carvedilol ; Kidney ; Hypertension ; Renal hemodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Antihypertensive drugs have differing effects on renal hemodynamics, tubular function, plasma electrolytes, and hormonal responses. Nonselective β-blockers without intrinsic sympathomimetic activites, such as propranolol, have been reported to reduce renal blood flow and to cause a modest decrease in glomerular filtration rate. Carvedilol is a new multiple action agent displaying nonselective β-blockade without intrinsic sympathicomimetic activity, α1-adrenoceptor blockade (probably responsible for its vasodilator activity), and possibly also calcium antagonist properties. The presence of these different pharmacodynamic properties results in a different effect on the kidney as compared with, e.g., propranolol. In the dog, intrarenal infusion of carvedilol resulted in a renal vasodilator response with preservation of renal blood flow and without inducing sodium retention; in contrast, propranolol induced a renal vasoconstrictor response and sodium retention in this model. A renal vasodilator response to carvedilol was also reported in spontaneously hypertensive rats (SHR) and in DOCA-salt SHR. In contrast to labetalol, i.v. infusion of hypotensive doses of carvedilol in conscious SHR did not cause sodium retention. Carvedilol was effective in controlling hypertension and preserving renal function in a rat model of progressive hypertensive renal disease. In patients with essential hypertension, carvedilol was reported to reduce renal vascular resistance in the presence of reduced perfusion pressure, allowing for normal renal autoregulation of renal blood flow. Although a small reduction in glomerular filtration rate was seen after acute administration, renal function was preserved during chronic treatment. It is concluded from these studies that renal perfusion and renal function are well maintained during acute and chronic treatment with carvedilol. The compound does not appear to cause sodium retention, and preliminary animal test data suggest the possibility of a renoprotective effect.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 70 (1992), S. 692-697 
    ISSN: 1432-1440
    Schlagwort(e): Kidney ; Urine concentration ; Volume regulation ; Potassium ; Bicarbonate ; Aldosterone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Cells of the renal medulla regulate their volume by transmembrane ion movements when exposed to large changes in osmolality. Since renal cells in culture release KHCO3 in response to hypotonic stress [11], we investigated the effect of an acute water load on urinary KHCO3 excretion in 5 healthy individuals. Water diuresis was induced by the ingestion of 1.51 hypoosmolal fluid (22 mosm/kg H2O) over 15 min. The rate of urinary volume excretion increased from an initial value of 1.4 ml/min to 9.3 ml/min after 75 min. Urinary osmolality dropped from an initial value of 940±32 mosm/kg H2O to 74±4 mosm/kg H2O (n = 5). The decrease of osmolality was accompanied by the transient release of potassium and bicarbonate. Peak values of KHCO3 excretion were observed between 30 and 45 min after the onset of the experiment corresponding to the drop of urinary osmolality. The magnitude of renal potassium release correlated significantly (r=0.93; P 〈 0.05) with endogenous plasma aldosterone concentrations measured prior to the experiment in the 5 volunteers. We conclude that medullary epithelial cells release KHCO3 when exposed to hypotonic stress. The volume regulatory response is upregulated by aldosterone.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 70 (1992), S. 735-739 
    ISSN: 1432-1440
    Schlagwort(e): Kidney ; Calcium ; Phosphate ; Sodium ; Caries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Clearance studies were performed for 2 days in two groups of age-matched young female volunteers: those with low caries prevalence and those with high caries prevalence. Both groups were kept on a low-calcium diet for 1 week and received 0.5 g calcium at the beginning of the second day. In both groups, glomerular filtration rate, urinary flow rate and renal excretions of sodium, calcium, and phosphate were subject to significant circadian variations. In both groups the administration of calcium led to a significant increase in renal excretion of sodium and calcium and a significant decrease in that of phosphate. On the first day, calcium excretion was significantly greater in those with low caries prevalence than in those with high caries prevalence, pointing to altered calcium homeostasis in this group.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-1912
    Schlagwort(e): 3H-noradrenaline release ; SHR ; Kidney ; Prejunctional β-adrenoceptors ; Adrenaline ; Isoprenaline ; cAMP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The aim of the present study was to investigate β-adrenoceptor modulation of noradrenaline release from sympathetic nerves in superfused cortical kidney slices of 4-week-old spontaneously hypertensive rats (SHR) and age-matched controls (WKY). After preincubation with 3H-noradrenaline the kidney slices were electrically stimulated in superfusion chambers. The stimulation induced (S-I) outflow of radioactivity was mainly composed of unmetabolized 3H-noradrenaline in both strains and thus taken as an index of noradrenaline release. There was a frequency-dependent (1.25–20 Hz) increase in the S-1 outflow of radioactivity. At all stimulation frequencies tested S-I outflow of radioactivity was similar or even slightly lower in SHR than in WKY kidney slices in either the absence or presence of cocaine (10 μmol/l). The non-selective β-adrenoceptor agonists isoprenaline (0.l gmol/1) and adrenaline (0.01 and 0.1 μmol/l) enhanced S-I outflow of radioactivity. The facilitatory effects of isoprenaline (0.1 μmol/l) and adrenaline (0.1 μmol/l) were blocked by the selective β2-adrenoceptor antagonist ICI 118551 (0.1 μmol/l) but not by the selective β1-adrenoceptor antagonist atenolol (0.3 μmol/l). The cell-permeable CAMP analogue 8-bromo-cAMP (300 μmol/l) enhanced S-1 outflow of radioactivity to a similar extent in both SHR and WKY kidney slices. A combination of 8-bromo-cAMP (300 μmol/l) and adrenaline (0.1 μmol/l) did not enhance S-1 outflow of radioactivity to a greater extent than 8-bromo cAMP (300 μmol/l) alone in both strains. However, the facilitatory effects of isoprenaline (0.1 μmol/l) and adrenaline (0.1 μmol/l) but not that of adrenaline (0.01 μmol/l) were significantly greater in SHR than in WKY. The results suggest that stimulation of prejunctional β2-adrenoceptors by adrenaline even in the absence of a-adrenoceptor blockade enhances noradrenaline release in kidney cortex of young SHR and WKY. This β2-adrenoceptor mediated effect may possibly be dependent on cAMP formation. The greater facilitatory effects of isoprenaline (0.1 μmol/l) and adrenaline (0.1 μmol/l) in SHR as compared to WKY are in accord with receptor binding studies which show a higher density of β2-adrenoceptors in SHR than in WKY kidney cortex.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 70 (1992), S. S120 
    ISSN: 1432-1440
    Schlagwort(e): Hypertension ; Kidney ; Antihypertensive drugs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Antihypertensive therapy influences kidney function by different mechanisms depending on the mode of action of the drug used. The GFR is improved by calcium entry blockers and ACE inhibitors, unaffected by vasodilators, α-blockers and centrally acting sympatholytics and impaired by β-blockers. The same is true for renal blood flow and is due to changes of renal vascular resistance. Renal sodium excretion is impaired mostly by vasodilators, by α-blockers, sympatholytics and β-blockers; in contrast, calcium entry blockers and ACE inhibitors acutely induce natriuresis. The RAAS is stimulated by vasodilators, unaffected by α-blockers and sympatholytics and suppressed by β-blockers. Plasma catecholamines are stimulated by vasodilators and suppressed by centrally acting sympatholytics and unaffected by the others. Induction of acute renal functional impairment is reported for ACE inhibitors under conditions of compromised renal perfusion pressure such as in renal artery stenosis. These data from the literature reviewed are supported by our own experimental data on sodium balance under different drugs and micropuncture data in experimental renal artery stenosis. To achieve effective antihypertensive treatment with a low profile of side effects, careful monitoring of renal function seems to be mandatory.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 51 (1992), S. 42-47 
    ISSN: 1432-0827
    Schlagwort(e): Kidney ; Endoplasmic reticulum ; Calcium ; In vivo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Calcium uptake by the endoplasmic reticulum (ER) is important for cellular calcium homeostasis, yet its regulation in nonmuscle cells is poorly understood. We reported that Ca2+ uptake by a light fraction of canine renal cortical ER (LER) is stimulated by protein kinase C in vitro. Here we describe conditions in vivo that stimulated renal cortical LER Ca2+ uptake. Thirty minutes after contralateral nephrectomy in the dog, 45Ca2+ uptake into renal cortical LER was increased 42% above control LER. There was no difference in LER Ca2+ uptake 24 hours after uninephrectomy. Acute denervation did not reproduce the increase in LER 45Ca2+ uptake seen at 30 minutes after uninephrectomy, nor did prior thyroparathyroidectomy abolish it. Forty-eight hours after thyroparathyroidectomy, 45Ca2+ uptake activity into renal cortical LER was decreased ≈sevenfold. In a proximal tubular cell line (LLC-PK1), 30-minute incubation with 12-O-tetradecanoylphorbol-13-acetate doubled 45Ca2+ uptake into a nonmitochondrial pool. Pretreatment with epidermal growth factor halved ER Ca2+ uptake, whereas insulin-like growth factor and growth hormone, alone or in combination, had no effect. Our data suggest that Ca2+ uptake into renal cortical ER is stimulated acutely during compensatory renal growth, perhaps through protein kinase C, and is stimulated chronically by parathyroid hormone.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 420 (1992), S. 301-304 
    ISSN: 1432-2307
    Schlagwort(e): Kidney ; Blood vessels ; Arterialisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An abnormality of blood vessels was noted in a biopsy of a renal transplant. This took the form of apparent development of a new artery inside and concentric with the old, with elastic laminae and a muscular media, separated from the old internal elastic lamina by poorly cellular tissue. In a systematic study of material from another 119 renal transplants, 13 nephrectomy specimens for chronic pyelonephritis and hydronephrosis, 28 renal biopsies showing interstitial nephritis, and 18 renal biopsies showing small vessel vasculopathy of accelerated hypertensive type, similar arterial changes were seen in another 10 renal transplants that showed chronic vascular rejection, 1 case of chronic interstitial nephritis, and 3 cases of vasculopathy, 2 with accelerated hypertension and 1 with systemic sclerosis. One renal transplant also showed apparent development of new muscular veins inside old veins. Immunohistological study for smooth muscle actin confirmed that the apparently new arterial and venous structures contained smooth muscle cells. The arterial abnormality may be called arterialisation of intrarenal arteries. This change appears to be not rare, is distinctive, and has scarcely been previously recognised or reported as a response of intrarenal blood vessels to damage.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 420 (1992), S. 533-537 
    ISSN: 1432-2307
    Schlagwort(e): Peripolar cell ; Renin ; Juxtaglomerular apparatus ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The glomerular peripolar cell may be a secretory component of the juxtaglomerular apparatus. To investigate this hypothesis we studied kidneys with the renin-angiotensin system activated by two different stimuli in order to compare the responses of peripolar cells and renin-secreting cells. We examined 10 human kidneys, removed for renal artery stenosis and 11 autopsy cases of Addison's disease with appropriate controls. We counted granulated peripolar cells in serial paraffin-embedded sections and renin-containing cells were quantified using an immunoperoxidase technique with an antiserum to human renin. There was a five-fold increase in the number of renin-containing cells in both renal artery stenosis and in untreated, but not in treated, Addison's disease. Peripolar cells were increased in number in three cases of renal artery stenosis, but were unaltered in both treated and untreated Addison's disease. Therefore, neither a reduction in renal perfusion pressure (renal artery stenosis), nor sodium depletion (Addison's disease) consistently affect peripolar cells in humans. These findings do not support the hypothesis that the peripolar cell is part of the juxtaglomerular apparatus.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Urological research 20 (1992), S. 271-274 
    ISSN: 1434-0879
    Schlagwort(e): Kidney ; Fetal kidney ; Renal volume ; Renal growth ; Fetal urology ; Renal anomalies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The growth of fetal kidney volume was studied in 290 specimens taken from 145 fresh human fetuses (85 males and 60 females) with gestational age ranging from 13 to 36 weeks postconception (WPC). Normative equations and curves of the growth of renal volume were obtained for male and female fetuses and for the whole sample in the second trimester (13–24 WPC) and in the third trimester (25–36 WPC) of gestation. There was no difference between the growth in volume of the right and left kidneys. Fetal kidney volume increases with a more intense rhythm in the early fetal period (13–24 WPC). During the second trimester, there was no difference between the values for renal volume of male and female fetuses. In the third trimester, male fetuses had renal volumes significantly greater than the female fetuses. The normative parameters of renal volume could have practical applications in detection and monitoring of renal anomalies in fetal and perinatal urology.
    Materialart: Digitale Medien
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  • 11
    ISSN: 1432-0568
    Schlagwort(e): Kidney ; Endothelium ; Glomerular mesangium ; Lung ; Autoradiography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The morphological effect of endothelin-1 (ET-1) and the distribution of endothelin-binding sites on the kidney and lung was investigated ultrastructually by intravenous injection of [125I]-ET-1 into rats. About 10% decrease of the diameter of glomeruli was observed at 10 min after the injections of ET-1 or [125I]-ET-1 (1.3–2.4 nmole/kg). When localization of [125I]-ET-1 in the kidney was examined by light and electron microscopic radioautography, silver grains were preferably localized on the fenestrated endothelial cells of glomeruli and peritubular capillary endothelial cells. Some grains were also localized on the interdigitating processes of urinary tubules. Quantitative analysis of silver grains in the glomeruli showed that 83% of grains were located on the fenestrated endothelial cells, 12% on the podocytes of visceral cells, and 5% on mesangial cells at 10 min. After 60 min, 50% of silver grains were incorporated into the cytoplasm of fenestrated endothelial cells. In contrast to glomeruli, silver grains were rare on the arteries and large arterioles. However, a few silver grains were often observed on the smooth muscle cells of small arterioles (8–20 μm in diameter). In the lung, 70% of silver grains were located on the alveolar capillary endothelial cells. These results indicate the abundance of ET receptors on the glomerular fenestrated endothelium, peritubular fenestrated endothelium and alveolar capillary endothelium.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 185 (1992), S. 291-297 
    ISSN: 1432-0568
    Schlagwort(e): Kidney ; Nephron development ; Chick
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In the avian kidney three nephron types may be identified: mammalian-type nephrons with long (MTN-I) and short (MTN-II) loops of Henlé, and reptilian-type nephrons (RTN). By the method of microdissection the maturation of the nephrons of domestic fowl kidney has been studied. From the 14th day of incubation it is possible to isolate the MTN-I which appear first; all three nephron types may be isolated after 18 days of incubation. The thin limb of Henlé's loop in MTN-I appears after hatching, and the length of this segment in 1-day-old chicks is 0.1–0.13 mm. In 60-day-old chicks its length has approximately doubled. The transition of the thin segment to the thick segment is situated in the descending part of Henlé's loop. In the course of development, the relative length of all nephron segments in MTN-I increases uniformly, while in MTN-II and in RTN the relative length of the proximal and distal convoluted tubules increases. At all stages of development, MTN-I are the longest among the three groups of nephrons and have the largest glomeruli. The comparison between developing avian and mammalian kidneys shows great similarities in the process of maturation in analogous nephron types in these two classes of vertebrates.
    Materialart: Digitale Medien
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  • 13
    ISSN: 1432-0568
    Schlagwort(e): Artery ; Endothelial cell ; Stress fiber ; Elastic fiber ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The structure of the intracellular actin filaments and the extracellular matrices was studied in the distal interlobular arteries in the rat kidney, employing three different morphological techniques, including rhodamin-phalloidin staining of cryosections, resorcin-fuchsin staining of paraffin sections, and a cold dehydration procedure for electron microscopy. The endothelial cells possess longitudinally running stress fibers. The inner elastic layer is composed of meshworks of elastic fibers encompassing numerous pores. The smooth muscle cells containing abundant actin filaments are arranged circumferentially around the vascular axis. The endothelial stress fibers are found mainly in the basal half of the endothelial cells, and anchor onto the basal cell membranes. The elastic meshworks send off longitudinal branch fibers to contact the endothelial cell membranes at the anchoring sites of stress fibers. In addition circumferential branches run toward the smooth muscle cells. The functional significance of the intracellular contractile apparatus and the extracellular tensile component in small arteries was discussed.
    Materialart: Digitale Medien
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  • 14
    ISSN: 1432-0428
    Schlagwort(e): Kidney ; hypertrophy ; insulin-like growth factors ; insulin-like growth factor binding proteins ; streptozotocin ; diabetes ; rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The insulin-like growth factors, insulin-like growth factor I and insulin-like growth factor II are bound to six distinct classes of insulin-like growth factor binding proteins (IGFBPs) in the circulation and in extracellular fluids. Diabetic renal hypertrophy is preceded by a transient increase in kidney insulin-like growth factor I suggestive of a renotropic function for insulin-like growth factor I. In order to examine a possible involvement of IGFBPs in initial diabetic kidney growth and in kidney insulin-like growth factor I accumulation, we studied rat kidney IGFBPs by ligand blotting during the first 4 days after induction of diabetes. Six distinct bands were identified in kidney and liver tissue with apparent molecular weight values of 38–47 (doublet), 34, 30, 24 and 20 kDa. The 38–47 kDa doublet band probably corresponds to the insulin-like growth factor binding subunit of IGFBP-3, the 24 kDa band to IGFBP4 and the 30 kDa band to IGFBP-1 and/or IGFBP-2, as these IGFBPs in rats have similar molecular weight. In untreated diabetic rats a transient increase in the kidney 30 kDa band was demonstrable 24 h after induction of diabetes with a maximal rise (two-fold) after 48 h, followed by a decrease to baseline values after 4 days. In untreated diabetic rats the 38–47 kDa doublet band also increased (two-fold) in kidney during the first 2 days after induction of diabetes, followed by a subsequent decrease. Insulin-treatment prevented both the increase in the 30 kDa and in the 38–47 kDa bands. Kidney weight in untreated diabetic rats increased by 26 % after 4 days. In conclusion, the present study shows a transient increase in the 30 kDa and the 38–47 kDa IGFBP species in hypertrophying diabetic kidneys, contemporarily with the previously described transient increase in extractable kidney insulin-like growth factor I content. These findings support the concept that IGFBPs may be involved in the action of insulin-like growth factor I and possibly in the diabetic kidney insulin-like growth factor I accumulation.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Surgical and radiologic anatomy 14 (1992), S. 113-117 
    ISSN: 1279-8517
    Schlagwort(e): Kidney ; Renal artery ; Multiple renal arteries ; Renal transplantation ; Renal angiography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé La vascularisation artérielle du rein a été analysée à partlr de 266 dissections provenant de 133 sujets d'anatomie. Les résultats anatomiques sont les suivants: une seule artère hilaire est présente dans 53,3% des cas; une artère hilaire associée à une branche polalre supérieure extrahilaire dans 14,3% des cas; deux artères hilaires dans 7,9% des cas; trois artères hilaires dans 1,9% des cas; une artère polaire supérieure dans 6,8% des cas; une artère polaire inférieure dans 5,3% des cas; enfin d'autres variations dans 8,5% des cas. Sont envisagées les applications urologiques et radiologiques de ces constatations dans la transplantation rénale, la pathologie hypertensive d'origine rénale, la traumatologie rénale, la radiologie interventionnelle, la chirurgie conservatrice et l'oncologie.
    Notizen: Summary The renal arterial supply was analyzed in 266 kidneys dissected from 133 fixed adults subjects. The anatomical findings are presented: 1 hilar artery in 53.3% of the cases, 1 hilar artery with 1 superior pole extra-hilar branch in 14.3%, 2 hilar arteries in 7.9%, 3 hilar arteries in 1.9%, superior polar artery in 6.8%, inferior polar artery in 5.3% and other variations in 8.5%. The urological and radiological implications of these findings in kidney transplantation, renovascular hypertension, renal trauma, interventional radiology, conservative surgery and oncologic surgery are discussed.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 51 (1992), S. 35-41 
    ISSN: 1432-0827
    Schlagwort(e): Kidney ; Endoplasmic reticulum ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary A subcellular fraction enriched in cytochrome c reductase (7.9-fold) and relatively de-enriched (0.64-fold) in Na+/K+-ATPase was prepared from canine kidney cortex by sucrose density gradient ultracentrifugation. It was shown by electron microscopy to consist primarily of a light fraction of endoplasmic reticulum (LER). LER vesicles displayed ATP-dependent 45Ca2+ uptake that was insensitive to 10 mM KCN or NaN3, and was promptly released by 20 μM A23187 or ionomycin. Inositol-1,4,5-trisphosphate (IP3) appeared to produce a time-dependent release of 45Ca2+. Vanadate inhibited 45Ca2+ uptake with a Ki≈0.3 mM, further suggesting that the activity resided in the ER rather than the plasma membrane. 45Ca2+ uptake by LER, at 5 μM total [Ca2+], displayed a strong dependence on divalent cations (Mg2+〉Co2+〉Mn2+≫Ba2+≥Cd2+≥Sr2+, present at 2 mM) as well as on monovalent cations (Na+≥K++Na+ 〉K+〉Li+〉choline+), and anions (Cl-〉acetate-≥NO3 -≥F-〉H2PO4 -≫gluconate-≥oxalate=≫SO4 =). It had a fairly narrow pH optimum (7.25–7.50). Preincubation (10 min) of LER vesicles with 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated LER Ca2+ uptake; this effect was enhanced in the presence of renal cytosol [5% (vol/vol)]. However, Ca2+ uptake was not affected by preincubation with dibutyryl cyclic AMP, calmodulin, or 1,25-(OH)2-vitamin D3, either in the absence or presence of renal cytosol. Thus, the Mg2+-ATP dependent 45Ca2+ uptake activity of this canine renal cortical LER fraction displays modulation by IP3, TPA, and pH that appears to be physiologically relevant.
    Materialart: Digitale Medien
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  • 17
    ISSN: 1432-1084
    Schlagwort(e): Gd-DOTA ; Contrast media ; Kidney ; Renal failure ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The aim of this study was to assess the pharmacokinetics and tolerance of Gd-DOTA (DOTAREM) in non-dialysed patients with chronic renal failure. Eight patients with chronic renal failure (creatinine clearance between 10 and 60 ml/min) and four healthy volunteers were given i.v. Gd-DOTA (0.1 mmol/kg). Blood and urine samples were collected. Gd-DOTA tolerance was also studied (vital signs, biological parameters, adverse reactions). In healthy volunteers, Gd-DOTA was rapidly distributed in the extracellular space and almost totally eliminated in the urine (glomerular filtration, 93.3±4.7% of the dose 24 h post injection). In patients with chronic renal failure, a delayed and almost total urinary elimination observed with a correlation between Gd-DOTA clearance and plasma creatinine clearance (r = 0.964). Tolerance was good with no significant modification of renal function or other parameters. These results confirm previous studies and indicates that DOTAREM can be used safely for patients with chronic renal failure.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 151 (1992), S. S76 
    ISSN: 1432-1076
    Schlagwort(e): Ethics ; Psychology ; Living organ transplantation ; Paediatrics ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract There is far-reaching consent in the literature that public and consensual agreements on the basics of the different aspects of medical ethics are inalienable before the instigation of any innovative transplant procedure. In the case of a certain method and/or of an individual patient, however, the ultimate ethical evaluation can most likely never be entirely complete before this application. Ethical evaluation depends on the actual criteria used, the present knowledge regarding the risk-benefit-balance as well as on the ethical evaluation of the patient's and his family's own feelings and expectations which are not entirely conscious. In relation to the so-called “fundamental and constant ethical guidelines” and under a psychological perspective potential, ethical conflict constellations are presented which have to be dealt with in the process of ethical and psychological evaluation before living organ transplantation.
    Materialart: Digitale Medien
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  • 19
    ISSN: 1432-0738
    Schlagwort(e): Kidney ; Liver ; Cell proliferation ; Rat ; Mouse ; p-Dichlorobenzene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Cell proliferation in the kidneys and livers of rats and mice exposed short-term to p-dichlorobenzene (p-DCB) was evaluated by immunohistochemical measurement of bromodeoxyuridine (BrdU) incorporation into nuclei of DNA-synthesizing cells. p-DCB was given by gavage at two doses up to 600 mg/kg body weight for 4 days. The cumulative fraction of proliferating cells was increased in the proximal tubule epithelial cells of male rats at the high dose, but not at the low dose nor in females at either dose using gamma-glutamyl transferase reaction to identify tubular cells. Also, no increase in cell proliferation was found in mouse kidneys. The fractions of proliferating cells in the livers of rats and mice of both sexes were also increased. The increased cell proliferation in only male rat kidney and in the livers of mice of both sexes correlates with the reported carcinogenic effects of p-DCB in those tissues. However, the finding that p-DCB also induced cell proliferation in the livers of rats of both sexes, which were not a site of p-DCB-induced tumors in bioassays, and in female mice at the low dose, which was not affected by an increase in tumors, reveals a lack of concordance and indicates that acute induction of cell proliferation is not sufficient to lead to carcinogenesis.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 151 (1992), S. S13 
    ISSN: 1432-1076
    Schlagwort(e): Kidney ; Transplantation ; Infant ; Uremia ; Development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Renal transplantation is widely accepted as the treatment of choice for endstage renal failure in childhood. Since dialysis is regularly applied to infants with renal failure, the question logically arises, can infants also receive renal transplants and what are the outcomes? A review of the literature and the clinical experience at the University of Minnesota supports the performance of renal transplantation in infancy. Present patient and graft survival rates for infants are indistinguishable from those of older children. While living adult donors are preferred, adult cadaveric kidneys have also been successfully transplanted. Following successful transplantation, the infants have generally enjoyed “catch-up” growth and accelerated psychomotor development. While there may be problems related to fluid and electrolyte balance in these smallest patients, the majority of the problems encountered mirror those seen in any child undergoing transplantation. Renal transplantation is regularly successful in infancy and should be considered an integral component of the therapy for any child with chronic renal failure.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 421 (1992), S. 168-175 
    ISSN: 1432-2013
    Schlagwort(e): Taurine ; Kinetic ; Stoichiometry ; Amino acid transport ; β-Amino acid ; Membrane vesicle ; Kidney ; Sodium-coupled transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The coupled transport of Na+ with taurine into snake renal brush-border membrane vesicles (BBMV) was studied using 5-s uptake conditions. Taurine transport into snake renal BBMV involved two parallel processes, one saturable (Na+-dependent) and one (Na+-independent) that behaved like passive diffusion. Below 1 mM taurine concentration, the Na+-dependent system accounted for 60% of total taurine uptake. Over both low (0.001–0.80 mM) and high (0.8–5.0 mM) taurine concentration ranges, the Na+-dependent taurine uptake within each range showed Michaelis-Menten kinetics, suggesting the presence of two independent saturable Na+-dependent transport systems for taurine. The high-affinity, low-capacity system saturated above 100 μM with a K m of 71.4±45.7 μM and a maximum velocity (V max) of 21.9±3.77 pmol (mg protein)−1 (5 s)−1. The low-affinity, high-capacity system saturated above 1 mM, with a K m of 1.11±0.63 mM and a V max of 252±47 pmol (mg protein)−1 (5 s)−1. The stoichiometric relationship between external Na+ concentration and taurine uptake (at 10 μM) by the high-affinity BBMV transport system was examined by the activation method under short-circuited conditions. The 5-s rate of taurine transport was a sigmoid function of increasing extravesicular Na+ concentration. Kinetic analysis of the interaction of Na+ with the high-affinity taurine transport system suggested that 3 Na+ ions (3.2±0.7) may be involved with 1 taurine molecule in the transport event. The data suggest the presence of a highly efficient and high-affinity reabsorptive taurine transport system on the luminal membrane of the kidney of the garter snake, a species that can secrete taurine in vivo.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 267 (1992), S. 233-239 
    ISSN: 1432-0878
    Schlagwort(e): Development, ontogenetic ; Kidney ; Glomerulus ; Distal convoluted tubule (DCT) ; Histamine ; Immunohistochemistry ; Hybridization, in situ ; Rat (Wistar)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An antiserum against conjugated histamine and two oligonucleotide probes that detect the mRNA encoding L-histidine decarboxylase (HDC) involved in histamine synthesis were used to study the appearance of histamine and its location in the kidneys of fetal, newborn and young postnatal rats and in the kidneys of pregnant rats. On embryonic days 16 and 18 (E16 and E18), some HA-immunoreactive (HA-ir) cells were found within the largest S-shaped bodies. Histamine was found to appear rapidly between the 18th and 20th embryonic days in the convoluted tubules of the kidneys. On postnatal day 0 (P0), the distal convoluted tubules and collecting ducts exhibited bright fluorescence, the intensity of which decreased quickly so that it was faint on day P4 and absent at later stages. In kidneys of pregnant rats HA-ir was found in the epithelium of both the Bowman's capsule, collecting ducts and in a few cells within the tubules. Nonuniform HA-ir was also detected within glomeruli. No evidence for the presence of L-histidine decarboxylase mRNA in kidneys of fetuses or pregnant rats was seen. It is concluded that distinct structures in the developing rat kidney contain histamine during a period around birth from day E20 to day P4. In the pregnant rat, the epithelium that is in direct contact with the urine flow is immunoreactive for histamine from day 16 to 20 of pregnancy. The results suggest that histamine is not synthesized locally in the kidneys but rather originates from other tissues.
    Materialart: Digitale Medien
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  • 23
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Glomerulus ; Stereology ; Morphometry ; Disector ; Quantitative methods, structural ; Rat (Sprague Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Alterations in numbers of glomeruli and glomerular cells occur in various renal disorders. Although values for these parameters have previously been reported for several species, the estimates have often been biased due to assumptions regarding glomerular and/or nuclear size and shape. Other studies have used tedious serial-section reconstruction methods. In the present study, unbiased stereological methods were used to estimate total numbers of glomeruli and individual glomerular cell types in normal rats. The kidneys of seven adult Sprague-Dawley rats were perfused with 4% paraformaldehyde and 1% glutaraldehyde in phosphate buffer and embedded in either glycolmethacrylate (for light microscopy, LM) or Epon/Araldite (for transmission electron microscopy, TEM). Total glomerular number was estimated using an LM physical disector/fractionator combination; the total number of cells per average glomerulus was estimated using an LM optical disector/ Cavalieri combination; and TEM physical disectors were used to count individual cell types. The normal rat kidney was found to contain 31764±3667 (mean±SD) glomeruli. An average glomerulus contained 674±129 cells, of which 181±53 were epithelial cells (podocytes), 248±53 were endothelial cells, and 245±45 were mesangial cells. An average renal corpuscle contained 117±27 parietal epithelial cells. Following sectioning and staining, less than 6.5 h was needed to obtain the above estimates for a single animal, with coefficients of variation (SD as a percent of the mean) ranging from 10% to 25%. The unbiased stereological methods used in the present study constitute an unbiased, precise and cost-efficient set of quantitative tools for assessing glomerular morphology in health and disease.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 267 (1992), S. 11-16 
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Distal tubule ; Tamm-Horsfall protein ; Cytokeratin ; Immunohistochemistry ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Various antibodies and lectins were used in a histological study of the human renal tubule, particularly of the distal end of the thick limb of the loop of Henle. The thick limb, identified by antibody to Tamm-Horsfall protein, ended abruptly, either at the macula densa or at a variable distance after it. At this point there was an abrupt change in cell size. Confocal microscopy and other techniques showed that this point marked an abrupt beginning of tubular staining by the cytokeratin antibody PKK 2 and the lectin UEA 1, with an abrupt end of staining by the lectin DBA. Distal from this point, there were gradual changes in staining of the tubule by various reagents including other antibodies to cytokeratins. These structural findings suggest that there is a fundamental change in the tubule at the end of the thick limb. The abrupt end to the thick limb in man resembles that seen in the rat and the rabbit.
    Materialart: Digitale Medien
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  • 25
    ISSN: 1432-0878
    Schlagwort(e): Transthyretin ; Kidney ; Peripolar cells ; Sheep, newborn
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Purified transthyretin has been isolated from sheep serum. Antiserum raised against this protein has been used with an indirect immunoperoxidase histochemical technique to identify transthyretin in newborn lamb kidney tissue. Transthyretin was found in proximal tubule cells and in glomerular peripolar cells. Preabsorption studies using purified transthyretin protein indicate that the immunoreactivity of the antiserum is specific to transthyretin.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 268 (1992), S. 567-570 
    ISSN: 1432-0878
    Schlagwort(e): Peripolar cell ; Glomerulus ; Kidney ; Cytoplasmic granules ; Scanning electron microscopy ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The peripolar cell is a unique cell type in the mammalian glomerulus. Peripolar cells are said to be identifiable during light microscopy by their cytoplasmic granules and by their position at the vascular pole; and during scanning electron microscopy by their distinctive surface morphology. We used both techniques to count peripolar cells in 6 normal rat kidneys. Scanning microscopy revealed that 55(±5)% of glomeruli contained at least one peripolar cell whereas light microscopy revealed granulated peripolar cells in only 4(±2)% of glomeruli. Vascular poles which contained peripolar cells previously identified by scanning were then examined by light and by transmission electron microscopy. Serial sections through these peripolar cells demonstrated the absence of cytoplasmic granules. Our observations suggest that the majority of peripolar cells in the rat contain no granules.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Journal of bioenergetics and biomembranes 24 (1992), S. 351-359 
    ISSN: 1573-6881
    Schlagwort(e): Kidney ; collecting tubule ; intercalated cells ; urinary acidification ; acid-base balance ; proton pump ; V-ATPase ; regulatory proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Vacuolar H+ ATPases participate in renal hydrogen ion secretion in both the proximal and distal nephron. These plasma membrane forms of the vacuolar H+ ATPase are regulated physiologically to maintain the acid-base balance of the organism. Proton transporting renal cells have requirements for constitutive acidification of intracellular compartments for normal endocytic and secretory functions. Recent experiments have begun to reveal how the kidney regulates these proton pumps independently. Vacuolar H+ ATPases are a family of structurally similar enzyme which differ in the composition of specific subunits. Cytosolic regulatory enzymes are present in renal cells which may affect vacuolar H+ ATPases in certain membrane compartments selectively. The vacuolar H+ ATPase in the plasma membrane of intercalated cells resides in a specialized proton-transporting apparatus that translocates the enzyme between an intracellular membrane pool and the plasma membrane in response to physiologic stimuli.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Langenbeck's archives of surgery 377 (1992), S. 222-225 
    ISSN: 1435-2451
    Schlagwort(e): Lymphocele ; Kidney ; Transplantation ; Rupture ; Trauma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Lymphozelen sind eine seltene Komplikation nach Nierentransplantationen (in unserem Krankengut 2,2%) und treten typischerweise in den ersten 3–4 Monaten nach der Transplantation auf. Im späteren Verlauf sind sie eine Rarität. Die traumatische Ruptur eines Nierentransplantats ist in unserem Krankengut mit über 1200 Nierentransplantationen bisher einmalig. Es wird der Fall eines 28jährigen Marines geschildert, der 19 Jahre nach der Transplantation eine traumatische Nierentransplantatruptur erleidet. Durch das Trauma wird eine vorbestehende chronische Lymphozele klinisch manifest. Die Histologic der Lymphozelenwand zeigt Fett- und Bindegewebe mit ausgeprägter Fibrose. Das diagnostische und therapeutische Vorgehen wird beschrieben und mögliche Zusammenhänge den beiden seltenen Ereignisse diskutiert.
    Notizen: Summary The lymphocele is a seldom complication after kidney transplantation (2.2% of our patients). This manifestation occurs typically 3–4 months after transplantation, as a late complication it's a rarity. The rupture of a kidney graft because of a trauma is unique in our clinical experience, which contains more than 1200 kidney transplantations. We report the case of a 28-year-old man who had 19 years after transplantation a traumatic rupture of the kidney graft. Because of the trauma a preexistent chronic lymphocele got clinically manifest. The histology of the lymphocele wall shows fatty and collagen tissue with a strong fibrosis. The diagnostic and therapeutic procedure is described. There are different possible relations between the rare problems: — the tight lymphocele carries over the force on the graft — the lymphocele has grown together with the graft at the lower pole and ruptures in this place — a little graft rupture makes a clinical manifest bleeding in the lymphocele because the deficiency of perirenal tissue.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992) 
    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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  • 30
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 1-2 
    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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  • 31
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 3-3 
    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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  • 32
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 5-5 
    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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  • 33
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 7-14 
    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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  • 34
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 43-52 
    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 Heisenberg spin Hamiltonian for a collection of N spin-1/2 sites is viewed, as favored by Professor Matsen, to be an element of the group algebra of the symmetric group SN. Several computationally tractable, variational group-algebraic approximations for the finite-temperature density matrix are made so as to minimize the Gibb's free-energy functional. Relations to previous quite differently motivated approximations are identified, though improvements are noted with the present approach.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 15-42 
    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 define the algebrant, a mathematical generalization of the determinant, the immanant, the permanent, and the Schur functions. Algebrants are classified as multilinear matrix functions or multicomponent symmetrized tensors. In applications, such as N-electron quantum mechanics, where extensive computation is required, it is vital to reduce computational effort, e.g., the well-known N-factorial problem. We derive certain mathematical properties that can be incorporated in efficient computing algorithms for algebrants. Foremost is our “elimination theorem,” which allows (in important special cases) zeros to be introduced into an algebrant in close analogy with Gaussian elimination for determinants. Savings accruing from such elimination can be substantial. We show examples from Matsen's spin-free quantum chemistry where elimination effectively removes the N-factorial problem that has hitherto stifled possible applications.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 53-75 
    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 geometric phase of quantum mechanics is introduced, and its physical effects are then studied in the context of molecular physics. By performing the most general Born-Oppenheimer procedure, we show how gauge groups appear in the study of molecules. This method is then applied to the doubly degenerate Λ-levels of a diatomic molecule. The resulting dynamics for the slow angular motion of the dumbbell is equivalent to that of a Dirac monopole.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 77-88 
    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 use of algebraic methods in molecular structure is briefly reviewed. The fundamental algebra, G ≡ U(4), of rotation-vibration spectra is introduced and its implications on spectra of di-, tri-, and polyatomic molecules are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 147-151 
    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: Explicit expressions for the eigenvalues of the class sums [(p)(1)n-p]n, p = 2, 3,…,14, of the symmetric group Sn are presented. Partial results are given for the eigenvalues corresponding to arbitrary p.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 105-116 
    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 multilevel circulant is defined as a graph whose adjacency matrix has a certain block decomposition into circulant matrices. A general algebraic method for finding the eigenvectors and the eigenvalues of multilevel circulants is given. Several classes of graphs, including regular polyhedra, suns, and cylinders can be analyzed using this scheme.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 40
    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 exposition of spin-spin operator matrix elements is presented in the context of the graphical unitary group approach (GUGA) to atomic and molecular physics and quantum chemistry. A compendium of subgraph types and formulae is given. Aspects of computer implementation within the structure of the Columbus CI programs is discussed.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 117-146 
    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 algorithm is described that enables an implementation of a general valence bond (VB) method using the Clifford algebra unitary group approach (CAUGA). In particular, a convenient scheme for the generation and labeling of classical Rumer-Weyl basis (up to a phase) is formulated, and simple rules are given for the evaluation of matrix elements of unitary group generators, and thus of any spin-independent operator, in this basis. The case of both orthogonal and nonrothogonal atomic orbital bases is considered, so that the proposed algorithm can also be exploited in molecular orbital configuration interaction calculations, if desired, enabling a greater flexibility for N-electron basis-set truncation than is possible with the standard Gel'fand-Tsetlin basis. Finally, an exploitation of this formalism for the VB method, based on semiempirical Pariser-Parr-Pople (PPP)-type Hamiltonian and nonorthogonal overlap-enhanced atomic orbital basis, and its computer implementation, enabling us to carry out arbitrarily truncated or full VB calculations, is described in detail.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 163-185 
    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 statistical state space is discussed in terms of the geometry of normed real vector spaces with particular reference to the novel concept of direction distance. Specialization to the geometry of the measure cone and the correspondingly specialized concept of mixing distance suggest strong mutual relationship as is shown subsequently in physically required generality. Thereby, the phenomenon of irreversibility attains an interpretation that seems to be the canonical mathematical background for classical and nonclassical statistical physics.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 187-211 
    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 freeon tensor product basis provides a rapid method for the evaluation of matrix elements in the unitary group formulation of quantum chemistry. The method employs fast transformations between the Gel'fand and freeon tensor product basis.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 153-162 
    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 configuration interaction (CI) method where the efficiency of the generators of the unitary group is most fully exploited is the internally contracted multireference CI method. In the most recent version of this method the semi-internal configurations were kept uncontracted, which means that the number of configurations can still be quite large. In the present study the necessary formulas are derived for the case where the semi-internal states are also contracted. The highest density matrix that appears in these formulas is of order 5, and the computational treatment of this large matrix is discussed in detail.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 213-242 
    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: Some problems in elementary geometry are approached from the point of view of linear algebra and generalized to the theory of linear spaces of finite or infinite dimensions having a positive definite binary product. The angle ω between two elements of the linear space is defined from the concept of length by means of the cosine-theorem. A rotation is then defined as a special case of a unitary transformation moving all elements the same angle ω, except that under certain circumstances, some elements may stay invariant. In the former case, one speaks of a rotation around an “external axis,” and in the latter case, of a rotation around an “internal axis” defined by the invariant elements. It is shown that the finite rotations U of both types may be expressed in the simple exponential form U = exp(iωm), where the “generator” m in the former case is an operator satisfying the relation m2 = 1, and in the latter case, m3 = m. The structure of the group of finite rotations in the former case is clarified in some detail. As an illustration of the theory, some applications to the three- and two-dimensional spaces as well as to the theory of spin are given. The coupling between the ordinary three-dimensional rotations and the spinor transformations is considered in somewhat greater detail.
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  • 46
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992) 
    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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  • 47
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 243-255 
    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 vertical ionization potentials of model hydrogen chains have been calculated, in the framework of STO-3G and 4-31G bases, at the second-order level of the many-body Green's function theory. Compared to the second-order many-body perturbation theory, this approach provides a qualitative description of trends observed with orbital relaxation, pair removal, and pair relaxation effects when studying oligomeric systems of increasing size with varying bond length.
    Zusätzliches Material: 6 Ill.
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  • 48
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 257-271 
    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 framework of our study of the changes of the electric polarizability upon substituting heteroatomic linkages in conjugated hydrocarbon backbones, we have been led to examine the relative stability of eight compounds isoelectronic to the all-trans octatetraene using the Cox and Pilcher concept of stabilization energy (SE), SE = ΔHa - ΣNABEAB, where ΔHa is the heat of atomization of the species under consideration and the EAB's are bond-energy terms. Full geometry optimizations at the 4-31G level have been performed to obtain the equilibrium geometries needed to deduce reliable semiempirical heats of formation from appropriate isodesmic processes. Some of the compounds containing the — CH=N— and — N=N — groups have electric polarizabilities and stabilization energies comparable to octatetrene.
    Zusätzliches Material: 1 Ill.
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  • 49
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 281-292 
    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 effects of the basis-set size on many-body energy expansion in Linn+F- clusters are investigated and correlated with previously reported values on Linn+Cl- analogs. Coulomb and non-Coulomb energies in Linn+F- at different configurations are also examined. Although at the minimal STO-3G basis Vna(3, 4) and Vna(4, 4) nonadditivity terms were the smallest in the D3h configuration, they were the largest at the extended 6-311 ++G basis. V(m, n) terms where m = n ≥ 3 were found to be playing a small role in the chemistry and physics of Linn+F- clusters compared with V(3, n) terms in Linn+Cl- clusters.
    Zusätzliches Material: 6 Tab.
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  • 50
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 273-279 
    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: Even in a finite-size system, the vibronic interaction acts as the attractive force to bind a pair of electrons. For small-size systems, the electron repulsion overwhelms the vibronic attraction. As the size of the system becomes large, the electronic repulsion diminishes to zero in proportion to the volume of the system, whereas the vibronic attraction (1) grows to infinity for a one-dimensional system, (2) converges to a finite value for a two-dimensional system, and (3) diminishes to zero for a three-dimensional system. Even for a three-dimensional system, the vibronic attraction diminishes much slower than does the electronic repulsion. This brings about a concept of the critical size for an any-dimensional system, over which size the vibronic attraction overwhelms the electronic repulsion, thereby creating purely attractive interaction for a pair of electrons, which may lead to superconductivity.
    Zusätzliches Material: 1 Ill.
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  • 51
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 327-337 
    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 analysis of the quality of a given basis set is presented in terms of the three fundamental parts of total energy. This analysis clearly displays three types of error occasionally present in the components of total energy. As an illustration of the application of these concepts, several STO and Gaussian basis sets for the Ni atom are analyzed.
    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 41 (1992), S. 293-310 
    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 electrode potential of 2,3-dicyanobenzoquinone in aqueous solution has been calculated relative to parabenzoquinone using a thermodynamic cycle approach that includes accurate gasphase ab initio calculations and calculation of differences in free energies of hydration using the free-energy perturbation method. The discrepancy between the calculated and experimental electrode potential is disappointingly large (99 mV) compared to previous studies using this approach. This, along with the experimental evidence, suggests that the experimental value itself is too large and that theoretical approaches may indeed be as reliable as experimental ones for determining redox properties of molecules such as 2,3-dicyanobenzoquinone. In the light of this discrepancy we have examined the variation of the results with the basis set, inclusion of electron correlation and changes in the parameters used in the molecular dynamics free-energy simulations. The results are shown to be dependent upon the torsional parameters and especially dependent upon the basis set or semiempirical method used to obtain the electrostatic potential-derived charges. The best charge set was determined using the ab initio criteria of completeness - as far as it can be applied to large molecules - and also by studying the effect of hydration on these charges. This was done by allowing the solvent to perturb the wave function prior to the electrostatic potential determination. Thus, 3-21G and 6-31G* basis sets were found to give satisfactory results. Similar results were obtained using semiempirical and ab initio geometries.
    Zusätzliches Material: 2 Ill.
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  • 53
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 311-325 
    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 derived the necessary conditions to which the vector coupling coefficients (VCC) amn(u) and bmn(u) describing atomic L,S-multiplets of the configurations dN (1 ≤ N ≤ 9), should satisfy. Special attention is paid to the states of non-Roothaan type for which VCC depend on the choice of degenerate d-orbitals basis set determined within the accuracy up to an orthogonal transformation u. It is shown that for such states the direct sum of matrices ‖amn(u)‖ and ‖bmn(u)‖ must be the non-symmetric matrix. Obtained VCC were used for the ab initio calculations (basis set (14s9p5d)/[8s4p2d] from [15]) on first-row transition atoms (from Sc to Cu) to compare to similar calculations [16], in which the Peterson's VCC have been used, and with calculations [15] carried out by the atomic SCF program [4] as well.
    Zusätzliches Material: 4 Tab.
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  • 54
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 339-357 
    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 modified and extended version of the Neumann expansion of the interrelectronic distance function riju for u = -1, 0, 1, 2, using the set of orthogonal polynomials normalized to unity, is presented. This expansion has been utilized to obtain analytical expressions for evaluating two-center two- and three-electron integrals in the Slater orbital basis occurring if variational correlated functions are used.
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  • 55
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 383-384 
    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
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 371-379 
    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 adiabatic reaction path for hydrogen abstraction from methane by methyl is computed by quantum chemical methods and then symmetrized by properly defining the reaction coordinate. The theoretical barriers are then fitted with the barriers defined by the parabolic and Eckart functions. Rate constants for the hydrogen and deuterium-abstraction processes via tunneling at low temperatures are then computed.
    Zusätzliches Material: 4 Ill.
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  • 57
    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: This article is concerned with the construction of the general algorithm for evaluating two-center, two- and three-electron integrals occurring in matrix elements of one-electron operators in the basis of variational correlated functions. This problem has been solved here in prolate spherical coordinates, using the modified and extended form of the Neumann expansion of the interelectronic distance function rkij derived in Part I of this series for k = -1, 0, 1, 2. This work expands the method proposed by one of us in the preceding paper for integrals of the types mentioned above. The results of numerical calculations for different types of the two- and three-electron integrals are presented. The problem of convergence of the proposed procedures used is also discussed.
    Zusätzliches Material: 5 Tab.
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  • 58
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 381-382 
    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
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 385-385 
    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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  • 60
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992) 
    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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  • 61
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 387-397 
    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 review a formalism introduced by Fix and Heiberger in 1972 for solving the generalized (or nonorthogonal) eigenvalue problem for ill-conditioned symmetric matrices and we discuss its application in quantum chemistry. A few examples dealing with the calculation of high Rydberg orbitals are presented.
    Zusätzliches Material: 3 Tab.
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  • 62
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 421-435 
    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 recently developed inclusion of the spin-orbit interaction into the quasi-relativistic version of the MSXα method has been applied to the ThX4:Pa4+ (X ≡ Cl, Br) doped system. A new interpretation of the optical spectrum is given.
    Zusätzliches Material: 4 Ill.
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  • 63
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 413-419 
    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 MRD-CI calculations using a basis set of near Hartree-Fock quality have been carried out to calculate the ground-state electronic structure of S2N+, S2N, and S2N- and the ionization potential, electron affinity, and vertical electronic spectrum of S2N. At the highest level of theory (estimated full CI or FCI), S2N+ is predicted to have a linear structure with r(N—S) = 1.51 Å. For S2N and S2N-, the minimum in energy at the FCI level corresponds to a quasi-linear [with a barrier height to linearity of about 2.0 kcal mol-1, ] and a bent structure , respectively. The adiabatic/vertical ionization potential and electron affinity of S2N are predicted to be 7.26/7.82 and 1.60/0.79 eV, respectively. Of the several electronic transitions in S2N considered, the ones with the excitation energy of 1.87 eV (X2 A1 → 2B2) and 2.87 eV (X2A1 → 2B2) are somewhat intense (ƒ = 0.005 and 0.002) and likely to be observed.
    Zusätzliches Material: 1 Ill.
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  • 64
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 489-496 
    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: Using simple physical arguments, a local spin-polarized exchange potential, Vxσ, is constructed from the single-particle Hartree-Fock (HF) potentials (generalized Slater method) that reduces to the usual Kohn-Sham (KS) result in the uniform gas limit. Numerical results for 10 closed subshell atoms demonstrate that the total energy calculated employing this Vxσ is closer to the exact KS results than those of other standard exchange approximations with electron densities and highest occupied orbital eigenvalues that closely approximate the HF results.
    Zusätzliches Material: 3 Ill.
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  • 65
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 475-488 
    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 vibronic interaction in an (A)2N chain (e.g., polyacetylene) has been studied within the Hückel framework. A Hückel framework scheme for calculating the parameters of molecular dynamic structure, i.e., the linear and quadratic orbital vibronic constants (OVCs), has been presented. Selection rules for the OVCs in this scheme have been obtained and discussed by using graph theory and group theory, under various boundary conditions. A Hückel noncoupling rule has been concluded and discussed. The dimerization of polyacetylene has then been discussed based on the molecular dynamic structure. It has been shown that for a finite undoped (A)2N chain the occupied orbital energy εn at the unified configuration has a negative slope in direction of Q2n. As a result, there exists a net Hellmann-Feynman force leading to dimerization. When the chain length goes to infinity, the slopes and forces tend to zero. However, a significant negative curvature in potential surface may occur in the direction of Q2n, due to the two-phonon coupling of the π-electrons, which could also induce the dimerization. These can be interpreted as the results of the hidden C4N+2 symmetry and the imaginary degeneracy in an (A)2N chain, according to the graph theory for molecular orbitals. Thus, the dimerization of an (A)2N chain actually destroys its hidden symmetry of C4N+2 and reduces its imaginary degeneracy.
    Zusätzliches Material: 5 Ill.
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  • 66
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 497-516 
    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: Recently, some cyclopenta-fused polyaromatic hydrocarbons, an environmentally relevant subclass of chemicals, have been shown to have carcinogenic activity in animals. It has been suggested that benz[l] aceanthrylene (I), an active member of this subclass with a gulf region, has a trans dihydrodiol metabolite that is nonplanar and has two distinct spatial configurations. We have used MMP2(85) and AM1 to investigate the three-dimensional structure of this dihydrodiol and other similar derivatives of (I) and have found that although (I) is somewhat nonplanar the relevant derivatives are all nearly planar. Further, we have computed potential functions for the bending of the angular ring in the gulf region using MMP2(85), AM1, and ab initio computed energies for AM1 spatial configurations and find that these molecules all have only a single potential minimum. We have performed the same calculations for benzo[c]phenanthren and its 1,12 dimethyl derivative, molecules with a similar gulf region for which crystallographic data exists. In agreement with that data, we find that two distinct spatial configurations exist separated by significant barries. The differences between the results generated by the three different methods of computation will be discussed.
    Zusätzliches Material: 8 Ill.
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  • 67
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 517-524 
    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 density of states is calculated for a random distribution of donor-pairs of hydrogenlike impurities in three- and two-dimensional systems. Recent investigations of the hydrogen molecule in the alternant-molecular-orbital approximation are here extended. We found that the lowest excited state 1Σu (i.e., H+H-), which is optically connected to the ground state, plays a relevant role in the absorption spectra of semiconductor systems.
    Zusätzliches Material: 8 Ill.
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992) 
    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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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 525-525 
    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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  • 70
    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 regional density-functional theory is formulated and applied to the study of ground-state electron redistributions during the course of a chemical reaction. If for a given increment of the reaction process, accumulation of electrons occurs in a certain region of space, then it is called the dynamic acceptor region, denoted by P. The complement is called the dynamic donor region, denoted by Q. The regional energy itself is determined as a unique functional of the electron density of the total system. The regional transfer potentials are defined in such a way that they add to give the total chemical potential, and their values along the reaction coordinate are found to be different between P and Q. The difference between the regional transfer potentials is shown to provide the driving force for electron transfer from Q to P. A characteristic coordinate for following electron transfer and an associated excitation potential are introduced. The excitation potential is a measure of regional virtual excitation due to regional interactions. The regional transfer potential gives the local character of electron transferability, while the excitation potential gives the global character. The theory encompasses the concepts of regional hardness and softness and sheds light on the HSAB principle.
    Zusätzliches Material: 4 Ill.
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 557-579 
    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: Potential energy surfaces can be classified into combinatiorial equivalence classes, based on their partitioning into catchment regions. Two classification theorems are proven: one for reaction spheres and another for reaction tori. A method for constructing all possible equivalence classes of reaction spheres and reaction tori is presented. As illustration of the general results, it is shown that not all the two-dimensional reaction spheres are combinatorially equivalent to polyhedra in the three-dimensional Euclidean space. As examples, several reaction spheres are calculated by using the RHF method at the 3-21G* level, describing the interactions between a series of polyatomic ions and H+. The calculations show that the potential energy surface of the CO32- …H+ interaction, combinatorially equivalent to that of the NO-3 …H+ interaction, is not combinatorially equivalent to any polyhedron in 3-space; however, the combinatorially different potential energy surface of the PO43- … H+ interaction is equivalent to a polyhedron in 3-space. The topological classification scheme is proposed for the study of similarities between various families of chemical reactions.
    Zusätzliches Material: 10 Ill.
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  • 72
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 581-590 
    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 requirements of variational freedom of electron group functions and their spatial separation are basic statements of the group functions method as they are necessary for taking into account the intragroup electron correlation while neglecting the intergroup one. But these requirements seem to be inconsistent with one another. This contradiction can be removed using the notion of antisymmetrical annulment of many-electron functions introduced in the present work. The transformation of group functions (GF) by means of functions antisymmetrically annulling (ASA) other GF's is proposed that does not affect the whole system's wave function but can be used for localizing GF's. The problem of construction of a function \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \Phi $\end{document} ASA a given Φ can be reduced to solving a system of linear algebraic equations. A sufficient condition of existing of nontrivial \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \Phi $\end{document} is obtained.
    Zusätzliches Material: 1 Tab.
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 591-598 
    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 addition reactions between HO2 and propene leading to the radical intermediates CH3CHCH2OOH and CH3CHOHCH2 have been studied by ab initio molecular orbital calculations using a 6-31G* basis set and including electron correlation through fourth-order Møller-Plesset calculations. The intermediates are predicted to have energies of about 5 kcal/mol below the total reactant energies, the complex resulting from the HO2 attack on the central carbon of propene being slightly preferred. The activation energies for the addition to the terminal carbon and the central carbon are predicted to be 8.5 and 8.0 kcal/mol, respectively, at the highest level of calculation [MP4(SDTQ)] with corrections for spin contamination. Spin contamination corrections are found to be very important in the calculation of these values. Referring to previous calculations at the same level for the addition of HO2 to ethylene [12], we assume that the addition step is the rate-determining one in the reaction leading to HO and propene oxide. The observed activation energy for this reaction, 14.2 kcal/mol [2], is significantly higher than the predicted one for the addition step. The discrepancy found, 6.2 kcal/mol, is virtually the same as the one encountered in the ethylene case, 6.6 kcal/mol [12]. The barrier to intramolecular hydrogen migration leading to the intermediate radical CH2CH2CH2OOH is found to be 42.6 kcal/mol at the highest level of calculation. Spin contaminiation corrections are not important for this energy.
    Zusätzliches Material: 1 Ill.
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 599-611 
    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 electronic influence of the matrix on several adsorption sites of the CO/Ni—Cu(110) system has been studied using a semiempirical molecular orbital calculation. A negative ligand effect of a copper matrix on monometallic nickel sites and a less important ligand effect of a nickel matrix on copper sites have been found and explained in base on the electronic structure. Bridge nickel-copper sites show an intermediate negative ligand effect within a Cu matrix. The results of the theoretical calculation are compared with the available experimental data.
    Zusätzliches Material: 5 Ill.
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  • 75
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992) 
    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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  • 76
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 613-635 
    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 further step is made in investigating the zero-point vibrational energies En (or the total pielectron energies En for the case of alternant hydrocarbons) of lineraly extended system B—An—B′ having n repeating identical moieties. By an approach using the aspects of form and general topology, an integral representation αint of a fundamental functional α, where α(ϕ) = limn→∞ (En(ϕ)/n), has been established, which enables one to treat these energies quantitatively in a unified manner.
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  • 77
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 637-651 
    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: Experimental and computational results from the study of positive and negative ions in solution are presented. The importance of short-range interactions between ion and solvent is studied with regard to core ionization of the ion. Exchange repulsion is found to be a significant factor in the interpretation of data for both cations and anions. Experimental results are presented for the core ionization of the OH- ion in solution. The data show a strong similarity with corresponding data for the F- ion, resulting in a large negative solvation energy for the final core hole state. The Be2+ ion shows large solvation energies for both ground- and core-ionized states, which is interpreted as due to charge transfer effects between solvent and ion.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 667-672 
    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 an empirically established fact that the total π-electron energy (E) of benzenoid hydrocarbons is a linear function of the number of Kekulé structures (K). A general class of approximate formulas for E is shown to exhibit the required linear dependency on K. The condition for this is that the highest occupied molecular orbitals (MOS) are nondegenerate and well separated from the second highest occupied MOS.
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  • 79
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 673-686 
    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 Sturmian basis set is a set of solutions to the Schrödinger equation, with the potential scaled in such a way that all the members of the set correspond to the same value of the energy. We discuss, in particular, the set of Sturmian basis functions corresponding to solutions of the d-dimensional hydrogenlike wave equation. These hydrogenlike Sturmian functions are expressed in terms of Laguerre polynomials and hyperspherical harmonics. When they are used as a basis for solving the many-particle Schrödinger equation, the secular equations take on a simple form [Eq. (59)]. The necessary integrals are evaluated explicitly, and the possibility of combining the hyperspherical technique with dimensional scaling is discussed.
    Zusätzliches Material: 1 Ill.
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  • 80
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 653-665 
    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 concepts of normalized irreducible tensorial matrices (NITM) are extended to all finite and compact unitary groups by a development that clarifies their relationship to group theory and matrix algebra. NITM for a unitary group G are shown to be elements of a basis obtained by symmetry adapting to G the matrix basis of a matrix space M(α1 × α2). Elements [X]α1α2 ∊ M(α1 α2) transform under Ga ∊ G according to [Ga]α1 [X]α1α2[G-1a]α2, where [Ga]α1 and [G-1a]α2 belong to irreducible representations of G. The usual properties of NITM and the Wigner-Eckart theorem follow from these results, which are valid for both finite and compact unitary groups. The NITM span M(α1 × α2) are orthonormal under the trace and transform irreducibly with respect to G. This NITM basis of M(α1 × α2) is said to be simple. A compound NITM basis of a matrix space results when the space is partitioned into two or more subspaces, each spanned by a simple NITM basis. NITM determined from Griffith's V coefficients for the octahedral group are tabulated and used to construct a six-coordinate superposition Hamiltonian.
    Zusätzliches Material: 2 Tab.
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  • 81
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 687-694 
    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 recently introduced concept of charge and valence for ab initio wave functions is applied to molecules with second-row elements. Mulliken and Löwdin charges and their valence counterparts by Mayer and Gopinathan-Jug are calculated for selected molecules with 4-31G and 6-31G* wave functions and compared with results derived from the new valence concept. It is concluded that the term hypervalence can be reasonalby used in phosphorus compounds PF5 and PCl5 and sulfur compounds SO3 and SF6.
    Zusätzliches Material: 2 Tab.
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  • 82
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 695-708 
    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 problem of the reduction of some strong correlated electron models to spin models is considered. Effective spin Hamiltonians for Hubbard and Emery modles with a strong repulsive potential are obtained.
    Zusätzliches Material: 8 Ill.
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  • 83
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 719-727 
    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 new expansion for r-212 expressed in terms of Legendre polynomials is given. The explicit expression is \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{1}{{r_{12}^2 }} = \sum\limits_{i = 0}^\infty {\left[{\ln \left| {\frac{{r_{1\,} + \,r_2 }}{{r_1 - r_2 }}} \right|\sum\limits_{k = 0}^l {C'_{l,k} r_1 ^{l - 2k - 1} } r_2 ^{ - l + 2k - 1} - \sum\limits_{k = 0}^{l - 1} {C_{l,k} } r_1^{l - 2k - 2} r_2 ^{ - l + 2k} } \right]} \,P_l ({\rm cos }\vartheta _{{\rm 12}}) $$\end{document}. For the coefficients C′l,k and Cl,k numerically stable formulas are derived.
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  • 84
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 709-718 
    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: Conformational preferences of N6-furfurylamino purine (kinetin) and N6-benzyl amino purine (BAP) have been investigated theoretically by the quantum chemical perturbative configuration interaction using localized orbitals method. The predicted most stable conformations for these molecules are quite similar. The N6 substituents in both these molecules are oriented toward N(1) and away from the imidazole moiety of the purine. The furfuryl ring in kinetin as well as the aromatic benzene ring in BAP are not coplanar with the purine ring. Comparison of these results with the preferred conformation of another compound N6-(Δ2-isopentenyl) adenine reveals striking similarity in the orientations of the N6 substituents in these cytokinin-active plant-growth-stimulating substances.
    Zusätzliches Material: 8 Ill.
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  • 85
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 729-731 
    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: The second-order Rayleigh-Schrödinger energy correction to the Born-Oppenheimer potential energy due to the spin-orbit interaction can be expressed as a linear response function evaluated at zero frequency. We have calculated this energy contribution to the Cr2 singlet ground state X1 Σ+g potential energy function for a multiconfiguration self-consistent field (MCSCF) wave function. The calculations show that the effect of spin-orbit interaction is small and of the same magnitude for the whole potential energy curve.
    Zusätzliches Material: 1 Tab.
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  • 86
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 733-747 
    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: Hartree-Fock-Roothaan studies are reported for low-lying electronic states of metallic beryllium as modeled by a moiety of 135 beryllium atoms. The system corresponds to 16 coordination shells of a central Be with internuclear separations derived from the lattice constants of the bulk metal. The calculations become tractable by use of the full D3h symmetry of the system at both the integrals and self-consistent-field stages and by employing ab initio effective potentials for the 1s electrons of each beryllium atom. Ionization potentials, binding energies, orbital energies, electric field gradients, nuclear-electrostatic potentials, diamagnetic shielding constants, second moments, and Mulliken populations are calculated for selected electronic states. The calculated ionization potential for the lowest state agrees to within 10% of the experimental bulk work function. A density-of-states analysis for that state is reported and compared with band structure calculations.
    Zusätzliches Material: 5 Ill.
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  • 87
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 755-757 
    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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  • 88
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 749-754 
    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 commercial computer algebra program, Mathematica, is used to generate the C matrix that characterizes our implementation of the Löwdin α-function method as applied to Slater-type orbitals. An example of a two-center overlap integral is done to show how the arbitrary precision capability of Mathematica can overcome severe cancellation errors encountered with programming in FORTRAN. This strategy is capable of being generalized to other multicenter molecular integrals. Mathematica programs are included.
    Zusätzliches Material: 3 Tab.
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  • 89
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992) 
    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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  • 90
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 759-761 
    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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  • 91
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 763-771 
    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 application of the Prüfer transformation to the Schrödinger equation leads to a nonlinear first-order differential equation. The advantage of this transformation is demonstrated in the calculation of the energy spectrum of the H2+ ion. In the second section, the classical problem is recalled and the transition to Prüfer transformation prepared. The definition of this transformations is contained in the third section. In the final paragraphs, the numerical results concerning the eigenvalues of H2+ energy are presented.
    Zusätzliches Material: 2 Ill.
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  • 92
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 773-783 
    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 demonstrated that the maximum overlap symmetry molecular orbital method can be used for optimization of molecular geometries and calculation of vibrational frequencies by adding a two-body repulsive energy term and a modification of the Wolfsberg-Helmholz formula. The obtained equilibrium geometries and vibrational frequencies are on the whole in good accordance with experimental data, which shows that the basic idea using the method to optimize molecular geometries and to calculate vibrational frequencies is reasonable.
    Zusätzliches Material: 3 Tab.
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  • 93
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 785-792 
    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: Second-order multiconfigurational self-consistent field (MCSCF) calculation has been programmed on the basis of CNDO/INDO molecular orbital bases, in which the configuration space employed is restricted within pair-excitations. Test calculations have been carried out for 17 small molecules. All the MCSCF ground states of these molecules have been successfully converged to their respective optimal states by employing a simple weighting scheme. This procedure provides a great savings in computer time. The MCSCF calculation on azetidine required only 27 min on a HITAC M-680H. The MCSCF energies of HF, F2, and BH show improved behaviors up to large atomic distances (∼7au).
    Zusätzliches Material: 1 Ill.
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  • 94
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 793-810 
    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 ab initio electronic structure study is presented of hydrogen-hydrogen interactions in an electronic environment perturbed by the presence of palladium atom clusters. In particular, we investigated changes in the interatomic potential when the atomic centers are trapped inside an fcc palladium octahedral hole and when they are separated from each other by a (111) plane of palladium atoms. The (111) plane was modeled with a cluster of three palladium atoms. Self-consistent field (SCF) level calculations were performed, and palladium atom pseudopotentials were employed to make the systems studied computationally tractable. For pairs of atoms placed within the octahedral hole, various lines of approach were considered [along the (100), (110), and (111) directions]. Lattice deformations and electronic excitations were examined for their effect on the interatomic potential.
    Zusätzliches Material: 13 Ill.
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  • 95
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 437-437 
    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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  • 96
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992) 
    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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  • 97
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 463-479 
    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: Dipole moments and static dipole polarizabilities have been calculated for a number of small molecules using the linear combination of Gaussian-type orbitals-local spin density method. The effect of augmenting standard orbital basis sets with polarization functions has been investigated. A set of optimum ζd, for use in calculating polarizabilities, has been derived for the first-row atoms C, N, O, and F. The results of this optimized doubly polarized double-zeta basis set compare well with results obtained using a double-zeta basis set augmented by four even-tempered ζd polarization functions. The results of the optimized basis set, and a basis set augmented with only a single ζd polarization function derived from it, compare very favorably with those obtained from Møller-Plesset perturbation theory and with experimental data. They show a marked improvement on results obtained using standard Hartree-Fock self-consistent-field molecular orbital methods where no treatment of electron-correlation is included.
    Zusätzliches Material: 2 Ill.
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  • 98
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 481-510 
    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 Woodward-Hoffmann (WH) Rules for the prediction of relative rates and stereochemistry of concerted reactions are based on considerations of the orbital symmetry of the reactants and products. Literally hundreds of reactions have been successfully categorized by these remarkably simple-appearing Rules. This paper develops a one-dimensional band model of these Rules. By explicit inclusion of the effects of an electromagnetic field in a standard gauge-invariant fashion, it can be shown that at certain levels of field strength the model suggests that the Rules may be reversed. This is because the Rules appear in the model as a consequence of a centrifugal angular momentum barrier that can be shifted by an electromagnetic field. This barrier could account for “aromatic” stabilization. As an additional effect, the model predicts flux-dependent oscillations and persistent currents for “aromatic” molecules due to the Aharonov-Bohm effect. The possible health effects of electromagnetic fields are speculated. The likelihood of experimental observations to verify the applicability of the model is discussed.
    Zusätzliches Material: 13 Ill.
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  • 99
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 567-572 
    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: A local model for the following reaction path is suggested. Exploratory calculations on simple isomerization reactions are undertaken. A local version of Hammond's postulate is proposed and tested on some model systems.
    Zusätzliches Material: 2 Ill.
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  • 100
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 42 (1992), S. 217-239 
    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 two main problems in applying common methods for electron correlation to large systems are (1) the steep dependency of the computational task with the size of the system and (2) the large and often prohibitive number of two-electron integrals that must be stored and retrieved during the calculation. The direct local correlation method eliminates both these problems. This method is a combination of the local correlation method that eliminates the steep computational dependency with the size of the system and extension of the direct SCF approach to electron correlation methods. The latter method eliminates external storage of the electron repulsion integrals. In this review, the direct local correlation approach and its computer implementation will be described in detail, including computational examples and comparisons to similar methods developed in other groups. The feasibility of future applications to extended systems is discussed.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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