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  • 1
    ISSN: 1432-086X
    Keywords: Key words: Portal vein, diagnostic imaging—Accessory portal vein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: To present a peculiar anatomic portal veins variant and evaluate its clinical implications. Methods: Among 118 consecutive patients undergoing transjugular intrahepatic portosystemic shunting (TIPS), six male patients were found to have an accessory portal vein, which was seen during direct portography. Results: In all six patients, portograms showed an accessory small-caliber vein parallel to the trunk of the main portal vein ending in the right lobe of the liver. Two of the six accessory portal veins drained blood from coronary veins, precluding access to coronary vein embolization during TIPS. Conclusion: An accessory portal vein is a rare anatomical variation with clinical significance for both surgical shunt placement and TIPS, as well as for transportal embolization of coronary veins.
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  • 2
    ISSN: 1617-4623
    Keywords: Frankia ; Nod ; Nodule ; Complementation ; Mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Clones from aFrankia At4 gene bank were pooled into groups and mass conjugated into anodD mutant ofRhizobium leguminosarum bv.viciae by triparental matings. When peas were inoculated with the pooled transconjugants, nodulation was observed. A plasmid, pAt2GX containingFrankia DNA, was isolated from bacteria recovered from these nodules. This plasmid was shown to complement anodD mutant ofR. leguminosarum bv.viciae. Thus pAt2GX contains aFrankia gene that is functionally equivalent tonodD ofR. leguminosarum bv.viciae.
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  • 3
    ISSN: 1619-7089
    Keywords: 99mTc-labeled t-butylisonitrile (99mTc-TBI) ; Myocardial perfusion imaging ; Coronary artery disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 99mTc-TBI myocardial perfusion imaging has been studied in 7 normal subjects and 24 patients with coronary artery disease. Scintigraphic data revealed that 99mTc-TBI myocardial perfusion imaging is more sensitive than ECG in detecting myocardial infarction. In comparing 99mTc-TBI imaging with contrast angiography, its' sensitivity for the diagnosis of coronary artery disease was 91.7%.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0894-9166
    Keywords: numerical simulating ; crack growth ; moving tip node ; finite element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper deals with the use of finite element for numerically simulating two-dimensional stable crack growth with mode I. A special model called “moving tip node model” is developed for this purpose, in which the node at crack tip is arbitrarily moved within one element's dimension by sequentially relaxing nodal forces thus reducing the discreteness of simulation to the lowest extent and making it closer to the real physical process. A reliable FORTRAN program based upon the incremental theory of plasticity is developed wherein an elastic-plastic finite deformation hybrid finite element is employed. The results obtained for an aluminum center crack plate treated as a linear hardening material are compared with the experimental results provided by [11] and the simulation is shown to be successful on the whole.
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  • 5
    ISSN: 1432-2234
    Keywords: Key words: Free energy simulations ; DPDPE peptide ; Peptide conformational equilibria in solution ; Conformational free energy ; Disulfide bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. We have calculated the free energy differences between four conformers of the linear form of the opioid pentapeptide DPDPE in aqueous solution. The conformers are Cyc, representing the structure adopted by the linear peptide prior to disulfide bond formation, β C and β E , two slightly different β-turns previously identified in unconstrained molecular dynamics simulations, and Ext, an extended structure. Our simulations indicate that β E is the most stable of the studied conformers of linear DPDPE in aqueous solution, with β C , Cyc and Ext having free energies higher by 2.3, 6.3, and 28.2 kcal/mol, respectively. The free energy differences of 4.0 kcal/mol between β C and Cyc, and 6.3 kcal/mol between β E and Cyc, reflect the cost of pre-organizing the linear peptide into a conformation conducive for disulfide bond formation. Such a conformational change is a pre-requisite for the chemical reaction of S–S bond formation to proceed. The relatively low population of the cyclic-like structure agrees qualitatively with observed lower potency and different receptor specificity of the linear form relative to the cyclic peptide, and with previous unconstrained simulation results. Free energy component analysis indicates that the moderate stability difference of 4.0–6.3 kcal/mol between the β-turns and the cyclic-like structure results from cancellation of two large opposing effects. In accord with intuition, the relaxed β-turns have conformational strain 43–45 kcal/mol lower than the Cyc structure. However, the cyclic-like conformer interacts with water about 39 kcal/mol strongly than the open β-turns. Our simulations are the first application of the recently developed multidimensional conformational free energy thermodynamic integration (CFTI) protocol to a solvated system, with fast convergence of the free energy obtained by fixing all flexible dihedrals. Additionally, the availability of the CFTI multidimensional free energy gradient leads to a new decomposition scheme, giving the contribution of each fixed dihedral to the overall free energy change and providing additional insight into the microscopic mechanisms of the studied processes.
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  • 6
    ISSN: 1432-2234
    Keywords: Key words: Ab initio calculation ; Dimerization ; Ketene imine ; Bis(trifluoromethyl)ketene imine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. The dimerization reactions of ketene imine and bis(trifluoromethyl)ketene imine were studied theoretically. All the dimerization processes take place in a concerted but asynchronous manner, each proceeding through a four-membered ring transition state. For the ketene imine dimerization reactions, three different processes have almost equal activation barriers, while for the three bis(trifluoromethyl)ketene imine dimerization processes the reaction giving symmetrical a four-membered heterocyclic product has the lowest activation barrier.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Surveys in geophysics 14 (1993), S. 373-380 
    ISSN: 1573-0956
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Three geopotential models (OSU91A, GEM-T3, and GRIM4-C2), available in 1991, have been compared in several ways. The models have been differenced to find the geoid undulation difference are on the order of 1 m in land areas and 30 cm in ocean areas with extreme differences reaching 6 m. The models were also evaluated, augmented by higher degree terms, when necessary, through comparisons with undulations at Doppler and GPS positioned stations. The undulation difference at the Doppler stations was ± 1.57 m with no significant difference between models. Using 4 GPS test areas, differences were seen between the various models. A final comparison was made between geoid undulations implied by a Geosat 17 day cycle and undulations from the three models. The OSU91A model performed best having a difference standard deviation of ±34 cm.
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  • 8
    ISSN: 1572-8897
    Keywords: relativistic CI ; double group ; correlation group table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A generalized correlation group table (CGT) method is described for the relativistic configuration interaction (RCI) wavefunctions of molecules containing heavy atoms. In this method first four keywords are defined and two properties are discussed in terms of spectroscopic states and double group theory. These definitions and properties are then used to summarize six principles to stipulate the relationship among relativistic states, nonrelativistic states, as well as RCI configurations. The definitions, properties, and principles comprise the generalized CGT method, which facilitates the classification and assignment of the RCI wavefunctions, and thus, provide a general technique for complex systems containing several open shells. Finally, the techniques are exemplified with a few computational models.
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  • 9
    ISSN: 1572-8862
    Keywords: ab initio quantum chemical embedded cluster calculations ; NO and CO adsorption ; platinum surfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The adsorption energetics of NO and CO on Pt(111) are studied using an ab initio embedding theory. The Pt(111) surface is modeled as a three-layer, 28-atom cluster with the Pt atoms fixed at bulk lattice sites. Molecular NO is adsorbed at high symmetry sites on Pt(111), with the fcc threefold site energetically more favorable than the hcp threefold and bridge sites. The calculated adsorption energy at the fcc threefold site is 1.90 eV, with an N-surface distance of 1.23 Å. The NO molecular axis is perpendicular to the Pt(111) surface. Tilting the O atom away from the surface normal destablizes adsorbed NO at all adsorption sites considered. On-top Pt adsorption has been ruled out. The Pt(111) potential surface is very flat for CO adsorption, and the diffusion barriers from hcp to fcc sites are 0.03 eV and less than 0.06 eV across the bridge and the atop sites, respectively. Calculated adsorption energies are 1.67, 1.54, 1.51, and 1.60 eV at the fcc threefold, hcp threefold, bridge, and atop sites, respectively. Calculated C-surface distances are 1.24 Å at the fcc threefold site and 1.83 Å at the atop site. It is concluded that NO and CO adsorption energetics and geometries are different on Pt(111).
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  • 10
    ISSN: 1435-5604
    Keywords: Kew words: newborns ; bone mineral density ; supplementation ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: To study the effects of calcium and vitamin D supplements on bone mineral density (BMD) of perinatal women and their newborns, a follow-up study was performed to examine the BMD of 110 normal pregnant women from mid- to late-term pregnancy to delivery and of their 110 newborns and 30 preterm newborns. BMD was examined using single-photon absorptiometry. In the first experiment, 31 women took a supplement of 0.3 g calcium lactate plus 400 IU vitamin D per day, while 79 received no supplement during their pregnancy. The results showed that the radial BMD of mothers who took calcium lactate during their pregnancy and the tibial BMD of their newborns were significantly higher than those when no supplement of calcium was taken. In the second experiment, it was found that the BMD of preterm newborns was significantly lower than that of normal newborns. This study suggested that advocating pregnancy hygiene, giving a proper dosage of calcium and vitamin D, and improving nutrition during pregnancy can prevent osteoporosis in women and benefit newborn development. It is also shown that a quantitative assessment of BMD might prove useful in the follow-up of newborn and infant development..
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