Search Results - (Author, Cooperation:L. Steffen)

2018-01-09

The American Association of Immunologists (AAI)

0022-1767

1550-6606

Medicine

2013-08-21

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2011-12-16

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1432-1440

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Es gibt 2 Typen von Lungentuberkulose im höheren Lebensalter: Die Alte Phthise, die im frühen Erwachsenenalter erworben und als geheilte oder stationäre cirrhotische Tuberkulose ins höhere Alter hinübergenommen wird. Die Altersphthise, die erst im höheren Lebensalter entsteht, häufig durch Diabetes ausgelöst wird und prognostisch ungünstiger ist. Zeitlich und nach dem Krankheitsverlauf stehen zwischen diesen beiden Typen die Übergangsfälle.

Electronic Resource

1432-1440

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1430-4171

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electronic Resource

1430-4171

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electronic Resource

1430-4171

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Electronic Resource

1572-9001

MM3 ; PM3 ; MMX ; crystal structure ; norbonadienone ; distorted compound

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract The reaction of 4,5-didehydroacenaphthene with phencyclone yields the title compound, a stable dibenzo-fused norbornadienone (8). The X-ray structure of8 is presented and compared with the structure predicted from a MM3, PM3, and a MMX calculation. Thermal decomposition of 8 produces, 7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (9), a hydrocarbon that is computed to have a significantly twisted polycyclic aromatic skeleton with 19 kcal/mole of strain energy.

Electronic Resource

1573-0743

right ventricular ejection fraction ; radionuclide imaging ; reproducibility ; statistical method of variance components

Springer Online Journal Archives 1860-2000

Medicine

Summary Confidence limits for single and repeat measurements of right ventricular ejection fraction (RVEF) were established by means of a model based on the statistical method of variance components. A total of 80 subjects (age 23 to 74 years) were examined by two radionuclide methods 1) gated first-pass (fp) technique performed in a standard 30° right anterior oblique projection, and 2) multigated equilibrium imaging (muga) in an individual left anterior oblique view, applying with both methods separate end-diastolic and endsystolic ventricular regions of interest. Values obtained by fp technique were clearly higher than those measured by the muga approach, and the correlation between them was only fair: RVEFmuga = 0.48 RVEFfp + 0.13; r = 0.73; SEE = 0.08. The 95% confidence limits for a single measurement were with the fp technique: ‘true’ RVEF = measured RVEF ±6 EF-units compared to ±16 units with the muga method. At repeat determination within an interval of four weeks, the minimal changes in measured RVEF that were statistically significant at the 5% level were with the fp technique ±8 units with the same observer on both occasions and ±9 units with different observers. Corresponding figures with the muga method were ±16 and ±22 units, respectively. The minimal changes in a subject's ‘true’ RVEF necessary to produce a significant change in measured RVEF were with fp technique ±14 units for the same observer and ±17 units for different observers, compared to ±30 and ±41 units with the muga method. In conclusion, the variability with the muga approach was far greater than with the fp technique and the consequent reproducibility so poor as to preclude meaningful measurement of RVEF by the muga method.

Electronic Resource

1572-9001

Cyclopentene-fused PAH ; AM1 ; MMX ; MNDO ; X-ray ; neutron diffraction

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract Several of the readily available theoretical programs are evaluated as tools for modeling the structures of polycyclic aromatic hydrocarbons with five-membered rings (CPAHs). The experimentally determined bond lengths and angles are compared to calculated values. Experimental bond lengths are also compared to Pauling and Huckel molecular orbital (HMO) bond orders. Previously published experimental X-ray and neutron-diffraction structures of acenaphthene, acenaphthylene, fluoranthene, cyclopent[o,p,q,r]benz[c]phenanthrene, and corannulene are modeled by the programs MMX, AM1, MNDO, and PM3, and previously reported STO-3G and 6-31G * data are also evaluated. In general, the error differences between the experimental and calculated results for all of the semiempirical programs were small. However, PM3 performed slightly better than AM1 and MMX, while MNDO generated structures which exhibited the largest deviation from experiment. Although the standard deviations for all programs are shown to be of comparable magnitude, a particular bond length or bond angle in any given theoretical calculation can exhibit significant error from the experimental data. The scatter in the bond order data computed from Huckel molecular orbital theory and valence bond theory is contrary to results obtained with alternant systems. It appears that these approaches are less successful at modeling accurately the nonalternant hydrocarbon systems described in this paper.

Electronic Resource

1573-7470

Causal network ; imprecise probability ; beta distribution ; unsupervised learning

Springer Online Journal Archives 1860-2000

Computer Science

Mathematics

Abstract A causal network is frequently used as a representation for qualitative medical knowledge, in which conditional probability tables on appropriate sets of variables form the quantitative part of the accumulated experience. For probabilities temporarily assumed known, we describe efficient algorithms for propagating the effects of multiple items of evidence around multiply-connected networks and hence providing precise probabilistic revision of beliefs concerning the current patient. As a database accumulates we also require the quantitative aspects of the model to be updated, as well as to learn about the qualitative structure, and we suggest some formal statistical tools for these problems.

Electronic Resource

0894-3230

Electron transfer properties ; substituted flouranthene derivatives ; redox potentials ; Chemistry ; Theoretical, Physical and Computational Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Physics

---The oxidation and reduction potentials of a series of related even non-alternant derivatives of 7,14-disubstituted acenaphth[1,2-k] fluoranthenes, and also fluoranthene, 7,10-diphenylfluoranthene and 8,9-dihydrodiindeno[1,2-j;2′,1′-] fluoranthene, were determined in organic solvents by cyclic voltammetry. The effects of steric hindrance on conjugation of the substituents with the central polycyclic aromatic hydrocarbon nucleus were evaluated. The semi-empirical molecular orbital calculation programs OMEGAMO, Extended Hückel, AM1 and PM3 were used to obtain optimal geometries and calculated HOMO and LUMO energies. As a further refinement, COSMO solvation was included in the AM1 calculations. The redox properties were correlated with data derived from the various semi-empirical calculations and the quality of these correlations is discussed. Inclusion of solvation energies in the computed molecular orbital energies results in a significant improvement in the correlation between observed and calculated oxidation potentials. © 1997 John Wiley & Sons, Ltd.

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Electronic Resource