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- Caidahl, Kenneth, 1949, et al.
(author)
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New concept in echocardiography: harmonic imaging of tissue without use of contrast agent.
- 1998
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In: Lancet (London, England). - : Elsevier BV. - 0140-6736. ; 352:9136, s. 1264-70
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Journal article (peer-reviewed)abstract
- Endocardial border detection is important for echocardiographic assessment of left-ventricular function. Second harmonic imaging of contrast agents enhances this border detection. We discovered that harmonic imaging improves tissue visualisation even before contrast injection. We therefore sought objectively to demonstrate the degree of enhancement of endocardial and myocardial visualisation.An ATL HDI-3000 scanner with software for contrast harmonic imaging was used to record short-axis images of the left ventricle in 27 patients with possible myocardial disease and 22 controls, in the fundamental mode and with harmonic imaging. A computer program measured the relative grey-scale values within six segments of the endocardium and myocardium. An Acuson Sequoia scanner equipped with software for tissue harmonic imaging was used to investigate the reproducibility of ejection-fraction calculations in 22 patients with ischaemic heart disease.Harmonic imaging produced brighter endocardium within each segment. Relative to the mean grey value of the total imaging sector, the values for harmonic and fundamental imaging were 171.5 vs 85.6% (p<0.0001) in end diastole and 194.1 vs 106.7% (p<0.0001) in end systole. Results for the myocardial segments were also significantly better for harmonic imaging. Structure enhancement of similar magnitude was seen among patients and healthy controls. Use of harmonic imaging reduced the proportion of unacceptable images by 14-46% in different views and improved the reproducibility of biplane ejection-fraction measurements.In comparison with fundamental imaging, the relative endocardial and myocardial brightness is enhanced by harmonic imaging.
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- Albinsson, Bo, 1963, et al.
(author)
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Conformers of n-Si5Me12: A comparison of ab initio and molecular mechanics methods
- 1999
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In: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 103:14, s. 2184-2196
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Journal article (peer-reviewed)abstract
- Optimized geometries of the conformers of permethylated linear pentasilane, n-Si5Me12, were calculated by the HF/3-21G*, MM3, MM2, and MM+ methods, which predict eight, nine, six, and six energetically distinct enantiomeric conformer pairs, respectively, at geometries representing various combinations of the anti (similar to 165 degrees), ortho (similar to 90 degrees), and gauche (similar to 55 degrees) SiSiSiSi dihedral angles in the backbone. The results of the MM2 and MM+ methods, based on the same force field, differ insignificantly. The barriers between conformers appear to be exaggerated by the molecular mechanics methods, particularly MM2. Contour maps showing the groundstate energy as a function of the full range of two backbone SiSiSiSi dihedral angles, with all other geometrical variables optimized, computed by each of the methods (only a limited range of angles near the anti,anti geometry in the case of HF/3-21G*) are compared with each other and with analogous results for a model compound, Si4Me10. Conformer interconversion paths are discussed, and two meso transition states for enantiomer interconversion have been located at the HF/3-21G* level of calculation. At the eight HF/3-21G* optimized geometries, single-point energies (HF/6-31G* and MP2/6-31G*) and vibrational frequencies (HF/3-21G*) were computed. The predicted IR and Raman spectra suggest that about half of the expected conformers will be identifiable by vibrational spectroscopy under conditions of matrix isolation. Relative conformer energies calculated by the MM2 and HF methods are similar and favor the anti dihedral angles over gauche and ortho, in agreement with results of solution experiments. Those calculated by the hIM3 and HF methods are similar to each other and favor both anti and gauche dihedral angles nearly equally over ortho, in agreement with indications provided by gas-phase experiments. A rationalization of these solvent effects is proposed. The energies of the conformers of Si4Me10 and Si3Me12 were used to set up a system of additive increments at the MM2, MM3, HF/3-21G*, HF/6-31G*, and MP2/6-31G* levels of calculation, which can be used to predict conformational energies of longer permethylated oligosilanes. An intrinsic energy value is assigned to each of the a, o, and g dihedral angles, and interaction energy values are assigned to each combination of two dihedral angles. The interaction values follow the expected rules in that equal twist sense is favored for adjacent aa, ag, oo, and gg pairs, whereas opposite twist sense is generally favored for adjacent so and go pairs. The MM3-derived set of increments has been tested against results computed for Si6Me14 and found to perform well.
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| 5. |
- Finkelstein, LD, et al.
(author)
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Band approach to the excitation-energy dependence of x-ray fluorescence of TiO2
- 1999
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In: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 60:4, s. 2212-2217
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Journal article (other academic/artistic)abstract
- Excitation-energy dependence of Ti L-2,L-3 soft x-ray emission spectra (XES) of a TiO2 single crystal is measured near Ti 2p threshold using tuneable synchrotron radiation at excitation energies E-exc = 458.2-476.9 eV. It is found that the emission spectr
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| 7. |
- Kurmaev, EZ, et al.
(author)
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Electronic structure of VO2 studied by x-ray photoelectron and x-ray emission spectroscopies
- 1998
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In: JOURNAL OF PHYSICS-CONDENSED MATTER. - : IOP PUBLISHING LTD. - 0953-8984. ; 10:18, s. 4081-4091
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Journal article (other academic/artistic)abstract
- A VO2 single crystal has been the subject of a combined investigation by high-resolution x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy (XES) with both electron and energy-selective x-ray excitation (V L alpha, V K beta(5) and O K alp
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| 8. |
- Lee, Stephanie, et al.
(author)
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Patients' willingness to pay for autologous blood donation
- 1997
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In: Health policy (Amsterdam). - : Elsevier Ireland Ltd. - 1872-6054 .- 0168-8510. ; 40:1, s. 1-12
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Journal article (peer-reviewed)abstract
- Most cost-effectiveness analyses of autologous blood donation show very small health benefits for a substantial increase in resource utilization. However, these analyses do not consider the psychological benefits of peace of mind to patients participating in the program. In order to quantitate these benefits, we employed contingent valuation methodology to measure the willingness of patients undergoing elective surgery, to pay for autologous blood donation. The internal consistency of patient responses was investigated through correlations of willingness-to-pay values with risk perceptions and patient characteristics. Two hundred and thirty-five patients completed the self-administered questionnaire which included demographic, willingness-to-pay and risk perception questions. Median population willingness to pay for autologous blood donation was approximately $900 per patient. In multivariate analysis, willingness to pay varied significantly with dread of allogenic transfusion, perceived risk of requiring a blood transfusion and income. Patients who participate in autologous blood donation programs value the procedure highly and state they are willing to pay significant amounts out of pocket to assure themselves of available autologous blood. Willingness to pay correlated significantly with factors expected to influence value decisions.
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