| 1. |
- Shev, S, et al.
(författare)
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Second-generation hepatitis C Elisa antibody tests confirmed by the four-antigen recombinant immunoblot assay correlate well with hepatitis C viremia and chronic liver disease in Swedish blood donors
- 1993
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Ingår i: Vox Sanguinis. - 1423-0410. ; 65:1, s. 32-37
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Tidskriftsartikel (refereegranskat)abstract
- Seventy-three Swedish blood donors (52 men, 21 women; median age 36 years) repeatedly reactive for hepatitis C antibodies (anti-HCV C-100-3) were tested with a second-generation (2nd-gen) anti-HCV Elisa and a 4-band recombinant immunoblot assay (RIBA 2). These results were correlated to serum alanine aminotransferase (S-ALAT), liver morphology and viremia as detected by 'nested' polymerase chain reaction (PCR) based on primers from a 5'-noncoding sequence of the HCV genome. Thirty-five of 46 (76%) donors with positive 2nd-gen Elisa tests confirmed by RIBA 2 were PCR positive whereof 27 had histological findings compatible with chronic persistent hepatitis (CPH) and 7 had chronic active hepatitis (CAH). Ten of 56 (18%) 2nd-gen Elisa-positive donors were RIBA 2 negative (or indeterminate) and none of these had chronic hepatitis nor were PCR positive. Seventeen of 73 (23%) donors were 1st-gen Elisa positive but 2nd-gen Elisa negative. All of these were PCR negative and only 1 (6%) had chronic hepatitis (CPH). An elevated S-ALAT level (reference < 0.7 mu kat/l) was found in 26 2nd-gen Elisa and RIBA 2-positive donors of which 18 had CPH and 7 had CAH and all 25 were PCR positive. A normal S-ALAT level was found in 9 of 34 (26%) donors with chronic hepatitis (all had CPH) and positive PCR. We have found that blood donors with positive 2nd-gen anti-HCV Elisa tests confirmed by RIBA-2 and especially with a concomitant elevated S-ALAT are highly likely to be viremic as demonstrated by PCR and to have chronic hepatitis.
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| 2. |
- Barnes, Leslie A, et al.
(författare)
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Bond length, dipole moment, and harmonic frequency of CO
- 1993
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 98:5, s. 3972-3977
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Tidskriftsartikel (refereegranskat)abstract
- A detailed comparison of some properties of CO is given, at the modified coupled-pair functional, single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory (including a perturbational estimate for connected triple excitations), using a variety of basis sets. With very large one-particle basis sets, the CCSD(T) method gives excellent results for the bond distance, dipole moment, and harmonic frequency of CO. In a [6s 5p 4d 3f 2g 1h] + (1s 1p 1d) basis set, the bond distance is about 0.005a0 too large, the dipole moment about 0.005 a.u. too small, and the frequency about 6 cm-1 too small, when compared with experimental results.
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| 3. |
- Barnes, Leslie A, et al.
(författare)
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Structure and energetics of Cr(CO)6 and Cr(CO)5
- 1993
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 98:5, s. 3978-3989
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Tidskriftsartikel (refereegranskat)abstract
- The geometric structure of Cr(CO)6 is optimized at the modified coupled-pair functional (MCPF), single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory (including a perturbational estimate for connected triple excitations), and the force constants for the totally symmetric representation are determined. The geometry of Cr(CO)5 is partially optimized at the MCPF, CCSD, and CCSD(T) levels of theory. Comparison with experimental data shows that the CCSD(T) method gives the best results for the structures and force constants, and that remaining errors are probably due to deficiencies in the one-particle basis sets used for CO. The total binding energies of Cr(CO)6 and Cr(CO)5 are also determined at the MCPF, CCSD, and CCSD(T) levels of theory. The CCSD(T) method gives a much larger total binding energy than either the MCPF or CCSD methods. An analysis of the basis set superposition error (BSSE) at the MCPF level of treatment points out limitations in the one-particle basis used here and in a previous study. Calculations using larger basis sets reduce the BSSE, but the total binding energy of Cr(CO)6 is Still Significantly smaller than the experimental value, although the first CO bond dissociation energy of Cr(CO)6 is well described. An investigation of 3s3p correlation reveals only a small effect. In the largest basis set, the total CO binding energy of Cr(CO)6 is estimated to be 140 kcal/mol at the CCSD(T) level of theory, or about 86% of the experimental value. The remaining discrepancy between the experimental and theoretical value is probably due to limitations in the one-particle basis, rather than limitations in the correlation treatment. In particular, an additional d function and an f function on each C and 0 are needed to obtain quantitative results. This is underscored by the fact that even using a very large primitive set (1042 primitive functions contracted to 300 basis functions), the superposition error for the total binding energy of Cr(CO)6 is 22 kcal/mol at the MCPF level of treatment.
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| 4. |
- Barnes, Leslie A, et al.
(författare)
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Symmetry breaking in O+4 : an application of the Brueckner coupled-cluster method
- 1994
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 223:3, s. 207-214
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Tidskriftsartikel (refereegranskat)abstract
- A recent calculation of the antisymmetric stretch frequency for the rectangular structure of quartet O4+ using the QCISD(T) method gave a value of 3710 cin-1. This anomalous frequency is shown to be a consequence of symmetry-breaking effects, which occur even though the QCISD(T) solution derived from a delocalized SCF reference function lies energetically well below the two localized (symmetry-broken) solutions at the equilibrium geometry. The symmetry breaking is almost eliminated at the CCSD level of theory, but the small remaining symmetry-breaking effects are magnified at the CCSD (T) level of theory so that the antisymmetric stretch frequency is still significantly in error. The Brueckner coupled-cluster method, however, leads to a symmetrical solution which is free of symmetry-breaking effects, with an antisymmetric stretch frequency of 1322 cm-1, in good agreement with our earlier calculations using the CASSCF/CASSI method.
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| 5. |
- Lindh, Christian, et al.
(författare)
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Method for analysis of methyltetrahydrophthalic acid in urine using gas chromatography and selected ion monitoring
- 1994
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Ingår i: Journal of chromatography. B, Biomedical applications. - : Elsevier BV. - 1572-6495 .- 0378-4347. ; 660:1, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- A method for the determination of methyltetrahydrophthalic acid (MTHP acid), a metabolite of methyltetrahydrophthalic anhydride (MTHPA) in human urine, was developed. The investigated MTHP acid was obtained by hydrolysis of a commercial MTHPA mixture, composed of three major isomers. These were synthesized and identified as 3-methyl-delta 4-tetrahydrophthalic anhydride, 4-methyl-delta 4-tetrahydrophthalic anhydride and 4-methyl-delta 3-tetrahydrophthalic anhydride. The urine was worked up by a liquid-solid extraction technique using C18 sorbent columns. Esterification was performed with methanol and boron trifluoride. The derivative in toluene was analyzed with capillary gas chromatography and selected ion monitoring. Deuterium-labeled MTHP acid was used as internal standard. The intra-assay precision for the overall method was between 4 and 8% in the range 3-110 ng/ml and the inter-assay precision was between 4 and 7% in the range 30-110 ng/ml. The total recoveries of the MTHP acid at 19 and 190 ng/ml were 94 and 97%, respectively. The total detection limit for the three isomers was < 6 ng/ml. Analysis of urine from a worker exposed to MTHPA makes it reasonable to assume that the method may be used for biological monitoring of MTHPA exposure.
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| 6. |
- Lindh, Roland, 1958-, et al.
(författare)
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The fraternal twins of quartet O+4
- 1994
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 100:1, s. 224-237
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Tidskriftsartikel (refereegranskat)abstract
- Eleven stationary geometries of quartet O4+ have been studied by ab initio methods. The geometries were optimized at the complete active space self-consistent field (CASSCF) level of theory and the energies were calculated by the multiconfigurational second order pertubation method (CASPT2), using double-zeta plus polarization (DZP), triple-zeta plus double polarization (TZ2P), average atomic natural orbital (ANO) [5s4p2d] and average ANO [6s5p3d2f] basis sets. The rectangular and trans-planar structures are found to be the most stable, with an energy barrier to conversion between the two at the threshold of dissociation. Both have a delocalized hole and are stable relative to separated O2 and O2+ by 11.0 and 11. 5 kcal/mol for the rectangular and the trans-planar structure, respectively, compared with the experimentally deduced energy in the range of 9.2 to 10.8 kcal/mol. The adiabatic ionization potentials of O4 and O2 are computed to be 11.67 and 12.21 eV, while experimental values are 11.66 and 12.07 eV, respectively. The vibrational frequencies have been computed for all degrees of freedom at the CASSCF level of theory. Symmetry breaking is found to be a particular problem in the computation of the antisymmetric stretch frequency for the delocalized structures at the CASSCF level of theory. Attempts to rectify these problems using the restricted active space self-consistent field (RASSCF) method leads to additional difficulties, but further analysis yields insight into the symmetry breaking and problems with earlier calculations. Finally, a nonorthogonal configuration interaction (CI) calculation based on the interaction of localized CASSCF wave functions using the complete active space state interation (CASSI) method leads to a balanced treatment of the antisymmetric stretch which is free from symmetry breaking. The study explains the four most prominent absorption frequencies observed in the partially unassigned IR spectrum of 04+ isolated in solid neon as the antisymmetric OO stretch, and the combination band of the symmetric and antisymmetric OO stretch of both the rectangular and trans-planar structures.
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