| 1. |
- Abrahamsson, Erik, 1974, et al.
(författare)
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A new reaction path for the C + NO reaction: dynamics on the 4A'' potential-energy surface.
- 2008
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Ingår i: Physical chemistry chemical physics : PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 10:30, s. 4400-9
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Tidskriftsartikel (refereegranskat)abstract
- We present a new reaction path without significant barriers for the C + NO reaction, forming ground state N((4)S) and CO. Electronic structure (CASPT2) calculations have been performed for the two lowest (4)A'' states of the CNO system. The lowest of these states shows no significant barriers against reaction in the C + NO or O + CN channels. This surface has been fitted to an analytical function using a many-body expansion. Using this surface, and the previously published (2)A' and (2)A'' surfaces [Andersson et al., Phys. Chem. Chem. Phys., 2000, 2, 613; Andersson et al., Chem. Phys., 2000, 259, 99], we have performed quasiclassical trajectory (QCT) calculations, obtaining rate coefficients for the C((3)P) + NO(X(2)Pi) --> CO(X(1)Sigma(+)) + N((4)S,(2)D) and C((3)P) + NO(X(2)Pi) --> O((3)P) + CN(X(2)Sigma(+)) reactions. We have also simulated the crossed molecular beam experiments of Naulin et al. [Chem. Phys., 1991, 153, 519] The inclusion of the (4)A'' surface in the QCT calculations gives excellent agreement with experiments. This is the first time an adiabatic pathway from C((3)P) + NO(X(2)Pi) to CO(X(1)Sigma(+))+N((4)S) has been reported.
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| 2. |
- Abrahamsson, Erik, 1974, et al.
(författare)
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Classical and quantum dynamics of the O+CN reaction
- 2006
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 324:2-3, s. 507-514
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Tidskriftsartikel (refereegranskat)abstract
- Electronic structure (CASPT2) calculations have been performed for the (2)Pi and (4)Sigma(-) states of the NCO system. To create the potential energy surfaces, the generalized discrete variable representation (GDVR) method has been used. Wave packet calculations have been performed for the collinear O + CN reaction on both surfaces. These are the first reported quantum dynamics calculations on this reaction. State-to-state reaction probabilities are presented. On the (2)Pi surface, which has an almost 6 eV deep well, we obtain structure in the reaction probabilities at low kinetic energies but at higher energies they are smooth. The (4)Sigma(-) surface is highly exoergic and vibrationally non-adiabatic dynamics is observed. The (4)Sigma(-) surface has an early barrier and as a result we find that translational energy more efficiently promotes the reaction than vibrational energy does. The wave packet results are compared with QCT results. Generally the agreement is good as would be expected but some notable differences are found, particularly for reaction out of the vibrational ground state. (c) 2005 Elsevier B.V. All rights reserved.
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| 3. |
- Abrahamsson, Erik, 1974, et al.
(författare)
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Dynamics of the O + CN Reaction and N + CO Scattering on Two Coupled Surfaces
- 2009
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Ingår i: J. Phys. Chem. A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 113:52, s. 14824-14830
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Tidskriftsartikel (refereegranskat)abstract
- Spin−orbit coupling between the two collinear 2Π and 4Σ− potential energy surfaces for the NCO system are calculated using the RASSI method with CASSCF wave functions as basis set. The GDVR method has been used to interpolate a spin−orbit coupling surface. Wave packet and quasi-classical trajectory surface hopping calculations have been performed and compared for both the O(3P) + CN(X2Σ+) → N(4S) + CO(X1Σ+) reaction and for electronically inelastic scattering in the N + CO channels. The O + CN nonadiabatic reaction probabilities are small. The wavepacket study gives a resonance structure. Also for the N + CO electronically inelastic scattering the wave packet calculations give a distinct resonance structure with peak transition probabilities up to around 10%, which is somewhat lower than the trajectory surface hopping results.
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| 4. |
- Andersson, Stefan, 1973, et al.
(författare)
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Comparison of quantum dynamics and quantum transition state theory estimates of the H + CH4 reaction rate.
- 2009
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Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1520-5215 .- 1089-5639. ; 113:16, s. 4468-78
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Tidskriftsartikel (refereegranskat)abstract
- Thermal rate constants are calculated for the H + CH(4) --> CH(3) + H(2) reaction employing the potential energy surface of Espinosa-Garcia (Espinosa-Garcia, J. J. Chem. Phys. 2002, 116, 10664). Two theoretical approaches are used. First, we employ the multiconfigurational time-dependent Hartree method combined with flux correlation functions. In this way rate constants in the range 225-400 K are obtained and compared with previous results using the same theoretical method but the potential energy surface of Wu et al. (Wu, T.; Werner, H.-J.; Manthe, U. Science 2004, 306, 2227). It is found that the Espinosa-Garcia surface results in larger rate constants. Second, a harmonic quantum transition state theory (HQTST) implementation of instanton theory is used to obtain rate constants in a temperature interval from 20 K up to the crossover temperature at 296 K. The HQTST estimates are larger than MCTDH ones by a factor of about three in the common temperature range. Comparison is also made with various tunneling corrections to transition state theory and quantum instanton theory.
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| 5. |
- Andersson, Stefan, 1973, et al.
(författare)
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Rotational Transitions of CO+ Induced by Atomic Hydrogen
- 2008
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Ingår i: The Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 678, s. 1042-1048
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Tidskriftsartikel (refereegranskat)abstract
- The CO+ molecular ion has been observed in photon-dominated regions. Recent modeling has not been able to explain the abundances of CO+ in these regions. The most abundant collision partners are believed to be hydrogen atoms, hydrogen molecules, and electrons. The reactions of these species with CO+ have been studied previously and found to be fast. The only inelastic processes studied before were collisions of CO+ with electrons. Here we investigate the inelastic collisions of CO+ with hydrogen atoms. We argue that this can be done on the lowest triplet electronic state. This implies that CO+ ions, in a hydrogen atom dominated surrounding, experiences a few inelastic collisions before reacting. Rotationally inelastic state-to-state cross sections ( ) are presented together with state-resolved thermal rate coefficients. The results suggest that the rotationally inelastic collision cross sections can be of comparable magnitude to the reactive ones. Implications for the rotational temperature of CO+ in PDRs are discussed. To perform the calculations, a potential energy surface is fitted using the reproducing-kernel Hilbert space method based on multireference configuration-interaction calculations employing the aug-cc-pVQZ basis set.
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| 6. |
- Antipov, Sergey V., 1986, et al.
(författare)
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Rate coefficient of CN formation through radiative association: A theoretical study of quantum effects
- 2009
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Ingår i: J. Chem. Phys.. - : AIP Publishing. ; 131
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Tidskriftsartikel (refereegranskat)abstract
- Radiative association of CN is simulated using a quantum dynamical as well as a semiclassical approach. A comparison of the resulting energy-resolved cross sections reveals striking quantum effects that are due to shape resonances. These, in turn, arise because of states that are quasibound by the centrifugal barrier. The quantal rate coefficient for temperatures from 40 to 1900 K has been computed using the Breit–Wigner theory to account for the resonances. Comparison with the results obtained by Singh and Andreazza [ Astrophys. J. 537, 261 (2000) ] shows that the semiclassical method, which completely omits the shape resonances, is accurate to within 25% above room temperature. At lower temperatures the contribution from the shape resonances to the radiative association rate is more significant.
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| 7. |
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| 8. |
- Balint-Kurti, Gabriel, et al.
(författare)
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Grid-Technology for Chemical Reactions Calculation
- 2005
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Ingår i: Lecture Notes in Computer Science, vol 3516. - Berlin/Heidelberg : Springer-Verlag. ; , s. 933-936
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Balint-Kurti, Gabriel, et al.
(författare)
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Grid-Technology for Chemical Reactions Calculation (Computational Science – ICCS 2005)
- 2005
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Ingår i: Lecture Notes in Computer Science, Vol 3516: Computational Science – ICCS 2005, 5th International Conference, Atlanta, GA, USA, May 22-25, 2005, Proceedings, Part III (V.S. Sunderam, G.D. van Albada, J. Dongarra, editors). - Berlin/Heidelberg : SpringerLink. - 9783540260448 ; , s. 97-133
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We discuss a possible strategy for implementing a grid-based approach to realizing the immense computational resources required to compute reactive molecular scattering cross sections and rate constants.
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| 10. |
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| 11. |
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| 12. |
- Björk, Jonas, et al.
(författare)
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Prediction of relative glomerular filtration rate in adults: New improved equations based on Swedish Caucasians and standardized plasma-creatinine assays.
- 2007
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 67:7, s. 678-695
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To evaluate newly developed equations predicting relative glomerular filtration rate(GFR) in adult Swedish Caucasians and to compare with the Modification of Diet in Renal Disease(MDRD) and Mayo Clinic equations using enzymatic and zero-calibrated plasma creatinine assays. MATERIAL AND METHODS: GFR was measured with iohexol clearance adjusted to 1.73 m(2). One population sample (n=436/Lund) was used to derive an equation based on plasma-creatinine/age/gender, and a second with the addition of lean body mass (LBM). Both equations were validated in a separate sample (n=414/Malmö). The coefficients of the equations were eventually fine-tuned using all 850 patients and yielding Lund-Malmö equations without (LM) and with LBM-term (LM(LBM)).Their performance was compared with the MDRD(CC) (conventional creatinine calibration), MDRD(IDMS) (isotope dilution mass spectroscopy traceable calibration) and Mayo Clinic equations. RESULTS: The Lund equations performed similarly in both samples. In the combined set, the Mayo Clinic/MDRD(CC) resulted in +19.0/+10.2 % median bias, while bias for the other equations was < 10 %. LM(LBM) had the highest accuracy (86 % of estimates within 30 % of measured GFR), significantly (p < 0.001) better than for MDRD(IDMS) (80 %). In men with BMI < 20 kg/m(2), MDRD(IDMS)/LM had +46 %/+19 % median bias. MDRD(IDMS) also overestimated GFR by 22 %/14 % in men/women above 80 years of age. The LM(LBM) equation had < 10 % bias irrespective of BMI, age or GFR except for a 15 % negative bias at GFR > 90 mL/min/1.73 m(2). CONCLUSION: The newly developed Lund-Malmö equations for GFR estimation performed better than the MDRD(IDMS) and Mayo Clinic equations in a Swedish Caucasian sample. Inclusion of an LBM term improved performance markedly in certain subgroups.
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| 13. |
- Bäcktorp, Carina, 1964, et al.
(författare)
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Direct dynamics study of ultrafast vibrational energy relaxation in ice Ih.
- 2005
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Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 109:14, s. 3105-10
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Tidskriftsartikel (refereegranskat)abstract
- Car-Parrinello molecular dynamics (CPMD) and a previously developed wave packet model are used to study ultrafast relaxation in water clusters. Water clusters of 15 water molecules are used to represent ice Ih. The relaxation is studied by exciting a symmetric or an asymmetric stretch mode of the central water molecule. The CPMD results suggest that relaxation occurs within 100 fs. This is in agreement with experimental work by Woutersen and Bakker and the earlier wave packet calculations. The CPMD results further indicate that the excitation energy is transferred both intramolecularly and intermolecularly on roughly the same time scale. The intramolecular energy transfer occurs predominantly between the symmetric and asymmetric modes while the bend mode is largely left unexcited on the short time scale studied here.
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| 14. |
- Bäcktorp, Carina, 1964, et al.
(författare)
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Mechanism of Air Oxidation of the Fragrance Terpene Geraniol
- 2008
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Ingår i: J.Chem.Theory Comput.. - : American Chemical Society (ACS). ; 4, s. 101-106
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Tidskriftsartikel (refereegranskat)abstract
- The fragrance terpene geraniol autoxidizes upon air exposure and forms a mixture of oxidation products, some of which are skin sensitizers. Reactions of geraniol with O2 have been studied with DFT (B3LYP) and the computational results compared to experimentally observed product ratios. The oxidation is initiated by hydrogen abstraction, forming an allylic radical which combines with an O2 molecule to yield an intermediate peroxyl radical. In the subsequent step, geraniol differs from previously studied cases, in which the radical chain reaction is propagated through intermolecular hydrogen abstraction. The hydroxy-substituted allylic peroxyl radical prefers an intramolecular rearrangement, producing observable aldehydes and the hydroperoxyl radical, which in turn can propagate the radical reaction. Secondary oxidation products like epoxides and formates were also considered, and plausible reaction pathways for formation are proposed.
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| 15. |
- Bäcktorp, Carina, 1964, et al.
(författare)
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Mechanisms of Air Oxidation of Ethoxylated Surfactants - Computational Estimations of Energies and Reaction Behaviors
- 2008
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 14:31, s. 9549-9554
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Tidskriftsartikel (refereegranskat)abstract
- Pathways for formation of previously observed autoxidation products of ethoxylated surfactants have been studied by DFT (B3LYP). In addition to the established radical-chain reaction, several mechanistic possibilities for intramolecular fragmentation of the intermediate radicals have been characterized concerning reaction barriers and energies of transition states. The results can rationalize the formation of previously observed autoxidation products, including several, which have been implicated as strongly allergenic.
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| 16. |
- Bäcktorp, Carina, 1964, et al.
(författare)
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Theoretical investigation of linalool oxidation.
- 2006
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Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 110:44, s. 12204-12
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Tidskriftsartikel (refereegranskat)abstract
- This study concerns the autoxidation of one of the most used fragrances in daily life, linalool (3,7-dimethyl-1,6-octadien-3-ol). It reacts with O2 to form hydroperoxides, which are known to be important contact allergens. Pathways for hydroperoxide formation are investigated by means of quantum mechanical electronic structure calculations. Optimized molecular geometries and harmonic vibrational frequencies are determined using density functional theory (DFT). Insight into how the addition of O2 to linalool occurs is obtained by establishing a theoretical framework and systematically investigating three smaller systems: propene, 2-methyl-2-butene, and 2-methyl-2-pentene. 2-Methyl-2-pentene was chosen as a model system and used to compare with linalool. This theoretical study characterizes the linalool-O2 biradical intermediate state, which constitutes a branching point for the further oxidation reactions pathways. Thus, the observed linalool oxidation product spectrum is discussed in terms of a direct reaction path, the ene-type mechanism, and the radical mechanism. The major hydroperoxide found in experiments is 7-hydroperoxy-3,7-dimethyl-octa-1,5-diene-3-ol, and the calculated results support this finding.
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| 17. |
- Dahlstrand, Ursula, et al.
(författare)
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Primary patency of percutaneously inserted self-expanding metallic stents in patients with malignant biliary obstruction
- 2009
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Ingår i: HPB : the official journal of the International Hepato Pancreato Biliary Association. - : Elsevier BV. - 1365-182X. ; 11:4, s. 358-63
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Effective bile duct drainage is crucial to the health-related quality of life of patients with jaundice caused by obstruction of the bile duct by inoperable malignant tumours. METHODS: All patients who were treated at Uppsala University Hospital, Sweden with percutaneous stenting between 2000 and 2005 were identified retrospectively. Data on the location of the obstruction and type of stent used, date and cause of death and date of stent failure were abstracted from the patients' notes. Stent patency was defined as the duration from the insertion of the stent to the date of failure. In cases in which the cause of death was directly related to failure of the stent, the date of death was defined as the patency endpoint. RESULTS: A total of 64 patients (34 women, 30 men) were identified. Their mean age was 71 years (standard deviation 11 years). The median length of patency was 11.4 months. Stent diameter >10 mm and distal stricture were found to be associated with significantly longer patency time in univariate Cox proportional hazard analysis. In multivariate Cox proportional hazard analysis, only location of the stricture was found to be independently and significantly associated with patency time. DISCUSSION: Percutaneous stenting is a good alternative for patients with obstructive jaundice and a life expectancy /=10 mm. However, patency time was found to be lower for hilar tumours.
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| 18. |
- Davidsson, Jan, et al.
(författare)
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Structural determination of a transient isomer of CH2I2 by picosecond x-ray diffraction
- 2005
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 94:24
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Tidskriftsartikel (refereegranskat)abstract
- Ultrafast time-resolved spectroscopic studies of complex chemical reactions in solution are frequently hindered by difficulties in recovering accurate structural models for transient photochemical species. Time-resolved x-ray and electron diffraction have recently emerged as techniques for probing the structural dynamics of short lived photointermediates. Here we determine the structure of a transient isomer of photoexcited CH2I2 in solution and observe the downstream reactions of the initial photoproducts. Our results illustrate how geminate recombination proceeds via the formation of a transient covalent bond onto the iodine atom remaining with the parent molecule. Further intramolecular rearrangements are thus required for the CH2I-I isomer to return to CH2I2. The generation of I-3(-) from those iodine radicals escaping the solvent cage is also followed with time.
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| 19. |
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| 20. |
- Eriksson, Lars-Gunnar, et al.
(författare)
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Endoscopic marking with metallic clip facilitates transcatheter arterial embolization in upper peptic ulcer bleeding.
- 2006
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Ingår i: Journal of Vascular and Interventional Radiology. - 1051-0443 .- 1535-7732. ; 17:6, s. 959-964
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To enable accurate transcatheter arterial embolization (TAE) of the target vessel, a new technique to localize the exact position of a bleeding ulcer was tested that involves endoscopic marking of the ulcer with a metallic clip. MATERIALS AND METHODS: In 13 patients (mean age, 75 years) with acute bleeding ulcers (11 duodenal ulcers, two malignant ulcers), a metallic clip was placed at gastroscopy followed or preceded by routine endoscopic treatment. The metallic clip was placed in the fibrous edge of the ulcer adjacent to the bleeding point. In 10 patients, TAE was indicated as a result of continued or recurrent bleeding. The artery was embolized with microcoils as close as possible to the clip. In three patients, there was no indication for TAE, so plain abdominal radiography was performed to determine whether the marking clip was still in place. RESULTS: In 11 patients, the clip was still in place on radiography; in two, it had disappeared. Hemostasis was achieved in eight of 10 patients after TAE. In six patients, the clip was essential to identify the bleeding vessel. CONCLUSION: Marking of the bleeding ulcer with a clip before TAE enhances the possibility that the correct vessel is embolized. This will most likely minimize the risk of recurrent bleeding after embolization, especially in patients who do not show contrast medium extravasation.
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| 21. |
- Eriksson, Lars-Gunnar, et al.
(författare)
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Massive Postpartum Hemorrhage Treated with Transcatheter Arterial Embolization : Technical aspects and long-term effects on fertility and menstrual cycle
- 2007
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 48:6, s. 635-642
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Tidskriftsartikel (refereegranskat)abstract
- Background: Transcatheter arterial embolization (TAE) is considered a safe, life-saving procedure in postpartum hemorrhage (PPH), but its long-term effect on menstruation and fertility is unclear. Purpose: To investigate technical aspects and the evaluation of complications, focused on menstrual cycle and fertility, using TAE in patients with PPH. Material and Methods: A retrospective study including 20 patients (seven with vaginal and 13 with cesarean delivery) with severe PPH treated with bilateral TAE of the uterine artery was carried out. All patients were asked to answer a questionnaire regarding their post-embolization history. In six patients, the radiation dose was measured. Results: All 20 cases underwent bilateral TAE of the uterine artery. Gelfoam was used as the embolic agent. However, after cesarean delivery in six patients who had clear contrast medium extravasation and/or pseudoaneurysm-like lesion, metallic coils had to be used in order to achieve hemostasis. No major short- or long-term complications were registered. Normal menses resumed in all patients. Four patients had a total of five full-term and two preterm pregnancies, and all delivered healthy infants by cesarean section with no recurrence of PPH. The mean radiation dose to the ovaries was 586 mGy (range 204-729 mGy). Conclusion: TAE in patients with PPH is safe and has no major short- or long-term side effects. A patient managed with TAE can expect return of normal menses and preservation of future fertility and successful pregnancies. PPH after cesarean section might need to be embolized with metallic coils in addition to Gelfoam in order to achieve secure hemostasis.
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| 22. |
- Eriksson, Lars-Gunnar, 1956-
(författare)
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Transcatheter Arterial Embolization in the Management of Life Threatening Bleeding Applied in Upper Gastrointestinal and Post Partum Bleedings.
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transcatheter Arterial Embolization (TAE) is a method in which a catheter is inserted into an artery under fluoroscopy guidance. By using material that creates a thrombus, inserted through the catheter, the artery can be occluded and the bleeding stopped.Endoscopy is the treatment of choice in upper gastrointestinal (GI) bleeding, but 10% to 30% of patients rebleed and needs other treatment options. Post Partum Hemorrhage (PPH) may evolve rapidly and can become life threatening. Obstetrical treatment will manage most cases, but in some cases emergency surgery is needed and in the worst case hysterectomy.The primary aim of this thesis was to evaluate the clinical usefulness, improve the TAE technique and compare the outcome of TAE with surgery used as “salvage therapy” in patients with upper GI bleeding. Evaluate TAE technique and the long-term effect on the menstrual cycle and fertility in severe PPH.To evaluate the clinical usefulness 13 patients were treated with TAE after endoscopic treatment failure and 5 were treated for recurrent hemorrhage after emergency surgery. The clinical outcome and mortality rate of 40 patients treated with TAE was compared with 51 patients treated with surgery of upper GI bleedings. In 13 patients the ulcer was marked with placement of a metallic clip at endoscopy to be able to locate the exact site of the bleeding ulcer during the TAE procedure.A retrospective study of 20 patients with severe PPH treated with bilateral TAE of the uterine artery was performed. TAE was found to be effective and an alternative to emergency surgery for control of massive upper GI bleeding. The 30-day mortality was lower in the TAE group (3%) compared to the surgical group (14%). By marking the bleeding ulcer at endoscopy using a metallic clip the site of bleeding could be identified on angiography without extravasation of contrast media.No major impact on fertility or menstruation cycle was found in patients treated with TAE in PPH. TAE in PPH is safe and have no major long-term side effect. By using TAE in PPH hysterectomy can be avoided.
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| 23. |
- Eriksson, Lars-Gunnar, 1956-, et al.
(författare)
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Transcatheter arterial embolization versus surgery in the treatment of upper gastrointestinal bleeding after therapeutic endoscopy failure
- 2008
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Ingår i: Journal of Vascular and Interventional Radiology. - : Elsevier BV. - 1051-0443 .- 1535-7732. ; 19:10, s. 1413-8
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To retrospectively compare the outcome of transcatheter arterial embolization (TAE) and surgery as salvage therapy of upper gastrointestinal bleeding after failed endoscopic treatment. MATERIALS AND METHODS: From January 1998 to December 2005, 658 patients were referred to diagnostic/therapeutic emergency endoscopy and diagnosed with upper gastrointestinal bleeding. Ninety-one of these 658 patients (14%) had repeat bleeding or continued to bleed. Forty of those 91 patients were treated with TAE and 51 were treated with surgery. From the medical records, the following variables were recorded: demographic data, endoscopic diagnoses, comorbidities, lowest hemoglobin levels, total transfusion requirements, lengths of hospitalization stays, postprocedure complications, and mortality rates. The relative survival rate was calculated, and survival probability was calculated with the Kaplan-Meier technique. RESULTS: Patients treated with TAE were older (mean age, 76 years; age range, 40-94 years) and had slightly more comorbidities compared to patients who underwent surgery (mean age, 71 years; age range, 45-89 years). The 30-day mortality rate in patients treated with TAE was one of 40 (3%) compared to seven of 51 (14%) in patients treated with surgery (P < .07). Most repeat bleeding could be effectively treated with TAE, both in the surgical and TAE groups. CONCLUSIONS: The results of this study suggest that, after failure of therapeutic endoscopy for upper gastrointestinal bleeding, TAE should be the treatment of choice before surgery and that TAE can also be used to effectively control bleeding after failed surgery or TAE. There was a clear trend to lower 30-day mortality with use of TAE instead of surgery.
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| 24. |
- Espinosa-García, J, et al.
(författare)
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The hydrogen abstraction reaction H + CH4. II. Theoretical investigation of the kinetics and dynamics.
- 2009
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Ingår i: The Journal of chemical physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 130:18
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Tidskriftsartikel (refereegranskat)abstract
- On a new potential energy surface (PES-2008) developed by our group (preceding paper), we performed an extensive kinetics study using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range of 250-2000 K and a dynamics study using quasiclassical trajectory (QCT) and quantum-mechanical (QM) calculations at collision energies between 0.7 and 2.0 eV for the title reaction and isotopically substituted versions. Kinetically, the H + CH(4) forward and reverse thermal rate constants reproduce the available experimental data, with a small curvature of the Arrhenius plot indicating the role of tunneling in this hydrogen abstraction reaction. Five sets of kinetic isotope effects are also calculated. In general, they reproduce the experimental information. Dynamically, we focused on the H + CD(4) reaction because there are more experimental studies for comparison. Most of the available energy appears as product translational energy (55%-68%), with the HD product being vibrationally cold (v(')=0,1) in agreement with experiment, although rotationally hotter than experiment. The reaction cross section is practically negligible at 0.7 eV and still small at 1.5 eV, reproducing the experimental evidence, although our values are smaller. The product angular distribution is analyzed using QCT and QM methods. While at low energies (0.7 eV) both the QCT and the QM calculations yield forward scattered CD(3) product, i.e., a rebound mechanism, at high energy (1.2 eV) only the QM calculations reproduce the experiment. The agreement with this wide variety of kinetic and dynamic experimental data (always qualitative and in some cases quantitative) shows the capacity of the PES-2008 surface to describe the reaction system.
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| 25. |
- Evenhuis, Chris, et al.
(författare)
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Quantum dynamics of the CH3 fragment: A curvilinear coordinate system and kinetic energy operators
- 2007
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Ingår i: The Journal of chemical physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127, s. 144302-144312
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Tidskriftsartikel (refereegranskat)abstract
- A curvilinear coordinate system for AB3 fragments is given. The corresponding exact kinetic energy operator is derived and a series of simpler, progressively more approximate kinetic energy operators are suggested. The operators are tailored for quantum dynamics simulations using the multiconfigurational time-dependent Hartree approach. It is outlined how these fragment coordinates can be utilized to set up coordinate systems for larger systems such as AB3C or AB3CD. Calculations of the vibrational levels of CH3 and quantum dynamics studies investigate the accuracy of the different kinetic energy operators suggested.
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| 26. |
- Frankcombe, Terry J, et al.
(författare)
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Adiabatic Capture Theory Applied to N + NH N2 + H at Low Temperature
- 2007
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Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:50, s. 13163-13167
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Tidskriftsartikel (refereegranskat)abstract
- The adiabatic capture centrifugal sudden approximation (ACCSA) has been applied to the ground state reaction N + NH N2 + H over the temperature range 2-300 K using an existent potential energy surface. The resultant thermal rate constants are in agreement with available rate constants from quasi-classical trajectory calculations but are significantly larger than the available experimentally derived rate. The calculated rate constants monotonically increase with increasing temperature but could only be approximately described with a simple Arrhenius-like form. Subtle quantum effects are evident in the initial rotational state resolved cross sections and rate constants.
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| 27. |
- Frankcombe, Terry J, et al.
(författare)
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Statistical modelling of NH+/ND+ + H2/HD/D2 branching ratios.
- 2008
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Ingår i: Physical chemistry chemical physics : PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 10:20, s. 3000-13
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Tidskriftsartikel (refereegranskat)abstract
- In this work we study hydrogen isotope fractionation along the proposed gas-phase ammonia formation pathway at temperatures relevant to interstellar modelling. Specifically we study the isotopically substituted variants of the NH(+) + H(2) reaction, for which the primary product is NH(2)(+) + H. Adiabatic capture theory calculations have been performed for the association reaction. A new potential-energy surface has been determined for the NH(2)(+) product. An extensive set of rovibrational energy levels has been calculated for the NH(2)(+) isotopologues described by this potential-energy surface. These rovibrational energy levels have been used to determine energy- and angular-momentum-resolved numbers of accessible product states from the NH(3)(+) isotopologue intermediates, which in turn have been averaged to give statistical branching fractions for all isotopically-substituted NH(+) + H(2) reactions. It is determined that in all cases where both hydrogen and deuterium are present, the NHD(+) product is preferred.
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| 28. |
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| 29. |
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| 30. |
- Gevorkyan, Ashot S., et al.
(författare)
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Regular and chaotic quantum dynamics in atom-diatom reactive collisions
- 2008
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Ingår i: Physics of Atomic Nuclei. ; 71:5, s. 876-883
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Tidskriftsartikel (refereegranskat)abstract
- A new microirreversible 3D theory of quantum multichannel scattering in the three-body system is developed. The quantum approach is constructed on the generating trajectory tubes which allow taking into account influence of classical nonintegrability of the dynamical quantum system. When the volume of classical chaos in phase space is larger than the quantum cell in the corresponding quantum system, quantum chaos is generated. The probability of quantum transitions is constructed for this case. The collinear collision of the Li + (FH) → (LiF) + H system is used for numerical illustration of a system generating quantum (wave) chaos. PACS numbers 03.65.-w - 34.10.+x - 34.50.Lf - 45.20.Jj - 32.80
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| 31. |
- Grage, Mette, et al.
(författare)
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HCl and DCl: A case study of different approaches for determining photo fractionation constants
- 2006
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 8:41, s. 4798-4804
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Tidskriftsartikel (refereegranskat)abstract
- The photoabsorption cross sections of HCl and DCl are calculated using the reflection principle and time dependent wavepacket propagation methods. The absorption cross sections are compared to high precision experimental absorption cross sections from the literature and the different results given by the methods are discussed. The results of the calculations emphasize the important roles that photodissociation dynamics and the change in transition dipole moment with internuclear distance play in isotopic fractionation. The wave number dependent fractionation constants have been determined. The process fractionation constant has been calculated in the Venusian atmosphere where photo-fractionation leads to enrichment in deuterium through loss of hydrogen to space. At an altitude of 70 km the process fractionation constant was found to be epsilon(p) = -344 parts per thousand and epsilon(p) = -256 parts per thousand for the experimental and the reflection principle methods, respectively. At the top of the atmosphere the process fractionation constant was evaluated to be epsilon(p) = -32 parts per thousand, epsilon(p) = -20 parts per thousand and epsilon(p) = -40 parts per thousand using the experimental data, the wavepacket and the reflection principle methods, respectively. Using the Rayleigh distillation formula it is concluded that HCl at the top of the Venusian atmosphere is fractionated ( enriched in D) relative to the bulk composition prior to photolysis.
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| 32. |
- Granberg, Dan, et al.
(författare)
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Liver embolization with trisacryl gelatin microspheres (embosphere) in patients with neuroendocrine tumors
- 2007
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 48:2, s. 180-185
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To report our experience of liver embolization with trisacryl gelatin microspheres (Embospheretrade mark) in patients with metastatic neuroendocrine tumors. MATERIAL AND METHODS: Fifteen patients underwent selective embolization of the right or left hepatic artery with Embosphere. One lobe was embolized in seven patients and both lobes, on separate occasions, in eight patients. Seven patients had midgut carcinoids, two had lung carcinoids, one suffered from a thymic carcinoid, and five had endocrine pancreatic tumors. Eight patients suffered from endocrine symptoms, seven of whom had carcinoid syndrome and one WDHA (watery diarrhea, hypokalemia, achlorhydria) syndrome. RESULTS: Partial radiological response was seen after eight embolizations (in six different patients), stable disease was observed after 13 embolizations (after three of these, necroses occurred), while radiological progression was noted after only two embolizations. Only two patients experienced a biochemical response. Clinical improvement of carcinoid syndrome was observed after five embolizations. There were no major complications. Fever >38 degrees C was seen after all but four embolizations, and urinary tract infections were diagnosed after eight embolizations. CONCLUSION: Selective hepatic artery embolization with Embosphere particles is a safe treatment for patients with metastatic neuroendocrine tumors and may lead to partial radiological response as well as symptomatic improvement of disabling endocrine symptoms.
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| 33. |
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| 34. |
- Grubb, Anders, et al.
(författare)
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Simple Cystatin C-Based Prediction Equations for Glomerular Filtration Rate Compared with the Modification of Diet in Renal Disease Prediction Equation for Adults and the Schwartz and the Counahan-Barratt Prediction Equations for Children.
- 2005
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 51:8, s. 1420-1431
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Serum creatinine is the most commonly used marker for estimation of glomerular filtration rate (GFR). To compensate for its drawbacks as a GFR marker, several prediction equations including several parameters are being used, with the Modification of Diet in Renal Disease (MDRD), Schwartz, and Counahan-Barratt equations being the ones most widely accepted for estimation of relative GFR in mL x min(-1) x (1.73 m(2))(-1). The present study analyzes whether these GFR prediction equations for adults and children might be replaced by simple prediction equations based on plasma concentrations of cystatin C.METHODS: Data from 536 patients (0.3-93 years), consecutively referred for determination of GFR by an invasive gold standard procedure, were used for the analysis. Calculations of bias (median percentage of error), correlation (adjusted R(2)), and percentage of estimates within 30% and 50% of measured GFR were used in the comparisons.RESULTS: A cystatin C-based prediction equation using only concentration in mg/L and a prepubertal factor: GFR [mL x min(-1) x (1.73 m(2))(-1)] = 84.69 x cystatin C (mg/L)(-1.680) x 1.384 (if a child <14 years) assessed GFR equally well or better than the simplified MDRD, the Schwartz, and the Counahan-Barratt prediction equations for the adult (> or =18 years) and juvenile groups of the investigated cohort. Age did not influence the cystatin C-based prediction equation for adults, whereas gender did, but with a factor close to unity (0.948 for females).CONCLUSION: A GFR prediction equation based solely on cystatin C (in mg/L) and a prepubertal factor might replace the simplified MDRD prediction equation for adults and the Schwartz and Counahan-Barratt prediction equations for children.
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| 35. |
- Haglund, Marie, et al.
(författare)
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Kontrastnefropati efter datortomografi. Hydrering och anpassad kontrastmedelsdos ger bästa profylax
- 2005
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Ingår i: Läkartidningen. - 0023-7205. ; 102:40, s. 2864-2870
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Tidskriftsartikel (refereegranskat)abstract
- Nefrotoxicitet efter kontrastmedelstillförsel, räknat som en 25-procentig stegring av kreatinin i plasma, förekom hos 12 procent i en oselekterad grupp patienter som genomgått datortomografi. Generell arterioskleros kan läggas till övriga kända riskfaktorer för utveckling av kontrastmedelsnefrotoxicitet. Uppskattning av njurfunktion, t ex med hjälp av lämplig formel, bör göras före kontrastmedelstillförsel, särskilt hos patienter över 70 års ålder. För att minimera risken för njurpåverkan bör kontrastmedelsdosen uttryckt i gram jod understiga det numeriska värdet av den glomerulära filtrationshastigheten (GFR) uttryckt i ml/min.
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| 36. |
- Hagvall, Lina, 1978, et al.
(författare)
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Fragrance compound geraniol forms contact allergens on air exposure. Identification and quantification of oxidation products and effect on skin sensitization
- 2007
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 20:5, s. 807-814
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Tidskriftsartikel (refereegranskat)abstract
- Fragrances are common causes of contact allergy. Geraniol (trans-3,7-dimethyl-2,6-octadiene-1-ol) is an important fragrance terpene. It is considered a weak contact allergen and is used for fragrance allergy screening among consecutive dermatitis patients. Analogous to other monoterpenes studied, such as limonene and linalool, geraniol has the potential to autoxidize on air exposure and form highly allergenic compounds. The aim of the present study was to investigate and propose a mechanism for the autoxidation of geraniol at room temperature. To investigate whether allergenic compounds are formed, the sensitizing potency of geraniol itself, air-exposed geraniol, and its oxidation products was determined using the local lymph node assay in mice. The results obtained show that the allylic alcohol geraniol follows an oxidation pattern different from those of linalool and limonene, which autoxidize forming hydroperoxides as the only primary oxidation products. The autoxidation of geraniol follows two paths, originating from allylic hydrogen abstraction near the two double bonds. From geraniol, hydrogen peroxide is primarily formed together with aldehydes geranial and neral from a hydroxyhydroperoxide. In addition, small amounts of a hydroperoxide are formed, analogous to the formation of the major linalool hydroperoxide. The autoxidation of geraniol greatly influenced the sensitizing effect of geraniol. The oxidized samples had moderate sensitizing capacity, quite different from that of pure geraniol. The hydroperoxide formed is believed to be the major contributor to allergenic activity, together with the aldehydes geranial and neral. On the basis of the present study and previous experience, we recommend that the possibility of autoxidation and the subsequent formation of contact allergenic oxidation products are considered in risk assessments performed on fragrance terpenes.
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| 37. |
- Huss, Fredrik, 1971-, et al.
(författare)
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Characterisation of a new degradable polymer scaffold for regeneration of the dermis : In vitro and in vivo human studies
- 2008
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Ingår i: Organogenesis. - 1547-6278. ; 4:3, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- Full thickness skin wounds in humans heal with scars, but without regeneration of the dermis. A degradable poly(urethane urea) scaffold (PUUR), Artelon® is already used to reinforce soft tissues in orthopaedics, and for treatment of osteoarthritis of the hand, wrist and foot. In this paper we have done in vitro experiments followed by in vivo studies to find out whether the PUUR is biocompatible and usable as a template for dermal regeneration. Human dermal fibroblasts were cultured on discs of PUUR, with different macrostructures (fibrous and porous). They adhered to and migrated into the scaffolds, and produced collagen. The porous scaffold was judged more suitable for clinical applications and 4 mm Ø, 2 mm-thick discs of porous scaffold (12% w/w or 9% w/w polymer solution) were inserted intradermally in four healthy human volunteers. The implants were well tolerated and increasing ingrowth of fibroblasts was seen over time in all subjects. The fibroblasts stained immunohistochemically for procollagen and von Willebrand factor, indicating neocollagenesis and angiogenesis within the scaffolds. The PUUR scaffold may be a suitable material to use as a template for dermal regeneration. ©2008 Landes Bioscience.
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| 38. |
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| 39. |
- Liss, Per, et al.
(författare)
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Renal effects of CO2 and iodinated contrast media in patients undergoing renovascular intervention : a prospective, randomized study
- 2005
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Ingår i: Journal of Vascular and Interventional Radiology. - 1051-0443 .- 1535-7732. ; 16:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: CO2 gas has been proposed for use instead of iodinated contrast media in angiographic examinations in patients at risk of developing renal failure from contrast media. The influence of intraarterial injection of CO2 with small added amounts of ioxaglate (200 mgI/mL) or ioxaglate alone on renal function in patients with suspected renal artery stenosis was studied in a prospective, randomized study. MATERIALS AND METHODS: One hundred twenty-three patients underwent renovascular intervention (n = 83) and/or renal angiography (n = 40) for suspected renal artery stenosis. Patients with a serum creatinine concentration less than 200 micromol/L (n = 82) were randomized prospectively to receive CO2 with small added amounts of ioxaglate (n = 37) or only ioxaglate (n = 45). Patients with serum creatinine levels greater than 200 micromol/L (n = 41) were not randomized and initially received CO2. Serum creatinine concentrations were measured within 1 day before and 1 day, 2 days, and 2-3 weeks after the procedure. RESULTS: The amount of injected CO2 did not relate to an increase in serum creatinine level. In the randomized groups, and also when the whole patient sample was considered, the amount of injected iodine was significantly correlated (P = .011) with an increase in serum creatinine level and a decrease in estimated creatinine clearance after 2 days. Among the randomized patients, one in the CO2 group and three in the ioxaglate group had a more than 25% increase in serum creatinine level within the first 2 days after the intervention. CONCLUSION: The risk of impairment of renal function is lower after injection of CO2 with small amounts of added ioxaglate compared with injection of a larger amount of ioxaglate alone. The larger the amount of administered iodinated contrast medium, the greater the risk of development of renal failure.
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| 40. |
- Ljungman, Christer, et al.
(författare)
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Propositions for refinement of the hybrid surgical technique for treatment of thoraco-abdominal aortic aneurysm
- 2008
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Ingår i: Scandinavian Journal of Surgery. - 1457-4969 .- 1799-7267. ; 97:2, s. 174-177
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Forskningsöversikt (refereegranskat)abstract
- Traditional open repair of thoraco-abdominal aortic aneurysms Crawford type II-IV carries a high perioperative risk and mortality. The hybrid technique for combined surgical and endovascular treatment offers an interesting alternative with reduced risk of paraparesis and possibly a reduced mortality rate. Propositions for refinement of this approach are outlined based on a single centre experience.
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| 41. |
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| 42. |
- Nyman, Gunnar, 1957
(författare)
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Accurate and approximate thermal rate constants for polyatomic chemical reactions
- 2007
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Ingår i: Physica Scripta. ; 76:3
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Tidskriftsartikel (refereegranskat)abstract
- In favourable cases it is possible to calculate thermal rate constants for polyatomic reactions to high accuracy from first principles. Here, we discuss the use of flux correlation functions combined with the multi-configurational time-dependent Hartree (MCTDH) approach to efficiently calculate cumulative reaction probabilities and thermal rate constants for polyatomic chemical reactions. Three isotopic variants of the H-2 + CH3 -> CH4 + H reaction are used to illustrate the theory. There is good agreement with experimental results although the experimental rates generally are larger than the calculated ones, which are believed to be at least as accurate as the experimental rates. Approximations allowing evaluation of the thermal rate constant above 400K are treated. It is also noted that for the treated reactions, transition state theory (TST) gives accurate rate constants above 500 K. TST theory also gives accurate results for kinetic isotope effects in cases where the mass of the transfered atom is unchanged. Due to neglect of tunnelling, TST however fails below 400K if the mass of the transferred atom changes between the isotopic reactions.
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| 43. |
- Nyman, Gunnar, 1957, et al.
(författare)
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Crossed-beam and quantum dynamics studies of the reaction Cl+CHD3
- 2007
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Ingår i: Israel Journal of Chemistry. - 0021-2148. ; 47:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The ground-state reaction of Cl + CHD3 was studied with joint experimental and theoretical efforts. Experiments were performed under crossed-beam conditions using a time-sliced velocity imaging detection method. By taking the images over the energy range of chemical significance—from threshold to about 9 kcal/mol—the reactive excitation functions as well as the dependence of product angular distributions and of the energy disposal on initial collision energies were obtained for both isotopic product channels. Theoretically, reduced dimensionality quantum dynamics calculations were performed for the HCl + CD3 channel, and the results are in excellent agreement with experimental findings. Comparisons with previously reported results on Cl + CH4/CD4, both experimental and theoretical, were also made to gain deeper insights into the dynamics of this benchmark atom + polyatomic reaction.
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| 44. |
- Nyman, Gunnar, 1957, et al.
(författare)
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Reduced Dimensionality Quantum Scattering Calculations on the F + CH4 FH + CH3 Reaction
- 2007
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Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:47, s. 11943-11947
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Tidskriftsartikel (refereegranskat)abstract
- The existence of recently observed scattering resonances in the hydrogen abstraction reaction F + CH4 FH + CH3 was investigated using the reduced dimensionality rotating line umbrella (RLU) quantum scattering model and employing an analytical potential energy surface, PES-2006, recently developed by our group. The calculations were performed in hyperspherical coordinates. The wells found in the hyperspherical adiabats, the oscillatory pattern in the cumulative and state-to-state reaction probabilities, the forward/backward predominance in the differential cross section at a collision energy of 1.8 kcal mol-1, and the dramatic change of the scattering angle with energy are related to scattering resonances, and they are assigned to a quasi-bound complex on the vibrationally adiabatic ground-state potential.
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| 45. |
- Nyman, Gunnar, 1957, et al.
(författare)
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Thermochemistry and Accurate Quantum Reaction Rate Calculations for H2/HD/D2 + CH3
- 2007
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Ingår i: The journal of physical chemistry. A. - 1089-5639. ; 111:41, s. 10331-10337
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Tidskriftsartikel (refereegranskat)abstract
- Accurate quantum-mechanical results for thermodynamic data, cumulative reaction probabilities (for J = 0), thermal rate constants, and kinetic isotope effects for the three isotopic reactions H2 + CH3 CH4 + H, HD + CH3 CH4 + D, and D2 + CH3 CH3D + D are presented. The calculations are performed using flux correlation functions and the multiconfigurational time-dependent Hartree (MCTDH) method to propagate wave packets employing a Shephard interpolated potential energy surface based on high-level ab initio calculations. The calculated exothermicity for the H2 + CH3 CH4 + H reaction agrees to within 0.2 kcal/mol with experimentally deduced values. For the H2 + CH3 CH4 + H and D2 + CH3 CH3D + D reactions, experimental rate constants from several groups are available. In comparing to these, we typically find agreement to within a factor of 2 or better. The kinetic isotope effect for the rate of the H2 + CH3 CH4 + H reaction compared to those for the HD + CH3 CH4 + D and D2 + CH3 CH3D + D reactions agree with experimental results to within 25% for all data points. Transition state theory is found to predict the kinetic isotope effect accurately when the mass of the transferred atom is unchanged. On the other hand, if the mass of the transferred atom differs between the isotopic reactions, transition state theory fails in the low-temperature regime (T < 400 K), due to the neglect of the tunneling effect.
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| 46. |
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| 47. |
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| 48. |
- Nyman, Rickard, et al.
(författare)
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Soft-tissue-anchored transcutaneous port for long-term percutaneous transhepatic biliary drainage
- 2005
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Ingår i: Cardiovascular and Interventional Radiology. - 0174-1551 .- 1432-086X. ; 28:1, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: A transcutaneous port (T-port) has been developed allowing easy exchange of a catheter, which was fixed inside the device, using the Seldinger technique. The objective of the study was to test the T-port in patients who had percutaneous transhepatic biliary drainage (PTBD).METHODS: The T-port, made of titanium, was implanted using local anesthesia in 11 patients (mean age 65 years, range 52-85 years) with biliary duct obstruction (7 malignant and 4 benign strictures). The subcutaneous part of the T-port consisted of a flange with several perforations allowing ingrowth of connective tissue. The T-port allowed catheter sizes of 10 and 12 Fr.RESULTS: All wounds healed uneventfully and were followed by a stable period without signs of pronounced inflammation or infection. It was easy to open the port and to exchange the drainage tube. The patient's quality of life was considerably improved even though several patients had problems with repeated bile leakage due to frequent recurrent obstructions of the tubes. The ports were implanted for a mean time of 9 months (range 2-21 months). Histologic examination in four cases showed that the port was well integrated into the soft tissue. Tilting of the T-port in two cases led to perforation of the skin by the subcutaneous part of the ports, which were removed after 7 and 8 months.CONCLUSION: The T-port served as an excellent external access to the biliary ducts. The drainage tubes were well fixed within the ports. The quality of life of the patients was considerably improved. Together with improved aesthetic appearance they found it easier to conduct normal daily activities and personal care. However, the problem of recurrent catheter obstruction remained unsolved.
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| 49. |
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| 50. |
- Nyman, U, et al.
(författare)
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Contrast-medium-induced nephropathy correlated to the ratio between dose in gram iodine and estimated GFR in ml/min
- 2005
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 46:8, s. 830-842
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To suggest a more precise tool when assessing the risk of contrast-medium-induced nephropathy (CIN), i.e. the ratio between contrast medium (CM) dose expressed in grams of iodine (g-I) and estimated glomerular filtration rate in ml/min (eGFR; based on equations using serum-creatinine (s-Cr), weight, height, age, and/or sex), here named I-dose/GFR ratio. Material and Methods: A Medline search of published CIN investigations reporting mean eGFR and mean dose of low-osmolality CM (LOCM) identified 10 randomized controlled prophylactic and 2 cohort coronary investigations, and 3 randomized and I cohort computed tomographic (CT) investigation. From the randomized trials, data were collected only from the placebo or control arms, unless there was no significant difference between the control and test groups. The mean I-dose/GFR ratio of each study was correlated with the mean frequency of CIN-1 (s-Cr rise >= 44.2 mu mol/l or >= 20-25%) and CIN-2 (oliguria or requiring dialysis). A maximum dose according to an I-dose/GFR ratio = 1 in patients with s-Cr ranging from 100 to 300 mu mol/l was compared with that of CIGARROA'S formula and with a "European consensus" threshold published by the European Society of Urogenital Radiology, both using s-Cr alone to predict renal function. MCCULLOUGH'S formula was used to assess the risk of CIN requiring dialysis at an I-dose/GFR ratio=1 with LOCM. Results: The coronary investigations revealed a linear correlation with a correlation coefficient between the I-dose/GFR ratio and the frequency of CIN-1 and CIN-2 of 0.91 (P<0.001) and 0.84 (P=0.001), respectively. At a mean I-dose/GFR ratio=1, the regression line indicated a 10% risk of CIN-1 and a 1% risk of CIN-2. At a mean I-dose/ GFR ratio=3, the risk of CIN-1 and CIN-2 increased to about 50% and 15%, respectively. Pooled weighted data from the CT investigations revealed a 12% risk of CIN-1 at a mean I-dose/GFR ratio = 1.1 and no cases of CIN-2. The maximum CM dose according to an I-dose/GFR ratio=1 was about 30-50% of that of both CIGARROA'S formula and the "European consensus" in elderly low-weight individuals, while it was similar for middle-aged individuals weighing about 90 kg. MCCULLOUGH'S formula suggests that there will be an exponentially increasing risk of CIN requiring dialysis, but at an I-dose/GFR ratio = 1 and using LOCM it will not exceed 1% until GFR decreases below 30 ml/min in diabetics and below 20 ml/min in non-diabetics. Conclusion: Using the I-dose/GFR ratio may be a more expedient way of improving risk assessment of CIN than today's common practice of estimating CM dose from volume alone and renal function from s-Cr alone. Prospective studies based on individual patient data are encouraged to define the risk of CIN at various I-dose/GFR ratios and correlated to type of CM, examination, risk factors, etc.
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