| 1. |
- Bantreil, Xavier, et al.
(författare)
-
γ- and δ-lactams through palladium-catalyzed intramolecular allylic alkylation: enantioselective synthesis, NMR Investigation, and DFT rationalization.
- 2011
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 17:10, s. 2885-96
-
Tidskriftsartikel (refereegranskat)abstract
- The Pd-catalyzed intramolecular allylic alkylation of unsaturated amides to give γ- and δ-lactams has been studied in the presence of chiral ligands. Ligand (R)-3,5-tBu-MeOBIPHEP (MeOBIPHEP = 6,6'-dimethoxybiphenyl-2,2-diyl)bis(diphenylphosphine)) afforded the best results and allowed the cyclization reactions to take place in up to 94:6 enantiomeric ratio. A model Pd-allyl complex has been prepared and studied through NMR spectroscopic analysis, which provided insight into the processes responsible for the observed enantiomeric ratios. DFT studies were used to characterize the diastereomeric reaction pathways. The calculated energy differences were in good agreement with the experimentally observed enantiomeric ratios.
|
|
| 2. |
- Chaintreau, Alain, et al.
(författare)
-
Site-specific C-13 content by quantitative isotopic C-13 nuclear magnetic resonance spectrometry : a pilot inter-laboratory study
- 2013
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 788, s. 108-113
-
Tidskriftsartikel (refereegranskat)abstract
- Isotopic C-13 NMR spectrometry, which is able to measure intra-molecular C-13 composition, is of emerging demand because of the new information provided by the C-13 site-specific content of a given molecule. A systematic evaluation of instrumental behaviour is of importance to envisage isotopic C-13 NMR as a routine tool. This paper describes the first collaborative study of intra-molecular C-13 composition by NMR. The main goals of the ring test were to establish intra-and inter-variability of the spectrometer response. Eight instruments with different configuration were retained for the exercise on the basis of a qualification test. Reproducibility at the natural abundance of isotopic C-13 NMR was then assessed on vanillin from three different origins associated with specific delta C-13(i) profiles. The standard deviation was, on average, between 0.9 and 1.2 parts per thousand for intra-variability. The highest standard deviation for inter-variability was 2.1%. This is significantly higher than the internal precision but could be considered good in respect of a first ring test on a new analytical method. The standard deviation of delta C-13(i) in vanillin was not homogeneous over the eight carbons, with no trend either for the carbon position or for the configuration of the spectrometer. However, since the repeatability for each instrument was satisfactory, correction factors for each carbon in vanillin could be calculated to harmonize the results.(C) 2013 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Soler, Josep M., et al.
(författare)
-
Predictive and Inverse Modeling of a Radionuclide Diffusion Experiment in Crystalline Rock at ONKALO (Finland)
- 2023
-
Ingår i: Nuclear Technology. - : Informa UK Limited. - 0029-5450 .- 1943-7471. ; 209:11, s. 1765-1784
-
Tidskriftsartikel (refereegranskat)abstract
- The REPRO-TDE test was performed at a depth of about 400 m in the ONKALO underground research facility in Finland. Synthetic groundwater containing radionuclide tracers [tritiated water tracer (HTO), 36Cl, 22Na, 133Ba, and 134Cs] was circulated for about 4 years in a packed-off interval of the injection borehole. Tracer activities were additionally monitored in two observation boreholes. The test was the subject of a modeling exercise by the SKB GroundWater Flow and Transport of Solutes Task Force. Eleven teams participated in the exercise, using different model concepts and approaches. Predictive model calculations were based on laboratory-based information concerning porosities, diffusion coefficients, and sorption partition coefficients. After the experimental results were made available, the teams were able to revise their models to reproduce the observations. General conclusions from these back-analysis calculations include the need for reduced effective diffusion coefficients for 36Cl compared to those applicable to HTO (anion exclusion), the need to implement weaker sorption for 22Na compared to results from laboratory batch sorption experiments, and the observation of large differences between the theoretical initial concentrations for the strongly sorbing 133Ba and 134Cs, and the first measured values a few hours after tracer injection. Different teams applied different concepts, concerning mainly the implementation of isotropic versus anisotropic diffusion, or the possible existence of borehole disturbed zones around the different boreholes. The role of microstructure was also addressed in two of the models.
|
|
| 4. |
- Soler, Josep, et al.
(författare)
-
Modelling of the LTDE-SD radionuclide diffusion experiment in crystalline rock at the Aspo Hard Rock Laboratory (Sweden)
- 2022
-
Ingår i: Geologica Acta. - : Universitat Autònoma de Barcelona. - 1695-6133 .- 1696-5728. ; 20, s. 1-32
-
Tidskriftsartikel (refereegranskat)abstract
- This study shows a comparison and analysis of results from a modelling exercise concerning a field experiment involving the transport and retention of different radionuclide tracers in crystalline rock. This exercise was performed within the Swedish Nuclear Fuel and Waste Management Company (SKB) Task Force on Modelling of Groundwater Flow and Transport of Solutes (Task Force GWFTS). Task 9B of the Task Force GWFTS was the second subtask within Task 9 and focused on the modelling of experimental results from the Long Term Sorption Diffusion Experiment in situ tracer test. The test had been performed at a depth of about 410m in the Aspo Hard Rock Laboratory. Synthetic groundwater containing a cocktail of radionuclide tracers was circulated for 198 days on the natural surface of a fracture and in a narrow slim hole drilled in unaltered rock matrix. Overcoring of the rock after the end of the test allowed for the measurement of tracer distribution profiles in the rock from the fracture surface (A cores) and also from the slim hole (D cores). The measured tracer activities in the rock samples showed long profiles (several cm) for non-or weakly-sorbing tracers (Cl-36, Na-22), but also for many of the more strongly-sorbing radionuclides. The understanding of this unexpected feature was one of the main motivations for this modelling exercise. However, re-evaluation and revision of the data during the course of Task 9B provided evidence that the anomalous long tails at low activities for strongly sorbing tracers were artefacts due to cross-contamination during rock sample preparation. A few data points remained for Cs-137, Ba-133, Ni-63 and Cd-109, but most measurements at long distances from the tracer source (>10mm) were now below the reported detection limits. Ten different modelling teams provided results for this exercise, using different concepts and codes. The tracers that were finally considered were Na-22, Cl-36, Co-57, Ni-63, Ba-133, Cs-137, Cd-109, Ra-226 and Np-237. Three main types of models were used: i) analytical solutions to the transport-retention equations, ii) continuum -porous-medium numerical models, and iii) microstructure-based models accounting for small-scale heterogeneity (i.e. mineral grains, porosities and/or microfracture distributions) and potential centimetre-scale fractures. The modelling by the different teams led to some important conclusions, concerning for instance the presence of a disturbed zone (a few mm in thickness) next to the fracture surface and to the wall of the slim hole and the role of micro-fractures and cm-scale fractures in the transport of weakly sorbing tracers. These conclusions could be reached after the re-evaluation and revision of the experimental data (tracer profiles in the rock) and the analysis of the different sets of model results provided by the different teams.
|
|
| 5. |
- Sternby, Hanna, et al.
(författare)
-
Determinants of Severity in Acute Pancreatitis : A Nation-wide Multicenter Prospective Cohort Study
- 2019
-
Ingår i: Annals of Surgery. - 1528-1140. ; 270:2, s. 348-355
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of this study was to compare and validate the different classifications of severity in acute pancreatitis (AP) and to investigate which characteristics of the disease are associated with worse outcomes. SUMMARY OF BACKGROUND DATA: AP is a heterogeneous disease, ranging from uneventful cases to patients with considerable morbidity and high mortality rates. Severity classifications based on legitimate determinants of severity are important to correctly describe the course of disease. METHODS: A prospective multicenter cohort study involving patients with AP from 23 hospitals in Spain. The Atlanta Classification (AC), Revised Atlanta Classification (RAC), and Determinant-based Classification (DBC) were compared. Binary logistic multivariate analysis was performed to investigate independent determinants of severity. RESULTS: A total of 1655 patients were included; 70 patients (4.2%) died. RAC and DBC were equally superior to AC for describing the clinical course of AP. Although any kind of organ failure was associated with increased morbidity and mortality, persistent organ failure (POF) was the most significant determinant of severity. All local complications were associated with worse outcomes. Infected pancreatic necrosis correlated with high morbidity, but in the presence of POF, it was not associated to higher mortality when compared with sterile necrotizing pancreatitis. Exacerbation of previous comorbidity was associated with increased morbidity and mortality. CONCLUSION: The RAC and DBC both signify an advance in the description and differentiation of AP patients. Herein, we describe the complications of the disease independently associated to morbidity and mortality. Our findings are valuable not only when designing future studies on AP but also for the improvement of current classifications.
|
|
