| 1. |
- Glynn, Anders, et al.
(författare)
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Declining levels of PCB, HCB and p,p'-DDE in adipose tissue from food producing bovines and swine in Sweden 1991-2004
- 2009
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 74:11, s. 1457-1462
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Tidskriftsartikel (refereegranskat)abstract
- The official control programme for organochlorine (OC) contaminants in food producing animals in Sweden was used to study temporal and spatial trends of the polychlorinated biphenyl CB 153, hexachlorobenzene (HCB) and p,p'-DDE in adipose tissue from bovines and swine 1991-2004. Our results show that efforts to decrease OC contamination of animal feed and the environment have had a positive impact on the contamination of the animal production. OC concentrations declined significantly in almost all studied regions of Sweden. OC temporal trends were slower in bovines (6-8% per year) than in swine (10-12%). Power analyses showed that data from more than 10 years of sampling were needed for a detection of an annual OC level change of 5% in both species in the control programme, due to large within- and between-year variation in OC levels. CB 153 and p,p'-DDE levels were higher in southern than in northern Sweden. Levels decreased with age in milk cows, but not in young nulliparous cows (heifers) and bulls. Moreover, milk cows and bulls had significantly lower OC levels than heifers. Levels were not age-dependent among swine, but castrated male swine (barrows) had significantly lower OC levels than young female swine (gilts). Levels of the studied OCs are now in many cases below the LOQ of the analytical method used. Future time trend studies of these OCs thus depend on lowered LOQs in the control programme.
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| 2. |
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| 3. |
- Karlsson, Gunilla, et al.
(författare)
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Hospitalization and mortality succeeding drunk driving and risky driving
- 2003
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Ingår i: Alcohol and Alcoholism. - : Oxford University Press (OUP). - 0735-0414 .- 1464-3502. ; 38:3, s. 281-286
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Tidskriftsartikel (refereegranskat)abstract
- AIMS:The association between drunk driving (DD) and/or risky driving (RD) offences and subsequent hospitalization and mortality was studied during a 25-year period.METHODS:Information about drinking habits and psychosocial factors for the 8122 conscripts from Stockholm County in 1969-1970 was linked to register data on hospitalization, mortality, DD and RD.RESULTS:Analyses comparing background characteristics of DD and RD groups showed that the prevalence of problem behaviour and drug use was highest in the RD group. The relative risk (RR) for hospitalization after DD and/or RD was significantly elevated in multivariate logistic regression analysis for all the studied diagnostic categories (alcohol diagnoses, narcotic diagnoses, suicide attempts, psychoses, E-codes, all diagnoses), and was especially high for alcohol (RR = 7.2) and diagnosis of drug misuse (RR = 9.2). The RR of all hospitalization was 1.5 for the DD group, 1.8 for the RD group, and 1.9 for those who had been sentenced both for drunk driving and risky driving (DRD), all of which were significantly increased. The RR of death was significantly elevated in all three groups.CONCLUSIONS:The results show a significantly increased risk of hospitalization and mortality both in the DD and the RD group. From a public health and traffic safety perspective, this implies a need for developing and implementing better prevention strategies.
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| 4. |
- Akner, Gunnar, 1953-, et al.
(författare)
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Vi står gärna bakom en utfallsbaserad vård
- 2017
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Ingår i: Dagens Samhälle. - 1652-6511.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Jörgen Nordenström försöker få det till att vår kritik av värdebaserad vård egentligen handlar om att vi vill ha mer resurser. Han har helt missuppfattat oss, skriver 26 specialistläkare i en replik.
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| 5. |
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| 6. |
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| 7. |
- Amann, Peter, et al.
(författare)
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The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 376:6593, s. 603-608
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Tidskriftsartikel (refereegranskat)abstract
- The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO2/CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO2/CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO2 methanol synthesis.
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| 8. |
- Anders, Halldin, et al.
(författare)
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Improved osseointegration and interlocking capacity with dual acid treated implants: a rabbit study.
- 2016
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Ingår i: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 27, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- Aim To investigate how osseointegration is affected by different nano- and microstructures. The hypothesis was that the surface structure created by dual acid treatment (AT-1), applied on a reduced topography, might achieve equivalent biomechanical performance as a rougher surface treated with hydrofluoric acid (HF). Materials and methods In a preclinical rabbit study, three groups (I, II, and III) comprised of test and control implants were inserted in 30 rabbits. The microstructures of the test implants were either produced by blasting with coarse (I) or fine (II) titanium particles or remained turned (III). All test implants were thereafter treated with AT-1 resulting in three different test surfaces. The microstructure of the control implants was produced by blasting with coarse titanium particles thereafter treated with HF. The surface topography was characterized by interferometry. Biomechanical (removal torque) and histomorphometric (bone–implant contact; bone area) performances were measured after 4 or 12 weeks of healing. Results Removal torque measurement demonstrated that test implants in group I had an enhanced biomechanical performance compared to that of the control despite similar surface roughness value (Sa). At 4 weeks of healing, group II test implants showed equivalent biomechanical performance to that of the control, despite a decreased Sa value. Group III test implants showed decreased biomechanical performance to that of the control. Conclusions: The results of the present study suggest that nano- and microstructure alteration by AT-1 on a blasted implant might enhance the initial biomechanical performance, while for longer healing time, the surface interlocking capacity seems to be more important.
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| 9. |
- Berger, Urs, et al.
(författare)
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Fish consumption as a source of human exposure to perfluorinated alkyl substances in Sweden : analysis of edible fish from Lake Vättern and the Baltic Sea
- 2009
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 76:6, s. 799-804
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Tidskriftsartikel (refereegranskat)abstract
- Perfluorinated alkyl substances (PFAS) were analyzed in muscle tissue from edible fish species caught in the second largest freshwater lake in Sweden, Lake Vättern (LV), and in the brackish water Baltic Sea (BS). Perfluorooctane sulfonate (PFOS) was the predominant PFAS found. PFOS concentrations were higher in LV (medians 2.9-12 ng g(-1) fresh weight) than in BS fish (medians 1.0-2.5 ng g(-1) fresh weight). Moreover, LV fish was more contaminated with several other PFAS than BS fish. This may be due to anthropogenic discharges from urban areas around LV. The PFAS pattern differed between LV and BS fish, indicating different sources of contamination for the two study areas. Human exposure to PFOS via fish intake was calculated for three study groups, based on consumption data from literature. The groups consisted of individuals that reported moderate or high consumption of BS fish or high consumption of LV fish, respectively. The results showed that PFOS intake strongly depended on individual fish consumption as well as the fish catchment area. Median PFOS intakes were estimated to 0.15 and 0.62 ng kg(-1) body weight (bw) d(-1) for the consumers of moderate and high amounts of BS fish, respectively. For the group with high consumption of LV fish a median PFOS intake of 2.7 ng kg(-1)bw d(-1) was calculated. Fish consumption varied considerably within the consumer groups, with maximum PFOS intakes of 4.5 (BS fish) or 9.6 ng kg(-1)bw d(-1) (LV fish). Comparison of our results with literature data on PFOS intake from food suggests that fish from contaminated areas may be a significant source of dietary PFOS exposure.
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| 10. |
- Chowdhary, Ramesh, et al.
(författare)
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Evaluation of stress pattern generated through various thread designs of dental implants loaded in a condition of immediately after placement and on osseointegration : an FEA study
- 2013
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Ingår i: Implant Dentistry. - : Lippincott Williams & Wilkins. - 1056-6163 .- 1538-2982. ; 22:1, s. 91-96
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To determine the stress pattern generated through various thread design in experimental simulation models, when loaded immediately after placement and after osseointegration. METHODS: Three-dimensional (3D) models were designed using CATIA, computer-aided design modeling software. The study was planned in 2 stages. Eight 2D models were constructed of different thread forms, one set with frictionless and other with bonded for bone to implant interface and loaded vertically with 100 N. In Stage II, 6 3D models of the different threads embedded in the cortical bone were constructed and loaded vertically and obliquely. RESULTS: In 2D models, the von Mises stress concentrated at the crest in the bonded connection thread designs. The stress levels were in the range of 7 to 13 MPa. In the frictional implant bone interface, the thread designs had a clear effect on the stress levels in the bone. In the 3D analysis, the complete implant design affected the stress levels. CONCLUSIONS: The thread design affects the magnitude of the stress peak in the bone more effectively in immediately loaded (frictionless) implants than the osseointegrated (bonded) implants. Maximum stress was observed at the first thread in most of the osseointegrated implants.
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| 11. |
- Chowdhary, Ramesh, et al.
(författare)
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Influence of Micro Threads Alteration on Osseointegration and Primary Stability of Implants : An FEA and In Vivo Analysis in Rabbits
- 2015
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Ingår i: Clinical Implant Dentistry and Related Research. - : John Wiley & Sons. - 1523-0899 .- 1708-8208. ; 17:3, s. 562-569
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To describe the early bone tissue response to implants with and without micro threads designed to the full length of an oxidized titanium implant. MATERIALS AND METHODS: A pair of two-dimensional finite element models was designed using a computer aided three-dimensional interactive application files of an implant model with micro threads in between macro threads and one without micro threads. Oxidized titanium implants with (test implants n=20) and without (control implants n=20) micro thread were prepared. A total of 12 rabbits were used and each received four implants. Insertion torque while implant placement and removal torque analysis after 4 weeks was performed in nine rabbits, and histomorphometric analysis in three rabbits, respectively. RESULTS: Finite element analysis showed less stress accumulation in test implant models with 31Mpa when compared with 62.2 Mpa in control implant model. Insertion and removal torque analysis did not show any statistical significance between the two implant designs. At 4 weeks, there was a significant difference between the two groups in the percentage of new bone volume and bone-to-implant contact in the femur (p< .05); however, not in the tibia. CONCLUSIONS: The effect of micro threads was prominent in the femur suggesting that micro threads promote bone formation. The stress distribution supported by the micro threads was especially effective in the cancellous bone.
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| 12. |
- Eriksson, Olof, et al.
(författare)
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In vivo and in vitro characterization of [18F]-FE-(+)-DTBZ as a tracer for beta-cell mass
- 2010
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Ingår i: Nuclear Medicine and Biology. - : Elsevier BV. - 0969-8051 .- 1872-9614. ; 37:3, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: The positron emission tomography (PET) tracer 9-[(18)F]fluoroethyl-(+)-dihydrotetrabenazine ([(18)F]-FE-(+)-DTBZ) is a potential candidate for quantifying beta-cell mass in vivo. The purpose was to investigate in vitro and in vivo utility of this tracer for the assessment of beta-cell mass. METHODS: Three pigs were intravenously administered [(18)F]-FE-(+)-DTBZ and examined by PET/computed tomography. Binding parameters were estimated by kinetic modeling. In vitro k(D) and B(max) were determined by saturation binding studies of endocrine and exocrine human tissue homogenates. In vitro pancreatic uptake was determined by tissue autoradiography with pancreases from patients with types 1 (T1DM) and 2 diabetes mellitus (T2DM) and healthy controls. RESULTS: [(18)F]-FE-(+)-DTBZ had a k(D) of 3.5+/-1.0 nM, a B(max) of 382+/-108 fmol/mg protein and a specificity of 89+/-1.8% in islet homogenates. The total exocrine uptake was lower and 65% was nondisplaceable. No uptake difference was observed in pancreatic tissue slices from patients with T1DM, T2DM or healthy controls. The in vivo porcine pancreatic uptake reached a peak of standardized uptake value (SUV) of 2.8 with a low distribution volume ratio in all animals. Moderate to high tracer uptake was identified in the bile system and in bone. CONCLUSIONS: [(18)F]-FE-(+)-DTBZ binds to vesicular monoamine transporter 2 (VMAT2) with high specificity in pure islet tissue in vitro. However, there is high nondisplaceable binding to exocrine tissue. In addition, in vivo tracer metabolism and dehalogenation result in severe underestimation of porcine pancreatic VMAT2 expression and BCM. The results do not support [(18)F]-FE-(+)-DTBZ as a suitable tracer for in vivo beta-cell imaging.
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| 13. |
- Forsberg, Anton, et al.
(författare)
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Low background and high contrast PET imaging of amyloid-β with [11C]AZD2995 and [11C]AZD2184 in Alzheimer's disease patients
- 2013
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Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer-Verlag New York. - 1619-7070 .- 1619-7089. ; 40:4, s. 580-593
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The aim of this study was to evaluate AZD2995 side by side with AZD2184 as novel PET radioligands for imaging of amyloid-β in Alzheimer's disease (AD).METHODS: In vitro binding of tritium-labelled AZD2995 and AZD2184 was studied and compared with that of the established amyloid-β PET radioligand PIB. Subsequently, a first-in-human in vivo PET study was performed using [(11)C]AZD2995 and [(11)C]AZD2184 in three healthy control subjects and seven AD patients.RESULTS: AZD2995, AZD2184 and PIB were found to share the same binding site to amyloid-β. [(3)H]AZD2995 had the highest signal-to-background ratio in brain tissue from patients with AD as well as in transgenic mice. However, [(11)C]AZD2184 had superior imaging properties in PET, as shown by larger effect sizes comparing binding potential values in cortical regions of AD patients and healthy controls. Nevertheless, probably due to a lower amount of nonspecific binding, the group separation of the distribution volume ratio values of [(11)C]AZD2995 was greater in areas with lower amyloid-β load, e.g. the hippocampus.CONCLUSION: Both AZD2995 and AZD2184 detect amyloid-β with high affinity and specificity and also display a lower degree of nonspecific binding than that reported for PIB. Overall [(11)C]AZD2184 seems to be an amyloid-β radioligand with higher uptake and better group separation when compared to [(11)C]AZD2995. However, the very low nonspecific binding of [(11)C]AZD2995 makes this radioligand potentially interesting as a tool to study minute levels of amyloid-β. This sensitivity may be important in investigating, for example, early prodromal stages of AD or in the longitudinal study of a disease modifying therapy.
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| 14. |
- Glynn, Anders, et al.
(författare)
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Regional differences in levels of chlorinated and brominated pollutants in mother's milk from primiparous women in Sweden.
- 2011
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Ingår i: Environment international. - : Elsevier BV. - 1873-6750 .- 0160-4120. ; 37:1, s. 71-9
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Tidskriftsartikel (refereegranskat)abstract
- Early life exposure to halogenated persistent organic pollutants, such as polychlorinated biphenyls (PCBs), the DDT metabolite p,p'-dichlorodiphenyldichloroethane (p,p'-DDE), polybrominated diphenylethers (PBDEs), and hexabromocyclododecane (HBCD), may affect human health. We determined if there are regional differences in mother's milk levels of these compounds in Sweden. In year 2000-2004, milk was sampled from 204 randomly recruited primiparas from four regions of Sweden. Levels of the compounds were measured by gas chromatography with dual electron-capture detectors. Women were recruited at delivery in three hospitals located in urban areas in southern and central Sweden (Lund, Gothenburg and Uppsala), and in one hospital located in a more rural area in northern Sweden (Lycksele). Information about dietary habits and medical/life-style factors were collected by questionnaires. Among PCB congeners, CB 153, CB 138 and CB 180 showed the highest median concentrations (18-48 ng/g mother's milk lipid), whereas more than 50% of the women had CB 52, CB 101, CB 114, and CB 157 levels below the LOQ (0.3-1.5 ng/g lipid). Median p,p'-DDE levels were in the range of 46-78 ng/g lipid. BDE 47 showed the highest median concentrations (1-2 ng/g lipid) among the brominated compounds, whereas more than 50% of the women had levels of BDE 28, BDE 66, BDE 138, BDE 154, and HBCD below the LOQ (0.05-0.10 ng/g lipid). Regional differences in median organohalogen compound concentrations were small, less than 2-fold. Lycksele women generally had the lowest levels of Σmono-and Σdi-ortho PCBs, mainly due to a lower average age. In contrast, these women had higher tetra- to penta-brominated PBDE levels, but no diet or life-style factor could explain this finding. Wide ranges of PBDEs and HBCD levels (up to 200-fold) were found, especially in the Lycksele area. The highest levels of PBDE were in the range of average levels found in mother's milk from North America, suggesting that food may not be the only source of exposure to PBDEs among some individuals.
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| 15. |
- Gryning, SE, et al.
(författare)
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Area averaging of land surface-atmosphere fluxes in NOPEX: challenges, results and perspectives
- 2002
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Ingår i: Boreal Environment Research: An International Interdisciplinary Journal. - 1239-6095. ; 7:4, s. 379-387
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Tidskriftsartikel (refereegranskat)abstract
- The NOPEX experimental campaigns dealt with the land-surface-atmosphere exchange of momentum, heat, water and CO2 on local and regional scales. In this paper emphasis is put on the NOPEX experiences with respect to the spatial integration of fluxes of momentum, heat, humidity and CO2 over the mosaic of forest, agricultural land, lakes and mires that make up the southern part of the NOPEX area. It is found that the forest dominates both the regional momentum and heat fluxes but in very different ways. Furthermore, results from a NOPEX experiment in the northern zone of the boreal forest in Finnish Lapland highlights the very unique processes associated with the energy exchange within a forest in wintertime. The interaction of the forest canopy with sunshine provides a considerable energy source, particularly at low solar angles. A considerable improvement in model simulations of fluxes and surface temperature was achieved when this effect and the heat storage of the canopy were taken into account.
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| 16. |
- Gustafsson, David, et al.
(författare)
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Boreal forest surface parameterization in the ECMWF model - 1D test with NOPEX long-term data
- 2003
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Ingår i: Journal of applied meteorology (1988). - 0894-8763 .- 1520-0450. ; 42:1, s. 95-112
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present study was to assess the performance and recent improvements of the land surface scheme used operationally in the European Centre for Medium-Range Weather Forecasts (ECMWF) in a Scandinavian boreal forest climate/ecosystem. The previous (the 1999 scheme of P. Viterbo and A. K. Betts) and the new (Tiled ECMWF Surface Scheme for Exchange Processes over Land, TESSEL) surface schemes were validated by single-column runs against data from NOPEX (Northern Hemisphere Climate-Processes Land-Surface Experiment). Driving and validation datasets were prepared for a 3-yr period (1994-96). The new surface scheme, with separate surface energy balances for subgrid fractions (tiling), improved predictions of seasonal as well as diurnal variation in surface energy fluxes in comparison with the old scheme. Simulated wintertime evaporation improved significantly as a consequence of the introduced additional aerodynamic resistance for evaporation from snow lying under high vegetation. Simulated springtime evaporation also improved because the limitation of transpiration in frozen soils was now accounted for. However, downward sensible heat flux was still underestimated during winter, especially at nighttime, whereas soil temperatures were underestimated in winter and overestimated in summer. The new scheme also underestimated evaporation during dry periods in summer, whereas soil moisture was overestimated. Sensitivity tests showed that further improvements of simulated surface heat fluxes and soil temperatures could be obtained by calibration of parameters governing the coupling between the surface and the atmosphere and the ground heat flux, and parameters governing the water uptake by the vegetation. Model performance also improved when the seasonal variation in vegetation properties was included.
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| 17. |
- Görlin, Mikaela, et al.
(författare)
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Key activity descriptors of nickel-iron oxygen evolution electrocatalysts in the presence of alkali metal cations
- 2020
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Efficient oxygen evolution reaction (OER) electrocatalysts are pivotal for sustainable fuel production, where the Ni-Fe oxyhydroxide (OOH) is among the most active catalysts for alkaline OER. Electrolyte alkali metal cations have been shown to modify the activity and reaction intermediates, however, the exact mechanism is at question due to unexplained deviations from the cation size trend. Our X-ray absorption spectroelectrochemical results show that bigger cations shift the Ni2+/(3+delta)+ redox peak and OER activity to lower potentials (however, with typical discrepancies), following the order CsOH>NaOH approximate to KOH>RbOH>LiOH. Here, we find that the OER activity follows the variations in electrolyte pH rather than a specific cation, which accounts for differences both in basicity of the alkali hydroxides and other contributing anomalies. Our density functional theory-derived reactivity descriptors confirm that cations impose negligible effect on the Lewis acidity of Ni, Fe, and O lattice sites, thus strengthening the conclusions of an indirect pH effect. It is commonly accepted that electrolyte alkali metal cations modify the catalytic activity for oxygen evolution reaction. Here the authors challenge this assumption, showing that the activity is actually affected by a change in the electrolyte pH rather than a specific alkali cation.
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| 18. |
- Halldin, Anders, et al.
(författare)
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Implant Stability and Bone Remodeling after 3 and 13 Days of Implantation with an Initial Static Strain
- 2014
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Ingår i: Clinical Implant Dentistry and Related Research. - : John Wiley & Sons. - 1523-0899 .- 1708-8208. ; 16:3, s. 383-393
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Tidskriftsartikel (refereegranskat)abstract
- Objective Bone is constantly exposed to dynamic and static loads, which induce both dynamic and static bone strains. Although numerous studies exist on the effect of dynamic strain on implant stability and bone remodeling, the effect of static strain needs further investigation. Therefore, the effect of two different static bone strain levels on implant stability and bone remodeling at two different implantation times was investigated in a rabbit model. Methods Two different test implants with a diametrical expansion of 0.15 mm (group A) and 0.05 mm (group B) creating initial static bone strains of 0.045 and 0.015, respectively. The implants were inserted in the proximal tibial metaphysis of 24 rabbits to observe the biological response at implant removal. Both groups were compared to control implants (group C), with no diametrical increase. The insertion torque (ITQ) was measured to represent the initial stability and the removal torque (RTQ) was measured to analyze the effect that static strain had on implant stability and bone remodeling after 3 and 13 days of implantation time. Results The ITQ and the RTQ values for test implants were significantly higher for both implantation times compared to control implants. A selection of histology samples was prepared to measure bone to implant contact (BIC). There was a tendency that the BIC values for test implants were higher compared to control implants. Conclusion These findings suggest that increased static bone strain creates higher implant stability at the time of insertion, and this increased stability is maintained throughout the observed period.
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| 19. |
- Halldin, Anders
(författare)
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On a biomechanical approach to analysis of stability and load bearing capacity of oral implants
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionWhen an implant is placed in the bone the body responds to thetrauma by encapsulating the implant and its survival depends onthe ability for hard tissue encapsulation. The stability of the implantduring the healing phase is essential to achieve a good result[1]. Biological, physiological and mechanical phenomena affectimplant stability. To achieve sufficient stability during the initialhealing phase the implant has to provide sufficient static interactionwith the bone. The static interaction might affect the biologicalprocesses that in turn affect implant stability. Although, numerousstudies on the effect of dynamic interaction on implant stabilityand bone remodeling exist, the effect of static strain has yetto be clarified.As the healing progresses it may result in bone formation in closecontact with the implant (i.e osseointegration) that stabilizes theimplant. It has been found that implant surface modifications atthe micro level promote osseointegration and that moderatelyroughened implants provide rapid and strong bone response [2, 3].In addition, the application of nanostructures to an implant surfacehas been shown to elicit an initial complex gene response that mayresult in further enhancement in bone formation around the implant[4]. Furthermore the implant surface structure interlocks mechanicallywith the bone that affects the stability of the implant.The implant surface design has to take into account both biologicaland mechanical behavior of the tissues.Materials and methodsTo investigate how implant stability and the biological responseare affected by an induced static load to the bone an in vivo studywas performed. Two types of controlled static loads, excessive andmoderate, were induced by specially designed implants. Two typesof surface structure, turned and blasted, were applied on the implants.The implants were inserted in rabbits and healed for 3-84days before the stability was measured by removal torque.To simulate how the pressure changes, due to biological and mechanicalphenomena, on an implant surface that was subjected toan initial pressure, a constitutive model was developed that wascomprised of visco-elastic, visco-plastic and remodeling components.The pressure on the surface in turn affects the implant stability.To investigate how the biomechanical and the biological responsesare affected by the surface structure an in vivo study and a finiteelement analysis of the theoretical interfacial shear strength wereperformed. In the pre-clinical study, three groups of implants withdifferent nano- and microstructures were compared to an implantwith a control surface structure.The theoretical interfacial strength at different healing times wasestimated by simulating the surface structure interlocking capacityto bone using an explicit finite element method. Simulations wereperformed for different surface structures and for different pressures,simulating visco-elastic and remodeling phenomena.ResultsImplants that induced a moderate bone condensation in the bonehad a significantly higher removal torque value at the implantationtimes of 3-24 days compared to implants that did not induce condensation.The effect the induced moderate bone condensation hadon implant stability decreases over time until the pressure has vanished,which approximately occurred after 28-30 days. Turned implants,placed in tibia, that induced excessive bone condensationresulted in significant increased implant stability at implantationtimes of 3-24 days compared to implants that induced no condensation.However, when they were placed in femur it provided nosignificant difference in removal torque at an implantation time of24 days compared to implants that induced no condensation.The developed constitutive model is able to capture visco-elasticmaterial behavior and remodeling phenomena of cortical bonewhich can be used to simulate how the pressure changes on an implantsurface that is subjected to an initial pressure caused by condensation.The implant nano- and microsurface structure affects the magnitudeof the removal torque value. It was found that implants, withno significant difference in surface roughness parameters (Sa, Ssk,Sdr) on micro level, can present a significant difference in removaltorque value at 4 weeks of implantation time. In addition, it wasalso found that implants with a significant difference in surfaceroughness parameters (Sa, Ssk, Sdr) can present no significant differencein removal torque value at 4 weeks of implantation times. Thedifference may be due to various biological responses from thenano- and microstructure surfaces.The simulated interfacial strength for the different surfaces did notreach the interfacial strength that corresponds to the removaltorque obtained in the in vivo study. Comparing the two surfaces in respect of removal torque ratio, suggests that during the earlyhealing phase the difference is caused by different bone formationrates from biological processes. As the healing progresses the effectof structural interlocking capacity is more pronounced.ConclusionsThe results suggest that increased static strain in the bone not onlycreates higher implant stability at the time of insertion, but alsogenerates increased implant stability throughout the observationperiod of 3-24 days. The proposed constitutive material model consists of three differentcomponents: a visco-elastic component, a visco-plastic componentand a remodeling component. The model captures with goodagreement the experimental behavior of cortical bone during differentlongitudinal loading situations i.e. in vitro stress-strain relationship,in vivo relaxation, in vitro creep and in vivo remodeling.The results of the present study suggest that nano- and microstructurealteration on a blasted implant might enhance the initial biomechanicalperformance, while for longer healing times, the surfaceinterlocking capacity seems to be more important.Simulation of the interfacial shear strength by means of finite elementanalysis seems to be a promising method to estimate the loadbearing capacity of the bone-to-implant interface for different surfacestructures at stable healing conditions i.e. longer healing times.Furthermore, it is a promising method to estimate the implant stabilityfor different magnitudes of condensation.
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| 20. |
- Halldin, Anders, 1971, et al.
(författare)
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On a Constitutive Material Model to Capture Time Dependent Behaviour of Cortical Bone
- 2014
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Ingår i: World Journal of Mechanics. - : Scientific Research Publishing, Inc.. - 2160-049X .- 2160-0503. ; 4:11, s. 348-361
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Tidskriftsartikel (refereegranskat)abstract
- It is commonly known that cortical bone exhibits viscoelastic-viscoplastic behavior which affects the biomechanical response when an implant is subjected to an external load. In addition, long term effects such as creep, relaxation and remodeling affect the success of the implant over time. Constitutive material models are commonly derived from data obtained in in vitro experiments. However during function, remodeling of bone greatly affects the bone material over time. Hence it is essential to include long term in vivo effects in a constitutive model of bone. This paper proposes a constitutive material model for cortical bone incorporating viscoelasticity, viscoplasticity, creep and remodeling to predict stress-strain at various strain rates as well as the behavior of bone over time in vivo. The rheological model and its parameters explain the behavior of bone subjected to longitudinal loading. By a proper set of model parameters, for a specific cortical bone, the present model can be used for prediction of the behavior of this bone under specific loading conditions. In addition simulation with the proposed model demonstrates excellent agreement to in vitro and in vivo experimental results in the literature.
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| 21. |
- Halldin, Anders, et al.
(författare)
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The effect of static bone strain on implant stability of bone remodelling
- 2011
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Ingår i: Bone. - : Elsevier. - 8756-3282 .- 1873-2763. ; 49:4, s. 783-789
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Tidskriftsartikel (refereegranskat)abstract
- Bone remodeling is a process involving both dynamic and static bone strain. Although there exist numerous studies on the effect of dynamic strain on implant stability and bone remodeling, the effect of static strain has yet to be clarified. Hence, for this purpose, the effect of static bone strain on implant stability and bone remodeling was investigated in rabbits. Based on Finite Element (FE) simulation two different test implants, with a diametrical increase of 0.15 mm (group A) and 0.05 mm (group B) creating static strains in the bone of 0.045 and 0.015 respectively, were inserted in the femur (group A) and the proximal tibia metaphysis (groups A and B respectively) of 14 rabbits to observe the biological response. Both groups were compared to control implants, with no diametrical increase (group C), which were placed in the opposite leg. At the time of surgery, the insertion torque (ITQ) was measured to represent the initial stability. The rabbits were euthanized after 24 days and the removal torque (RTQ) was measured to analyze the effect on implant stability and bone remodeling. The mean ITQ value was significantly higher for both groups A and B compared to group C regardless of the bone type. The RTQ value was significantly higher in tibia for groups A and B compared to group C while group A placed in femur presented no significant difference compared to group C. The results suggest that increased static strain in the bone not only creates higher implant stability at the time of insertion, but also generates increased implant stability throughout the observation period.
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| 22. |
- Halldin, Anders, et al.
(författare)
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The effect of static strain
- 2012
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Ingår i: AstraTech World Congress, May 9-12, 2012, Göteborg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 23. |
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| 24. |
- Halldin Stenlid, Maria U., et al.
(författare)
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Increased lipolysis in LCHAD deficiency
- 2007
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Ingår i: Journal of Inherited Metabolic Disease. - : Wiley. - 0141-8955 .- 1573-2665. ; 30:1, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of fatty acid oxidation defects are being detected owing to diagnostic improvements and a greater awareness among clinicians. The metabolic block leads to energy disruption, fatty infiltration, and toxic effects on organ functions exerted by β-oxidation metabolites. This investigation was undertaken to assess the influence of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency on lipolysis and energy turnover. We addressed the question whether the lipolysis and glucose production rates would be altered in the fasting state in a child with this disease. Lipolysis, glucose production and resting energy expenditure (REE) were studied in a 17-month-old girl with LCHAD deficiency and her healthy twin sister. Lipolysis and glucose production were determined after a 4–6 h fast by constant-rate infusion of [1,1,2,3,3-2H5]glycerol and [6,6-2H2]glucose and analysis by gas chromatography–mass spectrometry. REE was estimated by indirect calorimetry. The affected girl showed 50% higher lipolysis than did her sister, whereas the glucose production rates were similar. Plasma levels of dicarboxylic acids of 6–12 carbon atoms chain length, 3-hydroxy fatty acids of 6–18 carbon atoms chain length, total free fatty acids, and acylcarnitines were increased in the patient, as was REE. Since glucose production rates and plasma glucose levels were similar in the two girls, the increased lipolysis observed in the patient probably represents a compensatory mechanism for energy generation. This is achieved at the price of an augmented risk for fatty acid infiltration and toxic effects of β-oxidation intermediates. This highlights the importance of avoiding fasting in these patients.
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| 25. |
- Jahan, Mahabuba, et al.
(författare)
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Decreased defluorination by using the novel beta cell imaging agent [18F]FE-DTBZ-d4 in pigs examined by PET
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Fluorine-18 DTBZ-analogues, which selectively targets the vesicular monoamine transporter 2 (VMAT2), have been extensively studied for in vivo quantification of beta cell mass by positron emission tomography (PET). This study describes a novel deuterated radioligand [18F]FE-(+)-DTBZ-d4, aimed to increase the stability against in vivo defluorination previously observed for [18F]FE-(+)-DTBZ. Methods: [18F]FE-(+)-DTBZ-d4 was synthesized by alkylation of desmethyl -(+)-DTBZ precursor with deuterated [18F]fluoroethyl bromide ([18F]FCD2CD2Br). Radioligand affinity and specificity to VMAT2 was assessed by an in vitro saturation homogenate binding assay using human endocrine and exocrine pancreatic tissues. In vivo PK/PD was studied in a porcine model by PET/CT. The rate of defluorination was quantified by compartmental modeling and contrasted against defluorination of the non-deuterated analogue. Results: [18F]FE-DTBZ-d4 was produced in good radiochemical yield (3.0-1.7 GBq) in 100 min. Radiochemical purity of the formulated product was > 98% for up to 5h. The in vitro Binding Potential (BP) for VMAT2 in islet tissue was 27.0±8.8. The BP was lower in exocrine tissue (1.7±1.0) in addition to a close to three-fold decrease in specificity. The rate of in vivo defluorination was decreased significantly (kdefluorination= 0.0016±0.0007) compared to the non-deuterated analogue (kdefluorination= 0.012±0.002), resulting in a more than six-fold increase in half-life stability. Conclusion: [18F]FE-(+)-DTBZ-d4 has favorable pharmacokinetic (PK) properties for VMAT2 imaging, in addition to gaining significantly increased stability against defluorination. The in vitro islet BP and specificity was lower compared to a non-deuterated analogue but the islet/exocrine BP ratio was unchanged, potentially allowing for improved target tissue discrimination.
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| 26. |
- Jahan, Mahabuba, et al.
(författare)
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Decreased defluorination using the novel beta-cell imaging agent [18F]FE-DTBZ-d4 in pigs examined by PET
- 2011
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Ingår i: EJNMMI Research. - 2191-219X. ; 54, s. S137-S137
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundFluorine-18 dihydrotetrabenazine [DTBZ] analogues, which selectively target the vesicular monoamine transporter 2 [VMAT2], have been extensively studied for in vivo quantification of beta cell mass by positron-emission tomography [PET]. This study describes a novel deuterated radioligand [18F]fluoroethyl [FE]-DTBZ-d4, aimed to increase the stability against in vivo defluorination previously observed for [18F]FE-DTBZ.Methods[18F]FE-DTBZ-d4 was synthesized by alkylation of 9-O-desmethyl-(+)-DTBZ precursor with deuterated [18F]FE bromide ([18F]FCD2CD2Br). Radioligand binding potential [BP] was assessed by an in vitro saturation homogenate binding assay using human endocrine and exocrine pancreatic tissues. In vivo pharmacokinetics and pharmacodynamics [PK/PD] was studied in a porcine model by PET/computed tomography, and the rate of defluorination was quantified by compartmental modeling.Results[18F]FE-DTBZ-d4 was produced in reproducible good radiochemical yield in 100 ± 20 min. Radiochemical purity of the formulated product was > 98% for up to 5 h with specific radioactivities that ranged from 192 to 529 GBq/μmol at the end of the synthesis. The in vitro BP for VMAT2 in the islet tissue was 27.0 ± 8.8, and for the exocrine tissue, 1.7 ± 1.0. The rate of in vivo defluorination was decreased significantly (kdefluorination = 0.0016 ± 0.0007 min-1) compared to the non-deuterated analogue (kdefluorination = 0.012 ± 0.002 min-1), resulting in a six fold increase in half-life stability.Conclusions[18F]FE-DTBZ-d4 has similar PK and PD properties for VMAT2 imaging as its non-deuterated analogue [18F]FE-DTBZ in addition to gaining significantly increased stability against defluorination. [18F]FE-DTBZ-d4 is a prime candidate for future preclinical and clinical studies on focal clusters of beta cells, such as in intramuscular islet grafts.
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| 27. |
- Jimbo, Ryo, et al.
(författare)
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Vertical fracture and marginal bone loss of internal-connection implants : a finite element analysis
- 2013
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Ingår i: International Journal of Oral & Maxillofacial Implants. - : Quintessence. - 0882-2786 .- 1942-4434. ; 28:4, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Marginal bone loss around implants is of great concern, and its cause may be multifactorial. Recently, clinical cases presenting marginal bone loss, in most cases accompanied by vertical fracture of internal-connection implants in the buccolingual direction, have been reported, in which unfavorable stress distribution is one possible cause of marginal bone resorption. The purpose of the current study was to characterize this type of marginal bone loss and implant fracture by conducting a finite element analysis (FEA). MATERIALS AND METHODS: Clinical and radiographic evaluations showed that the prostheses of all reported cases had implant-level setups and were directly screwed to the internal implants. Intriguingly, all vertical fractures reported were in the buccolingual direction. Therefore, to characterize the specific implant fractures, FEA was conducted with misfit models created for two different setups, abutment-level and implant-level, both with screw-retained prostheses. The models were subjected to initial misfits of 0 μm (representing perfect fit), 50 μm, 100 μm, 150 μm, or 200 μm, and vertical loading was then applied. RESULTS: FEA revealed that, for the implant-level setup, excessive stress at the neck of the implant gradually increased in the buccolingual direction as the misfit increased. This result was not seen for the abutment-level setup. A broad maximum stress distribution was evident for the implant-level setup but not for the abutment-level setup. CONCLUSION: Broad distribution of excessive stress in the FEA correlated to the clinical cases, and marginal bone loss in these cases may be associated with mechanical alterations. To avoid unnecessary complications, selection of an abutment-level setup is strongly suggested.
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| 28. |
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| 29. |
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| 30. |
- Koroidov, Sergey, et al.
(författare)
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Chemisorbed oxygen or surface oxides steer the selectivity in Pd electrocatalytic propene oxidation observed by operando Pd L-edge X-ray absorption spectroscopy
- 2021
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 11:10, s. 3347-3352
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Tidskriftsartikel (refereegranskat)abstract
- Controlled electrochemical oxidation of hydrocarbons to desired products is an attractive approach in catalysis. Here we study the electrochemical propene oxidation under operando conditions using Pd L-edge X-ray absorption spectroscopy (XAS) as a sensitive probe to elucidate surface processes occurring during catalysis. Together with ab initio multiple-scattering calculations, our XAS results enable assignment of characteristic changes of the Pd L-edge intensity and energy position in terms of a mechanistic understanding of the selective oxidation of propene. The results, supported by electrochemical density functional theory DFT simulations, show that in the potential range of 0.8–1.0 V vs. the reversible hydrogen electrode (RHE), selective oxidation of propene to acrolein and acrylic acid occurs on the metallic Pd surface. These reactions are proposed to proceed via the Langmuir–Hinshelwood mechanism. In contrast, for the potential range of 1.1–1.3 V vs. RHE, selective oxidation of propene to propylene glycol takes place on a Pd oxide surface.
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| 31. |
- Nordén, Marcus, 1982-
(författare)
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Comparative avian developmental toxicity of PFAAs
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Perfluoroalkyl acids (PFAAs) are persistent organic pollutants that can commonly be found in environmental matrixes and wildlife from all over the globe. The PFAAs have been used in applications such as water and dirt repelling treatments for textiles, oil-resistant paper coatings and fire-fighting foams. Four studies were designed to evaluate the occurrence of PFAAs in Swedish populations of birds, the developmental toxicity of different PFAAs and species sensitivity differences as well as possible modes of action for the toxicity. The studied species were domestic chicken, and the wild species great cormorant and herring gull. Cormorant and gull eggs were collected from bird colonies in Lake Vänern, Sweden. Chemical analyses were performed on some of the eggs to determine the occurrence of 15 PFAAs in the eggs. The other eggs and eggs of domestic chicken were incubated and injected with solutions of the PFAAs PFOS, PFOA, PFBS and PFUnDA. The eggs were candled every 1-3 days to determine viability. High levels of PFAAs, mainly PFOS followed by PFUnDA, were found in the herring gull and great cormorant eggs. PFOS was found at concentrations up to 1163 ng/g and 771 ng/g in cormorant and herring gull, respectively. In the toxicity tests, chicken was found to be more sensitive than the wild species and cormorant was in general the least sensitive species. PFOA was found to be the most toxic of the chemicals followed by PFOS, PFBS and PFUnDA in decreasing order. Comparing these results with the levels of these chemicals found in the eggs of herring gull and great cormorant, PFOS is the chemical of most concern. Although PFOA had the highest toxicity, the levels found in the eggs were very low. In an additional study, the hepatic β-oxidation in developing chicken embryos after in ovo exposure to PFOS was studied with a tritium release assay. PFOS was found to increase the β-oxidation of palmitic acid at PFOS concentrations 3-7 times lower than the average egg levels in cormorant and herring gull. Therefore the occurrence of effects on the fatty acid metabolism cannot be ruled out. The doses of effect on embryo survival in the toxicity and the levels found in the herring gulls and cormorants gives a small margin of safety for the wild populations. Continued environmental monitoring and further studies on the toxicity of PFAAs that occur at high environmental concentrations is important.
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| 32. |
- Paul-Visse, Gesine, et al.
(författare)
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Safety and tolerability of intracerebroventricular PDGF-BB in Parkinson's disease patients
- 2015
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Ingår i: Journal of Clinical Investigation. - 0021-9738 .- 1558-8238. ; 125:3, s. 1339-1346
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND. Recombinant human PDGF-BB (rhPDGF-BB) reduces Parkinsonian symptoms and increases dopamine transporter (DAT) binding in several animal models of Parkinson's disease (PD). Effects of rhPDGF-BB are the result of proliferation of ventricular wall progenitor cells and reversed by blocking mitosis. Based on these restorative effects, we assessed the safety and tolerability of intracerebroventricular (i.c.v.) rhPDGF-BB administration in individuals with PD. METHODS. We conducted a double-blind, randomized, placebo-controlled phase I/IIa study at two clinical centers in Sweden. Twelve patients with moderate PD received rhPDGF-BB via an implanted drug infusion pump and an investigational i.c.v. catheter. Patients were assigned to a dose cohort (0.2, 1.5, or 5 mu g rhPDGF-BB per day) and then randomized to active treatment or placebo (3:1) for a 12-day treatment period. The primary objective was to assess safety and tolerability of i.c.v.-delivered rhPDGF-BB. Secondary outcome assessments included several clinical rating scales and changes in DAT binding. The follow-up period was 85 days. RESULTS. All patients completed the study. There were no unresolved adverse events. Serious adverse events occurred in three patients; however, these were unrelated to rhPDGF-BB administration. Secondary outcome parameters did not show dose-dependent changes in clinical rating scales, but there was a positive effect on DAT binding in the right putamen. CONCLUSION. At all doses tested, i.c.v. administration of rhPDGF-BB was well tolerated. Results support further clinical development of rhPDGF-BB for patients with PD.
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| 33. |
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| 34. |
- Schain, Martin, et al.
(författare)
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Arterial input function derived from pairwise correlations between PET-image voxels
- 2013
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Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : Nature Publishing Group. - 0271-678X .- 1559-7016. ; 33:7, s. 1058-1065
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Tidskriftsartikel (refereegranskat)abstract
- A metabolite corrected arterial input function is a prerequisite for quantification of positron emission tomography (PET) data by compartmental analysis. This quantitative approach is also necessary for radioligands without suitable reference regions in brain. The measurement is laborious and requires cannulation of a peripheral artery, a procedure that can be associated with patient discomfort and potential adverse events. A non invasive procedure for obtaining the arterial input function is thus preferable. In this study, we present a novel method to obtain image-derived input functions (IDIFs). The method is based on calculation of the Pearson correlation coefficient between the time-activity curves of voxel pairs in the PET image to localize voxels displaying blood-like behavior. The method was evaluated using data obtained in human studies with the radioligands [11C]flumazenil and [11C]AZ10419369, and its performance was compared with three previously published methods. The distribution volumes (VT) obtained using IDIFs were compared with those obtained using traditional arterial measurements. Overall, the agreement in VT was good (~3% difference) for input functions obtained using the pairwise correlation approach. This approach performed similarly or even better than the other methods, and could be considered in applied clinical studies. Applications to other radioligands are needed for further verification.
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| 35. |
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| 36. |
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| 37. |
- Schreck, Simon, et al.
(författare)
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Atom-Specific Probing of Electron Dynamics in an Atomic Adsorbate by Time-Resolved X-Ray Spectroscopy
- 2022
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 129:27
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Tidskriftsartikel (refereegranskat)abstract
- The electronic excitation occurring on adsorbates at ultrafast timescales from optical lasers that initiate surface chemical reactions is still an open question. Here, we report the ultrafast temporal evolution of x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) of a simple well-known adsorbate prototype system, namely carbon (C) atoms adsorbed on a nickel [Ni(100)] surface, following intense laser optical pumping at 400 nm. We observe ultrafast (∼100 fs) changes in both XAS and XES showing clear signatures of the formation of a hot electron-hole pair distribution on the adsorbate. This is followed by slower changes on a few picoseconds timescale, shown to be consistent with thermalization of the complete C/Ni system. Density functional theory spectrum simulations support this interpretation.
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| 38. |
- Stenlid, Maria Halldin, 1957-, et al.
(författare)
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Energy substrate metabolism in pyruvate dehydrogenase complex deficiency
- 2014
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Ingår i: Journal of Pediatric Endocrinology & Metabolism (JPEM). - : Walter de Gruyter GmbH. - 0334-018X .- 2191-0251. ; 27:11-12, s. 1059-1064
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Tidskriftsartikel (refereegranskat)abstract
- Pyruvate dehydrogenase (PDH) deficiency is an inherited disorder of carbohydrate metabolism, resulting in lactic acidosis and neurological dysfunction. In order to provide energy for the brain, a ketogenic diet has been tried. Both the disorder and the ketogenic therapy may influence energy production. The aim of the study was to assess hepatic glucose production, lipolysis and resting energy expenditure (REE) in an infant, given a ketogenic diet due to neonatal onset of the disease. Lipolysis and glucose production were determined for two consecutive time periods by constant-rate infusions of [1,1,2,3,3-2H5]-glycerol and [6,6-2H2]-glucose. The boy had been fasting for 2.5 h at the start of the sampling periods. REE was estimated by indirect calorimetry. Rates of glucose production and lipolysis were increased compared with those of term neonates. REE corresponded to 60% of normal values. Respiratory quotient (RQ) was increased, indicating a predominance of glucose oxidation. Blood lactate was within the normal range. Several mechanisms may underlie the increased rates of glucose production and lipolysis. A ketogenic diet will result in a low insulin secretion and reduced peripheral and hepatic insulin sensitivity, leading to increased production of glucose and decreased peripheral glucose uptake. Surprisingly, RQ was high, indicating active glucose oxidation, which may reflect a residual enzyme activity, sufficient during rest. Considering this, a strict ketogenic diet might not be the optimal choice for patients with PDH deficiency. We propose an individualised diet for this group of patients aiming at the highest glucose intake that each patient will tolerate without elevated lactate levels.
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| 39. |
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| 40. |
- Stenlid, Rasmus, et al.
(författare)
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High DPP-4 concentrations in adolescents are associated with low intact GLP-1
- 2018
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : Endocrine Society. - 0021-972X .- 1945-7197. ; 103:8, s. 2958-2966
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Tidskriftsartikel (refereegranskat)abstract
- Context: Dipeptidyl Peptidase-4 (DPP-4) metabolizes glucagon-like peptide-1 (GLP-1) and increased DPP4 levels are associated with obesity and visceral adiposity in adults.Objective: Investigating DPP-4 levels in adolescents and association with, firstly, circulating intact GLP-1 levels and glucose tolerance, secondly, BMI, and, thirdly visceral, subcutaneous and liver fat compartments.Design: Cross-sectional study, July 2012 to April 2015.Setting: Pediatric obesity clinic, Uppsala University Hospital.Patients and participants: Children and adolescents with obesity (n=59) and lean controls (n=21), age 8-18.Main outcome measures: BMI SDS, fasting plasma concentrations of DPP-4, total and intact GLP-1, fasting and OGTT concentrations of glucose and visceral (VAT) and subcutaneous (SAT) adipose tissue volumes and liver fat fraction.Results: Plasma DPP-4 decreased with age both in obese (41 ng/ml per year) and lean subjects (48 ng/ml per year). Plasma DPP-4 was higher in males both in the obesity and lean group. When adjusting for age and sex, plasma DPP-4 was negatively associated with intact GLP-1 at fasting, B=-12.3, 95% CI [-22.9, -1.8] and during OGTT, B=-12.1, 95% CI [-22.5, -1.7]. No associations were found between DPP-4 and plasma glucose measured at fasting or after a 2-hour OGTT. Plasma DPP-4 was 19% higher in the obese subjects. Among adipose tissue compartments the strongest association was with VAT, B=0.05, 95% CI [-0.02, 0.12].Conclusions: In adolescents, high plasma DPP-4 concentrations are associated with low proportion of intact GLP-1, high BMI, young age and male sex. The observed associations are compatible with an increased metabolism of GLP-1 in childhood obesity.
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| 41. |
- Stocchero, Michele, et al.
(författare)
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Influence of different drilling preparation on cortical bone : A biomechanical, histological, and micro-CT study on sheep
- 2018
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Ingår i: Clinical Oral Implants Research. - : John Wiley & Sons. - 0905-7161 .- 1600-0501. ; 29:7, s. 707-715
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveThe aim of this study was to investigate the extent of cortical bone remodeling between two different drilling protocols by means of histomorphometric, mu-CT, and biomechanical analyses. Material and methodsA total of 48 implants were inserted into the mandible of six sheep following two drilling protocols: Group A (Test, n=24), undersized preparation; Group B (Control, n=24), non-undersized preparation. The animals were euthanatized to obtain 5 and 10weeks of implantation time. Removal torque (RTQ) was measured on 12 implants of each group and the peri-implant bone was mu-CT scanned. Bone volume density (BV/TV) was calculated in pre-determined cylindrical volumes, up to 1.5mm from implant surface. Non-decalcified histology was prepared on the remaining 12 implants from each group, where total bone-to-implant contact (totBIC) and newly-formed BIC (newBIC) was measured. Bone Area Fraction Occupancy (BAFO) was determined in pre-determined areas up to 1.5mm from implant surface. Paired sample t test or Wilcoxon signed-rank test was used to investigate differences between the groups. ResultsGroup A presented significantly increased RTQ value at 5weeks, while no difference was observed at 10weeks. Group B presented increased BV/TV value at 5weeks. Both groups showed comparable values for totBIC at both time-points. However, Group A presented significantly lower newBIC at 5weeks. Higher BAFO was observed in Group B at 5weeks. ConclusionsImplants inserted into undersized sites has an increased biomechanical performance, but provoked major remodeling of the cortical bone during the early healing period compared to non-undersized preparations. After 10weeks, no difference was observed.
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| 42. |
- Takeshita, Kenji, et al.
(författare)
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Implant Vertical Fractures Provoked by Laboratory Procedures : A Finite Element Analysis Inspired from Clinical Cases
- 2016
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Ingår i: Implant Dentistry. - : Lippincott Williams & Wilkins. - 1056-6163 .- 1538-2982. ; 25:3, s. 361-366
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the causes for internal implant fractures, which is suggested to be one of the reasons for marginal bone loss. Materials and Methods: From a 14-year database of 6051 implants, 10 single implant vertical fractures were identified and the abutments were all castable abutments. The abutments presented contamination and irregularities at the internal connecting areas. The hypothesis was that perfect fit was disturbed by laboratory polishing procedures, and finite element analysis (FEA) using overcorrected and undercorrected castable abutment models were created and tested against a perfect fit model Results: The results from the FEA presented that both overcorrected and undercorrected models presented nonuniform excessive plastic strain distribution in the neck portion of the implants where clinically an implant fracture was noted Conclusions: The results suggested that laboratory procedures could induce plastic strain of the implant-abutment complex, which increases the risk of fracture
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