| 1. |
- Callaghan, Terry, et al.
(författare)
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Multi-Decadal Changes in Tundra Environments and Ecosystems : Synthesis of the International Polar Year-Back to the Future Project (IPY-BTF)
- 2011
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:6, s. 705-716
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the responses of tundra systemsto global change has global implications. Most tundraregions lack sustained environmental monitoring and oneof the only ways to document multi-decadal change is toresample historic research sites. The International PolarYear (IPY) provided a unique opportunity for such researchthrough the Back to the Future (BTF) project (IPY project#512). This article synthesizes the results from 13 paperswithin this Ambio Special Issue. Abiotic changes includeglacial recession in the Altai Mountains, Russia; increasedsnow depth and hardness, permafrost warming, andincreased growing season length in sub-arctic Sweden;drying of ponds in Greenland; increased nutrient availabilityin Alaskan tundra ponds, and warming at mostlocations studied. Biotic changes ranged from relativelyminor plant community change at two sites in Greenland tomoderate change in the Yukon, and to dramatic increasesin shrub and tree density on Herschel Island, and in subarcticSweden. The population of geese tripled at one sitein northeast Greenland where biomass in non-grazed plotsdoubled. A model parameterized using results from a BTFstudy forecasts substantial declines in all snowbeds andincreases in shrub tundra on Niwot Ridge, Colorado overthe next century. In general, results support and provideimproved capacities for validating experimental manipulation,remote sensing, and modeling studies.
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| 2. |
- Ballo, Ahmed, 1978, et al.
(författare)
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Bone tissue reactions to biomimetic ion-substituted apatite surfaces on titanium implants
- 2012
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 9:72, s. 1615-1624
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the bone tissue response to strontium-and silicon-substituted apatite (Sr-HA and Si-HA) modified titanium (Ti) implants. Sr-HA, Si-HA and HA were grown on thermally oxidized Ti implants by a biomimetic process. Oxidized implants were used as controls. Surface properties, i.e. chemical composition, surface thickness, morphology/pore characteristics, crystal structure and roughness, were characterized with various analytical techniques. The implants were inserted in rat tibiae and block biopsies were prepared for histology, histomorphometry and scanning electron microscopy analysis. Histologically, new bone formed on all implant surfaces. The bone was deposited directly onto the Sr-HA and Si-HA implants without any intervening soft tissue. The statistical analysis showed significant higher amount of bone-implant contact (BIC) for the Si-doped HA modification (P = 0.030), whereas significant higher bone area (BA) for the Sr-doped HA modification (P = 0.034), when compared with the non-doped HA modification. The differences were most pronounced at the early time point. The healing time had a significant impact for both BA and BIC (P < 0.001). The present results show that biomimetically prepared Si-HA and Sr-HA on Ti implants provided bioactivity and promoted early bone formation.
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| 3. |
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| 4. |
- Cannon, Christopher P., et al.
(författare)
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Comparison of ticagrelor with clopidogrel in patients with a planned invasive strategy for acute coronary syndromes (PLATO) : a randomised double-blind study
- 2010
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 375:9711, s. 283-293
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Variation in and irreversibility of platelet inhibition with clopidogrel has led to controversy about its optimum dose and timing of administration in patients with acute coronary syndromes. We compared ticagrelor, a more potent reversible P2Y12 inhibitor with clopidogrel in such patients. METHODS: At randomisation, an invasive strategy was planned for 13 408 (72.0%) of 18 624 patients hospitalised for acute coronary syndromes (with or without ST elevation). In a double-blind, double-dummy study, patients were randomly assigned in a one-to-one ratio to ticagrelor and placebo (180 mg loading dose followed by 90 mg twice a day), or to clopidogrel and placebo (300-600 mg loading dose or continuation with maintenance dose followed by 75 mg per day) for 6-12 months. All patients were given aspirin. The primary composite endpoint was cardiovascular death, myocardial infarction, or stroke. Analyses were by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00391872. FINDINGS: 6732 patients were assigned to ticagrelor and 6676 to clopidogrel. The primary composite endpoint occurred in fewer patients in the ticagrelor group than in the clopidogrel group (569 [event rate at 360 days 9.0%] vs 668 [10.7%], hazard ratio 0.84, 95% CI 0.75-0.94; p=0.0025). There was no difference between clopidogrel and ticagrelor groups in the rates of total major bleeding (691 [11.6%] vs 689 [11.5%], 0.99 [0.89-1.10]; p=0.8803) or severe bleeding, as defined according to the Global Use of Strategies To Open occluded coronary arteries, (198 [3.2%] vs 185 [2.9%], 0.91 [0.74-1.12]; p=0.3785). INTERPRETATION: Ticagrelor seems to be a better option than clopidogrel for patients with acute coronary syndromes for whom an early invasive strategy is planned.
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| 5. |
- Emanuelsson, Eva U., et al.
(författare)
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Parameterization of Thermal Properties of Aging Secondary Organic Aerosol Produced by Photo-Oxidation of Selected Terpene Mixtures
- 2014
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:11, s. 6168-6176
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Tidskriftsartikel (refereegranskat)abstract
- Formation and evolution of secondary organic aerosols (SOA) from biogenic VOCs influences the Earth's radiative balance. We have examined the photo-oxidation and aging of boreal terpene mixtures in the SAPHIR simulation chamber. Changes in thermal properties and chemical composition, deduced from mass spectrometric measurements, were providing information on the aging of biogenic SOA produced under ambient solar conditions. Effects of precursor mixture, concentration, and photochemical oxidation levels (OH exposure) were evaluated. OH exposure was found to be the major driver in the long term photochemical transformations, i.e., reaction times of several hours up to days, of SOA and its thermal properties, whereas the initial concentrations and terpenoid mixtures had only minor influence. The volatility distributions were parametrized using a sigmoidal function to determine T-VFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. T-VFR0.5 increased by 0.3 +/- 0.1% (ca. 1 K), while the steepness increased by 0.9 +/- 0.3% per hour of 1 x 10(6) cm(-3) OH exposure. Thus, aging reduces volatility and increases homogeneity of the vapor pressure distribution, presumably because highly volatile fractions become increasingly susceptible to gas phase oxidation, while less volatile fractions are less reactive with gas phase OH.
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| 6. |
- Grandfield, Kathryn, et al.
(författare)
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Bone response to free form fabricated hydroxyapatite and zirconia scaffolds : a transmission electron microscopy study in the human maxilla
- 2012
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1523-0899 .- 1708-8208. ; 14:3, s. 461-469
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Tidskriftsartikel (refereegranskat)abstract
- Background: Understanding the interfacial reactions to synthetic bone regenerative scaffolds in vivo is fundamental for improving osseointegration and osteogenesis. Using transmission electron microscopy, it is possible to study the biological response of hydroxyapatite (HA) and zirconia (ZrO2) scaffolds at the nanometer scale.Purpose: In this study, the bone-bonding abilities of HA and ZrO2 scaffolds produced by free-form fabrication were evaluated in the human maxilla at 3 months and 7 months.Materials and Methods: HA and ZrO2 scaffolds (ø: 3 mm) were implanted in the human maxilla, removed with surrounding bone, embedded in resin, and sectioned. A novel focused ion beam (FIB) sample preparation technique enabled the production of thin lamellae for study by scanning transmission electron microscopy.Results: Interface regions were investigated using high-angle annular dark-field imaging and energy-dispersive X-ray spectroscopy analysis. Interfacial apatite layers of 80 nm and 50 nm thickness were noted in the 3- and 7-month HA samples, respectively, and bone growth was discovered in micropores up to 10 µm into the samples.Conclusions: The absence of an interfacial layer in the ZrO2 samples suggest the formation of a direct contact with bone, while HA, which bonds through an apatite layer, shows indications of resorption with increasing implantation time. This study demonstrates the potential of HA and ZrO2 scaffolds for use as bone regenerative materials.
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| 7. |
- Grandfield, Kathryn, et al.
(författare)
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Free form fabricated features on CoCr implants with and without hydroxyapatite coating in vivo : a comparative study of bone contact and bone growth induction
- 2011
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 22:4, s. 899-906
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Tidskriftsartikel (refereegranskat)abstract
- The current study evaluates the in vivo response to free form fabricated cobalt chromium (CoCr) implants with and without hydroxyapatite (HA) plasma sprayed coatings. The free form fabrication method allowed for integration of complicated pyramidal surface structures on the cylindrical implant. Implants were press fit into the tibial metaphysis of nine New Zealand white rabbits. Animals were sacrificed and implants were removed and embedded. Histological analysis, histomorphometry and electron microscopy studies were performed. Focused ion beam was used to prepare thin sections for high-resolution transmission electron microscopy examination. The fabricated features allowed for effective bone in-growth and firm fixation after 6 weeks. Transmission electron microscopy investigations revealed intimate bone-implant integration at the nanometre scale for the HA coated samples. In addition, histomorphometry revealed a significantly higher bone contact on HA coated implants compared to native CoCr implants. It is concluded that free form fabrication in combination with HA coating improves the early fixation in bone under experimental conditions.
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| 8. |
- Palmquist, Anders, 1977, et al.
(författare)
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Biomechanical, Histological and Ultrastructural Analyses of Laser Micro- and Nano-structured Titanium Alloy Implants : A Study in Rabbit
- 2010
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Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 92A:4, s. 1476-1486
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the biomechanical properties and ultrastructure of the bone response of partly laser-modified Ti6Al4V implants compared with turned, machined implants after 8 weeks in rabbit. The surface analyses performed with interference microscopy and electron microscopy showed increased surface topography with micro- and nano-sized surface features as well as increased oxide thickness of the modified surface. The biomechanical testing demonstrated a 270% increase in torque value for the surface modified implants compared with the control implants. Histological evaluation of ground sections of specimens subjected to biomechanical testing revealed ongoing bone formation and remodeling. A histological feature exclusively observed at the laser-modified surface was the presence of fracture in the mineralized bone rather than at the interface between the bone and implant. Transmission electron microscopy (TEM) was performed on Focused Ion Beam (FIB) prepared samples of the intact bone-implant interface, demonstrating a direct contact between nanocrystalline hydroxyapatite and the oxide of the laser-modified implant surface. In conclusion, laser-modified titanium alloy implants have significantly stronger bone anchorage compared with machined implants and show no adverse tissue reactions.
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| 9. |
- Rundqvist, Sara, et al.
(författare)
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Tree and shrub expansion over the past 34 years at the tree-line near Abisko, Sweden
- 2011
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:6, s. 683-692
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Tidskriftsartikel (refereegranskat)abstract
- Shrubs and trees are expected to expand in the sub-Arctic due to global warming. Our study was conducted in Abisko, sub-arctic Sweden. We recorded the change in coverage of shrub and tree species over a 32- to 34-year period, in three 50 x 50 m plots; in the alpine-tree-line ecotone. The cover of shrubs and trees (<3.5 cm diameter at breast height) were estimated during 2009-2010 and compared with historical documentation from 1976 to 1977. Similarly, all tree stems (>= 3.5 cm) were noted and positions determined. There has been a substantial increase of cover of shrubs and trees, particularly dwarf birch (Betula nana), and mountain birch (Betula pubescens ssp. czerepanovii), and an establishment of aspen (Populus tremula). The other species willows (Salix spp.), juniper (Juniperus communis), and rowan (Sorbus aucuparia) revealed inconsistent changes among the plots. Although this study was unable to identify the causes for the change in shrubs and small trees, they are consistent with anticipated changes due to climate change and reduced herbivory.
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| 10. |
- Scirica, Benjamin M., et al.
(författare)
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The Incidence of Bradyarrhythmias and Clinical Bradyarrhythmic Events in Patients With Acute Coronary Syndromes Treated With Ticagrelor or Clopidogrel in the PLATO (Platelet Inhibition and Patient Outcomes) Trial Results of the Continuous Electrocardiographic Assessment Substudy
- 2011
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Ingår i: Journal of the American College of Cardiology. - : Elsevier BV. - 0735-1097 .- 1558-3597. ; 57:19, s. 1908-1916
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Tidskriftsartikel (refereegranskat)abstract
- Objectives The aim of this study was to determine whether ticagrelor increased the risk of ventricular pauses compared with clopidogrel and whether these pauses were associated with any clinical bradycardic events in patients presenting with acute coronary syndromes. Background Ticagrelor, an oral reversibly binding P2Y(12) inhibitor, provides more potent and consistent inhibition of platelet aggregation than clopidogrel but in a phase II study was associated with increased risk for ventricular pauses. A prospective continuous electrocardiographic (cECG) assessment was therefore performed within the PLATO (Platelet Inhibition and Patient Outcomes) study comparing ticagrelor and clopidogrel in patients hospitalized with acute coronary syndromes. Methods Patients in the cECG assessment had planned 7-day cECG recording initiated at the time of randomization (week 1), which was within 24 h of symptom onset, and then repeated at 1 month after randomization during the convalescent phase. The principal safety endpoint was the incidence of ventricular pauses lasting at least 3 s. Investigators also reported symptomatic bradycardic adverse events during the entire study duration (median 277 days). Results A total of 2,908 patients were included in the cECG assessment, of whom 2,866 (98.5%) had week 1 recordings, 1,991 (68.4%) had 1-month recordings, and 1,949 (67.0%) had both. During the first week after randomization, ventricular pauses >= 3 s occurred more frequently in patients receiving ticagrelor than clopidogrel (84 [5.8%] vs. 51 [3.6%]; relative risk: 1.61; p = 0.006). At 1 month, pauses >= 3 s occurred overall less frequently and were similar between treatments (2.1% vs. 1.7%). Most were ventricular pauses, and the greatest excess associated with ticagrelor were asymptomatic, sinoatrial nodal in origin (66%), and nocturnal. There were no differences between ticagrelor and clopidogrel in the incidence of clinically reported bradycardic adverse events, including syncope, pacemaker placement, and cardiac arrest. Conclusions In the PLATO cECG assessment, more patients treated with ticagrelor compared with clopidogrel had ventricular pauses, which were predominantly asymptomatic, sinoatrial nodal in origin, and nocturnal and occurred most frequently in the acute phase of acute coronary syndromes. There were no apparent clinical consequences related to the excess in ventricular pauses in patients assigned to ticagrelor. (A Comparison of AZD6140 and Clopidogrel in Patients With Acute Coronary Syndrome [PLATO]; NCT00391872) (J Am Coll Cardiol 2011; 57: 1908-16) .
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