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- Alexanderson, Helena, et al.
(författare)
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An Arctic perspective on dating Mid-Late Pleistocene environmental history
- 2014
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 92, s. 9-31
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Forskningsöversikt (refereegranskat)abstract
- To better understand Pleistocene climatic changes in the Arctic, integrated palaeoenvironmental andpalaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologicage control are required, not least for correlation to extra-Arctic records. In this paper we discuss,from an Arctic perspective, methods and correlation tools that are commonly used to date ArcticPleistocene marine and terrestrial events. We review the state of the art of Arctic geochronology, withfocus on factors that affect the possibility and quality of dating, and support this overview by examples ofapplication of modern dating methods to Arctic terrestrial and marine sequences.Event stratigraphy and numerical ages are important tools used in the Arctic to correlate fragmentedterrestrial records and to establish regional stratigraphic schemes. Age control is commonly provided byradiocarbon, luminescence or cosmogenic exposure ages. Arctic Ocean deep-sea sediment successionscan be correlated over large distances based on geochemical and physical property proxies for sedimentcomposition, patterns in palaeomagnetic records and, increasingly, biostratigraphic data. Many of theseproxies reveal cyclical patterns that provide a basis for astronomical tuning.Recent advances in dating technology, calibration and age modelling allow for measuring smallerquantities of material and to more precisely date previously undatable material (i.e. foraminifera for 14C,and single-grain luminescence). However, for much of the Pleistocene there are still limits to the resolutionof most dating methods. Consequently improving the accuracy and precision (analytical andgeological uncertainty) of dating methods through technological advances and better understanding ofprocesses are important tasks for the future. Another challenge is to better integrate marine andterrestrial records, which could be aided by targeting continental shelf and lake records, exploringproxies that occur in both settings, and by creating joint research networks that promote collaborationbetween marine and terrestrial geologists and modellers.
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| 2. |
- Jakobsson, Martin, et al.
(författare)
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Arctic Ocean glacial history
- 2014
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 92, s. 40-67
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Forskningsöversikt (refereegranskat)abstract
- While there are numerous hypotheses concerning glacial interglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the present state-of-the-art knowledge gained from field work and chronological studies, and with a specific focus on ice-sheet extent and environmental conditions during the Last Glacial Maximum (LGM). The maximum Quaternary extension of ice sheets is discussed and compared to LGM. We bring together recent results from the circum-Arctic continental margins and the deep central basin; extent of ice sheets and ice streams bordering the Arctic Ocean as well as evidence for ice shelves extending into the central deep basin. Discrepancies between new results and published LGM ice-sheet reconstructions in the high Arctic are highlighted and outstanding questions are identified. Finally, we address the ability to simulate the Arctic Ocean ice sheet complexes and their dynamics, including ice streams and ice shelves, using presently available ice-sheet models. Our review shows that while we are able to firmly reject some of the earlier hypotheses formulated to describe Arctic Ocean glacial conditions, we still lack information from key areas to compile the holistic Arctic Ocean glacial history.
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| 3. |
- Löfstrand Tideström, Britta, 1940-, et al.
(författare)
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Breathing obstruction in relation to craniofacial and dental arch morphology in 4-year-old children
- 1999
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Ingår i: European Journal of Orthodontics. - 0141-5387 .- 1460-2210. ; 21:4, s. 323-332
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of breathing obstruction was determined in a cohort of 4-year-old children. Craniofacial morphology was studied in obstructed children and compared with data from a control group of 4-year-old children with ideal occlusion. Dental arch morphology was compared in obstructed and non-obstructed children in the group. Parents of 95.5 per cent of the study base of 644 children answered a questionnaire concerning their child's nocturnal behaviour and related questions. The 48 children who, based on parental report, snored every night or stopped breathing when snoring (the 'snoring group'), showed a higher rate of disturbed sleep, mouth-breathing, and a history of throat infections as compared with the rest of the cohort. These children were examined by both an orthodontist and an otorhinolaryngologist and, when indicated, they were also monitored in a sleep laboratory. Twenty-eight of the children were diagnosed as having a breathing obstruction (4.3 per cent of the cohort) and six children (0.9 per cent) had sleep apnoea (mean apnoea-hypopnoea index of 17.3), using the same definition as that for adults. Cephalometric values among the obstructed children differed from those of a Swedish sample of the same age with ideal occlusion. Thy had a smaller cranial base angle and a lower ratio of posterior/anterior total face height. Small, but not significant differences were seen for NSL-ML and NL-ML. Compared with 48 asymptomatic children from the same cohort, the obstructed children had a narrower maxilla, a deeper palatal height, and a shorter lower dental arch. In addition, the prevalence of lateral crossbite was significantly higher among the obstructed children.
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| 4. |
- Mani, Maria, et al.
(författare)
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Objective Assessment of Nasal Airway in Unilateral Cleft Lip and Palate : a Long-term Study
- 2010
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Ingår i: The Cleft Palate-Craniofacial Journal. - : SAGE Publications. - 1055-6656 .- 1545-1569. ; 47:3, s. 217-224
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To objectively evaluate the nasal function in adults operated on for unilateral cleft lip and palate with one-stage or two-stage palate closure. DESIGN: The population consists of all unilateral cleft lip and palate patients born from 1960 to 1987 and treated at the Cleft Lip and Palate Center, Uppsala University Hospital, Sweden. The patients were treated according to the same protocol except for palate closure, which was performed in one stage until 1977 and in two stages thereafter. Eighty-three patients participated. Mean follow-up time after primary surgery was 32 years. An age-matched control group underwent the same examinations. MAIN OUTCOME MEASURES: Nasal minimum cross-sectional area (cm(2)) and volume (cm(3)) were assessed (acoustic rhinometry). Airflow resistance (Pa s/cm(3)) (rhinomanometry), peak inspiratory flow (L/min) (peak nasal inspiratory flow), and number of identified odors (Scandinavian Odor Identification Test) were determined. RESULTS: The cleft side of unilateral cleft lip and palate patients had significantly lower values for all parameters compared with controls (p < .001). No difference was found between one-stage and two-stage procedures in values for the cleft side. However, the nasal area and volume of the noncleft side were significantly larger in patients who underwent one-stage as compared with two-stage procedures (p < .05). CONCLUSION: The nasal airway of unilateral cleft lip and palate patients demonstrates a wide range of impairments that can be quantified by objective measurements. However, the measurements used did not differentiate between patients operated on with the one-stage and two-stage procedures except for values of the noncleft side.
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