| 113781. |
- Leifeld, Jens, et al.
(författare)
-
Sensitivity of peatland carbon loss to organic matter quality
- 2012
-
Ingår i: Geophysical Research Letters. - 1944-8007. ; 39, s. 14704-14704
-
Tidskriftsartikel (refereegranskat)abstract
- Peatland soils store substantial amounts of organic matter (OM). During peat formation, easily decomposable OM is preferentially lost and more recalcitrant moieties accumulate. In a peat profile, OM quality thus scales with depth. Drainage and ongoing climate change poses the risk of rapid OM loss when formerly anoxic peat layers oxidize. During peat decomposition, deeper, more recalcitrant peat is exposed to the oxygen-rich surface, which may influence the decomposition rate. We show that the soil respiration rate of a disturbed temperate peatland is strongly controlled by the peat's quality and especially its polysaccharides content. The polysaccharide content of soil profiles in a wider range of peatland sites with differing degrees of disturbance was inferred by means of solid-state C-13 NMR and DRIFT spectroscopy. The data confirmed a strong decline in polysaccharide content with depth and a poor OM quality of surface peat in soils drained decades ago. We combined the evidence from respiration and spectroscopic measurements to deduce the sensitivity of peatland carbon loss with respect to OM quality by scaling measured quality to a 142-years record of peatland subsidence and carbon loss at one of the sites. According to the functional relationship between quality and respiration, the measured average annual carbon loss rate of 2.5 t C ha(-1) at that site was 20 t C ha(-1) at the onset of peatland drainage and dropped to less than 1 t C ha(-1) in recent times. Citation: Leifeld, J., M. Steffens, and A. Galego-Sala (2012), Sensitivity of peatland carbon loss to organic matter quality, Geophys. Res. Lett., 39, L14704, doi: 10.1029/2012GL051856.
|
|
| 113782. |
- Leigh, Nicholas D, et al.
(författare)
-
Rebuilding limbs, one cell at a time
- 2022
-
Ingår i: Developmental Dynamics. - : Wiley. - 1097-0177 .- 1058-8388. ; 251:9, s. 1389-1403
-
Tidskriftsartikel (refereegranskat)abstract
- The regeneration of salamander limbs has been a special fascination among scientists and keen observers for centuries. Perhaps due to how closely the salamander's limb anatomically mirrors our own, a grand aspiration of regenerative medicine has been to provoke such a process following injury or loss of human limbs. Research in the last century has focused on understanding the blastema, a proliferative cell mass that develops after limb amputation (see Box 1 “A primer on limb regeneration” and reviews for discussion of foundational knowledge1-3). The first micrographs of limb blastemas (examples in Thornton4 and Hay5) brought limb regeneration to a cellular level and ushered in a new era of questions centered around the origin, potency, and processes of regenerative cells that has occupied the field ever since. Within this commentary, we will outline some of these persistent questions underlying limb regeneration, and how new technologies and approaches are paving the way toward a cellular understanding of complex tissue regeneration.
|
|
| 113783. |
|
|
| 113784. |
- Leigh, Richard, et al.
(författare)
-
Imaging the physiological evolution of the ischemic penumbra in acute ischemic stroke
- 2018
-
Ingår i: Journal of Cerebral Blood Flow and Metabolism. - 1559-7016. ; 38:9, s. 1500-1516
-
Forskningsöversikt (refereegranskat)abstract
- We review the hemodynamic, metabolic and cellular parameters affected during early ischemia and their changes as a function of approximate cerebral blood flow ( CBF) thresholds. These parameters underlie the current practical definition of an ischemic penumbra, namely metabolically affected but still viable brain tissue. Such tissue is at risk of infarction under continuing conditions of reduced CBF, but can be rescued through timely intervention. This definition will be useful in clinical diagnosis only if imaging techniques exist that can rapidly, and with sufficient accuracy, visualize the existence of a mismatch between such a metabolically affected area and regions that have suffered cell depolarization. Unfortunately, clinical data show that defining the outer boundary of the penumbra based solely on perfusion-related thresholds may not be sufficiently accurate. Also, thresholds for CBF and cerebral blood volume ( CBV) differ for white and gray matter and evolve with time for both inner and outer penumbral boundaries. As such, practical penumbral imaging would involve parameters in which the physiology is immediately displayed in a manner independent of baseline CBF or CBF threshold, namely pH, oxygen extraction fraction ( OEF), diffusion constant and mean transit time ( MTT). Suitable imaging technologies will need to meet this requirement in a 10-20 min exam.
|
|
| 113785. |
- Leighton, Jonathan A., et al.
(författare)
-
Capsule Endoscopy Is Superior to Small-bowel Follow-through and Equivalent to Ileocolonoscopy in Suspected Crohn's Disease
- 2014
-
Ingår i: Clinical Gastroenterology and Hepatology. - : Elsevier BV. - 1542-7714 .- 1542-3565. ; 12:4, s. 609-615
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND & AIMS: Evaluation of the small intestine for inflammation has traditionally relied on small-bowel follow-through (SBFT), but multiple studies have demonstrated its low diagnostic accuracy. Capsule endoscopy (CE) transmits high-quality images of the small intestinal mucosa; it can be used to visualize the entire length of the small bowel and much of the mucosa. We compared the diagnostic yields of CE vs SBFT in a prospective study of patients with suspected small-bowel Crohn's disease. METHODS: Eighty patients with signs and/or symptoms of small-bowel Crohn's disease (age, 10-65 years) underwent CE, followed by SBFT and ileocolonoscopy. Readers were blinded to other test results. The primary outcome was the diagnostic yield for inflammatory lesions found with CE before ileocolonoscopy compared with SBFT and ileocolonoscopy. A secondary outcome was the incremental diagnostic yield of CE compared with ileocolonoscopy and CE compared with SBFT. RESULTS: The combination of CE and ileocolonoscopy detected 107 of 110 inflammatory lesions (97.3%), whereas the combination of SBFT and ileocolonoscopy detected only 63 lesions (57.3%) (P < .001). The diagnostic yield of CE compared with ileocolonoscopy was not different (P = .09). The diagnostic yield was higher for CE than for SBFT (P < .001). Of the 80 patients with suspected Crohn's disease, 25 (31.3%) had the diagnosis confirmed. Eleven were diagnosed by CE findings alone and 5 by ileocolonoscopy findings alone. In the remaining 9 patients, diagnostic findings were identified by at least 2 of the 3 modalities. No diagnoses were made on the basis of SBFT findings alone. CONCLUSIONS: CE was better than SBFT and equivalent to ileocolonoscopy in detecting small-bowel inflammation. Although ileocolonoscopy remains the initial diagnostic test of choice, CE is safe and can establish the diagnosis of Crohn's disease in patients when ileocolonoscopy results are negative or the terminal ileum cannot be evaluated. ClinicalTrials.gov Number: NCT00487396.
|
|
| 113786. |
- Leijenaar, Jolien F., et al.
(författare)
-
Comorbid amyloid-β pathology affects clinical and imaging features in VCD
- 2020
-
Ingår i: Alzheimer's and Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 16:2, s. 354-364
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: To date, the clinical relevance of comorbid amyloid-β (Aβ) pathology in patients with vascular cognitive disorders (VCD) is largely unknown. Methods: We included 218 VCD patients with available cerebrospinal fluid Aβ42 levels. Patients were divided into Aβ+ mild-VCD (n = 84), Aβ− mild-VCD (n = 68), Aβ+ major-VCD (n = 31), and Aβ− major-VCD (n = 35). We measured depression with the Geriatric Depression Scale, cognition with a neuropsychological test battery and derived white matter hyperintensities (WMH) and gray matter atrophy from MRI. Results: Aβ− patients showed more depressive symptoms than Aβ+. In the major-VCD group, Aβ− patients performed worse on attention (P =.02) and executive functioning (P =.008) than Aβ+. We found no cognitive differences in patients with mild VCD. In the mild-VCD group, Aβ− patients had more WMH than Aβ+ patients, whereas conversely, in the major-VCD group, Aβ+ patients had more WMH. Atrophy patterns did not differ between Aβ+ and Aβ− VCD group. Discussion: Comorbid Aβ pathology affects the manifestation of VCD, but effects differ by severity of VCD.
|
|
| 113787. |
|
|
| 113788. |
- Leijon, Marie
(författare)
-
Att spåra tecken på lärande : Mediereception som pedagogisk form och multimodalt meningsskapande över tid
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present study is about media reception as an educational form, supporting meaning-making over time. The thesis stems from the desire to understand the complexity in a meaning-making process that takes its point of departure in media productions. The aim is to investigate the possibilities and limitations for meaning-making over time, afforded by the meeting of a group of student teachers and their texts, in a teacher education context. The following questions are posed: How is the meeting between participants and the text designed in the form of a reception? How do participants act on the resources that are offered during the receptions? Which sign systems and semiotic resources are used, and how are they used? How does meaning-making evolve over time? The theoretical point of departure is a design theory perspective, called designs for learning, proposing a performative aspect of learning. Design theory contributes by placing focus on framed sign-creating meaning-making activities, and by stressing participants’ creation and production. The design theory perspective is here enriched by a socio-cultural perspective, Bakhtin’s focus on dialogue, and Goffman’s research on interaction. With the ambition of studying meaning-making over time, a group of student teachers were followed over the two occasions for reception. Video observation was chosen as a method to study participants’ interaction at the receptions. The receptions were filmed and subsequently analysed multimodally. The video recordings resulted in a video text, which was transformed through the written text of the transcription, a text which was subsequently reshaped into a new text that is here presented in the thesis. By studying meaning-making over time, various forms of learning may be traced. Results suggest that the reception as an educational form has an impact on the meaning that is shaped in this setting. Seeing yourself and your results with the eyes of others and having the opportunity to meet the perspectives of different voices, are all elements that contribute to meaning-making. Creating a work that meets an audience, being able to find support in a design for the meeting, and during the meeting to form a new text, jointly prove to be powerful aspects of meaning-making. The thesis sheds light on an insufficiently explored area: media production and media reception in the context of teacher education. Working with media forms such as sound and moving images means that participants can avail themselves of a variety of types of texts, with different affordances, and use them as resources in their meaning-making. The study further indicates that participants exploit the various media forms and polyphony to develop knowledge about their subject matter. In other words, working with media in learning processes is something that enriches meaning-making. The study points to the need for increased openness in the perception of signs of learning, and more attentive listening to such signs. The importance of receptions for meaning-making has been clarified, where receptions have been understood as a learning process in their own right. The role that different media forms play in enriching meaning-making has been brought to the fore. Finally, a reformulated use is proposed of the theoretical model of a formal learning process.
|
|
| 113789. |
- Leijon, Matti E., 1970-, et al.
(författare)
-
Factors associated with patients self-reported adherence to prescribed physical activity in routine primary health care
- 2010
-
Ingår i: BMC Family Practice. - London, UK : BioMed Central. - 1471-2296. ; 11:38
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Written prescriptions of physical activity, so‐called physical activity referral (PAR) schemes, have increased in popularity in recent years. Such schemes have mostly been evaluated in terms of efficacy. This study reports on a Swedish PAR scheme implemented in routine primary health care (PHC) measuring patients’ self‐reported adherence to physical activity prescriptions. The aim of this study was to evaluate adherence to physical activity prescriptions issued in everyday PHC at 3 and 12 months and to analyse the different characteristics associated with adherence to these prescriptions.Methods: Prospective prescription data were obtained for 37 of the 42 PHC centres in Östergötland County, Sweden, during 2004. The study population consisted of 3300 patients issued PARs by ordinary PHC staff members. Odds ratios were calculated to identify the factors associated with adherence.Results: The average adherence rate was 56% at 3 months and 50% at 12 months. In the descriptive analyses, higher adherence was associated with increased age, higher activity level at baseline, home‐based activities, prescriptions issued by professional groups other than physicians, and among patients issued PARs due to diabetes, high blood pressure and “other PAR reasons”. In the multiple logistic regression models, higher adherence was associated with higher activity level at baseline, and to prescriptions including home‐based activities, both at 3 and 12 months.Conclusions: Prescriptions from ordinary staff in routine PHC yielded adherence in 50% of the patients in this routine care PAR scheme follow‐up. Patients’ activity level at baseline (being at least somewhat physically inactive) and being issued homebased activities were associated with higher adherence at both 3 and 12 months.
|
|
| 113790. |
- Leijon, Matti E., et al.
(författare)
-
Who is not adhering to physical activity referrals, and why?
- 2011
-
Ingår i: Scandinavian Journal of Primary Health Care. - : Informa Healthcare. - 0281-3432 .- 1502-7724. ; 29:4, s. 234-240
-
Tidskriftsartikel (refereegranskat)abstract
- Objective. To analyse patients self-reported reasons for not adhering to physical activity referrals (PARs). Design and setting. Data on 1358 patients who did not adhere to PARs were collected at 38 primary health care (PHC) centres in Sweden. Intervention. PHC providers issued formal physical activity prescriptions for home-based activities or referrals for facility-based activities. Subjects. Ordinary PHC patients whom regular staff believed would benefit from increased physical activity. Main outcome measure: Reasons for non-adherence to PARs: "sickness", "pain", "low motivation", "no time", "economic factors", and "other". Results. Sickness and pain were the most common motives for non-adherence among older patients. The youngest patients blamed economic factors and lack of time more frequently than those in the oldest age group. Economic factors was a more common reason for non-adherence among those referred for facility-based activities compared with those prescribed home-based activities. Low motivation was a more frequent cause of non-adherence among those prescribed home-based activities compared with those referred for facility-based activities. Furthermore, lack of time was a more common reason for non-adherence among patients issued with PARs due to high blood pressure than other patients, while low motivation was a more common reason among patients issued with PARs because of a BMI of greater than 25. Conclusion. The reasons for non-adherence differ between patients prescribed home-based activities and referred for facility-based activities, as well as between patients with different specific characteristics. The information obtained may be valuable not only for the professionals working in PHC, but also for those who work to develop PARs for use in different contexts.
|
|
