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Search Results: 1 - 10 of 203654 matches for " Mats P. Bj rkman "
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Reactive nitrogen and sulphate wet deposition at Zeppelin Station, Ny- lesund, Svalbard
Rafael Kühnel,Mats P. Bjrkman,Carmen P. Vega,Andy Hodson
Polar Research , 2013, DOI: 10.3402/polar.v32i0.19136
Abstract: As a potent fertilizer, reactive nitrogen plays an important role in Arctic ecosystems. Since the Arctic is a nutrient-limited environment, changes in nitrogen deposition can have severe impacts on local ecosystems. To quantify the amount of nitrogen deposited through snow and rain events, precipitation sampling was performed at Zeppelin Station, Svalbard, from November 2009 until May 2011. The samples were analysed for , nss- and concentrations, and the deposition of single precipitation events was calculated using precipitation measurements taken at nearby Ny- lesund. The majority of observed events showed concentrations ranging from 0.01 to 0.1 mg L 1 N for and and from 0.02 to 0.3 mg L 1 S for nss-. The majority of calculated depositions ranged from 0.01 to 0.1 mg m 2 N for and and from 0.02 to 0.3 mg m 2 S for nss-. The budget was controlled by strong deposition events, caused by long-lasting precipitation episodes that lasted for several days and which had raised concentrations of nitrogen and sulphur. Three future scenarios of increasing precipitation in the Arctic were considered. The results showed that deposition is mainly controlled by the amount of precipitation, which leads to the conclusion that increased precipitation might cause increases in deposition of the same magnitude.
Nitrate dry deposition in Svalbard
Mats P. Bjrkman,Rafael Kühnel,Daniel G. Partridge,Tjarda J. Roberts
Tellus B , 2013, DOI: 10.3402/tellusb.v65i0.19071
Abstract: Arctic regions are generally nutrient limited, receiving an extensive part of their bio-available nitrogen from the deposition of atmospheric reactive nitrogen. Reactive nitrogen oxides, as nitric acid (HNO3) and nitrate aerosols (p-NO3), can either be washed out from the atmosphere by precipitation or dry deposited, dissolving to nitrate (NO3-). During winter, NO3- is accumulated in the snowpack and released as a pulse during spring melt. Quantification of NO3- deposition is essential to assess impacts on Arctic terrestrial ecology and for ice core interpretations. However, the individual importance of wet and dry deposition is poorly quantified in the high Arctic regions where in-situ measurements are demanding. In this study, three different methods are employed to quantify NO3- dry deposition around the atmospheric and ecosystem monitoring site, Ny- lesund, Svalbard, for the winter season (September 2009 to May 2010): (1) A snow tray sampling approach indicates a dry deposition of –10.27±3.84 mg m 2 (± S.E.); (2) A glacial sampling approach yielded somewhat higher values –30.68±12.00 mg m 2; and (3) Dry deposition was also modelled for HNO3 and p-NO3 using atmospheric concentrations and stability observations, resulting in a total combined nitrate dry deposition of –10.76±1.26 mg m 2. The model indicates that deposition primarily occurs via HNO3 with only a minor contribution by p-NO3. Modelled median deposition velocities largely explain this difference: 0.63 cm s 1 for HNO3 while p-NO3 was 0.0025 and 0.16 cm s 1 for particle sizes 0.7 and 7 μm, respectively. Overall, the three methods are within two standard errors agreement, attributing an average 14% (total range of 2–44%) of the total nitrate deposition to dry deposition. Dry deposition events were identified in association with elevated atmospheric concentrations, corroborating recent studies that identified episodes of rapid pollution transport and deposition to the Arctic.
20-Year Climatology of and Wet Deposition at Ny-lcurlyb\AArcurlyblesund, Svalbard
Rafael Kühnel,Tjarda J. Roberts,Mats P. Bj rkman,Elisabeth Isaksson,Wenche Aas,Kim Holmén,Johan Str m
Advances in Meteorology , 2011, DOI: 10.1155/2011/406508
Abstract: A 20-year dataset of weekly precipitation observations in Ny-Ålesund, Svalbard, was analysed to assess atmospheric wet deposition of nitrogen. Mean annual total nitrogen deposition was 74 mg N/(m2 yr) but exhibited large interannual variability and was dominated by highly episodic “strong” events, probably caused by rapid transport from European sources. The majority (90%) of precipitation samples were defined as “weak” (<2 mg N/m2) and contributed an annual baseline of ~17 mg N/(m2 yr), whereas 10% of precipitation samples were defined as “strong” (>2 mg N/m2) and additionally contributed up to 225 mg N/(m2 yr). Nitrate deposition largely occurred in samples within the solid-precipitation season (16 September–2 June), and ammonium deposition occurred equally in both solid and liquid seasons. Trends of reactive nitrogen emissions from Europe are uncertain, and increasing cyclonic activity over the North Atlantic caused by a changing climate might lead to more strong deposition events in Svalbard.
20-Year Climatology of and Wet Deposition at Ny-lcurlyb\AArcurlyblesund, Svalbard
Rafael Kühnel,Tjarda J. Roberts,Mats P. Bjrkman,Elisabeth Isaksson,Wenche Aas,Kim Holmén,Johan Str?m
Advances in Meteorology , 2011, DOI: 10.1155/2011/406508
Abstract: A 20-year dataset of weekly precipitation observations in Ny-?lesund, Svalbard, was analysed to assess atmospheric wet deposition of nitrogen. Mean annual total nitrogen deposition was 74?mg?N/(m2?yr) but exhibited large interannual variability and was dominated by highly episodic “strong” events, probably caused by rapid transport from European sources. The majority (90%) of precipitation samples were defined as “weak” (<2?mg?N/m2) and contributed an annual baseline of ~17?mg?N/(m2?yr), whereas 10% of precipitation samples were defined as “strong” (>2?mg?N/m2) and additionally contributed up to 225?mg?N/(m2?yr). Nitrate deposition largely occurred in samples within the solid-precipitation season (16 September–2 June), and ammonium deposition occurred equally in both solid and liquid seasons. Trends of reactive nitrogen emissions from Europe are uncertain, and increasing cyclonic activity over the North Atlantic caused by a changing climate might lead to more strong deposition events in Svalbard. 1. Introduction Human activities release reactive nitrogen such as NH3 and (NO + NO2) to the atmosphere through energy production, fertilizer production, and cultivation of crops [1–4]. The resulting nitrogen-enriched air masses can be transported into remote, nutrient-limited regions such as the Arctic [5], primarily in the form of PAN (peroxyacetyl nitrate), but also as nitrate and ammonium aerosol. Furthermore, deposition of reactive nitrogen through precipitation is considered to be the main pathway for transfer of atmospheric nitrogen to the high Arctic surface [6]. The deposition of reactive nitrogen in the Arctic therefore results from the complex interplay of emissions, atmospheric transport, chemistry, precipitation, and snowpack processes as described below. Ice core analyses from Svalbard [7] and Greenland [8] showed an increase in nitrate concentrations in the 1950’s, followed by a drop in the 1980’s in the Svalbard ice cores. A trend analysis of recent precipitation observations in Europe could not find any significant trends for nitrate in Ny-?lesund [9, 10]. In Europe and North America, the nitrogen emissions are expected to further decrease due to current and future legislations though there are regional differences which may affect the Arctic in particular. The expected intensification of shipping activity might lead to an increase of nitrogen emissions in the Arctic [4]. Reduction protocols and improvements in technology counteract the increase of nitrogen emissions, and some progress has been made in reducing emissions in the last decade [11,
Infectious disease management in primary care: perceptions of GPs
Ingeborg Bjrkman, Mats Erntell, Marta R?ing, Cecilia Lundborg
BMC Family Practice , 2011, DOI: 10.1186/1471-2296-12-1
Abstract: Twenty GPs working at primary care centres in a county in south-west Sweden were purposively selected based on the strategy of including GPs with different kinds of experience. The GPs were interviewed and perceptions among GPs were analysed by a phenomenographic approach.Five qualitatively different perceptions of infectious disease management were identified. They were: (A) the GP must help the patient to achieve health and well-being; (B) the management must meet the GP's perceived personal, professional and organisational demands; (C) restrictive antibiotic prescribing is time-consuming; (D) restrictive antibiotic prescribing can protect the effectiveness of antibiotics; and (E) patients benefit personally from restrictive antibiotic prescribing.Restrictive antibiotic prescribing was considered important in two perceptions, was not an issue as such in two others, and was considered in one perception although the actual prescribing was greatly influenced by the interaction between patient and GP. Accordingly, to encourage restrictive antibiotic prescribing several aspects must be addressed. Furthermore, different GPs need various kinds of support. Infectious disease management in primary care is complex and time-consuming, which must be acknowledged in healthcare organisation and planning.It has been demonstrated that the level of antibiotic use correlates with the level of antibiotic resistance [1-6]. Accordingly, it is important to keep the level of antibiotic prescribing low in order to contain the development of resistant bacteria.Antibiotic prescribing in primary care in Sweden decreased continuously between the early 1990s and 2004, when the trend was broken and usage unexpectedly began to increase in all counties in Sweden except one [7]. No parallel increase in the occurrence of infectious diseases was registered and no other explanations were found [8]. One of the greatest increases in antibiotic prescribing compared to other counties was documented in H
Muscle Functions in Polymyalgia Rheumatica and Giant-Cell Arteritis
Mikko P. Bj rkman and Reijo S. Tilvis
Healthy Aging & Clinical Care in the Elderly , 2012, DOI: 10.4137/HACCE.S5012
Abstract: Objectives: To find out whether and to what extent the muscle functions are impaired in polymyalgia rheumatica (PMR) patients in relation to duration, activity and treatment of the disease as well as any history of giant cell-arteritis (GCA). Methods: Comprehensive clinical examinations of PMR patients (N = 40) called to participate in a clinical rehabilitation trial included, among others, the polymyalgia rheumatica disease activity score (PMR-AS), cytokine profile, appendicular fat (aFMI) and muscle mass indices (aMMI) by dual X-ray absorbtiometry, mean hand grip strength of both hands (HGS) and force platform countermovement jump height (CJH). Results: Of the older PMR patients (57.2–80.9 years), five had a history of GCA. Neither aMMI nor aFMI was associated with age in these patients. The HGS correlated moderately with CJH (r = 0.629, P , 0.001). In multivariate regression analyses, old age (P = 0.003), low aMMI (P = 0.005), and high aFMI (P = 0.012) were independently associated with weak HGS, explaining 62.2% (R2 = 0.622) of its variation. Older age (P , 0.001), lower aMMI (P = 0.001) and higher aFMI (P , 0.001) also independently indicated lower CJH, explaining 75.3% (R2 = 0.753) of its variation. Muscle functions did not associate with disease characteristics of PMR or any history of GCA. Conclusions: Low muscle mass and adiposity are the most important determinants of impaired muscle function and are a target for prevention in older patients suffering from PMR.
Tomosynthesis in pulmonary cystic fibrosis with comparison to radiography and computed tomography: a pictorial review
Kristina Vult von Steyern,Isabella Bj rkman-Burtscher,Mats Geijer
Insights into Imaging , 2012, DOI: 10.1007/s13244-011-0137-9
Abstract: The purpose of this pictorial review is to illustrate chest imaging findings of cystic fibrosis (CF) using tomosynthesis (digital tomography), in comparison to radiography and computed tomography (CT). CF is a chronic systemic disease where imaging has long been used for monitoring chest status. CT exposes the patient to a substantially higher radiation dose than radiography, rendering it unsuitable for the often needed repeated examinations of these patients. Tomosynthesis has recently appeared as an interesting low dose alternative to CT, with an effective dose of approximately 0.08 mSv for children and 0.12 mSv for adults. Tomosynthesis is performed on the same X-ray system as radiography, adding only about 1 min to the normal examination time. Typical pulmonary changes in CF such as mucus plugging, bronchial wall thickening, and bronchiectases are shown in significantly better detail with tomosynthesis than with traditional radiography. In addition, the cost for a tomosynthesis examination is low compared to CT. To reduce the radiation burden of patients with CF it is important to consider low dose alternatives to CT, especially in the paediatric population. Tomosynthesis has a lower radiation dose than CT and gives a superior visualisation of pulmonary CF changes compared to radiography. It is important to further determine the role of tomosynthesis for monitoring disease progression in CF.
Comprehensive CT Evaluation in Acute Ischemic Stroke: Impact on Diagnosis and Treatment Decisions
Askell L?ve,Roger Siemund,Gunnar Andsberg,Mats Cronqvist,Stig Holt?s,Isabella Bjrkman-Burtscher
Stroke Research and Treatment , 2011, DOI: 10.4061/2011/726573
Abstract: Background. With modern CT imaging a comprehensive overview of cerebral macro- and microcirculation can be obtained within minutes in acute ischemic stroke. This opens for patient stratification and individualized treatment. Methods. Four patients with acute ischemic stroke of different aetiologies and/or treatments were chosen for illustration of the comprehensive CT protocol and its value in subsequent treatment decisions. The patients were clinically evaluated according to the NIHSS-scale, examined with the comprehensive CT protocol including both CT angiography and CT perfusion, and followed up by MRI. Results. The comprehensive CT examination protocol increased the examination time but did not delay treatment initiation. In some cases CT angiography revealed the cause of stroke while CT perfusion located and graded the perfusion defect with reasonable accuracy, confirmed by follow-up MR-diffusion. In the presented cases findings of the comprehensive CT examination influenced the treatment strategy. Conclusions. The comprehensive CT examination is a fast and safe method allowing accurate diagnosis and making way for individualized treatment in acute ischemic stroke. 1. Introduction Current guidelines for treatment of acute stroke by intravenous (IV) thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) [1, 2] are based on several large trials showing favorable results for this treatment within the 3- or 4.5-hour time window [3–9]. The main limitation has been the diminished benefit of IV-thrombolytic treatment beyond the given time frame. However, in these trials, the diagnosis of acute stroke was made clinically with supplementary nonenhanced computer tomography (NECT) examination to exclude intracranial hemorrhage and extensive early ischemic changes, both considered contraindications for thrombolytic treatment. No perfusion measurements or angiographic studies were carried out, which might have allowed treatment individualization and improved treatment results. Clinical evaluation and NECT examination are still the most important tools in the workup of acute ischemic stroke. With modern brain CT-imaging, a supplementary overview of cerebral macro- and microcirculation can be obtained in minutes with CT angiography (CTA) and CT perfusion, providing valuable information before or during treatment initiation. The aim of this study was to illustrate a comprehensive three-step CT imaging protocol for acute stroke consisting of NECT to exclude hemorrhage and other contraindications for IV-thrombolysis, contrast enhanced dynamic
Mid-Gestational Enlargement of Fetal Thalami in Women Exposed to Methadone during Pregnancy
Meredith Schulson,Anthony Liu,Tracey Bjrkman,Ann Quinton,Kristy P. Mann,Michael Peek,Ralph Nanan
Frontiers in Surgery , 2014, DOI: 10.3389/fsurg.2014.00028
Abstract: Methadone maintenance therapy is the standard of care in many countries for opioid-dependent women who become pregnant. Despite recent evidence showing significant neurodevelopmental changes in children and adults exposed to both licit and illicit substances in utero, data on the effects of opioids in particular remains scarce. The purpose of this study was to examine the effects of opiate use, in particular methadone, on various fetal cortical and biometric growth parameters in utero using ultrasound measurements done at 18–22 weeks gestation. Head circumference (HC), bi-parietal diameter, lateral ventricle diameter, transcerebellar diameter, thalamic diameter, cisterna magna diameter, and femur length were compared between fetuses born to methadone-maintained mothers and non-substance using controls. A significantly larger thalamic diameter (0.05 cm, p = 0.01) was observed in the opiate-exposed group. Thalamic diameter/HC ratio was also significantly raised (0.03 mm, p = 0.01). We hypothesize here that the increase in thalamic diameter in opiate-exposed fetuses could potentially be explained by regional differences in opioid and serotonin receptor densities, an alteration in monoamine neurotransmitter systems, and an enhancement of the normal growth increase that occurs in the thalamus during mid-gestation.
Reformas de saúde em perspectiva comparada: uma quest?o sem fim .... ou uma busca improvável
Bjrkman,James Warner;
Ciência & Saúde Coletiva , 2009, DOI: 10.1590/S1413-81232009000300012
Abstract: given the problematic nature of attempts to reform national delivery systems for health care, the paper reviews the context and logic of reforms in the health sector. after a background on approaches to building capacity within three generations of public sector reforms, it examines the reforms applied to financing, organizing and delivering health services and suggests strategies for reform that take capacity into account.
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