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Search Results: 1 - 10 of 43 matches for " Torbjorn Akerstedt "
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Social Support and Sleep. Longitudinal Relationships from the WOLF-Study  [PDF]
Maria Nordin, Peter Westerholm, Lars Alfredsson, Torbjorn Akerstedt
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.312A181

Aim: To investigate the relationship between two social support dimensions (network and emotional support) and sleep quality and between two social support sources (at and outside work) and sleep quality. Methods: The three-wave prospective Work Lipids and Fibrinogen (WOLF) study from Northern Sweden was used including 2420 participants who had filled out a questionnaire on working life, life style and health. Sleep quality was assessed by the Karolinska Sleep Questionnaire (KSQ). Structure and function of social support were measured as network support both at and outside work by Availability of Social Integration (AVSI) and emotional support both at and outside work by Availability of Attachment (AVAT). Logistic regression was used, utilizing variables created to assess development over time. Moreover, reversed causation was tested. Results: Improved network support at work decreased the risk of disturbed sleep (OR .65; 95% CI .47 - .90) as did improved emotional support outside work (OR .69; 95% CI .49 - .96). Reporting a constant poor network support at work increased the risk of disturbed sleep (OR 1.53, 95% CI 1.10 - 2.11) as did reporting a constant poor emotional support outside work (OR 1.46; 95% CI 1.02

In-Car Nocturnal Blue Light Exposure Improves Motorway Driving: A Randomized Controlled Trial
Jacques Taillard, Aurore Capelli, Patricia Sagaspe, Anna Anund, Torbjorn Akerstedt, Pierre Philip
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046750
Abstract: Prolonged wakefulness greatly decreases nocturnal driving performance. The development of in-car countermeasures is a future challenge to prevent sleep-related accidents. The aim of this study is to determine whether continuous exposure to monochromatic light in the short wavelengths (blue light), placed on the dashboard, improves night-time driving performance. In this randomized, double-blind, placebo-controlled, cross-over study, 48 healthy male participants (aged 20–50 years) drove 400 km (250 miles) on motorway during night-time. They randomly and consecutively received either continuous blue light exposure (GOLite, Philips, 468 nm) during driving or 2*200 mg of caffeine or placebo of caffeine before and during the break. Treatments were separated by at least 1 week. The outcomes were number of inappropriate line crossings (ILC) and mean standard deviation of the lateral position (SDLP). Eight participants (17%) complained about dazzle during blue light exposure and were removed from the analysis. Results from the 40 remaining participants (mean age ± SD: 32.9±11.1) showed that countermeasures reduced the number of inappropriate line crossings (ILC) (F(2,91.11) = 6.64; p<0.05). Indeed, ILC were lower with coffee (12.51 [95% CI, 5.86 to 19.66], p = 0.001) and blue light (14.58 [CI, 8.75 to 22.58], p = 0.003) than with placebo (26.42 [CI, 19.90 to 33.71]). Similar results were found for SDLP. Treatments did not modify the quality, quantity and timing of 3 subsequent nocturnal sleep episodes. Despite a lesser tolerance, a non-inferior efficacy of continuous nocturnal blue light exposure compared with caffeine suggests that this in-car countermeasure, used occasionally, could be used to fight nocturnal sleepiness at the wheel in blue light-tolerant drivers, whatever their age. More studies are needed to determine the reproducibility of data and to verify if it can be generalized to women. Trial Registration ClinicalTrials.gov NCT01070004
Effects of Sustained Sleep Restriction on Mitogen-Stimulated Cytokines, Chemokines and T Helper 1/ T Helper 2 Balance in Humans
John Axelsson, Javaid-ur Rehman, Torbjorn Akerstedt, Rolf Ekman, Gregory E. Miller, Caroline Olgart H?glund, Mats Lekander
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082291
Abstract: Background Recent studies suggest that acute sleep deprivation disrupts cellular immune responses by shifting T helper (Th) cell activity towards a Th2 cytokine profile. Since little is known about more long-term effects, we investigated how five days of sleep restriction would affect pro-inflammatory, chemotactic, Th1- and Th2 cytokine secretion. Methods Nine healthy males participated in an experimental sleep protocol with two baseline sleep-wake cycles (sleep 23.00 – 07.00 h) followed by 5 days with restricted sleep (03.00 – 07.00 h). On the second baseline day and on the fifth day with restricted sleep, samples were drawn every third hour for determination of cytokines/chemokines (tumor necrosis factor alpha (TNF-α), interleukin (IL) -1β, IL-2, IL-4 and monocyte chemoattractant protein-1 (MCP-1)) after in vitro stimulation of whole blood samples with the mitogen phytohemagglutinin (PHA). Also leukocyte numbers, mononuclear cells and cortisol were analysed. Results 5-days of sleep restriction affected PHA-induced immune responses in several ways. There was a general decrease of IL-2 production (p<.05). A shift in Th1/Th2 cytokine balance was also evident, as determined by a decrease in IL2/IL4 ratio. No other main effects of restricted sleep were shown. Two significant interactions showed that restricted sleep resulted in increased TNF-α and MCP-1 in the late evening and early night hours (p’s<.05). In addition, all variables varied across the 24 h day. Conclusions 5-days of sleep restriction is characterized by a shift towards Th2 activity (i.e. lower 1L-2/IL-4 ratio) which is similar to the effects of acute sleep deprivation and psychological stress. This may have implications for people suffering from conditions characterized by excessive Th2 activity like in allergic disease, such as asthma, for whom restricted sleep could have negative consequences.
Deposition of charged nano-particles in the human airways including effects from cartilaginous rings  [PDF]
Hans O. Akerstedt
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.310113
Abstract: This paper presents a numerical study of the deposition of spherical charged nano-particles caused by convection, Brownian diffusion and electrostatics in a pipe with a cartilaginous ring structure. The model describes the deposition of charged particles in the different generations of the tracheobronchial tree of the human lung. The upper airways are characterized by a certain wall structure called cartilaginous rings which modify the particle deposition when compared to an airway with a smooth wall. The problem is defined by solving Naver-Stokes equations in combination with a convective-diffusion equation and Gauss law for electrostatics. Three non- dimensional parameters describe the problem, the Peclet number Pe = 2ūa/D , the Reynolds number Re = ūa/v and an electrostatic parameter α=α2c0q2/(4ε0κT) . Here U is the mean velocity, a the pipe radius and D the diffusion coefficient due to Brownian motion given by D=κTCu/3πμd , where Cu is the Cunningham-factor Cu=1+λ/d(2.34+1.05exp(-0.39d/λ)) Here d is the particle diameter and λ the mean free path of the air molecules. Results are provided for generations G4-G16 of the human airways. The electrostatic parameter is varied to model different concentrations and charge numbers.
PYTHIA 5.7 and JETSET 7.4 Physics and Manual
Torbjorn Sjostrand
Physics , 1995,
Abstract: This is the latest edition of the physics description and manual of the PYTHIA and JETSET programs for event generation in High Energy Physics.
QCD Physics Lessons of Z0 Decay
Torbjorn Sjostrand
Physics , 1995,
Abstract: This talk contains a subjective selection of interesting results on Z$^0$ decays, presented by the LEP and SLC groups. The emphasis is on soft and semihard QCD physics. Results are put in a theoretical context, and the limits of our current understanding are stressed. Topics covered include event measures, prompt photons, coherence and string effects, data and theory for particle rates and spectra, particle correlations and Bose--Einstein effects.
Soft Photoproduction Physics
Torbjorn Sjostrand
Physics , 1996, DOI: 10.1088/0954-3899/22/6/006
Abstract: Several topics of interest in soft photoproduction physics are discussed. These include jet universality issues (particle flavour composition), the subdivision into event classes, the buildup of the total photoproduction cross section and the effects of multiple interactions.
Qualifying and Quantifying IT Services Added Values in Outsourcing Assignments—Service Value Agreement  [PDF]
Merat Ziyarazavi, Christer Magnusson, Torbjorn Tergesten
Journal of Service Science and Management (JSSM) , 2012, DOI: 10.4236/jssm.2012.54038
Abstract: Traditionally, a Service Level Agreement (SLA) including service level metrics is used as an appendix in IT Service Management agreements to define the terms and conditions of delivery and set expectations. However, SLA neither implies nor guarantees the added values that are expected by the customer. Besides, due to the nature of IT services, there always exists uncertainty about the agreed services due to which the perceived risk for both customer and provider is high. Moreover, the quality and quantity of delivered values are mostly hidden by hazy marketing slogans. In order to guarantee the values of an offered service, the deliverable added values should be characterized properly, quantified by means of measurable metrics, and agreed upon between the two parties. Such comprehensive material, including the deliverable added values along with their measurable metrics, is called Service Value Agreement (SVA). This research proposes a platform for IT service offerings based on added values by identifying, as well as quantifying, an organization’s objectives in purchasing Application Management (AM) services from a provider firm.
After Hierarchy? Domestic Executive Governance and the Differentiated Impact of the European Commission and the Council of Ministers
Larsson,Torbjorn; Trondal,Jarle
European Integration Online Papers , 2005,
Abstract: This study offers an organisation theory approach that claims that the differentiated organisational constellation of the European Union contributes to a differentiated Europeanisation of domestic core-executives. It is argued that the European Commission mainly activates the lower echelons of the domestic government hierarchies, notably professional experts within sector ministries and agencies. Furthermore, the European Commission arguably weakens domestic politico-administrative leadership, the Foreign Office and the Prime Ministers Office. By contrast, the Council of Ministers arguably strengthens domestic politico-administrative leadership, the Foreign Office and the Prime Ministers Office. A comparative analysis of the decision-making processes within the central administrations of Norway and Sweden is offered. Based on a rich body of survey and interview data this analysis reveals that multi-level interaction of administrative systems between the European Commission and the Norwegian and Swedish central administrations occur largely outside the control of the domestic politico-administrative leadership, Prime Ministers Office and Foreign Office. In Sweden this tendency is to some extent counterbalanced by the inter-sectorally interlocking effect of the Council of Ministers.
Reversal of the Charge Transfer between Host and Dopant Atoms in Semiconductor Nanocrystals
Torbjorn Blomquist,George Kirczenow}
Physics , 2004, DOI: 10.1021/nl049108t
Abstract: We present ab initio density functional calculations that show P (Al) dopant atoms in small hydrogen-terminated Si crystals to be negatively (positively) charged. These signs of the dopant charges are reversed relative to the same dopants in bulk Si. We predict this novel reversal of the dopant charge (and electronic character of the doping) to occur at crystal sizes of order 100 Si atoms. We explain it as a result of competition between fundamental principles governing charge transfer in bulk semiconductors and molecules and predict it to occur in nanocrystals of most semiconductors.
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