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Search Results: 1 - 10 of 119538 matches for " Hans O. Akerstedt "
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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.
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
Abstract:

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

An International Trade Model with Entrepreneurs and Financial Markets  [PDF]
Bodil O. Hansen, Hans Keiding
Technology and Investment (TI) , 2016, DOI: 10.4236/ti.2016.73012
Abstract:
We consider a two-period model of a three-country world with free trade in finished products and some factor mobility, where production is subject to uncertainty. Enterpreneurs may establish production in other countries but can obtain financing only in the country of origin. In this model, integrating production across countries, in particular integrating economically strong and weak partners, may give rise to a welfare loss, showing that traditional views on efficiency of international trade must be reconsidered when risk and uncertainty are taken into account.
Numerical Investigation of Turbulent Flow through Rectangular and Biconvex Shaped Trash Racks  [PDF]
Hans O. ?kerstedt, Sebastian Eller, T. Staffan Lundstr?m
Engineering (ENG) , 2017, DOI: 10.4236/eng.2017.95024
Abstract: Turbulent flow through a trash rack of bars of rectangular and biconvex shapes is considered. A trash rack is composed of an array of bars fitted into a hydro-electric power station to prevent debris and fish to enter the waterway towards the turbine. The work is directed towards modeling a large number of bars for which the flow turn out to have a periodic structure. It is here shown that this case can be simplified with the flow past a single bar together with periodic boundary conditions. Using this approach the head loss is derived for different angles of attack α and blockages P for two shapes of the rack, a rectangular bar and an aerodynamically shaped biconvex bar. It is found that overall loss of the biconvex bars is in general about 15% of the loss for the rectangular case for small angles of attack. For large angle of attack this difference diminishes. Of interest for the biconvex bars is also a local minimum in the head loss for angles approximately greater than 20° and for a blockage P around 0.35. This combination of parameters gives a low loss together with an efficient barrier for debris and fishes.
Which factors decided general practitioners’ choice of hospital on behalf of their patients in an area with free choice of public hospital? A questionnaire study
Hans O Birk, Lars O Henriksen
BMC Health Services Research , 2012, DOI: 10.1186/1472-6963-12-126
Abstract: Retrospective questionnaire study of all of the 474 GPs practising in three counties which constituted a single uptake area. Patients were free to choose a hospital in another county in the country. The GPs were asked about responsibility for choice of the latest three patients referred by the GP to hospital; which of 16 factors influenced the choice of hospital; which of 15 sources of information about clinical quality at various hospitals/departments were considered relevant, and how often were six sources of information about waiting time utilised.Fifty-one percent (240 GPs) filled in and returned the questionnaire. One hundred and eighty-three GPs (76%) reported that they perceived that they chose the hospital on behalf of the latest referred patient. Short distance to hospital was the most common reason for choice of hospital.The most frequently used source of information about quality at hospital departments was anecdotal reports from patients referred previously, and the most important source of information about waiting time was the hospitals’ letters of confirmation of referrals.In an area with free choice of public hospital most GPs perceived that they chose the hospital on behalf of patients. Short distance to hospital was the factor which most often decided the GPs’ choice of hospital on behalf of patients. GPs attached little weight to official information on quality and service (waiting time) at hospitals or departments, focusing instead on informal sources like feedback from patients and colleagues and their experience with cooperation with the department or hospital.
The effect of cartilaginous rings on particle deposition by convection and Brownian diffusion  [PDF]
Hans O. ?kerstedt, Sofie M. H?gberg, T. Staffan Lundstr?m, Thomas Sandstr?m
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.27097
Abstract: The deposition of spherical nanoparticles by convection and Brownian diffusion in a pipe with a cartilaginous ring structure is studied. Analytical results for a fully developed flow are found for small amplitude rings using the interactive boundary layer theory. It is found that the local deposition rate is at maximum at a position approximately one twelfth of the spacing between the rings before the minimum cross section of the tube. For larger ring amplitudes the problem is solved numerically and separation then takes place in the depressions between the rings, and maximum deposition is found at the point of reattachment of the flow approximately at the same point as in the analytical theory. Cumulative deposition results are also provided with larger deposition rates with the inclusion of the cartilaginous rings. Deposition results for a developing flow are also provided. For the same volume flux as for fully developed flow the deposition is about 25% larger. In general conclusions about the position of maximum deposition rate from the analytic theory of fully developed flow also applies qualitatively to the case of developing flow.
How many systolic and diastolic variables must be measured in elderly patients with symptoms of heart failure?  [PDF]
Jan B. Remmets, Mona K. Olofsson, Hans Stenlund, Kurt O. Boman
World Journal of Cardiovascular Diseases (WJCD) , 2012, DOI: 10.4236/wjcd.2012.22017
Abstract: Objectives: To explore the concordance and the feasibility of obtaining systolic or diastolic variables of left ventricular function in elderly patients with heart failure symptoms. Methods: One hundred twenty four patients with symptoms of heart failure (mean age 77 years, 70% females) were included in a cross-sectional, explorative study. Nineteen echocardiographic variables (7 systolic and 12 diastolic) were measured. Results: Overall, feasibility ranged from 93% to 100% for 15 variables and was 48% for mitral regurgitation dp/dt(MRdp/dt), 66% for the difference between pulmonary AR-dur and mitral A-dur, 81% for the ratio between early and late mitral inflow velocity (E/A), and 76% for tissue Doppler imaging late dia-stolic velocity (TDI A’). Concordance was very good/ good in 83% and poor/missing in 17% of systolic variables, whereas it was very good/good for 67% of diastolic variables and poor/missing for 33%. Factor analysis reduced systolic variables to two factors that explained 69% of the total variance in systolic function. Conclusions: Low feasibility for some and questionable concordance of especially diastolic variables questions the rationale for routinely measuring a high number of echocardigraphic variables. The results of the factor analysis further strengthen the possibility of reducing the number of measured variables. The clinical value of such a reduction needs to be validated.
Reincentivizing – a new theory of work and work absence
Hans O Thulesius, Birgitta E Grahn
BMC Health Services Research , 2007, DOI: 10.1186/1472-6963-7-100
Abstract: We used classic grounded theory for analyzing data from >130 interviews with people working or on sick leave, physicians, social security officers, and literature. Several hundreds of typed and handwritten memos were the basis for writing up the theory.In this paper we present a theory of work incentives and how to deal with work absence. We suggest that work disability can be seen as hurt work drivers or people caught in mode traps. Work drivers are specified as work capacities + work incentives, monetary and non-monetary. Also, people can get trapped in certain modes of behavior through changed capacities or incentives, or by inertia. Different modes have different drivers and these can trap the individual from reincentivizing, ie from going back to work or go on working. Hurt drivers and mode traps are recognized by driver assessments done on several different levels. Mode driver calculations are done by the worker. Then follows employer, physician, and social insurance officer assessments. Also, driver assessments are done on the macro level by legislators and other stakeholders. Reincentivizing is done by different repair strategies for hurt work drivers such as body repair, self repair, work-place repair, rehumanizing, controlling sick leave insurance, and strengthening monetary work incentives. Combinations of these driver repair strategies also do release people from mode traps.Reincentivizing is about recognizing hurt work drivers and mode traps followed by repairing and releasing the same drivers and traps. Reincentivizing aims at explaining what is going on when work absence is dealt with and the theory may add to social psychological research on work and work absence, and possibly inform sick leave policies.The sickness absence rate in Sweden is one of the highest in the world [1]. Sweden has generous sick leave policies and strong job protection legislation. There is no upper time limit for sick leave, and a low risk of loosing employment due to sicknes
A Factor-Graph Representation of Probabilities in Quantum Mechanics
Hans-Andrea Loeliger,Pascal O. Vontobel
Mathematics , 2012,
Abstract: A factor-graph representation of quantum-mechanical probabilities is proposed. Unlike standard statistical models, the proposed representation uses auxiliary variables (state variables) that are not random variables.
Factor Graphs for Quantum Probabilities
Hans-Andrea Loeliger,Pascal O. Vontobel
Computer Science , 2015,
Abstract: A factor-graph representation of quantum-mechanical probabilities (involving any number of measurements) is proposed. Unlike standard statistical models, the proposed representation uses auxiliary variables (state variables) that are not random variables. All joint probability distributions are marginals of some complex-valued function q, and it is demonstrated how the basic concepts of quantum mechanics relate to factorizations and marginals of q.
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