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- Dencker, Nils, et al.
(författare)
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The solvability and subellipticity of systems of pseudodifferential operators
- 2009
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Ingår i: Advances in Phase Space Analysis of Partial Differential Equations - In Honor of Ferruccio Colombini's 60th Birthday. - Boston : Birkhäuser Boston. - 2374-0280 .- 1421-1750. - 9780817648602 ; 78, s. 73-94
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Konferensbidrag (refereegranskat)abstract
- The paper studies the local solvability and subellipticity for square systems of principal type. These are the systems for which the principal symbol vanishes of first order on its kernel. For systems of principal type having constant characteristics, local solvability is equivalent to condition (Ψ) on the eigenvalues. This is a condition on the sign changes of the imaginary part along the oriented bicharacteristics of the real part of the eigenvalue. In the generic case when the principal symbol does not have constant characteristics, condition (Ψ) is not sufficient and in general not well defined. Instead we study systems which are quasi-symmetrizable, these systems have natural invariance properties and are of principal type. We prove that quasi-symmetrizable systems are locally solvable. We also study the subellipticity of quasi-symmetrizable systems in the case when principal symbol vanishes of finite order along the bicharacteristics. In order to prove subellipticity, we assume that the principal symbol has the approximation property, which implies that there are no transversal bicharacteristics.
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- Larsson, Jonas, 1968-, et al.
(författare)
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Cardiovascular Effects of Load Carriage in Soldiers; A Pilot Study
- 2019
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Ingår i: Book of Abstracts of the 24th Annual Congress of the European College of Sport Science – 3rd - 6th July 2019, Prague – Czech Republic. - : European College of Sport Science. - 9783981841428 ; , s. 422-423
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Konferensbidrag (refereegranskat)abstract
- Introduction: Previous studies have shown that risk of physical fatigue increases if prolonged average work intensity exceeds 50% of oxygen uptake (VO2). In order to avoid persistent fatigue in a work setting, it is important to conduct suitable work capacity analyses. In physically demanding jobs where wearing protective gear and/or external load is mandatory, monitoring of cardiovascular demands through heart rate (HR) is one way to track the workers’ relative effort. There are limited studies examining effects of load carrying on cardiovascular capacity where it appears that VO2peak differ when soldiers and firefighters are tested with work-related equipment/clothing compared to light clothing. The aim of this pilot study was to investigate effects of load (combat gear) on HR, VO2 and muscle oxygen saturation (SmO2) compared to no load in soldiers during a graded treadmill protocol.Methods: Eight volunteer army soldiers (1 woman, 7 men) performed a graded treadmill test until exhaustion. All soldiers performed the test twice, once with light clothes and no load (NL) and once with added load, their personal combat gear (CG), with at least 48 h between sessions. The treadmill protocol stages included supine and standing positions, followed by marching speeds of 5.4 km/h and 8 km/h at 0 incline (all 5 min) immediately followed by a set marching speed of 8 km/h with a starting incline of 2 % increasing the incline 2 % every third minute until voluntary exhaustion. Measurements of HR, VO2 and SmO2 were collected continuously and the last 30 s of each stage were averaged and used for statistical analyses (paired t-tests).Results: The mean added load for all soldiers with CG was 16.8 ± 1.1 kg. All soldiers completed at least 6 stages (range 6-11 stages) with both NL and CG, where time to exhaustion with NL was longer (19.1 ± 3.2 min) compared to CG (9.1 ± 2.9 min; p <0.01). Submaximal HR and VO2 were both significantly higher with CG compared to NL (at absolute intensities) at all marching speeds all soldiers completed (5.4 km/h 0 % grade - 8 km/h 4% grade; all p<0.05). For SmO2, marching with CG compared to NL resulted in increased muscle oxygen utilization, at submaximal stages 8 km/h 0% -4% grade (all p<0.05). For values at maximal effort the CG had a significantly lower VO2peak (3.7 ± 0.5 L/min) compared to NL (4.1 ± 0.6 L/min, p <0.01), whereas there was no difference in HRpeak or the lowest value of SmO2 between CG (193.1 ± 7.2 bpm; 42.4 ± 30.3%) and NL (195.4 ± 8.9 bpm; 47.0 ± 29.2%).Conclusions: This pilot study suggests that assessment of aerobic capacity in soldiers should be conducted with combat gear to help determine their actual work capacity during combat and other load carrying tasks. These results suggest that if soldiers’ work performance is determined without added load it overestimates their aerobic capacity (VO2peak) in tasks wearing combat gear, which might lead to added fatigability and deleterious effect on performance.
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- Larsson, Jonas, 1968-, et al.
(författare)
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Self-rated physical work demands for ground combat soldiers
- 2018
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Ingår i: PES 2018 3rd International Conference on Physical Employment Standards, University of Portsmouth, United Kingdom, 17-19 July 2018. ; , s. 31-31
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Konferensbidrag (refereegranskat)abstract
- Introduction: Military tasks are physically demanding, and the ability to achieve and maintain the physical capacity required to perform all military tasks are important. Previous studies in other countries have identified the most physically demanding work tasks to be carrying, lifting heavy loads, and digging. The aim of the present study was to identify the most physically demanding work tasks for Swedish ground combat soldiers and to study gender differences in perceived difficulty of the tasks.Methods: Based on procedural documentation, field manuals and job analyses, a questionnaire was developed that defined 30 work tasks for ground combat soldiers. To assess face and content validity, an expert focus group was used. The questionnaire was distributed to 231 ground combat soldiers, 165 of whom responded (71.4%), rating the perceived physical strain of the identified work tasks.Results: Of the 30 item work tasks included in the survey, five were selected as the most physically demanding. Transport of wounded was rated as the most demanding task both for aerobic endurance and strength. Other highly demanding tasks for aerobic capacity were low/high crawl, dismounted attack in close country, urban and rough terrain, and carrying heavy loads. For muscle strength demands there were a total of 11 different work task ranked for hand-, arm-, leg-, and core strength although many of them only occurred in one of the areas of interest. Carrying heavy loads were ranked in second place except for leg and core strength there it was in third place, instead high and low crawl was ranked very strenuous for leg and core strength. Care of wounded were ranked high for hand strength but not so hard for the rest of the areas.Conclusions: Swedish ground combat soldiers rate many tasks as physically demanding. Almost all the identified tasks were physically challenging and contains elements of lifting and carrying, which demand personnel’s muscular strength and muscular endurance capabilities for the soldiers. There were no significant differences in ranked physical requirements between male and female soldiers although they sometimes ranked the tasks in different order.
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