| 1. |
- Bogo, Renata, et al.
(författare)
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Prevalence, Incidence Proportion, and Heritability for Tinnitus : A Longitudinal Twin Study
- 2017
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Ingår i: Ear and Hearing. - 0196-0202 .- 1538-4667. ; 38:3, s. 292-300
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The purpose of this longitudinal twin study was to explore the effect of tinnitus on hearing thresholds and threshold shifts over two decades and to investigate the genetic contribution to tinnitus in a male twin cohort (n = 1114 at baseline and 583 at follow-up). The hypothesis was that participants with faster hearing deterioration had a higher risk for developing tinnitus and there is an underlying role of genetic influences on tinnitus.DESIGN: Male mono- and dizygotic twin pairs, born between 1914 and 1958 were included. Mixed models were used for comparison of hearing threshold shifts, adjusted for age. A co-twin comparison was made within pairs discordant for tinnitus. The relative influence of genetic and environmental factors was estimated by genetic modeling.RESULTS: The overall prevalence of tinnitus was 13.5% at baseline (x age 50) and 34.4% at follow-up (x age 67). The overall incidence proportion was 27.8%. Participants who reported tinnitus at baseline or at both time points were older. At baseline, the hearing thresholds differed between tinnitus cases and controls at all frequencies. New tinnitus cases at follow-up had the greatest hearing threshold shift at the high-frequency area compared with the control group. Within pairs, the tinnitus twin had poorer hearing than his unaffected co-twin, more so for dizygotic than monozygotic twin pairs. The relative proportion of additive genetic factors was approximately 0.40 at both time points, and the influence of individual-specific environment was 0.56 to 0.61. The influence of genetic factors on tinnitus was largely independent of genetic factors for hearing thresholds.CONCLUSIONS: Our hypotheses were confirmed: The fastest hearing deterioration occurred for new tinnitus cases. A moderate genetic influence for tinnitus was confirmed.
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| 2. |
- Johnson, Ann-Christin, et al.
(författare)
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Influence of well-known risk factors for hearing loss in a longitudinal twin study
- 2017
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Ingår i: International Journal of Audiology. - : Informa UK Limited. - 1499-2027 .- 1708-8186. ; 56, s. 63-73
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim was to investigate the influence of environmental exposures on hearing loss in a twin cohort.STUDY SAMPLE: Male twins born 1914-1958, representing an unscreened population, were tested for hearing loss at two occasions, 18 years apart.DESIGN: Clinical audiometry and a questionnaire were performed at both time points in this longitudinal study. Noise and solvent exposure were assessed using occupational work codes and a job exposure matrix. Hearing impairment was investigated using two different pure tone averages: PTA4 (0.5, 1, 2, and 4 kHz) and HPTA4 (3, 4, 6, and 8 kHz).RESULTS: Age affected all outcome measures. Noise exposure between time point one and two affected the threshold shifts of PTA4 and HPTA4 more in participants with a pre-existing hearing loss at time point one. Lifetime occupational noise exposure was a risk factor especially for the low-frequency hearing threshold PTA4. Firearm use was a statistically significant risk factor for all outcome measures.CONCLUSIONS: Pre-existing hearing loss can increase the risk of hearing impairment due to occupational noise exposure. An increased risk for NIHL was also seen in the group with exposures below 85 dB(A), a result that indicates awareness of NIHL should be raised even for those working in environments where sound levels are below 85 dB(A).
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| 3. |
- Bernhard, Jonte, 1953-, et al.
(författare)
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Alternating currents first : Experiences from designing a novel approach to teaching electric circuit theory
- 2016
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Ingår i: 44th Annual Conference of the European Society for Engineering Education - Engineering Education on Top of the World. - : European Society for Engineering Education (SEFI). - 9782873520144
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Konferensbidrag (refereegranskat)abstract
- BACKGROUND: Commonly in electric circuit theory courses, circuit laws are first introduced in the context of direct current (DC) electricity and first thereafter are alternating currents (AC) introduced. The extension of DC-theory to AC is quite easily done mathematically but is conceptually difficult for students. Engineering students have difficulties in understanding phase relationships and phasor representations in AC-electricity. Indeed, it has been suggested that phase should be seen as a threshold concept.PURPOSE: The purpose of this study was to investigate if a re-designed introductory electric circuit course could improve students’ understanding of important concepts in AC-electricity.METHOD and COURSE DESIGN: The course was re-designed introducing AC and DC electricity simultaneously. DC was introduced as a special case of AC with requency equals zero. The re-designed course was taught for the first time during the spring semester 2014 and a new textbook was written. A conceptual test was developed and first administered in 2013 to serve as a baseline and in subsequent years to evaluate the revised course. In 2014 the students’ courses of action in selected lab-groups were video-recorded.RESULTS: In the first revision cycle many students had difficulties to complete the labs in time. Students revealed a mixed response towards the revised course and the results on the conceptual test showed neglible improvement. In the second cycle revisions the number tasks were reduced and focus was laid on tasks that were identified as most important for contributing to the development of student understanding. As a result the learning gain improved with an effect size (Cohen’s delta) of 0.56. Also the course and the textbook were very well appreciated. In the third cycle only small revisions are made.CONCLUSION: The results show that that AC-electricity can be taught concurrently with DC. However, two revisions cycles was needed which demonstrates that curriculum development needs a sustained effort over a considerable period of time with continuous revisions in light of gained experiences. In further revision we will continue to refine the labs and to develop appropriate interactive lecture demonstrations for the lectures and to develop the problems.
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| 4. |
- Bogo, Renata, et al.
(författare)
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The Role of Genetic Factors for Hearing Deterioration Across 20 Years : A Twin Study
- 2015
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Ingår i: The journals of gerontology. Series A, Biological sciences and medical sciences. - : Oxford University Press (OUP). - 1079-5006 .- 1758-535X. ; 70:5, s. 647-653
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Tidskriftsartikel (refereegranskat)abstract
- Background. Hearing deterioration at advanced ages is associated with environmental exposures (eg, to noise and solvents) and genetic influences may also be important. Little is known about the role of genetic influences on hearing when evaluated longitudinally. We sought to investigate longitudinal hearing loss in a cohort of adult male twins to evaluate the importance of genetic and environmental factors for hearing deterioration over time. Methods. Hearing using conventional clinical audiometry was assessed in 583 male twins (128 monozygotic twin pairs and 111 dizygotic twin pairs) aged 34-79 at baseline and again two decades later. The hearing thresholds at two time points were compared at each frequency and in two different frequency regions. Genetic analyses were based on structural equation models. Bivariate Cholesky decomposition was used for longitudinal analysis. Results. The prevalence of hearing loss increased over time in better and worse ear. The hearing threshold shift was more pronounced in the high-frequency region, especially at 8000 Hz. Genetic influences were moderate (heritability: 53%-65%) for pure-tone averages at both lower and higher frequencies, and were of equal magnitude at baseline and follow-up. In contrast, environmental influences were of substantial importance (55%-88%) for rate of change of the hearing threshold over the 18-year period. Conclusions. Genetic factors are of considerable importance for level of hearing acuity, but environmental factors are more important for rate of change over an 18-year period.
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| 5. |
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| 6. |
- Ulvcrona, Kristina, et al.
(författare)
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Identifying the biological effects of pre-commercial thinning on diameter growth in young Scots pine stands
- 2014
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 29, s. 427-435
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Tidskriftsartikel (refereegranskat)abstract
- Data from seven Scots pine (Pinus sylvestris L.) stands in central Sweden that had undergone pre-commercial thinning (PCT) were used to investigate the biological effect of PCT on the diameter at breast height (DBH) growth of the remaining trees. Two treatments were considered: a PCT treatment and a control (C) with no PCT. The DBH of the trees in each stand was measured on up to four occasions over 15 years. We examined mean DBH and DBH growth of the largest 300, 600, 900 and 1200 trees ha-1. Two methods of selecting the trees used to calculate the mean DBH values for each measurement occasion were considered: the actual mean DBH (Dma), which is based on the DBH distribution of the trees on the measurement occasion in question, and the genuine mean DBH (Dmg), which is based on the DBH distribution of the trees on the final measurement occasion of the study and therefore focuses on the same set of trees for all measurement occasions. There was no clear difference between the Dma- and Dmg-based DBH increments, but the Dmg values tended to be somewhat larger both for the C and PCT treatments. Over a 15-year period, the relative mean yearly increments (Dma/Dmg) for different tree size classes ranged from 0.91 to 0.98, with lower values for the C treatment and larger DBH size classes. We found that PCT promotes DBH growth: over a 15-year period, the increased growth amounted to about 2.0 mm year-1 compared to the trees in unthinned plots.
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| 7. |
- Yu, Zhaohua, 1983-, et al.
(författare)
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Green light laser exposure at 532nm near the exposure limit during a human volunteer vehicle driving task does not alter structure or function in the visual system
- 2014
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Ingår i: Journal of laser applications. - Melville : Laser Institute of America. - 1042-346X .- 1938-1387. ; 26:2, s. 022009-1-022009-7
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to verify nonexistence of clinically important pathological effects to the visual system after exposure to 532 nm green laser light close to the exposure limit. The present medical surveillance of vision and visual health reported in this paper is the conjunction with a study of driver performance in the presence of 532 nm laser induced glare. The driving time varied between 25 and 55 s, depending on background luminance. The laser was on during the complete test drive. The peak corneal irradiance typically was 3.5Wm2 in one test drive. Considering a typical test drive, the typical time integrated corneal radiant exposure for one test drive was estimated to be 53 J/m2. The number of test drives varied among drivers but was typically 50, thus resulting in a cumulative corneal exposure dose of approximately 2.7 kJ/m2. Altogether, ten subjects were recruited according to inclusion and exclusion criteria. All ten subjects were examined for visual acuity, intraocular pressure, contrast sensitivity, color vision, monocular reading speed, and eye structure with clinical slit-lamp microscopy examination and indirect retinoscopy. All subjects were examined before exposure, immediately after exposure, and finally within an interval between 1 week and 4 weeks after exposure. There was no significant change of visual acuity, intraocular pressure, contrast sensitivity, color vision, or monocular reading speed between before and after exposure. No abnormal ocular structure was detected after exposure. This study demonstrates that close to exposure limit, exposure to 532 nm green laser light during a vehicle driving task does not induce structural or functional damage to the human visual system as observed in the interval minutes to weeks after exposure.
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| 8. |
- Steinvall, Ove, et al.
(författare)
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Laser dazzling impacts on car driver performance
- 2013
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Konferensbidrag (refereegranskat)abstract
- A growing problem for the Police and Security Forces has been to prevent potentially hostile individuals to pass a checkpoint, without using lethatl violence. Therefore the question has been if there is a laser or any other strong light source that could be used as a warning and dazzling device, without lethal or long term effects. To investigate the possibilities a field trial has been performed at a motor-racing track. A green CW laser with an irradiance on the eye of maximum 0.5 MPE, as defined by ICNIRP [1] and the ANZI standard [2], was used as a dazzle source. Ten drivers have been driving with dipped headlights through a course of three lines with orange cones. In every line there has been only one gate wide enough to pass without hitting the cones. The time through the course, the choice of gates and the number of cones hit have been measured. For every second trial drive through the track, the driver was exposed to the laser dazzler. The background illuminances ranged from a thousand lux in daylight to about ten millilux in darkness. The protective effect of the sun-visor of the car was investigated. The drives visual system was carefully examined before and after experimental driving and a few weeks after the experimental driving to verify that no pathological effects, that could potentially be induced by the laser exposure, pre-existed or occurred after the laser exposure. An analysis of variance for a within subjects design has been used for evaluation. It was found that green laser light can have an obvious warning effect in daylight. Dazzling does reduce the drivers ability to make judgments and manouver the car in twilight and darkness. A sun-visor can reduce the glare and give the driver an improved control, but that perception can be unjustified. No damage to the visual system was observed.
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| 9. |
- Karlsson, Kjell, et al.
(författare)
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Fältdatasystem för skogliga fältförsök
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport beskriver ett Internet-baserat system anpassat för att hantera träd-data från skogliga fältförsök. Systemet har konstruerats för att uppfylla ett flertal krav. Systemet erbjuder säker långtidslagring av skogliga fältförsöksdata, tillgänglighet överallt och när som helst utan behov av jourhavande administratör, datorstöd vid revision av fältförsök, samt tillhandahåller sammanställningar av tillståndet på försöksytor vid olika revisioner (statistikkort) och digitala dataset för statistiska analyser. I systemet ingår ett skräddarsytt datorprogram att användas i handdatorer för utomhusbruk vid revision av skogliga fältförsök. Rapporten inkluderar en detaljerad beskrivning av hur insamlad fältdata bearbetas för olika presentationer över skogstillståndet på skogliga försöksytor.
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| 10. |
- Nilsson, Urban, et al.
(författare)
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Productivity of Norway Spruce Compared to Scots Pine in the Interior of Northern Sweden
- 2012
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 46, s. 197-209
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Tidskriftsartikel (refereegranskat)abstract
- Productivity of Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) was studied in 12 paired plots in the interior of northern Sweden. Stands were established between 1928 and 1959; yield plots were established between 1974 and 1983 during pre-commercial thinning of the stands. Gross stem-wood production was significantly higher for Scots pine than for Norway spruce, stem-wood production by Norway spruce being 29.4% that of Scots pine. The site index for Norway spruce was lower than for Scots pine at all sites except one; the average difference in site index was 4.8 m. The simulated maximum mean annual increment (MAI(max)) during the rotation was 19% higher than the MAI(max) estimated with the site index for Scots pine, whereas simulated MAI(max) and MAI(max) estimated from the site index was about the same for Norway spruce. The simulations also indicated that MAI peaked about 50 years later for Norway spruce than for Scots pine. More small trees were included in the diameter distribution of Norway spruce than of Scots pine resulting in a lower stem-wood volume for Norway spruce when stands with the same dominant height were compared. This study shows that the difference in growth and rotation length between Scots pine and Norway spruce has implications when choosing which species to grow in the interior of northern Sweden.
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