| 109391. |
- Kröger, Ronald, et al.
(författare)
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Space-saving advantage of an inverted retina.
- 2009
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Ingår i: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 49:18, s. 2318-2321
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Tidskriftsartikel (refereegranskat)abstract
- Vertebrate eyes are of the simple or camera type with a single optical system that creates an image on the retina in the back of the eye. There, the visual information is encoded as nervous signals by photoreceptors, processed by retinal neurons, and then sent to the brain via the optic nerve. Surprisingly at first sight, the retinal neurons are located between the lens and the light-sensitive parts of the photoreceptors. The tissue scatters some light, which leads to loss of light and image blur. The inverted retina has, therefore, long been regarded as inferior. Here, we provide evidence that the inverted retina actually is a superior space-saving solution, especially in small eyes. The inverted retina has most likely facilitated the evolution of image-forming eyes in vertebrates, and it still benefits especially small and highly visual species.
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| 109392. |
- Kröger, Ronald, et al.
(författare)
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Suspension and optical properties of the crystalline lens in the eyes of basal vertebrates.
- 2014
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Ingår i: Journal of Morphology. - : Wiley. - 1097-4687 .- 0362-2525. ; 275:6, s. 613-622
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the apparatus suspending the crystalline lens in the eyes of basal vertebrates. Data are presented for Holocephali (Chondrichthyes) and the actinopterygians Polypteriformes, Polyodontidae (Acipenseriformes), Lepisosteiformes, Amiiformes, and one teleost species, the banded archerfish (Toxotes jaculatrix). We also studied the optical properties of the lens in Polypteriformes, Lepisosteiformes, and the archerfish. Together with previously published results, our findings show that there are three basic types of lens suspension in vertebrates. These are i) a rotationally symmetric suspension (Petromyzontida, lampreys; Ceratodontiformes, lungfishes; Tetrapoda), ii) a suspension with a dorso-ventral axis of symmetry and a ventral papilla (all Chondrichthyes and Acipenseriformes), and iii) an asymmetric suspension with a ventral muscle and a varying number of ligaments (all Actinopterygii except for Acipenseriformes). Large eyes with presumably high spatial resolution have evolved in all groups. Multifocal lenses creating well-focused color images are also present in all groups studied. Stable and exact positioning of the lens, in many cases in combination with accommodative changes in lens position or shape, is achieved by all three types of lens suspension. It is somewhat surprising that lens suspensions are strikingly similar in Chondrichthyes and Acipenseriformes (Actinopterygii), while the suspension apparatus in Polypteriformes, usually being regarded as an actinopterygian group more basal than Acipenseriformes, are considerably more teleostean-like. This study completes a series of investigations on lens suspensions in nontetrapod vertebrates, covering all major groups except for the rare and highly derived coelacanths.
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| 109393. |
- Kröger, Ronald, et al.
(författare)
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The physics of light in air and water.
- 2008
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Ingår i: Sensory Evolution on the Threshold - Adaptations in Secondarily Aquatic Vertebrates. - 9780520252783 ; , s. 113-119
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 109394. |
- Kröger, Ronald
(författare)
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Towards prevention of myopia
- 2002
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Ingår i: The Baltic Eye. ; 2, s. 4-11
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 109395. |
- Krøijer, Stine, et al.
(författare)
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Ny jordreform i Danmark
- 2022
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Annan publikation (populärvet., debatt m.m.)abstract
- Changing societal challenges and priorities call for new ways of managing agricultural land and for new forms of land ownership. The Danish pilot programme for multifunctional land consolidation (MUFJO) is seen as a frontrunner for a larger land reform. The programme ensures collective planning and long-term solutions, but cannot alone ensure the goals for re-wetting agricultural lands as stipulated in the Danish agricultural climate agreement, nor a more democratic land governance. It is time to deliver on the political ambition of a larger land reform in Denmark.
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| 109396. |
- Krøjer, S., et al.
(författare)
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Demonstrating Majorana non-Abelian properties using fast adiabatic charge transfer
- 2022
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Ingår i: Physical Review B. - 2469-9950. ; 105
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Tidskriftsartikel (refereegranskat)abstract
- Demonstration of Majorana non-Abelian properties is a major challenge in the field of topological superconductivity. In this work, we propose a minimal device and protocol for testing non-Abelian properties using charge-transfer operations between a quantum dot and two Majorana bound states combined with reading the parity state using a second dot. We use an adiabatic perturbation theory to find fast adiabatic paths to perform operations and to account for nonadiabatic errors. We find the ideal parameter sweep and a region in parameter space that reduces the charge-transfer operation time 1–2 orders of magnitude with respect to constant velocity driving. Using realistic parameters, we estimate that the lower bound for the timescale can be reduced to ∼10 ns. Deviations from the ideal parameters lead to the accumulation of an undesired dynamical phase, affecting the outcome of the proposed protocol. We furthermore suggest to reduce the influence from the dynamical phase using a flux echo. The echo protocol is based on the 4π periodicity of the topological state, absent for trivial bound states.
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| 109397. |
- Krøll, L. S., et al.
(författare)
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Has aerobic exercise effect on pain perception in persons with migraine and coexisting tension-type headache and neck pain? A randomized, controlled, clinical trial
- 2018
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Ingår i: European Journal of Pain. - : Wiley. - 1090-3801. ; 22:8, s. 1399-1408
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Tidskriftsartikel (refereegranskat)abstract
- Background: A large subset of persons with migraine suffers from coexisting tension-type headache and neck pain which may adversely affect the prognosis of migraine. Aerobic exercise has been shown to decrease migraine burden in these persons. Therefore, the aim of this study was to investigate whether the effect of aerobic exercise in persons with migraine and coexisting tension-type headache and neck pain can be explained by changes in pain perception. Method: Seventy consecutively recruited persons with migraine and coexisting tension-type headache and neck pain were randomized into exercise group or control group. Aerobic exercise consisted of bike/cross-trainer/brisk walking for 45 min, three times/week for 3 months. Controls continued their usual daily activities. Pericranial tenderness, pain thresholds, supra-thresholds and temporal summation were assessed at baseline, after treatment and at follow-up (6 months from baseline). Results: Fifty-two persons with migraine and coexisting tension-type headache and neck pain completed the study. Aerobic exercise did not induce consistent changes in nociceptive pathways measured by pericranial tenderness, pressure pain thresholds and sensitivity to electrical stimulation. Conclusion: The effect of aerobic exercise cannot be explained by measurable effects on the pain modulation system. Thus, the positive effect on migraine burden may rather be explained by positive alteration of avoidance behaviour. Aerobic exercise can be recommended as a safe and inexpensive migraine treatment strategy. Significance: This study adds further knowledge about the positive effect of aerobic exercise for persons with migraine and coexisting tension-type headache and neck pain. This effect cannot be measured by changes in pain modulation, but may rather be explained by positive alteration of avoidance behaviour.
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| 109398. |
- Krøll, Lotte Skytte, et al.
(författare)
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Level of physical activity, well-being, stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain
- 2017
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Ingår i: Journal of Headache and Pain. - : Springer Science and Business Media LLC. - 1129-2369 .- 1129-2377. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The prevalence of migraine with co-existing tension-type headache and neck pain is high in the general population. However, there is very little literature on the characteristics of these combined conditions. The aim of this study was to investigate a) the prevalence of migraine with co-existing tension-type headache and neck pain in a clinic-based sample, b) the level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain compared to healthy controls, c) the perceived ability of persons with migraine and co-existing tension-type headache and neck pain to perform physical activity, and d) which among the three conditions (migraine, tension-type headache or neck pain) is rated as the most burdensome condition. Methods: The study was conducted at a tertiary referral specialised headache centre where questionnaires on physical activity, psychological well-being, perceived stress and self-rated health were completed by 148 persons with migraine and 100 healthy controls matched by sex and average age. Semi-structured interviews were conducted to assess characteristics of migraine, tension-type headache and neck pain. Results: Out of 148 persons with migraine, 100 (67%) suffered from co-existing tension-type headache and neck pain. Only 11% suffered from migraine only. Persons with migraine and co-existing tension-type headache and neck pain had lower level of physical activity and psychological well-being, higher level of perceived stress and poorer self-rated health compared to healthy controls. They reported reduced ability to perform physical activity owing to migraine (high degree), tension-type headache (moderate degree) and neck pain (low degree). The most burdensome condition was migraine, followed by tension-type headache and neck pain. Conclusions: Migraine with co-existing tension-type headache and neck pain was highly prevalent in a clinic-based sample. Persons with migraine and co-existing tension-type headache and neck pain may require more individually tailored interventions to increase the level of physical activity, and to improve psychological well-being, perceived stress and self-rated health.
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| 109399. |
- Krøll, Lotte Skytte, et al.
(författare)
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Migraine co-existing tension-type headache and neck pain : Validation of questionnaires
- 2015
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Ingår i: Scandinavian Journal of Pain. - : Walter de Gruyter GmbH. - 1877-8860 .- 1877-8879. ; 8, s. 10-16
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Tidskriftsartikel (refereegranskat)abstract
- Background and aim: Migraine often includes co-existing tension-type headache (TTH) and neck pain (NP). Multiple headache questionnaires assessing headache impact have been described previously; however, none of the existing questionnaires have been designed to cover migraine with co-existing TTH and NP. Therefore a new questionnaire was developed to measure these co-morbidities. The aim was to determine face and content validity of the newly developed questionnaire, "Impact of Migraine, Tension-Type Headache and Neck Pain" (impact M-TTH-NP) and to determine face and content validity of the International Physical Activity Questionnaire (IPAQ short form), Migraine-Specific Quality of Life Questionnaire (MSQ v. 2.1), WHO-Five Well-Being Index (WHO-5), Major Depression Inventory (MDI) and Neck Disability Index (NDI) not yet validated in this target population. Material and methods: The new multi-dimensional questionnaire "Impact M-TTH-NP" cover pain, triggers, psychosocial, socioeconomic and work related aspects, based on a four-week recall period. The items are rated on an 11-point numeric rating scale with the end points 0 = no impact and 10 = most imaginable impact. Face validity was assessed by migraine patients with co-existing TTH and NP. They were recruited between September 2012 and March 2013 from a tertiary referral headache centre. Nine women with a mean age of 38 years participated in group interviews. The questionnaires were reviewed for relevance and meaningfulness. Content validity was assessed by 13 headache experts. They had worked with headache diseases for an average of 9 (range, 2-38) years. Experts were recruited between August 2012 and October 2012. Nine medical doctors, two physical therapists, one headache nurse and one psychologist (eight women and five men, mean age of 42 years) participated. The experts rated each item of the questionnaires using a four-point Likert scale with the end points 1 = not relevant and 4 = highly relevant. The quantitative measurement of content validity was calculated by the item-level content validity index (I-CVI) and the scale-level content validity average method (S-CVI/Ave). The average deviation (AD) index was used as a measure of interrater agreement. Results: Impact M-TTH-NP showed acceptable face validity. Of 78 items twelve were revised and one was added based on group interviews and expert review. Seventy-two items (92%) obtained I-CVI. ≥ 0.78 (range 0.78-1.00) indicating excellent content validity, 71 items (91%) obtained acceptable AD index. Nine items did not meet either the limit for excellent I-CVI and/or acceptable AD index. The overall S-CVI/Ave was 0.92 indicating an excellent content validity. In addition, four of the five additional questionnaires showed acceptable face validity (MSQ, WHO-5, MDI and NDI) and three showed excellent content validity (WHO-5, MDI and NDI) for patients suffering from migraine and co-existing TTH and NP. Conclusions and implications: The impact M-TTH-NP questionnaire showed acceptable face validity and excellent content validity and may be useful when evaluating treatment effect in this target group. The new impact M-TTH-NP questionnaire in combination with the additional questionnaires that together assess pain, triggers, psychosocial and socioeconomic aspects may provide a deeper understanding of the complexity of migraine with co-existing TTH and NP.
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| 109400. |
- Krøll, Lotte Skytte
(författare)
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The effects of aerobic exercise and the impact of migraine and co-existing tension-type headache and neck pain
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aims of this thesis were to investigate the effects of an aerobic exercise program and the impact of migraine and co-existing TTH and NP in persons with these combined conditions. This thesis is based on four studies.In study I, a new questionnaire, Impact of Migraine, TTH and NP (Impact M-TTH-NP), was developed. This questionnaire covered pain, triggers, psychosocial,socioeconomic and work related aspects. Face and content validity wereinvestigated together with five additional questionnaires; the International Physical Activity Questionnaire (IPAQ short form), Migraine-Specific Quality of LifeQuestionnaire (MSQ v. 2.1), The World Health Organization five-itemPsychological Well-Being Index (WHO-5), Major Depression Inventory (MDI) andNeck Disability Index (NDI). Face validity was assessed by group interviews ofnine persons with migraine and co-existing TTH and NP. Content validity wasassessed by the degree of relevance by 13 headache experts. Impact M-TTH-NPshowed acceptable face validity and excellent content validity. MSQ, WHO-5, MDIand NDI showed acceptable face validity, and WHO-5, MDI and NDI showed excellent content validity.In study II, the prevalence of co-existing TTH and NP in a clinical sample of persons with migraine was investigated. Also, we investigated level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing TTH and NP, their perceived ability to engage in physical activity and which among the three conditions (migraine, TTH or NP) was rated as the most burdensome condition. A survey of 148 persons with migraine and 100 healthy controls was conducted. The prevalence of co-existing TTH and NP in persons with migraine was 67%; this group had a low level of physical activity, low psychological well-being, high level of perceived stress and poor self-rated health compared to healthy controls. They reported reduced ability to engage in physical activity owing to migraine (high degree), TTH (moderate degree) and NP (low degree). The most burdensome condition was migraine, followed by TTH and NP.In studies III and IV, the effect of a 12-week aerobic exercise program, with follow-up six months from baseline, in persons with migraine and co-existing TTH and NP was investigated in a prospective, open-label, randomized, clinical trial. Fifty-two persons (26 in exercise group and 26 in control group) completed the six-month study period. The exercise group showed a significant improvement in the ability to engage in daily activities because of reduced impact of migraine compared to controls. Migraine frequency, pain intensity and duration were significantly reduced in the exercise group compared to baseline, although not significant compared to the control group (Study III). The effect of the aerobic exercise program on pain perception was measured in Study IV. We did not identify any significant effect on muscle tenderness and pain thresholds. We concluded that aerobic exercise had positive effects on migraine severity and migraine burden, but these results could not be explained by the applied tests of muscle tenderness and pain thresholds. Thus, the positive effect on migraine burden may rather be explained by positive alteration of avoidance behaviour.
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