Search

The fields of science indicated in the title represent centuries old research and development activities of the current department and its legal predecessor institutions, matching the standards, expectations and possibilities of the given era. It is of course impossible to summarize all this in a few pages. A tangential or more detailed description of some areas can be found in other chapters of this issue compiled to review the scientific activities of the department (e.g., in the articles of András Salgó and Ferenc Békés, Zsuzsanna Bugyi et al., Eszter Schallet al.) and in the summary article presenting the department’s food science activities. In our current paper, we attempt to provide a brief overview of research directions and results that, from the 1990s to the present day, have played a decisive role in the activities of the department, including the Cereal Science and Food Quality Research Group, as well as in the development and shaping of its research profile. The years following the regime change were decisive in the lives of all of us. The conditions for education and the cultivation of science changed continuously and significantly, mostly worsening in this transition period. Many people questioned whether it was worth continuing to cultivate the old, traditional areas, or whether we should be more open, modernize and look for new ways, taking advantage of the extremely slow but continuously opening opportunities for building domestic and, especially, international relations, and later for tenders and financing. Progress, development, and openness to new ideas should be essential qualities for an educator and researcher. However, the acquisition of knowledge, experience, and skills takes time, as does the creation and maintenance of the conditions necessary for the cultivation of old or new fields. In this uncertain operating matrix, in the mid-1990s we decided to move towards new areas (modernization of food analysis, automatic and rapid test methods, food safety), while trying to maintain and strengthen the cultivation of traditional fields (such as research related to cereal science and plant proteins, development of analytical methods and instruments) that had gained national and international recognition thanks to the work of our predecessors. In the following sections, a brief summary of grain qualification and related method and instrument developments enabling the examination of typically small amounts of material, research on the qualification of small and pseudocereals and improving their possibilities of use, as well as analytical and product development results for increasing food safety, partially related to the previous topic, is given.

A címben jelzett tudományterületek a jelenlegi tanszék és jogelőd intézményeinek évszázados, az adott kor színvonalához, elvárásaihoz, lehetőségeihez illeszkedő kutatás-fejlesztési tevékenységeket jelentenek. Ennek összefoglalása néhány oldal terjedelemben természetesen lehetetlen. Egyes területek érintőleges vagy részletesebb leírása a tanszék tudományos tevékenységének áttekintésére összeállított jelen lapszám más fejezeteiben (pl. Salgó András és Békés Ferenc, Bugyi Zsuzsanna és mtsai., Schall Eszter és mtsai. cikkeiben) illetve a tanszék élelmiszertudományi tevékenységét bemutató összegző cikkben megtalálható. Jelenlegi írásunkban olyan kutatási irányok és eredmények rövid áttekintésére teszünk kísérletet, melyek az 1990-es évektől napjainkig meghatározó szerepet játszanak a tanszék és ezen belül a Gabonatudományi és Élelmiszerminőség kutatócsoport tevékenységében, illetve kutatási profiljának alakulásában, alakításában. A rendszerváltást követő évek mindannyiunk életében meghatározóak voltak. Az oktatás és a tudomány művelésének feltételei folyamatosan és jelentősen változtak, az átmeneti időszakban inkább romlottak. Sokakban megfogalmazódott a kérdés, hogy lehet-e, érdemes-e a régi, hagyományos területek művelését folytatni, vagy élve a rendkívül lassan, de folyamatosan kinyíló hazai és főleg nemzetközi kapcsolatépítési, majd később pályázati, finanszírozási lehetőségekkel, nyissunk, modernizáljunk, keressünk új utakat. A fejlődés, a fejlesztés, az új iránti nyitottság alap kell, hogy legyen egy oktató-kutató számára. Azonban a tudás, a tapasztalat, a jártasság megszerzése időigényes ugyanúgy, mint régi vagy új területek műveléséhez szükséges feltételrendszer megteremtése és fenntartása. Ebben a bizonytalannak nevezhető működési mátrixban döntöttünk úgy a 90-es évek közepén, hogy úgy indulunk el az új területek (élelmiszeranalitika modernizálása, automatikus és gyorsvizsgálati módszerek, élelmiszerbiztonság) felé, hogy közben igyekszünk megtartani és erősíteni az elődeink munkájának köszönhetően hazai és nemzetközi elismertséget kivívó hagyományos területek (mint pl. a gabonatudományi és növényi fehérjékkel kapcsolatos kutatások, analitikai módszer és műszerfejlesztések) művelését is. Az alábbiakban a gabonaminősítés és az azokhoz kapcsolódó, jellemzően kis anyagmennyiségek vizsgálatát lehetővé tévő módszer- és műszerfejlesztésekről, a kis- és álgabonák minősítésével és felhasználási lehetőségeinek javításával kapcsolatos kutatásokról, valamint -részben az előző témához is kapcsolódva- az élelmiszerbiztonság növelését szolgáló analitikai és termékfejlesztési eredményekről adunk rövid összegzést.

Abstract: We present herewith cases of non-infectious uveitis with biological treatment where the ocular complaints were the initial symptoms indicating a multi-organ autoimmune disease. The first case was a patient with panuveitis and Vogt–Koyanagi–Harada disease, the second case was also a panuveitic patient with sarcoidosis and the third case was a patient with intermediate uveitis and inflammatory bowel disease. In all cases, emerging new, biological therapy (adalimumab) was necessary to achieve permanent inactive period of uveitis and the autoimmune disease. Introducing systemic biological treatment (adalimumab) in ophthalmology is crucial in the therapy of immune-mediated, non-infectious uveitis in order to preserve visual acuity. Orv Hetil. 2019; 160(44): 1744–1750.

The aim of this research was to investigate the possibility of the instrumentation of baking tests on different scales and compare the results with a conventional, internationally standardized test baking method, using the flours of ten Hungarian winter wheat varieties. Baking quality of the wheat flours was tested on micro- and macro-scale using a semi-automatic test baking methodology developed by our department and Labintern Ltd. Standard straight-dough baking test was performed according to ICC Nr. 131 Standard Method. Characterization of baking performance included the determination of baking loss and specific volume, as well as digital image analysis and texture profile analysis of the bread crumb. The presented semi-automatic test baking method qualifies as one of the first instrumental laboratory bread baking methodologies, which enables the implementation of baking tests both on macro (250 g flour/loaf)- and micro-scale (10 g flour/loaf). The results of macro and micro baking tests obtained by the instrument were comparable with the standard method mainly in crumb properties such as crumb hardness. The methods basically differed in specific volume and crust color, which may indicate some fundamental differences between these methodologies.

Although efficacy of ustekinumab (UST) has been demonstrated through randomized trials, data from real-life prospective cohorts are still limited. Our aim was to evaluate clinical efficacy, drug sustainability, dose intensification and results from therapeutic drug monitoring in UST treated patients with Crohn's disease (CD) using a prospective, nationwide, multicenter cohort.Patients from 10 Inflammatory Bowel Disease centers were enrolled between 2019 January and 2020 May. Patient demographics, disease phenotype, treatment history, clinical disease activity (Crohn's Disease Activity Index(CDAI), Harvey Bradshaw Index(HBI)), biomarkers, and serum drug levels were obtained. Evaluations were performed at week8 (post-induction), w16-20, w32-36, and w52-56 follow-up visits.A total of 142 patients were included [57.4% female; complex disease behavior (B2/B3):48%, previous anti-TNF exposition:97%]. Clinical response and remission rates after induction(w8) were 78.1% and 57.7% using CDAI, and 82.5% and 51.8% based on HBI scores. The one-year clinical remission rate was 58%/57.3%(CDAI/HBI). Composite clinical and biomarker remission (CDAI150 and C-reactive protein10 mg/L) rates were 35.4%; 33.3%; 38.6% and 36.6% at w8/w16-20/w32-36 and w52-56. Drug sustainability was 81.9%(standard deviation(SD): 3.4) at 1 year(1y). Probability of dose intensification was high and introduced early, 42.2%(SD:4.2) at ~w32 and 51.9%(SD:4.4%) at 1y.Ustekinumab showed favorable drug sustainability and clinical efficacy in a patient population with severe disease phenotype and previous anti-tumor necrosis factor (anti-TNF) failure, however frequent dose intensification was required.

The aim of this study was to investigate the mixing behaviour and the baking performance of millet and buckwheat white and wholemeal flours in real dough systems. Furthermore arabinoxylan addition (1% and 3% (m/m)) and oxidative enzyme treatment (0.89U/g flour) were applied. All measuments were carried out on small-scale (4 g flour/dough and 15 g flour/bread) further examining the applicability of size reduced baking tests in the analyis of gluten-free end-products. Arabinoxylan addition reduced, but enzyme treatment increased the maximum consistency of the doughs. The development time and degree of softening were highly increased by AX. The specific volume was increased and the crumb hardness was decreased by adding arabinoxylan, however the enzyme had various effects in both dough systems. The observed phenomena highly depended on the right proportion of treatments and the complexity and the chemical composition of the flours: in the white flour systems, changes were more obvious than in the wholemeal flour systems. Sourdough could improve the final product quality in itself and could mask the effects of the additives. It can be concluded that the small-scale tests can be capable of describing the diverseness of the rheological behaviour and the baking performance in both straigh dough and sourdough systems.

When an artificial surface (e.g. an asphalt road) reflects strongly and horizontally polarized light as water bodies do in the nature, polarotactic aquatic insects, like the creek-dwelling Ephemera danica mayflies easily become deceived. After swarming above the creek surface, E. danica females begin their upstream compensatory flight and can be deflected at bridges with an asphalt road and continue their flight above the road surface. Thus, the water-mimicking optical signal of the road may deceive water-seeking polarotactic mayflies and lead them to distant, polarized-light-polluting surfaces, which elicit anomalous oviposition. On an asphalt road crossing a creek, we deployed polarizing insect traps at different distances from the bridge. The traps captured E. danica mayflies and their catch numbers indicated that these mayflies originated from the direction of the bridge, proving that they followed the track of the road. Our results suggest that distant polarized-light-polluting objects along an asphalt road can trap mayflies emerging from a creek crossing the road. The combination of an asphalt road and a man-made in situ (local) polarizing surface forms a complex ecological trap, being capable of luring aquatic insects from greater distances. To eliminate the oviposition of dangered polarotactic aquatic insects emerging from a creek onto the asphalt road crossing the creek, we suggest to deploy strongly and horizontally polarizing water-filled black trays along the edge of the road during the swarming period. Thus, the eggs of the deceived insects can be moved back to the creek in order to assist the conservation of the offspring-generation.

We present herewith cases of non-infectious uveitis with biological treatment where the ocular complaints were the initial symptoms indicating a multi-organ autoimmune disease. The first case was a patient with panuveitis and Vogt-Koyanagi-Harada disease, the second case was also a panuveitic patient with sarcoidosis and the third case was a patient with intermediate uveitis and inflammatory bowel disease. In all cases, emerging new, biological therapy (adalimumab) was necessary to achieve permanent inactive period of uveitis and the autoimmune disease. Introducing systemic biological treatment (adalimumab) in ophthalmology is crucial in the therapy of immune-mediated, non-infectious uveitis in order to preserve visual acuity. Orv Hetil. 2019; 160(44): 1744-1750.Absztrakt: Közleményünkben a nem fertőzéses eredetű uveitises, szisztémás biológiai terápiában részesülő betegeink kórtörténetét ismertetjük, ahol a szemészeti panaszok első/vezető tünetként jelentkeztek és hívták fel a figyelmet a háttérben rejlő autoimmun, több szervet érintő betegségre. Első esetünkben a panuveitis hátterében Vogt–Koyanagi–Harada-betegség, második esetünkben a panuveitis hátterében sarcoidosis, míg harmadik esetünkben az intermedier uveitis hátterében gyulladásos bélbetegség állt. A betegek a szemészetben újonnan bevezetett biológiai terápiában (adalimumab) részesültek, amely nemcsak az intraocularis gyulladás megszűnését, hanem a háttérbetegség aktivitásmentességét is eredményezte. A szemészetben új, szisztémás biológiai terápia, az adalimumab alkalmazása a háttérben álló autoimmun betegségek kezelése mellett a látóélesség megőrzése szempontjából is döntő jelentőségű. Orv Hetil. 2019; 160(44): 1744–1750.

Photovoltaic solar panels represent one of the most promising renewable energy sources, but are strong reflectors of horizontally polarized light. Polarized light pollution (PLP) associated with solar panels causes aquatic insects to prefer to oviposit on panels over natural water bodies, with potential to negatively impact their global populations as solar energy expands. We evaluate the hypothesis that anti-reflective coatings (ARCs) used to increase the energy efficiency of solar panels will reduce the amount of PLP they reflect, and their attractiveness to aquatic insects. We created artificial test surfaces that mimicked the optical properties of coated and uncoated solar panels and exposed them to wild populations of polarotactic mayflies (Ephemeroptera), horseflies (Tabanidae) and non-biting midges (Chironomidae) used as indicators of PLP. We evaluated the reflection-polarization properties of test surfaces from four different angles of view and under sunny and overcast skies in the visible and ultraviolet parts of the spectrum. Matte (i.e. ARC-coated) sunlit solar panels were strong sources of horizontally polarized light only when the sun was afront and behind, in contrast to uncoated panels which exceeded common polarization-sensitivity thresholds for aquatic insects from all four viewing directions. As predicted by these polarization patterns, horsefly numbers and water-seeking behaviors were significantly reduced by ARCs. Under overcast skies, both matte and shiny (i.e. uncoated) panels were insect-detectible sources of PLP. Matteness modestly reduced the degree of polarization of reflected light, but not sufficiently such that fewer chironomids were attracted to them. Mayflies actually preferred matte panels under overcast skies. ARCs are most likely to reduce PLP and benefit aquatic insects under sunny skies and when used in conjunction with white non-polarizing gridding, but may actually exacerbate the severity of their negative effects under overcast conditions. Consequently, even current ARC technology has a role to play in aquatic insect conservation, but strategic deployment of solar panels away from water bodies and temperate regions may trump these benefits.

Inspired by the pioneer work of the nineteenth century photographer, William Nicholson Jennings, we studied quantitatively how realistic painted lightnings are. In order to answer this question, we examined 100 paintings and 400 photographs of lightnings. We used our software package to process and evaluate the morphology of lightnings. Three morphological parameters of the main lightning branch were analysed: (i) number of branchesNb, (ii) relative lengthr, and (iii) number of local maxima (peaks)Npof the turning angle distribution. We concluded: (i) Painted lightnings differ from real ones inNbandNp. (ii) Ther-values of painted and real lightnings vary in the same range. (iii) 67 and 22% of the studied painted and real lightnings were non-bifurcating (Nb = 1, meaning only the main branch), the maximum ofNbof painted and real lightnings is 11 and 51, respectively, and painted bifurcating lightnings possess mostly 2–4 branches, while real lightnings have mostly 2–10 branches. To understand these findings, we performed two psychophysical experiments with 10 test persons, whose task was to guessNbon photographs of real lightnings which were flashed for short time periods Δt = 0.5, 0.75 and 1 s (characteristic to lightnings) on a monitor. We obtained that (i) test persons can estimate the number of lightning branches quite correctly ifNb ≤ 11. (ii) IfNb > 11, its value is strongly underestimated with exponentially increasing difference between the real and estimated numbers. (iii) The estimation is independent of the flashing period Δtof lightning photos/pictures. (iv) The estimation is more accurate, if skeletonized lightning pictures are flashed, rather than real lightning photos. These findings explain why artists usually illustrate lightnings with branches not larger than 11.

If a human looks at the clear blue sky from which light with high enough degree of polarization d originates, an 8-shaped bowtie-like figure, the yellow Haidinger's brush can be perceived, the long axis of which points towards the sun. A band of high d arcs across the sky at 90° from the sun. A person can pick two points on that band, observe the yellow brushes and triangulate the position of the sun based on the orientation of the two observed brushes. This method has been suggested to have been used on the open sea by Viking navigators to determine the position of the invisible sun occluded by cloud or fog. Furthermore, Haidinger's brushes can also be used to locate the sun when it is below the horizon or occluded by objects on the horizon. To determine the position of the sun using the celestial polarization pattern, the d of the portion of the sky used must be greater than the viewer's degree of polarization threshold d * for perception of Haidinger's brushes. We studied under which sky conditions the prerequisite d > d * is satisfied. Using full-sky imaging polarimetry, we measured the d -pattern of skylight in the blue (450 nm) spectral range for 1296 different meteorological conditions with different solar elevation angles θ and per cent cloud cover ρ . From the measured d -patterns of a given sky we determined the proportion P of the sky for which d > d *. We obtained that P is the largest at low solar elevations θ ≈ 0° and under totally or nearly clear skies with cloud coverage ρ = 0%, when the sun's position is already easily determined. If the sun is below the horizon (−5° ≤ θ P = 76.17 ± 4.18% for d min ∗ = 23 % under clear sky conditions. Consequently, the sky-polarimetric Viking navigation based on Haidinger's brushes is most useful after sunset and prior to sunrise, when the sun is not visible and large sky regions are bright, clear and polarized enough for perception of Haidinger's brushes.

Cue-conflict experiments were performed to study the compass calibration of one predominantly diurnal migrant, the dunnock (Prunella modularis), and two species of nocturnal passerine migrants, the sedge warbler (Acrocephalus schoenobaenus), and the European robin (Erithacus rubecula) during autumn migration in South Sweden. The birds' orientation was recorded in circular cages under natural clear and simulated overcast skies in the local geomagnetic field, and thereafter the birds were exposed to a cue-conflict situation where the horizontal component of the magnetic field (mN) was shifted +90° or −90° at two occasions, one session starting shortly after sunrise and the other ca. 90 min before sunset and lasting for 60 min. The patterns of the degree and angle of skylight polarization were measured by full-sky imaging polarimetry during the cue-conflict exposures and orientation tests. All species showed orientation both under clear and overcast skies that correlated with the expected migratory orientation towards southwest to south. For the European robin the orientation under clear skies was significantly different from that recorded under overcast skies, showing a tendency that the orientation under clear skies was influenced by the position of the Sun at sunset resulting in more westerly orientation. This sun attraction was not observed for the sedge warbler and the dunnock, both orientating south. All species showed similar orientation after the cue-conflict as compared to the preferred orientation recorded before the cue-conflict, with the clearest results in the European robin and thus, the results did not support recalibration of the celestial nor the magnetic compasses as a result of the cue-conflict exposure.

Like other aquatic insects, mayflies are positively polarotactic and locate water surfaces by means of the horizontal polarization of water-reflected light. However, may vertically polarized light also have implications for the swarming behaviour of mayflies? To answer this question, we studied in four field experiments the behavioural responses of Ephoron virgo and Caenis robusta mayflies to lamps emitting horizontally and vertically polarized and unpolarized light. In both species, unpolarized light induces positive phototaxis, horizontally polarized light elicits positive photo- and polarotaxis, horizontally polarized light is much more attractive than unpolarized light, and vertically polarized light is the least attractive if the stimulus intensities and spectra are the same. Vertically polarized light was the most attractive for C. robusta if its intensity was about two and five times higher than that of the unpolarized and horizontally polarized stimuli, respectively. We suggest that the mayfly behaviour observed in our experiments may facilitate the stability of swarming above water surfaces. Beside the open water surface reflecting horizontally polarized light, the shadow and mirror image of riparian vegetation at the edge of the water surface reflect weakly and non-horizontally (mainly vertically) polarized light. Due to their positive polarotaxis, flying mayflies remain continuously above the water surface, because they keep away from the unpolarized or non-horizontally polarizing edge regions (water surface and coast line) of water bodies. We also discuss how our findings can explain the regulation of mayfly colonization.

The 6-ommatidium ventral eye of the water-surface-inhabiting springtail Poduara aquatica has horizontal and vertical microvilli and perceives light from the ventral, frontal and frontodorsal regions, while the 2-ommatidium dorsal eye possesses two upward-looking ommatidia with vertical microvilli. The ventral eye may serve water detection by its polarization sensitivity, even if the insect is resting with its head slightly tipped down on a raised surface. The polarization sensitivity and polarotaxis in springtails (Collembola) have not been investigated. Therefore, we performed behavioural choice experiments to study them in P. aquatica. We found that the strength of phototaxis in P. aquatica depends on the polarization characteristics of stimulating light. Horizontally and vertically polarized light were the most and least attractive, respectively, while unpolarized stimulus elicited moderate attraction. We showed that horizontally polarized light attracted more springtails than unpolarized, even if the polarized stimulus was 10 times dimmer. Thus, besides phototaxis, P. aquatica also has polarotaxis with the ability to measure or at least estimate the degree of polarization. Our results indicate that the threshold d* of polarization sensitivity in P. aquatica is between 10.1 and 25.5 %.

Ecological photopollution created by artificial night lighting can alter animal behavior and lead to population declines and biodiversity loss. Polarized light pollution is a second type of photopollution that triggers water-seeking insects to ovisposit on smooth and dark man-made objects, because they simulate the polarization signatures of natural water bodies. We document a case study of the interaction of these two forms of photopollution by conducting observations and experiments near a lamp-lit bridge over the river Danube that attracts mass swarms of the mayfly Ephoron virgo away from the river to oviposit on the asphalt road of the bridge. Millions of mayflies swarmed near bridge-lights for two weeks. We found these swarms to be composed of 99% adult females performing their upstream compensatory flight and were attracted upward toward unpolarized bridge-lamp light, and away from the horizontally polarized light trail of the river. Imaging polarimetry confirmed that the asphalt surface of the bridge was strongly and horizontally polarized, providing a supernormal ovipositional cue to Ephoron virgo, while other parts of the bridge were poor polarizers of lamplight. Collectively, we confirm that Ephoron virgo is independently attracted to both unpolarized and polarized light sources, that both types of photopollution are being produced at the bridge, and that spatial patterns of swarming and oviposition are consistent with evolved behaviors being triggered maladaptively by these two types of light pollution. We suggest solutions to bridge and lighting design that should prevent or mitigate the impacts of such scenarios in the future. The detrimental impacts of such scenarios may extend beyond Ephoron virgo.

According to Thorkild Ramskou's theory proposed in 1967, under overcast and foggy skies, Viking seafarers might have used skylight polarization analysed with special crystals called sunstones to determine the position of the invisible Sun. After finding the occluded Sun with sunstones, its elevation angle had to be measured and its shadow had to be projected onto the horizontal surface of a sun compass. According to Ramskou's theory, these sunstones might have been birefringent calcite or dichroic cordierite or tourmaline crystals working as polarizers. It has frequently been claimed that this method might have been suitable for navigation even in cloudy weather. This hypothesis has been accepted and frequently cited for decades without any experimental support. In this work, we determined the accuracy of this hypothetical sky-polarimetric Viking navigation for 1080 different sky situations characterized by solar elevationθand cloudinessρ, the sky polarization patterns of which were measured by full-sky imaging polarimetry. We used the earlier measured uncertainty functions of the navigation steps 1, 2 and 3 for calcite, cordierite and tourmaline sunstone crystals, respectively, and the newly measured uncertainty function of step 4 presented here. As a result, we revealed the meteorological conditions under which Vikings could have used this hypothetical navigation method. We determined the solar elevations at which the navigation uncertainties are minimal at summer solstice and spring equinox for all three sunstone types. On average, calcite sunstone ensures a more accurate sky-polarimetric navigation than tourmaline and cordierite. However, in some special cases (generally at 35° ≤ θ ≤ 40°, 1 okta ≤ ρ ≤ 6 oktas for summer solstice, and at 20° ≤ θ ≤ 25°, 0 okta ≤ ρ ≤ 4 oktas for spring equinox), the use of tourmaline and cordierite results in smaller navigation uncertainties than that of calcite. Generally, under clear or less cloudy skies, the sky-polarimetric navigation is more accurate, but at low solar elevations its accuracy remains relatively large even at high cloudiness. For a givenρ, the absolute value of averaged peak North uncertainties dramatically decreases with increasingθuntil the sign (±) change of these uncertainties. For a givenθ, this absolute value can either decrease or increase with increasingρ. The most advantageous sky situations for this navigation method are at summer solstice when the solar elevation and cloudiness are 35° ≤ θ ≤ 40° and 2 oktas ≤ ρ ≤ 3 oktas.

It is a widely discussed hypothesis that Viking seafarers might have been able to locate the position of the occluded sun by means of dichroic or birefringent crystals, the mysterious sunstones, with which they could analyze skylight polarization. Although the atmospheric optical prerequisites and certain aspects of the efficiency of this sky-polarimetric Viking navigation have been investigated, the accuracy of the main steps of this method has not been quantitatively examined. To fill in this gap, we present here the results of a planetarium experiment in which we measured the azimuth and elevation errors of localization of the invisible sun. In the planetarium sun localization was performed in two selected celestial points on the basis of the alignments of two small sections of two celestial great circles passing through the sun. In the second step of sky-polarimetric Viking navigation the navigator needed to determine the intersection of two such celestial circles. We found that the position of the sun (solar elevation θ(S), solar azimuth φ(S)) was estimated with an average error of +0.6°≤Δθ≤+8.8° and -3.9°≤Δφ≤+2.0°. We also calculated the compass direction error when the estimated sun position is used for orienting with a Viking sun-compass. The northern direction (ω(North)) was determined with an error of -3.34°≤Δω(North)≤+6.29°. The inaccuracy of the second step of this navigation method was high (Δω(North)=-16.3°) when the solar elevation was 5°≤θ(S)≤25°, and the two selected celestial points were far from the sun (at angular distances 95°≤γ(1), γ(2)≤115°) and each other (125°≤δ≤145°). Considering only this second step, the sky-polarimetric navigation could be more accurate in the mid-summer period (June and July), when in the daytime the sun is high above the horizon for long periods. In the spring (and autumn) equinoctial period, alternative methods (using a twilight board, for example) might be more appropriate. Since Viking navigators surely also committed further errors in the first and third steps, the orientation errors presented here underestimate the net error of the whole sky-polarimetric navigation.

It is a widely discussed and regularly cited theory that Viking navigators might have been able to locate the position of the sun occluded by clouds or below the horizon with a mysterious birefringent or dichroic crystal, the sunstone, on the basis of the pattern of skylight polarisation. In this chapter we describe the steps and the experimentally tested efficiency of this sky-polarimetric navigation method, and we show modern navigation instruments that operate in a similar principle. We investigate the atmospheric optical prerequisites of sky-polarimetric Viking navigation, looking for the ideal weather conditions, under which sunstones could be used for this navigational task. We also discuss other hypothesised Viking navigation instruments, like the horizon board and the sun compass or twilight board. Finally, we consider the Medieval Norse sailing routes and some alternative atmospheric optical navigation cues, which also could help during the long-time marine voyage of Viking seafarers.

The theory of sky-polarimetric Viking navigation has been widely accepted for decades without any information about the accuracy of this method. Previously, we have measured the accuracy of the first and second steps of this navigation method in psychophysical laboratory and planetarium experiments. Now, we have tested the accuracy of the third step in a planetarium experiment, assuming that the first and second steps are errorless. Using the fists of their outstretched arms, 10 test persons had to estimate the elevation angles (measured in numbers of fists and fingers) of black dots (representing the position of the occluded Sun) projected onto the planetarium dome. The test persons performed 2400 elevation estimations, 48% of which were more accurate than ±1°. We selected three test persons with the (i) largest and (ii) smallest elevation errors and (iii) highest standard deviation of the elevation error. From the errors of these three persons, we calculated their error function, from which the North errors (the angles with which they deviated from the geographical North) were determined for summer solstice and spring equinox, two specific dates of the Viking sailing period. The range of possible North errors Δ ω N was the lowest and highest at low and high solar elevations, respectively. At high elevations, the maximal Δ ω N was 35.6° and 73.7° at summer solstice and 23.8° and 43.9° at spring equinox for the best and worst test person (navigator), respectively. Thus, the best navigator was twice as good as the worst one. At solstice and equinox, high elevations occur the most frequently during the day, thus high North errors could occur more frequently than expected before. According to our findings, the ideal periods for sky-polarimetric Viking navigation are immediately after sunrise and before sunset, because the North errors are the lowest at low solar elevations.

According to an old but still unproven theory, Viking navigators analysed the skylight polarization with dichroic cordierite or tourmaline, or birefringent calcite sunstones in cloudy/foggy weather. Combining these sunstones with their sun-dial, they could determine the position of the occluded sun, from which the geographical northern direction could be guessed. In psychophysical laboratory experiments, we studied the accuracy of the first step of this sky-polarimetric Viking navigation. We measured the adjustment erroreof rotatable cordierite, tourmaline and calcite crystals when the task was to determine the direction of polarization of white light as a function of the degree of linear polarizationp. From the obtained error functionse(p), the thresholdsp* above which the first step can still function (i.e. when the intensity change seen through the rotating analyser can be sensed) were derived. Cordierite is about twice as reliable as tourmaline. Calcite sunstones have smaller adjustment errors if the navigator looks for that orientation of the crystal where the intensity difference between the two spots seen in the crystal is maximal, rather than minimal. For higherp(greater thanpcrit) of incident light, the adjustment errors of calcite are larger than those of the dichroic cordierite (pcrit=20%) and tourmaline (pcrit=45%), while for lowerp(less thanpcrit) calcite usually has lower adjustment errors than dichroic sunstones. We showed that real calcite crystals are not as ideal sunstones as it was believed earlier, because they usually contain scratches, impurities and crystal defects which increase considerably their adjustment errors. Thus, cordierite and tourmaline can also be at least as good sunstones as calcite. Using the psychophysicale(p) functions and the patterns of the degree of skylight polarization measured by full-sky imaging polarimetry, we computed how accurately the northern direction can be determined with the use of the Viking sun-dial under 10 different sky conditions at 61° latitude, which was one of the main Viking sailing routes. According to our expermiments, under clear skies, using calcite or cordierite or tourmaline sunstones, Viking sailors could navigate with net orientation errors|Σmax|≤3∘. Under overcast conditions, their net navigation error depends on the sunstone type:|Σmax(calcite)|≤6∘,|Σmax(cordierite)|≤10∘and|Σmax(tourmaline)|≤17∘.

The knowledge on the optics of fogbows is scarce, and their polarization characteristics have never been measured to our knowledge. To fill this gap we measured the polarization features of 16 fogbows during the Beringia 2005 Arctic polar research expedition by imaging polarimetry in the red, green and blue spectral ranges. We present here the first polarization patterns of the fogbow. In the patterns of the degree of linear polarization p, fogbows and their supernumerary bows are best visible in the red spectral range due to the least dilution of fogbow light by light scattered in air. In the patterns of the angle of polarization α fogbows are practically not discernible because their α-pattern is the same as that of the sky: the direction of polarization is perpendicular to the plane of scattering and is parallel to the arc of the bow, independently of the wavelength. Fogbows and their supernumeraries were best seen in the patterns of the polarized radiance. In these patterns the angular distance δ between the peaks of the primary and the first supernumerary and the angular width σ of the primary bow were determined along different radii from the center of the bow. δ ranged between 6.08° and 13.41° , while σ changed from 5.25° to 19.47° . Certain fogbows were relatively homogeneous, meaning small variations of δ and σ along their bows. Other fogbows were heterogeneous, possessing quite variable δ- and σ-values along their bows. This variability could be a consequence of the characteristics of the high Arctic with open waters within the ice shield resulting in the spatiotemporal change of the droplet size within the fog

The horizontally polarizing surface parts of shiny black cars (the reflection-polarization characteristics of which are similar to those of water surfaces) attract water-leaving polarotactic insects. Thus, shiny black cars are typical sources of polarized light pollution endangering water-leaving insects. A new fashion fad is to make car-bodies matt black or grey. Since rough (matt) surfaces depolarize the reflected light, one of the ways of reducing polarized light pollution is to make matt the concerned surface. Consequently, matt black/grey cars may not induce polarized light pollution, which would be an advantageous feature for environmental protection. To test this idea, we performed field experiments with horizontal shiny and matt black car-body surfaces laid on the ground. Using imaging polarimetry, in multiple-choice field experiments we investigated the attractiveness of these test surfaces to various water-leaving polarotactic insects and obtained the following results: (i) The attractiveness of black car-bodies to polarotactic insects depends in complex manner on the surface roughness (shiny, matt) and species (mayflies, dolichopodids, tabanids). (ii) Non-expectedly, the matt dark grey car finish is much more attractive to mayflies (being endangered and protected in many countries) than matt black finish. (iii) The polarized light pollution of shiny black cars usually cannot be reduced with the use of matt painting. On the basis of these, our two novel findings are that (a) matt car-paints are highly polarization reflecting, and (b) these matt paints are not suitable to repel polarotactic insects. Hence, the recent technology used to make matt the car-bodies cannot eliminate or even can enhance the attractiveness of black/grey cars to water-leaving insects. Thus, changing shiny black car painting to matt one is a disadvantageous fashion fad concerning the reduction of polarized light pollution of black vehicles.

Vikings routinely crossed the North Atlantic without a magnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latitudes using primitive Sun compasses. Such instruments were tested on sea and proved to be efficient hand-held navigation tools, but the dimensions and incisions of the Uunartoq find are far from optimal in this role. On the basis of the sagas mentioning sunstones, incompatible hypotheses were formed for Viking solar navigation procedures and primitive skylight polarimetry with dichroic or birefringent crystals. We describe here a previously unconceived method of navigation based on the Uunartoq artefact functioning as a ‘twilight board’, which is a combination of a horizon board and a Sun compass optimized for use when the Sun is close to the horizon. We deduced an appropriate solar navigation procedure using a twilight board, a shadow-stick and birefringent crystals, which bring together earlier suggested methods in harmony and provide a true skylight compass function. This could have allowed Vikings to navigate around the clock, to use the artefact dial as a Sun compass during long parts of the day and to use skylight polarization patterns in the twilight period. In field tests, we found that true north could be appointed with such a medieval skylight compass with an error of about ±4° when the artificially occluded Sun had elevation angles between +10° and −8° relative to the horizon. Our interpretation allows us to assign exact dates to the gnomonic lines on the artefact and outlines the schedule of the merchant ships that sustained the Viking colony in Greenland a millennium ago.