Suvokiamo atkarpos ilgio priklausomybė nuo jos atvaizdo vietos akies tinklainėje

It is known that objects located in the centre of the visual field are perceived as larger than the objects located in the periphery (Пиаже, 1978). The image of an object differs from its perception object. The perceived size of an object depends on the size of its image in the visual cortex. This stems from the so-called cortical magnification factor. It is assumed that the same quantity of receptors sends information to the same area of the cortex. But photoreceptors are different – rods and the cones. It is not clear whether the different types of receptors make a different influence on the above-mentioned distortion of mapping. Also, the image of the object on the retina is perceived differently, depending on its location on the retina. Our goal was to explore how this subjective expansion changes while moving away from the centre of the retina, because there are no data on this, phenomenon. Method. Thirty normal or corrected to normal vision adults participated in the study. Five different length lines (5, 7, 10, 13, 15 degrees) were represented on the computer’s monitor one line at a time. Participants had monoculary bisected lines into two subjectively equal parts fixating sight on a cross located at the given end of the line.Results. The ratio ρ (length of the line near the cross / length of the other part) was calculated. This ratio as a function of the length of the whole line was not monotonic: when the line was short, ρ decreased, but then it began to increase. Three groups of results were formed considering the ratio of the line length (where the function had the extremum point). The largest group (66.67%) had the extremum point when the line length was 7 deg. The second group (23.33%) had the extremum point when the line length was 13 deg. The last group (10%) had not clear extremum point and was excluded from the calculation. Changes of the ρ value cannot be explained by the perceptual instability of the length of the line (Brown, 1953). There could be a correlation between the value of ρ and the density of all receptors in the retina where the line was projected.Conclusions. Humans make a bias while monocular by bisecting a line: the part near the point of fixation is perceived as bigger than the other part. The function of the line size ratio changes not monotonically – it has an extremum point. Most often, the extremum point is observed when the line size is 7 deg. This point is near the point where the density of rods exceeds that of cones. Other subjects show the extremum point when the line size is 13 deg., but the reasons for such a point shift remain unclear. Some subjects have no extremum point.Tyrimo tikslas yra patikrinti, kaip keičiasi objekto dydžio suvokimas, kintant jo projekcijos padėčiai akies tinklainėje, ir kaip objekto dydžio suvokimas priklauso nuo akies tinklainės receptorių (kūgelių ir lazdelių) tankio. Tiriamieji, žiūrėdami viena akimi ir fiksuodami žvilgsnį, dalijo skirtingų ilgių atkarpas – nustatydavo suvokiamą vidurį. Atkarpos dalių santykio nuo atkarpos ilgio funkcija turėjo lūžio tašką (66,7 proc. tiriamiesiems, kai atkarpos ilgis 7 laipsniai, 23,33 proc. – 13 laipsnių, kiti neturėjo). Rezultatai aiškinami skirtingu kūgelių ir lazdelių tankiu akies tinklainėje ir skirtinga kūgelių ir lazdelių įtaka

Spalvų suvokimo konstantiškumas: empirinis tyrimas ir matematinis modelis

The method to estimate the color constancy is suggested. The experimental results confirm the hypothesis of color constancy linear model. The linear operator calculated from the chromaticity coordinates of three chips under two different illuminations. The analysis of this linear operator is performed to clear up the physiological mechanism.Straipsnyje pasiūlytas būdas, kaip įvertinti spalvų suvokimo konstantiškumas. Eksperimento rezultatai patvirtino, kad spalvų suvokimo konstantiškumas yra linijinis modelis. Linijinis operatorius buvo apskaičiuotas iš chromatinių koordinačių, gautų iš trijų daviklių dviem apšvietimo sąlygomis. Operatoriaus analizė atlikta, siekiant išaiškinti psichologinį mechanizmą

Trend in eating habits among Lithuanian school-aged children in context of social inequality: three cross-sectional surveys 2002, 2006 and 2010

<p>Abstract</p> <p>Background</p> <p>Intermittent monitoring of food intake at the population level is essential for the planning and evaluation of national dietary intervention programs. Social-economic changes in Lithuania have likely affected dietary habits, but only a limited number of temporal studies on food intake trends among young population groups have been published. The aim of this study was to investigate changes in eating habits among Lithuanian school-aged children from 2002 to 2010, and to explore the association of these changes with the respondents' reported socio-economic status (SES).</p> <p>Methods</p> <p>We used Lithuanian data from the cross-national Health Behaviour in School-aged Children (HBSC) study collected in 2002, 2006 and 2010. Analyses were conducted on comparable questionnaire-based data from children aged 11, 13 and 15 (total n = 17,189) from a random sample of schools. A food frequency questionnaire was used to investigate frequencies of food consumption. Logistic regression was used to examine the affects of changing social variables on reported diet trends.</p> <p>Results</p> <p>In Lithuania, school-aged children have low intakes of fruits and vegetables. Only 21.1% of boys and 27.1% of girls reported daily fruit consumption. Similarly, 24.9% of boys and 29.6% of girls disclosed vegetable intake at least once daily. Comparing 2010 to 2002, the proportion of girls who consumed fruits daily increased from 24.2% to 31.0% (p < 0.001) but the proportion of boys who consumed vegetables daily decreased from 29.3% to 23.1% (p < 0.001). In 2006, for both sexes, there were observed increases in regular (at least five days a week) intake of sweets and chocolates, biscuits and pastries, and soft drinks; however, in the next survey (2010) these figures decreased. In addition, between 2006 and 2010, a substantial decrease in regular consumption of chips and fast food was also detected. Fruit and vegetable consumption as well as intake of sweets and chocolates, biscuits and pastries and soft drinks increased with family social-economic status and family material wealth. Trends in consumption of fruits, and other foods, and their association with changing social variables were demonstrated using the ORs estimated by three logistic models, using 2002 as the reference point. Changes in social variables from 2002 to 2010 affected the likelihood of daily consumption of fruits among boys by 22.5% (the corresponding OR decreased from 1.11 to 0.86) and among girls by 34.0% (the corresponding OR decreased from 1.41 to 1.12). Over the study period, changing social variables had little impact on the daily consumption of vegetables and other foods.</p> <p>Conclusions</p> <p>Based on the food consumption trends observed in Lithuania, increases in consumption of fruits and vegetables should be promoted, along with a reduction in the intake of less healthy choices, such as soft drinks and high-fat, high-sugar snack foods, by diminishing social inequalities in food consumption.</p

ДИНАМИКА СВОБОДНЫХ НОСИТЕЛЕЙ В ТЯЖЕЛЫХ СКИНТИЛЯЦИОННЫХ МАТЕРИАЛАХ СО СТРУКТУРОЙ ГРАНАТА

Ce-doped Lu3 Al5 O12 (LuAG), and Gd3 Al2 Ga3 O12 (GAGG) crystals with and without codoping by Mg2+ ions have been studied by the nonlinear absorption spectroscopy method. A faster rise time of transient optical absorption has been observed in all crystals codoped with Mg in comparison to Mg-free samples. A significant difference in the time evolution of the differential optical density in GAGG in comparison to LuAG crystals is revealed. in gadolinium garnets an absorption band peaked in the blue-green range and decaying with characteristic time of ~2 ps is observed. This band is considered to be due to absorption of free electrons before their trapping by Ce3+doping ions. A broad transient absorption band in the yellowred region is attributed to absorption from the Ce3+ excited states. Легированные ионами Се кристаллы Lu3 Al5 O12 (LuAG) и Gd3 Al2 Ga3 O12 (GAGG) с и без кодопирования ионами Mg2+ исследованы методом нелинейной абсорбционной спектроскопии. Ускорение времени нарастания переходного оптического поглощения наблюдалось в кристаллах, кодопированных ионами Mg, по сравнению с образцами без Mg. Выявлено существенное различие во временной эволюции дифференциальной оптической плотности в GAGG в сравнении с кристаллом LuAG. В гадолиниевых гранатах наблюдается полоса поглощения в сине- зеленом диапазоне с затуханием с характерным временем ~2 пс. Эта полоса соотнесена поглощению свободными электронами до их захвата примесными ионами Ce3+. Широкая полоса переходного поглощения в желто-красной области обусловлена поглощением из возбужденных состояний ионов Ce3+.

Garnet-based complex substituted glass ceramic materials

В статье рассмотрен комплекс гранулированных стеклокерамических материалов на основе граната

Improvement of response time in GAGG:Ce scintillation crystals by magnesium codoping

Dynamics of the population of the excited Ce states responsible for the luminescence response time in Gd3Al2Ga3O12:Ce scintillating crystals is studied by revealing the dynamics of nonequilibrium carriers in the picosecond domain. Optical pump and probe technique exploiting selective excitation of structural units of the crystal and probing the induced absorption as a function of time and spectral position is exploited. A fast response within a few picoseconds due to the absorption by holes at Gd ions and by electrons occupying the first excited state of Ce ions with the intracenter relaxation time of 500 fs are identified. Trapping of nonequilibrium electrons during their migration through the matrix to the emitting Ce ions are shown to be responsible for the slow component in the population of the excited Ce state. Elimination of the slow component is evidenced even at Mg codoping as low as 10 ppm. The elimination correlates with the acceleration of the response in coincidence time resolution experiments showing potential of GAGG:Ce, Mg in medical and high-energy physics applications

Timing properties of Ce-doped YAP and LuYAP scintillation crystals

The timing performance of radiation detectors based on Ce-doped perovskites YAlO3 (YAP) and (Lu1−x-Yx) AlO3 (LuYAP) coupled with near-UV sensitive silicon photomultipliers (NUV-HD SiPMs) have been compared in coincidence time resolution (CTR) experiments. The single-detector time resolution full width at half maximum (FWHM) of YAP was found to be 169 ps, i.e., by a factor of two better than that observed earlier with photomultiplier readout. Introduction of lutetium into YAP structure deteriorates the time resolution to 286 ps and 309 ps for a Lu/Y atomic ratio of 1:1 and 0.7:0.3, respectively. The study of the dynamics of Ce3+ excited state population after selective optical excitation with short (200 fs) pulses by using the differential absorption technique in pump and probe configuration evidenced the importance of electron trapping, which is enhanced by antisite LuAl defects having favorable conditions to occur in LuAP