Light Perception in Two Strictly Subterranean Rodents: Life in the Dark or Blue?

BACKGROUND: The African mole-rats (Bathyergidae, Rodentia) are strictly subterranean, congenitally microphthalmic rodents that are hardly ever exposed to environmental light. Because of the lack of an overt behavioural reaction to light, they have long been considered to be blind. However, recent anatomical studies have suggested retention of basic visual capabilities. In this study, we employed behavioural tests to find out if two mole-rat species are able to discriminate between light and dark, if they are able to discriminate colours and, finally, if the presence of light in burrows provokes plugging behaviour, which is assumed to have a primarily anti-predatory function. METHODOLOGY/PRINCIPAL FINDING: We used a binary choice test to show that the silvery mole-rat Heliophobius argenteocinereus and the giant mole-rat Fukomys mechowii exhibit a clear photoavoidance response to full-spectrum ("white"), blue and green-yellow light, but no significant reaction to ultraviolet or red light during nest building. The mole-rats thus retain dark/light discrimination capabilities and a capacity to perceive short to medium-wavelength light in the photopic range of intensities. These findings further suggest that the mole-rat S opsin has its absorption maximum in the violet/blue part of the spectrum. The assay did not yield conclusive evidence regarding colour discrimination. To test the putative role of vision in bathyergid anti-predatory behaviour, we examined the reaction of mole-rats to the incidence of light in an artificial burrow system. The presence of light in the burrow effectively induced plugging of the illuminated tunnel. CONCLUSION/SIGNIFICANCE: Our findings suggest that the photopic vision is conserved and that low acuity residual vision plays an important role in predator avoidance and tunnel maintenance in the African mole-rats

Calculations of photoelectron spectra of small water clusters using the independent molecule model

The aim of this thesis is to investigate theoretically photoelectron spectra of small water molecular clusters. This work is motivated by the recent experimental results of Hartweg et al [Phys. Rev. Letters 118, 103402, 2017] which showed that with an increasing number of constituent molecules in the water cluster the asymmetry parameter characterizing the photoelectron angular distribution converges to a universal shape. At the moment there are no theoretical calculations to support this finding. Therefore, we have developed a very simple model of photoionization of molecular clusters based on the use of photoionization data for a single molecule. We have found that the results of our model are sensitive to the different conformations of the clusters. Some of our results for the photoelectron angular distribution exhibit trends observed in the experiment. Nevertheless, the validity of our model will have to be studied in the future with the help of accurate calculations before the results can be conclusively interpreted

Výpočty fotoelektronových spekter malých vodních clusterů pomocí modelu nezávislých molekul

Cílem této bakalářské práce je teoreticky zkoumat spektra fotoelektronů malých vodních molekulárních clusterů. Tato práce je motivovaná nedávnými experimentálními výsledky od Hartwega et al. [Phys. Rev. Letters 118, 103402, 2017], které ukázaly, že parametr asymetrie charakterizující úhlové rozdělení fotoelektronů s rostoucím počtem molekul v clusteru konverguje k jedné univerzální křivce. Momentálně nejsou k dispozici žádné teoretické studie, které by toto zjištění podpořily. Vyvinuli jsme proto velmi jednoduchý model fotoionizace molekulárních clusterů založený na použití dat pro fotoionizaci jedné molekuly. Zjistili jsme, že výsledky našeho modelu jsou citlivé na různé struktury clusterů se stejným počtem molekul. Některé naše výsledky pro úhlové rozdělení fotoelektronů vykazují trendy pozorované v experimentu. Nicméně, platnost našeho modelu bude muset být dále prověřena za pomoci přesných výpočtů předtím, než mohou být naše výsledky jednoznačně interpretovány.The aim of this thesis is to investigate theoretically photoelectron spectra of small water molecular clusters. This work is motivated by the recent experimental results of Hartweg et al [Phys. Rev. Letters 118, 103402, 2017] which showed that with an increasing number of constituent molecules in the water cluster the asymmetry parameter characterizing the photoelectron angular distribution converges to a universal shape. At the moment there are no theoretical calculations to support this finding. Therefore, we have developed a very simple model of photoionization of molecular clusters based on the use of photoionization data for a single molecule. We have found that the results of our model are sensitive to the different conformations of the clusters. Some of our results for the photoelectron angular distribution exhibit trends observed in the experiment. Nevertheless, the validity of our model will have to be studied in the future with the help of accurate calculations before the results can be conclusively interpreted.Ústav teoretické fyzikyInstitute of Theoretical PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

3D data representation and visualization of blocks of buildings generated by means of aggregation generalization method

3D data representation and visualization of building blocks generated by the generalization aggregation method Abstract The bachelor thesis deals with the topic of 3D data representation and visualization. Its main objective is to automate the visualization of the result of the aggregation of LOD2 building blocks, which was performed using optimization method. In the first part, a survey of 3D building and building block generalization methods is performed, focusing on the aggregation method including the optimization problem from which the input data of this thesis comes. Next, an explanation of the actual algorithm design is given. The different phases of the method are discussed, followed by the actual implementation in Python 3. The principle of the actual algorithm is to remove redundant data by visualizing an aggregation of buildings with the same roof type. The minimization of the size of the resulting file is further provided by removing gaps between buildings and aligning the walls of the buildings on the outside of the block. All geometry changes are done under the condition that the volumes of building bodies and roof parts are preserved. Keywords: 3D GIS, generalization, aggregation, generalization automatio

Problem of the gyroscopic stabilizer damping

The gyroscopic stabilization of the vibro-isolation system of an ambulance couch is analyzed. This paper follows several previous papers, which concern the derivation of the complete system of appropriate differential equations and some analyses were provided there, as well. It was supposed that mass matrix, stiffness matrix and gyroscope impulse-moment remain constant and the stability of equilibrium state was solved according to different alternatives of the damping and of the radial correction. Little known theorems of the stability were used there. With respect to these theorems, vibro-isolation systems can be classified according to odd or even number of generalized coordinates

Self-oscillation of the two-axis gyroscopic stabilizer

This article was written at the Technical University of Liberec, Faculty of Mechanical Engineering with the support of the Institutional Endowment for the Long Term Conceptual Development of Research Institutes, as provided by the Ministry of Education, Youth and Sports of the Czech Republic in the year 2018.Van der Pol introduced a solution of the self-oscillations of spring suspended body siting upon the uniform velocity moving rough conveyor belt in 1934. Friction between body and conveyor belt was non-Coulomb, which characteristics has negative slope in the certain interval - see Fig. 1. This classic problem, which is introduced in lots of non-linear vibrations related textbooks, motivated several works whose refer to the fact that solution leads to the same equation (such as pin rotating in hub). Chernikov in demonstrates that transformation of one-axis gyrostabilizer self-oscillations lead to the same equation in certain case. Mentioned Chernikov�s work motivated us to analyze selfoscillations of two-axis gyroscopic stabilizer with non-Coulomb friction in the axis of stabilizer outer gimbal caused by uniform rotation speed of the stabilizer base

NON-LINEAR DAMPING IN THE SYSTEM OF TWO-AXIS GYROSCOPIC STABILIZER

This paper tackles the reasons for the application of the shock absorbers in the mechanical system of the two-axis gyroscopic stabilizer. The procedure of choice of the suitable damping torque characteristics based on the numeric simulations is proposed as well