Research topics

Research Topics at the Department of Biological Physics

 

SELF-PROPELLED PARTICLES

kiskep_csopmozgszimul.jpgWe investigate models of collective motion since 1995, when the self-propelled particles (SPP) model was proposed by Prof. Vicsek et al. to describe the onset of ordered motion within a group of self-propelled particles in the presence of perturbations. Due to its simplicity and analogy with biological systems consisting of many, locally interacting particles, the SPP model soon became a reference model for the description of flocking behavior of organisms. The ongoing modeling projects reveal new aspects of this interesting topic. https://hal.elte.hu/flocking/

BIOOPTICS
- Paleo-biooptical reconstruction of the eyes and vision of trilobites: 01_vizcseppes_level.jpgthe oldest preserved visual system
- Refraction-distorted binocular visual field of animals living at the air-water interface
- Optics of animal eyes
- Optics of sunlit water drops on leaves: conditions under which sunburn is possible

FLOCKING
kiskep_galambcsapat.jpg

Track logs of homing pigeons flying in flocks within a natural setting have been obtained by high-resolution lightweight GPS devices and analysed using a variety of correlation functions inspired by approaches common in statistical physics. We find a well-defined hierarchy among flock members from data concerning leading roles in pairwise interactions, defined on the basis of characteristic delay times between birds' directional choices. The average spatial position of a pigeon within the flock strongly correlates with its place in the hierarchy, and birds respond more quickly to conspecifics perceived primarily through the left eye — both results revealing differential roles for birds that assume different positions with respect to flock-mates. https://hal.elte.hu/flocking/


BIOMECHANCS
- Sports mechanics: influence of environmental factors on shot put and 02_hibas_lojaras.jpghammer throw range
- Bone mechanics: testing the biomechanical optimality of the wall thickness of limb bones in mammals and birds
- Erroneous quadruped walking depictions in natural history museums
- Swimming movements and swarming in whirligig beetles

CLUSTERS & COMMUNITIES
CFinderA cluster (also called a community or module) in a network is a group of nodes more densely connected to each other than to nodes outside the group. In most real networks in nature and societies clusters often overlap. CFinder offers a fast and efficient method for identifying the overlapping clusters of data represented by large graphs, such as genetic or social networks and microarray data. CFinder can be downloaded from http://CFinder.org as a free software for analyzing and visualizing overlapping dense groups of nodes in networks. The image shows the modules and the network of modules (identified with CFinder) in the protein-protein interaction network of the yeast, Saccharomyces cerevisiae.

autonomousflyingrobots.jpg
COLLECTIVE BEHAVIOR
We develope an experimental setup of simple self-propelled robots (boats) that show collective behavior based on only collisions in a two dimensional toroidal space. In our experiments the role of leaders can be studied in a system with a presence of noise. https://hal.elte.hu/flocking/

IMAGING POLARIMETRY
03_szkarabeusz.jpg- Ground-based full-sky imaging polarimetry of rapidly changing skies and its use for polarimetric cloud detection
- Imaging polarimetry of the circularly polarizing cuticle of metallic shiny scarab beetles
- Stereo videopolarimetry: measuring and visualizing polarization patterns in three dimensions
- Measurement of the reflection-polarization pattern of the flat water surface under different meteorological conditions

POLARIZATION VISION

- Polarization-induced false colours: how the polarization of light influences insect colour perception
- Why do dusk-active cockchafers (Melolontha melolontha) detect polarization in the green?04a_pol_hamisszinek.jpg
- Why is it advantageous for animals to detect celestial polarization in the ultraviolet?
- No evidence for positive polarotaxis in the yellow fever mosquito ( Aedes aegypti)
- Polarization vision and polarotaxis in dragonflies (Odonata), mayflies (Ephemeroptera) and tabanid flies (Tabanidae)
- A polarisation sun-dial dictates the optimal time of day for dispersal by flying polarotactic aquatic insects
- An unexpected advantage of whiteness in horses: the most horsefly-proof horse has a depolarizing white coat 


MULTIFRACTAL NETWORK GENERATOR

kiskep_halozatkut2.jpg

Random graph models reproducing the statistical properties of real networks provide an important subject in complex network theory as they can help the deeper understanding of the structure, function and origin of the investigated systems. An interesting new direction in this field is to use multifractal measures for generating random graphs, where the linking probability between the node pairs is determined by a multifractal. By varying the parameters of the multifractal the statistical properties of the generated graphs can undergo major changes as well, and certain methods enable one to also fit this framework to a given real network.

MEXICAN WAVE
kiskep_mexikoihullam.jpgThe Mexican wave, or La Ola, which rose to fame during the 1986 World Cup in Mexico, surges through the rows of spectators in a stadium as those in one section leap to their feet with their arms up, and then sit down again as the next section rises to repeat the motion. Modelling the reaction of the crowd to attempts to trigger the wave reveals how this phenomenon is stimulated, and may prove useful in controlling events that involve groups of excited people.

PANIC
kiskep_panik.jpg
One of the most disastrous forms of collective human behaviour is the kind of crowd stampede induced by panic, often leading to fatalities as people are crushed or trampled. Here we use a model of pedestrian behaviour to investigate the mechanisms of (and preconditions for) panic and jamming by uncoordinated motion in crowds. Our simulations suggest practical ways to prevent dangerous crowd pressures.

CELESTIAL POLARIZATION PATTERNS
  - Spatiotemporal change of sky polarization during total solar eclipses measured by full-sky imaging polarimetry
- Polarization patterns of thick clouds
- Imaging polarimetry of forest canopies: polarization patterns of the sunlit foliage
05_neutralis_pontok.jpg- Anomalous celestial polarization caused by forest fire smoke
- Atmospheric optical prerequisites of the polarimetric Viking navigation under foggy and cloudy skies
- Polarization of water-skies above arctic open waters (polynyas)
- Skylight polarization transmitted through the Snell's window of the flat water surface
- How well does the Rayleigh model describe the E-vector distribution of skylight in clear and cloudy conditions?
- Imaging polarimetry of the rainbow
- First observation of the fourth neutral polarization point in the atmosphere
- Polarization patterns of the moonlit clear night sky: comparison of the polarization of moonlit and sunlit skies

POLARIZED LIGHT POLLUTION
- Asphalt surfaces as ecological traps for water-seeking polarotactic insects
- How can the polarized light pollution of asphalt surfaces be reduced?
06_voros_auton_vizibogar.jpg- Reducing the maladaptive attractiveness of solar panels to polarotactic insects
- Attraction of dragonflies to horizontally polarizing black gravestones
- Why do red and dark-coloured cars lure aquatic insects?
- Oil reservoirs and plastic sheets as polarized traps for aquatic insects
- Visual ecological impact of a peculiar waste oil lake and plastic sheets on the avifauna
- Glass buildings on river banks as polarized light traps for mass-swarming polarotactic caddis flies
- Glass buildings as bird feeders: urban birds exploit insects trapped by polarized light pollution
- Wagtails (Aves: Motacillidae) as insect indicators on plastic sheets attracting polarotactic aquatic insects

POLARIZATION TABANID TRAPS07_tabanoid.jpg
- Ventral polarization vision in tabanid flies: tabanids (Diptera: Tabanidae) are attracted to horizontally polarized light
- Practical applications of polarotaxis in tabanid flies
- TabaNOid: polarization tabanid trap technology

kiskep_sejt.jpg

THERMALLING
kiskep_termik.jpg
Gliding saves much energy, and to make large distances using only this form of flight represents a great challenge for both birds and people. Are there any analogies between the solutions birds and humans find to handle the above task? High-resolution track logs were taken from thermalling falcons and paraglider pilots to determine the essential parameters of the flight patterns. We find that there are relevant common features, in particular, falcons seem to reproduce the MacCready formula widely used by gliders to calculate the best slope to take before an upcoming thermal.

CARBON NANOSTRUCTURES
Szén nanocsövek
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. These cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential uses in architectural fields. Basic properties (e.g. vibrational and eletronic dispersion) of these materials are investigated at the density functional theory level by our group.