Research

Below you can see some of our students research projects.

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Accretion onto the Companion of Eta Carinae

65625733

 

 

Amit Kashi worked on his PhD under the supervision of Prof. Noam Soker. The title of his thesis is "The Periastron Passage of the Binary star Eta Carinae".

Amit is fascinated by this star and the variety of physical processes that  take place in the binary system, and studied this system from almost every possible aspect. Amit is presently working on a few more subjects: Transient events (strange astrophysical explosions with energy between Nova and Supernova, which cannot be explained by simple processes), mass transfer in binaries, and formation of planets, brown dwarfs and stars around very massive stars of 100 solar mass or more.
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How vision begins: The light-matter interaction in the retina

How vision begins: The light-matter interaction in the retina

Amichai M. Labin

Advisors: Dr. Erez N Ribak & Prof. Ido Perlman.

The most primary step of vision is the absorption of light by cones and rods visual pigments [1]. The efficiency of this process was found to be largely affected by the pigment properties, its spontaneous activation and molecular thermal energy [2]. These intrinsic constraints are the basis of a ~100-fold difference in sensitivity between rods and cones, and pose fundamental limits on visual information transduction [3, 4]. Another prominent feature of the light-matter interaction in the retina is the ability of photoreceptors to guide light and therefore affect photon absorbance characteristics. But given these two key features, what can we say about there interrelations? Are these a two isolated phenomenon, or is there a preliminary task which other cells carry out for cones and rods pigments? Here we address these questions by following the path of light in the vertebrate retina, experimentally and theoretically [5].

1. Baylor, D.A., T.D. Lamb, and K.W. Yau, Responses of retinal rods to single photons. The Journal of Physiology, 1979. 288(1): p. 613-634.
2. Luo, D.-G., et al., Activation of Visual Pigments by Light and Heat. Science, 2011. 332(6035): p. 1307-1312.
3. Baylor, D., How photons start vision. Proceedings of the National Academy of Sciences, 1996. 93(2): p. 560-565.
4. Bowmaker, J.K. and H.J. Dartnall, Visual pigments of rods and cones in a human retina. J Physiol, 1980. 298: p. 501-11.
5. Labin, A.M. and E.N. Ribak, Retinal glial cells enhance human vision acuity. Phys Rev Lett. 104(15): p. 158102.

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Self Similar Modes of Coherent Diffusion

O. Firstenberg,A D. Yankelev,A P. London,A M. Shuker,A R. Pugatch,B and N. DavidsonB

A. Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel ( This email address is being protected from spambots. You need JavaScript enabled to view it. This e-mail address is being protected from spambots. You need JavaScript enabled to view it )

B. Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel

When a resonant light pulse propagates slowly through a vapor medium of hot diffusing atoms, the electromagnetic field exhibits diffusion, in addition to the regular free-space diffraction [1]. The extent of the diffusion depends on the degree of atomic excitation, which is maximal when storage of light is performed. For the latter, the evolution of the atomic coherence is described by the coherent diffusion equation yankelev-d-r-2where ψ is a complex scalar.

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Lamellipodial fragments as a model system of self-organization in actin-based motility

39074034Ofer Noa

Cell motility is a remarkable dynamic process which is crucial for many biological processes such as wound healing, fertilization and pathologic cases such as cancer metastasis. A moving cell is a self-organized mechano-chemical machine in which molecular components interact at small scales to generate forces and motion on much larger scales. The majority of animal cells crawl by actin-based motility where forward movement depends on the assembly and disassembly of a network formed by a protein named actin.

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Accessing the dark exciton with light

33924457 Eilon Poem

The dark exciton is a non-optical excited state of a semiconductor. When electronic excitation in a semiconductor occurs, an electron (which has a negative charge) "jumps" from the full, lower-energy valence band, to the higher-energy, empty conduction band. The missing electron in the valence band is called a "hole", and its electric charge is positive. The electron and the hole electrically attract one another, until they are "bound". A bound electron-hole pair is called an "exciton".

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