IJS KOLOKVIJ, sreda, 6. 6. 2012, prof. dr. Stephan Herminghaus

[Barbara Hrovatin]

Vabimo vas na 22. predavanje iz sklopa "Kolokviji na IJS" v letu 2011/12, ki
bo v sredo, 6. junija, 2012, ob 13. uri v Veliki predavalnici Instituta
>Jožef Stefan< na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete
tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke
preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

Prof. dr. Stephan Herminghaus

Max Planck Institute for Dynamics and Self-Organization, Göttingen, Nemčija 

 

Eksperimenti z aktivnimi emulzijami

Predstavili bomo eksperimente z emulzijami, za katere je značilno
raznovrstno aktivno obnašanje. V sistemu vodnih kapljic, ki vsebujejo
oscilatorje Belousova in Žabotinskega (BZ), opazimo sklopitvene vzorce,
odvisne od tvorbe lipidnih dvoslojev med njimi: tarčaste, kvorumske in
spiralne valove v dvorazsežnih zaplatah monodisperznih emulzij. Pri manjšem
prostorninskem deležu kapljic se začnejo slednje samodejno gibati in to
gibanje je mogoče nadzorovati z BZ reakcijo. Pojav lahko pojasnimo s
preprostim mehanizmom, zasnovanim na Marangonijevi mehanični napetosti.
Kapljice tvorijo roje z močnimi korelacijami, odvisnimi od gostote kapljic.
Energijo za to vrsto gibanja zagotavlja sproščanje broma pri kemijski
reakciji. Predstavimo tudi soroden tekočekristalni sistem, ki kaže podobno,
a mnogo bolj dolgoživo kolektivno obnašanje, katerega vzrok je spontana
tvorba mikroemulzije. Mezoskopska struktura tekočega kristala ne zene le
gibanja kapljic, temveč vodi tudi do mnogo kompleksnejših vzorcev, ki jih še
ne razumemo v celoti.

Predavanje bo v angleščini.

Lepo vabljeni!

 

*****

 




We would like to invite you to 22nd lecture of the "Kolokvij na IJS" in the
school year 2011/12. The lecture will be held on Wednesday, June 6, 2012, at
1 pm at the JSI main lecture hall, Jamova 39, Ljubljana. The abstract of the
lecture can be found on website:
<http://www.ijs.si/ijsw/Koledar_prireditev>
http://www.ijs.si/ijsw/Koledar_prireditev, the previous recorded lectures
can be found on website:  <http://videolectures.net/kolokviji_ijs>
http://videolectures.net/kolokviji_ijs. 

********************************************

 

Prof. dr. Stephan Herminghaus

Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

 

Experiments with active emulsions

 

Experiments are presented with emulsions showing various types of 'active'
collective behavior. Ensembles of aqueous droplets containing
Belouzov-Zhabotinski (BZ) oscillators are shown to exhibit coupling patterns
depending on the formation of lipid bilayers between them. We observe target
waves, quorum sensing, and spiral waves in two-dimensional rafts of
mono-disperse emulsions. As the volume fraction of the dispersed phase
(i.e., the droplets) is reduced, we observe self-propelled motion of the
droplets, which can be controlled by the BZ reaction if desired. We propose
a simple mechanism based on Marangoni stresses which accounts for this
motion. Swarming is shown to exhibit pronounced correlation features which
depend strongly on the raft density. While the bromine release provides the
energy source for this type of self-propulsion, we present an alternative
system based on liquid crystals which shows similar collective behaviour,
but whose motion has a longer lifetime and is fuelled by the spontaneous
formation of a microemulsion. Based on the meso-structure of the liquid
crystal, it enables, aside from simple droplet motion,  much more complex
patterns to evolve, the details of which are yet far from understood.

 

We look forward to meeting you at the "Kolokvij na IJS"!

 

 

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