Experimental Evidence of Marangoni Convection Rolls in Belousov-Zhabotinsky Reaction

1997 ◽  
pp. 135-137
Author(s):  
Osamu Inomoto ◽  
Akemi Sakaguchi ◽  
Shoichi Kai
Keyword(s):  
Experimental Evidence ◽  
Marangoni Convection ◽  
Convection Rolls ◽  
Belousov Zhabotinsky Reaction

scholarly journals Spatial Heterogeneity and Imperfect Mixing in Chemical Reactions: Visualization of Density-Driven Pattern Formation

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
Sabrina G. Sobel ◽  
Harold M. Hastings ◽  
Matthew Testa
Keyword(s):  
Pattern Formation ◽  
Salt Water ◽  
Model System ◽  
Reaction Vessel ◽  
Chemical System ◽  
Industrial Processes ◽  
History Of ◽  
Convection Rolls ◽  
Belousov Zhabotinsky Reaction ◽  
Complex Ion

Imperfect mixing is a concern in industrial processes, everyday processes (mixing paint, bread machines), and in understanding salt water-fresh water mixing in ecosystems. The effects of imperfect mixing become evident in the unstirred ferroin-catalyzed Belousov-Zhabotinsky reaction, the prototype for chemical pattern formation. Over time, waves of oxidation (high ferriin concentration, blue) propagate into a background of low ferriin concentration (red); their structure reflects in part the history of mixing in the reaction vessel. However, it may be difficult to separate mixing effects from reaction effects. We describe a simpler model system for visualizing density-driven pattern formation in an essentially unmixed chemical system: the reaction of pale yellow Fe3+ with colorless SCN− to form the blood-red Fe(SCN)2+ complex ion in aqueous solution. Careful addition of one drop of Fe(NO3)3 to KSCN yields striped patterns after several minutes. The patterns appear reminiscent of Rayleigh-Taylor instabilities and convection rolls, arguing that pattern formation is caused by density-driven mixing.

scholarly journals New evidence of transient complex oscillations in a closed, well-stirred belousov-zhabotinsky system

2006 ◽  
Vol 71 (6) ◽  
pp. 605-612 ◽  
Author(s):  
Ljiljana Kolar-Anic ◽  
Slavica Blagojevic ◽  
Natasa Pejic ◽  
Nebojsa Begovic ◽  
Stevan Blagojevic ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Malonic Acid ◽  
Batch Reactor ◽  
One Dimensional ◽  
Transient Complex ◽  
One Dimensional Maps ◽  
New Evidence ◽  
Belousov Zhabotinsky Reaction ◽  
Influence Of Noise

Some new experimental evidence of complex irregular oscillations in the Belousov-Zhabotinsky reaction realized in a batch reactor is presented. The results were obtained under relatively low cerium and malonic acid concentrations. One-dimensional maps were used for general discussion, and particularly, for the influence of noise on the evolution of the oscillations.

EXPERIMENTAL EVIDENCE ON THE STRUCTURE AND EVOLUTION OF THE PENTA–HEPTA DEFECT IN HEXAGONAL LATTICES DUE TO BÉNARD–MARANGONI CONVECTION

2001 ◽  
Vol 11 (05) ◽  
pp. 1261-1273 ◽  
Author(s):  
V. O. AFENCHENKO ◽  
A. B. EZERSKY ◽  
A. V. NAZAROVSKY ◽  
M. G. VELARDE
Keyword(s):  
Experimental Evidence ◽  
Qualitative Agreement ◽  
Marangoni Convection ◽  
Hexagonal Lattice ◽  
Experimental Results ◽  
Numerical Calculations ◽  
Good Qualitative Agreement ◽  
Topological Charges

Evidence is provided to show that the penta–hepta defect in a Bénard convective hexagonal lattice arises as a result of the attraction of two dislocations having opposite topological charges and belonging to different modes. The dislocations approach each other along a corridor connecting those topological charges. Fields of long–living penta–hepta defects have been analyzed. The comparison of experimental results with recent numerical calculations and solutions obtained analytically shows good qualitative agreement.

Inertial Bénard–Marangoni convection

1997 ◽  
Vol 350 ◽  
pp. 149-175 ◽  
Author(s):  
THOMAS BOECK ◽  
ANDRÉ THESS
Keyword(s):  
Prandtl Number ◽  
Marangoni Number ◽  
Marangoni Convection ◽  
Pseudospectral Method ◽  
Critical Value ◽  
Two Dimensional ◽  
Conductive Temperature ◽  
Reasonable Approximation ◽  
Convection Rolls ◽  
Dimensional Surface

Two-dimensional surface-tension-driven Bénard convection in a layer with a free-slip bottom is investigated in the limit of small Prandtl number using accurate numerical simulations with a pseudospectral method complemented by linear stability analysis and a perturbation method. It is found that the system attains a steady state consisting of counter-rotating convection rolls. Upon increasing the Marangoni number Ma the system experiences a transition between two typical convective regimes. The first one is the regime of weak convection characterized by only slight deviations of the isotherms from the linear conductive temperature profile. In contrast, the second regime, called inertial convection, shows significantly deformed isotherms. The transition between the two regimes becomes increasingly sharp as the Prandtl number is reduced. For sufficiently small Prandtl number the transition from weak to inertial convection proceeds via a subcritical bifurcation involving weak hysteresis. In the viscous zero-Prandtl-number limit the transition manifests itself in an unbounded growth of the flow amplitude for Marangoni numbers beyond a critical value Mai. For Ma<Mai the zero-Prandtl-number equations provide a reasonable approximation for weak convection at small but finite Prandtl number. The possibility of experimental verification of inertial Bénard–Marangoni convection is briefly discussed.

Asymmetric coupling stabilizes the out-of-phase mode: experimental evidence in the Belousov—Zhabotinsky reaction

1992 ◽  
Vol 189 (1) ◽  
pp. 18-22 ◽  
Author(s):  
Minoru Yoshimoto ◽  
Kenichi Yoshikawa ◽  
Yoshihito Mori ◽  
Ichiro Hanazaki
Keyword(s):  
Experimental Evidence ◽  
Asymmetric Coupling ◽  
Belousov Zhabotinsky Reaction

How do memory modules differentially contribute to familiarity and recollection?

2019 ◽  
Vol 42 ◽  
Author(s):  
Olya Hakobyan ◽  
Sen Cheng
Keyword(s):  
Recognition Memory ◽  
Experimental Evidence ◽  
Subjective Experience ◽  
Target Article ◽  
Memory Modules ◽  
Familiarity And Recollection ◽  
Memory Contents

Abstract We fully support dissociating the subjective experience from the memory contents in recognition memory, as Bastin et al. posit in the target article. However, having two generic memory modules with qualitatively different functions is not mandatory and is in fact inconsistent with experimental evidence. We propose that quantitative differences in the properties of the memory modules can account for the apparent dissociation of recollection and familiarity along anatomical lines.

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz
Keyword(s):  
Experimental Evidence ◽  
Lipid Membranes ◽  
Energy Supply ◽  
Redox Reactions ◽  
Living Systems ◽  
Asymmetric Distribution ◽  
Conservation Of Energy ◽  
Asymmetrical Distribution ◽  
Energy Conserving ◽  
Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

A Method for Setting the Clearance Angle

1972 ◽  
Vol 30 ◽  
pp. 388-389
Author(s):  
Michael T. Bucek ◽  
Howard J. Arnott
Keyword(s):  
Experimental Evidence ◽  
Light Source ◽  
Black Spot ◽  
Critical Factor ◽  
Clearance Angle ◽  
Crude Approximation ◽  
Ultrathin Sections

It is believed by the authors, with supporting experimental evidence, that as little as 0.5°, or less, knife clearance angle may be a critical factor in obtaining optimum quality ultrathin sections. The degree increments located on the knife holder provides the investigator with only a crude approximation of the angle at which the holder is set. With the increments displayed on the holder one cannot set the clearance angle precisely and reproducibly. The ability to routinely set this angle precisely and without difficulty would obviously be of great assistance to the operator. A device has been contrived to aid the investigator in precisely setting the clearance angle. This device is relatively simple and is easily constructed. It consists of a light source and an optically flat, front surfaced mirror with a minute black spot in the center. The mirror is affixed to the knife by placing it permanently on top of the knife holder.

Introductory Remarks

1980 ◽  
Vol 38 ◽  
pp. 598-599
Author(s):  
H. Mohri
Keyword(s):  
Muscle Contraction ◽  
Experimental Evidence ◽  
Sea Urchin ◽  
Constant Length ◽  
Thin Filaments ◽  
Bridge Formation ◽  
Thick Filaments ◽  
Sliding Mechanism ◽  
Radial Spokes ◽  
Cilia And Flagella

In 1959, Afzelius observed the presence of two rows of arms projecting from each outer doublet microtubule of the so-called 9 + 2 pattern of cilia and flagella, and suggested a possibility that the outer doublet microtubules slide with respect to each other with the aid of these arms during ciliary and flagellar movement. The identification of the arms as an ATPase, dynein, by Gibbons (1963)strengthened this hypothesis, since the ATPase-bearing heads of myosin molecules projecting from the thick filaments pull the thin filaments by cross-bridge formation during muscle contraction. The first experimental evidence for the sliding mechanism in cilia and flagella was obtained by examining the tip patterns of molluscan gill cilia by Satir (1965) who observed constant length of the microtubules during ciliary bending. Further evidence for the sliding-tubule mechanism was given by Summers and Gibbons (1971), using trypsin-treated axonemal fragments of sea urchin spermatozoa. Upon the addition of ATP, the outer doublets telescoped out from these fragments and the total length reached up to seven or more times that of the original fragment. Thus, the arms on a certain doublet microtubule can walk along the adjacent doublet when the doublet microtubules are disconnected by digestion of the interdoublet links which connect them with each other, or the radial spokes which connect them with the central pair-central sheath complex as illustrated in Fig. 1. On the basis of these pioneer works, the sliding-tubule mechanism has been established as one of the basic mechanisms for ciliary and flagellar movement.

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