IN MEMORIAM: In Memoriam: Alexander A Golovin and Alexei M Oparin In Memoriam: Alexander A Golovin and Alexei M Oparin

In Memoriam of Alexander A Golovin (1962-2008) Alexander (Sasha) Golovin passed away on 10 September 2008.

Sasha's scientific heritage includes seminal works in different fields of physics, from Marangoni convection to self-assembly of quantum dots, and from combustion fronts to anomalous diffusion in flows and on a crystal surface. A graduate of the Moscow Institute for Physics and Technology, he had very broad scientific interests and a unique ability to identify and solve new, intellectually challenging and technologically important problems.

One of the basic fields of Sasha's research was the fluid dynamics in systems with interfaces. His favorite subject was the motion of droplets, bubbles and particles in the presence of heat and mass transfer. Sasha's early works contained the discovery of the spontaneous motion of droplets due to the Marangoni effect and the investigation of the interaction between solid particles, bubbles and droplets caused by the Marangoni effect, which is a crucial factor that determines the effect of heat/mass transfer on the rate of coalescence. In both cases, Sasha's work was the first in a long sequence of papers written by different authors. Later, Sasha returned to that field when studying such fascinating subjects as levitation of droplets above the surface of an evaporating liquid and encapsulation of particles and bubbles by an advancing solidification front.

The subject of interfacial hydrodynamics overlaps with another basic field of Sasha's research, the theory of pattern formation. The contribution of Sasha's work to the modern understanding of the variety of pattern formation phenomena is significant. It includes the analysis of the interaction between long-wave and short-wave instability modes in Marangoni convection, investigation of the large-scale Marangoni convection that led to the prediction of different patterns including quasipatterns, and the description of various non-potential effects in Marangoni convection caused by surface deformation. Later, the field of Sasha's interests moved in the direction of small-scale hydrodynamics. His work on the fingering instability of a film wetting the solid substrate was the first truly quantitative work on that subject taking into account the effect of van der Waals interaction. Sasha was also one of the founders of the theory of ultra-thin two-layer films.

The achievements of Sasha Golovin in non-linear dynamics spread beyond hydrodynamics. In a series of papers on the instability of combustion fronts, Sasha investigated generic features of the interactions of different instability modes by the consideration of systems of coupled generic non-linear equations. The basic field of the applications of the pattern formation theory (in a wide sense) in Sasha's works was the materials science. The list of subjects included the studies of different modifications of the convective Cahn-Hilliard equation in the context of the crystal faceting kinetics, self-organization of quantum dots in solid films, formation of nanoscale porous structures, growth of nanowires, and explosive crystallization.

Among the latest directions of Sasha's research were the problem of an active controlling of the pattern formation process (specifically, suppression of morphological instabilities in solidification and prevention of a localized blow-up) and the pattern formation in systems with anomalous diffusion. A paper published in the current issue is devoted to the latter field.

Sasha was an exceptional personality. His unchanging optimism and enthusiasm supported his colleagues and students. He was selfless in helping his friends. Sasha died whilst at the peak point of his creative power. His death is an irretrievable loss for his colleagues and for non-linear science as a whole. We will never forget him, and we believe that his scientific achievements will never be forgotten.

On behalf of Sasha's colleagues and friends, Alexander Nepomnyashchy, Haifa, Israel 20 Dec 2008

In Memoriam of Alexei M Oparin (1964-2008) Alexei (Lesha) Oparin passed away on 4 December 2008.

Alexei graduated from the Moscow Institute for Physics and Technology in 1987, received his PhD at Landau Institute for Theoretical Physics in 1996, and, after training at the Max Plank Institute for Quantum Optics in Germany, worked at the Institute for Computer Aided Design of the Russian Academy of Sciences, where he became the chair of the Department of Numerical Methods and Turbulence. He built the Department so that in a short period of time it grew from 3 to 15 scientists and became one of the leading centers in Russia in numerical modeling of turbulent flows.

In Lesha's works, his talent was combined with the academic depth and the breadth of his scientific interests. Lesha's scientific heritage covers many fields of computational physics, including ignition and burn of deuterium-tritium fuel for the inertial confinement fusion; the flow of matter induced by ultra-short laser impulse; the exact expansion law for the Richtmyer-Meshkov turbulent mixing zone; growth-rate of the Rayleigh-Taylor instability for nuclear fusion; temperature and entropy separation in the Ranque-Hilsch tube; tornado origination from mezzo-cycle; turbulent nature of Jupiter spot; secondary vortex of the gas centrifuge; cascade of instabilities in Couette flow. One of these works is published in this issue.

What make it necessary to get the flow rolled up in zones of high gradients? Why do we have to restrict ourselves to the Reynolds number only, rather than to follow the experiment and get more parameters for stability? Where are the nuts and bolts of the turbulence? Many of these investigations were initiated and led by Lesha, and were based on his ability to identify the essence of the challenging problems and to formulate and address the right questions with mathematical elegance and physical intuition. A lot of work has been done by Lesha. Other problems remain to be solved, to our deep sorrow without him.

Lesha was an extraordinary personality. His professionalism, strength of mind and kindness were a source of enthusiasm for his colleagues and students. Lesha_s early death is an irreplaceable loss. We will always remember him, and his scientific results and achievements will serve as the origin of ideas and inspiration for computational scientists.

Sergei I Anisimov, Nail A Inogamov, Oleg M Belotserkovskii and Oleg Troshkin Moscow, Russia 21 Dec 2008