Statistical physics of active processes in cells

Simple concepts from statistical physics are discussed to describe the transduction of chemical energy of a fuel to mechanical work on the molecular level. Such approaches can characterize general physical features of motor proteins that generate forces in the cell cytoskeleton. In integrated cellular systems such as cilia and hair bundles, cytoskeletal filaments and motors form complex structures and interact in large numbers. In such systems the interplay of filaments and motors can lead to emergent dynamic behaviors such as oscillating collective modes or to wave-like patterns. We discuss general aspects of such dynamic states and relate them to the dynamics of cytoskeletal structures in cells.     

Adhesion of membranes with active stickers

We consider a theoretical model for membranes with adhesive receptors, or stickers, that are actively switched between two conformational states. In their "on" state, the stickers bind to ligands in an apposing membrane, whereas they do not interact with the ligands in their "off" state. We show that the adhesiveness of the membranes depends sensitively on the rates of the conformational switching process. This dependence is reflected in a resonance at intermediate switching rates, which can lead to large membrane separations and unbinding. Our results may provide insights into novel mechanisms for the controlled adhesion of biological or biomimetic membranes.     

Regularities of nuclear physics experiment aboard spacecrafts with long-term active functioning

Although many efforts have been made to ensure the radiation resistance of spacecraft equipment, the active life of space instruments and onboard astrophysical equipment is limited to a large extent by the action of ionizing cosmic rays. Hence, it is necessary to refine the techniques used to predict the radiation resistance, improve the methods for monitoring radiation fields aboard spacecrafts, and find more effective ways to provide radiation protection of the electronic components.     

The nature of physics

The Doppler shift in frequency of an ionospherically reflected radio wave can be used to study various ionospheric disturbances. In this article the experimental arrangement for measuring such a shift is described, and examples of frequency shifts associated with solar flares, geomagnetic variations and travelling disturbances are discussed.     

The physics of diamond

The accurate measurement of the thermal conductivity of metals still poses considerable experimental difficulty. The reasons for this, and the main ways in which the problem has been approached, are summarized. A detailed examination of the development in technique and methods of measurement shows that while most of the steady-state methods introduced over 50 years ago are still being improved, the emphasis in the last few years has been on the development of methods which give more rapid results, particularly at high temperatures.     

The physics of photons

The intensity of the electromagnetic field is treated using the photon wave function in the usual probabilistic sense, as governed by Maxwell's equations. The dynamic characteristics and symmetry properties are determined. The uncertainty relations are found, from which the degree of localization follows for single particle states.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 46–50, September, 1989.     

The physics of golf

A Review of The Physics of Golf. By T. P. Jorgensen. 1994, £27.50 (pbk), pp. 155. AIP, ISBN 0 88318 955 0. Scope: text. Level: non-specialist.     

The physics of lightning

Despite being one of the most familiar and widely recognized natural phenomena, lightning remains relatively poorly understood. Even the most basic questions of how lightning is initiated inside thunderclouds and how it then propagates for many tens of kilometers have only begun to be addressed. In the past, progress was hampered by the unpredictable and transient nature of lightning and the difficulties in making direct measurements inside thunderstorms, but advances in instrumentation, remote sensing methods, and rocket-triggered lightning experiments are now providing new insights into the physics of lightning. Furthermore, the recent discoveries of intense bursts of X-rays and gamma-rays associated with thunderstorms and lightning illustrate that new and interesting physics is still being discovered in our atmosphere. The study of lightning and related phenomena involves the synthesis of many branches of physics, from atmospheric physics to plasma physics to quantum electrodynamics, and provides a plethora of challenging unsolved problems. In this review, we provide an introduction to the physics of lightning with the goal of providing interested researchers a useful resource for starting work in this fascinating field.     

Passive or active fluctuations in membranes containing proteins

We have experimentally investigated the effect of a transmembrane protein, the Ca2+-ATPase, on shape fluctuations of giant vesicles. By using the micropipette method, we have measured a substantial renormalization of the bending modulus due to the presence of proteins in the membrane. Moreover, we have produced the first quantitative measurement of the active force dipole associated with the amplification of the fluctuations when the proteins are activated by adenosine 5'-triphosphate (ATP).     

Stochastic resonance for adhesion of membranes with active stickers

The behavior of two membranes that interact by active adhesion molecules or stickers is studied theoretically using mean-field theory and Monte Carlo simulations. The stickers are anchored in one of the membranes and undergo conformational transitions between on and off states. In their on states, the stickers can bind to ligands that are anchored in the other membrane. The transitions between the on and off states arise from the coupling of the stickers to some active, energy-releasing process, which keeps the system out of equilibrium. As one varies the transition rates of this active process, the membrane separation undergoes a stochastic resonance: this separation is maximal at intermediate rates of the sticker transitions and considerably smaller both at high and at low transition rates. This implies that the effective, fluctuation-induced repulsion between the membranes contains a rate-dependent contribution that arises from the switching of the active stickers.     

The readability of physics papers

Czechoslovak Journal of Physics - This seems to provide the main answer to the question — Have physics papers become more unreadable with time? It all depends on what you mean by...     

The physics of inorganic scintillators

Boston University, Department of chemistry, Boston, MA 02215, USA. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 4, pp. 209–231, July–August, 1995.     

The state of ferroelectric physics

Conclusions It can be concluded from this review that ferroelectric physics is one of the actively expanding branches of solid-state physics. The concepts of states related to the ferroelectric one, e.g., the ferroelastic state, have broadened significantly. Within this field successful studies are being performed of such general questions as phase transitions, subsystem interactions, i.e., the interaction of different quasiparticles, and other nonlinear processes. In ferroelectric semiconductors the interaction of charge carriers with spontaneous polarization is being studied, while in Seignette ferromagnetics the interaction of magnetic and electric subsystems is under investigation. Nonlinear phenomena are given special study in the phase transition region.A number of new interesting phenomena have been discovered in ferroelectric studies recently: phonon echo, photovoltaic effect, autolocalization of charge carriers in the phase transition region, etc. Many new classes of ferroelectrics have been discovered, thus demonstrating the broad extent of the ferroelectric state in nature. Apparently, certain organic compounds and liquid crystals may be classified as ferroelectrics. Results of ferroelectric studies are widely used in the national economy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 5–39, January, 1979.     

等离子体刻蚀工艺的物理基础

介绍了等离子体刻蚀工艺背景以及有关等离子体刻蚀机理的研究进展,综述了等离子体刻蚀机理的研究方法,着重阐述了电容耦合放电和电感耦合放电等离子体物理特性,特别是双频电容耦合放电等离子体和等离子体鞘层研究中的关键问题.