Energy Requirement of Control: Comments on Szilard's Engine and Maxwell's Demon

In mathematical physical analyses of Szilard's engine and Maxwell's demon, a general assumption (explicit or implicit) is that one can neglect the energy needed for relocating the piston in Szilard's engine and for driving the trap door in Maxwell's demon. If this basic assumption is wrong, then the conclusions of a vast literature on the implications of the Second Law of Thermodynamics and of Landauer's erasure theorem are incorrect too. Our analyses of the fundamental information physical aspects of various type of control within Szilard's engine and Maxwell's demon indicate that the entropy production due to the necessary generation of information yield much greater energy dissipation than the energy Szilard's engine is able to produce even if all sources of dissipation in the rest of these demons (due to measurement, decision, memory, etc) are neglected.Comment: New, simpler and more fundamental approach utilizing the physical meaning of control-information and the related entropy production. Criticism of recent experiments adde

Sexual behaviour in the face of risk : preliminary results from first AIDS-related surveys

Preliminary results are presented from nationally representative surveys of the adult populations of five African countries, conducted in 1989 and 1990. General awareness of AIDS was high, as was knowledge of sexual transmission. In four of the five surveys, large proportions, from 25 to 64 per cent, of both men and women perceived themselves to have a high or moderate risk of HIV infection. High proportions also reported that they had modified their behaviour typically by more care in selecting partners or greater faithfulness. Greater use of condoms was mentioned rarely. The results, particularly on behavioural change, should not be interpreted literally. But the fact that so many report modification of behaviour at least suggests a willingness to contemplate the need for change. The prognosis would have been much worse, had these surveys indicated widespread denial of risk and unwillingness to consider changes in behaviour

L’Avifaune nidificatrice d’une forêt de chênes pédoncules en bourgogne : étude de deux successions écologiques

Deux types de successions écologiques se développent cycli quement dans les massifs forestiers du Querceto Carpinetum primuletosum de Bourgogne selon l’exploitation forestière en Futaie ou en Taillis-sous-futaie. Nous avons dénombré pendant 9 ans les Passereaux, Picidés et Colombidés nichant dans les divers stades évolutifs des deux successions. Les dénombrements furent effectués par la méthode des IKA couplée avec celle des plans quadrillés, sur 185 échantillons répartis au sein de quelques grands massifs représentent une surface de 6 000 hectares de biotope homogène. 1) Les espèces nicheuses sont, pour la plupart, extrêmement sensibles à la physionomie du peuplement végétal, telle que la déterminent le mode d’exploitation et l’âge de la forêt, à tel point que peu d’entre elles se montrent capables d’habiter une succession d’un bout à l’autre de son évolution. 2) Les dénombrements spécifiques nous montrent des espèces qui ont un preferendum temporaire à un des stades évolutifs et d’autres qui augmentent progressivement jusqu’au climax. Au sein de chaque groupe phvlétique on voit comment les espèces évitent la concurrence en ayant soit des optimums différents soit des limites de tolérances différentes. 3) Beaucoup d’espèces montrent ainsi une préférence pour les jeunes stades initiaux buissonnants (phase à Sylviidés domi nants) et beaucoup d’autres pour les vieux boisements sub-clima- ciques (phase à Paridés dominants), mais très peu trouvent leur optimum dans les hauts buissons ou perchis intermédiaires. 4) Ces préférences spécifiques font que l’abondance totale de l’avifaune évolue selon une courbe à deux maximums séparés par un minimum. Ces deux maximums sont dus respectivement à une avifaune exogène , qui a pu pénétrer nos régions récemment à la suite des défrichements et qui conserve un caractère migra teur, et à Y avifaune endogène sédentaire qui a évolué sur place dans le climax des forêts étudiées. Les stades intermédiaires, créés artificiellement par l’homme, sont trops récents et éphé mères pour avoir permis l’adaptation d’une faune qui leur soit propre et ne conviennent bien à aucune des deux autres faunes. 5) Le nombre d’espèces nicheuses évolue parallèlement à l’abondance totale et il y a une corrélation positive très étroite entre ces deux caractéristiques des avifaunes. 6) La taille moyenne des oiseaux nicheurs augmente du début à la fin des successions. 7) Les avifaunes des deux successions, très différentes au début, montrent de plus en plus de points communs au cours de leur évolution jusqu’à se trouver presque identiques aux derniers stades, où elles représentent une avifaune probablement voisine de celle du climax. 8) Le facteur essentiel de l’abondance totale semble être l 'hétérogénéité du peuplement végétal ; les stades les plus riches en biomasse sont ceux où la physionomie du peuplement est la plus variée, et notamment ceux qui sont capables d’attirer des espèces appartenant aux deux avifaunes précitées. 9) Le sub-climax n’est pas le stade d’abondance ni de diver sité maximales. Par contre, c’est le stade où la taille moyenne des oiseaux est la plus forte et où l’avifaune est la plus sédentaire.Two types of ecological successions develop in semi-natural Quercus pedunculata forests in Burgundy, depending on the type of forestry management undertaken : Shelterwood system (evolving towards High forest) or Coppice-with-standards system. Counts were made over a 9 year period of Passerinæ, Picidæ and Colum- bidæ breeding in the various stages of both successions. A transect method (Kilometric Index Abundance) was used, in conjunction with mapping plots, in 185 different sample areas chosen within a total forest area of 6000 ha. 1) Most breeding species are greatly influenced by vegetation physionomy, as effected by type of exploitation and age of the plot. Few species are capable of colonizing an area throughout the entire time span of a successional sequence. 2) Some species are favoured by a particular succession stage, whilst other species increase in numbers up to the sub-climax. Within each phyletic group, competition pressure is lessened by the different times at which species numbers are at their optimum level and by different tolerance limits to particular successional stages. 3) Many species show a preference for initial low scrub stages (Sylviidæ dominant) and still others for late sub-climax stages (Paridæ dominant). Very few species reach optimum abundance in intermediate high scrub stages (Turdidæ dominant). 4) The curve of total bird numbers follows a wave like form with two peaks of abundance. The first peak is attributable to the influx of exogenous, migratory forms which quickly enter recently cleared areas. The second peak corresponds to endogenous, sedentary forms, living in climax forest areas in the region. Intermediary successional stages, between cleared areas and climax forest, lack a distinct avi-fauna. 5) The number of breeding species parallels, with a high positive correlation, the total bird number. 6) Te mean size of breeding birds increases with the age of the succession. 7) The bird populations of the two successions differ greatly at the start of the successions, but increase in similarity with stand age. In the latter stages of the successions they are practically identical. The faunas at that time closely resemble that associated with the climax. 8) Vegetation heterogeneity is the major factor influencing bird abundance. Highest bird biomasses were recorded when the physionomy of the vegetation showed its greatest variability, thus attracting species belonging to the two groups mentioned above (point 4). 9) In the sub-climax stage, the mean individual size of birds and the proportion of sedentary forms are at their maximal values. On the other hand, neither abundance nor diversity are maximal in this stage

Anisotropic charge transport in non-polar GaN QW: polarization induced charge and interface roughness scattering

Charge transport in GaN quantum well (QW) devices grown in non-polar direction has been theoretically investigated . Emergence of anisotropic line charge scattering mechanism originating as a result of anisotropic rough surface morphology in conjunction with in-plane built-in polarization has been proposed. It has shown that in-plane growth anisotropy leads to large anisotropic carrier transport at low temperatures. At high temperatures, this anisotropy in charge transport is partially washed out by strong isotropic optical phonon scattering in GaN QW.Comment: 4 pages, 4 figure

Collective Charge Fluctuations in Single-Electron Processes on Nano-Networks

Using numerical modeling we study emergence of structure and structure-related nonlinear conduction properties in the self-assembled nanoparticle films. Particularly, we show how different nanoparticle networks emerge within assembly processes with molecular bio-recognition binding. We then simulate the charge transport under voltage bias via single-electron tunnelings through the junctions between nanoparticles on such type of networks. We show how the regular nanoparticle array and topologically inhomogeneous nanonetworks affect the charge transport. We find long-range correlations in the time series of charge fluctuation at individual nanoparticles and of flow along the junctions within the network. These correlations explain the occurrence of a large nonlinearity in the simulated and experimentally measured current-voltage characteristics and non-Gaussian fluctuations of the current at the electrode.Comment: 10 pages, 7 figure

Fingerprinting Soft Materials: A Framework for Characterizing Nonlinear Viscoelasticity

We introduce a comprehensive scheme to physically quantify both viscous and elastic rheological nonlinearities simultaneously, using an imposed large amplitude oscillatory shear (LAOS) strain. The new framework naturally lends a physical interpretation to commonly reported Fourier coefficients of the nonlinear stress response. Additionally, we address the ambiguities inherent in the standard definitions of viscoelastic moduli when extended into the nonlinear regime, and define new measures which reveal behavior that is obscured by conventional techniques.Comment: 10 pages, 3 figures, full-page double-space preprint forma

One- and two-particle microrheology

We study the dynamics of rigid spheres embedded in viscoelastic media and address two questions of importance to microrheology. First we calculate the complete response to an external force of a single bead in a homogeneous elastic network viscously coupled to an incompressible fluid. From this response function we find the frequency range where the standard assumptions of microrheology are valid. Second we study fluctuations when embedded spheres perturb the media around them and show that mutual fluctuations of two separated spheres provide a more accurate determination of the complex shear modulus than do the fluctuations of a single sphere.Comment: 4 pages, 1 figur

Decoherence due to contacts in ballistic nanostructures

The active region of a ballistic nanostructure is an open quantum-mechanical system, whose nonunitary evolution (decoherence) towards a nonequilibrium steady state is determined by carrier injection from the contacts. The purpose of this paper is to provide a simple theoretical description of the contact-induced decoherence in ballistic nanostructures, which is established within the framework of the open systems theory. The active region's evolution in the presence of contacts is generally non-Markovian. However, if the contacts' energy relaxation due to electron-electron scattering is sufficiently fast, then the contacts can be considered memoryless on timescales coarsened over their energy relaxation time, and the evolution of the current-limiting active region can be considered Markovian. Therefore, we first derive a general Markovian map in the presence of a memoryless environment, by coarse-graining the exact short-time non-Markovian dynamics of an abstract open system over the environment memory-loss time, and we give the requirements for the validity of this map. We then introduce a model contact-active region interaction that describes carrier injection from the contacts for a generic two-terminal ballistic nanostructure. Starting from this model interaction and using the Markovian dynamics derived by coarse-graining over the effective memory-loss time of the contacts, we derive the formulas for the nonequilibrium steady-state distribution functions of the forward and backward propagating states in the nanostructure's active region. On the example of a double-barrier tunneling structure, the present approach yields an I-V curve with all the prominent resonant features. The relationship to the Landauer-B\"{u}ttiker formalism is also discussed, as well as the inclusion of scattering.Comment: Published versio

Optimization of Activation Methods for Mouse Oocytes Using Calcium-free CZB Medium, SrCl2, and Cytochalasin B in Vitro

Embryonic stem cells can be obtained by generating an embryo through fertilization; however, an embryo can also be generated asexually through parthenogenesis. This procedure will overcome the ethical issues regarding the use of embryos initially generated for reproductive purposes. The aim of this study was to obtain an optimized oocyte activation method through parthenogenesis by using mice oocytes as a model. Ten mM SrCl2 and 5 µg/ml Cytochalasin B (CB) in calcium-free Chatot Ziomek Bavister (CZB) were used as a medium for an in vitro activation of mouse oocytes. Treatment combinations for the oocyte activation methods were (A) activation in CZB & SrCl2 (prepared in stock) for two hours and in CZB & CB for four hours; (B) activation in CZB & SrCl2 (fresh medium) for two hours and in CZB & CB for four hours; and (C) activation in CZB & CB & SrCl2 (fresh medium) for six hours. The results show that the activation rate of  mouse oocytes  with  method C has  been  the best among all the protocols. This optimized protocol clearly provides a new insight in the generation of embryos for further use, particularly for producing embryonic stem cells