678 research outputs found
Traffic of Molecular Motors
Molecular motors perform active movements along cytoskeletal filaments and
drive the traffic of organelles and other cargo particles in cells. In contrast
to the macroscopic traffic of cars, however, the traffic of molecular motors is
characterized by a finite walking distance (or run length) after which a motor
unbinds from the filament along which it moves. Unbound motors perform Brownian
motion in the surrounding aqueous solution until they rebind to a filament. We
use variants of driven lattice gas models to describe the interplay of their
active movements, the unbound diffusion, and the binding/unbinding dynamics. If
the motor concentration is large, motor-motor interactions become important and
lead to a variety of cooperative traffic phenomena such as traffic jams on the
filaments, boundary-induced phase transitions, and spontaneous symmetry
breaking in systems with two species of motors. If the filament is surrounded
by a large reservoir of motors, the jam length, i.e., the extension of the
traffic jams is of the order of the walking distance. Much longer jams can be
found in confined geometries such as tube-like compartments.Comment: 10 pages, latex, uses Springer styles (included), to appear in the
Proceedings of "Traffic and Granular Flow 2005
Walks of molecular motors in two and three dimensions
Molecular motors interacting with cytoskeletal filaments undergo peculiar
random walks consisting of alternating sequences of directed movements along
the filaments and diffusive motion in the surrounding solution. An ensemble of
motors is studied which interacts with a single filament in two and three
dimensions. The time evolution of the probability distribution for the bound
and unbound motors is determined analytically. The diffusion of the motors is
strongly enhanced parallel to the filament. The analytical expressions are in
excellent agreement with the results of Monte Carlo simulations.Comment: 7 pages, 2 figures, to be published in Europhys. Let
Two-particle interference of electron pairs on a molecular level
We investigate the photo-doubleionization of molecules with 400 eV
photons. We find that the emitted electrons do not show any sign of two-center
interference fringes in their angular emission distributions if considered
separately. In contrast, the quasi-particle consisting of both electrons (i.e.
the "dielectron") does. The work highlights the fact that non-local effects are
embedded everywhere in nature where many-particle processes are involved
Leading-effect vs. Risk-taking in Dynamic Tournaments: Evidence from a Real-life Randomized Experiment
Two 'order effects' may emerge in dynamic tournaments with information feedback. First, participants adjust effort across stages, which could advantage the leading participant who faces a larger 'effective prize' after an initial victory (leading-effect). Second, participants lagging behind may increase risk at the final stage as they have 'nothing to lose' (risk-taking). We use a randomized natural experiment in professional two-game soccer tournaments where the treatment (order of a stage-specific advantage) and team characteristics, e.g. ability, are independent. We develop an identification strategy to test for leading-effects controlling for risk-taking. We find no evidence of leading-effects and negligible risk-taking effects
Comorbid anxiety increases cognitive control activation in Major Depressive Disorder
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134086/1/da22541.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134086/2/da22541_am.pd
Ability of herpes simplex virus vectors to boost immune responses to DNA vectors and to protect against challenge by simian immunodeficiency virus
AbstractThe immunogenicity and protective capacity of replication-defective herpes simplex virus (HSV) vector-based vaccines were examined in rhesus macaques. Three macaques were inoculated with recombinant HSV vectors expressing Gag, Env, and a Tat-Rev-Nef fusion protein of simian immunodeficiency virus (SIV). Three other macaques were primed with recombinant DNA vectors expressing Gag, Env, and a Pol-Tat-Nef-Vif fusion protein prior to boosting with the HSV vectors. Robust anti-Gag and anti-Env cellular responses were detected in all six macaques. Following intravenous challenge with wild-type, cloned SIV239, peak and 12-week plasma viremia levels were significantly lower in vaccinated compared to control macaques. Plasma SIV RNA in vaccinated macaques was inversely correlated with anti-Rev ELISPOT responses on the day of challenge (P value<0.05), anti-Tat ELISPOT responses at 2Â weeks post challenge (P value <0.05) and peak neutralizing antibody titers pre-challenge (P value 0.06). These findings support continued study of recombinant herpesviruses as a vaccine approach for AIDS
Imaging the square of the correlated two-electron wave function of a hydrogen molecule
The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H2two-electron wave function in which electron-electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sourcesThis work was funded by the Deutsche Forschungsgemeinschaft, the BMBF, the European Research Council under the European Union Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement 290853 XCHEM, the MINECO projects FIS2013-42002-R and FIS2016-77889-R, and the European COST Action XLIC CM1204. All calculations were performed at the CCC-UAM and Mare Nostrum Supercomputer Centers. We are grateful to the staff of PETRA III for excellent support during the beam time. K.M. and M.M. would like to thank the DFG for support via SFB925/A3. A.K. and V.S. thank the Wilhelm und Else Heraeus-Foundation for support. J.L. would like to thank the DFG for support. S.K. acknowledges support from the European Cluster of Advanced Laser Light Sources (EUCALL) project which has received funding from the European Unionâs Horizon 2020 research and innovation programme under grant agreement No 654220. T.W. was supported by the U.S. Department of Energy Basic Energy Sciences under Contract No. DE-AC02-05CH11231. A.P. acknowledges a RamĂłn y Cajal contract from the Ministerio de Economa y Competitivida
Protein Phosphatase Magnesium Dependent 1A (PPM1A) Plays a Role in the Differentiation and Survival Processes of Nerve Cells
The serine/threonine phosphatase type 2C (PPM1A) has a broad range of substrates, and its role in regulating stress response is well established. We have investigated the involvement of PPM1A in the survival and differentiation processes of PC6-3 cells, a subclone of the PC12 cell line. This cell line can differentiate into neuron like cells upon exposure to nerve growth factor (NGF). Overexpression of PPM1A in naive PC6-3 cells caused cell cycle arrest at the G2/M phase followed by apoptosis. Interestingly, PPM1A overexpression did not affect fully differentiated cells. Using PPM1A overexpressing cells and PPM1A knockdown cells, we show that this phosphatase affects NGF signaling in PC6-3 cells and is engaged in neurite outgrowth. In addition, the ablation of PPM1A interferes with NGF-induced growth arrest during differentiation of PC6-3 cells
An Experimental Investigation of Colonel Blotto Games
"This article examines behavior in the two-player, constant-sum Colonel Blotto game with asymmetric resources in which players maximize the expected number of battlefields won. The experimental results support all major theoretical predictions. In the auction treatment, where winning a battlefield is deterministic, disadvantaged players use a 'guerilla warfare' strategy which stochastically allocates zero resources to a subset of battlefields. Advantaged players employ a 'stochastic complete coverage' strategy, allocating random, but positive, resource levels across the battlefields. In the lottery treatment, where winning a battlefield is probabilistic, both players divide their resources equally across all battlefields." (author's abstract)"Dieser Artikel untersucht das Verhalten von Individuen in einem 'constant-sum Colonel Blotto'-Spiel zwischen zwei Spielern, bei dem die Spieler mit unterschiedlichen Ressourcen ausgestattet sind und die erwartete Anzahl gewonnener Schlachtfelder maximieren. Die experimentellen Ergebnisse bestĂ€tigen alle wichtigen theoretischen Vorhersagen. Im Durchgang, in dem wie in einer Auktion der Sieg in einem Schlachtfeld deterministisch ist, wenden die Spieler, die sich im Nachteil befinden, eine 'Guerillataktik' an, und verteilen ihre Ressourcen stochastisch auf eine Teilmenge der Schlachtfelder. Spieler mit einem Vorteil verwenden eine Strategie der 'stochastischen vollstĂ€ndigen Abdeckung', indem sie zufĂ€llig eine positive Ressourcenmenge auf allen Schlachtfeldern positionieren. Im Durchgang, in dem sich der Gewinn eines Schlachtfeldes probabilistisch wie in einer Lotterie bestimmt, teilen beide Spieler ihre Ressourcen gleichmĂ€Ăig auf alle Schlachtfelder auf." (Autorenreferat
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