Stochastic dynamics of adhesion clusters under shared constant force and with rebinding

Single receptor-ligand bonds have finite lifetimes, so that biological systems can dynamically react to changes in their environment. In cell adhesion, adhesion bonds usually act cooperatively in adhesion clusters. Outside the cellular context, adhesion clusters can be probed quantitatively by attaching receptors and ligands to opposing surfaces. Here we present a detailed theoretical analysis of the stochastic dynamics of a cluster of parallel bonds under shared constant loading and with rebinding. Analytical solutions for the appropriate one-step master equation are presented for special cases, while the general case is treated with exact stochastic simulations. If the completely dissociated state is modeled as an absorbing boundary, mean cluster lifetime is finite and can be calculated exactly. We also present a detailed analysis of fluctuation effects and discuss various approximations to the full stochastic description.Comment: Revtex, 29 pages, 23 postscript figures included (some with reduced image quality

Nuclear shadowing and in-medium properties of the rho^0

We explain the early onset of shadowing in nuclear photoabsorption within a multiple scattering approach and discuss its relation to in-medium modifications of the rho^0.Comment: 4 pages, 2 figures, to appear in the proceedings of the 9th International Conference on the Structure of Baryons, Newport News, VA, USA, 3-8 Mar 200

Coronal Mass Ejections Associated with Slow Long Duration Flares

It is well known that there is temporal relationship between coronal mass ejections (CMEs) and associated flares. The duration of the acceleration phase is related to the duration of the rise phase of a flare. We investigate CMEs associated with slow long duration events (LDEs), i.e. flares with the long rising phase. We determined the relationships between flares and CMEs and analyzed the CME kinematics in detail. The parameters of the flares (GOES flux, duration of the rising phase) show strong correlations with the CME parameters (velocity, acceleration during main acceleration phase and duration of the CME acceleration phase). These correlations confirm the strong relation between slow LDEs and CMEs. We also analyzed the relation between the parameters of the CMEs, i.e. a velocity, an acceleration during the main acceleration phase, a duration of the acceleration phase, and a height of a CME at the end of the acceleration phase. The CMEs associated with the slow LDEs are characterized by high velocity during the propagation phase, with the median equal 1423 km/s. In half of the analyzed cases, the main acceleration was low (a<300 m/s^2), which suggests that the high velocity is caused by the prolongated acceleration phase (the median for the duration of the acceleration phase is equal 90 minutes). The CMEs were accelerated up to several solar radii (with the median 7 Rsun), which is much higher than in typical impulsive CMEs. Therefore, slow LDEs may potentially precede extremely strong geomagnetic storms. The analysis of slow LDEs and associated CMEs may give important information for developing more accurate space weather forecasts, especially for extreme events.Comment: Solar Physics, accepte

Aggregating Dependency Graphs into Voting Agendas in Multi-Issue Elections

Many collective decision making problems have a combinatorial structure: the agents involved must decide on multiple issues and their preferences over one issue may depend on the choices adopted for some of the others. Voting is an attractive method for making collective decisions, but conducting a multi-issue election is challenging. On the one hand, requiring agents to vote by expressing their preferences over all combinations of issues is computationally infeasible; on the other, decomposing the problem into several elections on smaller sets of issues can lead to paradoxical outcomes. Any pragmatic method for running a multi-issue election will have to balance these two concerns. We identify and analyse the problem of generating an agenda for a given election, specifying which issues to vote on together in local elections and in which order to schedule those local elections

Coupled plasmon - phonon excitations in extrinsic monolayer graphene

The existence of an acoustic plasmon in extrinsic (doped or gated) monolayer graphene was found recently in an {\it ab initio} calculation with the frozen lattice [M. Pisarra {\it et al.}, arXiv:1306.6273, 2013]. By the {\em fully dynamic} density-functional perturbation theory approach, we demonstrate a strong coupling of the acoustic plasmonic mode to lattice vibrations. Thereby, the acoustic plasmon in graphene does not exist as an isolated excitation, but it is rather bound into a combined plasmon-phonon mode. We show that the coupling provides a mechanism for the {\em bidirectional} energy exchange between the electronic and the ionic subsystems with fundamentally, as well as practically, important implications for the lattice cooling and heating by electrons in graphene.Comment: 5 pages, 4 figure

Microbial Profiles of Hands, Foods, Easy Contact Surfaces and Food Contact Surfaces: A Case Study of a University Campus

Human hands usually harbour microbes both as part of body normal flora as well as transient microbes acquired from the environment. One common way by which transient organisms of hand are picked up is by contact with food and surfaces. A total of 130 samples consisting of 40 hand swabs, 20 each of food samples and food contact surfaces and 10 each of swabs from banisters, table top, door handles, taps handles and toilet flushers were collected from different locations of the University campus. Samples were analyzed for total aerobic plate count, fungal count, coliform count and for specific organisms. About 98% of hand swabs, food contact and the easy contact surfaces were contaminated with diverse organisms. Hand swabs from the halls of residence and Library had higher levels of contaminations 2.1x105 and 1.9x105 cfu respectively. Toilet flushers and Banisters had TAPC of 8.3x106 and 4.8x106. Moin-moin, Fried rice and Coleslaw had counts of 3.2x107, 1.6x106 and 1.1x106 cfu/g. The predominant microorganisms isolated were Bacillus spp., Staphylococcus spp., Streptococcus spp., Aspergillus spp., Fusarium spp., Penicillium spp. and Actinomycetes. Also present in the food samples and contact surfaces are Klebsiella spp., Escherichia coli and Salmonella spp. Different types of organisms can be picked up from the environment specifically the easy contact surfaces and the hand can be the most important means by which enteric pathogens are transmitted. Likewise, the rate of food borne illness can be greatly reduced by effective HACCP, GMP and hand washing

Reply on the ``Comment on `Loss-error compensation in quantum- state measurements' ''

The authors of the Comment [G. M. D'Ariano and C. Macchiavello to be published in Phys. Rev. A, quant-ph/9701009] tried to reestablish a 0.5 efficiency bound for loss compensation in optical homodyne tomography. In our reply we demonstrate that neither does such a rigorous bound exist nor is the bound required for ruling out the state reconstruction of an individual system [G. M. D'Ariano and H. P. Yuen, Phys. Rev. Lett. 76, 2832 (1996)].Comment: LaTex, 2 pages, 1 Figure; to be published in Physical Review