EquiCast: Scalable multicast with selfish users

Peer-to-peer (P2P) networks suffer from the problem of “freeloaders”, i.e., users who consume resources without contributing anything in return. In this paper, we tackle this problem taking a game theoretic perspective by modeling the system as a non-cooperative game. We introduce EquiCast, a wide-area P2P multicast protocol for large groups of selfish nodes. EquiCast is the first P2P multicast protocol that is formally proven to enforce cooperation in selfish environments. Additionally, we prove that EquiCast incurs a low constant load on each user.     

Agenda-based regulation of study-time allocation: When agendas override item-based monitoring.

Theories of self-regulated study assume that learners monitor item difficulty when making decisions about which items to select for study. To complement such theories, the authors propose an agenda-based regulation (ABR) model in which learners’ study decisions are guided by an agenda that learners develop to prioritize items for study, given their goals and task constraints. Across 4 experiments, the authors orthogonally manipulated 1 task constraint—the reward structure of the task—with objective item difficulty, so that learners could use either item difficulty or potential reward in deciding how to allocate their study time. Learners studied items, were tested, and then selected half the items for restudy. As predicted by the ABR model, reward structure drove item selection more than did item difficulty, which demonstrates learners’ agendas can override the effects of monitoring item difficulty in the allocation of study time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Configuration of inter-office switch for extreme traffic with zone configuration evaluator diagram

The problem addressed by this paper is to enable a manufacturer's representative to configure an inter-office switch with a balance of desirable functionality and measured performance under several potential extremes of traffic. The zone-configuration evaluator diagram (ZCED), a decision aid that generates the tradeoffs among different configurations, is developed to enable the switch manufacturer to forego the past practice of guaranteeing absolute performance to all of its diverse customers. This guarantee was achieved in the past by the manufacturer supporting a single conservative configuration only. The ZCED simultaneously characterizes (i) customer needs in three regimes: safety-critical, business-critical, or non-critical; (ii) extremes of traffic in terms of non-peak, average, peak, and peak–peak scenarios; and (iii) measurable performance in terms of frequency of lost transactions. Thus, a manufacturer's representative selects a configuration appropriate to the customer's individual needs and the manufacturer achieves higher revenue on the sale of desirable functions and features. A demonstration of the ZCED is developed based on a performance simulation of an actual small-office switch. The ZCED concept is readily adaptable to the configuration of other communication devices with diverse customer needs, traffic loads, and optional functionalities.     

Chirality Dependence of Amyloid β Cellular Uptake and a New Mechanistic Perspective

Amyloid β is an inherently disordered peptide that can form diverse neurotoxic aggregates, and its 42-amino-acid isoform is believed to be the agent responsible for Alzheimer's disease (AD). Cellular uptake of the peptide is a pivotal step for it to be able to exert many of its toxic actions. The cellular uptake process is complex, and numerous competing internalization pathways have been proposed. To date, it remains unclear which of the uptake mechanisms are particularly important for the overall process, and improvement of this understanding is needed, so that better molecular AD therapeutics can be designed. Chirality can be used as a unique tool to study this process, because some of the proposed mechanisms are expected to proceed in stereoselective fashion, whereas others are not. To shed light on this important issue, we synthesized fluorescently labeled enantiomers of amyloid β and quantified their cellular uptake, finding that uptake occurs in stereoselective fashion, with a typical preference for the l stereoisomer of ≈5:1. This suggests that the process is predominantly receptor-mediated, with likely minor contributions of non-stereoselective mechanisms.     

Automatic correction of background phase offset in 4D-flow of great vessels and of the heart in MRI using a third-order surface model

Magnetic Resonance Materials in Physics, Biology and Medicine - To evaluate an automatic correction method for velocity offset errors in cardiac 4D-flow acquisitions. Velocity offset correction was...     

How to construct constant-round zero-knowledge proof systems for NP

Constant-round zero-knowledge proof systems for every language in are presented, assuming the existence of a collection of claw-free functions. In particular, it follows that such proof systems exist assuming the intractability of either the Discrete Logarithm Problem or the Factoring Problem for Blum integers.     

Close-packed noncircular nanodevice pattern generation by self-limiting ion-mill process

We describe a self-limiting, low-energy argon-ion-milling process that enables noncircular device patterns, such as squares or hexagons, to be formed using precursor arrays of uniform circular openings in poly(methyl methacrylate) defined using electron beam lithography. The proposed patterning technique is of particular interest for bit-patterned magnetic recording medium fabrication, where square magnetic bits result in improved recording system performance. Bit-patterned magnetic medium is among the primary candidates for the next generation magnetic recording technologies and is expected to extend the areal bit density limits far beyond 1 Tbit/in(2). The proposed patterning technology can be applied either for direct medium prototyping or for manufacturing of nanoimprint lithography templates or ion beam lithography stencil masks that can be utilized in mass production.     

Nucleosome conformational flexibility and implications for chromatin dynamics

The active role of chromatin in the regulation of gene activity seems to imply a conformational flexibility of the basic chromatin structural unit, the nucleosome. This review is devoted to our recent results pertaining to this subject, using an original approach based on the topology of single particles reconstituted on DNA minicircles, combined with their theoretical simulation. Three types of chromatin particles have been studied so far: a subnucleosome, that is, the (H3-H4)(2) histone tetramer-containing particle, now known as the tetrasome; the nucleosome; and the linker histone H5/H1-bearing nucleosome (the chromatosome). All the particles were found to exist in two to three conformational states, which differ by their topological and mechanical properties. Our approach unveiled the molecular mechanisms of nucleosome conformational dynamics and will help to understand its functional relevance. A most surprising conclusion of the work was perhaps that DNA overall flexibility increases considerably upon particle formation, which might indeed be a requirement of genome function.     

Thermally Activated Photoluminescence in Lead Selenide Colloidal Quantum Dots

The thermal activation processes in PbSe colloidal quantum dots and their influence on the ground‐state exciton emission are discussed. Activation of a dark exciton occurs at 1.4–7 K, assisted by an acoustic phonon coupling. Activation of a bright exciton occurs at 100–200 K, which appears as a sudden change in the photoluminescence band intensity, energy, and full width at half maximum. This activation overcomes the dark–bright‐state splitting, when the activation temperature increases with the decrease of the dots' size. The dark exciton lifetime is found to be ≈6–12 µs at 1.4 K, while the bright exciton lifetime at 300 K evaluated as 450 ns varies slightly with the change in the size of the dots. In addition, the emission quantum yield of these dots, measured at a variety of temperatures when dissolved in various solvents, reveals information about the influence of the environment on the recombination processes.     

Adapting content for wireless Web services

Motorola Labs' Web-enabled museum system demonstrates how context-aware wireless Web services can adapt their content to a user's dynamic context.