Crumpling of a stiff tethered membrane

first-principles numerical simulation model for crumpling of a stiff tethered membrane is introduced. In our model membranes, wrinkles, ridge formation, ridge collapse, as well as the initiation of stiffness divergence, are observed. The ratio of the amplitude and wave length of the wrinkles, and the scaling exponent of the stiffness divergence, are consistent with both theory and experiment. We observe that close to the stiffness divergence there appears a crossover beyond which the elastic behavior of a tethered membrane becomes similar to that of dry granular media. This suggests that ridge formation in membranes and force-chain network formation in granular packings are different manifestations of a single phenomenon.Comment: For full resolution figures, please send us an emai

The Visibility Of Information Science And Library Science Research In Bibliometric Mapping Of The Lis Field

The relation between information science and library science has been debated for decades, and even attempts at utilizing methods generally acknowledged as robust for the purpose of mapping research fields have yielded results with large variations. The

Multiple changes in gene expression in chronic human Achilles tendinopathy

Atlas™ cDNA cell interaction arrays (CLONTECH) were used to examine degenerate tissue from four patients with Achilles tendon disorders, in order to identify changes in expression of genes important in cell–cell and cell–matrix interactions. The greatest difference between normal (post-mortem) and degenerate tissue samples was in the level of MMP-3 (stromelysin) mRNA, which was down-regulated in all the degenerate samples. Quantitative RT-PCR assay of RNA extracted from paired ‘normal’ and degenerate Achilles tendon tissue samples taken from tendons during surgery mirrored the results of the arrays. Levels of MMP-3 mRNA were lower, whereas levels of type-I and type-III collagen mRNAs were significantly higher, in the degenerate compared to the ‘normal’ samples. Immunoblotting of proteins extracted from the same tendon samples showed that three of four normal tissue samples taken from individuals without apparent tendon disorder had much higher levels of MMP-3 protein than ‘normal’ or degenerate samples from patients with tendinosis. We suggest that MMP-3 may play an important role in the regulation of tendon extracellular matrix degradation and tissue remodelling

Brittle fracture down to femto-Joules - and below

We analyze large sets of energy-release data created by stress-induced brittle fracture in a pure sapphire crystal at close to zero temperature where stochastic fluctuations are minimal. The waiting-time distribution follows that observed for fracture in rock and for earthquakes. Despite strong time correlations of the events and the presence of large-event precursors, simple prediction algorithms only succeed in a very weak probabilistic sense. We also discuss prospects for further cryogenic experiments reaching close to single-bond sensitivity and able to investigate the existence of a transition-stress regime.Comment: REVTeX, new figure added, minor modifications to tex

Dependable Control for Wireless Distributed Control Systems

The use of wireless communications for real-time control applications poses several problems related to the comparatively low reliability of the communication channels. This paper is concerned with adaptive and predictive application-level strategies for ameliorating the effects of packet losses and burst errors in industrial sampled-data Distributed Control Systems (DCSs), which are implemented via one or more wireless and/or wired links, possibly spanning multiple hops. The paper describes an adaptive compensator that reconstructs the best estimates (in a least squares sense) of a sequence of one or more missing sensor node data packets in the controller node. At each sample time, the controller node calculates the current control, and a prediction of future controls to apply over a short time horizon; these controls are forwarded to the actuator node every sample time step. A simple design method for a digital Proportional Integral Derivative (PID)-like adaptive controller is also described for use in the controller node. Together these mechanisms give robustness to packet losses around the control loop; in addition, the majority of the computational overhead resides in the controller node. An implementation of the proposed techniques is applied to a case study using a Hardware in the Loop (HIL) test facility, and favorable results (in terms of both performance and computational overheads) are found when compared to an existing robust control method for a DCS experiencing artificially induced burst errors

Why do people lose their friends after a stroke?

Background: It is well-known that people lose friends after a stroke; what is less well understood is why this occurs. Aims: This study explored why people lose contact with their friends, and whether there are any protective factors. It also examined how friendship loss and change is perceived by the individual. Methods and Procedures: Participants with a first stroke were recruited from one acute stroke unit in the UK. In-depth qualitative interviews took place between 8 and 15 months post stroke. Outcomes and Results: 29 participants were recruited of whom 10 had aphasia. The main reasons given for losing friends were: loss of shared activities, reduced energy levels, physical disability, aphasia, unhelpful responses of others, environmental barriers, and changing social desires. The subset of participants who experienced the most extensive loss of friends were those who described a sense that they were ‘closing in’ on themselves leading to a withdrawal from social contact and a new preference for meeting only close friends and family. Those with aphasia experienced the most hurtful negative responses from others and found it more difficult to retain their friends unless they had strong supportive friendship patterns prior to the stroke. The factors which helped to protect friendships included: having a shared history, friends who showed concern, who lived locally, where the friendship was not activity-based, and where the participant had a ‘friends-based’ social network prior to the stroke. Conclusions and Implications: Given the link between depression and loss of friends post stroke, supporting an individual in maintaining a social network is likely to be beneficial. For intervention to be effective, however, it may need to take into account not only the impact of new physical and language disabilities, but also changing social desires