Modelling the bioelectric behaviour of halo pin-patient structures during magnetic resonance imaging

Bioelectric compatibility of electrically conductive halo fixation devices and magnetic resonance (MR) imaging has been largely based on resulting image quality. Previous studies have focused primarily on improving image quality and, although the electrical characteristics of the system during imaging may have been noted, they have not been studied in depth. Utilizing both a theoretical and experimental approximation, this study focuses on the bioelectric characteristics of the pin-patient structures typically enountered in clinical halo fixation systems. Results indicate that the halo pin-patient system can be modelled using a resistor-inductor-capacitor circuit and that simple attempts at improving compatibility through increasing interface resistance by the use of insulated pins may not be an effective approach to improving halo instrumentation compatibility with new, stronger magnetic and higher-frequency resonance imaging systems.     

Do It Yourself Haptics: Part II

This article is the second of a two-part series intended to be an introduction to haptic interfaces, their construction, and application design. Haptic interactions employ mechanical, programmed physical devices that can be used for human-computer communication via the sense of touch. In Part I of this series, we focused on the devices themselves: the classes of hardware schemes currently available or envisioned, the software components that drive them, and specific examples that can be built on the kitchen table. Here in Part II, we broach a topic that is coming into its own; between the vision of a particular utility that haptic feedback theoretically should enable and the hardware capable of delivering the required sensations is the problem of designing the interaction in a usable way.     

The use of ceramic onlays for restoring the occlusal surface of the teeth

Computer-aided milling of ceramic insertions helped more effectively repair the masticatory surface of teeth, minimize the incidence of errors, rule out the laboratory stage of making the insertions and the technological errors made at this stage, retain physical and mechanical characteristics of ceramics, optimize marginal adherence of the insertion to the tooth, retain the height of the lower part of the face, and thus prevent the maxillodental dysfunction.     

镀锌焊接钢丝网水泥在一种模拟海洋环境中的疲劳特性

使正常养护２８ｄ的７０个镀锌焊接钢丝网水泥试件持续受弯，最外层钢丝的计算应力达到腐蚀下容许值２０７Ｎ／ｍｍ＾２，再放入自制的以７０℃干燥６０ｍｉｎ和４３℃，３．５％ＮａＣｌ溶液浸渍３０ｍｉｎ为一周期的忆速模拟海洋环境实验系统中，分别承受荷载－腐蚀共同作用１、３、７和１８个月（４８０￣８６４０个周期），再对这些试件进行弯曲疲劳－腐蚀试验。分析评估了影响钢丝网水泥抗荷载－腐蚀性能的因素，给出了破坏概率     

A longitudinal investigation of anxiety sensitivity in adolescence.

This investigation sought to expand existing knowledge of anxiety sensitivity in a sample of high school students (N = 2,365) assessed over 4 years. The stability of anxiety sensitivity levels across assessment periods was examined, and cluster analyses were used to identify different developmental pathways in levels of anxiety sensitivity. Groups of adolescents with stable low, stable high, and escalating anxiety sensitivity levels were identified. Adolescents with stable high or escalating anxiety sensitivity were significantly more likely to report experiencing a panic attack than individuals with stable low anxiety sensitivity. Results also indicated that Asian and Hispanic adolescents tended to report higher anxiety sensitivity but that their anxiety sensitivity was less strongly associated with panic than that of Caucasian adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The computer modelling and the chemical kinetics of the rate of cure of epoxy resins

Conclusions  The combined techniques of radiolabelling and computer simulation provide a powerful way of monitoring the actual mechanisms and reactivity of epoxy cure. The information obtained from this treatment allows the understanding of the structure:activity relationships in epoxy cure reactions and permits the design of curing agents with improved or decreased reactivity. A decreased reactivity would be useful for improving the shelf-life of the resin. A decreased k₂ would lead to materials with good tack and drape properties. The potential for controllable B-staging is also evident in such a system with a reduced k₂.     

Outage probability analysis for superposition coded symmetric relaying

Superposition coded symmetric relaying is a bandwidth-efficient cooperative scheme where each source node simultaneously transmits both its own "local" packet and "relay" packet that originated at its partner by adding the modulated local and relay signals in Euclidean space. This paper investigates the power allocation and outage probability of a superposition coded symmetric relaying system with finite-constellation signaling. We first derive the mutual information (MI) metrics for the system. The derived MI metrics consist of two parts: one represents the MI conveyed by the modulated signal corresponding to its own data, and the other represents the MI conveyed by the modulated signal corresponding to its partner’s data. Using MI based effective signal-to-noise ratio mapping technique, we attain expressions for the outage probability. Furthermore, we discuss power allocation policies that minimize the outage probability. Simulation results are presented to verify the correctness of the outage probability analysis and the benefits of the power allocation.     

Nondestructive examination of epoxy adhesive-bonded structures exposed to a humid environment: A comparison of low- and high-frequency dielectric measurements

Broadband dielectric measurements (10 ?2 to 3 GHz) are reported on the effects of exposure of thick film adhesive-bonded structures to moisture. Measurement of the dielectric properties over a broad frequency range allows identification of water both in voids and as a molecular dispersion in the matrix. Changes in the low frequency region of the dielectric spectrum can be attributed to a combination of processes associated with plasticisation of the adhesive, interfacial polarisation effects, and hydration of the surface oxide layer. The data obtained are complemented by mechanical testing and failure analysis of the bond structure measured as a function of the time of exposure. This study indicates that for thick film adhesives the ageing characteristics are apparently independent of the surface treatment. In one of the joints studied an additional feature is identified which appears to correlate with the premature aging of the joint structure.