An infobutton for Web 2.0 clinical discussions: the knowledge linkage framework

This paper aims to develop an infobutton to automatically retrieve published papers corresponding to a topic-specific online clinical discussion. The knowledge linkages infobutton is designed to supplement online clinical conversations with pertinent medical literature from Pubmed. The project involves three distinct steps: 1) Clinical messages around a specific problem are grouped together into a thread. 2) These threads are processed using Metamap to link the conversations to keywords from the MeSH lexicon. 3) These keywords are used in a novel search strategy to retrieve a set of papers from Pubmed, which are then returned to the user. A pilot study using the messages from 2007 and 2008, was conducted to compare the knowledge linkage search strategy to a vector space model and extended Boolean model. The knowledge linkage model proved to be significantly better in terms of precision ( p = 0.013 and 0.003, respectively) and recall ( p = 0.351 and 0.013). Pertinent papers were returned to over 55% of the threads. This approach has demonstrated how clinicians can supplement their peer communications with evidence based research. Future work should focus on how to improve the threading and keyword-mapping strategies.     

Secure sensors data acquisition and communication protection in eHealthcare: Review on the state of the art

Recent advances in hardware technology have led to the development of low cost, power efficient and more feature rich devices that are amongst the most critical parts of communication networks. These devices or sensors can now sense data with more accuracy, process it by themselves and send it to the neighboring node or the sink node. However, robust and reliable security mechanisms are not yet properly implemented on these sensors due to their limited energy and computation power. Sensors also play a very important role in eHealthcare systems where ubiquitous patient monitoring is performed. As data is generated from the sensor nodes, reliable, secure and attack-resistant data acquisition and transmission is important for an efficient eHealthcare systems. This survey focuses on security issues of sensors data acquisition and transmission protocols, describing their main security features and comparing them in the context of a secure eHealthcare system. A taxonomy of open issues and future challenges is also discussed with respect to specific security metrics described in the paper.     

Superradiant Emission from Coherent Excitons in van Der Waals Heterostructures

Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability.     

Understanding the Time and Frequency Varying Characteristics of a Multipath Wireless Channel

Designing a spectrally efficient wireless channel requires a comprehensive understanding of its time and frequency varying characteristics, making it a stochastic medium of communication. These characteristics become more challenging to cater at the receiving terminal in a multipath transmission. This is because of the fading effect and Doppler shift of the transmitted frequency, specifically in cellular mobile radio systems and vehicle to vehicle communications. This paper presents the modeling, simulation, and then characterization of a cellular mobile radio multipath channel over its time and frequency varying fading gain. For this purpose, a discrete-time Finite Impulse Response (FIR) type filter of such a channel is designed, modeled, and simulated using time and frequency varying characteristics of the received signal. The simulated channel response is further analyzed in terms of coherence bandwidth, coherence time, delay spread, Doppler spread, and symbol time.

     

Throughput-efficient coalition formation of selfish/altruistic nodes in ad hoc networks: a hedonic game approach

In this paper, we analyze the problem of throughput-efficient distributed coalition formation (CF) of selfish/altruistic nodes in ad hoc radio networks. We formulate the problem as a hedonic CF game with non-transferable utility and propose different preference relations (CF rules) based on individual/group rate improvement of distributed nodes. We develop a hedonic CF algorithm, through which distributed nodes may self-organize into stable throughput-efficient disjoint coalitions. We apply the concept of frequency reuse over different coalitions, such that the members of each coalition will transmit over orthogonal sub-bands with the available spectrum being optimally allocated among them. We study the computational complexity and convergence properties of the proposed hedonic CF algorithm under selfish and altruistic preferences, and present means to guarantee Nash-stability. In addition, we identify the scenarios in which a CF process might lead to instability (CF cycle), and we propose methods to avoid cycles and define different exit procedures if a CF cycle is inevitable. Performance analysis shows that the proposed algorithm with optimal bandwidth allocation provides a substantial gain, in terms of average payoff per link, over existing coalition formation algorithms for a wide SNR range.     

A spherical aberration-corrected 200 kV TEM

A spherical aberration (Cs)-corrected 200 kV TEM was newly developed. The column of the microscope was extended by 25 cm and the inner yoke of the objective lens was modified to insert some parts of the corrector elements. The corrector has two hexapole elements that play a main role in Cs correction and they are placed at a position equivalent to the coma-free point of the objective lens by using two transfer doublet lenses. The Cs correction was successfully carried out by means of the third-order aberration that was generated in the two extended hexapoles. The Cs can be corrected to the desired value and also can be overcompensated in order to produce a negative Cs, as with the corrected Cs of -23 microm shown in this work. The optical system of the corrector does not produce second- and fourth-order aberrations, and can correct residual aberrations up to the third order. All of the corrector elements are computer-controlled and the third-order aberrations are quite stable after they are properly corrected. The resolution of 0.135 nm was experimentally confirmed by the Young's fringe method. Image simulations of a silicon [110] single crystal were made with various Cs and defocus values to demonstrate the effectiveness of arbitral control of Cs.     

On the synergy between electrical and photonic switching

This article focuses on the values of electrical switching vs. photonic switching in the context of telecom transport networks. In particular, we show that the requirement of providing agility at the optical layer in the face of traffic forecast uncertainties is served better through photonic switching. On the other hand, some of the network-level functions, such as fast protection, subwavelength aggregation, and flexible client connectivity, require electrical switching. We further argue that additional values are achieved with hybrid photonic and electrical switching, which do not exist when either of these options is used in isolation.     

A medium access protocol exploiting multiuser-detection in CDMA ad-hoc networks

A new medium access protocol which exploits the physical layer capability of multiuser detection is proposed to help in improving the throughput/delay performance of ad-hoc networks. When more than one node has packets buffered for a common node in the neighborhood, all such nodes can simultaneously transmit their packets to the common receiver after reserving their surrounding channel. This is achieved in our protocol by extending the (sender-initiated) CSMA/CA collision avoidance framework by the receiver-initiated medium access technique and incorporating the transmission power control. We analyze the improvement in the throughput that can be achieved over the basic sender-initiated collision avoidance protocol in the network. Since the throughput improvement via multi-packet reception is influenced by the network layer activity as well, the performance of our protocol rolls back to that of the basic sender-initiated protocol in case of no coordination from the network layer. For the evaluation of performance of our protocol we simulate ad-hoc networks for different network topologies and traffic configurations. We observe the scheme to be capable in significantly improving the throughput/delay performance of the network.     

Temperature distribution in tissues from a regular array of hotsource implants: an analytical approximation

An approximate analytical model based on the bioheat transfer equation is derived and used to calculate temperature within a perfused region implanted regularly with dielectrically coated hot source implants. The effect of a regular array of mutually parallel heat sources of cylindrical shape is approximated by idealizing one of the boundary conditions. The solution is in terms of modified Bessel functions. In calculating the temperature of each thermoregulating source in the array, the steady state power balance is enforced. The important feature of the model is that the finite size of implant diameter and its dielectric coating can be incorporated. The effect of thickness and thermal conductivity of the coating on the source and tissue temperatures along with various other interesting features are deduced from this model. The analytically calculated implant and tissue temperatures are compared with those of a numerical 3-D finite difference model. The analytical model also is used to define a range of parameters such that minimal therapeutic temperatures will be achieved in the implanted volume without exceeding prescribed maximum temperatures