Tailoring the Molecular Properties with Isomerism Effect of AIEgens

It is challenging to achieve precise control on the properties of organic π‐functional materials to widen their practical applications. On the other hand, the study of aggregation‐induced emission luminogens (AIEgens) helps achieve such goals because of inherent relationships between their luminescence behaviors and conformational variations that allow for the visual monitoring of the changes in the material properties. Inspired by this, in this work, three AIE isomers are fabricated in structures consisting of tetraphenylpyrazine and triphenylethene units with para‐, meta‐, and ortho‐position linkages, respectively. The isomerism effect brings about significantly decreased luminescence efficiency, subtly blueshifted emission, basically reduced AIE effect but boosted porosity in the aggregate state as the conformation of AIEgens evolves from an extended to a folded one. Based on the distinct properties, their respective use in blue organic light‐emitting diodes, nanofluorescent probes, and molecule‐capturing porous crystals are investigated. This work not only achieves precise property control by using the isomerism effect of AIEgens but also provides useful information on the future design of π‐conjugated materials with advanced functionalities.     

Characterization and exploitation of heterogeneous OFDM primary users in cognitive radio networks

The fundamental features of cognitive radio (CR) systems are their ability to adapt to the wireless environment where they operate and their opportunistic occupation of the licensed spectrum bands assigned to the primary network. CR users in CR systems should not cause any interference to primary users (PUs) of the primary network. For this purpose, CR users need to accurately estimate the features and activities of the primary users. In this paper, a novel characterization of heterogeneous PUs and a novel reconfigurability solution in CR networks are introduced. The characterization of PUs consists of a detector and classifier that distinguishes between heterogenous PUs. The PU characteristics stored in radio environmental maps are utilized by an interference/throughput adapter for the optimization of CR parameters. The performance of the proposed solutions is evaluated by showing false alarm and missed detection probabilities of the detector/classifier in a multipath fading channel with additive white Gaussian noise. Moreover, the impact of the PU characteristics on the CR throughput is analyzed.     

Morphological Stabilization by Supramolecular Perfluorophenyl‐C60 Interactions Leading to Efficient and Thermally Stable Organic Photovoltaics

A new PC₆₁BM‐based fullerene, [6,6]‐phenyl‐C₆₁ butyric acid pentafluorophenyl ester (PC₆₁BP^F) is designed and synthesized. This new n‐type material can replace PC₆₁BM to form a P3HT:PC₆₁BP^F binary blend or serve as an additive to form a P3HT:PC₆₁BM:PC₆₁BP^F ternary blend. Supramolecular attraction between the pentafluorophenyl group of PC₆₁BP^F and the C₆₀ cores of PC₆₁BP^F/PC₆₁BM can effectively suppress the PC₆₁BP^F/PC₆₁BM materials from severe aggregation. By doping only 8.3 wt% PC₆₁BP^F, device PC₆₁BP^F651 exhibits a PCE of 3.88% and decreases slightly to 3.68% after heating for 25 h, preserving 95% of its original value. When PC₆₁BP with non‐fluorinated phenyl group is used to substitute PC₆₁BP^F, the stabilizing ability disappears completely. The efficiencies of PC₆₁BP651 and PC₆₁BP321 devices significantly decay to 0.44% and 0.11%, respectively, after 25 h isothermal heating. Most significantly, this strategy is demonstrated to be effective for a blend system incorporating a low band‐gap polymer. By adding only 10 wt% PC₆₁BP^F, the PDTBCDTB: PC₇₁BM‐based device exhibits thermally stable morphology and device characteristics. These findings demonstrate that smart utilization of supramolecular interactions is an effective and practical strategy to control morphological evolution.     

Facile Generation of L10‐FePt Nanodot Arrays from a Nanopatterned Metallopolymer Blend of Iron and Platinum Homopolymers

Hard ferromagnetic (L1₀ phase) FePt alloy nanoparticles (NPs) with extremely high magnetocrystalline anisotropy are considered to be one of the most promising candidates for the next generation of ultrahigh‐density data storage system. The question of how to generate ordered patterns of L1₀‐FePt NPs and how to transform the technology for practical applications represents a key current challenge. Here the direct synthesis of L1₀ phase FePt NPs by pyrolysis of Fe‐containing and Pt‐containing metallopolymer blend without post‐annealing treatment is reported. Rapid single‐step fabrication of large‐area nanodot arrays (periodicity of 500 nm) of L1₀‐ordered FePt NPs can also be achieved by employing the metallopolymer blend, which possesses excellent solubility in most organic solvents and good solution processability, as the precursor through nanoimprint lithography (NIL). Magnetic force microscopy (MFM) imaging of the nanodot pattern indicates that the patterned L1₀ phase FePt NPs are capable of exhibiting decent magnetic response, which suggests a great potential to be utilized directly in the fabrication of bit patterned media (BPM) for the next generation of magnetic recording technology.     

Enzymatic Writing to Soft Films: Potential to Filter,Store, and Analyze Biologically Relevant Chemical Information

Sensor‐based chemical analyses commonly enlist either the molecular recognition capabilities of biology (e.g., enzyme biosensors) or advanced information processing algorithms (e.g., the electronic nose). Here, a hybrid approach is proposed in which an enzyme is used to “filter” chemical information and write this information to a film which then serves as a permanent storage medium that can be ‘read’ repeatedly, interactively, and by multiple sensor modalities. This approach is demonstrated by analyzing common dietary phenols that are reported to offer health benefits. Specifically, the enzyme tyrosinase is used to convert these phenols into reactive quinones that graft (i.e., write) to a chitosan film. Grafting can be detected by optical, mechanical, and electrochemical sensors. Importantly, grafting confers redox activity to the films and this redox activity can be probed interactively by advanced electrochemical methods that allow the intrinsic redox reactivities to be compared, redox interactions to be identified, and biologically relevant redox activities to be examined. The transfer of chemical and biological information to a film is envisioned to provide broader access to the extensive capabilities offered by sensor technologies and signal processing methodologies.     

Fabricating Strong and Stiff Bioplastics from Whole Spirulina Cells

Since the 1950s, 8.3 billion tonnes (Bt) of virgin plastics have been produced, of which around 5 Bt have accumulated as waste in oceans and other natural environments, posing severe threats to entire ecosystems. The need for sustainable bio-based alternatives to traditional petroleum-derived plastics is evident. Bioplastics produced from unprocessed biological materials have thus far suffered from heterogeneous and non-cohesive morphologies, which lead to weak mechanical properties and lack of processability, hindering their industrial integration. Here, a fast, simple, and scalable process is presented to transform raw microalgae into a self-bonded, recyclable, and backyard-compostable bioplastic with attractive mechanical properties surpassing those of other biobased plastics such as thermoplastic starch. Upon hot-pressing, the abundant and photosynthetic algae spirulina forms cohesive bioplastics with flexural modulus and strength in the range 3–5 GPa and 25.5–57 MPa, respectively, depending on pre-processing conditions and the addition of nanofillers. The machinability of these bioplastics, along with self-extinguishing properties, make them promising candidates for consumer plastics. Mechanical recycling and fast biodegradation in soil are demonstrated as end-of-life options. Finally, the environmental impacts are discussed in terms of global warming potential, highlighting the benefits of using a carbon-negative feedstock such as spirulina to fabricate plastics.     

Bit error rate evaluation of linear equalization in FWA systems

The bit error rate performance of broadband wireless fixed access (FWA) systems over multipath fading channels is investigated in this paper. Linear MMSE equalization is examined theoretically for 16‐QAM and QPSK modulated FWA systems and shown to yield unsatisfactory performance. The theoretical analysis is validated by Monte‐Carlo simulations and proved to be reasonably accurate. It provides us an insight into the physical limitations imposed by the FWA channels and suggest solutions to improve the capacity and performance of future FWA systems. Copyright © 2006 John Wiley & Sons, Ltd.     

高级触摸感应技术普遍应用于玩家界面

正现在,消费性电子产品(最早是MP3播放器,现在则是智能手机、电子阅读器和平板电脑)上复杂精致的触摸屏互动应用日渐受到人们的青睐;它能使游戏机更加现代化,能吸引更年轻、更热衷高端技术的玩家。它能让玩家享受一系列功能和操作上的优势,同时使得开发商能够提供与其竞争对手截然不同的产品类型,在     

Selection criteria for the analysis of data-driven clusters in cerebral FMRI

Functional MRI (fMRI) may be possible without a priori models of the cerebral hemodynamic response. First, such data-driven fMRI requires that all cerebral territories with distinct patterns be identified. Second, a systematic selection method is necessary to prevent the subjective interpretation of the identified territories. This paper addresses the second point by proposing a novel method for the automated interpretation of identified territories in data-driven fMRI. Selection criteria are formulated using: 1) the temporal cross-correlation between each identified territory and the paradigm and 2) the spatial contiguity of the corresponding voxel map. Ten event-design fMRI data sets are analyzed with one prominent algorithm, fuzzy c-means clustering, before applying the selection criteria. For comparison, these data are also analyzed with an established, model-based method: statistical parametric mapping. Both methods produced similar results and identified potential activation in the expected territory of the sensorimotor cortex in all ten data sets. Moreover, the proposed method classified distinct territories in separate clusters. Selected clusters have a mean temporal correlation coefficient of 0.39+/-0.07 (n=19) with a mean 2.7+/-1.4 second response delay. At most, four separate contiguous territories were observed in 87% of these clusters. These results suggest that the proposed method may be effective for exploratory fMRI studies where the hemodynamic response is perturbed during cerebrovascular disease.     

In-Plane Coupling of Light From InP-Based Photonic Crystal Band-Edge Lasers Into Single-Mode Waveguides

In this paper, we analyze the coupling of light from photonic-crystal band-edge lasers into single-mode waveguides. Both active and passive devices lie in the same plane and coupling of light is achieved by using parabolic and nanotapers in InP based epitaxial structures. Two- and three-dimensional finite-difference time-domain methods are employed to analyze these devices. Coupling efficiencies higher than 80% can be obtained with parabolic couplers. We also present laser configurations that can reduce multiwavelength coupling of light into single-mode waveguides, using structures that are similar to coupled cavity Fabry-Peacuterot lasers