A polymerizable photosensitizer and its photopolymerization kinetics

A previously reported polymerizable benzophenone photosensitizer, 2‐methacryloxyethyl 4‐benzoylbenzoate (MEBB), was synthesized and characterized. The photopolymerization kinetics of methyl α‐hydroxymethylacrylate (MHMA) and 1,6‐hexanediol diacrylate (HDDA) initiated with MEBB or benzophenone (BP) in the presence or absence of amine co‐initiators were determined by photo‐differential scanning calorimetry. The results indicate that benzophenone with a p‐carbonyl substitutent is more efficient in photoinitiation when compared to the non‐substituted benzophenone analogue. The final monomer conversions in the presence of amine co‐initiators are slightly higher than without them. Copyright © 2005 Society of Chemical Industry     

Synthesis and photopolymerizations of phosphate-containing acrylate/(di)methacrylate monomers from 3-(acryloyloxy)-2-hydroxypropyl methacrylate

Summary Novel phosphorus-containing acrylate/(di)methacrylate monomers based on 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) were prepared by two different methods. The first method involved reaction of AHM with diethylchlorophosphate to produce a phosphate-containing acrylate/methacrylate monomer followed by Michael addition of this monomer with dihexyl amine. In the second method, a hydroxyl-containing dimethacrylate monomer was prepared via Michael addition of hydroxyl amine to AHM followed by its reaction with diethylchlorophosphate. The photopolymerization kinetics of the synthesized monomers were investigated using a differential scanning calorimeter. It was shown that changing the monomer structure allows control of polymerization reactivity and new phosphorus-containing polymers can be obtained.     

频域数字脉冲压缩系统有限字长效应分析

本文提出了采用数字信号处理（ Ｄ Ｓ Ｐ） 芯片 Ｔ Ｍ Ｓ３２０ Ｃ６２ｘ 实现线性调频（ Ｃｈｉｒｐ） 信号频域数字脉冲压缩（ Ｄ Ｐ Ｃ） 的方案．针对 Ｔ Ｍ Ｓ３２０ Ｃ６２ｘ 运算字长较短的问题,研究了有限字长效应的影响;对原码截断算法的字长误差进行了理论分析;并对原码、补码格式下定点截断和定点舍入算法的有限字长效应进行了仿真分析;讨论了输入噪声对字长误差的影响;并给出了一种解决有限字长效应的方案．     

Tandem repeats of Sushi3 peptide with enhanced LPS-binding and -neutralizing activities

Endotoxin, also known as lipopolysaccharide (LPS), is the majormediator of septic shock due to Gram-negative bacterial infection.Chemically synthesized S3 peptide, derived from Sushi3 domainof Factor C, which is the endotoxin-sensitive serine proteaseof the limulus coagulation cascade, was previously shown tobind and neutralize LPS activity. For large-scale productionof this peptide and to mimick other pathogen-recognizing molecules,tandem multimers of the S3 gene were constructed and expressedin Escherichia coli. The recombinant tetramer of S3 (rS3-4mer)was purified by anion exchange and digested into monomers (rS3-1mer).Both the rS3-4mer and rS3-1mer were functionally analyzed fortheir ability to bind LPS by an ELISA-based method and surfaceplasmon resonance. The LAL inhibition and TNF-release test showedthat rS3-1 mer can neutralize the LPS activity as effectivelyas the synthetic S3 peptide, while rS3-4mer displays an enhancedinhibitory effect on LPS-induced activities. Both recombinantpeptides exhibited low cytotoxicity and no haemolytic activityon human cells. This evidence suggests that the recombinantsushi peptides have potential use for the detection, removalof endotoxin and/or anti-endotoxin strategies. Received September 5, 2002; revised June 18, 2003; accepted June 20, 2003.     

Analysis of cladding-mode couplings for a lensed fiber integrated with a long-period fiber grating by use of the beam-propagation method

The beam-propagation method (BPM) is employed to analyze the coupling behavior of our scheme proposed previously, which combines a lensed fiber and a long-period fiber grating (LPFG) [Chen and Wang, Appl. Opt. 39,4490-4500 (2000)]. The influences of a core within the fiber lens are investigated. As for the fiber dependence of our coupling scheme, two typical fibers are studied: dispersion-shifted and single-mode, step-index fibers. With the BPM, the optimal coupling efficiencies for various source waists with corresponding lens radii and working distances are determined. We also compare the results with those obtained by use of the ABCD method and found that the BPM gives better agreement with experimental results.     

Design of binary long-period fiber grating filters by the inverse-scattering method with genetic algorithm optimization

An approach is presented to the design of binary long-period fiber grating (LPFG) filters based on the Gel'fand-Levitan-Marchenko (GLM) inverse-scattering method and genetic algorithm optimization. The nonuniform coupling strength of the binary grating can be realized by varying the local duty ratio. A coupled-mode theory combined with the Poisson sum formula for treating the binary index perturbation is developed for the application of the GLM synthesis method. Since the coupled-mode theory, which smears out the discrete coupling nature, can be regarded only as an approximation to the modeling of a binary LPFG, we use instead the transfer-matrix model to analyze the coupling behavior of a nonuniform binary LPFG. Based on the synthesized grating patterns from the GLM method, a real-coded genetic algorithm with the transfer-matrix model is used to compensate for the discrepancies resulting from use of the coupled-mode theory and to optimize the design. We exemplify the above procedure by designing a flatband LPFG filter and a high-visibility all-fiber Mach-Zehnder filter.     

Distributed construction of low-interference spanners

We propose a new low-interference topology for wireless ad hoc networks modeled by Quasi Unit Disk Graphs. Our topology combines two existing structures, the relaxed Greedy structure developed by Damian, Pandit and Pemmaraju, and the low-interference structure developed by Burkhart, von Rickenbach, Wattenhofer and Zollinger. Our main contribution is showing that, when applied on a QUDG G = (V, E), this new structure inherits most properties of the two underlying structures: (i) it is a t(1 + ε) spanner of G, for any t > 1 and ε > 0, (ii) it has optimal interference among all t-spanners for G, (iii) it has O(1) maximum degree, (iv) its total weight is within a factor of O(log Δ) of the weight of a minimum spanning tree for V, where Δ is the aspect ratio of G, and (v) it can be implemented efficiently in O(log Δ + log^* n) rounds of communication. This work was supported by NSF grant CCF-0728909. A preliminary version of this paper, titled “Distributed construction of bounded-degree low-interference spanners of low weight”, appeared in MobiHoc’08.     

Improved sensor network lifetime with multiple mobile sinks

A critical issue for data gathering in wireless sensor networks is the formation of energy holes near the sinks. Sensors near the sinks have to participate in relaying data on behalf of other sensors and thus will deplete their energy very quickly, resulting in network partitioning and limitation of the network lifetime. The solution that we propose in this paper is to use mobile sinks that change their location when the nearby sensors’ energy becomes low. In this way the sensors located near sinks change over time. In deciding a new location, a sink searches for zones with richer sensor energy.First, we study the improvement in network lifetime when sinks move on a predetermined path, along the perimeter of a hexagonal tiling. Two cases are considered for data gathering when sinks stop in the hexagon’s corners and when the sinks stop on multiple locations on the hexagon perimeter. This study shows an improvement of up to 4.86 times in network lifetime. Second, we design a distributed and localized algorithm used by the sinks to decide their next movement location such that the virtual backbone formed by the sinks remains interconnected at all times. Two extensions of the distributed algorithm, coverage requirement and limitation of the time-delivery requirement, are also addressed. Simulation results are presented to verify our approaches.     

Segmentation and labeling of face images for electronic documents

Face image segmentation and labeling is required in several quality tests which a face image has to pass in order to be included into an electronic ID document. The complexity of such a problem depends on the complexity of the scene, but in general there are no restrictions to the scene. The procedure that we have developed segments a face image into five regions: skin, hair, shoulders, background and padding frame. The presented method consists of two main steps: oversegmentation and labeling. In the first step, the image is segmented into homogeneous regions, whereas in the second step, the labeling of the homogeneous regions is performed. In the course of our research we experimented with several methods for the two described steps, and in this paper we present a setup in which the oversegmentation is performed using the mean-shift segmentation, and labeling is performed using the AdaBoost classification algorithm. Such setup has produced the best results in our experiments which we also present herein.