Resolution and quantification of arginine,monomethylarginine, asymmetric dimethylarginine,and symmetric dimethylarginine in plasma using HPLC with internal calibration

N^G,N^G‐dimethyl‐l ‐arginine (asymmetric dimethylarginine, ADMA),N^G‐monomethyl‐l ‐arginine (l ‐NMMA) and N^G,N^G’‐dimethyl‐l ‐arginine (symmetric dimethylarginine, SDMA) are released during hydrolysis of proteins containing methylated arginine residues. ADMA and l ‐NMMA inhibit nitric oxide synthase by competing with l ‐arginine substrate. All three methylarginine derivatives also inhibit arginine transport. To enable investigation of methylarginines in diseases involving impaired nitric oxide synthesis, we developed a high‐performance liquid chromatography (HPLC) assay to simultaneously quantify arginine, ADMA, l ‐NMMA and SDMA. Our assay requires 12 μL of plasma and is ideal for applications where sample availability is limited. We extracted arginine and methylarginines with mixed‐mode cation‐exchange columns, using synthetic monoethyl‐l ‐arginine as an internal standard. Metabolites were derivatized with ortho‐phthaldialdeyhde and 3‐mercaptopropionic acid, separated by reverse‐phase HPLC and quantified with fluorescence detection. Standard curve linearity was ≥0.9995 for all metabolites. Inter‐day coefficient of variation (CV) values were ≤5% for arginine, ADMA and SDMA in human plasma and for arginine and ADMA in mouse plasma. The CV value for l ‐NMMA was higher in human (10.4%) and mouse (15.8%) plasma because concentrations were substantially lower than ADMA and SDMA. This assay provides unique advantages of small sample volume requirements, excellent separation of target metabolites from contaminants and validation for both human and mouse plasma samples. © 2015 The Authors Biomedical Chromatography published by John Wiley & Sons, Ltd.     

Maximizing the SDMA Mobile Radio Capacity Increase by DOA Sensitive Channel Allocation

In a cellular mobile radio system an SDMA (Space Division Multiple Access) component can be implemented for the reuse of radio channels physically incorporated by time, frequency or code slots. Since SDMA is based on the spatial separation of different users operating in the same channel, a DOA (Direction of arrival) sensitive channel allocation scheme is essential for maximizing system capacity. In this paper we present the Eigenvector method, a computationally efficient algorithm to do this job. We also present simulation results on the Eigenvector method operating in a typical urban mobile radio cell. The simulated blocking probabilities are then used to predict the capacity increase which can be expected after adding an SDMA component to a conventional mobile radio system.     

基于有限反馈的数据流数自适应SDMA

针对目前绝大部分有限反馈自适应SDMA由于使用固定满波束发送策略而导致在稀疏网络中严重的用户间干扰的问题,该文提出了一种基于有限反馈的数据流数自适应SDMA,该方案能通过自适应地选择并行发送波束的数目来达到有效控制用户间干扰的目的。具体实现如下：通过用户的有限反馈信息,以及信道的二阶统计信息,基站端使用约束最大似然估计的方法估计出使用不同数目发送波束的发送模式所支持的最大和吞吐量,从而自适应地选择最优的发送模式。仿真结果表明：该文提出的方案能在增加很少反馈量的前提下显著改善现有SDMA方案的性能。     

A review of recent trends in electrospray ionisation-mass spectrometry for the analysis of metal-organic ligand complexes

Background

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) formation inhibitor, has emerged as a promising biomarker of NO-associated endothelial dysfunction in cardiovascular diseases as well in chronic renal failure. The interest in potentially fundamental role of this metabolite, in basic and clinical research, led to the development of numerous analytical methods for the quantitative determination of ADMA and dimethylarginines in biological systems, notably plasma, serum and urine.

Objectives

The aim of this work was to present a simple, fast and accurate UPLC-tandem-MS-based method for the simultaneous determination and quantification of arginine, ADMA, SDMA, NMMA, homo-arginine and citrulline. This method is designed for high sample throughput of only 10 μL of human plasma, serum or urine.

Methods

The analysis time is reduced to 1.9 min by an ultrahigh-performance liquid chromatography run coupled with electrospray ionization (ESI) in the positive mode tandem mass spectrometry detection.

Results

The method was validated in plasma, serum and urine. Correlation coefficients (r²) of the calibration curves in all matrices considered ranged from 0.9810 to 0.9993. Inter- and intra-assay precision, accuracy, recovery and carry-over were evaluated for validation. The LOD was 0.01 μM for all compounds in water, plasma and serum and 0.1 μM in urine. The LOQ was 0.05 μM for ADMA, SDMA, NMMA and H-Arg and 0.5 μM for Arg and Cit in water, plasma and serum; while in urine was 0.1 μM for ADMA, SDMA, NMMA and H-Arg and 0.5 μM for Arg and Cit.The precision was ranged from 1% to 15% expressed as CV% and the accuracy (bias %) was <±7% for all added concentrations with the exception of NMMA (−10%).ADMA mean plasma levels, measured in healthy adults and newborns, were in accord with literature data published: (M ± SD) 0.56 ± 0.10 μM and 0.84 ± 0.21 μM, respectively, showing that ADMA levels in plasma decreased with age. In serum we have similar data (0.54 ± 0.18 μM and 1.14 ± 0.36 μM), while in neonatal urine ADMA was 11.98 ± 7.13 μmol mmol⁻¹ creatinine.

Conclusions

Data from calibration curves and method validation reveal that the method is accurate and precise. The fast run time, the feasibility of high sample throughput and the small amount of sample required make this method very suitable for routine analysis in the clinical setting.     

Interference Mitigation on WLANs Using Smart Antennas

This paper investigates the performance of a fixed Wireless LAN in which nodes are equipped with fully adaptive smart antennas. The considered smart antenna system is a uniform circular array of microstrip patch elements in which the weights are updated using the unconstrained LMS algorithm. The behavior of a new directional MAC protocol for spatial multiplexing is analyzed and compared with IEEE 802.11 DCF. The paper purpose is the evaluation of interference and multipath effects on SDMA, using realistic models for the channel and for the smart antenna system. The link model takes into account path loss, cochannel interference and multipath, using a modified Jakes model. Results show that the performance of the WLAN are strictly dependent on the interferer characteristics and on the angular spread of the channel. Fulvio Babich was born in Trieste, Italy. He received the doctoral degree in electrical engineering, from the University of Trieste, in 1984. From 1984 to 1987 he was with the Research and Development Department of Telettra (Vimercate), working on optical communications. From 1987 to 1992 he was with Research and Development Department of Zanussi (Zeltron), where he held the position of Company Head in the Home System European projects. In 1992, he joined the Department of Electrical Engineering (DEEI) of the University of Trieste, where he is associate professor of digital communications. His current research interests are in the field of wireless networks and personal communications. Massimiliano Comisso was born in Trieste, Italy. He received the degree of “Laurea" in Electronic Engineering from the University of Trieste. Currently, he is a PhD student at the Department of Electrical Engineering (DEEI) at University of Trieste in information technology. His research interests include wireless networks, adaptive arrays and small antennas. Marco D'Orlando was born in Tolmezzo, Italy, in September 1978. He received the Electronic Engineering degree (summa cum laude) from the University of Trieste, Italy, in December 2003. He is currently working toward the Ph.D. degree in the Department of Electrical and Electronic Engineering (DEEI) at University of Trieste. His research interests are in the field of multimedia communications, networking, joint source channel coding and resource allocation. Lucio Manià was born in Ronchi dei Legionari, Italy, in 1942. He received the Electronic Engineering degree from the University of Trieste, Italy, in 1968. Since 1970 he has been an Assistant Professor with the Department of Electrical and Electronic Engineering, where he is currently an Associate Professor. From 1975 to 1985 he was a consulting engineer with Co.El. S.p.A., where he was involved in antenna design for FM and TV broadcasting systems. His current scientific interests include electromagnetic compatibility for safety purposes, wireless communications and numerical techniques for electromagnetic simulations.     

TD-SCDMA下载速率提升策略研究

TD-SCDMA的下载速率与其它两种3G标准相比存在一定的差距,同时建网经验也相对缺乏,本文通过对TD-SCDMA下载速率现状的分析研究,提出了现阶段可考虑采取的6个措施,以提升TD-SCDMA下载速率,改善用户体验。     

Intelligent MBWIMA/UMTS Protocol Using SDMA Scheduling in UTRA TDD Mode

The intelligent medium access control (MAC) protocol based on cascade fuzzy logic control (CFLC) using the first-duplicated space division multiple access (SDMA) scheduling for UTRA TDD mode is presented in this paper. Voice, data and video are integrated for transmission using CFLC-based movable boundary wireless multiple access in the UMTS (MBWIMA/UMTS) protocol. The CFLC-based MBWIMA/UMTS protocol performance with data rate control is optimized using the CFLC to generate the proper maximum number of voice/video slots and a suitable data rate. The first-duplicated SDMA scheduling, which provides the SDMA scheduling management, can increase the wireless mobile system capacity and reduce the voice-video dropping probability. The simulation results demonstrate that the CFLC-based MBWIMA/UMTS protocol using the first-duplicated SDMA scheduling can greatly improve both the voice-video dropping probability and data packet delay, compared with the MBWIMA/UMTS and GPRS/UMTS protocols using the first-duplicated SDMA scheduling at the expense of a small decrease in data packet throughput. Jeich Mar received the M.S. degree in electrical engineering from the National Taiwan University, Taiwan, R.O.C., in 1974 and the Ph.D. degree in electrical engineering from the University of Southern California, Los Angeles, in 1981. From 1981 to 1991, he worked as a Scientist in the Chung-Shang Institute of Science and Technology, Taiwan, where the worked on the development of a signal processor for phased array radar. He is currently a Professor in the Department of Communications Engineering, Yuan-Ze University, Taoyuan, Taiwan. His research interests include mobile communication and ap-plications of signal processing in Radar and Communication. Chih-Yang Kao was born in Hualien, Taiwan, Republic of China, 1974. He received the B.S., M.S. and Ph.D degree in electrical engineering from Yuan-Ze University, Taiwan in 1996, 1998 and 2004, respectively. He is now with Computer & Communications Research Laboratories, Industrial Technology Research Institute (CCL-ITRI). His current research interests include digital video broadcasting and wireless medium access control of next-generation mobile communication systems.     

A green scheduling with adaptive spatial division multiple access grouping for multi‐user coordinated multi‐point networks

Multi‐User Coordinated Multi‐Point (MU‐CoMP), which couples CoMP with Multi User‐Multiple Input Multiple Output (MU‐MIMO), appears as a promising solution to enhance the Long Term Evolution‐Advanced (LTE‐A) system performance. However, some challenging issues in MU‐CoMP networks require more investigation. First, the set of users transmitting under CoMP mode should be properly identified. Secondly, time‐frequency resource should be efficiently partitioned between CoMP and non‐CoMP users in order to improve the system radio capacity. Thirdly, a fair and green scheduler is much needed for a more energy efficient system. This paper deals with these three issues. We propose an adaptive transmission mode selection according to the total load in the cluster and to users' quality of service. The adequate size of the Spatial Division Multiple Access users' groups is also analyzed. We finally propose a new scheduling algorithm to further enhance the radio capacity and the energy consumption in the cluster. Simulations results showed that significant improvements are obtained in terms of total system throughput and outage probability in the cluster with our proposed scheme. Moreover, energy efficiency has increased by four times with our proposed scheduling algorithm as compared to commonly used schedulers. Copyright © 2015 John Wiley & Sons, Ltd.     

多用户MIMO系统中基于快速匹配调度的有限反馈SDMA

提出了一种能高效利用多用户分集和空分复用增益的有限反馈空分多址(SDMA,space division multiple access)方法。首先利用子空间扰动的方法构造了一种具有分簇结构的多用户预编码码本。基于该码本,进一步给出了一种新型的多用户机会调度算法,该算法利用码本的簇结构实现对信道条件匹配的用户组进行快速的机会调度,同时确定被调度用户的首选码字。仿真结果表明,在蜂窝网络中,与传统的有限反馈SDMA方法相比,所提方法可以在不明显增加反馈开销的前提下显著提高系统吞吐量。     

An MBER–BLAST algorithm for OFDM–SDMA communication using particle swarm optimization

A multiple antenna‐aided, minimum bit error rate–Bell Laboratories‐layered space–time (MBER–BLAST) multiuser detection algorithm is proposed for uplink orthogonal frequency division multiplexing–space division multiple access (OFDM–SDMA) communication to increase the capacity of the system. The proposed algorithm overcomes the limitations of the conventional detectors when the number of users exceed the number of receiver antennas. A particle swarm optimization (PSO) algorithm is employed for finding the optimum weight vectors for MBER detector. PSO is well suited for physically realizable, real‐time applications, where low complexity and fast convergence are of absolute importance, while an optimum maximum likelihood (ML) detection using an exhaustive search method is prohibitively complex. The proposed algorithm outperforms the MBER detector and is capable of achieving performance close to that attained by ML detector at a significantly lower complexity, especially under high user loads. Simulation results show that MBER–BLAST detector promises substantially improved performance compared with the existing systems and offers a good performance–complexity trade‐off. It supports a large number of users by exploiting the capacity advantages of multiple antenna systems in rich scattering environments. Copyright © 2010 John Wiley & Sons, Ltd.