bluuebunny/crossref_metadata_2025 huggingface dataset:
Complex Wurtzite ZnSe Microspheres with High Hierarchy and Their Optical Properties
Authors: Yao Weitang , Yu Shu‐Hong , Jiang Jun , Zhang Lin
Published: January 2006

Complex wurtzite ZnSe microspheres with hierarchical fractal structure and showing strong quantum‐size effects can be prepared easily by a mild solvothermal reaction in a diethylenetriamine (DETA)–deionized water (DIW) binary solution. The ZnSe microspheres are made up of nanosheets, each formed by the face‐to‐face pairing of two individual nanosheets. In addition, high‐order, flowerlike hierarchical structures are formed by the attachment of flexible, uniform nanofibers to the exposed faces of each nanosheet pair. The surface morphology of the nanosheets changed as reaction time increased and the detailed phase‐transformation and shape‐evolution processes were studied. This approach could provide an effective strategy for tuning the electronic and optical properties of semiconductors, with special advantages over the traditional high‐temperature approach, and could be extended to access other semiconductor materials with unusual morphologies and structures.
Spatial Extent of the Singlet and Triplet Excitons in Luminescent Angular‐Shaped Transition‐Metal Diynes and Polyynes Comprising Non‐π‐Conjugated Group 16 Main Group Elements
Authors: Poon Suk‐Yue , Wong Wai‐Yeung , Cheah Kok‐Wai , Shi Jian‐Xin
Published: January 2006

A novel approach based on conjugation interruption has been developed and is presented for a series of luminescent and thermally stable chalcogen‐bridged platinum(II) polyyne polymers trans‐[{Pt(PBu3)2CC(C6H4)E(C6H4)CC}n] (E=O, S, SO, SO2). Particular attention was focused on the photophysical properties of these Group 10 polymetallaynes and comparison was made to their binuclear model complexes trans‐[Pt(Ph)(PEt3)2CC(C6H4)E(C6H4)CCPt(Ph)(PEt3)2] and their closest Group 11 gold(I) and Group 12 mercury(II) neighbours, [MCC(C6H4)E(C6H4)CCM] (M=Au(PPh3), HgMe; E=O, S, SO, SO2). The regiochemical structures of these angular‐shaped molecules were studied by NMR spectroscopy and single‐crystal X‐ray structural analyses. Upon photoexcitation, each one has an intense purple‐blue fluorescence emission near 400 nm in dilute fluid solutions at room temperature. Harvesting of the organic triplet emissions harnessed through the strong heavy‐atom effects of Group 10–12 transition metals was studied in detail. These metal‐containing aryleneethynylenes spaced by chalcogen units were found to have large optical gaps and high‐energy triplet states. The influence of metal‐ and chalcogen‐based conjugation interrupters on the intersystem crossing rate and on the spatial extent of the lowest singlet and triplet excitons was fully elucidated. We discuss and compare the phosphorescence spectra of these transition‐metal diynes and polyynes in terms of the nature of the metal centre, conjugated chain length and Group 16 spacer unit. Our work here indicates that high‐energy triplet states in these materials intrinsically give rise to very efficient phosphorescence with fast radiative decays and one could readily observe room‐temperature phosphorescence for the platinum polyynes.
A Stacking Interaction between a Bridging Hydrogen Atom and Aromatic π Density in the n‐B18H22–Benzene System
Authors: Hamilton Ewan J. M. , Kultyshev Roman G. , Du Bin , Meyers Edward A. , Liu Shengming , Hadad Christopher M. , Shore Sheldon G.
Published: January 2006

The structures of n‐B18H22 and of n‐B18H22⋅C6H6 were determined by single‐crystal X‐ray analysis at −60 °C. The geometry of the boron cluster itself does not seem to be appreciably affected by solvation. There does, however, appear to be an unusual interaction of a polyborane bridging hydrogen atom with the benzene π system, giving rise to an extended stacked structure. The 1H{11B} spectrum of n‐B18H22 in [D6]benzene differs from that in [D12]cyclohexane most noticeably in the bridging proton region. Upon moving from the aliphatic to the aromatic solvent, the greatest increase in shielding was for the signal corresponding to the bridge hydrogen atom that interacts with the π system of benzene; the signal was shifted upfield by 0.49 ppm. Density functional theory calculations were performed on 1:1 and 2:1 complexes of the n‐B18H22 unit with benzene.
Kinetic Energy Release of C70+ and Its Endohedral Cation N@C70+: Activation Energy for N Extrusion
Authors: Cao Baopeng , Peres Tikva , Lifshitz Chava , Cross R. James , Saunders Martin
Published: January 2006

Unimolecular decomposition of C70+ and its endohedral cation N@C70+ were studied by high‐resolution mass‐analyzed ion kinetic energy (MIKE) spectrometry. Information on the energetics and dynamics of these reactions was extracted. C70+ dissociates unimolecularly by loss of a C2 unit, whereas N@C70+ expels the endohedral N atom. Kinetic energy release distributions (KERDs) in these reactions were measured. By use of finite heat bath theory (FHBT), the binding energy for C2 emission from C70+ and the activation energy for N elimination from N@C70+ were deduced from KERDs in the light of a recent finding that fragmentation of fullerene cations proceeds via a very loose transition state. The activation energy measured for N extrusion from N@C70+ was found to be lower than that for C2 evaporation, higher than the value from its neutral molecule N@C70 obtained on the basis of thermal stability measurements, and coincident with the theoretical value. The results provide confirmation that the proposed extrusion mechanism in which the N atom escapes from the cage via formation of an aza‐bridged intermediate is correct.
Cover Picture: Utilization of Self‐Sorting Processes To Generate Dynamic Combinatorial Libraries with New Network Topologies (Chem. Eur. J. 4/2006)
Authors: Saur Isabelle , Scopelliti Rosario , Severin Kay
Published: January 2006

Dynamic combinatorial libraries can be regarded as adaptive chemical networks, in which the library members are connected by exchange reactions. In the Full Paper by K. Severin et al. on page 1058 ff., a library of metallamacrocyclic ruthenium and iridium complexes with a unique network topology is described.
Adiponectin, ghrelin, and leptin in cancer cachexia in breast and colon cancer patients
Authors: Wolf Ido , Sadetzki Seigal , Kanety Hannah , Kundel Yulia , Pariente Clara , Epstein Nava , Oberman Bernice , Catane Raphael , Kaufman Bella , Shimon Ilan
Published: January 2006

BACKGROUND

The hormone ghrelin and the adipocytokines leptin and adiponectin participate in body weight regulation. In response to weight loss, ghrelin and adiponectin levels increase and leptin decreases. Cancer cachexia is a complex metabolic state, characterized by loss of muscle mass and adipose tissue together with anorexia. The authors hypothesized that responses of these hormones may be attenuated in cancer cachexia.

METHODS

Fasting plasma ghrelin, adiponectin, and leptin levels, as well as weight loss, were determined in 40 cancer patients: 18 of them suffered from cancer‐induced cachexia, and 22 served as a comparison group. Hormone levels were measured before administration of cancer therapy.

RESULTS

A similar distribution of age, gender, and diagnosis was observed in both study groups, but the cachectic patients had higher rates of metastatic disease and lower albumin levels. No significant correlation was observed between plasma adiponectin levels and weight loss. Mean plasma ghrelin levels were higher among cachectic compared with noncachectic patients. Notably, the association between ghrelin levels and weight loss was only modest, and in a third of the cachectic patients, ghrelin levels were equal to or lower than those in the noncachectic group. Plasma leptin levels showed gender‐dependent associations, and significantly lower levels were found among cachectic women but not among cachectic men.

CONCLUSIONS

Results suggested a gender‐dependent attenuation of expected physiologic responses to weight loss among cancer cachexia patients. Thus, impaired response of adiponectin, ghrelin, and leptin may play a role in the pathogenesis of cancer cachexia syndrome. Cancer 2006. © 2006 American Cancer Society.
Effective Controlled Release of Captopril by Silylation of Mesoporous MCM‐41
Authors: Qu Fengyu , Zhu Guangshan , Huang Shiying , Li Shougui , Qiu Shilun
Published: January 2006

The release of the water‐soluble drug Captopril is controlled by tailoring the surface properties of mesoporous silica via stepwise silylation. The degree of silylation is manipulated by adjusting the initial concentration of silylanizing reagent (trimethylchlorosilane, TMCS). The silylanized and drug‐loaded samples are characterized by powder X‐ray diffraction, Fourier transform IR spectroscopy, N2 adsorption and desorption,29Si cross‐polarization magic angle spinning NMR spectroscopy, and transmission electron microscopy. The drug‐loading amount is correlated to the Brunauer–Emmett–Teller surface area and surface hydrophilicity/hydrophobicity of the mesoporous silica material, while drug release profiles can be controlled by tailoring the surface properties and pore size.
Probing the Acidity of p‐Substituted Phenols in the Excited State: Electronic Spectroscopy of the p‐Cyanophenol–Water Cluster
Authors: Jacoby Christoph , Böhm Marcel , Vu Chau , Ratzer Christian , Schmitt Michael
Published: January 2006

The hydrogen bond structure of the p‐cyanophenol–water cluster has been determined in the ground and first excited electronic state by rotationally resolved UV spectroscopy. The water molecule is trans‐linearly bound to the hydroxy group of the p‐cyanophenol moiety, with hydrogen bond distances considerably shorter in both electronic states than in the similar phenol‐water cluster. The structure of the cluster has been elucidated by ab initio calculations at various levels of theory and compared to the experimental findings. The barriers to internal rotation of the water moiety were determined experimentally to be 275 and 183 cm−1for the ground and excited state, respectively. Hydrogen bond distances and the energy barrier to water torsion correlate with the pKavalues of different substituted phenols for both electronic states.
Chair, Boat and Twist Conformation of Dodecamethylcyclohexasilane and Undecamethylcyclohexasilane: A Combined DFT and Raman Spectroscopic Study
Authors: Tekautz Günter , Binter Alexandra , Hassler Karl , Flock Michaela
Published: January 2006

The conformations of dodecamethylcyclohexasilane Si6Me12 and undecamethylcyclohexasilane Si6Me11H have been investigated by ab initio calculations employing the B3LYP density functional with a 6‐31+G(d) basis set. Local minima as well as transition structures were calculated with imposed symmetry constraints. For Si6Me12, three unique minima, which correspond to the chair, twist and boat conformations were located with relative zero‐point‐vibration‐corrected energies of 0.0, 7.8 and 11.4 kJ mol−1. A half‐chair conformation with four coplanar silicon atoms connects the chair and twisted minima via an energy barrier of 16.0 and 8.2 kJ mol−1, respectively. A second transition structure with a barrier of 3.9/0.3 kJ mol−1connects the twist with the boat structure. Solution Raman spectra of Si6(CH3)12 and Si6(CD3)12 fully corroborate these results. Below −40 °C, the symmetric SiSi ring breathing vibration is a single line, which develops a shoulder (originating from the twist conformer) at longer wavelengths whose intensity increases with increasing temperature. From a Van′t Hoff plot, the chair/twist enthalpy difference is 6.6±1.5 kJ mol−1for Si6(CH3)12 and 6.0±1.5 kJ mol−1for Si6(CD3)12, which is in reasonable agreement with the ab initio results. Due to the low barrier, the boat conformation cannot be observed, because either the lowest torsional vibration level lies above it or a rapid interconversion between the twist and boat conformations occurs, resulting in averaged Raman spectra. For Si6Me11H, six local minima were located. The chair with the hydrogen atom in the axial position (axial chair) is the global minimum, followed by the equatorial chair (+1.9 kJ mol−1) and the three twist conformers (+5.3, +8.0 and +8.1 kJ mol−1). The highest local minimum (+11.9 kJ mol−1) is a Cssymmetric boat with the hydrogen atom in the equatorial position. Two possible pathways for the chair‐to‐chair interconversion with barriers of 13.9 and 14.5 kJ mol−1have been investigated. The solution Raman spectra in the SiSi ring breathing region clearly show that below −50 °C only the axial and equatorial chairs are present, with an experimental ΔH‐value of 0.46 kJ mol−1. With increasing temperature a shoulder develops which is attributed to the combined twist conformers. The experimental ΔH‐value is 6.9 kJ mol−1, in good agreement with the ab initio results. Due to the low interconversion barriers, the various twist conformers cannot be detected separately.
Determining Molecular Structures and Conformations Directly from Electron Diffraction using a Genetic Algorithm
Authors: Habershon Scott , Zewail Ahmed H.
Published: January 2006

A global optimization strategy, based upon application of a genetic algorithm (GA), is demonstrated as an approach for determining the structures of molecules possessing significant conformational flexibility directly from gas‐phase electron diffraction data. In contrast to the common approach to molecular structure determination, based on trial‐and‐error assessment of structures available from quantum chemical calculations, the GA approach described here does not require expensive quantum mechanical calculations or manual searching of the potential energy surface of the sample molecule, relying instead upon simple comparison between the experimental and calculated diffraction pattern derived from a proposed trial molecular structure. Structures as complex as all‐trans retinal and p‐coumaric acid, both important chromophores in photosensing processes, may be determined by this approach. In the examples presented here, we find that the GA approach can determine the correct conformation of a flexible molecule described by 11 independent torsion angles. We also demonstrate applications to samples comprising a mixture of two distinct molecular conformations. With these results we conclude that applications of this approach are very promising in elucidating the structures of large molecules directly from electron diffraction data.
On parameter estimation of a simple real‐time flow aggregation model
Authors: Fu Huirong
Published: January 2006

There exists a clear need for a comprehensive framework for accurately analysing and realistically modelling the key traffic statistics that determine network performance. Recently, a novel traffic model, sinusoid with uniform noise (SUN), has been proposed, which outperforms other models in that it can simultaneously achieve tractability, parsimony, accuracy (in predicting network performance), and efficiency (in real‐time capability). In this paper, we design, evaluate and compare several estimation approaches, including variance‐based estimation (Var), minimum mean‐square‐error‐based estimation (MMSE), MMSE with the constraint of variance (Var+MMSE), MMSE of autocorrelation function with the constraint of variance (Var+AutoCor+MMSE), and variance of secondary demand‐based estimation (Secondary Variance), to determining the key parameters in the SUN model. Integrated with the SUN model, all the proposed methods are able to capture the basic behaviour of the aggregation reservation system and closely approximate the system performance. In addition, we find that: (1) the Var is very simple to operate and provides both upper and lower performance bounds. It can be integrated into other methods to provide very accurate approximation to the aggregation's performance and thus obtain an accurate solution; (2) Var+AutoCor+MMSE is superior to other proposed methods in the accuracy to determine system performance; and (3) Var+MMSE and Var+AutoCor+MMSE differ from the other three methods in that both adopt an experimental analysis method, which helps to improve the prediction accuracy while reducing computation complexity. Copyright © 2005 John Wiley & Sons, Ltd.
Hyperelliptic curves encryption combined with block codes for Gaussian channel
Authors: Jirón I. , Soto I. , Carrasco R. , Becerra N.
Published: January 2006

In this paper, a new cryptographic system is constructed using a combination of a hyperelliptic curve of genus g = 2 over the Galois field GF(2n) and a Reed–Solomon code (N, K) over the Galois field GF(2m) and this system uses a smaller key than the elliptic curves cryptosystem and the Rivest, Shamir, and Adleman cryptosystem. The design criterion for the combination can be expressed as the data compression condition and addressing capability of the code. In addition, the system performance is compared with other systems; extraordinary improvements of 8 and 16.5 dB can be obtained for a BER = 10−5, when compared with binary phase shift keying and differential chaos shift keying, respectively. This system has a polynomial complexity, which depends on data length and the number of operations in GF(2n). Copyright © 2005 John Wiley & Sons, Ltd.
Closed‐form expression for the BER of m‐QAM‐OFDM systems over time‐ and frequency‐selective wireless channels
Authors: Castells F. , Almenar V.
Published: January 2006

The broadcast DVB‐T system is an m‐QAM‐OFDM communication system that includes pilot‐symbol‐assisted modulation (PSAM) in order to enhance channel estimation at the receiver. This characteristic makes DVB‐T suitable for a mobile reception, over time‐ and frequency‐selective wireless channels. In this work, a closed‐form expression for the BER as a function of the transmission system, channel model and the channel estimation strategy employed at the receiver is derived. In addition, adjacent channel interference due to Doppler effects is also considered. The results are focused on the DVB‐T system under different scenarios. The channel estimation at the receiver has been shown to be very critical, and the impact of channel estimation errors on the BER is analysed in detail. Copyright © 2005 John Wiley & Sons, Ltd.
Improving fairness of PGMCC
Authors: Chen Hualiang , Liu Zhongxin , Chen Zengqiang , Yuan Zhuzhi
Published: January 2006

PGM congestion control (pgmcc), a single‐rate multicast congestion control scheme, is one of the most promising schemes which aim to solve the problem of multicast fairness with TCP. However, by deep investigation, we find that there exist two inappropriate mechanisms in this scheme, which are the fixed slow start threshold (ssthresh) and the mechanism of changing a group representative (acker). Our experiments have revealed the fact that these mechanisms can lead to the unfairness of pgmcc under some network conditions. In this paper, two new mechanisms have been proposed to replace the original ones. One mechanism is to make the sender adapt the value of ssthresh to the network conditions to mimic the action of TCP, and in order to avoid being more aggressive than TCP, the other one is to make the sender reduce the congestion window by half when the acker changes. Our experiment results, parts of which are discussed in this paper, show that the modified pgmcc can achieve better performance than the original one. Copyright © 2005 John Wiley & Sons, Ltd.
An efficient MAC protocol for multi‐channel mobilead hocnetworks based on location information
Authors: Tseng Yu‐Chee , Wu Shih‐Lin , Chao Chih‐Min , Sheu Jang‐Ping
Published: January 2006

This paper considers thechannel assignmentproblem in a multi‐channel MANET environment. We propose a scheme calledGRID, by which a mobile host can easily determine which channel to use based on its current location. In fact, following the GSM style, our GRID spends no communication cost to allocate channels to mobile hosts since channel assignment is purely determined by hosts' physical locations. We show that this can improve thechannel reuseratio. We then propose a multi‐channel MAC protocol, which integrates GRID. Our protocol is characterized by the following features: (i) it follows an ‘on‐demand’ style to access the medium and thus a mobile host will occupy a channel only when necessary, (ii) the number of channels required is independent of the network topology, and (iii) no form of clock synchronization is required. On the other hand, most existing protocols assign channels to a host statically even if it has no intention to transmit [IEEE/ACM Trans. Networks1995;3(4):441–449; 1993;1(6): 668–677;IEEE J. Selected Areas Commun.1999;17(8):1345–1352], require a number of channels which is a function of the maximum connectivity [IEEE/ACM Trans. Networks1995;3(4):441–449; 1993;1(6): 668–677;Proceedings of IEEE MILCOM'97,November 1997;IEEE J. Selected Areas Commun.1999;17(8):1345–1352], or necessitate a clock synchronization among all hosts in the MANET [IEEE J. Selected Areas Commun.1999;17(8):1345–1352;Proceedings of IEEE INFOCOM'99, October 1999]. Through simulations, we demonstrate the advantages of our protocol. Copyright © 2005 John Wiley & Sons, Ltd.
The CSMA/DM LAN protocol
Authors: Peng Wuxu , Makki Shamila
Published: January 2006

We propose an extension of the classical CSMA/CD protocol that eliminates its three main drawbacks. The new protocol, called dual‐mode CSMA/CD (CSMA/DM), operates in two modes, light mode and heavy mode. The light mode of CSMA/DM is almost the same as the original CSMA/CD protocol and is primarily used when the LAN load is light. The heavy mode is a collision free mode and is applied when the LAN load is heavy.

The proposed modification to CSMA/CD is minimal while performance gain is significant. CSMA/DM automatically switches between its two modes based on the observed LAN load. Under heavy mode, the monitor station in a CSMA/DM LAN allocates bandwidth to those busy stations without collisions. The newly added priority scheme in the heavy mode allows stations to reserve bandwidth for their high priority frames.

Compared with the current collision‐free fast Ethernet and Gigabit Ethernet, CSMA/DM has the advantage of not needing any extra switches or hubs while maintaining comparable performance. Its priority scheme provides more flexibility on bandwidth distribution than in fast Ethernet and Gigabit Ethernet. It can also be easily adapted for high‐speed wireless LANs. More importantly, CSMA/DM should be a good alternative of the widely used CSMA/CA (collision avoidance) in mobile ad hoc networks (MANET) and sensor networks. Copyright © 2005 John Wiley & Sons, Ltd.
MAC‐assisted topology control forad hocwireless networks
Authors: Rahman A. , Gburzynski P.
Published: January 2006

We considerad hocwireless networks and the topology control problem defined as minimizing the amount of power needed to maintain connectivity. The issue boils down to selecting the optimum transmission power level at each node based on the position information of reachable nodes. Local decisions regarding the transmission power level induce a subgraph of the maximum powered graphGmaxin which edges represent direct reachability at maximum power. We propose a new algorithm for constructing minimum‐energy path‐preserving subgraphs ofGmax, i.e. ones minimizing the energy consumption between node pairs. Our algorithm involves a modification to the medium access control (MAC) layer. Its superiority over previous solutions, up to 60% improvement in sparse networks, demonstrates once again that strict protocol layering in wireless networks tends to be detrimental to performance. Copyright © 2005 John Wiley & Sons, Ltd.
Improved implementation solution and general mobile network architecture for the interworking between MMS and streaming
Authors: Miraj‐E‐Mostafa A.
Published: January 2006

The prospects of multimedia in mobile communication depend largely on effective design of interactive multimedia applications now. Multimedia Messaging Service (MMS) and streaming are two potential multimedia applications for mobile communication. Though MMS has many advantages, a limitation is noted in MMS—an inability to handle a message requiring more space than available in a mobile terminal, as the message must be fully retrieved and stored before its presentation. Moreover, a large message can keep a recipient user waiting long for its retrieval before it is presented, causing poor user‐experience. This paper proposes a new implementation solution for the interworking between MMS and streaming to overcome the limitation. The new solution is consistent with the existing frameworks and working principles of both MMS and streaming. The new solution is compared with the previous solutions, indicating that it has considerable advantages. This paper also presents general network architecture, providing various architectural options, to accommodate the interworking in different situations. The architecture considers many practical cases, like person‐to‐person messaging, messaging involving content providers and multiple network operators, load balancing and scalability in related network servers, operational agreement between a content provider and a network operator, and using existing network infrastructure for the interworking. Copyright © 2005 John Wiley & Sons, Ltd.
Enhancing data throughput and lower correlations quasi orthogonal functions for 3G CDMA systems
Authors: Hou Jia , Lee Moon Ho
Published: January 2006

The forward link of the 3G code‐division multiple‐access (CDMA) system may become limited under the increasing of the number of users. The conventional channelization code, Walsh code, has not enough sizes for much possible users, therefore, the quasi orthogonal function (QOF), which can process optimal cross‐correlation with Walsh code, is considered.

To obtain lower correlations and better performance in 3G CDMA system, we investigate a quasi orthogonal function on Jacket matrices in this paper. Secondly, to simplify the detector and improve the bit error rate (BER) performance, we provide a novel detection scheme for QOF CDMA system. Finally, we give a brief discussion about a simple recursive generation of the bent sequences for QOF mask function. Copyright © 2005 John Wiley & Sons, Ltd.
QPSK differential space time coding on different unitary matrices sets and initializations
Authors: Hou Jia , Ho Lee Moon
Published: January 2006

This paper investigates a distinct set of complex unitary matrices for differential space time coding by using QPSK modulation. The numerical results show that the proper selection of the initial transmission matrix and the set of unitary matrices can efficiently improve the bit error rate performance, especially for the antennas correlated fading channel. The computer simulations are evaluated over slow and fast Rayleigh fading channels. Copyright © 2005 John Wiley & Sons, Ltd.
A zone co‐operation approach for efficient caching in mobilead hocnetworks
Authors: Chand Narottam , Joshi R. C. , Misra Manoj
Published: January 2006

MobileAd hocNETwork (MANET) presents a constrained communication environment due to fundamental limitations of client resources, insufficient wireless bandwidth and users' frequent mobility. Caching of frequently accessed data in such environment is a potential technique that can improve the data access performance and availability. Co‐operative caching, which allows the sharing and co‐ordination of cached data among clients, can further explore the potential of the caching techniques. In this paper, we propose a novel scheme, calledzone co‐operative(ZC) for caching in MANETs. In ZC scheme, one‐hop neighbours of a mobile client form a co‐operative cache zone. For a data miss in the local cache, each client first searches the data in its zone before forwarding the request to the next client that lies along routing path towards server. As a part of cache management, cache admission control andvalue‐based replacement policy are developed to improve the data accessibility and reduce the local cache miss ratio. An analytical study of ZC based on data popularity, node density and transmission range is also performed. Simulation experiments show that the ZC caching mechanism achieves significant improvements in cache hit ratio and average query latency in comparison with other caching strategies. Copyright © 2006 John Wiley & Sons, Ltd.
Improving broadcast performance by traffic isolation in wirelessad hocnetworks
Authors: Purtoosi Reza , Taheri Hassan , Mohammadi Abbas , Foroozan Foroohar
Published: January 2006

In this paper we propose a new broadcasting algorithm. In the proposed method we significantly reduce the broadcast overhead and also improve the broadcast delivery ratio in mobile networks. A novel traffic isolation method has been used which reduces the control message exchange. The proposed broadcasting method is based on a clustering method called ‘stability‐based clustering algorithm’ which had been proposed before. The broadcasting traffic is divided into internal (flow inside a cluster) and external traffic (flow among the clusters). For internal flooding traffic, cluster‐heads and gateways are responsible for re‐broadcasting but for external type, border nodes may perform the forwarding function as well. This simplifies the gateway selection method through the local selection of gateway nodes by its cluster head. Therefore, a cluster head selects gateway in its own cluster without any knowledge of other clusters. Considering the effect of mobility and node density, simulations have been conducted in a number of wireless environments. Simulation results show the broadcast coverage is close to 100% at different node speeds. Moreover, we study the broadcast parameters in light and dense networks and show improvement of the overhead and the number of forward nodes in comparison to other broadcasting methods. Copyright © 2005 John Wiley & Sons, Ltd.
The evolving UK wind energy industry: critical policy and management aspects of the emerging research agenda
Authors: Strachan Peter A. , Lal David , von Malmborg Fredrik
Published: January 2006

In recent years, renewable energy – and in particular wind power – has come to the fore of both international and UK national environmental policy debates. In addition to helping to meet its Kyoto obligations, the British Government has indicated its desire for a much larger slice of the international wind energy market, and has consequently developed a national strategy to stimulate a more vibrant UK wind energy industry. With this in mind, the British Government's Climate Change Programme (DETR, 2000) and more recent Energy White Paper (DTI, 2003) outline the UK energy strategy for the coming two decades, with wind power featuring as a core component. This article critically considers the prospects for the development of a wind energy industry in the UK and introduces five strategic opportunities and five strategic barriers in this evolving segment of the energy market. The article concludes with recommendations to enhance public acceptance of wind energy and four important areas for future research are outlined. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.
Public and stakeholder participation in European water policy: a critical review of project evaluation processes
Authors: Videira Nuno , Antunes Paula , Santos Rui , Lobo Gonçalo
Published: January 2006

The recent reform of the European water policy recognizes the importance of developing effective mechanisms to support public and stakeholder participation in river basin decision‐making processes. This paper critically reviews the evaluation processes of different types of water related project in five European countries (Portugal, Greece, The Netherlands, the United Kingdom and Spain), with respect to participatory criteria. The horizontal comparison of these cases accounted for criteria such as the political and institutional context, the design, the implementation and the evaluation of the outcomes of participation. The results indicated that, in the majority of the case studies, participation was simply adopted to conform to the requisites of the Environmental Impact Assessment Directive. Thus, there was truly no room for the active involvement and collaboration of the interested parties. The development of guidelines, drawing from the analysis of past experiences, is expected to support the implementation of the participatory objectives of the EU water policy. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.
Policy profile: how Dutch environmental policy contributes to meet European environmental standards; Dutch environmental balance
Authors: van Wezel Annemarie P. , Kruitwagen Sonja , Maas Rob
Published: January 2006

In the Dutch ‘environmental balance’ the effectiveness of Dutch environmental policy in meeting European environmental standards is evaluated. Major themes in the environmental balance are eco‐efficiency, climate change, manure policy, air quality and urban environment, and the general developments in Dutch environmental policy in the past 15 years.

 Main conclusions are that European policy results in a considerable emission reduction, however not enough to meet EU environmental quality standards. Compared to other EU member states, The Netherlands is densely populated and built, resulting in high emissions per square kilometre. Moreover, The Netherlands has a substantial contribution of contamination from abroad, although it is itself a net exporter of pollution. Therefore, additional national measures are necessary to meet the EU quality standards.

 The wish to have a ‘level playing field’ for industry may conflict with the wish to protect citizens equally against a low environmental quality. Spatial solutions are frequently chosen as additional measures, by separating sources of pollution from citizens or nature. In this way, additional national emission reduction measures on top of European emission policy are avoided. However, this spatial separation is not always effective. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.
The role of indicators in improving timeliness of international environmental reports
Authors: Rosenström Ulla , Lyytimäki Jari
Published: January 2006

Environmental indicators were developed mainly to improve information flows from scientists to policy‐makers. This article discusses the importance of timely environmental data and investigates the influence of indicator‐based reporting on the data timeliness of environmental reports by international organizations. Timeliness of information contributes to the quality and appeal of the reports, and to their role as early warning tools, and increases their usability by decision‐makers in short‐term decision cycles. The results of an analysis of 11 international reports by the European Environmental Agency (EEA) and the Organization for Economic Co‐Operation and Development (OECD) show a considerable time lag of three years on average, with only minor development towards more timely reporting. The results suggest that the introduction of environmental indicators has not improved the timeliness of reporting. In order to overcome these problems, the article recommends some methods for improving timeliness. These include better choice of indicators in smaller sets, use of preliminary data and outlooks, development of new indicators, publishing on the internet and more effective use of internet databases to avoid intermediate levels in data collection. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.
Another Example of the Instability of a Keggin‐Type Heteropolyanion in the Presence of Aqueous Hydrogen Peroxide: From [AsW12O40]3– to Low‐Nuclearity Oxoperoxotungstates – Crystal Structure of [(nHex)4N]3[AsO4{W2O2(μ‐O2)2(O2)2}2]
Authors: Piquemal Jean‐Yves , Salles Laurent , Chottard Geneviève , Herson Patrick , Ahcine Chehrazed , Brégeault Jean‐Marie
Published: January 2006

The Keggin dodecatungstoarsenato anion of HNa2[AsW12O40] is inherently unstable in aqueous hydrogen peroxide and is mainly degraded to [AsO4{W2O2(μ‐O2)2(O2)2}2]3–, [HAsO4{W2O2(μ‐O2)2(O2)2}]2– and [{WO(O2)2(H2O)}2(μ‐O)]2–. These anions were isolated as salts and identified by elemental and spectroscopic analyses. The salt with the formula [(nC6H13)4]3[AsO4{W2O2(μ‐O2)2(O2)2}2] was obtained from the reaction of tungstic acid, “H2WO4” (or HNa2[AsW12O40]·nH2O), with aqueous hydrogen peroxide, HNa2[AsO4]·7H2O and [(nC6H13)4N]Cl. The structure was refined with R1 = 0.058 and wR2 = 0.067 [monoclinic C2 (no. 5); a = 20.516(6) Å, b = 15.923(4) Å, c = 14.902(2) Å, β = 91.64(1)°, Z = 2]. The vibrational spectra (IR and Raman) suggest that the overall structure is maintained in organic solvents. The close relation between the phosphate‐ and arsenate‐based complexes indicates that fluxional behaviour may exist for all these di‐ and tetranuclear complexes. Fluxionality may play a key role in the transfer of active oxygen (from peroxo groups) to organic substrates via {WO(O2)2} units. It is shown that the heteroligand [XOp]n– (X = As, HAs, MeAs, P, HP, etc.) has a marked effect on the stoichiometric and regioselective epoxidation of (R)‐(+)‐limonene to 1,2‐epoxide at ambient temperature, for a given pH of the aqueous phase. The oxodiperoxo complexes can be used to carry out epoxidation stoichiometrically and regioselectively with (R)‐(+)‐limonene, but can also be employed in a catalytic process in a two‐phase mixture at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Study on separation of aristolochic acid I and II by micellar electrokinetic capillary chromatography and competition mechanism between SDS and β‐cyclodextrin
Authors: Li Wei , Chen Zheng , Liao Yiping , Liu Huwei
Published: January 2006

In this study, a rapid MEKC method using 40 mM sodium borate buffer containing 50 mM SDS as surfactant was developed for the analysis of aristolochic acid (AA) in Aristolochia plants. Baseline separation of AA‐I and AA‐II was achieved within 3 min with high separation efficiency, satisfactory sensitivity, repeatability, and recovery. Resolution between AA‐I and AA‐II is above 5 and great performance with higher than 200 000 theoretical plate numbers was obtained. The detection limits (based on 3 S/N) were both 1.0 μg/mL. Two kinds of AA in 35 herbal samples of Aristolochia plants were successfully determined. The competition mechanism between β‐CD and SDS was also investigated by changing the content ratio of β‐CD and SDS.
Determination of biogenic amines in HeLa cell lysate by 6‐oxy‐(N‐succinimidyl acetate)‐9‐(2'–methoxycarbonyl) fluorescein and micellar electrokinetic capillary chromatography with laser‐induced fluorescence detection
Authors: Cao Liwei , Wang Hong , Ma Ming , Zhang Huashan
Published: January 2006

An MEKC‐LIF method using 6‐oxy‐(N‐succinimidyl acetate)‐9‐(2'‐methoxy‐carbonyl) fluorescein (SAMF) newly synthesized in our lab as a labeling reagent for the separation and determination of eight typical biogenic amines was proposed. After careful study of the derivatization condition such as pH value, reagent concentration, temperature, and reaction time, derivatization reaction was accomplished as quickly as 10 min with stable yield. Optimal separation of SAMF‐labeled amines was achieved with a running buffer (pH 9.3) containing 30 mM boric acid, 25 mM SDS, and 20% v/v ACN. The proposed method allowed biogenic amines to be determined with LODs as low as 0.25–2.5 nmol/L and RSD values from 0.4 to 4.5%. The present method has been successfully used to monitor biogenic amines in HeLa cells and fish samples. This study exploits the potential of MEKC‐LIF with SAMF labeling as a tool for monitoring biogenic amines involved in complex physiological and behavioral processes in various matrices.
Separation and quantitation of the four stereoisomers of itraconazole in pharmaceutical formulations by electrokinetic chromatography
Authors: Castro‐Puyana María , Crego Antonio L. , Marina M. Luisa
Published: January 2006

The four stereoisomers of itraconazole were resolved for the first time by EKC using a CD as chiral selector. A study on the enantiomeric separation ability of different neutral CDs was carried out. Heptakis‐2,3,6‐tri‐O‐methyl‐β‐CD was shown to provide the highest values for the enantiomeric resolution. The influence of some experimental conditions, such as pH, chiral selector concentration, and temperature, on the enantiomeric separation was also studied. The use of a 100 mM phosphate buffer (pH 2.5), 30 mM in heptakis‐2,3,6‐tri‐O‐methyl‐β‐CD together with an applied voltage of 30 kV and a temperature of 20°C enabled the separation of the enantiomers of itraconazole with high resolutions (Rs > 3.0). Finally, the method was validated and successfully applied to the quantitation of itraconazole in three pharmaceutical formulations.
Capillary electrochromatography of biologically relevant flavonoids
Authors: Stöggl Wolfgang M. , Huck Christian W. , Stecher Günther , Bonn Günther K.
Published: January 2006

Flavonoids were separated utilizing CEC technique. Baseline separation of biologically relevant flavonoids was obtained using a 100 μm ID fused‐silica capillary filled with 3 μm Silica‐C18 material and an optimized mobile phase comprising of 20 mM Tris‐HCl (pH 6.5), ACN and water at a ratio of 10/40/50 v/v/v. Separations were carried out at 25 kV and a column temperature of 25°C. The influence of relevant parameters for the CEC separation, such as buffer concentration, pH, separation voltage, and ACN concentration, was investigated and optimized. Dependencies of the electroendoosmotic flow (EOF) on these parameters and effects on the resolution of the analytes were studied. During analyses the solvents used for dissolving the samples turned out to have significant effects on the separation of flavonoids. The optimized system was then successfully used for the separation of the flavonoids epicatechin, myricetin, quercetin, naringenin, and hesperetin. CEC turned out to be a useful complementary tool for the economic analysis of flavonoids in addition to common HPLC, μHPLC, and CE methodologies. This method can be used for real applications in phytomics.
Rapid determination of acyclovir in plasma and cerebrospinal fluid by micellar electrokinetic chromatography with direct sample injection and its clinical application
Authors: Yeh Hsin‐Hua , Yang Yuan‐Han , Chen Su‐Hwei
Published: January 2006

A simple MEKC with UV detection at 254 nm for analysis of acyclovir in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of acyclovir from biological matrix was performed at 25°C using a BGE consisting of Tris buffer with SDS as the electrolyte solution. Several parameters affecting the separation of the drug from biological matrix were studied, including the pH and concentrations of the Tris buffer and SDS. Using dyphylline as an internal standard, the linear ranges of the method for the determination of acyclovir in plasma and in CSF all exceeded the range of 2–50 μg/mL; the detection limit of the drug in plasma and in CSF (S/N = 3; injection 3.45 kPa, 5 s) was 1.0 μg/mL. The applicability of the proposed method for determination of acyclovir in plasma and CSF collected at 8 h after intravenous administration of 500 mg acyclovir (Zovirax®) in two patients with herpes simplex encephalitis was demonstrated.
An on‐column derivatization method for the determination of the enantiomeric excess of chiral primary amines via indirect enantioseparation by micellar electrokinetic chromatography
Authors: Cheng Jiayi , Kang Jingwu
Published: January 2006

A method used for determining the enantiomeric excess (ee) value of chiral amino compounds by MEKC is described. In this method, the plug‐plug type electrophoretic medicated microanalysis technique was employed to convert the enantiomers of chiral amino compounds into their diastereomers through an on‐column derivatization with o‐phthaldialdehyde and the chiral reagent N‐acetyl‐L‐cysteine. Afterwards, the resulting diastereomers were easily separated with a nonchiral MEKC approach. The on‐column derivatization conditions and the separation conditions were optimized and the method was validated with five chiral amino compounds. The present method can be used for assaying the ee value of chiral amino compound with various structural features, especially for those that have no UV chromophore. Therefore, the method can be potentially used for screening or evaluation of the asymmetric catalysts developed by the combinatorial chemistry. In this case, the ee values of chiral products with various structures need to be measured; however, this is difficult for direct chiral separation approach due to the fact that the chiral selectivity is strongly dependent on the structure of the analytes. The method is simple, reliable, and automatic.
Metallomesogenic stationary phase for open‐tubular capillary electrochromatography
Authors: Chen Jian‐Lian
Published: January 2006

A synthetic coppermesogenic polymer is prepared and then covalently bonded to the siloxane‐based deactivated column as the stationary phases of open‐tubular CEC with essentially high phase ratio. The EOF generated from the modified phase is surveyed through conventional aqueous buffers and hydroorganic mobile phases. Zeta potentials, which are computed from the EOF data and the ratio of dielectric constant to viscosity, are plotted as a function of pH, ionic molarity, and compositional range. These plots responsible for the electroosmotic characteristic of the bonded phases are found to be like those of bare fused‐silica or deactivated columns through decreasing or increasing the ACN content in the mobile phase, respectively. This two‐phase characteristic is basically derived from the polymeric configuration with carboxylato ligands attached onto the polysiloxane backbone. Phthalates and amino acids are suitable probes to examine the two phenomena, more‐polar and less‐polar mediums, respectively, and to judge whether the chromatographic retention is the major source of separation mechanism. With the mixing modes of Lewis acid–base interaction, dispersive force, and shape discrimination, the chromatographic partition adequately accomplishes the uneasily resolved separations by only CZE mode, although the electrophoretic migration is truly somewhat involved.
Investigation of vesicle electrokinetic chromatography as an in vitro assay for the estimation of intestinal permeability of pharmaceutical drug candidates
Authors: Pascoe Robert J. , Masucci John A. , Foley Joe P.
Published: January 2006

As the pharmaceutical industry continues the daunting search for novel drug candidates, there remains a need for rapid screening methods not only for biological activity, but for physiochemical properties as well. It is invaluable that adequate model systems for absorption and/or bioavailability be developed early in the drug evaluation process to avoid the loss of promising compounds late in development. The focus of this paper is the use of vesicle EKC (VEKC) as a high‐throughput, easy, cost‐effective, and predictive model for the passive transcellular diffusion of drug candidates in the intestinal epithelium. Vesicles are large aggregates of molecules containing a spherical bilayer structure encapsulating an internal cavity of solvent. It is this bilayer structure that makes vesicles attractive as model membranes. In this study, vesicles were synthesized from both phospholipids and surfactant aggregates, and then employed as pseudostationary phases in EKC (VEKC). The interaction of drug molecules with vesicles in EKC was then used as the basis for an in vitro assay to evaluate passive diffusion. The VEKC technique showed a statistical correlation between the retention of drug candidates using surfactant and phospholipid vesicles and passive diffusion data (log Pow and colon adenocarcinoma). VEKC analysis offers high‐throughput capabilities due to the short run times, low sample, and solvent volumes necessary, as well as instrument automation. However, due to the complexity of drug absorption in the intestine, difficulty arises when a single in vitro model is used to predict in vivo absorption characteristics. Therefore, the retention of drug candidates using VEKC in conjunction with other permeability prediction methods can provide a primary screen for a large number of drug candidates early in the drug discovery process with minimal resources.