bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol
Authors: Miura Yutaka , Satoh Toshifumi , Narumi Atsushi , Nishizawa Osamu , Okamoto Yoshio , Kakuchi Toyoji 
Published: January 2006

AbstractThe copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me6TREN) as a ligand was performed even at −78°C with a number‐average molecular weight (Mn) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured Mn's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr2) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]0/[methyl α‐bromoisobutyrate]0/[CuBr]0/[CuBr2]0/[Me6TREN]0 = 200/1/1/0.2/1.2 at −20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of CuIBr/Me6TREN in HFIP, there were [Cu(Me6TREN)Br]+ and [Cu(Me6TREN)OCH(CF3)2]+, indicating that HFIP should coordinate to the CuI/Me6TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for −78°C, 77% for −30°C, 75% for −20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006
Hydrogen bonding interactions and miscibility between phenolic resin and octa(acetoxystyryl) polyhedral oligomeric silsesquioxane (AS‐POSS) nanocomposites
Authors: Kuo Shiao‐Wei , Lin Han‐Ching , Huang Wu‐Jang , Huang Chih‐Feng , Chang Feng‐Chih 
Published: January 2006

AbstractWe have synthesized a polyhedral oligomeric silisesquioxane (POSS) derivative containing eight acetoxystyryl functional groups [octa(acetoxystyryl)octasilsesquioxane (AS‐POSS)] and then blended it with phenolic resin to form nanocomposites stabilized through hydrogen bonding interactions between the phenolic resin's hydroxyl group and the AS‐POSS derivative's carbonyl and siloxane groups. One‐ and two‐dimensional infrared spectroscopy analyses provided positive evidence for these types of hydrogen bonding interactions. In addition, we calculated the interassociation equilibrium constant, based on the Painter–Coleman association model (PCAM), between phenolic resin and POSS indirectly from the fraction of hydrogen‐bonded carbonyl groups; quantitative analyses indicate that the hydroxyl–siloxane interassociation from the PCAM is entirely consistent with the classical Coggesthall and Saier (C and S) methodology. From a thermal analysis, we observed that the miscibility between phenolic and AS‐POSS occurs at a relatively low AS‐POSS content, which characterizes this mixture as a polymer nanocomposite system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 673–686, 2006
Role of disulfide bonds in modulating internal motions of proteins to tune their function: Molecular dynamics simulation of scorpion toxin Lqh III
Authors: Moghaddam Majid Erfani , Naderi‐Manesh Hossein 
Published: January 2006

AbstractA series of 1‐ns MD simulations were performed on the scorpion toxin Lqh III in native and disulfide bond broken states. The removal of disulfide bonds has caused hydrogen bond network alteration in the five‐residue turn, the long loop, the α‐helix, the loop connecting strands II and III, and the C‐terminal region. In addition and more importantly, it has influenced the amplitude of the fluctuations of five‐residue turn, loops, and C‐terminal region with a minor effect on the fluctuations of the cysteines in the broken bond sites. These findings suggest that disulfide bonds are not the most important factors in rigidifying their own locations, while they have more important effects at a global scale. Furthermore, our results reveal that disulfide bonds have considerable influence on the functionally important essential modes of motions and the correlations between the motions of the binding site residues. Therefore, we can conclude that disulfide bonds have a crucial role in modulating the function via adjusting the dynamics of scorpion toxin molecules. Although this conclusion cannot be generalized to all peptides and proteins, it demonstrates the importance of more investigations on this aspect of disulfide bond efficacy. Proteins 2006. © 2006 Wiley‐Liss, Inc.
An overview of inherently safer design
Authors: Hendershot Dennis C. 
Published: January 2006

AbstractInherently safer product and process design represents a fundamentally different approach to safety in the manufacture and use of chemicals. The designer is challenged to identify ways to eliminate or significantly reduce hazards, rather than to develop add‐on protective systems and procedures. In the chemical process industries, risk management layers of protection are classified as inherent, passive, active, and procedural. Inherently safer design focuses on eliminating hazards, or minimizing them significantly, to reduce the potential consequence to people, the environment, property, and business. Inherently safer design is considered to be the most robust way of dealing with process risk and can be considered to be a subset of green chemistry and green engineering. It focuses on safety hazards—the immediate impacts of single events such as fires, explosions, and short‐term toxic impacts. Many of the strategies of inherently safer design are not specific to the chemical industry, but apply to a broad range of technologies. Strategies for identifying inherently safer options are discussed, with examples. However, for most facilities, a complete risk management program will include features from all categories of layers of protection. Also, the designer must be aware that all processes and materials have multiple hazards and that there can be conflicts among the risks associated with different alternatives. Design alternatives that reduce or eliminate one hazard may create or increase the magnitude of others. Recognition and understanding of these conflicts will enable the designer to make intelligent decisions to optimize the design. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006
Identification of phenolic constituents in Radix Salvia miltiorrhizae by liquid chromatography/electrospray ionization mass spectrometry
Authors: Zeng Guifeng , Xiao Hongbin , Liu Jianxun , Liang Xinmiao 
Published: January 2006

AbstractThe phenolic components from Radix Salvia miltiorrhizae Bunge, a well‐known herbal medicine (Dan‐Shen in Chinese), have been investigated by high‐performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI‐MS/MS). HPLC analyses were performed on a reversed‐phase C18 column using gradient elution. In the ESI mass spectra a predominant [M–H]− ion was observed in negative mode and provided molecular mass information. ESI‐MS/MS spectra of the [M–H]− ions were used for structural analysis, based on the spectra of standards. It was found that caffeic acid and its monomeric analogs containing a carboxyl group readily lost CO2, while dimers, trimers and tetramers of caffeic acid expelled successively danshensu or caffeic acid or their esters. Twenty‐eight phenolic compounds in S. miltiorrhizae were characterized, of which eight compounds were positively identified by comparison with standards. The remaining twenty phenolics for which standards were not available were tentatively identified based on their UV spectra and MS/MS fragmentation characteristics. Copyright © 2006 John Wiley & Sons, Ltd.
UV photodissociation of phospho‐seryl‐containing peptides: laser stabilization of the phospho‐seryl bond with multistage mass spectrometry
Authors: Lemoine Jérôme , Tabarin Thibault , Antoine Rodolphe , Broyer Michel , Dugourd Philippe 
Published: January 2006

AbstractProtonated precursor ions of phosphorylated peptides containing a tyrosyl residue have been subjected to UV laser‐induced dissociation (LID) at a wavelength of 220 nm and to collision‐induced dissociation (CID) in an ion trap. As expected, neutral loss of the phosphate group is one of the predominant fragmentation channels during CID together with H2O elimination. In contrast, LID leads mainly to the homolytic cleavage of the tyrosyl side chain and a restrained loss of the phosphate group. Interestingly, the intensity of the dephosphorylated fragment ion is greatly minimized when CID is carried out next on the radical precursor ion of the singly and doubly charged species. Copyright © 2006 John Wiley & Sons, Ltd.
A new solution for assigning cryptographic keys to control access in mobile agent environments
Authors: Chang Chin‐Chen , Lin Iuon‐Chang 
Published: January 2006

AbstractA mobile agent is a technological promising product. It is an executive program that can migrate from host to host, performing tasks autonomously. However, in an open environment, the mobile agent has many potential threats. Security becomes a critical issue for the mobile agent. Recently, Volker and Mehradad have constructed a mobile agent structure and designed a key assignment strategy to prevent the sensitive data to from being accessed by an unauthorized host. However, their scheme requires a larger agent size and a higher computational cost. In this paper, we shall propose an efficient key assignment scheme to enhance the performance of Volker and Mehradad's scheme. Only few computations and a fixed and small storage are required in our proposed scheme. Furthermore, our scheme can achieve the dynamic key management efficiently. It can also be implemented simply and practically. Copyright © 2006 John Wiley & Sons, Ltd.
A novel self‐adaptive transmission scheme over an IEEE 802.11 WLAN for supporting multi‐service
Authors: Li Changle , Li Jiandong , Cai Xuelian 
Published: January 2006

AbstractThe IEEE 802.11 wireless local area network (WLAN) media access control (MAC) specification is a hybrid protocol of random access and polling when both distributed coordination function (DCF) and point coordination function (PCF) are used. Data traffic is transmitted with the DCF, while voice transmission is carried out with the PCF. Based on the performance analysis of the MAC protocol for integrated data and voice transmission by simulation, this paper puts forward a self‐adaptive transmission scheme to support multi‐service over the IEEE 802.11 WLAN. The simulation results show that, on the premise of satisfying the maximum allowable delay of packet voice, the self‐adaptive transmission scheme can improve the data traffic performance and increase the WLAN capacity through dynamic and appropriate adjustment of the protocol parameters. Especially, voice traffic is sensitive to delay jitter, and the self‐adaptive scheme can effectively decrease it. Finally, it is worth noting that the adaptive scheme is easy to be realized, whereas no change in the MAC protocol is needed. Copyright © 2006 John Wiley & Sons, Ltd.
Performance analysis of cellular CDMA high‐speed data services
Authors: Chan Kevin K. H. , Zhuang Weihua , Yoon Young C. 
Published: January 2006

AbstractThis paper investigates the forward‐link peak and average data rates, throughput, and coverage of a cellular CDMA system for delivering high‐speed wireless data services. The analysis takes into account major aspects commonly found in the forward data channel and applies the generalized Shannon capacity formula for multi‐element antenna (MEA) systems. The study focuses on the physical layer and is flexible for various propagation environments, antenna configurations, multicode allocations, user distributions, and cell site configurations. Numerical results for various multicode allocations are presented for a system model with two‐tier interfering cells operating under a frequency selective slow fading channel with propagation environments specified in the Recommendation ITU‐R M.1225. Copyright © 2006 John Wiley & Sons, Ltd.
On efficacy of Rayleigh‐inverse Gaussian distribution over K‐distribution for wireless fading channels
Authors: Karmeshu  , Agrawal Rajeev 
Published: January 2006

AbstractFor studying performance characteristics of radio channels, the knowledge about the probability density function (pdf) of fading–shadowing effects is essential. K‐distribution corresponding to Rayleigh–gamma distribution (RGD) is widely used to approximate a more realistic Rayleigh–lognormal distribution (RLD) which does not have a closed form expression. A new composite Rayleigh‐inverse Gaussian distribution (RIGD), an alternative to K‐distribution, is analyzed with regards to its suitability and effectiveness in radio channels. Detailed investigations are made to study the performance characteristics of RIGD and K‐distribution (RGD) in terms of Kullback–Leibler (KL) measure of divergence. Based on these investigations, it is found that RIGD is better suited for capturing fading–shadowing aspects of radio channels instead of K‐distribution. Copyright © 2006 John Wiley & Sons, Ltd.
Optimal dynamic transport selection for wireless portable devices
Authors: Younis Mohamed , Sardesai Amit , Yesha Yaacov 
Published: January 2006

AbstractRecent technological advances in mobile computing and wireless communication have made portable devices, such as PDA, laptops, and wireless modems to be very compact and affordable. On the other hand, wireless networks have gained such wide popularity that new network infrastructure is continually introduced. It is thus likely that many of the future portable devices will be equipped with multiple wireless modems such as Bluetooth and 802.11 WLAN, in order to increase device inter‐operability. The availability of multiple modems can leverage the performance of the communication traffic generated by the applications, for example Internet access. We envision a tool for managing the device connection through these modems. At the core of this tool is an optimization engine that splits packet traffic across a subset of the available transports so that user's performance metrics are maximized. This paper describes a mathematical model for such an optimization problem considering its applicability to small portable devices. Relevant quality of service (QoS) parameters such as bandwidth, average delay, and energy consumption are covered in the model. The mathematical formulation is validated using a simulated environment. The experimental results have demonstrated the effectiveness of our model and captured the inter‐relationship among the quality parameters. Copyright © 2006 John Wiley & Sons, Ltd.
Demand‐driven server and service location in third generation mobile networks
Authors: Mateus Geraldo Robson , Goussevskaia Olga , Loureiro Antonio A. F. 
Published: January 2006

AbstractIn this paper, we formulate and solve the problem of how to dynamically distribute network resources in third‐generation mobile telecommunication systems, aiming to minimize the equipment maintenance and service provision costs. A mobility simulator was implemented in order to represent a hypothetical city, which was populated with different groups of users, whose mobility behavior and demand for different kinds of services was generated in order to simulate a typical 24‐h day behavior. Given the generated demand at a certain period of time, a server allocation is made in order to attend it. This is done by modeling the system as an integer‐programming problem and by, afterwards, running an optimization algorithm on it. The output from the optimization process was used to reconfigure the system by activating the selected servers and deactivating the others. The problem turned out to be NP‐hard, so a heuristic method was necessary in order to solve it. We chose the Lagrangean relaxation technique to do the task, and obtained good results in terms of the solution proximity to the optimum. The performed experiments demonstrated the model's sensitivity to different kinds of parameters, such as user mobility, demand distribution over time and space, time of day, type of area where events occur, and the relation between fixed and variable costs of the system. A significant system cost reduction was also achieved. The proposed approach allows a personalized and demand driven resource distribution. Copyright © 2006 John Wiley & Sons, Ltd.
A performance evaluation of distributed dynamic channel allocation protocols for mobile networks
Authors: Boukerche Azzedine , El‐Khatib Khalil , Huang Tingxue 
Published: January 2006

AbstractTechnological advances coupled with the proliferation of wireless devices among mobile users require efficient resource management and reuse of the scare radio spectrum allocated to wireless and mobile communication systems. Several channel allocation protocols based on a mutual exclusion paradigm have been developed. However, very little data have been reported to compare these protocols. In this paper, we review four of the best known distributed dynamic channel and resource allocation algorithms based on the mutual exclusion paradigm. While the first three channel alloctaion protocols (Caoet al., Choyet al. and Prakashet al.) are based on the co‐channel interference, the fourth protocol, which is known as DDRA, adopts the co‐group interference approach. We present an extensive set of simulation experiments to evaluate and compare the performance of these four protocols using realistic scenarios. Our results indicate clearly that DDRA algorithm has shown the shortestresponse timeand highestblocking rateamong all of the four channel allocation protocols. Caoet al. algorithm exhibits a betterblocking ratewhen compared to the three other schemes. This is due to the fact that it reuses communication channels optimally. Last, but not least, we discuss the basic fault tolerant machanisms that can be used to enhance further these protocols while dealing with the base stations, mobile hosts, or links' failure. Copyright © 2006 John Wiley & Sons, Ltd.
EM‐based iterative receiver for coded MIMO systems in unknown spatially correlated noise
Authors: Mo Wei , Wang Zhengdao , Dogandžić Aleksandar 
Published: January 2006

AbstractWe present iterative channel estimation and decoding schemes for multi‐input multi‐output (MIMO) Rayleigh block fading channels in spatially correlated noise. An expectation‐maximization (EM) algorithm is utilized to find the maximum likelihood (ML) estimates of the channel and spatial noise covariance matrices, and to compute soft information of coded symbols which is sent to an error‐control decoder. The extrinsic information produced by the decoder is then used to refine channel estimation. Several iterations are performed between the above channel estimation and decoding steps. We derive modified Cramer–Rao Bound (MCRB) for the unknown channel and noise parameters, and show that the proposed EM‐based channel estimation scheme achieves the MCRB at medium and high SNRs. For a bit error rate of 10−6and long frame length, there is negligible performance difference between the proposed scheme and the ideal coherent detector that utilizes the true channel and noise covariance matrices. Copyright © 2006 John Wiley & Sons, Ltd.
Sphingolipids differentially regulate mitogen‐activated protein kinases and intracellular Ca2+in vascular smooth muscle: effects on CREB activation
Authors: Mathieson Fiona A , Nixon Graeme F 
Published: January 2006

Related sphingolipids, sphingosine 1‐phosphate (S1P) and sphingosylphosphorylcholine (SPC), have important effects on vascular smooth muscle. The aim of this study was to investigate the intracellular pathways regulated by S1P and SPC in rat cerebral artery.In cerebral arteries, S1P increased extracellular signal‐regulated kinase (ERK)1/2 phosphorylation (5.2±1.4‐fold increase) but did not activate p38 mitogen‐activated protein kinase (p38MAPK) as assessed by immunoblotting. In contrast, SPC increased p38MAPK phosphorylation (3.0±0.3‐fold increase) but did not stimulate ERK1/2. This differential activation was confirmed by measuring activation of heat shock protein (HSP) 27, a known downstream target of p38MAPK. Only SPC, but not S1P, activated HSP27.In enzymatically dispersed cerebral artery myocytes, SPC increased [Ca2+]iin a concentration‐dependent manner (peak response at 10 μM: 0.4±0.02 ratio units) as determined using the Ca2+indicator, Fura 2. In contrast to S1P, the SPC‐induced [Ca2+]iincrease did not involve intracellular release but was due to Ca2+influxviaL‐type Ca2+channels.Despite differences in signalling, both S1P and SPC phosphorylated the transcription factor cAMP response element‐binding protein (CREB). S1P‐induced CREB activation was dependent on ERK1/2 and Ca2+‐calmodulin‐dependent protein kinase (CaMK) activation. CREB activation by SPC required both p38MAPK and CaMK activation, but not ERK1/2.In conclusion, S1P and SPC activate distinct MAP kinase isoforms and increase [Ca2+]iviadifferent mechanisms in rat cerebral artery. This does not affect the ability of S1P or SPC to activate CREB, although this occursviadifferent pathways.British Journal of Pharmacology(2006)147, 351–359. doi:10.1038/sj.bjp.0706600
Agonist activity of naloxone benzoylhydrazone at recombinant and native opioid receptors
Authors: Olianas Maria C , Concas Danilo , Onali Pierluigi 
Published: January 2006

In the present study, we examined the pharmacological activity of the putativeκ3‐opioid receptor agonist naloxone benzoylhydrazone (NalBzoH) at recombinant human opioid receptors individually expressed in Chinese hamster ovary (CHO) cells and native opioid receptors present in rat striatum.At theμ‐opioid receptor (MOR), NalBzoH stimulated guanosine‐5′‐O‐(3‐[35S]thio)triphosphate ([35S]GTPγS) binding (pEC50=8.59) and inhibited cyclic AMP accumulation (pEC50=8.74) with maximal effects (Emax) corresponding to 55 and 65% of those obtained with the MOR agonist DAMGO, respectively. The MOR antagonist CTAP blocked the stimulatory effects of NalBzoH and DAMGO with similar potencies.At theκ‐opioid receptor (KOR), NalBzoH stimulated [35S]GTPγS binding (pEC50=9.70) and inhibited cyclic AMP formation (pEC50=9.45) as effectively as the selective KOR agonist (−)‐U‐50,488. The NalBzoH effect was blocked by the KOR antagonist nor‐binaltorphimine (nor‐BNI) (pKi=10.30).In CHO cells expressing theδ‐opioid receptor (DOR), NalBzoH increased [35S]GTPγS binding (pEC50=8.49) and inhibited cyclic AMP formation (pEC50=8.61) almost as effectively as the DOR agonist DPDPE. Naltrindole (NTI), a selective DOR antagonist, completely blocked the response to NalBzoH (pKiof 10.40).In CHO cells expressing the nociceptin/orphanin FQ (N/OFQ) receptor (NOP), NalBzoH failed to exert agonist effects and antagonized the agonist‐induced receptor activation.When compared to other opioid receptor ligands, NalBzoH showed an efficacy that was lower than that of morphine at MOR, but higher at KOR and DOR.In rat striatum, NalBzoH enhanced [35S]GTPγS binding and inhibited adenylyl cyclase activity. These effects were antagonized by either CTAP, nor‐BNI or NTI, each antagonist blocking a fraction of the NalBzoH response.These data demonstrate that NalBzoH displays agonist activity at MOR, DOR and KOR expressed either in a heterologous cell system or in a native environment.British Journal of Pharmacology(2006)147, 360–370. doi:10.1038/sj.bjp.0706601