bluuebunny/crossref_metadata_2025 huggingface dataset:
Thallium Determination at the Single Picomole per Liter Level by Flow‐Injection Differential‐Pulse Anodic Stripping Voltammetry
Authors: Jakubowska Monika , Zembrzuski Wlodzimierz , Lukaszewski Zenon
Published: April 2008

The flow‐injection differential‐pulse anodic stripping voltammetric (FI‐DP‐ASV) procedure has been developed for the determination of thallium concentration of the order of the single pM. Due to the analyte preconcentration at the electrode, DPASV is among the leaders in competition for achieving a detection limit as low as possible. The enrichment factor can be easily regulated by the duration of the preconcentration time. A DPASV measurement in a flow‐injection system enables the circulation of an analyzed sample and a medium exchange when preconcentration is completed. This approach ensures significant improvement of a background current. The measurements were performed in a cell of the wall‐jet type containing the mercury film electrode. One hour preconcentration was used for the determination of the lowest thallium concentrations. The developed method provides the opportunity to determine thallium in real environmental samples at the single pM level with the detection limit equal to 0.25 pM and RSD equal to 8.2%. This is by more than one order of magnitude better than the lowest detection limit reported in the literature (5 pM). Additionally, the medium exchange resulted in the improvement of the measuring accuracy, which was evidenced by the application of a certified reference material.
Acetylferrocene Modified Carbon Paste Electrode; A Sensor for Electrocatalytic Determination of Hydrazine
Authors: Ojani Reza , Raoof Jahan‐Bakhsh , Norouzi Banafsheh
Published: April 2008

The electrocatalytic oxidation of hydrazine at a carbon paste electrode spiked with acetylferrocene as a mediator was studied by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. In contrast to other ferrocenic compounds, acetylferrocene exhibits a chemical irreversible behavior, but it can act as an effective mediator for electrocatalytic oxidation of hydrazine, too. The heterogeneous electron transfer rate constant between acetylferrocene and the electrode substrate (carbon paste) and the diffusion coefficient of spiked acetylferrocene in silicon oil were estimated to be about 3.45×10−4 cm s−1 and 4.45×10−9 cm2 s−1, respectively. It has been found that under the optimum conditions (pH 7.5) the oxidation of hydrazine occurs at a potential of about 228 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak current of hydrazine was linearly dependent on its concentration and the obtained linear range was 3.09×10−5 M–1.03×10−3 M. The detection limit (2σ) has been determined as 2.7×10−5 M by cyclic voltammetry. Also, the peak current was increased linearly with the concentration of hydrazine in the range of 1×10−5 M–1×10−3 M by differential pulse voltammetry with a detection limit of 1×10−5 M. This catalytic oxidation of hydrazine has been applied as a selective, simple, and precise new method for the determination of hydrazine in water samples.
Voltammetric Reduction of a 4‐Nitroimidazole Derivative on a Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrode
Authors: Jara‐Ulloa P. , Bollo S. , Núñez‐Vergara L. J. , Squella J. A.
Published: April 2008

We report the electrochemical behavior of a 4‐nitroimidazole derivative, 1‐methyl‐4‐nitro‐2‐hydroxymethylimidazole (4‐NImMeOH), on glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNT). As dispersing agents, dimethylformamide (DMF) and water were used. The electrochemical response of the resulting electrodes was evaluated using linear sweep, cyclic and square‐wave voltammetry (LSV, CV and SWV). Several parameters such as medium pH, nature and concentration of the CNTs dispersion and accumulation time were tested. The optimal conditions determined for obtain better response were: pH 2, dispersion concentration=4 mg/mL of CNT in water, accumulation time=7 min. The MWCNT‐modified GCE exhibited attractive electrochemical properties producing enhanced currents with a significant reduction in the overpotential and good signal‐to‐noise characteristics, in comparison with the bare GCE. The modified electrode is highly repeatable for consecutive measurements, reaching a variation coefficient of 2.9% for ten consecutive runs.
The primate palette: The evolution of primate coloration
Authors: Bradley Brenda J. , Mundy Nicholas I.
Published: April 2008

Flip through The Pictorial Guide to the Living Primates1 and you will notice a striking yet generally underappreciated aspect of primate biology: primates are extremely colorful. Primate skin and pelage coloration were highlighted examples in Darwin's2 original discussions of sexual selection but, surprisingly, the topic has received little research attention since. Here we summarize the patterns of color variation observed across the primate order and examine the selective forces that might drive and maintain this aspect of primate phenotypic diversity. We discuss how primate color patterns might be adaptive for physiological function, crypsis, and communication. We also briefly summarize what is known about the genetic basis of primate pigmentation and argue that understanding the proximate mechanisms of primate coloration will be essential, not only for understanding the evolutionary forces shaping phenotypic variation, but also for clarifying primate taxonomies and conservation priorities.
Citrinin induces apoptosis in mouse embryonic stem cells
Authors: Chan Wen‐Hsiung
Published: April 2008

The mycotoxin citrinin (CTN) is a natural contaminant in foodstuffs and animal feeds, and exerts cytotoxic and genotoxic effects on various mammalian cells. CTN causes cell injury, including apoptosis. However, its precise regulatory mechanisms of action, particularly in stem cells and embryos, are currently unclear. Recent studies show that CTN has cytotoxic effects on mouse embryonic stem cells and blastocysts, and is associated with defects in their subsequent development, both in vitro and in vivo. Experiments with the embryonic stem cell line, ESC‐B5, disclose that CTN induces apoptosis via several mechanisms, including ROS generation, increased cytoplasmic free calcium levels, intracellular nitric oxide production, enhanced Bax/Bcl‐2 ratio, loss of mitochondrial membrane potential, cytochrome c release, activation of caspase‐9 and caspase‐3, and p21‐activated protein kinase 2 and c‐Jun N‐terminal protein kinase activation. Additional studies show that CTN promotes cell death via inactivation of the HSP90/multi‐chaperone complex and subsequent degradation of Ras and Raf‐1, further inhibiting anti‐apoptotic processes such as the Ras→ERK signal transduction pathway. On the basis of these findings, we propose a model for CTN‐induced cell injury signalling cascades in embryonic stem cells and blastocysts. © 2008 IUBMB IUBMB Life, 60(3): 171–179, 2008
Multidomain STS/TULA proteins are novel cellular regulators
Authors: Tsygankov Alexander Y.
Published: April 2008

Proteins of the STS/TULA family recently emerged as important regulators of cellular functions. They exhibit a unique domain architecture, featuring at least three interactive/functional domains. Despite a significant degree of homology between the two members of this family, there are considerable functional differences between them. Thus, one of them is ubiquitously expressed in mammalian tissues and exhibits high phosphatase activity, whereas the other one is expressed in lymphocytes only and exhibits very low phosphatase activity, but is capable of promoting apoptosis, an activity unique for this family member. Among several functions reported for STS/TULA proteins, the most characterized one is the regulation of protein tyrosine kinase‐mediated signaling. Interestingly, gene deletion of neither family member results in a discernible phenotype, whereas simultaneous deletion of both members causes hyperreactivity of T cells. Despite their apparent importance, the physiological role and the molecular basis of the effects of STS/TULA proteins remain poorly understood. This brief review summarizes what is currently known about the STS/TULA family and outlines the unresolved questions in this area. © 2008 IUBMB IUBMB Life, 60(4): 224–231, 2008
Eukaryotic selenoprotein synthesis: Mechanistic insight incorporating new factors and new functions for old factors
Authors: Squires Jeffrey E. , Berry Marla J.
Published: April 2008

Selenium is an essential micronutrient that has been linked to various aspects of human health. Selenium exerts its biological activity through the incorporation of the amino acid, selenocysteine (Sec), into a unique class of proteins termed selenoproteins. Sec incorporation occurs cotranslationally at UGA codons in archaea, prokaryotes, and eukaryotes. UGA codons specify Sec coding rather than termination by the presence of specific secondary structures in mRNAs termed selenocysteine insertion (SECIS) elements, and trans‐acting factors that associate with SECIS elements. Herein, we discuss the various proteins known to function in eukaryotic selenoprotein biosynthesis, including several players whose roles have only been elucidated very recently. © 2008 IUBMB IUBMB Life, 60(4): 232–235, 2008
Resveratrol: One molecule, many targets
Authors: Pirola Luciano , Fröjdö Sara
Published: April 2008

Resveratrol is one of the numerous polyphenolic compounds found in several vegetal sources. In recent years, the interest in this molecule has increased exponentially following the major findings that resveratrol (i) is shown to be chemopreventive in some cancer models, (ii) is cardioprotective, and (iii) has positive effects on several aspects of metabolism, leading to increased lifespan in all the metazoan models tested thus far, including small mammals. Such remarkable properties have elicited a vast interest towards the identification of target proteins of resveratrol and have led to the identification of enzymes inhibited by resveratrol and others whose activation is enhanced. In the vast majority of cases, resveratrol displays inhibitory/activatory effects in the micromolar range, which is potentially attainable pharmacologically, although targets with affinities in the nanomolar range have also been reported. Here, we provide an overview of the various classes of enzymes known to be inhibited (or activated) by resveratrol. It appears that resveratrol, as a pharmacological agent, has a wide spectrum of targets. The biological activities of resveratrol may thus be dependent on its simultaneous activity on multiple molecular targets. © 2008 IUBMB IUBMB Life, 60(5): 323–332, 2008
Trapping of human DNA topoisomerase I by DNA structures mimicking intermediates of DNA repair
Authors: Lebedeva Natalia , Rechkunova Nadejda , Boiteux Serge , Lavrik Olga
Published: April 2008

In this report we show that human DNA Topoisomerase I (Top1) forms DNA‐protein adducts with nicked and gapped DNA structures lacking a conventional Top1 cleavage site. The radioactively labeled crosslinking products were identified by SDS‐gel electrophoresis. The chemical structure of the groups at 5′ or 3′ end of the nick does not have an effect on the formation of these covalent adducts. Therefore, all kinds of nicks, either directly induced by ionizing radiation or reactive oxygen species or indirectly induced in the course of base excision repair (BER) are targets for Top1 that competes with BER proteins and other nick‐sensors. Top1‐DNA covalent adducts formed in cells exposed to DNA damaging agents can promote genetic instability. © 2008 IUBMB IUBMB Life, 60(2): 130–134, 2008
Mechanisms of aging and energy metabolism in Caenorhabditis elegans
Authors: Artal‐Sanz Marta , Tavernarakis Nektarios
Published: April 2008

Aging studies on diverse species ranging from yeast to man have culminated in the delineation of several signaling pathways that influence the process of senescent decline and aging. While understanding these interlinked signal‐transduction cascades is becoming even more detailed and comprehensive, the cellular and biochemical processes they impinge upon to modulate the rate of senescent decline and aging have lagged considerably behind. This fundamental question is one of the most important challenges of modern aging research and has been the focus of recent research efforts. Emerging findings provide insight into the facets of cellular metabolism which can be fine‐tuned by upstream signaling events to ultimately promote longevity. Here, we survey the mechanisms regulating aging in the simple nematode worm Caenorhabditis elegans, aiming to highlight recent discoveries that shed light into the interface between aging signaling pathways and cellular energy metabolism. Our objective is to review the current understanding of the processes involved and discuss mechanisms that are likely conserved in higher organisms. © 2008 IUBMB IUBMB Life, 60(5): 315–322, 2008
Thermo‐triggered and biotinylated biotin‐P(NIPAAm‐co‐HMAAm)‐b‐PMMA micelles for controlled drug release
Authors: Cheng Cheng , Wei Hua , Zhang Xian‐Zheng , Cheng Si‐Xue , Zhuo Ren‐Xi
Published: April 2008

Thermosensitive and biotinylated biotin‐poly (N‐isopropylacrylamide‐co‐N‐hydroxymethylacrylamide)‐block‐poly(methyl methacrylate) (biotin‐P(NIPAAm‐co‐HMAAm)‐b‐PMMA) block copolymers were designed and synthesized. The conjugation of biotin molecule with the copolymer as well as the capability of easily functionalizing with ligands for pretargeting approach of the biotinylated multifunctional drug carrier was confirmed by a novel method called capillary electrophoresis immunoassay (CEIA) based on enhanced chemiluminescence (CL) detection. The biotin‐P(NIPAAm‐co‐HMAAm)‐b‐PMMA copolymer was capable of self‐assembling into nanometer‐sized micelle. The anticancer drug methotrexate (MTX), used as a model drug, was loaded in the self‐assembled micelles and the thermo‐triggered release behavior of MTX was investigated. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Long‐term evaluation of blood silicon and ostecalcin in operatively treated patients with benign bone tumors using bioactive glass and autogenous bone
Authors: Lindfors N. C. , Heikkilä J. T. , Aho A. J.
Published: April 2008

In a study on 25 patients with verified benign bone tumors, bioactive glass (BG) and autogenous bone (AB) were used as bone‐graft substitutes. The patients were randomized into two groups according to the filling material. Blood samples were taken both preoperatively, at 2 weeks, and 3, 8, 12, 24, and 36 months postoperatively, for evaluation of silicon concentration in blood. In the determination, direct current plasma atomic emission spectroscopy was used. No significant difference in blood silicon concentration between the BG group or the AB group could statistically be observed (p = 0.5400), and neither did the size of the bone tumor (p = 0.4259) nor the follow‐up time affect the results (p = 0.2094). Concentration of osteocalcin in blood was significantly higher for large cysts (p < 0.0001). The filler material (BG or AB) did not affect the osteocalcin concentration level in blood. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Using support vector machine to predict β‐ and γ‐turns in proteins
Authors: Hu Xiuzhen , Li Qianzhong
Published: April 2008

By using the composite vector with increment of diversity, position conservation scoring function, and predictive secondary structures to express the information of sequence, a support vector machine (SVM) algorithm for predicting β‐ and γ‐turns in the proteins is proposed. The 426 and 320 nonhomologous protein chains described by Guruprasad and Rajkumar (Guruprasad and Rajkumar J. Biosci 2000, 25,143) are used for training and testing the predictive model of the β‐ and γ‐turns, respectively. The overall prediction accuracy and the Matthews correlation coefficient in 7‐fold cross‐validation are 79.8% and 0.47, respectively, for the β‐turns. The overall prediction accuracy in 5‐fold cross‐validation is 61.0% for the γ‐turns. These results are significantly higher than the other algorithms in the prediction of β‐ and γ‐turns using the same datasets. In addition, the 547 and 823 nonhomologous protein chains described by Fuchs and Alix (Fuchs and Alix Proteins: Struct Funct Bioinform 2005, 59, 828) are used for training and testing the predictive model of the β‐ and γ‐turns, and better results are obtained. This algorithm may be helpful to improve the performance of protein turns' prediction. To ensure the ability of the SVM method to correctly classify β‐turn and non‐β‐turn (γ‐turn and non‐γ‐turn), the receiver operating characteristic threshold independent measure curves are provided. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Unusual Sb–Sb bonding in high temperature thermoelectric materials
Authors: Xu Jianxiao , Kleinke Holger
Published: April 2008

The emerging families of advanced thermoelectrics are dominated by antimonides and tellurides. Because the structures of the tellurides are mostly composed of NaCl‐related motifs, they do not contain any Te–Te bonds, and all of the antimonide structures exhibit Sb–Sb bonds of various lengths. Taking all Sb–Sb distances shorter than 3.2 Å into account, the Sb atom substructures are Sb24− pairs in β‐Zn4Sb3, linear Sb37− units in Yb14MnSb11, planar Sb44− rectangles in the skutterudites, for example, LaFe3CoSb12, and Sb8 cubes interconnected via short Sb–Sb bonds to a three‐dimensional network in Mo3Sb5Te2. These interactions have a significant impact on the band gap size as well as on the effective mass around the Fermi level, for the bottom of the conduction band is in all cases predominated by antibonding Sb–Sb interactions, and—in some cases—the top of the valence band by bonding Sb–Sb interactions. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Are Ba11Cd6Sb12 and Sr11Cd6Sb12 Zintl phases or not? A density‐functional theory study
Authors: Xia Sheng‐Qing , Bobev Svilen
Published: April 2008

The chemical bonding and the electronic band structures of two isoelectronic and isostructural Zintl compounds, Sr11Cd6Sb12 and Ba11Cd6Sb12, have been studied on the basis of the density‐functional theory (DFT) using the tight‐binding linear‐muffin‐tin‐orbital (TB‐LMTO‐ASA) approach and the local‐density approximation (LDA). These results reveal that the classic Zintl reasoning and the concept of two‐center two‐electron bonds cannot explain the subtleties of this complex structure type. The computations also suggest that the antimony dimers present in these structures play an important role and allow for a greater flexibility in optimization of the bonding with the surrounding d‐metal atoms. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Exploring the conformational space of Vpu from HIV‐1: A versatile adaptable protein
Authors: Krüger Jens , Fischer Wolfgang B.
Published: April 2008

The dynamic behavior of monomeric Vpu1‐32 from HIV‐1 in different lipid environments has been studied. The peptide shows highly flexible behavior during the simulations and easily adapts to changing lipid environments as it experiences when travelling through the Golgi apparatus. Protein–lipid interactions do not show any significant correlation towards lipid type or thickness based on multiple 10 ns simulations. The averaged structure of a series of 16 independent simulations suggest kink around Ser‐24, which compensates the polarity of its side chain by forming hydrogen bonds with the carbonyl backbone of adjacent amino acids towards the N‐terminus. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008.
Branchial arch muscle innervation by the glossopharyngeal (IX) and vagal (X) nerves in Tetraodontiformes, with special reference to muscle homologies
Authors: Nakae Masanori , Sasaki Kunio
Published: April 2008

Branchial arch muscle innervation by the glossopharyngeal (IX) and vagal (X) nerves in 10 tetraodontiform families and five outgroup taxa was examined, with special reference to muscle homologies. Basic innervation patterns and their variations were described for all muscle elements (except gill filament muscles). In the tetraodontids Takifugu poecilonotus and Canthigaster rivulata, diodontid Diodon holocanthus, and molid Mola mola, levator externus 4 was innervated by the 3rd vagal branchial trunk (BX3) in addition to BX2, owing to strong posterior expansion of the muscle. Based on nerve innervation, migrations of the muscle attachment sites (i.e., origins and insertions) were recognized in levator internus 2 (in Mola mola), obliquus dorsalis 3 (in Ostracion immaculatus and Canthigaster rivulata), and obliquus ventralis 2 (in Stephanolepis cirrhifer), muscle topologies not necessarily being indicative of homologies. Embryonic origin of the retractor dorsalis and parallel attainment of the swimbladder muscle within the order were also discussed. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.
Promotion of neuronal differentiation through activation of N‐methyl‐D‐aspartate receptors transiently expressed by undifferentiated neural progenitor cells in fetal rat neocortex
Authors: Yoneyama Masanori , Nakamichi Noritaka , Fukui Masaki , Kitayama Tomoya , Georgiev Danko D. , Makanga Juliet O. , Nakamura Nobuhiro , Taniura Hideo , Yoneda Yukio
Published: April 2008

Neural progenitor cell is a generic term for undifferentiated cell populations composed of neural stem, neuronal progenitor, and glial progenitor cells with abilities for self‐renewal and multipotentiality. In this study, we have attempted to evaluate the possible functional expression of N‐methyl‐D‐aspartate (NMDA) receptors by neural progenitor cells prepared from neocortex of 18‐day‐old embryonic rats. Cells were cultured in the presence of basic fibroblast growth factor (bFGF) for different periods up to 12 days under floating conditions. Reverse transcription‐polymerase chain reaction and fluorescence imaging analyses revealed transient expression of functional NMDA receptors in neurospheres formed by clustered progenitors during the culture with bFGF. A similarly potent increase was seen in the fluorescence intensity after brief exposure to NMDA in cells differentiated after the removal of bFGF under adherent conditions, and an NMDA receptor antagonist invariably prevented these increases by NMDA. Moreover, sustained exposure to NMDA not only inhibited the formation of neurospheres when exposed for 10 days from day 2 to day 12 but also promoted spontaneous and induced differentiation of neurospheres to cells immunoreactive for a neuronal marker protein on immunocytochemistry and Western blotting analyses. These results suggest that functional NMDA receptors may be transiently expressed to play a role in mechanisms underlying the modulation of proliferation along with the determination of subsequent differentiation fate toward a neuronal lineage in neural progenitor cells of developing rat neocortex. © 2008 Wiley‐Liss, Inc.
Soil degradation and soil surface process intensities on abandoned fields in Mediterranean mountain environments
Authors: Seeger M. , Ries J. B.
Published: April 2008

The Pyrenean and Pre‐Pyrenean mountain areas have been intensively used at least since roman times, but nowadays depopulation has lead to widespread land abandonment without a steering land‐management. Vegetation recovery is weak in most abandoned fields. Soil formation and characteristics are conditioned by this fact, and for this, soils show past degradation processes and are mostly predominant factors for continuing land degradation or restoration. Three study areas were set up along a climatic gradient with increasing summer water deficit in the sub‐humid zone between the Central Pyrenees and Pre‐Pyrenees. Soil survey combined with experiments for the determination of infiltration, runoff and erosion were applied for understanding the degradation history and the future development of the soils. All areas are dominated by Entisols, but also Inceptisols and Alfisols are found, and even soils with hydromorphic features. The soils show signs of heavy erosion. The parental material determines the nutrient supply and the general chemical properties. All sites show a weak water storing capacity, as a result of the removal of fine material by erosion and due to the depletion of soil organic matter. In addition, infiltration capacity and runoff generation are high within the studied areas, averaging between 27 and 37 per cent. The driest area studied shows an ongoing trend to degradation, with high erosion rates combined with a high degradations status of the soil. The other areas are characterised by a patchy pattern of soil degradation and regradation processes. Copyright © 2008 John Wiley & Sons, Ltd.
Spectral line‐by‐line shaping for optical and microwave arbitrary waveform generations
Authors: Huang Chen‐Bin , Jiang Zhi , Leaird DanielE. , Caraquitena José , Weiner AndrewM.
Published: April 2008

Spectral line‐by‐line shaping is a key enabler towards optical arbitrary waveform generation, which promises broad impact both in optical science and technology. In this paper, generation of optical and microwave arbitrary waveforms using the spectral line‐by‐line shaping technique is reviewed. Compared to conventional pulse shaping, significant new physics arises in the line‐by‐line regime, where the shaped pulse fields generated from one laser pulse now overlap with those generated from adjacent pulses. This leads to coherent interference effects related to the properties of optical frequency combs which serve as the source in these experiments. We explore such effects in a series of experiments using several different high‐repetition‐rate optical combs, including harmonically mode‐locked lasers and continuous‐wave lasers that are externally phase modulated either with or without the help of an optical cavity. As an application of line‐by‐line pulse shaping, we describe generation of microwave electrical arbitrary waveforms that can be reprogrammed at rates approaching 10 GHz.
in vitro Biological Evaluation of Folate‐Functionalized Block Copolymer Micelles for Selective Anti‐Cancer Drug Delivery
Authors: Licciardi Mariano , Craparo Emanuela F. , Giammona Gaetano , Armes Steven P. , Tang Yiqing , Lewis Andrew L.
Published: April 2008

The main objective of this study was to evaluate the ability of folic acid‐functionalized diblock copolymer micelles to improve the delivery and uptake of two poorly water‐soluble anti‐tumor drugs, tamoxifen and paclitaxel, to cancer cells through folate receptor targeting. The diblock copolymer used in this study comprised a hydrophilic poly[2‐(methacryloyloxy)ethyl phosphorylcholine] (MPC) block, carrying at the chain end the folate targeting moiety, and a pH‐sensitive hydrophobic poly[2‐(diisopropylamino)ethyl methacrylate] (DPA) block (FA–MPC–DPA). The drug‐loading capacities of tamoxifen‐ and paclitaxel‐loaded micelles were determined by high performance liquid chromatography and the micelle dimensions were determined by dynamic light scattering and transmission electron microscopy. Cell viability studies were carried out on human chronic myelogenous leukaemia (K‐562) and colon carcinoma cell lines (Caco‐2) in order to demonstrate that drug‐loaded FA–MPC–DPA micelles exhibited higher cytotoxicities toward cancer cells than unfunctionalized MPC‐DPA micelles. Uptake studies confirmed that folate‐conjugated micelles led to increased drug uptake within cancer cells, demonstrating the expected selectivity toward these tumor cells.

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Size Effect of Al2O3 Nanowires on the Molecular Relaxation in Epoxy Composites
Authors: Wan Wei‐Tao , Yu De‐Mei , Huang Long‐Biao , Xie Yun‐Chuan , Guo Xiu‐Sheng , Zhang Jing
Published: April 2008

The size effect of Al2O3 nanowires on the molecular relaxation of an epoxy system was investigated by means of DSC and dielectric relaxation spectroscopy. Tg and activation energy of dielectric relaxation decreased with the incorporation of the nanowires. To explain the observed results, a coarse‐grained confined‐region structure model is proposed, and on the basis of this model, the change in molecular motion arising from the nanowires could be understood. The variations of thermal stability and water absorption for the nanocomposites were also discussed. These original experimental results should be helpful in scientific research and nanocomposite applications.

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Novel Cationic RAFT‐Mediated Polystyrene/Clay Nanocomposites: Synthesis, Characterization, and Thermal Stability
Authors: Samakande Austin , Juodaityte J. J. , Sanderson Ronald D. , Hartmann Patrice C.
Published: April 2008

Two novel cationic RAFT agents, PCDBAB and DCTBAB, were anchored onto MMT clay to yield RAFT‐MMT clays. The RAFT‐MMT clays were then dispersed in styrene where thermal self‐initiation polymerization of styrene to give rise to exfoliated PS/clay nanocomposites occurred. The RAFT agents anchored onto the clay layers successfully controlled the polymerization process resulting in controlled molecular masses and narrow polydispersity indices. The nanocomposites prepared showed enhanced thermal stability, which was a function of the clay loading, clay morphology, and slightly on molecular mass.

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Direct Generation of Polymer Films on Copper Surfaces through Azide‐Alkyne Cycloaddition Reactions between Peptidomimetic Oligomers
Authors: Shah Neel H. , Kirshenbaum Kent
Published: April 2008

N‐substituted glycine oligomers, or peptoids, can be used in conjunction with the copper‐catalyzed [3 + 2] cycloaddition of azides and alkynes to generate branched polymer networks. By incorporating both azides and alkynes as side chain functionalities on the oligomer scaffolds, peptoids are able to form cross‐linked macromolecular products. The oligomer starting materials are readily associated onto copper metal sheets, allowing for localized cross‐link proliferation which in turn generates thin film polymer coatings. This novel procedure provides a direct method for the chemical modification of metal surfaces and the formation of mechanically robust sequence‐specific polymer networks.

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A compact combline bandpass filter designed in LTCC
Authors: Yang Tao , Xu Ruimin , Xiao Lan
Published: April 2008

A compact combline bandpass filter structure using low temperature cofired ceramic (LTCC) technology is proposed. The lumped capacitance in traditional combline filter structure is changed to distributed capacitance realized by parallel coupled strip‐lines in LTCC layers. A bandpass filter with this structure is designed, fabricated, and tested in this article. The theoretical and experimental results are presented. The two results match each other well. The results show a relative band width of 5% with the center frequency at 9.6 GHz and a very high suppression out of band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1897–1900, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23475
5.8 GHz orientation‐specific extruded‐fin heatsink antennas for 3D RF system integration
Authors: Covert Lance , Lin Jenshan , Janning Dan , Dalrymple Thomas
Published: April 2008

In high‐power RF transmitter applications, the heatsink can be used as an antenna for improved antenna performance and increased integration. Extruded‐fin heatsink antennas designed at 5.8 GHz are orientation‐specific when the heatsink base replaces the patch of a patch antenna. In this case, the orientation of the fins with respect to the patch edges plays a significant role in the antenna performance and must be considered. The results show that the heatsink antenna using a lossy, low‐cost FR4 substrate increases the bandwidth from 3.1 to 17.6% and radiation efficiency from 62 to 87% compared with the patch antenna on the same substrate. Also, the orientation has a significant effect on the directivity, gain, and radiation pattern. By combining two functions into one structure, the component count in a system is reduced and the antenna performance can be improved. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1826–1831, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23478
Band notched ultra wideband internal antenna for USB dongle application
Authors: Jung Jinwoo , Lee Hyeonjin , Lim Yeongseog
Published: April 2008

A novel band notched UWB antenna for USB dongle application is demonstrated experimentally and numerically. By embedding an ellipse cutting in the antenna's radiator, an ultra‐wideband property is achieved. To create a band notched characteristic, stub lines are employed in the antenna. The antenna is printed on the top portion of the ground plane, and can be considered as a circuit board of a practical USB Dongle. The dimensions of the antenna are 12.5 mm × 13.5 mm. The antenna has a notched band of 5.15 to 5.84 GHz while maintaining UWB performance. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1789–1793, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23480
Wideband circularly polarized microstrip antenna array using a new single feed network
Authors: Nasimuddin  , Chen Zhi Ning , Esselle K. P.
Published: April 2008

A new single feed system is presented for broadband and high gain circularly polarized stacked microstrip (CPSM) array applications. It consists of a combination of a microstrip line and a via. The gap between elements and location of the feed are optimized to achieve a good circular polarization (CP) performance with high gain. A 2 × 2 sequentially rotated array was fabricated and tested. The measured 3 dB axial‐ratio (AR) bandwidth is 27% (3.5–4.6 GHz) and at boresight gain is 9.0 dBic over the 3 dB AR bandwidth. The measured 10 dB return loss impedance bandwidth is around 51% (3.28–5.54 GHz). The proposed new feeding network system is very useful to design the high gain and wideband CP array in a space‐limited environment. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1784–1789, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23481
Embedded wire nodes in time‐domain unstructured 2D TLM
Authors: Wykes J. G. , Sewell P. , Christopoulos C. , Benson T. M. , Thomas D. W. P. , Vukovic A.
Published: April 2008

A novel triangular TLM node containing a subcell sized wire of arbitrary radius is presented. The technique is based upon the mapping between the total field at the cell boundary and exact modal field expansions around the wire. The wire node is incorporated into an unstructured 2D TLM algorithm providing a flexible package for modeling fine‐features in proximity to complex structures. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1753–1757, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23482
A novel microstrip slow‐wave resonator band‐pass filter for millimeter wave applications
Authors: Zhang Yong
Published: April 2008

Microstrip line is characterized by many advantages such as easy fabrication, compact size, lightweight, planar structure, and easy integration with other components on a single circuit board. In this article, a novel microstrip millimeter wave band‐pass filter with slow‐wave resonator is presented. By introducing cross‐coupling capacitance between the input and output ports of the filter, a slow‐wave resonator is suggested to improve both selectivity and stopband rejection. The proposed microstrip filter also has the merits of compact size and high stopband rejection. The experimental results on a fabricated filter agree with the simulated results very well. It might be widely used in plane circuits and advanced circuits such as MMIC and LTCC. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1720–1722, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23484
A 0.855 1.342 GHz octa‐phase LC VCO for multimode direct conversion receiver in 0.18‐μm CMOS
Authors: Lee Sangho , Kim Hyeongdong
Published: April 2008

New fully integrated, multiband octa‐phase LC VCOs are presented. The VCO is composed of four identical differential VCOs and implemented in a 0.18‐μm TSMC CMOS process. Four individual VCOs are connected by a series‐coupling transistor to obtain the octa‐phase signal and low phase noise characteristic. For multiband operation, a band‐tuning circuit is designed. The circuit is composed of a switching capacitor circuit and MOS varactors, and allows the VCO to operate at a frequency range of three standards (CDMA 2000 1x, WCDMA, WiBro) and to be tuned to select a channel in each frequency range. The measured phase noises of the VCO are −105 dBc at 100 kHz, −115 dBc at 1 MHz, and −130 dBc at 10 MHz for CDMA 2000 1x, WCDMA and WiBro, respectively, while the VCO draws 12 mA and consumes 21.6 mW with output buffers at the frequency band from a 1.8 V supply. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1717–1719, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23485
A method of double cross‐coupling lines for HTS filter design
Authors: Liao Sili , Zhang Xiaoping , Guo Xubo , Wei Bin , Cao Bisong
Published: April 2008

This article proposes a method of double cross‐coupling lines to produce the transmission zeros independently in the both close‐to‐band rejections of HTS filter, and that their positions are controllable. An eight‐pole HTS filter is simulated to present the feasibility of this method. According to this method, a four‐pole HTS filter has been designed and fabricated. The experimental results have good agreement with simulation and support this method. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1874–1876, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23486
Time‐domain finite‐element modeling of electrically and magnetically dispersive medium via recursive FFT
Authors: Li Xiaolei , Jin Jian‐Ming
Published: April 2008

A numerical scheme is described for the modeling of a general electrically and magnetically dispersive medium in the time‐domain finite‐element analysis of electromagnetic problems. This approach employs the recursive fast Fourier transform to evaluate the time convolutions induced by dispersion. Its implementation needs only the values of the susceptibility functions instead of their pole expansions as required by previous approaches based on recursive convolution. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1837–1841, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23488
Investigation of cavitation bubble dynamics by fiber‐coupling optical beam deflection technique
Authors: Xu Rongqing , Zhao Rui , Cui Yiping , Lu Jian , Ni Xiaowu
Published: April 2008

The bubble dynamics are investigated experimentally by means of a fiber‐optic force sensor based on optical beam deflection (OBD). This sensor is applied to detect the laser‐induced plasma ablation force and liquid‐jet impact during the cavitation bubble collapse. Some remarkable features such as liquid‐jet formation threshold and a variation of liquid‐jet appearance time are pointed out in this work. The experiment results indicate that once laser intensity goes beyond the liquid‐jet formation threshold, a high‐speed wall‐directed liquid‐jet develops and the appearance time of the liquid‐jet increases with laser energy. Combining the OBD detection principles, the pressure and velocity of liquid‐jet are calculated. The results are discussed with respect to the dynamics of cavitation bubble important for corresponding research fields. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1767–1770, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23491
Cryogenic low noise amplifier for VHF band applied in superconducting filter
Authors: Tang Shiming , Zhang Xiaoping , Guo Xubo , Wei Bin , Cao Bisong , Gao Baoxin
Published: April 2008

A low noise amplifiers (LNA) using common source parallel feedback have been designed and developed with high performance at liquid nitrogen temperature. The measured results show that the frequency band from 150 to 300 MHz in which the noise figure (NF) is within 0.55 dB, the power gain is about 21.6 ± 0.1 dB, the input volt standing wave ratio (VSWRin) < 1.1, output volt standing wave ratio (VSWRout) < 1.3 at 70 K. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1937–1940, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23497
Equilateral triangular microstrip array antenna for broadband operation
Authors: Pushpanjali G. M. , Konda R. B. , Mulgi S. N. , Satnoor S. K. , Hunagund P. V.
Published: April 2008

This article presents a novel design of corporate fed four‐element equilateral triangular microstrip array antenna (FETMSA) for multiband operation, which is attractive for emerging wireless communication systems. If FETMSA is fed through aperture, the coupling converts its multiband operation into triband operation. Further by using optimum slots in the radiating elements converts its tribands into dual wide bands, which may find application in synthetic aperture radar. The overall magnitude of impedance bandwidth is found to be 23.74% at X‐band frequencies with broadside radiation characteristics. This impedance bandwidth is 2.61 times more when compared with the impedance bandwidth of FETMSA. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1834–1837, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23503
Design of compact size tapered slot antenna
Authors: Xu Zh. , Liu Q. Zh. , Zhang Ch. F. , Li J. Y. , Yuan Y.
Published: April 2008

A compact size linearly tapered slot antenna is investigated. The new designed antenna is with wideband and wide beamwidth. Measured results show that the half‐power beamwidth (HPBW) of the compact size antenna achieves 120° at the operation frequency. Over the whole frequency band, the HPBW is wider than 100°. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1761–1763, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23507
A fractal dipole tag antenna for RFID dual‐band application
Authors: Lee Yi‐Chieh , Sun Jwo‐Shiun
Published: April 2008

New design of a dipole antenna with rectangular fractal shape radiator element with two operating bands for radio frequency identification (RFID) is presented. By using fractal shape slot and metal meander patch, the proposed antenna has the wide and dual measured return loss bandwidth. Besides, the omnidirectional radiation pattern of the design antenna cover the entire frequency range including ultra high frequency (UHF, 860–960 MHz) band and microwave (2.45 GHz) band has been obtained. Several properties of the proposed antenna for dual‐band operation such as impedance bandwidth, radiation pattern, and measured gain have been investigated numerically and experimentally in detail. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1963–1966, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23512
Trisection cross‐coupled filter with symmetrical response using split‐ring resonator DGS
Authors: Wu Bian , Qin Pei‐Yuan , Li Qi , Liang Chang‐Hong
Published: April 2008

In this article, a novel trisection cross‐coupled filter with symmetrical response by using split‐ring resonator defected ground structure (SRR DGS) is presented. The SRR DGS is loaded at the bottom of a two‐pole microstrip SRR filter, then a compact trisection cross‐coupled filter with a pair of transmission zeros is obtained. A practical filter which has a center frequency of 1.4 GHz and a relative bandwidth of 14% is successfully designed and fabricated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1774–1776, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23529
Estimation of local SAR level using RBFNN in three‐layer cylindrical human model
Authors: Colak Omer H. , Polat Ovunc
Published: April 2008

In this study, we present a new approach based on radial basis function neural networks (RBFNN) for estimation of specific absorption rate (SAR) in 2D cylindrical human model with three layers. The simulation results obtained using RBFNN were compared with the FDTD results. The estimated local SAR values using RBFNN has proved to be an impressive approximation to the FDTD results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1958–1961, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23535
A novel reconfigurable circular polarization patch antenna
Authors: Ouyang Jun , Yang Feng , Yang Shiwen
Published: April 2008

A novel design of a microstrip patch antenna with switchable branches is proposed to achieve circular polarization diversity. Two branches are incorporated into the patch and two switches are utilized to switch the branches on and off. By turning the switches on or off, this antenna can radiate with either right‐handed circular polarization or left‐handed circular polarization using the same feeding probe. Experimental results validate this concept. This design demonstrates useful features for wireless communication applications and future planetary missions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1921–1923, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23537
Design of a novel pulse generator for UWB applications
Authors: Song Fei , Wu Yi , Liao Huailin , Huang Ru
Published: April 2008

This article presents a low‐cost ultra‐wideband (UWB) pulse generator that is built using commercially available discrete components mounted on a PTFE substrate. A novel pulse shaping technique is adopted, which uses Schottky barrier diodes to generate a Gaussian‐cosine pulse with desirable time duration and spectrum response. Generated baseband pulses then are up‐converted to a center frequency of 4 or 8 GHz by a passive mixer, and Binary Phase‐Shift Keying (BPSK) modulation scheme is utilized. The final generated pulse with a bandwidth (−10 dB) of more than 1 GHz satisfies the FCC spectrum mask very well without any extra filtering, and can operate in either 3.1–5 GHz low band or 6–10 GHz high band. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1857–1861, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23541
An elastoplastic evaluation of the stress state around cylindrical openings based on a closed multiaxial yield surface
Authors: Li Li , Aubertin Michel
Published: April 2008

There are many applications encountered in geo‐engineering where there is a need to evaluate the stress state around circular openings. This paper presents a new analytical solution for evaluating the stresses around a cylindrical excavation in an elastoplastic medium defined by the closed MSDPu yield surface. The proposed formulation takes into account the 3D stress geometry with a plasticity criterion that intersects the mean stress axis on the positive (compressive) and negative (tensile) sides. The results shown here illustrate how the stress distribution and yielding zone size are affected by various influence factors. Validation of the proposed formulation is made by comparing calculated results with existing analytical solutions and a numerical simulation. Copyright © 2008 John Wiley & Sons, Ltd.