bluuebunny/crossref_metadata_2025 huggingface dataset:
Cost‐effective designs of fault‐tolerant access networks in communication systems
Authors: Chen Xujin , Chen Bo
Published: February 2009

This article is concerned with the design of fault‐tolerant access networks for cost‐effective communications—deploying network links and service providers (SPs) at a minimum cost, while ensuring error tolerance ability via the ring architecture. Given a set of service subscribers (SSs) in an access network, we are required to determine the locations and capacities of service providers, and to establish network links in terms of rings connecting SSs to SPs. We pay link costs for ring constructions and pay management costs for selecting SPs with capacities sufficient to manage the SSs in their rings. The network design aims to minimize the sum of the link costs and the management costs. Two APX‐hard problems in the general network design are studied in this article to address the scalable and modular features of SP capacities. Despite the logarithmic inapproximability that we show for one problem, constant‐factor approximation algorithms are proposed to solve the other problem and its variant in quartic time. © 2009 Wiley Periodicals, Inc. NETWORKS, 2009
A branch‐and‐cut algorithm for the undirected prize collecting traveling salesman problem
Authors: Bérubé Jean‐François , Gendreau Michel , Potvin Jean‐Yves
Published: February 2009

Given an undirected graph with edge costs and vertex prizes, the aim of the Prize Collecting Traveling Salesman Problem (PCTSP) is to find a simple cycle minimizing the total edge cost while collecting at least a minimum amount of prizes. In this article, we present a branch‐and‐cut algorithm to solve the PCTSP. We have adapted and implemented some classical polyhedral results for the PCTSP and derived inequalities from cuts designed for the Orienteering Problem. Computational results on instances with more than 500 vertices are reported. © 2009 Wiley Periodicals, Inc. NETWORKS, 2009
Synthesis and characterization of liquid crystalline diethanolamine‐based dendrimers
Authors: Didehban Khadijeh , Namazi Hassan , Entezami Ali Akbar
Published: February 2009

Three generations of diethanolamine‐based dendrimers containing nitroazobenzene were synthesized. Firstly, G1 was prepared by the diazotation of p‐nitroaniline, and then the obtained salts reacted with n‐phenyl‐2,2′‐iminodiethanol. The reaction of hydroxyl groups of diethanolamine of G1 and G2 with acryloyl chloride resulted in G1.5 and G2.5. Then, G2 and G3 were synthesized using Michael addition of amino group of diethanolamine and G1.5 and G2.5. The Williamson etherification and azo‐reaction were employed in the preparation of the mesogenic unit 4‐[4‐(6‐bromohexyloxy)phenylazo]nitrobenzene (N6‐Br). Secondly, mesogen‐functionalized dendrimers were synthesized via the coupling of the hydroxyl group of G1, G2, G3, and bromine from mesogenic units (N6‐Br). The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) were used for the investigation of the liquid crystalline properties of the mesogen‐functionalized dendrimers. The structures of obtained compounds were investigated using common spectroscopy methods and CHN analysis. Copyright © 2009 John Wiley & Sons, Ltd.
Composite polymer electrolyte membranes comprising P(VDF‐co‐CTFE)‐g‐PSSA graft copolymer and zeolite for fuel cell applications
Authors: Patel Rajkumar , Park Jung Tae , Lee Won Seok , Kim Jong Hak , Min Byoung Ryul
Published: February 2009

Hybrid organic/inorganic composite polymer electrolyte membranes based on a poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) grafted membrane and varying concentrations of zeolite were investigated for application in proton exchange membrane fuel cells (PEMFC). A proton conducting comb copolymer consisting of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) backbone and poly(styrene sulfonic acid) (PSSA) side chains, i.e. P(VDF‐co‐CTFE)‐g‐PSSA (graft copolymer) with 47 wt% of PSSA was synthesized using atom transfer radical polymerization (ATRP) and solution blended with zeolite. Upon incorporation of zeolite, the symmetric stretching band of both SO group (1169 cm−1) and the OH group (3426 cm−1) shifted to lower wavenumbers. The shift in these FT‐IR spectra suggests that the zeolite particles strongly interact with the sulfonic acid groups of PSSA chains. When the weight percent of zeolite 5A is above 7%, the proton conductivity at room temperature was reduced to 0.011 S/cm. The water uptake of the composite membranes decreased from 234 to 125% with an increase of the zeolite 5A weight percent to 10 wt%. The decrease in water uptake is likely a result of the decrease in the number of available water absorption sites because of the hydrogen bonding interactions between the zeolite particles and the graft copolymer matrix. This behavior is successfully investigated by scanning electron microscopy (SEM). The results of thermal gravimetric analysis (TGA) also showed that all the membranes were stable up to 300°C. Copyright © 2009 John Wiley & Sons, Ltd.
Weathering properties of elastic rubber concrete comprising waste tire solution
Authors: Chung Kyung‐Ho , Hong Young‐Keun
Published: February 2009

As a way of solving the environmental problem of waste tires, we introduce rubber concrete made from a rubber solution. The rubber solution was prepared by dissolving vulcanized waste tire scrap in a solvent mixture of tetrachloroethane and methylene chloride. The elastic rubber concrete was then manufactured by mold processing, with compositions comprising of rubber solution and aggregates. Carbon dioxide super‐critical fluid was used to extract solvent from mixture of rubber solution and aggregates. The compressive strength and strain of the rubber concrete were 93.4 MPa and 6.7%, respectively. These results indicated that the rubber concrete made in this study corresponded to ultrahigh strength and high elastic properties compared with conventional cement concrete. Weathering properties on the elastic rubber concrete were examined. The time of freeze‐thaw, lasting up to 10 days, did not affect the properties of the elastic rubber concrete. According to chemical tests with sodium chloride and sulfuric acid, it was found that the elastic rubber concrete was not affected by these chemicals for up to 240 days. Changing the outdoor condition for up to 720 days did not change the mechanical properties. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Preparation and characterization of poly(butylene terephthalate)/silica nanocomposites
Authors: Yao Xiayin , Tian Xingyou , Zhang Xian , Zheng Kang , Zheng Jin , Wang Ruoxi , Kang Shenghong , Cui Ping
Published: February 2009

In this study, we presented a convenient, in situ polymerization route for the preparation of Poly (butylene terephthalate) (PBT)/silica nanocomposites, in which silica was not premodified. The nanocomposites were synthesized by in situ polymerization of terephthalic acid (TPA), 1,4‐butanediol (BD) and silica. The structure of these nanocomposites were investigated by Fourier transform infrared (FTIR) and thermogravimetric analyses (TGA). The results show that PBT chains were successfully grafted onto the surface of silica. Transmission electron microscope (TEM) micrographs revealed that silica were homogeneously dispersed in PBT matrix at a size level of 10–20 nm. The isothermal crystallization kinetics of pure PBT and PBT/silica nanocomposites were investigated by differential scanning calorimeter (DSC) and simulated by Avrami model. The existence of silica could lead to an acceleration of crystallization and enhance the thermal stability of PBT. According to dynamic mechanical analysis (DMA), the storage modulus of PBT/silica nanocomposites were markedly improved compared with pure PBT. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Nylon 66/clay nanocomposite structure development in a twin screw extruder
Authors: Lin Bin , Thümen Anne , Heim Hans‐Peter , Scheel Gerhard , Sundararaj Uttandaraman
Published: February 2009

Nylon 66/clay nanocomposites were prepared in a Berstorff ZE25A UTX Ultra‐glide corotating twin screw extruder at 270°C. Two types of extruder configurations with different mixing sections were used. One comprised two kneading block sections in the screws (KB only) and the other had a combination of a multi‐process‐element (MPE) section and a kneading block section. Samples at eight different locations along the extruder screw were obtained and analyzed using scanning electron microscope and transmission electron microscope to examine the morphology development of clay inside nylon down the length of the extruder. It is found that the clay aggregates are quickly broken into smaller tactoids (micron size) and then even much smaller clay bundles (nanometer size) and single clay platelets in the first mixing section. The structure changes in the second mixing section are much less significant. X‐ray diffraction (XRD) analysis of the nanocomposite products showed small, or disappearance of, characteristic XRD (001) peaks, which indicates partial exfoliation, or complete exfoliation, respectively, of clay inside nylon matrix. Differential scanning calorimetry nonisothermal study shows that the crystallization temperature of the nanocomposites has increased around 17°C when compared with neat nylon 66. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Comparative proteomic analysis of differentially expressed proteins in an in vitro cellular carcinogenesis model of oral squamous cell carcinoma
Authors: Zhong Lai‐ping , Zhang Lei , Yang Xiao , Pan Hong‐ya , Zhou Xiao‐jian , Wei Kui‐jie , Ye Dong‐xia , Jiang Qian , Chen Wan‐tao , Zhang Zhi‐yuan
Published: February 2009

In vitro cellular model is an important tool to be used to investigate the cellular events related to pathophysiological conditions in humans. We have developed an in vitro cellular carcinogenesis model of oral squamous cell carcinoma (OSCC). In this study, we performed comparative proteomic analysis using 2‐DE and LC‐tandem mass chromatography to separate and identify differentially expressed proteins. Forty‐five proteins were identified, including 24 proteins with decreased expression and 19 proteins with increased expression during carcinogenesis from immortalized oral epithelial cells to squamous cancerous cells. The identified known proteins were classified into three ontologies of cellular component, molecular function, and biological process. Further validation of five identified proteins (ANXA1, ANXA2, CTSB, KRT17, and S100A6) in the cellular carcinogenesis model and cancerous tissues from OSCC patients confirmed the comparative proteomic results. Moreover, Annexin A1 and A2 expression levels correlated with the pathological differentiation grade of cancerous tissues. Thus, this work provides a dynamic protein file of differentially expressed proteins in oral squamous carcinoma cells, which could provide clues to study the mechanisms of OSCC carcinogenesis and possibly be developed as potential biomarkers for clinical diagnosis or prognostic monitoring.
Structure of a mutant human purine nucleoside phosphorylase with the prodrug, 2‐fluoro‐2′‐deoxyadenosine and the cytotoxic drug, 2‐fluoroadenine
Authors: Afshar Sepideh , Sawaya Michael R. , Morrison Sherie L.
Published: February 2009

A double mutant of human purine nucleoside phosphorylase (hDM) with the amino acid mutations Glu201Gln:Asn243Asp cleaves adenosine‐based prodrugs to their corresponding cytotoxic drugs. When fused to an anti‐tumor targeting component, hDM is targeted to tumor cells, where it effectively catalyzes phosphorolysis of the prodrug, 2‐fluoro‐2′‐deoxyadenosine (F‐dAdo) to the cytotoxic drug, 2‐fluoroadenine (F‐Ade). This cytotoxicity should be restricted only to the tumor microenvironment, because the endogenously expressed wild type enzyme cannot use adenosine‐based prodrugs as substrates. To gain insight into the interaction of hDM with F‐dAdo, we have determined the crystal structures of hDM with F‐dAdo and F‐Ade. The structures reveal that despite the two mutations, the overall fold of hDM is nearly identical to the wild type enzyme. Importantly, the residues Gln201 and Asp243 introduced by the mutation form hydrogen bond contacts with F‐dAdo that result in its binding and catalysis. Comparison of substrate and product complexes suggest that the side chains of Gln201 and Asp243 as well as the purine base rotate during catalysis possibly facilitating cleavage of the glycosidic bond. The two structures suggest why hDM, unlike the wild‐type enzyme, can utilize F‐dAdo as substrate. More importantly, they provide a critical foundation for further optimization of cleavage of adenosine‐based prodrugs, such as F‐dAdo by mutants of human purine nucleoside phosphorylase.
What is new in nitride laser diodes reliability studies
Authors: Marona L. , Wiśniewski P. , Leszczyński M. , Prystawko P. , Grzegory I. , Suski T. , Porowski S. , Czernecki R. , Czerwinski A. , Pluska M. , Ratajczak J. , Perlin P.
Published: February 2009

In the present paper we discuss possible degradation mechanisms of InGaN violet laser diodes, grown on bulk GaN substrates. Lifetime tests include electrical and optical parameters monitoring, temperature and microstructural studies. Our results point out at very strong, the exponential dependence of the degradation rate on the operation current of the device. The square root‐like behavior of the degradation as a function of time is also reconfirmed. Our microstructural analysis indicates also that the appearance of strain driven defects (dislocation loops formed around AlGaN/GaN interface) may have an influence on the laser diode degradation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gap bowing in Inx Ga1–xN and Inx Al1–xN under pressure
Authors: Gorczyca I. , Suski T. , Christensen N. E. , Svane A.
Published: February 2009

The electronic band structures of InxGa1–xN and InxAl1–xN alloys are calculated by ab‐initio methods in a supercell geometry, and the effects of varying the composition and applying external pressure examined. Indium segregation is also simulated, and it is shown that it strongly influences the band gap and its pressure derivative. Both the band gaps and their pressure coefficients are considerably lower when In atoms are clustered, than when they are uniformly distributed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlInN optical confinement layers for edge emitting group III‐nitride laser structures
Authors: Schenk H. P. D. , Nemoz M. , Korytov M. , Vennéguès P. , Demolon P. , Dräger A. D. , Hangleiter A. , Charash R. , Maaskant P. P. , Corbett B. , Duboz J. Y.
Published: February 2009

Al1–xInxN ternary alloys with solid phase indium compositions between x = 0.15 and 0.28 have been grown by metalorganic chemical vapor deposition under indium rich conditions. Within the growth temperature range of 750‐810 °C the indium incorporation into the solid is increasingly reduced by a competing process with thermal activation energy of 1.07 eV. Using this growth scheme, smooth epitaxial layers with root mean‐squares surfaces roughness of 0.3‐0.8 nm are obtained. Extrinsic origin is suggested for the low temperature photoluminescence peak associated with these layers. (Al,In)N films lattice‐matched to GaN have been introduced into laser diode structures for optical confinement. Optical gain is observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Realization of 270 nm band AlGaN based UV‐LEDs on large area AlN templates with high crystalline quality
Authors: Takano Takayoshi , Hirayama Hideki , Fujikawa Sachie , Tsubaki Kenji
Published: February 2009

Semiconductor light‐emitting diodes (LEDs) with emission wavelengths in the range 250‐350nm have a wide range of potential applications. So far, high power AlGaN‐ and InAlGaN‐based LEDs in the ultraviolet (UV) region have been fabricated. However, for the realization of commercially‐available low‐cost UV‐LEDs, the fabrication of structures on large‐sized or multiple wafers is desirable. We have now demonstrated the growth of AlN templates using an ammonia (NH3) pulsed‐flow multilayer (ML) growth technique and AlGaN based UV‐LEDs on (0001) sapphire substrates by low‐pressure metalorganic chemical vapour deposition (MOCVD) in a 2″ × 3 reactor system. In the case of the (10‐12) X‐ray rocking curve (XRC), the full‐width‐at‐half‐maximum (FWHM) increased from 510 arcsec to 580 arcsec when scanning from the center to the edge of the wafer. On the other hand, the FWHM of the (0002) XRC was slightly increased from 170 arcsec to 190 arcsec. Furthermore, Emission peaks for UV‐LEDs were clearly observed in the range from 268 nm to 284 nm. The output power at 100 mA and maximum output power were 0.2 mW and 0.3 mW, respectively. These results indicate that sub‐milliwatt operation in the deep‐UV range was successfully achieved. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of total pressure and precursors flow rates on the growth of aluminium nitride by high temperature chemical vapor deposition (HTCVD)
Authors: Claudel Arnaud , Blanquet Elisabeth , Chaussende Didier , Pique Didier , Pons Michel
Published: February 2009

In order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750 °C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influence of total pressure, Cl2 flow rate and NH3 flow rate on AlN growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 μm.h–1 have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As‐grown AlN layers were characterized by SEM and X‐ray Diffraction. Surface morphology was studied by SEM and FEG‐SEM and crystallographic orientations were obtained by X‐ray diffraction on θ/2θ. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly luminescent InxGa1–xN thin films grown over the entire composition range by energetic neutral atom beam lithography & epitaxy (ENABLE)
Authors: Williamson T. L. , Hoffbauer M. A. , Yu K. M. , Reichertz L. A. , Hawkridge M. E. , Jones R. E. , Miller N. , Ager J. W. , Liliental‐Weber Z. , Walukiewicz W.
Published: February 2009

In‐rich alloys of InxGa1–xN are becoming highly sought after because of the significant role they may play in a number of technologies including photovoltaics, solid‐state lighting, and high frequency electronics. Unfortunately, these alloys are difficult to produce with high quality by conventional growth technologies. We describe our efforts to create high‐quality In‐rich InxGa1–xN alloys by a new growth technology called energetic neutral atom beam lithography & epitaxy (ENABLE). ENABLE uses a collimated beam of neutral N atoms (kinetic energies of ∼2.0 eV) as the reactive group V species in InxGa1–xN growth, allowing for a substantial reduction in substrate growth temperatures (typically 450 °C to 750 °C). Directly providing a significant portion of the required reaction energy by the N atoms rather than by high substrate temperatures improves InxGa1–xN film quality across the full stoichiometric range. ENABLE‐grown InN on sapphire is shown to be highly crystalline by XRD and RBS. The observed photoluminescence (PL) peak energy is 0.74 eV, and the electron concentrations are between 7x1018 and 7x1019 cm–3 with the highest mobility exceeding 1200 cm2/Vs. ENABLE has been used to produce highly luminescent InxGa1–xN with PL peak energies in the 1.5 to 2.5 eV range, spanning the visible range. ENABLE grown InxGa1–xN films are shown by XRD to be highly crystalline consisting of a uniform single phase. These results establish ENABLE as a new technique uniquely capable of low temperature growth of high‐quality InxGa1–xN films over widely varying compositions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of time‐resolved photoluminescence from InGaN single quantum wells grown on nonpolar and semipolar bulk GaN substrates
Authors: Garrett Gregory A. , Shen Hongen , Wraback Michael , Tyagi Anurag , Schmidt Mathew C. , Speck James S. , DenBaars Steven P. , Nakamaura Shuji
Published: February 2009

Single quantum wells of low InN concentration InGaN grown on high quality nonpolar and semipolar substrates cut from bulk GaN boules are studied by time‐resolved photoluminescence techniques. Data is presented for different well widths at varying pump fluence and sample temperature to study nonlinear non‐radiative recombination, radiative lifetimes, and carrier localization or separation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnO quantum dots embedded in a SiO2 nanoparticle layer grown by atomic layer deposition
Authors: Wu M. K. , Shih Y. T. , Chen M. J. , Yang J. R. , Shiojiri M.
Published: February 2009

We have fabricated ZnO quantum dots embedded in an amorphous silicon oxide layer by atomic layer deposition (ALD). SiO2 nanoparticles with diameters of approximately 10 nm dispersed in isopropyl alcohol solution were spin‐on coated on the Si substrate and dried in an oven. Subsequently, ALD of ZnO was performed using two precursors, Zn(C2H5)2 and H2O, which can infiltrate into the small voids between SiO2 nanoparticles. It is revealed that the deposited ZnO was uniformly embedded in the SiO2 layer as crystalline ZnO quantum dots with diameters in the range of about 3–8 nm after a high‐temperature post‐deposition annealing treatment. The quantum confinement effect of the ZnO dots is well manifested by a significant blue‐shift of about 80 meV in the photoluminescence spectrum at room temperature. This technique is applicable to a new fabrication route of optoelectronic devices, such as UV light emitting diodes and lasers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
QSAR Models for Prediction of PPARδ Agonistic Activity of Indanylacetic Acid Derivatives
Authors: Lather Viney , Fernandes Miguel X.
Published: February 2009

Peroxisome Proliferator Activated Receptor β/δ (PPAR β/δ), one of three PPAR isoforms is a member of nuclear receptor superfamily and ubiquitously expressed in several metabolically active tissues such as liver, muscle, and fat. Tissue specific expression and knock‐out studies suggest a role of PPARδ in obesity and metabolic syndrome. Specific and selective PPARδ ligands may play an important role in the treatment of metabolic disorders. Indanylacetic acid derivatives reported as potent and specific ligands against PPARδ have been studied for the Quantitative Structure–Activity Relationships (QSAR). Molecules were represented by chemical descriptors that encode constitutional, topological, geometrical, and electronic structure features. Four different approaches, i.e., random selection, hierarchical clustering, k‐means clustering, and sphere exclusion method were used to classify the dataset into training and test subsets. Forward stepwise Multiple Linear Regression (MLR) approach was used to linearly select the subset of descriptors and establish the linear relationship with PPARδ agonistic activity of the molecules. The models were validated internally by Leave One Out (LOO) and externally for the prediction of test sets. The best subset of descriptors was then fed to the Artificial Neural Networks (ANN) to develop non‐linear models. Statistically significant MLR models; with R2 varying from 0.80 to 0.87 were generated based on the different training and test set selection methods. Training of ANNs with different architectures for the different training and test selection methods resulted in models with R2 values varying from 0.83 to 0.94, which indicates the high predictive ability of the models.
Exploring 2D and 3D QSARs of 2,4‐Diphenyl‐1,3‐oxazolines for Ovicidal Activity Against Tetranychus urticae
Authors: Roy Kunal , Paul Somnath
Published: February 2009

Quantitative Structure–Activity Relationship (QSAR) studies have been carried out for ovicidal activity of 2,4‐diphenyl‐1,3‐oxazoline analogues against two‐spotted spider mite Tetranychus urticae, which causes serious damage to agricultural products. The studies have been performed with 2D (physicochemical, structural, and topological) and 3D (shape, spatial, electronic, and molecular field) descriptors. The chemometrics tools used for the analyses are Genetic Function Approximation (GFA) and Genetic Partial Least Squares (G/PLS). The whole dataset (n=90) was divided into a training set (75% of the dataset) and a test set (remaining 25%) on the basis of K‐means clustering technique of standardized topological and structural descriptor matrix. Models developed from the training set were used to predict the activity of the test set compounds. All the models have been validated internally, externally, and by Y‐randomization technique. However, different models emerged as the best ones according to different validation criteria. We have tried a consensus model, which is based on the results obtained by all predictive models and this may provide the most stable solution. Models obtained by using 2D parameters revealed that the chain length of the substituent at para position of the 4‐phenyl ring is a critical factor. Lipophilicity of the molecule also reflects a dominant role for the ovicidal activity. Models generated from 3D descriptors suggest that the shape of the substituents should be optimum and the lipophilic substituents having electronegative atoms with distributed positive charge over a surface may enhance the ovicidal activity. The model obtained from Molecular Field Analysis (MFA) suggests that bulky substituents with optimally distributed charge may increase the ovicidal activity.
A special reactor coupled with a high‐temperature mass spectrometer for the investigation of the vaporization and cracking of organometallic compounds
Authors: Violet Perrine , Nuta Ioana , Artaud Laurent , Collas Hervé , Blanquet Elisabeth , Chatillon Christian
Published: February 2009

A special reactor coupled to a high‐temperature mass spectrometer was specifically designed for the study of vaporization and thermal cracking of organometallic precursors. This reactor has two kinds of settings. One is a single Knudsen effusion cell which enables the analysis of the composition of saturated vapors and the determination of the partial pressure of each gaseous molecule in equilibrium with its condensed phase. This cell is an evaporation/sublimation cell (operating from 243 to 473 K), which can be tightly closed – like a vacuum chamber – in order to protect organometallic compounds against moisture and atmospheric components. This cell can be independently weighed usefully to evaluate the equilibrium vapor pressures of the sample using the mass‐loss method. During experiments, the effusion aperture is externally opened for direct mass spectrometric measurements. The other setting dedicated to the study of thermal decomposition of gaseous molecules consists of a set of tandem cells: the previously described Knudsen cell and a cracking cell (operating from 293 to 973 K). Copyright © 2009 John Wiley & Sons, Ltd.
Corn plant sensing using real‐time stereo vision
Authors: Jin Jian , Tang Lie
Published: February 2009

Though some two‐dimensional (2D) machine vision–based systems for early‐growth‐stage corn plant sensing exist, some of their shortcomings are difficult to overcome. The greatest challenge comes from separating individual corn plants with overlapped plant canopies. With 2D machine vision, variation in outdoor lighting conditions and weeds in the background also pose difficulties in corn plant identification. Adding the depth dimension has the potential to improve the performance of such a sensing system. A new corn plant sensing system using a real‐time stereo vision system was investigated in this research. Top‐view depth images of corn plant canopy were acquired. By processing the depth images, the algorithm effectively updated the plant skeleton structures and finally recognized individual corn plants and detected their center positions. The stereo vision system was tested over corn plants of V2–V3 growth stages in both laboratory and field conditions. Experimental results showed that the stereo vision system was capable of detecting both separated and overlapped corn plants. During the field test, 96.7% of the corn plants were correctly detected, and plant center positions were estimated with maximum distance errors of 5 and 1 cm for 74.6% and 62.3% of detections, respectively. © 2009 Wiley Periodicals, Inc.
Connectivity is a two‐way street—the need for a holistic approach to fish passage problems in regulated rivers
Authors: Calles O. , Greenberg L.
Published: February 2009

We evaluated the effects of a rehabilitation project, whose goal was to re‐establish longitudinal connectivity for anadromous trout in the regulated river Emån. We used a holistic approach, by tagging and following both upstream‐migrating spawners (N = 348) and downstream‐migrating smolts (N = 80) and kelts as they passed two hydroelectric plants (HEP 2‐3) with nature‐like fishways.

When migrating upstream, 84–88% of the spawners stopped, primarily at spawning grounds, before reaching HEP2. The proportion of stoppers was lower (56%) for fish that had been to the fishways in previous years, indicating that the recolonization rate is likely to increase over time. Of the spawners that approached the fishway at HEP2, 77% rapidly located the fishway situated next to the tail‐race, resulting in an attraction efficiency of 81% and a passage efficiency of 95%. The time required to locate the fishway inside the former channel at HEP3 was substantial, but the attraction efficiency (89%) and passage efficiency (97%) were nevertheless high.

The kelts swam downstream mainly in spring, using spill gates and the fishways, to swim past HEP2 and 3 and continue downstream to the Baltic Sea. Iteroparity was confirmed by the fact that 20% of the spawners were tagged in previous years. Smolt loss was about 30% for both HEPs, with a higher turbine‐induced loss 30% for fish passing through Francis runners than a Kaplan runner. Fifteen per cent of the tagged smolt reached the sea and none of these fish had swum through the Francis runners.

It will probably take many years before longitudinal connectivity is fully re‐established in the river Emån, due to substantial losses of both upstream‐migrating spawners (35% loss) and downstream‐migrating smolts (50%) and kelts. In addition, smolt production in areas upstream of HEP3 is far below carrying capacity. Thus, additional measures that not only facilitate movement of upstream spawners, but also reduce mortality and injuries of downstream migrants are urgently needed to create a self‐sustaining fish population. Copyright © 2009 John Wiley & Sons, Ltd.
Layer‐By‐Layer Films as a Biomimetic Reservoir for rhBMP‐2 Delivery: Controlled Differentiation of Myoblasts to Osteoblasts
Authors: Crouzier Thomas , Ren Kefeng , Nicolas Claire , Roy Christian , Picart Catherine
Published: February 2009

Efficient delivery of growth or survival factors to cells is one of the most important long‐term challenges of current cell‐based tissue engineering strategies. The extracellular matrix acts as a reservoir for a number of growth factors through interactions with its components. In the matrix, growth factors are protected against circulating proteases and locally concentrated. Thus, the localized and long‐lasting delivery of a matrix‐bound recombinant human bone morphogenetic protein 2 (rhBMP‐2) from a biomaterial surface would mimic in vivo conditions and increase BMP‐2 efficiency by limiting its degradation. Herein, it is shown that crosslinked poly(L‐lysine)/hyaluronan (HA) layer‐by‐layer films can serve as a reservoir for rhBMP‐2 delivery to myoblasts and induce their differentiation into osteoblasts in a dose‐dependent manner. The amount of rhBMP‐2 loaded in the films is controlled by varying the deposition conditions and the film thickness. Its local concentration in the film is increased up to ≈500‐fold when compared to its initial solution concentration. Its adsorption on the films, as well as its diffusion within the films, is evidenced by microfluorimetry and confocal microscopy observations. A direct interaction of rhBMP‐2 with HA is demonstrated by size‐exclusion chromatography, which could be at the origin of the rhBMP‐2 “trapping” in the film and of its low release from the films. The bioactivity of rhBMP‐2‐loaded films is due neither to film degradation nor to rhBMP‐2 release. The rhBMP‐2‐containing films are extremely resistant and could sustain three successive culture sequences while remaining bioactive, thus confirming the important and protective effect of rhBMP‐2 immobilization. These films may find applications in the local delivery of immobilized growth factors for tissue‐engineered constructs and for metallic biomaterial surfaces, as they can be deposited on a wide range of substrates with different shapes, sizes, and composition.
A hybrid positioning system for technology‐independent location‐aware computing
Authors: Ficco Massimo , Russo Stefano
Published: February 2009

Location‐aware computing is a form of context‐aware mobile computing that refers to the ability of providing users with services that depend on their position. Locating the user terminal, often called positioning, is essential in this form of computing. Towards this aim, several technologies exist, ranging from personal area networking, to indoor, outdoor, and up to geographic area systems. Developers of location‐aware software applications have to face with a number of design choices, that typically depend on the chosen technology. This work addresses the problem of easing the development of pull location‐aware applications, by allowing uniform access to multiple heterogeneous positioning systems. Towards this aim, the paper proposes an approach to structure location‐aware mobile computing systems in a way independent of positioning technologies. The approach consists in structuring the system into a layered architecture, that provides application developers with a standard Java Application Programming Interface (JSR‐179 API), and encapsulates location data management and technology‐specific positioning subsystems into lower layers with clear interfaces. In order to demonstrate the proposed approach we present the development of HyLocSys. It is an open hybrid software architecture designed to support indoor/outdoor applications, which allows the uniform (combined or separate) use of several positioning technologies. HyLocSys uses a hybrid data model, which allows the integration of different location information representations (using symbolic and geometric coordinates). Moreover, it allows support to handset‐ and infrastructure‐based positioning approaches while respecting the privacy of the user. The paper presents a prototypal implementation of HyLocSys for heterogeneous scenarios. It has been implemented and tested on several platforms and mobile devices. Copyright © 2009 John Wiley & Sons, Ltd.
Pharmacological characterization of 2‐methoxy‐N‐propylnorapomorphine's interactions with D2and D3dopamine receptors
Authors: Skinbjerg Mette , Namkung Yoon , Halldin Christer , Innis Robert B. , Sibley David R.
Published: February 2009

Dopaminergic signaling pathways have been extensively investigated using PET imaging, primarily with antagonist radioligands of D2and D3dopamine receptors (DARs). Recently, agonist radioligands of D2/D3DARs have begun to be developed and employed. One such agonist is (R)‐2‐11CH3O‐N‐n‐propylnorapomorphine (MNPA). Here, we perform a pharmacological characterization of MNPA using recombinant D2and D3DARs expressed in HEK293 cells. MNPA was found to robustly inhibit forskolin‐stimulated cAMP accumulation to the same extent as dopamine in D2or D3DAR‐transfected cells, indicating that it is a full agonist at both receptors. MNPA is ∼50‐fold more potent than dopamine at the D2DAR, but equally potent as dopamine at the D3DAR. MNPA competition binding curves in membrane preparations expressing D2DARs revealed two binding states of high and low‐affinity. In the presence of GTP, only one binding state of low affinity was observed. Direct saturation binding assays using [3H]MNPA revealed similar results as with the competition experiments leading to the conclusion that MNPA binds to the D2DAR in an agonist‐specific fashion. In contrast to membrane preparations, using intact cell binding assays, only one site of low affinity was observed for MNPA and other agonists binding to the D2DAR. MNPA was also found to induce D2DAR internalization to an even greater extent than dopamine as determined using both cell surface receptor binding assays and confocal fluorescence microscopy. Taken together, our data indicate that the PET tracer, MNPA, is a full and potent agonist at both D2and D3receptors. Synapse 63:462–475, 2009. © 2009 Wiley‐Liss, Inc.
Positron emission tomography imaging of amphetamine‐induced dopamine release in the human cortex: A comparative evaluation of the high affinity dopamine D2/3 radiotracers [11C]FLB 457 and [11C]fallypride
Authors: Narendran Rajesh , Frankle W. Gordon , Mason N. Scott , Rabiner Eugenii A. , Gunn Roger N. , Searle Graham E. , Vora Shivangi , Litschge Maralee , Kendro Steve , Cooper Thomas B. , Mathis Chester A. , Laruelle Marc
Published: February 2009

The use of PET and SPECT endogenous competition binding techniques has contributed to the understanding of the role of dopamine in several neuropsychiatric disorders. An important limitation of these imaging studies is the fact that measurements of acute changes in synaptic dopamine have been restricted to the striatum. The ligands previously used, such as [11C]raclopride and [123I]IBZM, do not provide sufficient signal to noise ratio to quantify D2 receptors in extrastriatal areas, such as cortex, where the concentration of D2 receptors is much lower than in the striatum. Given the importance of cortical DA function in cognition, a method to measure cortical dopamine function in humans would be highly desirable. The goal of this study was to compare the ability of two high affinity DA D2 radioligands [11C]FLB 457 and [11C]fallypride to measure amphetamine‐induced changes in DA transmission in the human cortex. D2 receptor availability was measured in the cortical regions of interest with PET in 12 healthy volunteers under control and postamphetamine conditions (0.5 mg kg−1, oral), using both [11C]FLB 457 and [11C]fallypride (four scans per subjects). Kinetic modeling with an arterial input function was used to derive the binding potential (BPND) in eight cortical regions. Under controlled conditions, [11C]FLB 457 BPND was 30–70% higher compared with [11C]fallypride BPND in cortical regions. Amphetamine induced DA release led to a significant decrease in [11C]FLB 457 BPND in five out the eight cortical regions evaluated. In contrast, no significant decrease in [11C]fallypride BPND was detected in cortex following amphetamine. The difference between [11C]FLB 457 and [11C]fallypride ability to detect changes in the cortical D2 receptor availability following amphetamine is related to the higher signal to noise ratio provided by [11C]FLB 457. These findings suggest that [11C]FLB 457 is superior to [11C]fallypride for measurement of changes in cortical synaptic dopamine. Synapse 63:447–461, 2009. © 2009 Wiley‐Liss, Inc.
Collagen accumulation over time in the murine lung after exposure to crocidolite asbestos or Libby amphibole
Authors: Smartt Aubrey M. , Brezinski Mary , Trapkus Melanie , Gardner Donald , Putnam Elizabeth A.
Published: February 2009

Libby, MT is the site of a closed vermiculite mine that produced ore contaminated with asbestos‐like amphiboles. Worldwide distribution of the material and the long latency period for manifestation of asbestos‐related diseases (ARDs) has created a significant health threat for many years to come. The composition of the Libby material [termed the Libby amphibole (LA)] differs from other well‐studied types of asbestos in that it is a mixture of several amphibole fibers. The purpose of this study was to determine the fibrotic effects of LA exposure in a mouse model and to compare these effects to those of a well‐characterized amphibole fiber, crocidolite asbestos. We exposed C57Bl/6 mice to LA or crocidolite and analyzed lung RNA, protein, and morphology at 1 week, 1 month, and 3 months post instillation. Our results indicate that both forms of amphibole studied induced increased collagen types I and III mRNA expression and collagen protein deposition in exposed murine lungs compared to the PBS‐instilled control lungs, and that these collagen increases were the most significant at 1 month after exposure. However, crocidolite‐exposed mice demonstrated greater increases in collagen deposition than those exposed to LA, indicating that the fibrotic effects of LA exposure, although not as severe as those of crocidolite in this model system, were still able to induce collagen deposition. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.
Hierarchical Titanate Nanostructures through Hydrothermal Treatment of Commercial Titania Powders
Authors: Dong Zhenghong , Zhao Yongnan , Su Hao , Yu Jianguo , Li Lu
Published: February 2009

Hierarchical titanate nanostructures were hydrothermally synthesized in concentrated base solutions using commercial titania powders as starting materials. By varying the base concentration, nanowire arrays, flowers of nanosheets and nanotubes, and urchin‐like nanostructures of nanowires and nanotubes were sequentially fabricated. If the NaOH concentration was higher than 6 M, hydrated Na2Ti6O13 nanowire arrays, with nanowire diameters of 20–90 nm and an aspect ratio of 1100–5000, were produced at suitable reaction temperatures over a large area. In 10 M KOH solutions, aligned nanowires with a diameter of 30 nm and a lenght of 80 μm formed. In 4 M NaOH solutions, micrometer‐sized flowers of nanotubes and nanosheets formed. Reactions in 2 M NaOH solutions produced urchin‐like materials with a size of ca. 10 μm that were composed of nanotubes and nanowires. The adsorption behavior of the urchin‐like materials resembled macroporous materials with micropores. Since both base concentration and reaction temperature affected the reaction rate, the formation of various titanate nanostructures was proposed as a growth speed controlled process.
Synthesis of Aluminum‐Rich Analcime Using an Ethylene Diamine Derivative as Template
Authors: Naser Azizi Seyed , Yousefpour Maryam
Published: February 2009

The hydrothermal synthesis of analcime (ANA) with N,N′‐dibenzyl‐N,N,N′,N′‐tetramethylethylenediamine (DBTMED) as template was systematically studied. The various parameters that affect the crystallization of analcime, such as temperature, time, Al source, and Si/Al ratio were investigated. Systematic variations of these parameters revealed that ANA was obtained from the reaction mixture with the optimized ratios of SiO2/Al2O3 = 5–9.5 in presence of DBTMED, whereas template‐free clear solution methods require SiO2/Al2O3 ratio of greater than 25. When experiments were conducted at 130 and 150 °C for 4 days, a mixture of analcime and zeolite P was present in the samples, and a pure analcime sample could be obtained with heating in the temperature range 160–180 °C. When microwave and conventional heating were used, analcime could be obtained after 2 days. The obtained products were characterized by XRD, SEM, and IR spectroscopy.
Trilithium Trisaminotriazinates
Authors: Glatz Germund , Motz Günter , Kempe Rhett
Published: February 2009

Two trilithium‐tris(trimethylsilylamino)triazinates were prepared from the reaction of three equivalents nBuLi and one equivalent 2,4,6‐tris(trimethylsilyamino)‐1,3,5‐triazine (TrTMS3H3) in tetrahydrofurane (THF) or dimethoxyethane (DME). Concentration of the mother liquor gave single crystals suitablefor X‐ray diffraction. The solid‐state structures of [(TrTMS3)2Li6(THF)8]·2THF (1) and [(TrTMS3)2Li6(DME)4] (2) were determined. Two triply deprotonated TrTMS3 ligands are bridged by four lithium atoms.
Connective tissue growth factor(CCN2), a pathogenic factor in diabetic nephropathy. What does it do? How does it do it?
Authors: Mason Roger M.
Published: February 2009

Connective tissue growth factor (CTGF/CCN2) is a member of the CCN family of matricellular proteins. Its expression is induced by a number of factors including TGF‐β. It has been associated with fibrosis in various tissues including the kidney. Diabetic nephropathy (DN) develops in about 30% of patients with diabetes and is characterized by thickening of renal basement membranes, fibrosis in the glomerulus (glomerulosclerosis), tubular atrophy and interstitial fibrosis, all of which compromise kidney function. This review examines changes in CTGF expression in the kidney in DN, the effects they have on glomerular mesangial and podocyte cells and the tubulointerstitium, and how these contribute to driving fibrotic changes in the disease. CTGF can bind to several other growth factors modifying their function. CTGF is also able to interact with receptors on cells, including integrins, tyrosine receptor kinase A (TrkA), low density lipoprotein receptor‐related protein (LRP) and heparan sulphate proteoglycans. These interactions, the intracellular signalling pathways they activate, and the cellular responses evoked are reviewed. CTGF also induces the expression of chemokines which themselves have pharmacological actions on cells. CTGF may prompt some responses by acting through several different mechanisms, possibly simultaneously. For example, CTGF is often described as an effector of TGF‐β. It can promote TGF‐β signalling by binding directly to the growth factor, promoting its interaction with the TGF‐β receptor; by triggering intracellular signalling on binding the TrkA receptor, which leads to the transcriptional repression of Smad7, an inhibitor of the TGF‐β signalling pathway; and by binding to BMP‐7 whose own signalling pathway opposing TGF‐β is inhibited, leading to enhanced TGF‐β signalling.
The piggyBac transposon is an integrating non‐viral gene transfer vector that enhances the efficiency of GDEPT
Authors: Kang Yu , Zhang Xiao‐Yan , Jiang Wei , Wu Chao‐Qun , Chen Chun‐Mei , Gu Jian‐Ren , Zheng Yu‐Fang , Xu Cong‐Jian
Published: February 2009

Gene‐directed enzyme prodrug therapy (GDEPT) is a strategy developed to selectively target cancer cells. However, the clinical benefit is limited due to its poor gene transfer efficiency. To overcome this obstacle, we took advantage of piggyBac (PB) transposon, a natural non‐viral gene vector that can induce stable chromosomal integration and persistent gene expression in vertebrate cells, including human cells. To determine whether the vector can also mediate stable gene expression in ovarian cancer cells, we constructed a PB transposon system that simultaneously expresses the Herpes simplex virus thymidine kinase (HSV‐tk) gene and the monomeric red fluorescent protein (mRFP1) reporter gene. The recombinant plasmid, pPB/TK, was transfected into ovarian adenocarcinoma cells SKOV3 with FuGENE HD reagent, and the efficiency was given by the percentage of mRFP1‐positive cells detected by flow cytometry and confocal microscopy. The specific expression of HSV‐tk in transfected cells was confirmed by RT‐PCR and western blotting. The sensitivity of transfected cells to pro‐drug ganciclovir (GCV) was determined by methylthiazoletetrazolium (MTT) assay. A total of 56.4 ± 8.4% cells transfected with pPB/TK were mRFP1 positive, compared to no measurable mRFP1 expression in pORF‐HSVtk‐transfected cells. The expression level of HSV‐tk in pPB/TK‐transfected cells was ∼10 times higher than in pORF‐HSVtk‐transfected cells. The results show that pPB/TK transfection increases the sensitivity of cells to GCV in a dose‐dependent manner. Our data indicate that the PB transposon system could enhance the anti‐tumor efficiency of GDEPT in ovarian cancer.