bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecularly imprinted polymers and their application in solid phase extraction
Authors: Lasáková Martina , Jandera Pavel 
Published: February 2009

AbstractSolid phase extraction is routinely used in many different areas of analytical chemistry. Some of the main fields are environmental, biological, and food chemistry, where cleaning and pre‐concentration of the sample are important steps in the analytical protocol. Molecularly imprinted polymers (MIPs) have attracted attention because they show promise as compound‐selective or group‐selective media. The application of these synthetic polymers as sorbents allows not only pre‐concentration and cleaning of the sample but also selective extraction of the target analyte, which is important, particularly when the sample is complex and impurities can interfere with quantification. This review surveys the selectivity of MIPs in solid phase extraction of various kinds of analytes.
Antiviral drug discovery: Ten more compounds, and ten more stories (part B)
Authors: De Clercq Erik 
Published: February 2009

AbstractThis review article that complements the previous review article on “The discovery of antiviral agents: ten different compounds, ten different stories” presents ten more compounds and ten more stories in which I have been closely involved at one or another point of my scientific career: (i) interferon (IFN) (in particular, IFN‐β); (ii) poly(I).poly(C); (iii) suramin; (iv) novel acyclic nucleoside phosphonates; (v) the double prodrug of [9‐(2‐phosphonomethoxyethyl)guanine]; (vi) cyclic nucleoside phosphonates; (vii) picornavirus inhibitors; (viii) human immunodeficiency virus (HIV) co‐receptor inhibitors; (ix) nonimmunosuppressive cyclosporin A analogues; and (x) bicyclic (furanopyrimidine) nucleoside analogues. With the exception of the HIV co‐receptor CCR5 inhibitor none of the compounds described here have already been marketed (for the indication they were initially developed). Successful antiviral drug development depends on the interplay of three disciplines, chemistry, biology/medicine, and industry, crucial factors being open mindedness for the unexpected, preparedness to explore serendipitous observations, and perseverance (in trying) to overcome the hurdles or setbacks inevitably compounding any drug development. © 2009 Wiley Periodicals, Inc. Med Res Rev
The rainbow connectivity of a graph
Authors: Chartrand Gary , Johns Garry L. , McKeon Kathleen A. , Zhang Ping 
Published: February 2009

AbstractA path P in an edge‐colored graph (not necessarily a proper edge‐coloring) is a rainbow path if no two edges of P are colored the same. For an ℓ‐connected graph G and an integer k with 1 ≤ k ≤ ℓ, the rainbow k‐connectivity rck(G) of G is the minimum integer j for which there exists a j‐edge‐coloring of G such that every two distinct vertices of G are connected by k internally disjoint rainbow paths. The rainbow k‐connectivity of the complete graph Kn is studied for various pairs k, n of integers. It is shown that for every integer k ≥ 2, there exists an integer f(k) such that rck(Kn) = 2 for every integer n ≥ f(k). We also investigate the rainbow k‐connectivity of r‐regular complete bipartite graphs for some pairs k,r of integers with 2 ≤ k ≤ r. It is shown that for each integer k ≥ 2, there exists an integer r such that rck(Kr,r) = 3. © 2009 Wiley Periodicals, Inc. NETWORKS, 2009
A survey of some network reliability analysis and synthesis results
Authors: Boesch F.T. , Satyanarayana A. , Suffel C.L. 
Published: February 2009

AbstractThe purpose of this article is to introduce several results concerning the analysis and synthesis of reliable or invulnerable networks. First, the notion of signed reliability domination of systems is described and some applications to reliability analysis are reviewed. Then the analysis problem is considered and a brief summary of the difficulty of calculating various reliability measures is presented. Some relevant concepts in the synthesis of a most reliable network are studied. The article concludes with an introduction to a non‐probabilistic approach to evaluate the vulnerability of a network. © 2009 Wiley Periodicals, Inc. NETWORKS, 2009
A time‐staggered partitioned coupling algorithm for transient heat conduction
Authors: Nakshatrala P. B. , Nakshatrala K. B. , Tortorelli D. A. 
Published: February 2009

AbstractWe present a time‐staggered partitioned coupling algorithm for transient heat conduction finite element simulations. This algorithm divides a large structural mesh into a number of smaller subdomains, solves the individual subdomains separately and couples the solutions to obtain the response to the original problem. The proposed algorithm is a mixed multi‐timestep algorithm and enables arbitrary time integration schemes and meshes to be coupled with different timesteps in the various subdomains. In this procedure, the solution of each partition is separately evaluated over a system timestep after which the interfacial conditions are enforced making this a staggered algorithm that facilitates parallel computation. We present examples showing the feasibility of the coupling algorithm and discuss the merits in terms of convergence and stability. Copyright © 2009 John Wiley & Sons, Ltd.
Transcriptional activation of the β‐catenin gene at the invasion front of colorectal liver metastases
Authors: Bandapalli Obul R , Dihlmann Susanne , Helwa Reham , Macher‐Goeppinger Stephan , Weitz Jurgen , Schirmacher Peter , Brand Karsten 
Published: February 2009

Abstractβ‐Catenin is a pivotal molecule of the Wnt‐signalling pathway, involved in regulation of developmental and oncogenic processes as well as in intercellular adhesion. So far, β‐catenin has been thought to be regulated mainly at the protein level. Here, we provide evidence for a transcriptional mechanism of β‐catenin regulation at the invasion front of colorectal liver metastases. In a nude mouse/LS174T cell xenograft model of colorectal liver metastases, we observed β‐catenin up‐regulation at the mRNA and protein levels and a 13.7‐fold increase of β‐catenin promoter activity in the cancer cells of the invasion front. In addition, the promoter activity was five‐fold higher in the interior of the tumour than in cells growing in cell culture. In vitro studies revealed binding of TCF‐4 to the β‐catenin promoter and reduced promoter activity by over‐expression of dominant negative TCF‐4, or β‐catenin knock‐down and increased activity by β‐catenin over‐expression, indicating that β‐catenin acts as co‐transcription factor of its own promoter. In 55% (7/13) of clinical specimens, β‐catenin mRNA was markedly elevated in the cancer cells of the invasion front. Elevation of mRNA was paralleled by increased nuclear and cytoplasmic β‐catenin protein concentrations. These data indicate that transcriptional regulation contributes to the dynamic changes of β‐catenin levels upon the confrontation of tumour cells with the host microenvironment. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Thermoplastic toughened layered silicate epoxy ternary nanocomposites—Preparation, morphology, and thermomechanical properties
Authors: Asif A. , Rao V. Lakshmana , Saseendran V. , Ninan K.N. 
Published: February 2009

AbstractEpoxy–clay ternary nanocomposites were processed by melt blending of hydroxyl terminated poly (ether ether ketone) oligomer with pendant methyl groups (PEEKMOH) with diglycidyl ether of bisphenol A (DGEBA) epoxy resin along with organically modified montmorillonite (OMC‐OH) followed by curing with 4,4′‐diamino diphenyl sulfone. Small angle X‐ray diffraction and transmission electron microscopy revealed an intercalated morphology. Tensile, flexural, storage, and loss moduli were increased whereas the tensile, flexural, and impact strength and glass transition temperature were decreased with increase in clay content for the PEEKMOH toughened epoxy system. Fracture toughness and percentage strain were increased by 66% and 45% respectively whereas the coefficient of the thermal expansion was decreased by 27% with the incorporation of 1 phr OMC‐OH to the PEEKMOH toughened epoxy system compared with neat epoxy. The scanning electron microscope pictures of fracture and tensile failed surfaces revealed crack path deflection and ductile fracture with the incorporation of OMC‐OH confirming the improvement in toughness. The domain size and the distance between the domains of thermoplastic phase were decreased with the addition of nanoclay into the epoxy matrix indicating the restriction of the growth mechanism by nucleation during phase separation. A marginal increase in thermal stability was observed with increase in clay content. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Study of application of ultrasonic wave to injection molding
Authors: Sato Atsushi , Ito Hiroshi , Koyama Kiyohito 
Published: February 2009

AbstractWe have developed an ultrasonic injection molding (UIM) system, which applies ultrasonic waves to injection molding, as a precision injection molding technology. Molding of optical lenses showed that the lens weight increased when the ultrasonic wave was applied immediately after the resin was filled into a cavity. Results showed that, by applying ultrasonic waves, oscillatory flow was generated inside the cavity and consequently the weight of the lens was increased. The surface finish of the molded lens was also significantly improved in UIM when compared with that in conventional molding. The part of shrinkage during the packing and holding stages was suppressed by the oscillatory flow provided by the ultrasonic vibration. Because of ultrasonic energy absorption, local heating was generated inside the resin, resulting in the formation of oscillatory flow during packing and holdingstages. Local heating, occurring especially between molten and skin layers, reduces the skin layer's deformation resistance. Consequently, replication during the packing and holding stages is facilitated by the UIM. Moreover, evaluation of the residual optical strain of concave lens revealed that the strain was much lower in UIM than in conventional molding. The decreased strain was attributed to the local heat generation by the ultrasonic waves. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Application of gentle annular gas veil for electrospinning of polymer solutions and melts
Authors: Rein D.M. , Cohen Y. , Ronen A. , Shuster K. , Zussman E. 
Published: February 2009

AbstractA novel experimental device for elevated‐temperature electrospinning of highly volatile and quickly crystallizing polymer solutions and melts was developed. The main parameters of gentle annular gas veil in electrospinning process were studied. The influence of electrical conductivity of solvent on the diameter of electrospun fibers from ultra‐high molecular weight polyethylene was experimentally determined. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Solubility of terephthalic acid in the reaction system oligomeric bishydroxybutyl terephthalates—1,4‐butanediol
Authors: Huang Hainan , Zeng Zuoxiang , Xue Weilan , Zhu Wanyu 
Published: February 2009

AbstractThe physical solubilities of terephthalic acid (TPA) in the reaction system oligomeric bishydroxybutyl terephthalates—1,4‐butanediol (BD) are measured using an analytic method from 449 to 507 K. The reaction system is obtained by transesterification of dimethyl terephthalate and excess BD. These results are fitted with the solubility model based on the Margules equation, and the average deviation of the model is 1.20%; the fusion enthalpies ΔHfus of TPA and infinite‐dilution activity coefficients γ∞2 in the system are obtained by regressing of the experimental data. In addition, synthetic method is chosen to determine the total solubility which is complicated by chemical reaction, the results indicate that the chemical reaction start at 452–472 K. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Trials needed to assess knee proprioception following stroke
Authors: Piriyaprasarth Pagamas , Morris Meg E. , Delany Clare , Winter Adele , Finch Sue 
Published: February 2009

AbstractBackground and Purpose. This study explores the number of trials required to identify clinically significant impairments in knee joint position sense and movement sense following stroke. Method. Proprioception was assessed in 33 stroke patients aged 37–87 years. Ten trials for each assessment were performed in sitting and supine positions using both verbal response techniques and contralateral limb matching. Results. Forty‐six percent of participants were identified with a proprioceptive deficit. The trial where the first incorrect response occurred varied across individuals and testing positions. Performing only one trial detected proprioceptive impairments in less than 10% patients, and incorrect responses did not always occur in the first 5 trials. In sitting, no participant failed the assessment of knee joint position sense using the verbal response technique after only 6 trials. In supine, no participant failed the assessment of knee movement sense using the verbal response technique after only 6 trials. For the assessment of knee joint position sense in sitting using contralateral limb matching an estimated 9.4% of patients with a deficit would be missed if only 3 trials were used in preference to 5. For assessment of knee joint position sense in sitting, an estimated 18.8% of patients with deficits would be missed if only 3 trials were used rather than 10 trials. Conclusions. Clinicians should perform at least 10 trials in either sitting or supine to quantify joint position sense and movement sense at the knee following stroke. Copyright © 2009 John Wiley & Sons, Ltd.
Dielectric relaxation and giant dielectric constant of Nb‐doped CaCu3Ti4O12 ceramics under dc bias voltage
Authors: Liu Peng , He Ying , Zhou Jian‐ping , Mu Chun‐hong , Zhang Huai‐wu 
Published: February 2009

AbstractCaCu3Ti4–x Nbx O12 (x = 0, 0.01, 0.08, 0.2) ceramics were fabricated by a conventional solid‐state reaction method. The ceramics showed the body‐centered cubic structure without any foreign phases and the grain size decreases with Nb doping. Two Debye‐type relaxations were observed for the Nb‐doped samples at low frequency and high frequency, respectively. The complex electric modulus analysis revealed that the surface layer, grains and grain boundaries contributed to the dielectric constant. The low‐frequency dielectric constant relative to the surface layer decreased to a minimum and then increased with the dc bias voltage at 100 Hz, which were well explained in terms of a model containing two metal oxide semiconductors in series, confirming the surface layer in the ceramics. The shift voltage VB corresponding to the minimal capacitance increased with increase of the composition x. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies of giant magnetoimpedance effect of Co‐rich microwires in wide frequency range
Authors: Popov V. , Zhukova V. , Ipatov M. , García C. , Gonzalez J. , Ponomarenko V. , Berzhansky V. , Vinogorodsky D. , Zhukov A. 
Published: February 2009

AbstractThe GMI effect in Co‐rich amorphous microwires with nearly‐zero and negative magnetostriction constant has been investigated in the frequency range from a few MHz up to 10 GHz using conventional impedance analyzer based technique and microwave waveguide method. The GMI response of the order of 200% has been observed for all samples at MHz frequencies, while only one samples demonstrated considerable GMI ratio of about 60% at GHz frequencies. This can be explained by the fact that impedance dependence on external magnetic field in the microwaves range is affected not only by the magnetic softness of the wire material but also by the magnetic resonance conditions in the not saturated sample. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monolithically integrated UV/IR‐photodetectors based on an AlN/GaN‐based superlattice grown on an AlGaN buffer layer
Authors: Hofstetter Daniel , Baumann Esther , Giorgetta Fabrizio R. , Théron Ricardo , Guillot Fabien , Monroy Eva , Golka Sebastian , Strasser Gottfried 
Published: February 2009

AbstractIn this article, we demonstrate closely spaced, monolithically integrated photodetectors in two largely different wavelength ranges. The epitaxial structure of the devices was grown by plasma‐assisted molecular‐beam epitaxy on an AlN‐on‐sapphire template; it consists of a Si‐doped AlGaN thin film, and a nearly strain compensated 40 period AlN/GaN superlattice with 1.0 nm thick GaN quantum wells and 2.0 nm thick AlN barriers. The entire structure is covered with an AlGaN cap layer. The superlattice acts as active region for the infrared detector, while the AlGaN buffer layer serves as active area for the ultraviolet detector. While the photovoltaic near‐infrared detector has a center wavelength of 1.37 μm, the photoconductive ultraviolet detector has a long wavelength cutoff at 250 nm. The two detectors could be operated up to room temperature with reasonable sensitivities. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel tunable phosphor‐free white III‐nitride light emitting diodes based on indium rich InGaN nanostructures
Authors: Soh C. B. , Liu W. , Chua S. J. , Teng J. H. , Tan Rayson J. N. , Ang S. S. 
Published: February 2009

AbstractPhosphor free tunable white light emitting diodes (LEDs) have been fabricated using stacked InGaN/GaN quantum wells (QWs) comprised of a lower set of red emitting QWs with an upper set of blue and green emitting QW layers. With antisurfactant treatment, indium rich InGaN nanostructures are incorporated in the InGaN/GaN quantum well during growth. AFM study shows the formation of InGaN nanostructures with an average diameter of 40‐80 nm in the quantum well layer. This growth technique enables red emitting III‐Nitride based LEDs to be generated. With the growth of additional stacked blue/green QWs on these red emitting QWs with InGaN nanostructure incorporation for white light generation, competition arises between the quantum well layers for thermalization of injected carriers. The transport of holes from the p‐GaN layer determines the radiative recombination event as holes have a lower mobility than electrons. At low injection current, emission from the upper blue/green QWs layer dominates where electron–hole (e–h) pair recombination takes place. With higher injection current, more holes diffuse across the GaN barrier to recombine with electrons at the InGaN nanostructures in the lower sets of QWs. Based on the band structure for the stacked QWs, the existence of these In‐rich nanostructures leads to more effective carrier trapping at the lower set of QWs as electrons have to overcome an additional potential barrier (at the interface of InGaN nanostructures to the InGaN well layer). There is also a higher tendency for thermalization of carriers at the lower energy states. The effect of band filling under higher injection current also enables the excess holes to recombine at the lower set of QW layers with indium rich nanostructure, which accounts for the continuous increase in higher emission wavelength from the EL spectra. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental method for scanning the surface depletion region in nitride based heterostructures
Authors: Netzel Carsten , Skriniarova Jaroslava , Herms Martin , Wenzel Hans , Hoffmann Veit , Knauer Arne , Weyers Markus 
Published: February 2009

AbstractThe group‐III‐nitride semiconductors feature strong spontaneous polarization in the [0001] direction and charges on the respective polar surfaces. Within the resulting surface depletion region the surface field causes band banding and affects the optical transitions in quantum wells. We studied the changes of the emission characteristics of a single GaInN quantum well when its distance to the surface and the influence of the surface field varies. We observe a strong increase of the quantum well emission energy and a decrease of the line width when the surface field partially compensates the piezoelectric field of the quantum well. A scan of the total surface depletion region with a single quantum well as probe was performed. The obtained emission data allow for the direct determination of the width of the depletion region. The experimental method is promising for studies of the surface field and the surface potential of III‐nitride surfaces and interfaces. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhancement in electrical properties of GaN heterostructure field‐effect transistor by Si atom deposition on AlGaN barrier surface
Authors: Onojima Norio , Hirose Nobumitsu , Mimura Takashi , Matsui Toshiaki 
Published: February 2009

AbstractThis study demonstrates that deposition of Si atoms on AlGaN barrier surfaces in GaN heterostructure field‐effect transistors (HFETs) can modulate the electrical properties of the two‐dimensional electron gas (2DEG). The results of Hall measurements performed using the eddy current and four‐point van der Pauw methods showed that the sheet resistance of an AlGaN/GaN HFET sample without surface passivation increased from that of the unprocessed sample after post‐metallization annealing at 820 °C for ohmic contacts. In contrast, the sheet resistance of the Si‐deposited sample did not increase even after annealing. Furthermore, eddy current measurements for unprocessed wafers with and without Si deposition revealed that the sheet resistance can be reduced by depositing Si atoms, regardless of annealing. The effect of Si deposition on devices having a thin Al‐rich barrier layer was found to be significant. The deposition of Si atoms (2 nm) on the AlN barrier surface in an AlN/GaN HFET (AlN 2 nm) resulted in a remarkable decrease in the sheet resistance from 60356 to 388 Ω/sq. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
HVPE growth of AlxGa1–xN alloy layers
Authors: Hagedorn Sylvia , Richter Eberhard , Netzel Carsten , Zeimer Ute , Weyers Markus , Tränkle Günther 
Published: February 2009

AbstractIn this work growth of AlxGa1–xN layers (0 < x < 0.91) by hydride vapour phase epitaxy (HVPE) is presented. The growth process is performed in a modified horizontal reactor. The measured compositions show good agreement with theoretical values calculated from a heterogeneous thermodynamic equilibrium model. The aluminum mole fractions, the homogeneity and the relaxation of the AlxGa1–xN layers are deduced from x‐ray diffraction (XRD) measurements. Cathodoluminescence (CL) investigations of an Al0.52Ga0.48N sample exhibit a luminescence peak energy near the expected band edge and an additional luminescence peak between the AlxGa1–xN and the GaN bandgap. From XRD and spatially resolved CL measurements the peak at lower energy can be associated to crystallites with orientation different from the c‐plane bulk layer that are formed on the growing surface. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of 3D InGaN/GaN structures providing semipolar GaN planes for efficient green light emission
Authors: Wunderer T. , Lipski F. , Hertkorn J. , Schwaiger S. , Scholz F. 
Published: February 2009

AbstractA fabrication method for the formation of 3D GaN structures with reduced piezoelectric field is presented. Via optimized selective epitaxy the surface is just composed of hexagonally patterned semipolar {1$ \bar 1 $01} or {11$ \bar 2 $2} planes. GaN growth with less NH3 at a higher growth speed, a doubled effective area and good light outcoupling properties compared to c‐plane growth are additional advantages of this effective technique.The high material quality is confirmed via PL measurements. No defect related optical transitions, often observed in non‐ and semipolar GaN, were found. An In‐GaN QW grown on these semipolar planes showed efficient green (522 nm) light emission in spite of a reduced influence of the quantum confined stark effect (QCSE) (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)