bluuebunny/crossref_metadata_2025 huggingface dataset:
A wideband Gilbert cell mixer with an integrated Marchand balun using 0.5‐μm GaAs enhancement‐mode pHEMT technology
Authors: Fu Jeffrey S. , Kuo Che‐Yu , Lin Shao‐Wei , Ke Po‐Yu , Chiu Hsien‐Chin
Published: March 2010

In this study, a fully integrated active Gilbert cell mixer with two Marchand baluns was proposed.The proposed circuit was designed at 12 GHz with bandwidth from 7.5 to 19 GHz and fabricated in a 0.5‐μm pHEMT process. In addition, the “current bleeding” technique was also provided in the Gilbert cell mixer to boost the conversion gain. The greatest conversion gain of 4.5 dB can be achieved in the designed circuit under LO input power of −2 dBm. Both RF‐IF and LO‐IF isolations were better than 30 dB. The third order intercept point input power, IIP3, achieved as high as 2 dBm. The mixer works from 7.5 to 19 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1302–1306, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25174
Miniaturized band‐pass filters using closed‐loop microstrip ring resonator with parallel‐coupled feed
Authors: Athukorala L. , Budimir D.
Published: March 2010

Novel compact band‐pass filters and diplexer using microstrip ring resonator with parallel‐coupled feed are presented. Overall size reductions depend on the amount of meandering used and 56% size reduction is achieved. The proposed filters and diplexer are designed and tested. The experimental and simulation results are presented to validate the argument. Good agreement between simulated and measured result is observed. The filters and diplexer are relatively easy to manufacture and are very suitable for broadband communication systems where size and weight minimization are essential. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1277–1280, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25188
Design of a broadband balun based on composite right/left handed structure
Authors: Cao Weiping , Guo Feng , Wang Bingzhong
Published: March 2010

A new printed Wilkinson balun based on the nonlinear phase characteristics of composite right/left handed (CRLH) structure is presented.The new device, which differs from the traditional CRLH balun, is composed of a Wilkinson power divider, a distributed CRLH transmission line (TL), and a conventional TL. It can be easily applied to MIC/MMIC circuits. Full‐wave simulations and measurement results verify the effectiveness of the new structure. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1310–1313, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25189
Characteristics of a 60 GHz MMIC mixer with an open stub microstrip line
Authors: Lee Sang‐Heung , Lim Jong‐Won , Ahn Hokyun , Chang Woojin , Ji Hong Gu , Kim Haecheon , Nam Eun Soo
Published: March 2010

In this article, 60 GHz MMIC down‐conversion mixers for a 60 GHz communication system are designed and fabricated on‐chip using a 0.12 μm GaAs PHEMT process technology with an fT of 78 GHz and fmax of 190 GHz.The characteristics of a 60 GHz monolithic cascode mixer with an open stub microstrip line are compared with those of a 60 GHz monolithic cascode mixer without an open stub microstrip line, which are integrated on‐chip including matching and bias circuits. The 60 GHz monolithic cascode mixer with an open stub microstrip line measured at RF 60 GHz show a conversion gain of −16 dB, LO to RF isolation of 21.5 dB, and LO to IF isolation of 40.5 dB. Especially in the case of the mixer, the LO to IF isolation characteristic is much better than that of the 60 GHz monolithic cascode mixer without an open stub microstrip line. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1341–1345, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25191
Drain efficiency amplifier of 50% with optimized power range for CDMA base station
Authors: Zheng Guangming , Lin Weigan
Published: March 2010

A novel high‐efficiency Doherty amplifier is presented here.A carrier amplifier and a peak amplifier are set to asymmetrical drain voltages to extend the power range where a high efficiency of the amplifier is maintained. In Doherty amplifier, matching circuits of the carrier amplifier and peak amplifier are designed for each drain voltage so that the efficiency and signal linearity of the amplifier at a 7.2 dB back‐off point from its saturated output power become higher than those of a conventional amplifier. A Doherty amplifier containing laterally‐diffused metal‐oxide semiconductor field‐effect transistors achieves an adjacent channel leakage power ratio of −30.89 dBc and a drain efficiency of 50% at an output power of 49.3 dBm. This is the highest drain efficiency of a Doherty amplifier for a CDMA signal to the best of the authors' knowledge. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1244–1246, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25195
A coupling‐fed multiband antenna for WLAN/WiMAX applications
Authors: Zuo Shaoli , Yin Yingzeng , Zhang Zhiya
Published: March 2010

A coupling‐fed printed monopole antenna applied to wireless local area network/worldwide interoperability for microwave access (WLAN/WiMAX) applications is proposed. By using a pair of branch‐shaped strips, which are symmetrical with a gradual changing strip, the proposed antenna exhibits multiband performance to meet the requirements of WLAN in the 2.4/5.2/5.8 GHz bands and WiMAX in the 2.5/3.5/5.5 GHz bands. The proposed antenna has good omnidirectional radiation characteristic owing to its symmetric structure and achieves gains to be 2.44, 3.74, 3.3, and 2.02 dBi at 2.4, 3.5, 5.2, and 5.8 GHz, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1283–1286, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25197
Methodology for all‐fiber optical active devices by composing the stimulated Brillouin scattering spectra
Authors: Galindez C. A. , Madruga F.J. , López‐Higuera J. M.
Published: March 2010

The methodology for reshaping and enlarging the Brillouin gain spectral response is proposed in this article as a technique to develop all‐fiber optical active devices. It is based on the superposition of the Brillouin scattering spectra from several optical fibers, which are connected in serial, parallel, or both. Additionally, the overall Brillouin gain spectral response can be tailored or customized by tuning the temperature or the strain on the fiber. To experimentally demonstrate the method, we propose a fiber device with a tailored like “W” spectral response. The bandwidth is 190 MHz at 3 dB, centered in 10.765 GHz from the pump wavelength. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1316–1318, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25199
Optical fiber arterial pulse wave sensor
Authors: Eom Sunghoon , Park Jaehee , Lee Jonghun
Published: March 2010

An optical fiber arterial pulse wave sensor is proposed using an in‐line Michelson interferometer that is a hollow optical fiber spliced to a single‐mode fiber at one end and cleaved at the other end. The proposed optical fiber arterial pulse wave sensor consists of an in‐line Michelson interferometer and steel reinforcement enclosed in a heat‐shrinkable tube. The sensor was directly attached onto a wrist and signals corresponding to arterial pulse waves successfully obtained. The signal‐to‐noise ratio of the sensor signals was better than 20 dB. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1318–1321, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25200
Concurrent dual‐band six‐loop‐antenna system with wide 3‐dB beamwidth radiation for MIMO access points
Authors: Su Saou‐Wen
Published: March 2010

A high‐gain, wide‐beamwidth, six‐loop‐antenna MIMO system suited for wireless access points in the concurrent WLAN 2.4 and 5 GHz bands is presented.The antenna system mainly comprises an antenna ground plane and single‐band loop antennas, among which the three antennas are designated for 2.4 and 5 GHz operation, respectively. The antennas are set in a sequential, rotating arrangement on the ground plane with an equal inclination angle of 60° to form a symmetrical structure, and the 2.4 and 5 GHz loops are facing each other one by one. The experimental results show that good port isolation can be obtained between antenna ports. High‐gain, directional radiation patterns with wide 3‐dB beamwidth in elevation planes are also observed. Details of a design prototype are described and discussed in the article. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1253–1258, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25208
Trifluoromethylated (tetrahydropyrrolo) quinazolinones by a new three‐component reaction and facile assignment of the regio‐ and stereoisomers formed by NMR spectroscopy
Authors: Dolenský Bohumil , Kvíčala Jaroslav , Paleta Oldřich , Lang Jan , Dvořáková Hana , Čejka Jan
Published: March 2010

A new three‐component cyclisation reactions of methyl 3,3,3‐trifluoropyruvate, 2‐aminobenzylamine and oxo compounds afforded tetrahydropyrroloquinazolinones of the types 4 and 5 as mixtures of regio‐ and stereoisomers. Whereas standard 1D NMR spectroscopy was used for a facile assignment of the cyclization regioisomers, a combination of homo (proton–proton) and heteronuclear (proton–fluorine) NOE experiments allowed the determination of the relative configuration on stereogenic centres. The structure of some compounds was also confirmed by the X‐ray diffraction. Adaptation of the 1D double‐pulsed field‐gradient spin‐echo NOE for a heteronuclear case is presented. Copyright © 2010 John Wiley & Sons, Ltd.
Relative acidities and structure analysis of cis and trans isomers of 1,5‐oxazaspiro[5.5] undecane derivatives by multinuclear magnetic resonance
Authors: Guerrero‐Álvarez Jorge Antonio , Mas‐Ku Wendy Paloma , Garcías‐Morales Cesar , Ariza‐Castolo Armando
Published: March 2010

The relative acidities of the cis and trans isomers of a series of 1,5‐oxazaspiro[5.5]undecane derivatives were determined by measuring ΔpK in acid‐base titrations followed by 1 H NMR. Relative structural stabilities were determined by measuring substituent chemical shift and γ‐gauche effects in 13C, 15N, and 17O NMR. Crystallographic characterization of a model spiro[5.5]undecane is presented to support the basicity in solid state. Copyright © 2010 John Wiley & Sons, Ltd.
Synthesis, 1H and 13C NMR assignment and electrochemical properties of novel thiophene–thiazolothiazole oligomers and polymers
Authors: Van Mierloo S. , Chambon S. , Boyukbayram A. E. , Adriaensens P. , Lutsen L. , Cleij T. J. , Vanderzande D.
Published: March 2010

Novel hexyl‐substituted bisthiophene compounds containing a thiazolothiazole(5,4‐d) unit have been explored. The molecules are soluble in common organic solvents, which would enhance their chance of possible integration in printable electronics. Synthesis and complete elucidation of the chemical structures by detailed 1D/2D NMR spectroscopy are described. This provides interesting input for chemical shift prediction software, because few experimental data on this type of compounds are available. Furthermore, the potential n‐type character of these derivatives is verified using electrochemical measurements. In addition, the low‐bandgap character of conjugated polymers containing the thiazolothiazole unit is demonstrated by performing an electropolymerization. Copyright © 2010 John Wiley & Sons, Ltd.
Kinetic Modeling of Surface‐Initiated Atom Transfer Radical Polymerization
Authors: Gao Xiang , Feng Wei , Zhu Shiping , Sheardown Heather , Brash John L.
Published: March 2010

A kinetic model has been developed using the method of moment for surface‐initiated atom transfer radical polymerization (s‐ATRP) from flat solid surfaces based on a moving boundary physical model. The model is verified with the experimental data of 2‐methacryloyloxyethyl phosphorylcholine from silicon wafer, which were carried out by either adding free initiator (Method I) or excess deactivator (Method II) to the solution. It is shown through the modeling that Method II gives better control over polymer molecular weight and thicker graft layer under similar conditions than Method I. A new mechanism is proposed for the radical termination based on the fact that the rapid activation/deactivation cycle reactions facilitate “migration” of radical centers on the surface. The rate constant of “migration termination” is thus catalyst concentration dependent with higher catalyst concentration resulting in higher termination. Lowering catalyst concentration suppressed migration termination that could improve the control and livingness of s‐ATRP. However, there exists a catalyst concentration for the optimal control performance.

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Teaching medical students about chronic disease: patient‐led teaching in rheumatoid arthritis
Authors: Phillpotts Clare , Creamer Paul , Andrews Tanya
Published: March 2010

Objectives: To evaluate the effectiveness of patient‐led teaching compared with doctor‐led teaching, regarding the impact of chronic disease (rheumatoid arthritis [RA]).

Methods: A set of learning objectives regarding the impact of RA on patient and family was designed. Students (n = 42) attached to the academy for their musculoskeletal diseases module were randomized to teaching either by a doctor or a patient. Outcome was assessed using a knowledge test, feedback forms and qualitative written interview.

Results: In the knowledge test, the groups performed equally. The patient‐taught group scored 24.5 ± 3.5 (max 35); the doctor‐taught group scored 24.6 ± 4.1 (p > 0.05; NS). Feedback was completed by 40/42 students. Mean scores for the overall grading of teaching (1–5, where 1 = worst, 5 = best) were: patient teaching 4.36 (95% confidence interval [CI] 4.11, 4.61); doctor teaching 3.69 (95% CI 3.52, 3.92).The difference between the average scores was 0.42 (p = 0.005). Qualitative feedback showed recurring themes that students appreciated the personal nature of the patient's teaching, enabling them to understand the impact of the disease on patients and their families. The doctors' teaching was also appreciated, particularly the interactive style and opportunity to participate in role play.

Conclusions: We have demonstrated that our patient was at least as good as a doctor at teaching about the impact of chronic disease on patients. Furthermore, this experience is valued by students who appreciate the personal insight that a patient can offer. Copyright © 2010 John Wiley & Sons, Ltd.
Homogenization and two‐scale simulations of granular materials for different microstructural constraints
Authors: Miehe C. , Dettmar J. , Zäh D.
Published: March 2010

The paper presents a new method for quasi‐static homogenization of granular microstructures and its embedding into two‐scale simulations. On the coarse scale, a homogenized standard continuum is considered where the granular microstructures are locally attached at each point. These representative volumes are defined by aggregates of discrete solid particles, which may come into contact. On the micromechanical side, the interparticle contact mechanisms between particles is governed by a Coulomb‐type frictional contact. In particular, elliptical‐shaped plane particles are investigated. A consistent extension of classical stiff, soft and periodic boundary conditions from continuous to granular microstructures induce new classes of micro‐to‐macro transitions for granular aggregates. These include constraints not only for particle center displacements but also for particle rotations at a driving boundary frame. The stiff and soft constraints at the driving frame of the particle aggregate induce upper and lower bounds of the particle aggregate's stiffness. On the computational side, we outline a unified implementation of the displacement and rotational constraints by penalty methods that proves to be convenient for straightforward integration into discrete element codes. Representative numerical examples with elliptical‐shaped particles are investigated, where the macroscopic stress responses for different boundary constraints are comparatively discussed. Finally, we embed the granular microstructures into a coarse graining discrete‐to‐finite element model, where they govern the micromechanical behavior of a two‐scale simulation. Copyright © 2010 John Wiley & Sons, Ltd.
Frequent genomic structural alterations at HPV insertion sites in cervical carcinoma
Authors: Peter Martine , Stransky Nicolas , Couturier Jérôme , Hupé Philippe , Barillot Emmanuel , de Cremoux Patricia , Cottu Paul , Radvanyi Francois , Sastre‐Garau Xavier
Published: March 2010

To investigate whether integration of HPV DNA in cervical carcinoma is responsible for structural alterations of the host genome at the insertion site, a series of 34 primary cervical carcinomas and eight cervical cancer‐derived cell lines were analysed. DNA copy number profiles were assessed using the Affymetrix GeneChip Human Mapping 250K Sty array. HPV 16, 18 or 45 integration sites were determined using the DIPS‐PCR technique. The genome status at integration sites was classified as follows: no change, amplification, transition normal/gain, normal/loss or gain/LOH. A single HPV integration site was found in 34 cases; two sites were found in seven cases; and three sites in one case (51 sites). Comparison between integration sites and DNA copy number profiles showed that the genome status was altered at 17/51 (33%) integration sites, corresponding to 16/42 cases (38%). Alterations detected were amplification in nine cases, transition normal/loss in four cases, normal/gain in three cases, and gain/LOH in one case. A highly significant association was found between genomic rearrangement and integration of HPV DNA (p < 10−10). Activation of the replication origin located in viral integrated sequences in a cell line derived from one of the primary cervical carcinomas induced an increase of the amplification level of both viral and cellular DNA sequences flanking the integration locus. This mechanism may be implicated in the triggering of genome amplification at the HPV integration site in cervical carcinoma. Structural alterations of the host genome are frequently observed at the integration site of HPV DNA in cervical cancer and may act in oncogenesis. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Anaplastic plasmacytoma of mouse—establishing parallels between subtypes of mouse and human plasma cell neoplasia
Authors: de Jong Daphne , Janz Siegfried
Published: March 2010

Mouse models may provide an important tool for basic and applied research on human diseases. An ideal tumour model should replicate the phenotypic and molecular characteristics of human malignancy as well as the typical physiological effects and dissemination patterns. The histopathological and molecular genetic characterization of anaplastic plasmacytoma (APCT) in strain NSF.V+ mice provides an example to achieve this goal for a specific lymphoma subtype. Firstly, it demonstrates that, like plasma‐cell neoplasms in humans, those in mice occur as distinct subtypes. Secondly, it shows that mouse APCT exhibits striking parallels to possible human tumour counterparts for which good mouse models of de novo tumour development are sorely needed: IgM+ multiple myeloma and Waldenström's macroglobulinaemia. Thirdly, it strongly suggests that insertional somatic mutagenesis, by either a murine leukaemia virus or an oncogenic transposon, would be an effective experimental approach to accelerating malignant transformation of mature B cells and plasma cells in mice and, thereby, tagging and uncovering cancer driver genes that may be of great relevance for the tumour initiation and progression in lymphoma. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Issues in multiple imputation of missing data for large general practice clinical databases
Authors: Marston Louise , Carpenter James R. , Walters Kate R. , Morris Richard W. , Nazareth Irwin , Petersen Irene
Published: March 2010

Purpose

Missing data are a substantial problem in clinical databases. This paper aims to examine patterns of missing data in a primary care database, compare this to nationally representative datasets and explore the use of multiple imputation (MI) for these data.

Methods

The patterns and extent of missing health indicators in a UK primary care database (THIN) were quantified using 488 384 patients aged 16 or over in their first year after registration with a GP from 354 General Practices. MI models were developed and the resulting data compared to that from nationally representative datasets (14 142 participants aged 16 or over from the Health Survey for England 2006 (HSE) and 4 252 men from the British Regional Heart Study (BRHS)).

Results

Between 22% (smoking) and 38% (height) of health indicator data were missing in newly registered patients, 2004–2006. Distributions of height, weight and blood pressure were comparable to HSE and BRHS, but alcohol and smoking were not. After MI the percentage of smokers and non‐drinkers was higher in THIN than the comparison datasets, while the percentage of ex‐smokers and heavy drinkers was lower. Height, weight and blood pressure remained similar to the comparison datasets.

Conclusions

Given available data, the results are consistent with smoking and alcohol data missing not at random whereas height, weight and blood pressure missing at random. Further research is required on suitable imputation methods for smoking and alcohol in such databases. Copyright © 2010 John Wiley & Sons, Ltd.
Crystallization and spherulitic growth kinetics of poly(trimethylene terephthalate)/polycarbonate blends
Authors: Shafee Ez El , Naguib Halla F. , Li Longfei , Jiang Shichun , An Lijia
Published: March 2010

The macroscopic and microscopic melt‐crystallization kinetics of poly(trimethylene terphthalate) (PTT)/polycarbonate (PC) blends have been measured by differential scanning calorimetry (DSC), and optical microscopy (OM). The results are analyzed in terms of the Avrami equation and the Hoffman–Lauritzen crystallization theory (HL model). Blending with PC did not change the crystallization mechanism of PTT, but reduced the crystallization rate compared with that of neat PTT at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature. The spherulitic morphology of PTT was influenced apparently by the crystallization temperature and by the addition of PC. X‐ray diffraction shows no change in the unit cell dimension of PTT was observed after blending. Through the HL theory, the classical regime II→III transition was detected for the neat PTT and the blends. The nucleation parameter (Kg), the fold‐surface free energy (σe), and the work of chain folding (q) were calculated. Blending with PC decreased all the aforementioned parameters compared with those of neat PTT. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Low viscous hydrophilic processing additives for extrusion of polyethylene at reduced temperatures
Authors: Kulikov Oleg , Hornung Klaus , Wagner Manfred
Published: March 2010

Industry is using fluorinated polymer processing additives (PPA) to delay the onset of sharkskin to higher rates of extrusion of PE resins. Yet it is necessary to keep elevated temperatures during extrusion to reduce apparent melt viscosity. We propose to use low viscous PPA made from reacting mixtures of polyethylene glycol with organic polyacids, phosphoric acid, and polyesters of oxiacids of Phosphorus. Surprisingly, extrusion pressures and apparent viscosity with the novel PPA at reduced temperatures are less, than at elevated temperatures. In total, extrusion pressures can be reduced 2–5 times for concentrations of PPA from 0.1 to 0.5 wt%, while sharkskin melt fracture can be eliminated for concentrations of PPA above 0.02 wt%. Extrusion with the novel PPA at reduced temperatures potentially increases productivity, reduces production cost, and allows processing of PE resins ofhigher MW and highly filled polymer composites. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Automatic velocity profile determination for uniform filling in injection molding
Authors: Chen Xi , Zhang Lei , Kong Xiangsong , Lu Junde , Gao Furong
Published: March 2010

The filling phase plays an important role in determining the quality of injection molded parts. Uniform melt‐front velocity has been recommended for minimizing the part non‐uniformity. On the basis of a capacitive transducer that has been developed for online measurement of melt front velocity, we propose an intelligent strategy for profiling injection velocity. The nonlinear response of melt development in a mold cavity is first acquired with a constant screw injection velocity. On the basis of this response, a stage division method is proposed to determine an appropriate stage number of a piecewise linear profile and the locations of the switch points. An optimization based on sequential simplex search is then conducted to search for the optimal profile of injection velocity. Online experimental tests on molds with different geometries show that the proposed method is effective in achieving a uniform mold filling. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Effect of applied voltage on surface and volume charge density of the jet in electrospinning of polyacrylonitrile solutions
Authors: Fallahi D. , Rafizadeh M. , Mohammadi N. , Vahidi B.
Published: March 2010

To investigate the effect of applied voltage on jet charge density, one must investigate its effect on the jet electric current and flow rate. However, there are some difficulties in measuring the jet flow rate. Here, the electrospinning jet flow rate is calculated by applying a new method and the effects of applied voltage and feed rate on jet charge density are investigated. The jet flow rate was independent of the feed rate and increased on increasing the applied voltage. By defining an experimental equation for dependence of jet flow rate on jet current, a relation between jet volume charge density and jet current could be defined. By measuring the electrospun fiber diameter, surface charge density of the jet could be estimated. On increasing the voltage, the jet volume charge density decreased whereas the jet surface charge density remained unchanged. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers
Design, selection, and characterization of a split chorismate mutase
Authors: Müller Manuel M. , Kries Hajo , Csuhai Eva , Kast Peter , Hilvert Donald
Published: March 2010

Split proteins are versatile tools for detecting protein–protein interactions and studying protein folding. Here, we report a new, particularly small split enzyme, engineered from a thermostable chorismate mutase (CM). Upon dissecting the helical‐bundle CM from Methanococcus jannaschii into a short N‐terminal helix and a 3‐helix segment and attaching an antiparallel leucine zipper dimerization domain to the individual fragments, we obtained a weakly active heterodimeric mutase. Using combinatorial mutagenesis and in vivo selection, we optimized the short linker sequences connecting the leucine zipper to the enzyme domain. One of the selected CMs was characterized in detail. It spontaneously assembles from the separately inactive fragments and exhibits wild‐type like CM activity. Owing to the availability of a well characterized selection system, the simple 4‐helix bundle topology, and the small size of the N‐terminal helix, the heterodimeric CM could be a valuable scaffold for enzyme engineering efforts and as a split sensor for specifically oriented protein–protein interactions.
Backbone additivity in the transfer model of protein solvation
Authors: Hu Char Y. , Kokubo Hironori , Lynch Gillian C. , Bolen D. Wayne , Pettitt B. Montgomery
Published: March 2010

The transfer model implying additivity of the peptide backbone free energy of transfer is computationally tested. Molecular dynamics simulations are used to determine the extent of change in transfer free energy (ΔGtr) with increase in chain length of oligoglycine with capped end groups. Solvation free energies of oligoglycine models of varying lengths in pure water and in the osmolyte solutions, 2Murea and 2MtrimethylamineN‐oxide (TMAO), were calculated from simulations of all atom models, and ΔGtrvalues for peptide backbone transfer from water to the osmolyte solutions were determined. The results show that the transfer free energies change linearly with increasing chain length, demonstrating the principle of additivity, and provide values in reasonable agreement with experiment. The peptide backbone transfer free energy contributions arise from van der Waals interactions in the case of transfer to urea, but from electrostatics on transfer to TMAO solution. The simulations used here allow for the calculation of the solvation and transfer free energy of longer oligoglycine models to be evaluated than is currently possible through experiment. The peptide backbone unit computed transfer free energy of −54 cal/mol/M compares quite favorably with −43 cal/mol/M determined experimentally.
Dimer–monomer equilibrium of human thymidylate synthase monitored by fluorescence resonance energy transfer
Authors: Genovese Filippo , Ferrari Stefania , Guaitoli Giambattista , Caselli Monica , Costi M. Paola , Ponterini Glauco
Published: March 2010

An ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43′ with an excitation energy donor/acceptor pair. The dimer–monomer equilibrium of the enzyme is then characterized through steady‐state fluorescence determination of the intersubunit resonance energy transfer efficiency.
Chronic systemic hypoxia promotes LNCaP prostate cancer growth in vivo
Authors: Terraneo Laura , Bianciardi Paola , Caretti Anna , Ronchi Raffaella , Samaja Michele
Published: March 2010

OBJECTIVE

Solid tumors contain underperfused regions where hypoxia‐inducible factor‐1α (HIF‐1α) over‐expression induces hypoxia adaptation and cell proliferation. We test the hypothesis that systemic hypoxia promotes prostate cancer growth in vivo and examine HIF‐1α centrality in this effect.

METHODS

Male athymic mice were xenografted with 3 × 106 LNCaP cells per each flank and exposed for 28 days to either chronic hypoxia (CH, 10% O2) or CH with reoxygenation (CHReox, 3 times/week for 1 hr), with normoxia as control (n = 17, 9, and 20, respectively). At the end of the observation, mice were euthanized and tumors harvested for analyses.

RESULTS

The successful xenografts grew faster in CH and CHReox than in normoxia (first‐order rate constants 0.15 ± 0.01, 0.18 ± 0.03, and 0.09 ± 0.01 day−1, P < 0.05, n = 18, 15, and 25, respectively). Furthermore, the tumor masses at the end were 4.09 ± 0.58, 3.42 ± 0.55, and 1.86 ± 0.25 mg/g bw (P < 0.05), respectively. HIF‐1α, assayed by Western blot and immunofluorescence, was slightly increased in CH with respect to normoxia, but markedly over‐expressed (5–10 times) in CHReox (P < 0.001). The tumor hemoglobin content, higher in CH and CHReox than in normoxia, reflected the higher blood hemoglobin concentration, not neovascularization, as supported by similar expression levels of vascular endothelial growth factor (VEGF) in the three groups. By contrast, protein kinase B (Akt) was more phosphorylated in both hypoxic groups than in normoxia (P < 0.01).

CONCLUSION

In vivo systemic hypoxia promotes prostate cancer growth regardless of HIF‐1α expression level and neovascularization, suggesting an important role for hypoxia‐dependent pathways that do not involve HIF‐1α, as the phosphatidyl inositol‐3‐phosphate signaling cascade. Prostate 70: 1243–1254, 2010. © 2010 Wiley‐Liss, Inc.
ToF‐SIMS investigations of adsorbed proteins on dental titanium
Authors: Wald J. , Müller C. , Wahl M. , Hoth‐Hannig W. , Hannig M. , Kopnarski M. , Ziegler C.
Published: March 2010

Two model proteins, bovine serum albumin (BSA) and lysozyme (LSZ), were used to study adsorption behavior on dental titanium by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Protein films were prepared as single component layers and as mixtures of the two proteins. Additionally, the behavior of consecutive adsorption of both proteins was investigated. The obtained data were analyzed by means of principal component analysis (PCA). Dental titanium samples with a layer consisting of simply one protein could be separated from each other by selecting amino acid related peaks and using PCA or samples coated with a mixture of both proteins, the differentiation was also possible. The partial displacement of LSZ molecules by BSA was shown in the case of simultaneous adsorption. The consecutive adsorption of BSA and subsequently LSZ resulted in layers with a bigger amount of LSZ than of BSA compared to the layers obtained by simultaneous adsorption.
Application of segmented flow for quality control of food using microfluidic tools
Authors: Schemberg Jörg , Grodrian Andreas , Römer Robert , Cahill Brian P. , Gastrock Gunter , Lemke Karen
Published: March 2010

The integration of segmented flow into the development of a new rapid detection method for food‐borne pathogens is presented. The workflow is subdivided into different steps. The selective part is to catch contaminants from the food matrix. Afterward, the fluorescently labeled target cells converted from the cell suspension into droplets (nl‐scale). For this, microfluidic tools like glass or polydimethylsiloxane (PDMS) chips are necessary. It is the main step to determine the amount of contaminants (target cells) fluorescently inside one droplet. Therefore the number of target cells was detected by means of a microscope or by generating one droplet with one fluorescent target cell spectroscopically based on a yes‐ or no‐decision. For a competitive platform, PDMS as a cost‐effective chip‐module was integrated into an automatic microscopic detection system. For quality control during routine analysis a commercial spectroscopic detection system was used to measure the fluorescence signal. Based on these efforts a prototype design for spectroscopic detection was developed.
Fabrication and application of a microfluidic‐embedded silicon nanowire biosensor chip
Authors: Vu Xuan Thang , Stockmann Regina , Wolfrum Bernhard , Offenhäusser Andreas , Ingebrandt Sven
Published: March 2010

We report the fabrication of a silicon nanowire (SiNW) transistor array realized in a top‐down process on 4′′ silicon‐on‐insulator (SOI) wafers. This process is a second, optimized version combining thermal nanoimprint lithography and wet chemical etching to define planar nanowires and contact lines out of the top silicon layer in one etching step. We used ion implantation to reduce series resistance of source and drain contact lines. In total 56 individually addressable SiNWs were aligned in two lines. Wires dimensions were down to 60 nm in width and 40 nm in height having lengths up to 40 µm. Due to an improved processing we obtained almost identical wire structures and electronic properties throughout the 4′′ wafer enabling direct comparison of signals from one chip. The wires were capped by a microfuidic structure, which was used to administer different analyte solutions. First pH characterization measurements and molecular detection experiments using charged polyelectrolytes (PEs) and poly(D)lysine were successful. In future these devices could be used to observe diffusion of analytes in a time‐dependent, spatially‐ and quantitatively‐resolved readout.
GaAs nanowires grown by MOVPE
Authors: Bauer Jens , Paetzelt Hendrik , Gottschalch Volker , Wagner Gerald
Published: March 2010

GaAs nanowire (NW) growth was studied by metal‐organic vapour phase epitaxy (MOVPE). The vapour–liquid–solid (VLS) mechanism with gold‐based alloy particles and the selective‐area growth (SAG) mechanism on electron beam lithographically prepared SiNx/GaAs mask structures were applied. A special focus is set on thermodynamic aspects of the VLS process. The alloy particle formation and the influence of MOVPE growth parameters on the growth rate and the GaAs NW morphology are examined. Furthermore, the improvement of the real structure with particular interest on the twin formation is studied. Besides the commonly used continuous VLS growth mode also a pulsed VLS growth mode with alternating precursor supply is reported. Based on photoluminescence measurements the effect of strain in core/shell NW structures is confirmed. For the SAG mechanism the MOVPE growth parameters are determined and the real structure is described.

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Picosecond kinetics of the electron‐hole layers formation in wide‐bandgap II‐VI type‐II heterostructures
Authors: Filatov E.V. , Zaitsev S.V. , Tartakovskii I.I. , Maksimov A.A. , Yakovlev D.R. , Waag A.
Published: March 2010

Considerable slowdown of luminescence kinetics of the direct optical transition was discovered in ZnSe/BeTe type‐II heterostructures under high levels of optical pumping. The effect is attributed to forming of a potential barrier for holes in the ZnSe layer due to band bending at high densities of spatially separated carriers. That results in a longer time of the photoexcited holes energy relaxation to their ground state in the BeTe layer.

The decrease of overlapping of electron and hole wavefunctions in the ZnSe layer in thick ZnSe/BeTe structures at high levels of optical excitation reveals an additional important effect, that leads to sufficient retardation of radiative recombination time for photoexcited carriers (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of elemental compositions by gas chromatography/time‐of‐flight mass spectrometry using chemical and electron ionization
Authors: Abate Salvatore , Ahn Yun Gyong , Kind Tobias , Cataldi Tommaso R. I. , Fiehn Oliver
Published: March 2010

Many metabolomic applications use gas chromatography/mass spectrometry (GC/MS) under standard 70 eV electron ionization (EI) parameters. However, the abundance of molecular ions is often extremely low, impeding the calculation of elemental compositions for the identification of unknown compounds. On changing the beam‐steering voltage of the ion source, the relative abundances of molecular ions at 70 eV EI were increased up to ten‐fold for alkanes, fatty acid methyl esters and trimethylsilylated metabolites, concomitant with 2‐fold absolute increases in ion intensities. We have compared the abundance, mass accuracy and isotope ratio accuracy of molecular species in EI with those in chemical ionization (CI) with methane as reagent gas under high‐mass tuning. Thirty‐three peaks of a diverse set of trimethylsilylated metabolites were analyzed in triplicate, resulting in 342 ion species ([M+H]+, [M–CH3]+ for CI and [M]+., [M–CH3]+. for EI). On average, CI yielded 8‐fold more intense molecular species than EI. Using internal recalibration, average mass errors of 1.8 ± 1.6 mm/z units and isotope ratio errors of 2.3 ± 2.0% (A+1/A ratio) and 1.7 ± 1.8% (A+2/A ratio) were obtained. When constraining lists of calculated elemental compositions by chemical and heuristic rules using the Seven Golden Rules algorithm and PubChem queries, the correct formula was retrieved as top hit in 60% of the cases and within the top‐3 hits in 80% of the cases. Copyright © 2010 John Wiley & Sons, Ltd.
Evaluation of tetracationic salts as gas‐phase ion‐pairing agents for the detection of trivalent anions in positive mode electrospray ionization mass spectrometry
Authors: Zhang Xiaotong , Wanigasekara Eranda , Breitbach Zachary S. , Dodbiba Edra , Armstrong Daniel W.
Published: March 2010

In previous studies, new electrospray ionization mass spectrometry (ESI‐MS) approaches were developed for the highly sensitive detection of singly and doubly charged anions in positive mode ESI‐MS by using specially synthesized dicationic and tricationic ion‐pairing agents, respectively. By detecting the positively charged ion complex in the positive mode, limits of detection (LODs) for the anions can be lowered by several magnitudes. In this work, we used eighteen newly synthesized tetracationic ion‐pairing agents, constructed with different geometries, linkages and cation moieties, for the detection of eighteen triply charged anions of different structural motifs. The LODs for these anions were from ten to several thousand times lower in the positive selective ion monitoring (SIM) mode than in the negative mode. These tetracationic agents also were shown to be useful for the detection of −1 and −2 anions. In addition, the LODs for −3 anions can be further lowered by monitoring the product fragments of the ion‐pairing complexes in the single reaction monitoring (SRM) mode. Copyright © 2010 John Wiley & Sons, Ltd.
In situ probing of cholesterol in astrocytes at the single‐cell level using laser desorption ionization mass spectrometric imaging with colloidal silver
Authors: Perdian D. C. , Cha Sangwon , Oh Jisun , Sakaguchi Donald S. , Yeung Edward S. , Lee Young Jin
Published: March 2010

Mass spectrometric imaging has been utilized to localize individual astrocytes and to obtain cholesterol populations at the single‐cell level in laser desorption ionization (LDI) with colloidal silver. The silver ion adduct of membrane‐bound cholesterol was monitored to detect individual cells. Good correlation between mass spectrometric and optical images at different cell densities indicates the ability to perform single‐cell studies of cholesterol abundance. The feasibility of quantification is confirmed by the agreement between the LDI‐MS ion signals and the results from a traditional enzymatic fluorometric assay. We propose that this approach could be an effective tool to study chemical populations at the cellular level. Published in 2010 by John Wiley & Sons, Ltd.
Release kinetics of actives from chewing gums into saliva monitored by direct analysis in real time mass spectrometry
Authors: Jeckelmann Nicolas , Haefliger Olivier P.
Published: March 2010

Direct analysis in real time mass spectrometry (DART‐MS) was used to monitor the release kinetics of a taste‐refreshing compound from chewing gums into the saliva of subjects. A new DART‐MS sample probe was designed which was about four times more sensitive than the current benchmark probe. This decreased the impact of the dilution of the saliva samples that was required to minimize ion suppression effects and make quantitative analyses without an internal standard possible. The new probe was also about three times more reproducible, which allowed quantitative measurements to be conducted manually without requiring the enhanced precision provided by an automatic sample positioner. The accuracy of analyses performed by DART‐MS was verified by comparing the results obtained from saliva samples analyzed both by DART‐MS and by a more classical liquid chromatography/mass spectrometry (LC/MS) method. This investigation showed good agreement between the two techniques. DART‐MS could then be used to objectively demonstrate the efficiency of a granular carbohydrate‐based delivery system to boost for a few minutes the release of a lipophilic flavor raw material with a high octanol/water partition coefficient, cyclohexanecarboxamide, N‐ethyl‐5‐methyl‐2‐(1‐methylethyl) (WS‐3), from chewing gum into saliva. Copyright © 2010 John Wiley & Sons, Ltd.
Elevation moment of inertia: A new feature for Monte Carlo localization in outdoor environment with elevation map
Authors: Kwon Tae‐Bum , Song Jae‐Bok , Joo Sang‐Hyun
Published: March 2010

The elevation map is one of the most popular maps for outdoor navigation. We propose the elevation moment of inertia (EMOI), which represents the distribution of elevation around a robot in an elevation map, for use in the matching of elevation maps. Using this feature, outdoor localization can be performed with an elevation map without external positioning systems. In this research, the Monte Carlo localization (MCL) method is used for outdoor localization, and the conventional method is based on range matching, which compares range sensor data with the range data predicted from an elevation map. Our proposed method is based on EMOI matching. The EMOI around a robot is compared with the EMOIs for all cells of the pregiven reference elevation map to find a robot pose with respect to the reference map. MCL based on EMOI matching is very fast, although its accuracy is slightly lower than that of conventional range matching. To deal with the disadvantage of EMOI matching, an adaptive switching scheme between EMOI matching and range matching was also proposed. Various outdoor experiments indicated that the proposed EMOI significantly reduced the convergence time of MCL. Therefore, the proposed feature is considered to be useful when an elevation map is used for outdoor localization. © 2010 Wiley Periodicals, Inc.
Atomic force microscopy study on chlorpromazine‐induced morphological changes of living HeLa cells In Vitro
Authors: Li Yongjun , Zhang Jing , Zhang Bailin
Published: March 2010

Chlorpromazine (CPZ)‐induced morphological changes of living human cervical carcinoma cells were investigated by atomic force microscopy in near physiological condition. The results showed that the cell morphology changed visibly with time in the presence of CPZ (>21 µM). The cell membrane shrank gradually and detached finally from the substrate. After being treated with CPZ for 50 min, the cell volume increased by about 27.6% while its projective area (cell adhered to the substrate) decreased by about 12%. The mechanism was also discussed. SCANNING 31: 259–265, 2009. © 2010 Wiley Periodicals, Inc.
The armchair at the borders: The “messy” ideas of borders and border epistemologies within multicultural science education scholarship
Authors: Carter Lyn
Published: March 2010

This paper aims to further articulate multicultural science education scholarship. In particular, it explores the notions of borders and border epistemologies as intellectual resources to think again about the challenges of science education in the global world that demand more sophisticated concepts to unravel some of its complexities. It responds in part to Osborne's (2007) call for more “armchair science education” to “develop better theories about our goals and values” (p. 11). Borders and border spaces reconceptualize and extend the view of borders typically presented within the literature as unproblematic lines between cultures and knowledges that need to be crossed. The constructs of border epistemologies introduce to science education the work of cultural theorists, Boaventura de Sousa Santos and Walter Mignolo. Collectively, their scholarship helps to theorize alternative epistemologies from the Global South that argue social and political justice must be premised within epistemological justice. I finish by problematizing some of these ideas for ongoing thinking around multicultural approaches to science education. © 2010 Wiley Periodicals, Inc.Sci Ed94:428–447, 2010