bluuebunny/crossref_metadata_2025 huggingface dataset:
An impedance‐based model for the evaluation of IM3 in nonlinear amplifiers showing memory effects
Authors: Madero‐Ayora María J. , Reina‐Tosina Javier , Crespo‐Cadenas Carlos
Published: January 2008

A simple model that captures nonlinear memory effects in wideband amplifiers is presented in this work. The model defines an equivalent hypothetical load impedance that explains asymmetries, in magnitude and phase, in two‐tone IM products, showing good correspondence with measurements. It helps to understand the intermodulation distortion dependence on modulation bandwidth. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 568–573, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23140
Fiber‐optic displacement sensor using a multimode bundle fiber
Authors: Yasin Moh. , Harun S. W. , Karyono Kusminarto , Ahmad H.
Published: January 2008

A simple fiber optic displacement sensor based on intensity modulation technique is demonstrated using a bundle multimode plastic fiber as a probe. The sensor consists of a light source, a probe, and photodiode detector. The sensor is capable of measuring displacements of mirror ranging from 0.05 to 2.2 mm using a red light source of wavelength 632.8 nm with maximum output power of 1 mW. The sensitivity of the device is found to be 168.8 mV/mm over 0.05–0.35 mm range and −29.8 mV/mm over 1.05–2.2 mm range. The sensor is highly sensitive at the front slope and very useful for close distance target. The simplicity of the design, high degree of sensitivity, dynamic range and the low cost of the fabrication make it suitable for applications in industries as position control and micro displacement measurement in the hazardous region. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 661–663, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23147
Effective permeability of inner ring shorted split ring resonator
Authors: Khan M. F. , Mughal M. J.
Published: January 2008

Analytical expression for effective permeability of inner ring shorted split ring resonator is derived in this paper. The resonant frequencies thus calculated are compared with published results and good agreement is observed for higher split lengths. Simulation results for effective permeability with different gap lengths in the split ring resonator are also included in this paper. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 624–627, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23149
LTCC stripline resonator using embedded air cavities for millimeter wave applications
Authors: Chul Lee Young , Soon Park Chul
Published: January 2008

A stripline T‐resonator is designed and implemented in the LTCC substrate for millimeter wave applications. The loss‐free air cavities are embedded at both side edges of the conducting strip in order to efficiently reduce the dielectric loss of the stripline structure. The resonator was implemented using 4‐layer LTCC dielectrics. The fabricated stripline resonator with air cavities reveals Q‐factor of 248 and total loss of 0.035 dB/mm at 34.7 GHz, and that is improved by 108% and 51%, respectively, compared to the conventional one. The proposed LTCC stripline resonator with the embedded air cavities can meet demands for low‐loss millimeter‐wave system‐on‐package (SoP) applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 658–661, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23151
Analysis of female human breast tissues at microwave frequencies
Authors: Bindu G. , Mathew K. T.
Published: January 2008

Complex permittivities of in vitro female human breast tissues have been measured at the ISM band using rectangular resonant cavity perturbation technique. Ranges of dielectric properties and water contents of these tissues are presented. The results show that benign and malignant breast tumors can be characterized based on the variation of the dielectric properties with respect to the dielectric parameters of the normal breast tissues. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 614–616, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23160
Using finite element method to calculate capacitance, inductance, characteristic impedance of open microstrip lines
Authors: Musa Sarhan M. , Sadiku Matthew N. O.
Published: January 2008

Microstrip transmission lines have received more interest and attention in microwave integrated circuit design. Analysis and electrical characterization of single and coupled microstrip lines have been a major focus for researchers in integrated circuit technology. In this article, we will illustrate modeling of the capacitance, inductance, and characteristic impedance of quasi‐TEM for open microstrip lines using finite element method with COMSOL multiphysics package. In this work, we determine the capacitance per unit length, inductance per unit length, and characteristic impedance of open microstrip lines (single‐strip, double strip, and three‐strip). We compare our results with those obtained by other methods and found them to be in agreement. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 611–614, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23164
Harmonics suppression of Wilkinson power divider using spurlines with adjustable rejection bands
Authors: Liu Hai‐Wen , Shi Zhiguo , Boutejdar Ahmed , Knoechel Reinhard H. , Schuenemann Klaus F.
Published: January 2008

A newly asymmetrical spurline structure is presented in this article. Its dual‐bandgap characteristics are reported and can be adjusted by changing the length difference between spurlines. Then, a simple circuit model is set up for the spurline structure by using two LCR‐resonators and the circuit parameters can be extracted from EM simulations. Moreover, a Wilkinson power divider using the proposed spurlines was designed, fabricated, and measured. Experimental results verify that 27‐dB suppression for the second harmonic and 30‐dB suppression for the third harmonic are obtained, respectively. In addition, the reflection coefficients are −3.5 dB ± 0.3 dB (−3 dB for ideal case) below 3.8 GHz and −3.7 dB at the operating frequency 3.12 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 601–604, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23172
Characterization and modeling of on‐wafer single and multiple vias for CMOS RFICS
Authors: Shi Xiaomeng , Seng Yeo Kiat , Anh Do Manh , Chye Boon Chirn
Published: January 2008

Characterization of on‐wafer vias using a 0.18‐μm RF CMOS technology is presented. Equivalent resistance and inductance of a single via and multiple vias with different physical arrangements are extracted from full wave simulations up to 30 GHz. An equivalent circuit model with frequency‐independent components is proposed to model the frequency‐dependent characteristics of the vias. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 713–715, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23173
A novel bandpass filter based on complementary split rings resonators and substrate integrated waveguide
Authors: Che Wenquan , Li Chao , Deng Kuan , Yang Lisheng
Published: January 2008

One novel bandpass filter implemented with combination of two different structures‐complementary split rings resonators (CSRRs) and substrate integrated waveguide (SIW) is proposed in this article. Several CSRRs are etched on the surface of SIW to form the stopband with very sharp rejection. One prototype was fabricated, the measured results indicate 30% passband (at −15 dB return loss), the rejection band ranges from 6.4 GHz to 7.8 GHz, about 20% bandwidth at −20 dB rejection, the maximum rejection even reaches 50 dB. The rejection skirt is very sharp, only 18 MHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 699–701, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23182
Design of spur‐line‐loaded cross‐coupled dual‐band bandpass filter with wide upper‐end stopband
Authors: Hsieh Yi‐Huan , Lee Ching‐Her , Hsu Chung‐I. G.
Published: January 2008

This article presents the design of a compact fourth‐order cross‐coupled dual‐band bandpass filter (BPF) having a wide upper‐end stopband. Quarter‐wavelength (λ/4) stepped‐impedance resonators (SIRs) were employed to construct the BPF to have a relatively small circuit size and high spurious harmonics, as compared with the BPF using half‐wavelength (λ/2) SIRs. The resonators tapped by the input and output feeding lines were loaded by a spur‐line to suppress the first spurious passband so as to further broaden the upper‐end stopband. BPFs with and without the embedded spur‐lines were both simulated to compare their frequency responses. Very good agreement between the simulated and measured results was observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 691–694, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23186
Gradient‐based optimization of packaged integrated microwave circuits exploiting reduced electromagnetic models
Authors: Assadihaghi Atousa , Bila Stéphane , Baillargeat Dominique , Aubourg Michel , Verdeyme Serge
Published: January 2008

A gradient‐based optimization method is presented for the design of packaged integrated microwave circuits. The method uses a reduced electromagnetic model resulting in a quasi‐instantaneous analysis of the packaged device. A gradient‐based strategy identifying parasitic effects due to circuit packaging is then deployed for optimizing the whole device. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 688–691, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23187
Wideband monopole antenna for DTV/GSM operation in the mobile phone
Authors: Lee Cheng‐Tse , Wong Kin‐Lu , Lin Yuan‐Chih
Published: January 2008

A wideband monopole antenna comprising a narrow radiating strip of length 120 mm and a simple internal matching portion for mobile phone application is presented. The monopole antenna can generate a wide operating band to cover the DTV reception in the UHF frequency band (470–862 MHz) and mobile communication in the GSM850/900 bands (824–894 MHz/890–960 MHz). The radiating strip is also promising to be retracted to be concealed inside the casing of the mobile phone when not in use. Details of the proposed antenna are described in the study. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 801–806, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23194
A low‐cost compact uniplanar Quasi–Yagi printed antenna
Authors: Ávila‐Navarro E. , Segarra‐Martínez A. , Carrasco J.A. , Reig C.
Published: January 2008

A low cost directive uniplanar broadband printed Quasi–Yagi antenna design is presented. As a particular realization, some prototypes have been designed to operate in the 2.45 GHz band. They have been then modeled, fabricated onto standard printed circuit dielectric substrate and tested successfully. For the design and the modeling processes, we have make use of FDTD based in‐house developed algorithms. The obtained bandwidth is, for all the considered cases, better than 15%. The main radiation characteristics are 2–5.5 dBi gain, depending on the number of director elements, and better than 25 dB front‐to‐back ratio. Overall antenna size was, in any case lesser than 1 λ × 0.5 λ. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 731–735, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23197
Linearity improvement of three‐way Doherty amplifier using power tracking bias supply method
Authors: Lee Yong‐Sub , Lee Mun‐Woo , Jeong Yoon‐Ha
Published: January 2008

This letter presents highly linear three‐way Doherty power amplifier (DPA) using power tracking bias supply method. The drain biases of carrier and peaking amplifiers and the gate biases of peaking amplifiers are adaptively controlled by the power tracking circuit according to average power levels of the input signal. For validation, a three‐way DPA is implemented using 30‐W Si LDMOSFETs and tested for two‐tone and 1‐carrier WCDMA signals at 2.14 GHz. The measured results show the notable linearity improvement over a wide output power range. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 728–731, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23198
Compact ultra‐wideband bandpass filter with improved out‐of‐band rejection
Authors: Mondal Priyanka , Kanti Mandal Mrinal , Chakrabarty Ajay
Published: January 2008

This letter presents a compact ultra‐wideband bandpass filter with improved out‐of‐band rejection performances. Complementary split ring resonators with microstrip feed lines are used to design the filter. Measurements show that maximum insertion loss within the ultra‐wide passband is below 2 dB. The 50‐dB stopband on the lower end is from DC to 2.48 GHz and the 25‐dB upper stopband is from 11.27 to 20 GHz. Out‐of‐band rejection performance of the filter satisfies and exceeds the U.S. Federal Communications Commission's indoor limit. Implementation area of the filter is 0.54 λg× 0.22 λg, λgis the guided wavelength of 50‐Ω microstrip line at 6.85 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 758–761, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23203
Multiwavelength YB‐doped fiber ring laser based on a Mach‐Zehnder interferometer
Authors: Tu Chenghou , Guo Wengang , Li Yongnan , Zhang Shuanggen , Zhu Hui , Lu Fuyun
Published: January 2008

We proposed and demonstrated a room‐temperature multiwavelength Yb‐doped fiber ring laser with high stability based on a Mach‐Zehnder interferometer by exploiting spatial hole burning and polarization hole burning effects, from which stable eight lasing wavelengths is obtained. The number of the lasing wavelengths (eight) is the most to our knowledge, and the wavelength spacing is 1.1 nm. Triple‐, and dual‐wavelength operation with the wavelength spacing of 1.1 nm or its integral multiples have been obtained by adjusting the intracavity polarization controllers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 723–725, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23206
Self‐Aligned Wafer‐Level Integration Technology with an embedded faraday cage for substrate crosstalk suppression
Authors: Sharifi H. , Mohammadi S.
Published: January 2008

A modification to a recently developed chip/wafer integration technology has proven to be very effective in suppressing the substrate crosstalk for mixed signal systems. In this implementation, analog and digital chips are fabricated on separate dies, and then integrated on a single Si substrate using a Self‐Aligned Wafer‐Level Integration Technology. A truly grounded faraday‐cage structure is realized by sidewall metallization around each die resulting in an ultimate substrate noise reduction. Any planar chip with any thickness can be used in this technology. Simulation and measurement results show that when a high‐resistivity silicon substrate as an integration medium is used along with grounded faraday cage, substrate coupling is suppressed to less than −60 dB for frequencies up to 25 GHz. For a low‐resistivity silicon substrate, the substrate coupling is a dominant mechanism in generating mixed‐signal noise, however, when sidewall metallization as faraday cage is utilized, the substrate coupling is reduced by at least 20 dB for frequencies below 25 GHz. The substrate noise suppression is higher than 35 dB for frequencies below 2 GHz. To our knowledge, these are the best values reported for isolation improvement of thick silicon substrates at microwave frequencies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 829–832, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23207
Innovative design of a planar fractal‐shaped GPS/GSM/Wi‐Fi antenna
Authors: Azaro R. , Zeni E. , Rocca P. , Massa A.
Published: January 2008

In this letter, the design of a microstrip three‐band antenna working in GPS, GSM, and Wi‐Fi frequency bands is described. By considering a planar geometry printed on a dielectric substrate, the tuning of the antenna behavior in three nonharmonic frequency bands is obtained perturbing the patch perimeter according to a Koch‐like fractal shape. The synthesis procedure is automatically performed by means of an iterative PSO‐based optimization strategy where a fractal boundary generator is integrated with a MoM‐based electromagnetic simulator. The feasibility of the approach as well as the reliability of the synthesized antenna is assessed through simulations as well as experimental results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 825–829, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23208
CPW‐FED shorted monopole antenna for broadband application
Authors: Liu Wen‐Chung , Yeh Feng‐Ming
Published: January 2008

By embedding two folded narrow slots into a rectangular patch, a shorted monopole fed by a coplanar waveguide (CPW) structure is obtained and can achieve broadband impedance matching for wireless application. Prototype of the obtained design has been constructed and experimentally studied. The measured results explore wide operation with −10 dB impedance bandwidth of 3.21 GHz, ranging from 4.29 to 7.5 GHz, and show good agreement with the numerical predictions. Also, good radiation pattern and high antenna gains over the operating band have also been observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 787–789, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23210
Infrared phased‐array antenna
Authors: Middlebrook Christopher T. , Krenz Peter M. , Lail Brian A. , Glenn D. Boreman
Published: January 2008

Phased addition of currents from multiple dipole antennas is demonstrated for the first time at a wavelength of 10.6 μm. Coplanar strip lines are used to interconnect the antennas, preserving the phase of the individual infrared‐frequency currents, which are summed together at a common bolometric load. Angular pattern measurements on two‐element dipole arrays show that the direction of maximum response depends on the phase difference between the currents contributed from each antenna, evaluated at the bolometer location. As more antennas are added together in phase, beam narrowing is observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 719–723, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23213
All‐optical generation of microwave using a photonic crystal fiber Brillouin laser based on Bragg grating Fabry‐Perot cavity
Authors: Geng Dan , Yang Dongxiao , Zhang Xianmin , Dong Qiujun , Wang Liang , Shao Xiaojie
Published: January 2008

A novel all‐optical technique for microwave generation using photonic crystal fiber Brillouin laser is presented, and a 9.78‐GHz microwave signal generator based on the Brillouin laser is experimentally realized. The Brillouin laser is based on a fiber Fabry‐Perot cavity with fiber Bragg gratings as reflectors along with 25‐m photonic crystal fiber as Brillouin gain medium. The fiber Bragg gratings are chosen to realize low laser threshold and suppress the higher‐order Stokes waves. Predictions of numerical simulations are compared with experimental results and both are in good agreement with each other. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 809–814, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23221
Greedy search and a hybrid local optimization/genetic algorithm for tree‐based inverse scattering
Authors: Wildman Raymond A. , Weile Daniel S.
Published: January 2008

A genetic programming‐based geometry optimization method for inverse scattering that uses a tree data structure to encode Boolean combinations of convex shapes has recently been shown to outperform other genetic algorithm‐based techniques. Nonetheless, the genetic algorithms are still inefficient for inverse scattering. This letter treats the inefficiency with local search techniques. First, an implementation using greedy search is discussed. Next, a local search method is added to the genetic algorithm used in the previous approach. Numerical results show that the number of function evaluations necessary to image conducting cylinders can be reduced by several orders of magnitude. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 822–825, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23222
New inequalities for finite and infinite group problems from approximate lifting
Authors: Miller Lisa A. , Li Yanjun , Richard Jean‐Philippe P.
Published: January 2008

In this paper, we derive new families of facet‐defining inequalities for the finite group problem and extreme inequalities for the infinite group problem using approximate lifting. The new valid inequalities for the finite group problem include two‐ and three‐slope facet‐defining inequalities as well as the first family of four‐slope facet‐defining inequalities. The new valid inequalities for the infinite group problem include families of two‐ and three‐slope extreme inequalities. These new inequalities not only illustrate the diversity of strong inequalities for the finite and infinite group problems, but also provide a large variety of new cutting planes for solving integer and mixed‐integer programming problems. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008
A summary of epiphyseal union timings in Bosnian males
Authors: Schaefer M. C.
Published: January 2008

Dry bone documentation of epiphyseal union times is scarcely represented within the literature due to the difficulties in obtaining large sample sizes of known‐age, juvenile osseous material. The identified missing from the recent conflicts in the former Yugoslavia has become a source for such a sample. This study investigates the union times of 26 epiphyses, in addition to union of the sternebrae, in 256 identified Bosnian males between the ages of 14 to 30 years. Progress of union was recorded by assigning each epiphysis to one of three phases denoting open, active or complete union. Age/phase distributions are provided for each of the epiphyses, as well as a summary table documenting overall age parameters. The results of this analysis not only increase the discipline's overall understanding of the timings of developmental changes, but will also assist in the process of age estimations, specifically within the Balkans. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis and characterization of conjugated polymers containing a carbazole moiety
Authors: Liu Yingliang , Xu Shengang , Li Jianghui , Xin Yuanrong , Zhao Guoxin , Ye Baoxian , Cao Shaokui
Published: January 2008

Two series of conjugated polymers with a carbazole moiety were synthesized by Knovenagel and Wittig condensations. The chemical structure, thermogravimetric, photophysical and electrochemical properties of the polymers were characterized by 1H‐NMR, IR, GPC, TG, UV‐vis, FL, and CV. The results indicated that PBM is the most thermally stable one and PBP is the most thermally instable one. The absorption and emission properties of the polymers were adjusted by the modification of chemical structures. The quenching effect of cyano group and oxygen atom results in the lower fluorescence quantum efficiency. The fitted emission spectra suggested that the emission spectra of all the polymers come from different vibronic transitions and aggregation emission. Copyright © 2008 John Wiley & Sons, Ltd.
Differential gene expression signature between primary and metastatic head and neck squamous cell carcinoma
Authors: Liu C‐J , Liu T‐Y , Kuo L‐T , Cheng H‐W , Chu T‐H , Chang K‐W , Lin S‐C
Published: January 2008

Head and neck squamous cell carcinoma (HNSCC) is a world‐wide malignancy. This study aimed to identify differential gene expression associated with the progression of disease from primary to metastatic HNSCC. Microdissection retrieved pure epithelial cells from paired primary tumours and cervical lymph node metastasis. cDNA microarray analysis and algorithm grouping identified differential mRNA expression of 301 genes. Quantitative reverse transcription‐polymerase chain reaction analysis clarified the up‐regulation of CCL19, CR2, EGR2, FUCA1, RGS1, and SELL, as well as the down‐regulation of IGFBP6 and KLK8 in nodal metastasis compared to primary tumours. Immunohistochemistry confirmed the up‐regulation of SELL and down‐regulation of IGFBP6 in nodal metastasis relative to primary tumours. Interestingly, primary tumours exhibiting higher FUCA1 and SELL expression were associated with significantly worse patient survival. In OECM‐1 HNSCC cells, inhibition of proliferation, migration, and anchorage‐independent growth was noted following knockdown of SELL expression. In SAS HNSCC cells, expression of exogenous SELL resulted in increased invasion, anchorage‐independent growth, and xenographic tumourigenesis in nude mice. Knockdown of FUCA1 and treatment with IGFBP6 inhibited the migration of OECM‐1 cells. Knockdown of RGS1 inhibited the anchorage‐independent growth of SAS cells. Our results provide a useful gene signature profile describing the factors underlying the metastasis of HNSCC to cervical lymph nodes, which may be beneficial for the treatment of HNSCC metastasis. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Influence of DMF on the polymerization of tert‐butyl acrylate initiated by 4‐oxo‐TEMPO‐capped polystyrene macroinitiator
Authors: Kuo Kuo‐Huai , Chiu Wen‐Yen , Cheng Kuo‐Chung
Published: January 2008

BACKGROUND: In a number of studies it has been shown that 2,2,6,6‐tetramethylpiperidinooxy (TEMPO)‐mediated polymerization of acrylates is not facile. Therefore, the object of the study reported here was to prepare poly[styrene‐block‐(tert‐butyl acrylate)] (PS‐b‐PtBA) block copolymers using 4‐oxo‐TEMPO‐capped polystyrene macroinitiator as an initiator, in the presence of small amounts of N,N‐dimethylformamide (DMF). The kinetic analysis and the effect of DMF on the reaction mechanism are also discussed.

RESULTS: PS‐b‐PtBA block copolymer was prepared through polymerization of tert‐butyl acrylate (tBA) initiated by 4‐oxo‐TEMPO‐capped polystyrene macroinitiator at 135 °C. The polymerization rate of tBA could be increased by adding a small amount of DMF, and the number average molecular weight of the PtBA block in PS‐b‐PtBA reached 10 000 g mol−1 with narrow polydispersity. The activation rate constant kact−tBA of alkoxyamine increased and the recombination rate constant krec−tBA decreased with increasing DMF concentration.

CONCLUSION: DMF was shown to be a rate‐enhancing additive for the polymerization of tBA using a 4‐oxo‐TEMPO‐capped polystyrene macroinitiator. From the kinetic analysis, it was concluded that the improvement of polymerization with the addition of DMF was due to an increase in kact−tBA and a decrease in krec−tBA. Copyright © 2008 Society of Chemical Industry
Finding consensus on the physiotherapy management of asymptomatic infants with cystic fibrosis
Authors: Prasad S.A. , Main E. , Dodd M.E.
Published: January 2008

Background

Babies with cystic fibrosis diagnosed by neonatal screening often display no overt signs of respiratory disease. The role of traditional routine daily chest physiotherapy in this particular group of babies is unclear and has generated considerable international debate. There is currently no evidence addressing this issue and present circumstances preclude a rigorous trial in the UK. This study aimed to provide expert consensus regarding the physiotherapy management of asymptomatic infants with CF.

Method

A Delphi consensus method was used to gather and refine expert opinions of senior paediatric physiotherapists in the UK. Agreement was sought on 16 statements reflecting aspects of physiotherapy management in ‘asymptomatic’ babies with cystic fibrosis.

Results

Twenty‐five senior paediatric physiotherapists from Specialist CF Centres throughout the UK participated in the study. Consensus was high amongst the respondents for 15 of the 16 statements. One statement failed to reach consensus. This related to the question of not routinely initiating a daily chest physiotherapy regimen in apparently healthy babies. Due to the lack of consensus an amendment to this statement was made, to allow a more flexible approach, where physiotherapists would not be obliged to initiate routine daily treatment in asymptomatic babies with CF, if they felt other another approach was justified.

Conclusion

There was high consensus of opinion amongst senior physiotherapists in the UK on most aspects of the physiotherapy management of babies with CF. Consensus could not be achieved on whether routine daily chest physiotherapy is necessary in ‘asymptomatic’ babies. An agreed amendment to the original statement allows professionals to modify or change traditional practice with the sanction of their senior colleagues. The results of this process will be used by the Association of Chartered Physiotherapists in Cystic Fibrosis to form the basis of national clinical guidelines. Pediatr Pulmonol. 2008; 43:236–244. © 2008 Wiley‐Liss, Inc.
A covalent S‐F heterodimer of leucotoxin reveals molecular plasticity of β‐barrel pore‐forming toxins
Authors: Roblin Pierre , Guillet Valérie , Joubert Olivier , Keller Daniel , Erard Monique , Maveyraud Laurent , Prévost Gilles , Mourey Lionel
Published: January 2008

Staphylococcal leucotoxins, leucocidins, and γ‐hemolysins are bicomponent β‐barrel pore‐forming toxins (β‐PFTs). Their production is associated with several clinical diseases. They have cytotoxic activity due to the synergistic action of a class S component and a class F component, which are secreted as water‐soluble monomers and form hetero‐oligomeric transmembrane pores, causing the lysis of susceptible cells. Structural information is currently available for the monomeric S and F proteins and the homoheptamer formed by the related α‐hemolysin. These structures illustrate the start and end points in the mechanistic framework of β‐PFT assembly. Only limited structural data exist for the intermediate stages, including hetero‐oligomeric complexes of leucotoxins. We investigated the protein–protein interactions responsible for maintaining the final bipartite molecular architecture and describe here the high‐resolution crystal structure and low‐resolution solution structure of a site‐specific cross‐linked heterodimer of γ‐hemolysin (HlgA T28C–HlgB N156C), which were solved by X‐ray crystallography and small angle X‐ray scattering, respectively. These structures reveal a molecular plasticity of β‐PFTs, which may facilitate the transition from membrane‐bound monomers to heterodimers. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Folding and dimerization of the ionic peptide EAK 16‐IV
Authors: Yan Zhiqiang , Wang Jun , Wang Wei
Published: January 2008

Folding and dimerization of an ionic polyalanine‐based peptide chain (EAK16‐IV) are simulated with nonspecific interactions. It is found that there is a competition between two kinds of structural motifs under different strengths of electrostatic interactions. The dominance of hairpin‐like structures would be realized with a strong electrostatic interaction both thermodynamically and kinetically, showing the importance of the electrostatic interaction on the formation of hairpin‐like structures. Simulations on the dimerization with strong electrostatic interaction are also carried out. It is found that the concentration contributes essentially to the shape of the dimers. These studies demonstrate that the strong interactions and kinetic factors might be important for the ordered amyloid aggregates. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Protein structure modeling indicates hexahistidine‐tag interference with enzyme activity
Authors: Freydank Anna‐Carolin , Brandt Wolfgang , Dräger Birgit
Published: January 2008

Unusual kinetic characteristics of tropinone reductase, an enzyme in the family of short chain dehydrogenases, prompted to investigate a possible impact of the hexahistidine affinity tag on catalytic properties. Comparison of enzymes from Solanum dulcamara, Solanaceae, tagged at the N‐terminus or at the C‐terminus revealed that the C‐terminally tagged form was functionally impaired. Protein modeling indicated that the hexahistidine tag attached at the C‐terminus but not at the N‐terminus of the polypeptide can interfere with the active site by steric or electrostatic interactions. In consequence, protein modeling is suggested before enzyme expression with affinity tags to estimate possible interactions of affinity tags with the active center. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Structure‐based classification of 45 FK506‐binding proteins
Authors: Somarelli J. A. , Lee S. Y. , Skolnick J. , Herrera R. J.
Published: January 2008

The FK506‐binding proteins (FKBPs) are a unique group of chaperones found in a wide variety of organisms. They perform a number of cellular functions including protein folding, regulation of cytokines, transport of steroid receptor complexes, nucleic acid binding, histone assembly, and modulation of apoptosis. These functions are mediated by specific domains that adopt distinct tertiary conformations. Using the Threading/ASSEmbly/Refinement (TASSER) approach, tertiary structures were predicted for a total of 45 FKBPs in 23 species. These models were compared with previously characterized FKBP solution structures and the predicted structures were employed to identify groups of homologous proteins. The resulting classification may be utilized to infer functional roles of newly discovered FKBPs. The three‐dimensional conformations revealed that this family may have undergone several modifications throughout evolution, including loss of N‐ and C‐terminal regions, duplication of FKBP domains as well as insertions of entire functional motifs. Docking simulations suggest that additional sequence segments outside FKBP domains may modulate the binding affinity of FKBPs to immunosuppressive drugs. The docking models also indicate the presence of a helix‐loop‐helix (HLH) region within a subset of FKBPs, which may be responsible for the interaction between this group of proteins and nucleic acids. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Evolutionary conserved N‐terminal region of human muscle fructose 1,6‐bisphosphatase regulates its activity and the interaction with aldolase
Authors: Gizak Agnieszka , Maciaszczyk Ewa , Dzugaj Andrzej , Eschrich Klaus , Rakus Darek
Published: January 2008

N‐terminal residues of muscle fructose 1,6‐bisphosphatase (FBPase) are highly conserved among vertebrates. In this article, we present evidence that the conservation is responsible for the unique properties of the muscle FBPase isozyme: high sensitivity to AMP and Ca2+ inhibition and the high affinity to muscle aldolase, which is a factor desensitizing muscle FBPase toward AMP and Ca2+. The first N‐terminal residue affecting the affinity of muscle FBPase to aldolase is arginine 3. On the other hand, the first residue significantly influencing the kinetics of muscle FBPase is proline 5. Truncation from 5–7 N‐terminal residues of the enzyme not only decreases its affinity to aldolase but also reduces its k‐cat and activation by Mg2+, and desensitizes FBPase to inhibition by AMP and calcium ions. Deletion of the first 10 amino acids of muscle FBPase abolishes cooperativity of Mg2+ activation and results in biphasic inhibition of the enzyme by AMP. Moreover, this truncation lowers affinity of muscle FBPase to aldolase about 14 times, making it resemble the liver isozyme. We suggest that the existence of highly AMP‐sensitive muscle‐like FBPase, activity of which is regulated by metabolite‐dependent interaction with aldolase enables the precise regulation of muscle energy expenditures and might contributed to the evolutionary success of vertebrates. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Spontaneous asparaginyl deamidation of canine milk lysozyme under mild conditions
Authors: Nonaka Yasuhiro , Aizawa Tomoyasu , Akieda Daisuke , Yasui Masanori , Watanabe Masahiro , Watanabe Nobuhisa , Tanaka Isao , Kamiya Masakatsu , Mizuguchi Mineyuki , Demura Makoto , Kawano Keiichi
Published: January 2008

Asparaginyl deamidation is a common form of nonenzymatic degradation of proteins and peptides. As it introduces a negative charge spontaneously and irreversibly, charge heterogeneity can be accumulated in protein solution during purification, preservation, and experiments. In this study, canine milk lysozyme (CML), a useful model for the study of the molten globule state, exhibited charge heterogeneity after sample purification. Four Asn residues in CML deamidated rapidly under mild conditions: pH 8.0 and 30°C. Other than these residues, one Asn residue, which was stable in the native state, was labile to deamidation in the unfolded state. This suggests that the structural formation around Asn can suppress deamidation. Substitutions of these labile Asn residues to Gln residues prevented deamidation effectively. Because the substitutions did not disrupt the structural formation of the native and molten globule states, they will enable more precise analyses for physical and structural studies. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Probing electric fields in proteins in solution by NMR spectroscopy
Authors: Hass Mathias A. S. , Ringkjøbing Jensen Malene , Led Jens J.
Published: January 2008

Electric fields generated in native proteins affect almost every aspect of protein function. We present a method that probes changes in the electric field at specific locations within a protein. The method utilizes the dependence of the amide 1H and 15N NMR chemical shifts on electric charges in proteins. Charges were introduced at different positions in the blue copper protein plastocyanin, by protonation of side chains or by substitution of the metal ion. It is found that the associated chemical shift perturbations (CSPs) stem mainly from long‐range electric field effects caused by the change in the electric charge. It is demonstrated that the CSPs can be used to estimate the dielectric constant at different locations in the protein, estimate the nuclear shielding polarizability, or position charges in proteins. Proteins 2008. © 2008 Wiley‐Liss, Inc.
The size of the intermolecular energy funnel in protein–protein interactions
Authors: Hunjan Jagtar , Tovchigrechko Andrey , Gao Ying , Vakser Ilya A.
Published: January 2008

Revealing the fundamental principles of protein interactions is essential for the basic knowledge of molecular processes and designing better predictive tools. Protein docking procedures allow systematic sampling of intermolecular energy landscapes, revealing the distribution of energy basins and their characteristics. A systematic search docking procedure GRAMM‐X was applied to a comprehensive nonredundant database of nonobligate protein–protein complexes to determine the size of the intermolecular energy funnel. The unbound structures were simulated using rotamer library. The procedure generated grid‐based matches, based on a smoothed Lennard‐Jones potential, and minimized them off the grid with the same potential. The minimization generated a distribution of distances, based on a variety of metrics, between the grid‐based and the minimized matches. The metric selected for the analysis, ligand interface RMSD, provided three independent estimates of the funnel size: based on the distribution amplitude for the near‐native matches, deviation from random, and correlation with the energy values. The three methods converge to similar estimates of ∼6–8 Å ligand interface RMSD. The results indicated dependence of the funnel size on the type of the complex (smaller for antigen–antibody, medium for enzyme–inhibitor, and larger for the rest of the complexes) and the funnel size correlation with the size of the interface. Guidelines for the optimal sampling of docking coordinates, based on the funnel size estimates, were explored. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Solution structure of At3g28950 from Arabidopsis thaliana
Authors: de la Cruz Norberto B. , Peterson Francis C. , Volkman Brian F.
Published: January 2008

We determined the solution structure of At3g28950 from A. thaliana, a homolog of At5g39720, whose structure we solved earlier. The secondary structure of the 165‐aa protein consists of a 5‐strand antiparallel β‐barrel domain flanked by two α‐helices and a 2‐strand β‐sheet; an additional free C‐terminal α‐helix extends into solution. Bioinformatic searches and analyses suggest that members of this growing set of structurally related proteins have been recruited to serve a wide variety of functions ranging from γ‐glutamyl cyclotransferase activity to participation in plant responses to chemical and biotic stimuli. Expression of a human homolog is elevated in bladder cancer tissues. Expression patterns for At3g28950 and its Arabidopsis paralogs suggest that each one evolved a different physiological role. The At3g28950 structure was solved as part of a structural genomics effort, and the results demonstrate how such a project can further understanding of genome evolution in addition to sequence–structure and structure–function relationships. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Protein domain annotation with integration of heterogeneous information sources
Authors: Zhao Xing‐Ming , Wang Yong , Chen Luonan , Aihara Kazuyuki
Published: January 2008

Domains are structural and functional units of proteins and play an important role in functional genomics. Theoretically, the functions of a protein can be directly inferred if the biological functions of its component domains are determined. Despite the important role that domains play, only a small number of domains have been annotated so far, and few works have been performed to predict the functions of domains. Hence, it is necessary to develop automatic methods for predicting domain functions based on various available data.

In this article, two new methods, that is, the threshold‐based classification method and the support vector machines method, are proposed for protein domain function prediction by integrating heterogeneous information sources, including protein–domain mapping features, domain–domain interactions, and domain coexisting features. We show that the integration of heterogeneous information sources improves not only prediction accuracy but also annotation reliability when compared with the methods using only individual information sources. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Phosphorescence of orthopaedic– grade ultra high molecular weight polyethylene
Authors: Chithambo M. L.
Published: February 2008

Isothermal luminescence decay curves have been measured from orthopaedic–standard ultra high molecular weight polyethylene between 35 and 70 °C on the rising edge of the main glow peak at 70 °C. Preparatory peak‐shape analysis of the temperature‐resolved glow peak at 70 °C measured at 1 °C s−1 gave a geometrical factor close to 0.5 suggestive of second order kinetics for both the isothermal and thermally stimulated luminescence. The results of analysis of the phosphorescence of transformed monotonic‐to‐peak isothermal decay curves are also second order, as is the conclusion from thermoluminescence glow‐curve de‐convolution. All methods of analysis give an activation energy of about 0.7 eV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metal insulator transition in n‐BGaInAs
Authors: Teubert J. , Klar P. J. , Heimbrodt W.
Published: February 2008

Isovalent boron is expected to form highly localized states within the conduction band of the GaInAs host which according to most present experimental findings only weakly influences the structure of the extended host states. Here we present magnetotransport (MR) measurements on three n‐type BGaInAs samples doped with silicon which vary in free carrier concentration n from 4.0 × 1016 cm−3 to 7.2 × 1017 cm−3. The three samples differ strongly in their resistivity behaviour. Whereas the sample with the highest n shows metallic behaviour, the transport behaviour of the sample with the lowest n is dominated by hopping transport. The latter is manifested by an exponential increase of the resistivity in the magnetic field. The experimental results are interpreted as a metal insulator transition (MIT). The MIT is found at unexpectedly high carrier concentration compared to GaAs which is attributed to increased alloy disorder in the quarternary alloy mainly due to the localized boron states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: phys. stat. sol. (c) 5/2
Authors: Leitch Andrew
Published: January 2008

The Conference on Photonic Materials held at Kariega Game Reserve from 2–6 May 2007, has been a successor to the successful Conference on Photo‐responsive Materials held at the same venue in 2004. Located in pristine surroundings, the tranquillity and splendour of the reserve, a Big 5 game lodge, in the Eastern Cape Province of South Africa, is beyond doubt awesome, making it a unique venue for this conference. The conference has since grown from 60 delegates representing 12 countries to more than 80 delegates from just over 20 countries, exceeding all expectations both from a representation and an academic standard point of view.

The purpose of this meeting was to bring together scientists working on various aspects of photonic materials, to share their latest research results and ideas and to foster links, consequently stimulating this all important field of solid state physics in South Africa and indeed the rest of the world.

The academic programme allowed sufficient time for interaction and exchanging of views and covered a wide range of important current topics in the field. The growth and characterization of narrow gap semiconductors for light emitting applications received considerable attention, as did ZnO and GaN and a range of nano materials. An interesting contribution in the photovoltaic section suggested that printed nano particle Si composites may have a role to play in the silicon photovoltaic market. On the social front, delegates were entertained by game drives and boat cruises up the Kariega river to view the majestic fish eagle. Dinner was served around a barn fire in an African Boma, with traditional African dancers entertaining delegates while they enjoyed traditional meals.

The academic programme committee members were: Reinhardt Botha and Andrew Leitch (Nelson Mandela Metropolitan University), Margit Härting (University of Cape Town), Jackie Nel (University of Pretoria) and Hendrik Swart (University of the Free State).

All papers appearing in these proceedings underwent a strict reviewing process separate from the conference. We express our appreciation to the referees for there diligence in this important task.

The conference was organized by the Department of Physics of the Nelson Mandela Metropolitan University (formerly known as the University of Port Elizabeth) under the auspices of the Condensed Matter Physics and Material Science (CMPMS) subgroup of the South African Institute of Physics. It was sponsored by EMF Limited (UK), the African Laser Centre (ALC), DETEK, the Council for Scientific and Industrial Research (CSIR), John Wiley & Sons, Inc. and Cambridge Chemical.