bluuebunny/crossref_metadata_2025 huggingface dataset:
An ultra‐wide bandpass filter with good out‐of‐band performance
Authors: Li Zhong , Wang Guang‐Ming , Zhang Chen‐Xin , Long Ge‐Nong
Published: April 2008

An ultra‐wideband microstrip filter with good out‐of‐band performance is designed and demonstrated. The filter design is based on a circuit model for an optimum short‐circuited stub transmission‐line filter whose unit elements or connecting lines are nonredundant. Substituting the connecting lines by the lowpass filter using stepped impedance hairpin resonator, the undesired spurious bands can be efficiently suppressed, and the designed filter length is reduced. According to the different requirements, the broadband bandpass and lowpass filter can be independently designed and modified, which makes the filter more convenient and easily implemented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1735–1737, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23517
Improving the solution accuracy of thin dielectric approximation with a vertical electric field component
Authors: Lu Cai‐Cheng
Published: April 2008

The traditional thin dielectric sheet approximation (TDS) method models the electromagnetic scattering by thin dielectric sheet using surface integral equation. In this approximation, only the tangential current within the dielectric sheet is considered, and the vertical component is ignored. This article proposes a method that uses the volume integral equation solution to predict the vertical volume current and hence to improve the overall solution accuracy. The formulation is based on the hybrid surface (SIE) and volume integration equation (VIE) in which, the thin dielectric is modeled with SIE, and the thin layers are modeled by VIE. It is shown that the inclusion of the vertical current component does not increase memory and solution time. Numerical examples will be provided to demonstrate the effectiveness of this approach. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1978–1982, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23518
Design of a miniaturized planar antenna for FCC‐UWB communication systems
Authors: Lizzi L. , Viani F. , Azaro R. , Massa A.
Published: April 2008

In this letter, the design of a planar antenna compliant with FCC requirements for ultra‐wideband (UWB) transmission systems is described. With reference to a planar geometry on a dielectric substrate, the shape of the antenna is described by means of a spline‐based representation and it is determined by means of an optimization process aimed at finding the optimal descriptive parameters that allow to fit the user‐defined electrical and dimensional requirements. The reliability and effectiveness of the antenna prototype are assessed through simulations as well as experimental measurements. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1975–1978, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23519
Propagation characteristics of periodic guided wave structures with a compact finite‐difference frequency‐domain method
Authors: Wang Xiao‐Hua , Wang Bing‐Zhong
Published: April 2008

To simulate periodic structures efficiently, Floquet's theorem is applied to a compact finite‐difference method for the analysis of dispersion characteristics of general periodic guided wave structures. By solving the full‐field‐component Eigen equations, dispersion characteristics and modes are obtained. The proposed method shows good applicability to the periodic guided structures where complex mode pairs, radiation modes, or leaky modes, etc., may exist. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1941–1944, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23520
Wideband circular slot antenna with tri‐band rejection characteristics at 2.45/5.45/8 GHz
Authors: Yeo Junho
Published: April 2008

A novel wideband circular slot antenna with tri‐band rejection characteristics at 2.45, 5.45, and 8 GHZ is proposed. Two different types of slots are used to obtain band‐notched characteristics at three frequencies; one is a split ring and the other is an inverted L‐shaped slot. These slots are employed inside a circular patch of the circular slot antenna and the rejection bands can be adjusted by selecting the lengths of two slots. It is demonstrated that tri‐band rejection characteristics at 2.45, 5.45, and 8 GHz with desired bandwidths can be obtained by using two different types of slots. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1910–1914, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23521
A star patch antenna for generating multiple radiation patterns
Authors: Mehta A. , Mirshekar‐Syahkal D. , Nakano H.
Published: April 2008

A novel form of star patch antenna for generating multiple radiation patterns, namely, tilted, axial and doughnut is presented and analyzed. These three patterns can be switched to scan all directions in front of the antenna. Each of these patterns can be generated by exciting one of the six feeding points on the antenna. By examining the current distributions corresponding to the radiation patterns of the antenna, qualitative reasoning's for the radiation mechanisms are also presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1908–1910, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23522
Low cost ultra wideband amplifier in 0.35 μm CMOS process
Authors: Modha Kuldip N. , Hayes‐Gill Barrie , Harrison Ian
Published: April 2008

A two stage ultra wideband (UWB) amplifier is presented. This amplifier incorporates multiple bandwidth enhancing techniques and is implemented in Austria micro systems (AMS) 0.35 μm CMOS process technology. The amplifier consumes 39.5 mW of power, exhibits a maximum gain of 13 dB, has input and output reflections below −9 and −10 dB, respectively over a −3 dB bandwidth of 4 GHz. The average measured noise figure is 6 dB and 1 dB compression point at 3 GHz is −12 dBm. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1879–1881, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23525
FDTD analysis of microstrip patch antenna on ferrite substrate
Authors: Alsunaidi M. A.
Published: April 2008

The finite‐difference time‐domain (FDTD) method is used to model the response of microstrip patch antennas on magnetized ferrite substrates. The proposed FDTD model utilizes the auxiliary differential equation approach to represent the frequency dependent permeability tensor in the time domain equations. The resulting 3D full‐wave numerical model is tested and verified against experimental data showing very good agreement. This model, being efficient, stable, and robust, is expected to assist in the design and characterization of wideband ferrite‐based antenna structures. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1848–1851, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23526
A modified scheme of sparse‐matrix canonical‐grid method using Chebyshev interpolating Green′s function
Authors: Huang S. W. , Xia M. Y.
Published: April 2008

A modified scheme of sparse‐matrix canonical‐grid (SMCG) method for simulation of rough surface scattering is developed. It employs an interpolating Green's function based on Chebyshev polynomial approximation to replace the Taylor series expansion in the previous SMCG methods, which becomes intractable for high‐order terms. This modified scheme is more efficient and flexible, and suitable for arbitrary roughness. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1844–1848, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23527
Controllable terahertz wave attenuator
Authors: Li Jiusheng , Yao Jianquan
Published: April 2008

A new type of optically controllable terahertz wave attenuator using high‐resistivity silicon wafer is developed and tested. Without optical excitation, the high‐resistivity silicon is a lossless dielectric material at terahertz wave region. When the high‐resistivity silicon wafer is optically excited, free carriers are generated, and the silicon wafer becomes a lossy dielectric. We study theoretically and demonstrate experimentally light‐controllable terahertz wave of the high‐resistivity silicon wafer. The results show that more than 10‐dB attenuation of the novel terahertz wave attenuator is obtained at frequency of 0.3 THz. The proposed device can be used in future terahertz wave communication systems. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1810–1812, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23528
Resonant microstrip meander line antenna element for wide scan angle active phased array antennas
Authors: Beenamole K. S. , Kutiyal Prem N. S. , Revankar U. K. , Pandharipande V. M.
Published: April 2008

A compact, wide bandwidth, wide beamwidth resonant microstrip meander line antenna element is reported for active phased array applications. The antenna element offers a return loss better than −10 dB over a bandwidth of 12% in S‐band with a beamwidth of 130° in E‐plane. The element has been tested in an array for its wide‐angle scan performance. Simulated and measured results are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1737–1740, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23531
A slot‐loaded slot antenna fed by inset CPW for dual frequency operation
Authors: Rhee Seungyeop
Published: April 2008

Broadband operation of a dual‐frequency rectangular slot antenna is achieved by embedding a pair of narrow slots in a rectangular patch inside a loop antenna with a CPW feed. With the proposed antenna design, the impedance bandwidths of 9.4% at the lower frequency band and 3.0% at the upper band are obtained. Details of the antenna design and experimental result are presented and discussed. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1984–1986, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23532
All fiber‐optic sensor for liquid level measurement
Authors: Nath Pabitra , Datta Pranayee , Ch Sarma Kanak
Published: April 2008

In this article, a simple intensity‐modulated fiber optic sensor for liquid level measurement is presented. The sensor principle is based on frustrated total internal reflection effect caused by refractive index change of a medium surrounding an optical fiber. The end face of a step‐index multimode optical fiber is polished to form a hemispherical tip so that a part of the forward propagating modes is reflected in the reverse direction by the effect of total internal reflection. The change of medium (due to contact of the tip with the liquid) modifies the critical angle for the back reflected light thus giving modulated output power. The experimental results of the sensor obtained for different liquids (pure water, ethanol) confirm the sensor potential for liquid level determination with high accuracy nearly 5 μm and repeatability. © Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1982–1984, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23533
Single mode operation of a Fabry–Perot laser locked by a tunable laser
Authors: Hua Zhu Ning , Han Wei , Li Wei , Chen Wei , Wen Ji Min , Liu Yu , Xie Liang
Published: April 2008

In this article, the single mode operation of a Fabry‐Perot laser (FP‐LD) subject to the optical injection from a tunable laser is investigated. The maximum side mode suppression ratio (SMSR) is 53 dB, and the locked wavelength range is about 46 nm, which can cover 58 International Telecommunication Union (ITU) wavelengths with 100 GHz spacing or 115 ITU wavelengths with 50 GHz spacing for wavelength division multiplexing (WDM) system. In the wavelength range from 1535 to 1569 nm, the SMSR is over 46 dB, and the frequency response of the injection‐locked FP‐LD can be improved with the proper wavelength detuning. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1888–1892, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23538
A microstrip patch antenna with broadened beamwidth
Authors: Ning Chen Zhi , Kian Toh Wee , Qing Xianming
Published: April 2008

A beamwidth broadening technique for a microstrip patch antenna is presented here. The antenna consists of a patch radiator with two phase‐reversed auxiliary radiators. This technique allows the beamwidth of a microstrip antenna with a large aspect ratio to be broadened at the expense of a slight increase in its lateral size. By using the auxiliary radiators, up to 16% increase in the H‐plane beamwidth is achieved. This antenna is also analyzed using a modified aperture model. Other existing beamwidth broadening techniques are compared and their applications listed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1885–1888, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23539
An alternative implementation of time domain adaptive integral method for surface integral equations
Authors: Xin‐Yi Ma , Dang‐Wei Wang , Yi Su , Jie Sheng
Published: April 2008

This letter presents an alternative implementation of the time domain adaptive integral method (TD‐AIM) for solving combined field integral equation (CFIE) pertinent to electromagnetic surface scattering phenomena. We use the cubic spline as temporal basis function and analytically remove the rot operator from the integrals of far‐zone interactions. Furthermore, we decompose the huge 4D FFT into several smaller ones in time domain. Consequently, the TD‐CFIE can be solved with relatively littler memory and computational resources accurately. Simulation results have been presented and demonstrated the effectiveness of the proposed implementation method. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1819–1822, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23542
Analysis of compact H‐shaped microstrip antenna
Authors: Ansari J. A. , Kesh Dubey Satya , Singh Prabhakar , Khan R. U. , Vishvakarma Babau R.
Published: April 2008

Analysis of H‐shaped patch is carried out using equivalent circuit model. It is found that the antenna exhibits dual resonance behavior which is very sensitive to the dimensions of the notch. The theoretical results of proposed method are compared with experimental and theoretical result reported earlier using FDTD method. Comparison with other reported results justify the veracity of the proposed method. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1779–1784, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23543
Compact ultrawideband square slot antenna with an asymmetric protruding stub
Authors: Shiu Jen‐Yi , Sze Jia‐Yi , Tu Po‐Jen
Published: April 2008

A new compact ultra‐wideband (UWB) square slot antenna fed by a coplanar waveguide (CPW) is proposed. A large impedance bandwidth of more than 13 GHz (2.8–16 GHz) was obtained by asymmetrically widening the tuning stub that is extended from the signal strip of the CPW into the square slot. The larger and smaller widened parts of the asymmetric tuning stub can be easily adjusted to achieve good impedance matching in the lower and upper regions, respectively, of the entire VSWR ≤ 2 band. The simple design procedure along with reasonably agreed measured and simulated results is presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1776–1779, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23544
A fully single‐ended GaInP/GaAs HBT micromixer using an integrated active LO balun
Authors: Wu Tzung‐Han , Lin Yi‐Chen , Meng Chinchun , Wu Tse‐Hung , Wei Hung‐Ju , Huang Guo‐Wei
Published: April 2008

A Gilbert micromixer is demonstrated in this paper using GaInP/GaAs HBT technology. By using an on‐chip active LO balun, the micromixer with the single‐ended RF, LO, and IF ports is suitable for hybrid RF system applications. The port‐to‐port isolation has its best performance when the LO signal is balanced. The fully matched high‐linearity micromixer has the conversion gain of 12 dB, IP1dB of −9 dBm, IIP3 of 1 dBm when fIF(input) = 300 MHz, fLO = 3.5 GHz, and fRF(output) = 3.8 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1918–1921, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23549
Scheduling parallel dedicated machines with the speeding‐up resource
Authors: Kellerer Hans , Strusevich Vitaly A.
Published: April 2008

We consider a problem of scheduling jobs on m parallel machines. The machines are dedicated, i.e., for each job the processing machine is known in advance. We mainly concentrate on the model in which at any time there is one unit of an additional resource. Any job may be assigned the resource and this reduces its processing time. A job that is given the resource uses it at each time of its processing. No two jobs are allowed to use the resource simultaneously. The objective is to minimize the makespan. We prove that the two‐machine problem is NP‐hard in the ordinary sense, describe a pseudopolynomial dynamic programming algorithm and convert it into an FPTAS. For the problem with an arbitrary number of machines we present an algorithm with a worst‐case ratio close to 3/2, and close to 3, if a job can be given several units of the resource. For the problem with a fixed number of machines we give a PTAS. Virtually all algorithms rely on a certain variant of the linear knapsack problem (maximization, minimization, multiple‐choice, bicriteria). © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008
PANI–LDPE composites: Effect of blending conditions
Authors: Cote M. , Cortés M.T. , Beltrán D. , Ortiz P.
Published: April 2008

A composite based on polyaniline (PANI) and low density polyethylene (LDPE) with electrical conductivity was developed. Polyaniline was polymerized by chemical oxidation and doped with dodecyl‐benzene‐sulfonic acid (DBSA). PANI–LDPE composites were prepared via melt blending and the films were obtained by compression molding. The influence of three variables of the blending (temperature, [PANI], rotor speed) on conductivity, microstructure and mechanical properties of the composites was studied by means of statistical tools and a 23 experimental design. The results show that the PANI concentration is the most influential variable, which mainly affects the conductivity and the elongation at break of the composites. These changes are related to the microstructure of the composites. Statistically, the other variables don't show significant influence on conductivity and mechanical properties in the studied range. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.
Copolymerization of aniline and styrene using various surfactants in aqueous media
Authors: Eisazadeh Hossein , Kavian Amin
Published: April 2008

Polyaniline/polystyrene (PAn/PS) copolymer was prepared in the aqueous solution by copolymerization of styrene and aniline using potassium iodate (KIO3) and ammonium persulfate ((NH4)2S2O8) as an oxidant in the presence of various surfactants such as poly(ethylene glycol), hydroxypropylcellulose, and surfactive dopant sodium dodecylbenzenesulfonate. The PAn/PS copolymer was characterized in terms of conductivity, morphology, chemical structure, and glass transition temperature. The results indicate that the morphology, conductivity, and glass transition temperature of products are dependent on the type of surfactant. Furthermore, it was found that addition of styrene monomer into stirred aqueous solution influences the surface morphology. The chemical structure and glass transition temperature of product were studied by Fourier transform infrared spectroscopy and differential scanning calorimetry respectively. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Effect of surface treatment on the tribological performance of carbon fiber reinforced thermoplastic polyimide composites
Authors: Li J. , Cheng X.H.
Published: April 2008

The effect of rare earth solution (RES) surface treatment of carbon fibers (CFs) on the tensile strength and tribological properties of CF‐reinforced polyimide (CF/PI) composite was investigated. Experimental results revealed that the tensile strength of RES‐treated CFs reinforced PI composite was improved by about 19% compared with that of untreated composite, while 7% improvement was achieved by air oxidation. Compared with the untreated and air‐oxidated CF/PI composite, the RES‐treated composite had the lowest friction coefficient and specific wear rate under given applied load and reciprocating sliding frequency. RES treatment effectively improved the interfacial adhesion between CFs and PI. The strong interfacial adhesion of the composite made CFs not easy to detach from the PI matrix and prevented the rubbing‐off of PI, and accordingly improved the friction and wear properties of the composite. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
The investigation of intumescent flame‐retardant polypropylene using a new macromolecular charring agent polyamide 11
Authors: Liu Yuan , Feng Zhiqiang , Wang Qi
Published: April 2008

This article deals with a new macromolecular charring agent, polyamide 11 (PA11), which is in combination with a small charring agent, pentaerythritol (PER) and a flame retardant, ammonium polyethylene to flame‐retardant polypropylene (PP). When compared with polyamide 6 (PA6), an existing macromolecular charring agent extensively reported, PA11 has longer alkyl segment in its chain unit and shows better compatibility with PP; additionally, with a relatively lower melt point close to that of PP, PA11 can be more effectively compounded with PP in the melt state and better dispersed in PP matrix, thus enhancing the flame retardancy and mechanical properties. Moreover, with certain synergistic effects between PA11 and PER, the system using PA11/PER as composite charring agents showed better charring performance in comparison with the system only using PER. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Preparation and characterization of functionalized carbon nanotubes/poly(phthalazinone ether sulfone ketone)s composites
Authors: Feng Xuebin , Liao Gongxiong , He Wei , Sun Qingmin , Jian Xigao , Du Jinhong
Published: April 2008

Multiwalled carbon nanotubes (MWNT) were successfully functionalized with phthalazinone‐containing diamine (DHPZDA) groups by the amidation reaction. The morphologies and structures of the DHPZDA‐functionalized MWNT (MWNT‐DHPZDA) were characterized by scanning electron microscope, Fourier transform infrared, and Raman spectroscopy, revealing that the DHPZDA were covalently attached onto the surface of MWNT, and the weight gain due to the functionalization was determined by thermogravimetric analysis. The MWNT‐DHPZDA/poly(phthalazinone ether sulfone ketone)s (PPESK) composites with different filler content were prepared by the solution‐mixing method. MWNT‐DHPZDA can be uniformly dispersed in the matrix and the strong interfacial adhesion between two constituents was found, which resulted in obvious enhancements of the mechanical properties. For the composite with 1 wt% MWNT‐DHPZDA, the tensile strength and the Young's modulus are 102.1 and 1,974 MPa, about 1.65 and 1.72 times of the pure PPESK, respectively. Conductivity measurements indicate that a typical percolation transition behavior takes place for MWNT‐DHPZDA content in the range from 0.5 to 2 wt%. Additionally, introducing MWNT‐DHPZDA into PPESK is favorable to improvement of the thermal stability. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Synthesis and properties of the amino‐functionalized multiple‐walled carbon nanotubes/polyimide nanocomposites
Authors: Hu Yizhe , Shen Jianfeng , Qin Chen , Wu Liping , Zhang Binbin , Ye Mingxin
Published: April 2008

The 1,6‐hexanediamine‐functionalized multi‐walled carbon nanotubes(a‐MWNTs)/polyimide(PI) nanocomposite films were prepared through in‐situ polymerization followed by mixture casting, evaporation, and thermal imidization. To increase the compatibility of carbon nanotubes with the matrix polyimide, a‐MWNTs was used as the filler. According to the results, a‐MWNTs were homogeneously dispersed in the nanocomposite films. With the incorporation of a‐MWNTs, the mechanical properties of the resultant films were improved due to the strong chemical bonding and interfacial interaction between a‐MWNTs and 4,4′‐oxydiphthalic anhydride(ODPA)/4,4′‐Oxydianiline(ODA) polyimide matrix. The thermal stability of the a‐MWNTs/polyimide nanocomposite was also improved by the addition of a‐MWNTs. The electrical tests showed a percolation threshold at about 0.85 vol% and the electrical properties were increased sharply. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Acute dyspnea in an adolescent girl after physical exertion: A case report and review of the literature
Authors: Yalçın Ebru , Arıyürek Macit
Published: April 2008

Dyspnea is a common symptom of cardiac and pulmonary diseases. We present a 15‐year‐old girl with acute dyspnea, chest pain, cough, and difficulty in swallowing whose initial diagnosis was psychogenic dyspnea. The etiology of acute dyspnea is discussed and reported cases are reviewed in this case report. Pediatr Pulmonol. 2008; 43:604–606. © 2008 Wiley‐Liss, Inc.
Nasal potential difference in non‐classic cystic fibrosis—long term follow up
Authors: Jaron Ranit , Yaakov Yasmin , Rivlin Joseph , Blau Hannah , Bentur Lea , Yahav Yakov , Kerem Eitan , Bibi Haim , Picard Elie , Wilschanski Michael
Published: April 2008

Background

Nasal potential difference (NPD) measurement is an electrophysiological test that assesses cystic fibrosis transmembrane conductance regulator (CFTR) activity and is a recognized diagnostic tool in CF. The aim of this study is to assess in the long term the role of NPD in patients whose diagnosis is questionable.

Methods

We performed follow up study on 70 patients with questionable CF (QCF) who were divided previously into two groups according to their NPD results: patients who likely have CF (QCF‐CF) (n = 24), and those who likely do not have CF (QCF‐non‐CF) (n = 46).

Results

Sixty out of 70 patients were available for study. Sixteen patients in the QCF‐CF group were being followed up at CF Centers as opposed to 1 in the QCF‐non‐CF group (P < 0.01). Seven patients from the QCF‐CF group developed sinusitis during the follow up years compared to none from the QCF‐non‐CF group. During the years of the follow up, 17 QCF‐non‐CF patients were diagnosed with other medical conditions that could explain their previous symptoms. On repeated NPD measurement in the QCF‐CF group, the results were similar to the original test.

Conclusions

This study supports the diagnostic role of NPD measurement. Larger cohort studies are required for confirmation. Pediatr Pulmonol. 2008; 43:545–549. © 2008 Wiley‐Liss, Inc.
Lattices for ab initio protein structure prediction
Authors: Pierri Ciro Leonardo , De Grassi Anna , Turi Antonio
Published: April 2008

In the study of the protein folding problem with ab initio methods, the protein backbone can be built on some periodic lattices. Any vertex of these lattices can be occupied by a “ball,” which can represent the mass center of an amino acid in a simplified coarse‐grained model of the protein. The backbone, at a coarse‐grained level, can be constituted of a No Reverse Self Avoiding Walk, which cannot intersect itself and cannot go back on itself. There is still much debate between those who use lattices to simplify the study of the protein folding problem and those preferring to work by using an off‐lattice approach. Lattices can help to identify the protein tertiary structure in a computational less‐expensive way, than off‐lattice approaches that have to consider a potentially infinite number of possible structures. However, the use of a lattice, constituted of insufficiently accurate direction vectors, constrains the predictive ability of the model. The aim of this study is to perform a systematic screening of 7 known classic and 11 newly proposed lattices in terms of predictive power. The crystal structures of 42 different proteins (14 mainly alpha helical, 14 mainly beta sheet and 14 mixed structure proteins) were compared to the most accurate simulated models for each lattice. This strategy defines a scale of fitness for all the analyzed lattices and demonstrates that an increase in the coordination number and in the degrees of freedom is necessary but not sufficient to reach the best result. Instead, the introduction of a good set of direction vectors, as developed and tested in this study, strongly increases the lattice performance. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Constructing templates for protein structure prediction by simulation of protein folding pathways
Authors: Kifer Ilona , Nussinov Ruth , Wolfson Haim J.
Published: April 2008

How a one‐dimensional protein sequence folds into a specific 3D structure remains a difficult challenge in structural biology. Many computational methods have been developed in an attempt to predict the tertiary structure of the protein; most of these employ approaches that are based on the accumulated knowledge of solved protein structures. Here we introduce a novel and fully automated approach for predicting the 3D structure of a protein that is based on the well accepted notion that protein folding is a hierarchical process. Our algorithm follows the hierarchical model by employing two stages: the first aims to find a match between the sequences of short independently‐folding structural entities and parts of the target sequence and assigns the respective structures. The second assembles these local structural parts into a complete 3D structure, allowing for long‐range interactions between them. We present the results of applying our method to a subset of the targets from CASP6 and CASP7. Our results indicate that for targets with a significant sequence similarity to known structures we are often able to provide predictions that are better than those achieved by two leading servers, and that the most significant improvements in comparison with these methods occur in regions of a gapped structural alignment between the native structure and the closest available structural template. We conclude that in addition to performing well for targets with known homologous structures, our method shows great promise for addressing the more general category of comparative modeling targets, which is our next goal. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Aldrin epoxidation and dihydroisodrin hydroxylation as probes of in vivo and in vitro oxidative metabolic capability of some caterpillars
Authors: Krieger Robert I
Published: April 2008

Comparative biochemical studies are productive means to study factors that limit both beneficial and harmful effects of chemicals. Reactions such as aldrin epoxidation and dihydroisodrin hydroxylation are valuable assays of oxidative metabolism in scientific studies of chemical biology in insects, subhuman primates and other living things. The tissue distribution of activity in caterpillars may have functional significance. Localization of relatively high concentrations of these cytochrome P450 monooxygenases in gut tissue of lepidoptera may represent an important means to minimize absorption of lipophilic foreign chemicals in food. Some polychlorocycloalkanes permit in vivo and in vitro studies owing to their stability, acceptable toxicity and relatively simple pattern of metabolism. In vivo studies to assess the significance of in vitro findings are feasible with substrates such as aldrin, dihydroisodrin (DHI) and oxidative methylenedioxyphenyl inhibitors such as piperonyl butoxide (PBO) or carbon monoxide. Biphasic dose‐dependent decreased and increased DHI‐OH formation resulted from PBO pretreatment by gut, fat body, head and Malpighian tubule homogenates of cutworms and gut and fat body (the only tissues tested) of cabbage looper Trichplusia ni (Hübner) and black cutworm Agrotis ipsilon (Hüfnagel). The biphasic in vivo responses of caterpillars to PBO are a reminder of the complexity of biochemical and physiological responses of organisms coexposed to chemicals that are classified, often glibly, as toxic substances and metabolic inhibitors and inducers. Knowledge of dose and time relationships demands very careful evaluation in living things in the environment. Copyright © 2008 Society of Chemical Industry
Simulation and design of InGaAsN metal‐semiconductor‐metal photodetectors for long wavelength optical communications
Authors: Tsai Shin‐Li , Wu Jenq‐Shinn , Lin Hung‐Ji , Lin Der‐Yuh , Zheng Jin‐Yao
Published: April 2008

Optical properties of InGaAsN/AlGaAs metal‐semi‐conductor‐metal photodetectors (MSM‐PDs) with a modulation‐doped heterostructure operating at the wavelength of 1.3 μm have been simulated by a two‐dimensional device simulator. Simulation results show that the optimized device structure has a 30‐nm‐thick cap layer with Nd = 2×1017 cm–3, a 10‐nm‐thick spacer layer, and 7‐μm‐wide finger spacing to exhibit the largest photocurrent response and shortest decay response time. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of surface preparation and i‐AlGaN thickness on electrical properties of i‐AlGaN/GaN heterostructures
Authors: Sawada T. , Takahashi K. , Imai K. , Suzuki K. , Kimura N. , Kitamori K.
Published: April 2008

The influence of surface preparation and wet‐etching of AlGaN layer on electrical properties of bare i‐AlGaN/GaN and Ni/i‐AlGaN/GaN Schottky samples has been investigated. Hall effect measurements of bare samples indicated that the surface oxide increases 2DEG density, while the thinner the AlGaN layer, the lower the 2DEG density is, accompanied with reduced electron mobility. Theoretical analysis indicated that the former is due to lowering of the surface barrier, while in the latter the 2DEG density changes according to theoretical curve with a constant surface barrier. For Schottky samples, both forward and reverse currents increased with reducing the AlGaN layer, giving smaller effective Schottky barrier height (SBH). The behavior can be well explained by combined leakage currents due to leaky patches and simple tunneling through the surface barrier. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance stability of AlGaN/GaN HFET: effect of plasma processing
Authors: Baksht Tamara , Knafo Yaron , Yehuda Ilanit , Bunin Gregory
Published: April 2008

Effect of fluoride‐based plasma treatment on performance stability of AlGaN/GaN HFET was systematically investigated. The plasma‐based processes can introduce different type of damage that can be permanent or temporary, depending on electrical field in the device, plasma density, and energy of radicals and total process thermal budget. In order to understand more clearly the mechanism of fluorine based plasma treatment on device performance, we compare the effects of Ar, O2 and CF4 based plasma treatments applied before gate definition. Ar plasma was chosen for comparison with CF4 because of high ionization rate of Ar and chemically neutral behavior of Ar ions. Under the same medium range of 40 V DC bias in RIE system for these two gases, the shift of drain current and threshold voltage was similar that indicate the common mechanism of plasma damage. We supposed that the major effect for this phenomenon is a negative electron charge inserted in semiconductor during plasma treatment, because at the same accelerated field the penetration depth for electrons is higher than the penetration depth for fluoride ions. Devices stressed under impact ionization conditions show an improvement of breakdown voltage (for O2 plasma treatment) and some recovery of threshold voltage similar to “walkout effect”. This performance non‐stability raise the serious concern about application of fluorine based technology for power applications, where large voltage/current swing may push device to the impact ionization region. The experimental results show that the implementation of fluoride based plasma treatment for power device manufacturing can affect the performance stability of AlGaN/GaN power HFET. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High power and high gain AlGaN/GaN MIS‐HEMTs with high‐k dielectric layer
Authors: Kanamura M. , Ohki T. , Imanishi K. , Makiyama K. , Okamoto N. , Kikkawa T. , Hara N. , Joshin K.
Published: April 2008

High power n‐GaN/n‐AlGaN/GaN metal‐insulator‐semi‐conductor high electron mobility transistors (MIS‐HEMTs) with high‐k Ta2O5 dielectric layer were fabricated on a 3‐inch S.I.‐SiC substrate, for the first time. An n‐GaN/n‐AlGaN/GaN MIS‐HEMTs with 400 V breakdown voltage were obtained by using Ta2O5 insulating layer/n‐GaN capstructure. The single‐chip GaN MIS‐HEMTs amplifier with a Ta2O5 layer operated at 50 V achieve a high output power of 113 W with a linear gain of 16.3 dB at 2.5 GHz. We also investigated the RF stress reliability under the P3dB condition. The fluctuation of output power and drain current was lower than 5% even after 150 h stress test. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cervical length and obstetric history predict spontaneous preterm birth: development and validation of a model to provide individualized risk assessment
Authors: Celik E. , To M. , Gajewska K. , Smith G. C. S. , Nicolaides K. H.
Published: April 2008

Objectives

To evaluate the ability of combinations of cervical length and maternal history to assess the risk of spontaneous preterm birth, and to provide a simple procedure for the optimal estimation of risk.

Methods

This prospective observational study was carried out between January 1998 and May 2006. Transvaginal sonographic measurement of cervical length at 20 + 0 to 24 + 6 weeks of gestation was carried out in 58 807 singleton pregnancies as part of routine antenatal care. The outcome measure was spontaneous extreme (< 28 weeks), early (28–30 weeks), moderate (31–33 weeks) and mild (34–36 weeks) preterm birth. Logistic regression analysis was used to derive models for the prediction of spontaneous preterm birth from the maternal obstetric history, demographic characteristics and cervical length.

Results

The rates of extreme, early, moderate and mild spontaneous preterm birth were 0.23%, 0.24%, 0.57% and 2.93%, respectively. The best prediction of spontaneous preterm birth was provided by cervical length (area under the receiver–operating characteristics curve (AUC), extreme 0.903, early 0.816, moderate 0.784 and mild 0.617) and this was improved by adding obstetric history (AUC, extreme 0.919, early 0.836, moderate 0.819 and mild 0.650). Addition of other parameters was without material effect. For a 10% screen‐positive rate, models using cervical length and obstetric history had a sensitivity of 80.6%, 58.5%, 53.0% and 28.6% for extreme, early, moderate and mild spontaneous preterm birth, respectively. These models were expressed as tables of adjusted likelihood ratios to allow simple estimation of the risk of spontaneous preterm birth.

Conclusions

A model combining cervical length and obstetric history provides a better prediction of spontaneous preterm birth than either factor alone, and the sensitivity of screening improves for increasing degrees of prematurity. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Studies on rheology and morphology of POE/PP thermoplastic elastomer dynamically crosslinked by peroxide
Authors: Yuan Bo , Chen Xian , He Bobing
Published: April 2008

An ethylene‐octene copolymer (POE)/polypropylene (PP) thermoplastic elastomer was prepared through dynamically crosslinking by 2,5‐dimethyl‐2,5‐dilbuty (Peroxy) hexane (DHBP). The effects of DHBP concentration, POE/PP ratio, melt flow index (MFI) of PP, and mixer rotation on rheology and morphology of the thermoplastic elastomer were studied. The results showed that with increasing DHBP concentration or POE content, the size of crosslinked particles as well as the melt viscosity increased. Furthermore, agglomerates or a network structure formed as the size of crosslinked particles increased. The melt viscosity also increased as MFI of PP decreased, while the size of crosslinked particles decreased under the same condition. Research on the morphology of dynamically crosslinked POE/PP thermoplastic elastomer flowing through a capillary rheometer at different shear rates show that the reprocessing had little effect on the morphology of dynamically crosslinked elastomer. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.
Influence of third component on mechanical properties and thermal stability of polypropylene/(regenerated polyurethane) blends
Authors: Zhang Shu Ling , Zhang Zhen Xiu , Kim Jin Kuk
Published: April 2008

The possibility of polypropylene (PP) modification by regenerated polyurethane (PU), obtained after partial thermochemical decomposition of waste PU, has been studied. The degradation product was a thermoplastic mixture, applicable for reuse without any purification and fractionation. It was proved that regenerated PU could be reused as an effective polymeric plasticizer for PP and that the addition of regenerated PU did not decrease the thermal stability of PP. In order to improve further the elongation at break of PP modified by regenerated PU, a third component was added to the PP/(regenerated PU) blend. The influence of the third component on the mechanical properties and thermal stability of the blends was evaluated by using a universal testing machine (UTM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The data showed that the elongations of PP/(regenerated PU) blends with styrene‐ethylene‐butylene‐styrene polymer (SEBS) were obviously better than those of the PP/(regenerated PU) blend without the third component and with PP‐g‐MA or SEBS‐g‐MA (MA = maleic anhydride). In addition, the thermal stability of PP/(regenerated PU) blends with a third component was almost same as that of the PP/(regenerated PU) blend without a third component. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.
Myasthenia gravis in a patient affected by glycogen storage disease type Ib: A further manifestation of an increased risk for autoimmune disorders?
Authors: Melis D. , Balivo F. , Della Casa R. , Romano A. , Taurisano R. , Capaldo B. , Riccardi G. , Monsurrò M. R. , Parenti G. , Andria G.
Published: April 2008

Glycogen storage disease type Ib (GSD Ib, OMIM 232220) is an inborn disorder of glucose metabolism, caused by mutations in the G6PT gene, encoding a glucose 6‐phosphate transporter (G6PT). GSD Ib is mainly associated with fasting hypoglycaemia and hepatomegaly. Most GSD Ib patients also show neutropenia and neutrophil dysfunction and therefore are at risk of developing severe infections and inflammatory bowel disease (IBD). An increased risk for autoimmune disorders, such as thyroid autoimmunity and Crohn‐like disease, has also been demonstrated, but no systematic study on the prevalence of autoimmune disorders in GSD Ib patients has ever been performed. We describe a 25‐year‐old patient affected by GSD Ib who developed ‘seronegative’ myasthenia gravis (MG), presenting with bilateral eyelid ptosis, diplopia, dysarthria, severe dysphagia, dyspnoea and fatigue. The repetitive stimulation of peripheral nerves test showed signs of exhaustion of neuromuscular transmission, particularly evident in the cranial area. Even in the absence of identifiable anti‐acetylcholine receptor antibodies, seronegative MG is considered an autoimmune disorder and may be related to the disturbed immune function observed in GSD Ib patients.
Fractal Dimensions of Simulated and Real Fat Crystal Networks in 3D Space
Authors: Tang Dongming , Marangoni Alejandro G.
Published: April 2008

The microstructure of fat crystal networks is closely related to rheological properties of fat products, and thus is of particular interest to food scientists. The fractal dimensions of fat crystal networks calculated by microscopy methods such as box‐counting, Db, particle‐counting, Df, and mass fractal dimension, Dm, have been extensively employed to quantify the microstructure of fats. This work revealed the microstructural basis of Db, Df, and Dm in 3D space through both computer simulation and experiments on the high melting fraction of milk fat crystal networks. Similar to our previous simulation study on the fractal dimensions of fat crystal networks in 2D space, Db is sensitive to crystal size, area fraction, and not sensitive to distribution orderliness of crystals, which is the percentage of evenly distributed fat crystals within the simulated fat crystal networks. Df and Dm were not affected by any of the microstructural factors studied in the simulation.
Effect of atorvastatin on plasma levels of asymmetric dimethylarginine in patients with non‐ischaemic heart failure
Authors: Young Joanna M. , Strey Christopher H. , George Peter M. , Florkowski Christopher M. , Sies Christiaan W. , Frampton Christopher M. , Scott Russell S.
Published: April 2008

Background:

Elevated plasma levels of asymmetric dimethylarginine (ADMA), an endothelial nitric oxide synthase (eNOS) inhibitor, may contribute to endothelial dysfunction in chronic heart failure (CHF). Since statins upregulate eNOS and ameliorate endothelial dysfunction in non‐ischaemic CHF, we hypothesized that this may be in part through modification of ADMA.

Aim:

To evaluate the effect of atorvastatin on the relationship between ADMA and endothelial function in non‐ischaemic CHF.

Methods:

Twenty‐four patients with CHF (ejection fraction <40%, New York Heart Association Functional Classes II and III) were randomised to atorvastatin treatment (40 mg) or placebo once daily for 6 weeks in a double‐blinded, placebo‐controlled crossover study. Plasma ADMA and L‐arginine levels were measured by HPLC. Endothelial function was assessed by flow‐mediated dilatation and invasive forearm plethysmography.

Results:

Post‐statin therapy, endothelial function was improved (p<0.05) independent of LDL‐cholesterol reductions, but no changes were observed in ADMA levels or the L‐arginine to ADMA ratio. There was a trend for ADMA to inversely correlate with endothelial function at baseline.

Conclusions:

Short‐term atorvastatin treatment in non‐ischaemic CHF improves endothelial function but has no effect on ADMA or the L‐arginine to ADMA ratio. Our finding suggests that the observed statin‐induced improvements in endothelial function are likely mediated via alternative pathways.