bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of shielded broadside‐coupled substrate striplines
Authors: Musa Sarhan M. , Sadiku Matthew N. O.
Published: November 2008

Broadside‐coupled substrate striplines represent an essential part of modern integrated circuits. In this article, we will illustrate modeling of inhomogeneous quasi‐TEM shielded broadside‐coupled substrate striplines using the finite element method (FEM). FEM is especially suitable and effective for the computation of electromagnetic fields in strongly inhomogeneous media. We illustrate that FEM is suitable and effective as other methods for modeling shielded broadside‐coupled substrate striplines. We specifically determine the capacitance per unit length, even mode impedance, odd mode impedance, and characteristic impedance of shielded broadside‐coupled suspended striplines. Excellent agreement with some results obtained previously is demonstrated. We extended the modeling by designing our own model of shielded broadside‐coupled inverted microstrip line and determine the capacitance per unit length, even mode impedance, odd mode impedance, and characteristic impedance. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 9–13, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23960
A new silicon‐based photoconductive microwave switch
Authors: Flemish Joseph R. , Kwan Henry W. , Haupt Randy L. , Lanagan Michael
Published: November 2008

A silicon‐based photoconductive microwave switch has been designed and fabricated within a coplanar waveguide on a high resistivity Si substrate. This device offers improved signal attenuation per incident optical power when compared with other types of optically controlled attenuators that have been reported. Attenuation of more than 30 dB was achieved by illumination from a single infrared LED. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 248–252, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23961
L‐band erbium doped fiber amplifier based on a large mode area fiber
Authors: Dragic Peter D.
Published: November 2008

We present a single‐pass L‐band erbium doped fiber amplifier (EDFA) based on a large mode area (LMA) fiber. A single transverse mode is maintained through restricted mode launch. Pump light near 974 nm is sent into the core and has high spatial overlap with the signal beam, helping to preserve single mode propagation. Up to +27 dB of pump power limited small signal gain (30 μW signal input) with a noise figure (NF) near 4.4 is achieved in a relatively short fiber[b]. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 173–175, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23966
Analysis of planar microwave circuits with lumped‐elements by CN‐FDTD
Authors: Tang Wanchun , Nai Yu , Yu Zhengyong
Published: November 2008

A three‐dimensional implementation of the lumped‐element by Crank‐Nicolson finite‐difference time‐domain (CN‐FDTD) algorithm has been presented in this article. Several examples of planar microwave circuits with lumped resistor, capacitor, and/or inductor are simulated and compared with traditional finite‐difference time‐domain method and measurements. The accuracy of CN‐FDTD implementation for lumped elements in this article has been verified. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 113–116, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23969
UMTS radio over fiber link performance analysis based on low‐cost uncooled laser
Authors: Brizido A. , Lima M. , Teixeira A. , Larrode M. , Koonen T.
Published: November 2008

The performance of an UMTS radio over fiber link based on directly modulated lasers has been experimentally evaluated in terms of the error vector magnitude (EVM). Operational range for standard EVM values (<12%) was achieved in terms of distance and power. Also, the effect of a semiconductor optical amplifier on these signals in mono and multiwavelength was observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 6–9, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23975
A self‐checking technique for materials characterization using calibration‐independent measurements of reflecting lines
Authors: Hasar U. C.
Published: November 2008

There is a need for a method for the performance evaluation of calibration‐independent measurements of dielectric materials located into a measurement cell (a coaxial or waveguide section) before starting the extraction of the complex permittivity of the sample. This is important since such a method can signal the accurateness of measurements and even may show any problem of numerical methods used for the permittivity extraction. In this article, we present a metric function derived for reflecting cells, in which the samples partially or completely fill. The function is validated by uncalibrated scattering parameter measurements. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 129–132, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23978
Compact harmonic control network for Doherty power amplifier
Authors: Colantonio Paolo , Giannini Franco , Giofrè Rocco , Piazzon Luca
Published: November 2008

In this contribution, an innovative design solution to realize small size Doherty power amplifier is presented. The idea consists in the realization of a unique output matching network for both carrier and peaking devices without losing the Doherty behavior. Experimental results performed on uneven Doherty amplifier using GaN HEMT device is given to demonstrate the proposed approach. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 256–258, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23983
Low profile DOA finder at 2.4 GHz
Authors: Uthansakul M. , Uthansakul P. , Sangmanee N. , Sangpradittara S.
Published: November 2008

Technique to find direction of arrival (DOA) has been promisingly constructed by smart antenna technology. It consists of array antennas and signal processing unit. Because of the limitation of space in commercial products, the size of antenna array should be designed with the smallest dimension. Also the processing unit is expected in low complexity and expense. Most of DOA finders were recently proposed employing linear array in which the size is linearly increased as a number of antenna elements. Also the processing units were fully comprised with high level of computation. In this paper, the low profile of 2.4 GHz DOA finder is proposed. The DOA finder is designed in the compact size of 2 × 2 array antennas. Using modified Butler matrix, the processing unit is very simple in which it can be handled by any economic microprocessors. The proposed finder is able to delicately specify DOA in every angle from 0° to 360°. The experimental results confirm the success of proposed DOA finder. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 252–256, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23984
A 24‐GHz 90‐nm CMOS injection‐locked frequency divider
Authors: Lee Chien‐Feng , Jang Sheng‐Lyang
Published: November 2008

This article presents a fully integrated 24‐GHz divide‐by‐2 injection‐locked frequency divider (ILFD). The circuit was implemented using a standard 90‐nm CMOS process. The ILFD consists of a VCO core and injection MOS for injection signal to the resonator. Two injection MOSFETs are in series with the cross‐coupled transistors. The measurement results show that at the supply voltage of 1.2 V, the free‐running ILFD is tunable from 11.4 to 12.11 GHz. The locking range is from 21.93 to 27.11 GHz. The output phase noise of the locked ILFD is −109.82 dBc/Hz at 10‐KHz offset frequency from the 12 GHz. The core power consumption is 4.32 mW at the supply voltage of 1.2 V. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 32–36, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23986
2.45 GHz inter‐/intraboard wireless communication using a CPW‐fed vertical bow‐tie antenna
Authors: Kim J. K. , Cha S. Y. , Yun T. S. , Yoon Y. K.
Published: November 2008

Coplanar waveguide (CPW)‐fed vertically standing bow‐tie antennas for 2.45 GHz ISM band applications for inter‐/intraboard wireless communication are presented. The vertical antenna scheme provides wave propagation in the horizontal direction parallel to the substrate, allowing effective in‐plane board‐to‐board communication. The monopole bow‐tie antenna is implemented in an air‐lifted fashion, resulting in high efficiency, broad bandwidth, and small footprint compared with the conventional surface mounted patch type antenna. The vertical bow‐tie antenna with a height of 22.4 mm and a flare angle of 43° shows a 10‐dB bandwidth of 20.4%, a footprint of ∼1 mm2, and a height reduction of 33% compared with a cylindrical monopole counterpart. A numerical analysis has been performed between 1 and 4 GHz and the transmission characteristics using two identical antennas have been performed at 2.45 GHz with a network analyzer. The numerical results are in good agreement with experimental data. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 266–269, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23988
Bandwidth enhancement of K‐band CMOS mixer using balun matching for UWB radar
Authors: Yu Han‐Yeol , Choi Sung‐Sun , Kim Sung‐Hyun , Kim Yong‐Hoon
Published: November 2008

A K‐band double balanced mixer with 1.9 GHz ultra‐wide bandwidth in a 0.18 μm CMOS technology is presented in this article. Baluns with slot pattern ground were applied to the proposed mixer for an ultra‐wide band matching in RF and LO ports. The mixer down converts RF signals (23.1–25 GHz) to intermediate frequency signals (100 MHz–1 GHz) using a LO signal of 24.1 GHz. The mixer achieves a conversion gain of 3.4 dB with a RF signal of 24 GHz and a LO signal of 24.1 GHz. A 1 dB compression point of the mixer is −4 dBm, and the mixer consumes 20 mA current with a 1.8 V supply. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 232–235, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23991
Miniaturized dual‐passband microstrip filter based on double‐split complementary split ring and split ring resonators
Authors: Genc Alper , Baktur Reyhan
Published: November 2008

We present a miniaturized dual‐passband filter module designed using double‐split complementary split ring resonator (DS‐CSRR) and split ring resonator (SRR). The use of SRR results in a significant size reduction of the filter comparing with edge‐coupled‐line filters. Two passbands are individually printed on two sides of a Rogers 3010 substrate, consequently providing a novel and compact integration. Coupling between two bands is weak, so they can be independently designed and tuned. Both bands operate at fundamental mode, providing an increased stability. A prototype dual‐band filter basic cell is fabricated and the measurement agrees well with simulations by Agilent's momentum. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 136–139, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23996
Miniaturization of wideband branch‐line couplers using fractal‐shaped geometry
Authors: Chen Wen‐Ling , Wang Guang‐Ming , Zhang Chen‐Xin
Published: November 2008

In this article, we present a technique to miniaturize the cascaded wideband branch‐line couplers using fractal‐shaped geometry. As an example, four‐branch couplers operated at 2.0 GHz employing Koch fractal shapes of different iteration orders have been designed successfully. By meandering the branch lines in accordance with the structures of the Koch curves, the fractal‐shaped couplers of first and second iteration orders achieved 50.4% and 72.7% size reduction, respectively, with no major effect to overall performances. The technique was verified by the measurement results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 26–29, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24002
Accurate design of a compact superconducting microstrip filter
Authors: Peng Huili , Guo Xubo , Jin Shichao , Piao Yunlong , Zhang Xiaoping , Wei Bin , Gao Baoxin , Cao Bisong
Published: November 2008

This article presents a six‐pole high‐temperature superconducting (HTS) filter at 2.5 GHz with a compact size of 10 mm × 15 mm on MgO substrate. Twin‐spiral resonators with high simulation accuracy are used in the design procedure. EM simulations verify that the filter response is insensitive to the variations of the cell sizes and the substrate parameters. The untuned measurement of the HTS filter at 70 K shows a high performance. The minimum return loss is 14.7 dB without any tuning. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 141–144, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24018
A probe‐fed patch antenna with a step‐shaped ground plane for 2.4 GHz access point
Authors: Chang Fa‐Shian , Liu Yung‐Tao , Su Saou‐Wen , Chou Jui‐Hung
Published: November 2008

This letter demonstrates a new design of a probe‐fed patch antenna with a modified antenna ground, and a constructed prototype ideal for applications in a 2.4‐GHz WLAN access point is presented. The antenna has a thick air substrate for broadband operation and is fed by an inclined probe pin at the edge of the patch bent portion. The antenna ground comprises different portions and is in the shape of a step. With the proposed probe feed and ground configuration, good impedance bandwidth with VSWR below 1.5 over the 2.4 GHz WLAN band can be obtained. In addition, good broadside radiation characteristics have also been observed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 139–141, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24019
Application of asymptotic waveform evaluation technique in the on‐surface discretized boundary equation method
Authors: Wang Kan , Xu Yun‐Sheng
Published: November 2008

The recently developed on‐surface discretized boundary equation (OS‐DBE) method for scattering by a conducting cylinder allows an independent determination of the current density at any given point on the object surface with a matrix of smaller order than that in the method of moments. However, the generation of the whole current distribution requires repeated calculations at many points. To improve the numerical efficiency, this article incorporates the asymptotic waveform evaluation technique into the OS‐DBE method to reduce the number of current calculation points at which the utilization of the OS‐DBE is necessary. Numerical results are presented to demonstrate the validity and efficiency of the proposed technique. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 67–70, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24022
Degeneration of dementia with Lewy bodies measured by diffusion tensor imaging
Authors: Ota Miho , Sato Noriko , Ogawa Masafumi , Murata Miho , Kuno Sadako , Kida Jiro , Asada Takashi
Published: November 2008

Dementia with Lewy bodies (DLB) is the second most common form of dementia. It is thought to involve impairment of the visual association area. In this study, we applied diffusion tensor imaging (DTI) to examine the microstructural interruption of visual association areas in patients with DLB. The DTI metrics of three visual association fibres – the inferior longitudinal fasciculus (ILF), visual pathway, and splenial fibres – were compared between 14 patients with DLB and 13 healthy subjects. The fractional anisotropy value of the ILF was significantly lower in patients with DLB than in healthy subjects. The difference in the mean diffusivity value of ILF was at trend level. The λ2,3 of ILF were significantly lower in patients with DLB; however, there was no difference in λ1. DTI metrics of the visual pathway and splenial fibres showed no differences between the groups. Our results showed degeneration of the ILF, which is responsible for visuospatial cognition. ILF dysfunction may influence the clinical features in DLB. Copyright © 2008 John Wiley & Sons, Ltd.
Real‐time scheduling of multiple uncertain receding horizon control systems
Authors: Gholami Behnood , Gordon Brandon W. , Rabbath C. A.
Published: November 2008

In this paper, a new scheduling approach is proposed that considers the effect of modeling uncertainty for multiple continuous time receding horizon control (RHC) systems. This is accomplished by combining a scheduling approach with results from the continuous time nonlinear systems theory. It is shown that using a rate monotonic priority assignment method combined with analytical bounds on the prediction error, the problem of scheduling multiple uncertain plants can be cast into an appropriate constrained optimization problem. The constraints guarantee that the processes will be schedulable. The optimization provides optimized performance and balanced resource allocation in the presence of uncertainty. The proposed method was applied to a real‐time simulation of RHC trajectory tracking for two hovercraft vehicles demonstrating the validity of the approach. Copyright © 2008 John Wiley & Sons, Ltd.
Attributes of adult stem cells
Authors: Alison MR , Islam S
Published: November 2008

While cultured embryonic stem (ES) cells can be harvested in abundance and appear to be the most versatile of cells for regenerative medicine, adult stem cells also hold promise, but the identity and subsequent isolation of these comparatively rare cells remains problematic in most tissues, perhaps with the notable exception of the bone marrow. The ability to continuously self‐renew and produce the differentiated progeny of the tissue of their location are their defining properties. Identifying surface molecules (markers) that would aid in stem cell isolation is a major goal. Considerable overlap exists between different putative organ‐specific stem cells in their repertoire of gene expression, often related to self‐renewal, cell survival and cell adhesion. More robust tests of ‘stemness’ are now being employed, using lineage‐specific genetic marking and tracking to show production of long‐lived clones and multipotentiality in vivo. Moreover, the characterization of normal stem cells in specific tissues may provide a dividend for the treatment of cancer. The successful treatment of neoplastic disease may well require the specific targeting of neoplastic stem cells, cells that may well have many of the characteristics of their normal counterparts. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Acquired von Willebrand syndrome and Wilms tumor: Not always benign
Authors: Baxter Patricia A. , Nuchtern Jed G. , Guillerman Robert P. , Mahoney Donald H. , Teruya Jun , Chintagumpala Murali , Yee Donald L.
Published: November 2008

Current literature suggests that acquired von Willebrand syndrome associated with Wilms tumor (AVWS‐WT) occurs infrequently and usually has little clinical significance. Treatment strategies are thus poorly defined. We describe two patients with AVWS‐WT and profuse bleeding who required intensive multimodal therapy, including aggressive blood component and factor replacement and plasmapheresis. They achieved adequate surgical hemostasis only after the renal vessels were ligated, with resolution of the coagulopathy upon tumor removal. Our experience suggests that AVWS‐WT is not always benign. A careful bleeding history should always be obtained in patients with suspected renal tumors for consideration of pre‐operative screening for AVWS. Pediatr Blood Cancer 2009;52:392–394. © 2008 Wiley‐Liss, Inc.
Both location and age predict survival in ependymoma: A SEER study
Authors: McGuire Courtney S. , Sainani Kristin L. , Fisher Paul Graham
Published: November 2008

Background

Studies have suggested that supratentorial ependymomas have better survival than infratentorial tumors, with spinal tumors having the best prognosis, but these data have been based on small samples. Using a population‐based registry of ependymomas, we analyzed how age, gender, location, race and radiotherapy influence survival in children.

Methods

We queried the Surveillance Epidemiology End Results database (SEER‐17) from 1973 to 2003, strictly defining ependymomas by histology. Site codes were used to distinguish between supratentorial, infratentorial, and spinal tumors when available. Outcomes were compared by location, age, gender, race and radiotherapy, using Kaplan–Meier analysis and logrank tests. Cox regression was completed, incorporating all significant covariates from univariate analysis.

Results

Six hundred thirty‐five children were identified with an overall 5‐year survival of 57.1 ± standard error (SE) 2.3%. Increasing age was associated with improved survival (P < 0.0001). Five‐year survival by location was 59.5 ± SE 5.5% supratentorial, 57.1 ± SE 4.1% infratentorial and 86.7 ± SE 5.2% spinal. Radiotherapy of the infratentorial tumors resulted in significantly improved survival in both univariate analysis (logrank P < 0.018) and multivariate analysis restricted to this tumor location (P = 0.033). Using multivariate analysis that incorporated all tumor locations, age (P < 0.001) and location (P = 0.020) were significant predictors for survival.

Conclusions

Age and location independently influence survival in ependymoma. Spinal tumors are associated with a significantly better prognosis than both supratentorial and infratentorial tumors, and may represent a distinct biological entity. Radiotherapy appears beneficial for survival in patients with infratentorial ependymoma. Pediatr Blood Cancer 2009;52:65–69. © 2008 Wiley‐Liss, Inc.
Analysis of biological prognostic factors using tissue microarrays in neuroblastic tumors
Authors: Piqueras Marta , Navarro Samuel , Castel Victoria , Cañete Adela , Llombart‐Bosch Antonio , Noguera Rosa
Published: November 2008

Background

Neuroblastic tumors (NT) are pediatric neoplasms with a heterogeneous genetic profile. They present genotypic alterations of prognostic value, the study of which is mandatory in designing therapeutic management. Tissue microarrays (TMA) from paraffin material allow the analysis of a large number of cases with minimal costs. The main purpose of the present study is to analyze specific genetic markers of neuroblastic tumors included in TMAs and determine their prognostic value. We compare the results obtained by different molecular techniques at different substrates to evaluate the feasibility of these assays.

Procedure

One hundred thirty‐nine samples were included in four different TMAs. We performed FISH assays to determine the status of MYCN gene, 1p36 region and 17q23 arm. The prognostic value of the genetic markers as well as the statistical correlation among clinical variables and outcome were analyzed by SPSS.

Results

MYCN amplification was detected in 35.3% of the cases, whereas 1p36 deletion and 17q23 gain was observed in 46.8% and 58.3% of the cases, respectively. An adverse prognosis was noted among these patients. Other adverse factors were age (>18 months) as well as high stage of disease (stage 4). Phenotypic signs of differentiation correlated with good outcome.

Conclusion

Retrospective studies using paraffin‐embedded tissues assembled in TMA are a useful tool for the analysis of prognostic factors in NT. Pediatr Blood Cancer 2009;52:209–214. © 2008 Wiley‐Liss, Inc.
High‐resolution array genomic hybridization in prenatal diagnosis
Authors: Friedman J. M.
Published: November 2008

Array genomic hybridization (AGH) can detect chromosomal gains or losses that are 100 times smaller than those identifiable by conventional cytogenetic methods. Genome‐wide AGH can identify genomic imbalance that causes birth defects and mental retardation at least twice as frequently as conventional cytogenetic analysis. Using AGH as a prenatal test for fetal genomic imbalance offers the promise of detecting pathogenic gain or loss of genomic material more quickly and much more frequently than current methods. However, the chance of finding a result of uncertain clinical significance is much greater than with conventional cytogenetic analysis, and the benefit–cost ratio of doing AGH in addition to conventional cytogenetic analysis in pregnancies at high risk for Down syndrome is likely to be poor. Very little is known about the natural history and range of clinical variability associated with most pathogenic submicroscopic copy number variants (CNVs). It seems doubtful that patients can be adequately counseled for prenatal AGH testing in most cases because the risks and benefits are unknown. At present, AGH should be offered for prenatal diagnosis only if the pregnancy is at especially high risk of having a pathogenic CNV or if AGH is being done as part of a clinical trial. Copyright © 2008 John Wiley & Sons, Ltd.
Pediatric drug surveillance and the food and drug administration's adverse event reporting system: an overview of reports, 2003–2007
Authors: Johann‐Liang Rosemary , Wyeth Jo , Chen Min , Cope Judith U.
Published: November 2008

Purpose

Our objective was to examine the numbers and characteristics of US pediatric adverse events (AEs) reported to the Food and Drug Administration (FDA)'s adverse event reporting system (AERS) for 5 years following implementation of the Best Pharmaceuticals for Children Act (BPCA) in 2002.

Methods

We analyzed reports in AERS received by FDA from January 1, 2003 to January 1, 2008 for overall numbers, age, gender, and seriousness of outcome in children and adults. Pediatric and adult age groups (<2, 2–10, 11–17, 18–50, and >50 years of age) were further evaluated for most frequently reported suspect drug classes and AEs.

Results

Seventy‐two percent of 815 267 crude count reports had specified age information. Six percent of the total reports with age information reported age <18 years. Numbers of AEs being reported for children have remained steady, while those for adults have increased. The proportion of serious AEs reported was similar for pediatrics as compared to adults. Frequently reported suspect drug classes noted in pediatric age groups that were not observed in adults included anticonvulsants, attention deficit hyperactivity disorder (ADHD), anti‐acne, and respiratory medications.

Conclusions

This overview highlights the need for strengthening the passive drug surveillance system from a pediatric perspective, as well as investing in more active surveillance systems. Drug safety initiatives to better capture risk information in order to balance the risk/benefit of drug use in children. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis, characterization, and bulk properties of amphiphilic copolymers containing fluorinated methacrylates from sequential copper‐mediated radical polymerization
Authors: Hansen Natanya M. L. , Gerstenberg Michael , Haddleton David M. , Hvilsted Søren
Published: November 2008

The partly fluorinated monomers, 2,2,2‐trifluoroethyl methacrylate (3FM), 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate (8FM), and 1,1,2,2‐tetrahydroperfluorodecyl methacrylate (17FM) have been used in the preparation of block copolymers with methyl methacrylate (MMA), 2‐methoxyethyl acrylate (MEA), and poly(ethylene glycol) methyl ether methacrylate (PEGMA) by Atom Transfer Radical Polymerization. A kinetic study of the 3FM homopolymerization initiated with ethyl bromoisobutyrate and Cu(I)Br/N‐(n‐propyl)‐2‐pyridylmethanimine reveals a living/controlled polymerization in the range 80–110 °C, with apparent rate constants of 1.6 · 10−4 s−1 to 2.9 · 10−4 s−1. Various 3FM containing block copolymers with MMA are prepared by sequential monomer addition or from a PMMA macroinitiator in all cases with controlled characteristics. Block copolymers of 3FM and PEGMA resulted in block copolymers with PDI < 1.22, whereas block copolymers from 3FM and MEA have less controlled characteristics. The block copolymers based on MMA with 8FM and 17 FM have PDI's < 1.30. The glass transition temperatures of the block copolymers are dominated by the majority monomer, as the sequential monomer addition results in too short pure blocks to induce observable microphase separation. The thermal stability of the fluorinated poly((meth)acrylate)s in inert atmosphere is less than that of corresponding nonfluorinated poly((meth)acrylate)s. The presence of fluorinated blocks significantly increases the advancing water contact angle of thin films compared to films of the nonfluorinated poly((meth)acrylate)s. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8097–8111, 2008
Preparation of polybenzoxazole fibers via electrospinning and postspun thermal cyclization of polyhydroxyamide
Authors: Hsu Steve Lien‐Chung , Lin Kuen‐Shian , Wang Chi
Published: November 2008

Polybenzoxazole (PBO) fibers with a submicron diameter were successfully prepared by electrospinning its precursor, polyhydroxyamide (PHA), solutions to obtain the PHA fibers first, followed by appropriate thermal treatments for cyclization reaction. BisAPAF‐IC PHA with two different molecular weights (MWs) were synthesized from a low temperature polymerization of 2,2′‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane (BisAPAF) and isophthaloyl chloride (IC). Using dimethylacetamide (DMAc) and tetrahydrofuran (THF), solvent effects on the electrospinnability of PHA solutions were investigated. For balancing the solution properties, it was found that DMAc/THF mixture with a weight ratio of 1/9 was the best cosolvent to prepare smooth PHA fibers; uniform PHA fibers with a diameter of 325–720 nm were obtained by using 20 wt % PHA/(DMAc/THF) solutions. For a fixed PHA concentration, solutions with a lower MW of PHA yielded thinner electrospun fibers under the same electrospinning condition. After obtaining the electrospun BisAPAF‐IC PHA fibers, subsequent thermal cyclization up to 350 °C produced the corresponding thermally stable BisAPAF‐IC PBO fibers with a diameter of 305–645 nm. The structure of the precursor fibers and the fully cyclized fibers were characterized by FTIR. For the cyclized BisAPAF‐IC PBO fibers, thermogravimetric analysis showed a 5% weight loss temperature at 523 °C in nitrogen atmosphere. The interconnected fiber structure in the BisAPAF‐IC PBO fiber mats was irrelevant to the curing process, but resulted from the jet merging during the whipping process as revealed by the high speed camera images. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8159–8169, 2008
Monitoring Batch Cooling Crystallization Using NIR: Development of Calibration Models Using Genetic Algorithm and PLS
Authors: Li Rui F. , Wang Xue Z. , Abebe Solomon B.
Published: November 2008

Near infrared spectroscopy (NIR) uses fiber‐optics for rapid data transmission, is robust, simple, and sensitive at both low and high solution concentrations. Therefore, it is particularly suitable for monitoring industrial processes. This study investigates the use of NIR for monitoring batch cooling crystallization processes, and emphasis is placed on applying genetic algorithm (GA) for wavelength selection in partial least squares calibration model development. The calibration data was collected for under‐saturated and saturated solutions, as well as for α‐ and β‐form crystal slurries of L‐glutamic acid at a variety of solution concentrations, temperatures, and solid concentrations and sizes. The GA method proves to be capable of effectively selecting a small number of wavelengths and the models thus developed give improved prediction performance in terms of generalization capability compared to models derived using the full spectrum. The developed models are successfully applied to monitoring batch cooling crystallization of L‐glutamic acid under seeded and unseeded conditions and with varied cooling rates.
Is chest sonography a breakthrough in diagnosis of pulmonary thromboembolism in children?
Authors: Kosiak Mateusz , Korbus‐Kosiak Anna , Kosiak Wojciech , Potaz Piotr
Published: November 2008

Objective

Sonographic criteria of pulmonary thromboembolism (PTE) have been already evaluated basing on adult patients. There are limited studies to determine diagnostic value of chest ultrasound (CUS) in pediatric PTE. The aim of our study was to present usefulness of ultrasound examination of chest in diagnosis of PTE in children.

Material and Methods

We present results of chest ultrasound examinations of six children: three teenagers—13‐year‐old boy treated for primary antyphospholipid syndrome, 14‐year‐old boy with Wegeners' granuloma, and 15‐year‐old girl with urosepsis—where sonographic results were compared to CT results, and three newborns with congenital heart disease—two boys treated for hypoplastic left heart syndrome (HLHS) and one for duct‐dependent coarctation of the aorta (CoA, PDA). Because of severe clinical condition of the newborns, other imaging tests could not be performed. Ultrasound examination was performed as bedside emergency examination using GE Logic 500 with linear probe 8.2–11.0 MHz.

Results

In all cases suggestion of PTE was based on ultrasound examination. Sonograms showed: bilateral, peripheral, subpleural, hypoechoic, triangular and oval lesions, accompanied by pleural effusion. In all three teenagers the diagnosis of PTE was confirmed by CT.

Conclusions

Bedside chest ultrasound examination is especially useful in children with high risk of PTE and in critical general condition. In newborns in severe general condition ultrasound examination of chest should be first imaging test for PTE. It is significant to set on a multicenter study to evaluate the diagnostic value of chest ultrasound in diagnosis of PTE in children. Pediatr. Pulmonol. 2008; 43:1183–1187. © 2008 Wiley‐Liss, Inc.
Flexible bronchoscopy in pediatric intensive care
Authors: Davidson Mark G. , Coutts Jonathan , Bell Graham
Published: November 2008

Objective

To define the benefits of a flexible bronchoscopy (FB) service in a Paediatric Intensive Care Unit (PICU).

Design

Review of the first 200 FBs undertaken in a large PICU.

Setting

Large cardiac and medical PICU in the United Kingdom, also providing extra‐corporeal life support.

Patients

129 patients (78 males, 51 females, median age 9.9 months, median weight 4.6kg) underwent FB from August 1990 to June 2003.

Interventions

Broncho‐alveolar lavage (BAL) as indicated at time of bronchoscopy.

Measurements

Basic patient parameters were identified, including ventilation modes and diagnoses. FB findings were correlated with microbiology results.

Main results

The majority of the FBs were diagnostic (161 of 200). 114 of these were undertaken to exclude underlying airway abnormalities and 47 to aid the diagnosis of pneumonia. Therapeutic procedures including bronchial stenting, directed surfactant instillation and broncho‐alveolar toileting were undertaken in 39 cases. 68% of the diagnostic FBs were deemed to be abnormal. 16% had significant extra‐luminal airway obstruction. 24% had new findings of airway anomalies. 14.5% of the FBs showed endo‐tracheal tube misplacement. Positive microbiological results which altered or confirmed changes in patient management occurred in 46.1% children who had BAL specimens cultured. 80 of the FBs were undertaken whilst the children were receiving extra‐corporeal life support. Only one FB procedure was ceased because of patient instability.

Conclusion

There is a high yield of positive findings from undertaking FB both anatomically and microbiologically. FB should be seen as a routine diagnostic and therapeutic tool in paediatric intensive care. Pediatr. Pulmonol. 2008; 43:1188–1192. © 2008 Wiley‐Liss, Inc.
Nanoscale investigation of light‐trapping in a‐Si:H solar cell structures with randomly textured interfaces
Authors: Bittkau Karsten , Beckers Thomas , Fahr Stephan , Rockstuhl Carsten , Lederer Falk , Carius Reinhard
Published: November 2008

Light trapping in thin‐film silicon solar cell arising from randomly textured ZnO front contact layers is investigated in the optical near‐field experimentally and theoretically. The experimental data are obtained from near‐field scanning optical microscopy, theoretical data are calculated using rigorous diffraction theory. The surface of the randomly textured ZnO consists of statistically distributed craters with different shapes. Along the rims of the craters light localizations are found. Photon jets emerge from the vertices of the surface profile. From the theoretical study, the local absorption enhancement is calculated. The results provide important insight into the local effects of light trapping in thin‐film optoelectronic devices and strategies for optimizing the external quantum efficiency in thin‐film silicon solar cells are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Directional selectivity and ultra‐light‐trapping in solar cells
Authors: Ulbrich Carolin , Fahr Stephan , Üpping Johannes , Peters Marius , Kirchartz Thomas , Rockstuhl Carsten , Wehrspohn Ralf , Gombert Andreas , Lederer Falk , Rau Uwe
Published: November 2008

Directional and energy selective optical surface structures attached to solar cells may result in both, enhancement or deterioration of photovoltaic performance of a solar cell. On the one hand, restricting the cell acceptance to the small incidence angle of direct and circumsolar irradiation enhances the maximum path length of the light in a solar cell with Lambertian surfaces even above the Yablonovitch limit (ultra‐light‐trapping). On the other hand, restrictions to small acceptance angles imply losses of diffuse sunlight, even for perfectly tracked cells. Using temporally resolved solar irradiation spectra, we simulate the enhancement and loss in the annual energy yield of silicon solar cells of various thicknesses. We assume an idealized angular and energy selective filter on top of the Lambertian surface of the absorber and compare the results to a Lambertian surface only. We find a maximum annual gain in the energy density of 32.5% for 1 μm, and of ∼10% for 10 μm and 100 μm thick perfectly tracked crystalline silicon solar cells. The simulation implies various tracking modes and two different locations. Finally, we introduce two possible realizations of such a filter; a Rugate stack and inverted opals. In experimental measurements, we could verify the absorptance enhancement by such a structure applied on top of a thin silicon wafer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photonics in photovoltaic systems
Authors: Gombert Andreas , Luque Antonio
Published: November 2008

This paper gives an overview on photonics for photovoltaic systems. Starting from the spectral and angular distribution of the electromagnetic radiation from the sun, many important optical approaches how to improve the efficiency of solar cells are presented and discussed. Topics include antireflective coatings, various light trapping structures, refractive, reflective and fluorescent concentrators, and components for spectral management. The theoretical background is shortly described and examples of the experimental and also of the commercial realisation are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light trapping in organic solar cells
Authors: Niggemann Michael , Riede Moritz , Gombert Andreas , Leo Karl
Published: November 2008

One key problem in optimizing organic solar cells is to maximize the absorption of incident light and to keep the charge carrier transport paths as short as possible in order to minimize recombination losses during the charge carrier extraction. The large versatility of organic semiconductors and compositions requires specific optimization of each system. Due to the small thickness of the functional layers in the order of several ten nanometres, coherent optics has to be considered and therefore interference effects play a dominant role. Here we present and discuss concepts for light trapping in organic solar cells. These are wide gap layers in planar solar cells, folded solar cell architectures benefiting from the illumination under inclined incident angles and multiple reflections and absorptions as well as diffraction gratings embossed into the photoactive layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Can we use the CO2concentrations determined by continuous‐flow isotope ratio mass spectrometry from small samples for the Keeling plot approach?
Authors: Joos Ottmar , Saurer Matthias , Heim Alexander , Hagedorn Frank , Schmidt Michael W. I. , Siegwolf Rolf T. W.
Published: November 2008

A common method to estimate the carbon isotopic composition of soil‐respired air is to use Keeling plots (δ13C versus 1/CO2concentration). This approach requires the precise determination of both CO2concentration ([CO2]), usually measured with an infrared gas analyser (IRGA) in the field, and the analysis ofδ13C by isotope ratio mass spectrometry (IRMS) in the laboratory. We measured [CO2] with an IRGA in the field (n = 637) and simultaneously collected air samples in 12 mL vials for analysis of the13C values and the [CO2] using a continuous‐flow isotope ratio mass spectrometer. In this study we tested if measurements by the IRGA and IRMS yielded the same results for [CO2], and also investigated the effects of different sample vial preparation methods on the [CO2] measurement and the thereby obtained Keeling plot results. Our results show that IRMS measurements of the [CO2] (during the isotope analysis) were lower than when the [CO2] was measured in the field with the IRGA. This is especially evident when the sample vials were not treated in the same way as the standard vials. From the three different vial preparation methods, the one using N2‐filled and overpressurised vials resulted in the best agreement between the IRGA and IRMS [CO2] values. There was no effect on the13C‐values from the different methods. The Keeling plot results confirmed that the overpressurised vials performed best. We conclude that in the cases where the ranges of [CO2] are large (>300 ppm; in our case it ranged between 70 and 1500 ppm) reliable estimation of the [CO2] with small samples using IRMS is possible for Keeling plot application. We also suggest some guidelines for sample handling in order to achieve proper results. Copyright © 2008 John Wiley & Sons, Ltd.
Dynamic perspectives on social characteristics and sustainability in online community networks
Authors: Otto Peter , Simon Martin
Published: November 2008

Online community networks can help organizations improve collaboration. However, in spite of their potential value, there has been little empirical research into two important network factors that determine their success: social characteristics of users and changes in operations that result from network evolution. Our research addresses these deficiencies by using a cultural framework. Derived from anthropology, it extends previous system dynamics research on online community networks. The framework acts as a lens, enabling a better understanding of the effects that changes in these factors bring to online community networks. Using data collected from Wikipedia for model calibration, our findings suggest that, contrary to conventional wisdom, removing policies that focus on building group commitment does not lower performance. The results also show that online networks need structural control, otherwise their attractiveness, credibility and, subsequently, content value might all decrease. To ensure sustainability the network must be monitored, especially during the early stages of its evolution, so that rules and regulations that ensure value and validity can be selectively employed. Copyright © 2008 John Wiley & Sons, Ltd.
Composite beam composed of steel and precast concrete (Modularized Hybrid System, MHS). Part I: experimental investigation
Authors: Hong Won‐Kee , Park Seon‐Chee , Kim Jin‐Min , Lee Seung‐Geun , Kim Seung‐Il , Yoon Ki‐Joon , Lee Ho‐Chan
Published: November 2008

An experimental investigation of composite beams composed of wide flange steel and precast concrete is presented. The bottom flange of the steel section is encased in precast concrete. Utilizing the merits of both steel and concrete material, the size of the steel beams can be reduced without sacrificing performance. The bottom flange of the steel beam is reinforced with concrete at a manufacturing plant, eliminating the use of temporary pour forms. The composite beams were tested to investigate how the size of the wide flange steel and how the top and bottom reinforcements influence the behaviour of the beams. Flexural load carrying capacity, load displacement relationships and failure modes were examined. The test specimens were T‐shaped composite beams with slabs, each measuring 10‐m long. The flexural moment strength of all of the composite beams—at both the yield limit state and the maximum load limit state—was measured and compared with the analytical flexural capacity.

The stiffness degradation, ductility and dissipating energy capabilities of the composite beams were investigated based on the hysteresis curves. The composite beams tested in this study successfully reduced both the floor height of the building and the size of the steel beams needed to meet code requirements. Copyright © 2008 John Wiley & Sons, Ltd.
Fetal and placental malignancies: prenatal diagnosis and management
Authors: Sebire N. J. , Jauniaux E.
Published: November 2008

Fetal and placental malignancies are rare complications during pregnancy, but when they occur they may present significant challenges for the perinatology team. Owing to their rarity, there is limited information on many of these entities, with much data derived from individual case reports or small case series. Prenatal diagnosis of these entities is rare and inconsistent, usually in the form of isolated case reports. In the majority of fetal tumors, prenatal features are those of a mass lesion, with or without other non‐specific features of fetal compromise such as polyhydramnios, fetal hydrops or intrauterine death, the final diagnosis in most cases being based on postnatal pathological examination.

Expectant management is almost always indicated antenatally, with serial ultrasound examinations performed to detect rapid enlargement, metastasis or secondary fetal complications, such as non‐immune hydrops, which may require intervention. Delivery should be planned in a specialist center in conjunction with pediatric surgeons and oncologists to allow appropriate neonatal management. Placental malignancy is most commonly in the form of gestatational trophoblastic disease, which requires assessment and management in specialist centers. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Metacommunity‐level coexistence mechanisms in rocky intertidal sessile assemblages based on a new empirical synthesis
Authors: Noda Takashi
Published: November 2008

Advances in community ecology rely on connecting empirical work to theoretical frameworks. In a metacommunity, various coexistence mechanisms should operate on various spatial scales. This review attempts to provide a new empirical synthesis organizing various coexistence mechanisms operating in real metacommunities. This synthesis is based on (1) theoretical frameworks involving comparative predictions and assumptions of various coexistence hypotheses, and (2) empirical understanding of the context dependency of species interactions relating to environmental heterogeneity. By applying this synthesis to rocky intertidal sessile assemblages, which are model systems for studying competitive coexistence, I attempt to provide several integrative views of coexistence and future prospects for research in this system. Nine types of common coexistence mechanism, including five local coexistence mechanisms, two coexistence mechanisms in a homogeneous competitive environment, and two mechanisms in a heterogeneous competitive environment are found to operate in rocky intertidal sessile metacommunities, and their relative importance varies depending on species group, environment, and spatial scale.