bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel planar triple‐mode bandpass filter with slits perturbation
Authors: Guo L. , Yu Z.‐Y.
Published: March 2011

A novel planar microstrip triple‐mode bandpass filter is proposed by introducing slits into λ/2 traditional microstrip resonator in this article.The slits cannot only perturb the traditional resonator for the multimode operation but also generate transmission zero point at stopband for the stopband control. By using different kinds of slits, different kinds of responses triple‐mode bandpass filter can be realized. For method validation, a filter operating at 2.45 GHz is fabricated and measured. Both the simulated results and the measured results are presented. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1260–1262, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25965
Small‐signal lumped‐element modeling of P‐I‐N photodiode
Authors: Miao Ang
Published: March 2011

A small‐signal lumped‐element modeling technique for P‐I‐N photodiodes is presented.The model is extracted by fitting model's components with the accurately measured S parameters using the genetic algorithm. Experimental results indicate the extracted model is well matched to the measured data in the frequency range from 130 MHz to 20 GHz. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1416–1419, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25971
Enhancing patch antenna bandwidth by means of uniplanar EBG‐AMC
Authors: de Cos M. Elena , Álvarez Yuri , Las‐Heras Fernando
Published: March 2011

The design of a bandwidth‐enhanced uniplanar MPA using EBG‐AMC is presented.The designed structure with neither via holes nor multilayer substrates yields bandwidth enhancement still with useful radiation pattern values in its band. Two prototypes, a MPA and a PA with uniplanar EBG‐AMC (PA_U‐EBG‐AMC), are manufactured and characterized based on return losses and radiation pattern. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1372–1377, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25974
A Ka‐band quasi‐optical power‐divider basing on Talbot Effect of phase grating
Authors: Li Guang , Huang Jian , Pei Naichang
Published: March 2011

A new design of quasi‐optical (QO) power divider at millimeter wave band is presented in this article. The Talbot Effect of periodical phase grating is applied to realize power dividing with high efficiency. A novel periodic phase profile was adopted to make a linear region of zero diffraction filed. Then a closed metallic cavity can be used to screen the power divider with the wall placed in this region without disturbance to field distribution and efficiency degrading, which improves electromagnetic compatibility of QO power combining system greatly. The Scalar Diffraction theory is applied to analyze the “Talbot Pattern” and then generic algorithm is used to optimize the phase profile. A 1 × 18 divider was designed and tested at 37.5GHz. The efficiency is tested to be 80.8%, which is well agreed with the simulated value of 88.7%. Since efficiency of QO power divider/combiner is essentially independent of the number of combining elements and the inter‐element spacing, this technology can be extended to power dividing or combining of large number of ways up to THz band. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1331–1336, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25975
An empirical I‐V nonlinear model suitable for GaN FET class F PA design
Authors: García‐Osorio A. , Loo‐Yau J. R. , Reynoso‐Hernández J. A. , Ortega‐C. Susana , del Valle‐Padilla J. L.
Published: March 2011

This article presents an improved nonlinear IDS(VGS, VDS) model useful for modeling the experimental pulsed I‐V measurement data of GaN FETs operated at large drain‐source voltages. This improved IDS(VGS, VDS) model is based on the Chalmers model. The main features of the improved nonlinear IDS(VGS, VDS) model are the two analytical expressions that are incorporated to model the output conductance and the saturation voltage. The new model only requires 13 parameters easily determined from experimental pulsed I‐V data. Comparison between simulated and measured data of an inverse class F PA designed with a commercial GaN FET at 1.5 GHz demonstrate that the proposed model is suitable for microwave circuit design based on GaN transistors. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1256–1259, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25980
Broadband bluetooth antenna based on Co2Z hexaferrite‐glass composite
Authors: Lee Jaejin , Hong Yang‐Ki , Bae Seok , Abo Gavin S. , Jalli Jeevan , Park Jihoon , Seong Won‐Mo , Park Sang‐Hoon , An Won‐Gi , Kim Gi‐Ho
Published: March 2011

Bluetooth ferrite antenna was fabricated on Co2Z (Ba3Co2Fe24O41) hexaferrite‐glass composite substrate and characterized. The fabricated antenna has a total volume of 36 mm3 (3 × 8 × 1.5 mm3) and showed wide bandwidth (390 MHz at VSWR < 2). The maximum 3D peak‐gain and radiation efficiency were measured to be 3.32 dBi at 2.35 GHz and 77.7% at 2.3 GHz, respectively. The 3D peak gain of 2.45 dBi and 3D average gain of −1.89 dBi were obtained at the Bluetooth central frequency of 2.45 GHz. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1222–1225, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25982
Internal eight‐band WWAN/LTE handset antenna using loop shorting strip and chip‐capacitor‐loaded feeding strip for bandwidth enhancement
Authors: Wong Kin‐Lu , Chang Yu‐Wei
Published: March 2011

A planar inverted‐F antenna (PIFA) with a loop shorting strip and a chip‐capacitor‐loaded feeding strip to achieve a small size yet wideband operation for eight‐band WWAN/LTE operation (698˜960/1710˜2690 MHz) in the mobile handset is presented.The antenna occupies a small no‐ground footprint of 15 × 35 mm2 on the main circuit board of the handset and is closely integrated with the surrounding system ground plane to achieve compact integration inside the handset. By applying the proposed shorting strip and feeding strip, a dual‐resonance excitation at about 800 MHz which forms the antenna's wide lower band to cover the LTE700/GSM850/900 operation is obtained. Further, the proposed shorting strip and feeding strip lead to the generation of additional higher‐order resonant modes to assist in forming a wide upper band for the antenna to cover the GSM1800/1900/UMTS/LTE2300/2500 operation. The proposed antenna also shows good radiation characteristics over the eight operating bands. The obtained SAR values of the antenna are well less than the limit of 1.6 W/kg for 1‐g head tissue for practical handset applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1217–1222, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25983
Time delay estimation of UWB radar signals backscattered from a wall
Authors: Protiva Pavel , Mrkvica Jan , Macháč Jan
Published: March 2011

Estimating the basic characteristics of a wall is especially important in the field of through‐wall radar imaging. In this article, we focus on the time delay estimation of signals measured by an ultra‐wideband short‐pulse radar. We describe the essential signal preprocessing steps, which are applied before a subspace super‐resolution method is used to estimate the time delays of overlapping pulses backscattered from the wall. The signal correlation matrix is estimated using only one snapshot of the measured data, and the algorithm can operate in real time. In addition, to resolve closely spaced correlated echoes, we apply an improved spatial smoothing method. The performance of our algorithm is verified by simulations, and we also present the measurement results for two real brick walls. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1444–1450, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25985
Marching‐on‐in‐order time‐domain volume‐surface integral equations in analysis of transient electromagnetic scattering from composite conducting–dielectric objects
Authors: Wang Q. Q. , Yan C. , Shi Y. F. , Ding D. Z. , Chen R. S.
Published: March 2011

In this letter, the matching‐on‐in‐order time‐domain volume‐surface integral equation method is used to analyze transient electromagnetic scattering from objects comprising both conductor and dielectric material. SWG and RWG basis functions are used as the spatial basis functions in dielectric region and on the conducting surface, respectively. Different orders of weighted Laguerre polynomials are used as temporal basis functions, and the relative expansion coefficients are solved recursively order by order. The spatial and temporal testing procedures are separate, and both of them are carried on with the Galerkin's method. Stable solutions are ensured, and several numerical results are given to verify the proposed method. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1315–1319, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25987
A novel single‐band RF front‐end module for wireless communication systems
Authors: Kim Dong Ho , Kim Dongsu , Kim Jun Chul , Park Chong Dae
Published: March 2011

In this article, a novel integrated RF front‐end module (FEM) for wireless communication system is realized by low temperature co‐fired ceramic (LTCC) technology.The proposed RF FEM has four ports and consists of a novel selectable filter, balun, which are fully embedded in the LTCC substrate, and two PIN diodes. This novel selectable filter can be applied for either lowpass filter (LPF) for Tx path or bandpass filter (BPF) for Rx path by simply making output port to be shorted to the ground. The fabricated single‐band RF FEM has nine pattern layers including two ground layers and it occupies less than 2.3 × 4.0 × 0.44 mm3. In case of Tx path, the measured insertion loss at 2‐GHz band is less than 2.3 dB and a return loss of more than 16.8 dB. Furthermore, it provide a more than 40.5 dB second harmonic suppression at 2‐GHz is obtained. In case of Rx path, the measured insertion loss at 2‐GHz band is less than 1.2 dB and a return loss of more than 16.7 dB. The measured results of the implemented RF FEM are in good agreement with the simulated results. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1349–1352, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25991
Study on the reader baseband receiver structure for the demodulation of subcarrier signal in a passive RFID environment
Authors: Bae Ji‐Hoon , Kim Kyung‐Tae , Choi WonKyu , Park Chan‐Won , Pyo Cheol‐Sig
Published: March 2011

In this article, we present a subcarrier demodulation structure to eliminate an undesirable DC‐offset phenomenon, which may appear in the baseband of the reader receiver under passive radio frequency identification environment.To achieve the requirement, the primary feature of the proposed demodulation structure is to reconstruct the signal corrupted by the DC‐offset phenomenon by creating peak signals from the corrupted signal. In the case of the Miller subcarrier signal, the phase inversion information in the symbol duration is used for generating the peak signal. It is shown that the proposed method can successfully detect valid data from the received signal, even when the received baseband signal is distorted by the DC‐offset phenomenon. In addition, the performance of the proposed method is slightly better than or comparable to that of the well‐known‐matched filter‐type baseband receiver in the band‐limited channel environments. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1264–1272, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25995
Simultaneous all‐optical amplification, inversion and format conversion based on self‐induced nonlinear effects in a semiconductor optical amplifier
Authors: Xie Yanqiao , Gao Ying , Gao Shiming , Shu Chester
Published: March 2011

We propose and experimentally demonstrate simultaneous all‐optical amplification, inversion and format conversion based on self‐induced nonlinear effects in a single semicondctor optcial amplifier. All these functions are verified for injected amplitude‐shift keying signals with variable extinction ratios from 5 to 12 dB. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1320–1323, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26009
Simple printed monopole slot antenna for penta‐band wireless wide area network operation in the mobile handset
Authors: Wong Kin‐Lu , Lin Po‐Wei , Chang Chih‐Hua
Published: March 2011

A simple printed monopole slot antenna for penta‐band wireless wide area network operation (824–960/1710–2170 MHz) in the mobile handset is presented.The monopole slot has a length of 50 mm only and is embedded close to the bottom edge of the system ground plane of the handset with a small distance of 11 mm. By adding a small‐size C‐shaped strip connected orthogonal to the bottom edge of the system ground plane, good excitation of the monopole slot antenna at its fundamental (0.25 wavelength) and higher‐order resonant modes can be obtained. The excited resonant modes form two wide operating bands to cover the GSM850/900 operation (824–960 MHz) and GSM1800/1900/UMTS operation (1710–2170 MHz). Detailed operating principle and radiation characteristics including the specific absorption rate results of the proposed monopole slot antenna are described. Measured results of the fabricated antenna are also presented. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1399–1404, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26017
Novel band‐notched ultra‐wideband elliptical monopole antenna with dual radiating elements
Authors: Jeng Bo‐Ming , Luo Ching‐Hsing
Published: March 2011

A novel ultra‐wideband design of planar elliptical monopole antenna with dual radiating elements is presented. The proposed antenna consists of two elliptical radiating elements and a ground plane. The antenna has a super‐wideband from 2.8 to 15 GHz for voltage standing wave ratio less than 2, except the notched band at 4.8–5.9 GHz for filtering the wireless local area network signal. Based on the contribution of the shorting position d to the notch bandwidth, a particular notch‐band range can be designed by adjusting the size of the minor elliptical radiating element. The radiation pattern of the proposed antenna in the yz‐plane is omni‐directional. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1427–1430, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26023
The Israel lobby, American democracy and foreign perceptions of the USA
Authors: Guerlain Pierre
Published: March 2011

There has been much discussion about the power of the so‐called Israel lobby in the United States. Although the debate has been around for at least three decades the terms of this debate have changed with recent publications. The key questions concerning the so‐called Israel lobby are, first, one of definition —who can be said to belong to or support this lobby, by no means an easy matter which can be solved in ethnic terms—and then one of effectiveness—is US foreign policy in the Middle East shaped by the Israel lobby and is the image of the US in this region of the world and beyond highly correlated with the activities of a domestic pressure group?

Analyzing the activities of the Israel lobby leads one to challenge the concept of a separation between domestic and foreign policy. This paper analyzes how the Israel lobby operates within the context of American democracy and also tackles the issue of foreign perceptions of the US and of an often ill defined Israel lobby. Copyright © 2011 John Wiley & Sons, Ltd.
Flame retardation of glass‐fiber‐reinforced polyamide 6 by combination of aluminum phenylphosphinate with melamine pyrophosphate
Authors: Hu Zhi , Lin Gong‐Peng , Chen Li , Wang Yu‐Zhong
Published: March 2011

The aluminum phenylphosphinate (BPA‐Al) was synthesized and its chemical structure was confirmed by FT‐IR, 1H NMR, and inductively coupled plasma‐atomic emission spectrometry (ICP‐AES). BPA‐Al was used to prepare a series of flame‐retardant glass‐fiber‐reinforced polyamide 6 (GFPA6) composites together with melamine pyrophosphate (MPyP) and sodium tungstate (ST) via melt compounding. The flame retardancy of the composites was investigated by vertical burning test and cone calorimeter test. The thermal behaviors and decomposition kinetics were investigated by thermogravimetric analysis (TGA). BPA‐Al alone could not improve the flame retardancy of GFPA6 composites, but the combination of BPA‐Al and MPyP resulted in a UL‐94 V‐2 rating, and the addition of a small amount of ST to the flame retardant system could endow the composites a V‐0 rating. The flame retardant systems also resulted in a decrease in PHRR and THR in cone calorimeter test. The analysis of thermal decomposition kinetics showed that the activation energies (Eα) of the flame‐retardant composites dramatically decreased compared with that of GFPA6. Copyright © 2011 John Wiley & Sons, Ltd.
Influence of the nanofiller type and content on permeation characteristics of multifunctional NR nanocomposites and their modeling
Authors: Bhattacharya Mithun , Biswas Subharanjan , Bandyopadhyay Srikanta , Bhowmick Anil K.
Published: March 2011

Along with other properties, superior gas permeation behavior would impart an extra dimension to multifunctional natural rubber (NR) nanocomposites used in various applications, like tires. For the first time, the impact on thermodynamics and kinetics of oxygen transport has been evaluated for nano, micro, and dual filler based multifunctional NR nanocomposites through oxygen permeation studies at three different temperatures. It is seen that, the kinetics is less affected by platelet like nanofillers, while the thermodynamics and eventual permeability are not altered much by fibrous nanofillers. The permeability of the nanocomposites decreased in the presence of nanofillers due to high aspect ratio and exquisite dispersion, as ascertained from morphological studies, which caused increment in tortuosity and the reduction in free volume. Relative permeabilities were compared to predictions of existent permeation models and a novel function was successfully introduced to address deviations in a model. Finally, nearly 60% decrement in permeability of dual filler based nanocomposites explained by the formation of zeta potential driven filler associations indicate potency in development of thinner, but stronger and more durable multifunctional materials with longer air retention capabilities. These could be applied in tire research to reduce material, energy costs and increase fuel efficiencies. Copyright © 2011 John Wiley & Sons, Ltd.
Improved polyvinylpyrrolidone (PVP)/graphite nanocomposites by solution compounding and spray drying
Authors: Wang Leilei , Zhang Liqun , Tian Ming
Published: March 2011

In order to evaluate the roles of graphite dispersion on the functional properties of the composites, PVP/graphite nanocomposites were prepared by blending the aqueous suspension of expanded graphite sheets and polyvinylpyrrolidone (PVP) aqueous solution by ultrasonic treatment, followed by spray drying and direct drying as a comparison individually. The effects of graphite loading and drying method on the dispersion of graphite and the resultant properties of the composites such as electrical and thermal conductivity, friction, and dynamic mechanical properties were studied. The results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X‐ray diffraction showed that the composites prepared by fast spray drying exhibited a higher degree of exfoliation and a better dispersion of graphite sheets in the PVP matrix than the corresponding composites prepared by direct drying, leading to a conclusion that fast spray drying can effectively prevent from re‐stacking of the exfoliated graphite sheets as illustrated. As a result, dynamic mechanical thermal analysis showed significant increases in the storage modulus and glass transition temperature for the composites prepared by spray drying. Besides, the spray drying as well greatly improved the electrical and thermal conductivity of the composites. It was also found that the electrical and thermal conductivity of the composites strongly depended on the graphite dispersion, while the friction coefficient unexpectedly does not. Increasing graphite loading level might enhance the probability of graphite sheets re‐stacking, resulting in poor graphite dispersion. Copyright © 2011 John Wiley & Sons, Ltd.
Morphological comparison of isotactic polypropylene parts prepared by micro‐injection molding and conventional injection molding
Authors: Liu Fanghui , Guo Chao , Wu Xian , Qian Xinyuan , Liu Hong , Zhang Jie
Published: March 2011

The morphological feature of microparts evolved during micro‐injection molding may differ from that of the macroparts prepared by conventional injection molding, resulting in specific physical properties. In this study, isotactic polypropylene (iPP) microparts with 200 µm thickness and macroparts with 2000 µm thickness were prepared, and their morphological comparison was investigated by means of polarized light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and wide‐angle X‐ray diffraction (WAXD). The results presented some similarities and differences. PLM observations showed that the through‐the thickness‐morphology of micropart exhibited a similar “skin–core” structure as macropart, but presented a large fraction of shear layer in comparison to the macropart which presented a large fraction of core layer. The SEM observation of shear layer of micropart featured highly oriented shish‐kebab structure. The micropart had a more homogeneous distribution of lamellae thickness. The degree of crystallinity of the micropart was found to be higher than that of the macropart. High content of β‐crystal was found in micropart. The 2D WAXD pattern of the core layer of macropart showed full Debye rings indicating a random orientation, while the arcing of the shear layer indicates a pronounced orientation. The most pronounced arcing of the micropart indicates the most pronounced orientation of iPP chains within lamellae. Copyright © 2011 John Wiley & Sons, Ltd.
Genetic polymorphisms in AURKA and BRCA1 are associated with breast cancer susceptibility in a Chinese Han population
Authors: Ruan Yuan , Song Ai‐Ping , Wang Hui , Xie Yun‐Tao , Han Ji‐Yuan , Sajdik Constantin , Tian Xin‐Xia , Fang Wei‐Gang
Published: March 2011

Centrosome defects can result in aneuploidy and genomic instability, and have important implications for breast cancer development. The Aurora‐A and BRCA1 proteins interact and both are strongly involved in centrosome regulation. Genetic variants in these two genes may have an effect on breast cancer development. Here, we report a comprehensive single nucleotide polymorphism (SNP) and haplotype‐tagging association study on these two genes in 1334 breast cancer cases and 1568 unaffected controls among the Chinese Han population. Apart from a missense SNP, rs2273535 (Phe31Ile), and a probable risk SNP, rs2064863, six htSNPs were analysed in three high‐LD blocks of AURKA spanning from 10 kb upstream to 2 kb downstream of AURKA. For BRCA1, six htSNPs were analysed in a large high‐LD region covering 98 kb (10 kb was extended to each end of BRCA1). The results showed that four SNPs in AURKA (data in recessive model, rs2273535: OR = 2.19, 95% CI = 1.03–4.66, p = 0.0422; rs2298016: OR = 0.38, 95% CI = 0.18–0.82, p = 0.0141; rs6024836: OR = 1.54, 95% CI = 1.18–2.00, p = 0.0014; rs10485805: OR = 0.68, 95% CI = 0.47–0.98, p = 0.0380) and one SNP in BRCA1 (rs3737559, dominant model OR = 1.35, 95% CI = 1.11–1.64, p = 0.0030) were associated with breast cancer susceptibility. After correction for multiple comparisons (FDR = 0.05), only rs6024836 and rs3737559 remained significant. Two haplotypes (CC of block 2, OR = 20.74, 95% CI = 4.35–98.88, p = 0.0001; GG of block 3, OR = 1.32, 95% CI = 1.12–1.56, p = 0.0010) and one diplotype (AG‐GG of block 3, OR = 1.63, 95% CI = 1.18–2.26, p = 0.0031) within AURKA showed strong associations with breast cancer risk. One haplotype of BRCA1 (CTGTTG, OR = 1.30, 95% CI = 1.06–1.59, p = 0.0118) was also associated with breast cancer risk. However, women harbouring both at‐risk genotypes of Aurora‐A and BRCA1 were at a slightly increased risk compared with those harbouring either at‐risk variant alone. Common genetic variants in the AURKA and BRCA1 genes may contribute to breast cancer development. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Using mouse models to investigate the biological and physiological consequences of defects in the Fanconi anaemia/breast cancer DNA repair signalling pathway
Authors: Tischkowitz Marc , Winqvist Robert
Published: March 2011

Fanconi anaemia (FA) is a rare, predominantly autosomal recessive syndrome (with one X‐linked form) that results in congenital defects, abnormal haematopoiesis and a greatly increased risk of solid tumours in humans. Mutations in at least 14 different genes have been shown to cause FA, and several of these genes, including FANCJ/BRIP1, FANCD1/BRCA2 and FANCN/PALB2, also predispose to breast cancer in heterozygote carriers. The FA genes code for proteins that act in complexes to coordinate the repair of damaged DNA, and thus the FA repair network is intimately linked with hereditary breast cancer. Much remains to be learnt about the functions and interactions of the FA proteins and one experimental approach involves the generation of mice that are deficient in various FA genes. Mouse models for FANCN/PALB2 have recently been generated, including one reported in a recent issue of The Journal of Pathology. Given the pivotal role of the PALB2 protein, which interacts with both BRCA1 and BRCA2, these mice provide valuable insights into the FA phenotype and mechanisms of tumourigenesis caused by disruption of the FA protein network. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Down‐regulation of spinophilin in lung tumours contributes to tumourigenesis
Authors: Molina‐Pinelo Sonia , Ferrer Irene , Blanco‐Aparicio Carmen , Peregrino Sandra , Pastor Maria Dolores , Alvarez‐Vega Juan , Suarez Rocio , Verge Mar , Marin Juan J , Hernandez‐Losa Javier , Cajal Santiago Ramon y , Paz‐Ares Luis , Carnero Amancio
Published: March 2011

The scaffold protein spinophilin (Spn, PPP1R9B) is one of the regulatory subunits of phosphatase‐1a (PP1), targeting it to distinct subcellular locations and to its target. Loss of Spn reduces PPP1CA levels, thereby maintaining higher levels of phosphorylated pRb. This effect contributes to an increase in p53 activity. However, in the absence of p53, reduced levels of Spn increase the tumourigenic properties of cells. In addition, Spn knockout mice have a reduced lifespan, an increased number of tumours and increased cellular proliferation in some tissues, such as the mammary ducts. In addition, the combined loss of Spn and p53 activity leads to an increase in mammary carcinomas, confirming the functional relationship between p53 and Spn. In this paper, we report that Spn is absent in 20% and reduced in another 37% of human lung tumours. Spn reduction correlates with malignant grade. Furthermore, the loss of Spn also correlates with p53 mutations. Analysis of miRNAs in a series of lung tumours showed that miRNA106a* targeting Spn is over‐expressed in some patients, correlating with decreased Spn levels. Proof‐of‐concept experiments over‐expressing miRNA106a* or Spn shRNA in lung tumour cells showed increased tumourigenicity. In conclusion, our data showed that miRNA106a* over‐expression found in lung tumours might contribute to tumourigenesis through Spn down‐regulation in the absence of p53. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Plasma Deposited Electrocatalytic Films with Controlled Content of Pt Nanoclusters
Authors: Dilonardo Elena , Milella Antonella , Cosma Pinalysa , d'Agostino Riccardo , Palumbo Fabio
Published: March 2011

Combining platinum sputtering with plasma polymerization in argon–ethylene plasmas, nanocomposite Pt‐hydrocarbon thin films, useful as catalytic layers for proton exchange membrane fuel cells, can be deposited. Pulsing the ethylene flow rate allowed for a fine tuning of the Pt amount in deposited films at low RF input power. The proposed deposition process seems to be an efficient strategy to control the metal content over a wide range of atomic percentages (5–80%). Deposited films were characterized in terms of their chemical, electrochemical and structural properties. The XPS spectra revealed that platinum is included in the films in metallic state. SEM and TEM analyses showed that nanosized Pt clusters (3–7 nm diameter) are uniformly distributed in a porous columnar film structure. The best electrochemical activity (202 cm2 · mg) was achieved with a 500 nm thick thin film containing 0.56 mgPt · cm−2 of catalyst.

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Leukocyte integrin αLβ2 transmembrane association dynamics revealed by coarse‐grained molecular dynamics simulations
Authors: Chng Choon‐Peng , Tan Suet‐Mien
Published: March 2011

Integrins are transmembrane (TM) proteins that mediate bidirectional mechanical signaling between the extracellular matrix and the cellular cytoskeletal network. Each integrin molecule consists of non‐covalently associated α‐ and β‐subunits, with each subunit consisting of a large ectodomain, a single‐pass TM helix, and a short cytoplasmic tail. Previously we found evidence for a polar interaction (hydrogen bond) in the outer membrane clasp (OMC) of the leukocyte integrin αLβ2 TMs that is absent in the platelet integrin αIIβ3 OMC. Here, we compare the self‐assembly dynamics of αLβ2 and αIIβ3 TM helices in a model membrane using coarse‐grained molecular dynamics simulations. We found that although αIIβ3 TM helices associate more easily, packing is suboptimal. In contrast, αLβ2 TM helices achieve close‐to‐optimal packing. This suggests that αLβ2 TM packing is more specific, possibly due to the interhelix hydrogen bond. Theoretical association free energy profiles show a deeper minimum at a smaller helix‐helix separation for αLβ2 compared with αIIβ3. The αIIβ3 profile is also more rugged with energetic barriers whereas that of αLβ2 is almost without barriers. Disruption of the interhelix hydrogen bond in αLβ2 via the β2T686G mutation results in poorer association and a similar profile as αIIβ3. The OMC polar interaction in αLβ2 thus plays a significant role in the packing of the TM helices. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Observing the osmophobic effect in action at the single molecule level
Authors: Aioanei Daniel , Tessari Isabella , Bubacco Luigi , Samorì Bruno , Brucale Marco
Published: March 2011

Protecting osmolytes are widespread small organic molecules able to stabilize the folded state of most proteins against various denaturing stresses in vivo. The osmophobic model explains thermodynamically their action through a preferential exclusion of the osmolyte molecules from the protein surface, thus favoring the formation of intrapeptide hydrogen bonds. Few works addressed the influence of protecting osmolytes on the protein unfolding transition state and kinetics. Among those, previous single molecule force spectroscopy experiments evidenced a complexation of the protecting osmolyte molecules at the unfolding transition state of the protein, in apparent contradiction with the osmophobic nature of the protein backbone. We present single‐molecule evidence that glycerol, which is a ubiquitous protecting osmolyte, stabilizes a globular protein against mechanical unfolding without binding into its unfolding transition state structure. We show experimentally that glycerol does not change the position of the unfolding transition state as projected onto the mechanical reaction coordinate. Moreover, we compute theoretically the projection of the unfolding transition state onto two other common reaction coordinates, that is, the number of native peptide bonds and the weighted number of native contacts. To that end, we augment an analytic Ising‐like protein model with support for group‐transfer free energies. Using this model, we find again that the position of the unfolding transition state does not change in the presence of glycerol, giving further support to the conclusions based on the single‐molecule experiments. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Anomalous temperature and interfacial‐coupling dependence of exchange bias in antiferromagnetic (core)/ferromagnetic (shell) nanoparticles
Authors: Hu Yong , Du An
Published: March 2011

In a single composite ferromagnetic/antiferromagnetic (AFM) nanoparticle with an unconventional core/shell morphology, the effects of temperature and interfacial coupling on the exchange bias (EB) are studied by performing a modified Monte Carlo method. With the decrease of temperature, three distinct behaviors of the EB are obtained as a result of the state transitions of the AFM spins from completely free via partially free and partially frozen, and, finally, to completely frozen. The behaviors of the coercivity are nonmonotonic due to the energy competitions and the thermal fluctuations. Moreover, the cooling field affects strongly the low‐temperature behaviors of the EB. The EB field obtained after field cooling is negative and almost constant, independent of the interfacial coupling. However, after zero‐field cooling, the EB field may exhibit a sign‐reversal behavior with increasing interfacial coupling at low temperature. On the basis of the theory of the surplus magnetization, it is revealed that the drastic temperature dependence and the energy competition mechanism at the interface in the cooling process are responsible for this unique property in such novel nanostructures.
A PRESUMPTIVE STANDARD FOR ENVIRONMENTAL FLOW PROTECTION
Authors: Richter B. D. , Davis M. M. , Apse C. , Konrad C.
Published: March 2011

The vast majority of the world's rivers are now being tapped for their water supplies, yet only a tiny fraction of these rivers are protected by any sort of environmental flow standard. While important advances have been made in reducing the cost and time required to determine the environmental flow needs of both individual rivers and types of rivers in specific geographies, it is highly unlikely that such approaches will be applied to all, or even most, rivers within the forseeable future. As a result, the vast majority of the planet's rivers remain vulnerable to exploitation without limits. Clearly, there is great need for adoption of a “presumptive standard” that can fill this gap. In this paper we present such a presumptive standard, based on the Sustainability Boundary Approach of Richter (2009) which involves restricting hydrologic alterations to within a percentage‐based range around natural or historic flow variability. We also discuss water management implications in applying our standard. Our presumptive standard is intended for application only where detailed scientific assessments of environmental flow needs cannot be undertaken in the near term. Copyright © 2011 John Wiley & Sons, Ltd.
MACROINVERTEBRATES IN ABANDONED CHANNELS: ASSEMBLAGE CHARACTERISTICS AND THEIR INDICATIONS FOR CHANNEL MANAGEMENT
Authors: Pan B.‐Z. , Wang Z.‐Y. , Xu M.‐Z.
Published: March 2011

Alluvial floodplains contain four types of abandoned channels: old river courses, oxbow lakes, oxtail lakes and riparian wetlands. These result from avulsions, meander cutoffs, ice‐jam floods and stem‐channel shifts, respectively. With the exception of old river courses, which belong to terrestrial ecosystems, abandoned‐channel types are important components of freshwater ecosystems. During 2006–2009, we conducted systematic investigations of macroinvertebrates in three types of freshwater abandoned channels and identified 93 taxa of macroinvertebrates belonging to 51 families and 88 genera. In the assemblage composition, most taxa were similar to those found in river‐isolated lakes and river mainstreams. Moreover, abandoned channels supported many unique benthic taxa, which are important complementary resources for the entire river system. In the abandoned channels that were covered with a layer of silt, standing crops were higher than that found in the river mainstream where the bed sediment consisted mainly of sand. Conversely, in abandoned channels that were covered with fine sand, standing crops were lower than in the gravel streambed. Some abandoned channels, such as the riparian wetlands of the East River that are freely connected with the mainstream, were characterized by the highest biodiversity and the greatest biomass. In regions less affected by human activities, abandoned channels need to be connected with mainstreams by flooding at least once every 3 years to maintain at least half of the maximum amount of macroinvertebrate resources. In regions more affected by human activities, abandoned channels need to be connected with mainstreams at least once every year. Copyright © 2011 John Wiley & Sons, Ltd.
Application of Cr Kα X‐ray photoelectron spectroscopy system to overlayer thickness determination
Authors: Kobata Masaaki , Píš Igor , Nohira Hiroshi , Iwai Hideo , Kobayashi Keisuke
Published: March 2011

A laboratory hard X‐ray photoelectron spectroscopy (HXPS) system at 5.4‐keV excitation energy was used to measure the angle dependence of a silicon oxide overlayer on a Si(0 0 1) substrate with overlayer thickness ranging from 4 to 25 nm. The thickness values of the SiO2 overlayers were determined by utilizing a focused monochromatized Cr Kα source and a high‐energy hemispherical analyzer with an angle‐resolved wide acceptance angle objective lens. The modulation of the photoemission intensity due to photoelectron diffraction, which deteriorates high‐precision thickness determination, was suppressed significantly by continuous sample rotation around the sample's normal during the measurements. The resultant thickness values very well agree with those determined by ellipsometry in the same sample set. To demonstrate merits of the large information depth measurements, profiling of a wedged SiO2 layer buried in a gate stack model structure with Ir (8 nm) and HfO2 (2 nm) overlayers was performed. Copyright © 2011 John Wiley & Sons, Ltd.
Response modeling methodology
Authors: Shore Haim
Published: March 2011

Response modeling methodology (RMM) is a general platform for modeling monotone convex relationships. Unique to RMM models is their ‘continuous convexity’ property, which allows the data to ‘select’ the final form of the model via the estimated parameters (analogously with the Box–Cox transformation). This renders RMM a versatile and effective platform for empirical modeling of random variation (‘distribution fitting’) and of systematic variation (‘relational modeling’). In this overview, we detail the motivation that led to the development of RMM, explain RMM core concepts, and introduce RMM basic model and variations. Allied maximum‐likelihood estimation procedures are detailed, separately for models of random variation and for models of systematic variation. Numerical examples demonstrate RMM effectiveness in comparison to other current approaches. Current literature on RMM (about 25 publications), available software, and ongoing research are also addressed. WIREs Comp Stat 2011 3 357–372 DOI: 10.1002/wics.151

This article is categorized under:

Statistical and Graphical Methods of Data Analysis > Density Estimation

Statistical Learning and Exploratory Methods of the Data Sciences > Modeling Methods

Statistical and Graphical Methods of Data Analysis > Modeling Methods and Algorithms

Algorithms and Computational Methods > Maximum Likelihood Methods
PIXE simulation in Geant4
Authors: Mantero A. , Ben Abdelouahed H. , Champion C. , El Bitar Z. , Francis Z. , Guèye P. , Incerti S. , Ivanchenko V. , Maire M.
Published: March 2011

Geant4 is a general purpose and open source C + + Monte Carlo simulation toolkit, widely used in the scientific community. It is able to simulate physical interactions of particles through matter. According to the user's needs, models for the simulation of electromagnetic (EM) interactions are provided in two Geant4 subpackages, the ‘standard’ EM subpackage, well suited for a wide range of applications and the ‘low‐energy’ EM subpackage, able to reach the electronVolt regime. Particle‐induced X‐ray emission (PIXE) is a well known and a very useful technique for quantitative elemental analysis in environmental, archaeological, biological, medical and space applications. An atomic de‐excitation module is part of the Geant4 ‘low‐energy’ EM subpackage since 1999 and has been validated in recent years. PIXE simulation has been included in this subpackage in 2001 and new ionisation cross‐sectional models following the ECPSSR theory have been added for the PIXE simulation in 2008. In 2010, these models have been further extended to higher energies. In this work, we present new results on the verification of these models and an overview of the new interface to PIXE modelling prepared for the recent public release of the Geant4 toolkit (December 2010) allowing a unified usage of the Geant4 de‐excitation module by both ‘standard’ and ‘low‐energy’ subpackages. Copyright © 2011 John Wiley & Sons, Ltd.
In vivo 3D imaging of Drosophila melanogaster using PIXE‐micron‐CT
Authors: Ohkura S. , Ishii K. , Matsuyama S. , Terakawa A. , Kikuchi Y. , Kawamura Y. , Catella G. , Hashimoto Y. , Fujikawa M. , Hamada N. , Fujiki K. , Hatori E. , Yamazaki H.
Published: March 2011

Characteristic X‐rays from a pure metal target bombarded with a few MeV proton micro‐beams can be used as a point source of quasi‐monochromatic X‐rays. On the basis of this idea, we have previously developed a microscopic computed tomography (CT) which we called particle induced X‐ray emission (PIXE)‐micron‐CT. We applied our CT to observe organs in a body of a living Drosophila, which is popularly used in various fundamental studies, such as gene research. We optimized the beam spot size of proton micro‐beam, redesigned the geometry of the PIXE‐micron‐CT and improved the sample preparation method. As a result of these efforts, the CT scan time could be reduced to less than a sixth of its previous value without degrading the spatial resolution. Three‐dimensional (3D) images of a living Drosophila in different growth stages were obtained. The forms of organs changed significantly depending on the growth stage. The CT images of living Drosophila were much different from those of dead or formalin fixed ones. The in vivo 3D imaging by PIXE‐micron‐CT is very useful and is one of the powerful tool in biological and medical studies. Copyright © 2011 John Wiley & Sons, Ltd.
Micro‐PIXE studies of Ni‐elimination strategies in representatives of two families of beetles feeding on Ni‐hyperaccumulating plant Berkheya coddii
Authors: Migula P. , Przybyłowicz W. J. , Nakonieczny M. , Augustyniak M. , Tarnawska M. , Mesjasz‐Przybyłowicz J.
Published: March 2011

Plants may use the ability to hyperaccumulate toxic metals in their defence against herbivores. Insects can counteract and feed on toxic plants. Among grazers of Ni‐hyperaccumulating Berkheya coddii, some beetles tolerate Ni (Chrysolina clathrata, former name Chrysolina pardalina; Epilachna nylanderi). The adaptive mechanisms against Ni toxicity were studied in these species using micro‐PIXE quantitative elemental mapping and by microscopy techniques. Distinct differences were found in mechanisms used for Ni‐elimination in both species. Functional comparisons and quantification of data extracted from selected micro‐areas in target organs responsible for metal circulation (digestive tract and Malpighian tubules) were made. Similar detoxification mechanism is used against metals through spheric granules, which in E. nylanderi are formed mainly in the midgut, while in C. clathrata in Malpighian tubules and midgut. Elemental maps showed positive correlations of Ni and Zn in Malpighian tubules of E. nylanderi without such effect in C. clathrata. Quantitative relations of K+ and Cl− indicate higher osmotic pressure increasing reabsorption of water necessary for Ni transportation to the intestine lumen and further rejection outside the body. Copyright © 2011 John Wiley & Sons, Ltd.
Infinite-dimensional stochastic differential equations related to random matrices
Authors: Osada Hirofumi
Published: March 2011

We solve infinite-dimensional stochastic differential equations (ISDEs) describing an infinite number of Brownian particles interacting via two-dimensional Coulomb potentials. The equilibrium states of the associated unlabeled stochastic dynamics are the Ginibre random point field and Dyson’s measures, which appear in random matrix theory. To solve the ISDEs we establish an integration by parts formula for these measures. Because the long-range effect of two-dimensional Coulomb potentials is quite strong, the properties of Brownian particles interacting with two-dimensional Coulomb potentials are remarkably different from those of Brownian particles interacting with Ruelle’s class interaction potentials. As an example, we prove that the interacting Brownian particles associated with the Ginibre random point field satisfy plural ISDEs.
Effect of Stipa tenacissima L. on the structure of plant co‐occurrence networks in a semi‐arid community
Authors: Saiz Hugo , Alados Concepción L.
Published: March 2011

Network approaches can increase our understanding of both changes in ecosystems and the role that individual species play in such changes. In ecology, networks have been applied mainly to the study of food webs and mutualistic interactions, with few studies on plant communities. This study used a network approach to examine a semi‐arid plant community along a Stipa tenacissima abundance gradient at two locations in SE Spain: (1) an open shrub land where S. tenacissima is a highly competitive species, and (2) an alpha steppe where S. tenacissima forms the end stable successional community. In alpha steppe, the influence of slope was also examined. We detected that S. tenacissima influenced the network structuring process, and that network organization changed along the gradient. In open shrub land, when S. tenacissima became abundant, it dominated the community and other species disappeared. This resulted in a reduction of the number of links that S. tenacissima established. At the alpha‐steppe, S. tenacissima coexists with other species, developing more links as it becomes more abundant. On gentle slope zones of alpha steppe, S. tenacissima is more competitive and becomes dominant for high abundance values, reducing its links with other species. The organization of networks varied similarly in both locations. When plant species reduce their abundance and number, links are more heterogeneously distributed in networks. This leads to a concentration of most of the links around a few species, particularly S. tenacissima, which is the most abundant in this case. We conclude that, in order to study plant communities, it is convenient to consider the properties of individual components together with the interaction between them.