bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed Systems Robust to Hand Loading Based on Nonresonant Elements
Authors: Andujar Aurora , Anguera Jaume , Cobo Yolanda
Published: July 2013

Miniature and multiband internal antenna systems are strongly required in emergent multifunction wireless devices. Recent techniques are focused on properly exciting ground plane radiation modes through nonresonant elements. These solutions remove the need of including quarter‐wavelength resonant antennas featured by a considerable size. Nevertheless, in this new scenario, the complexity moves toward not only the reduction of the size of the elements used to excite the ground plane mode but also to the simplification of the radiofrequency system used to attain impedance matching. This article proposes the use of distributed systems based on nonresonant elements for solving the bandwidth and efficiency limitations of previous solutions while adding robustness to hand loading effects. Two different feeding schemes, an in‐phase and an out‐of‐phase feeding scheme are simulated, measured, and compared in free‐space as well as regarding the presence of a phantom hand. The proposal provides octo‐band operation and attains a radiating system robust to hand loading effects capable of properly operating in nine communication standards, LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2100, LTE2300, and LTE2500. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2307–2317, 2013
A 3.1–10.6‐GHz Current‐Reused CMOS Ultra‐Wideband Low‐Noise Amplifier Using Self‐Forward Body Bias and Forward Combining Techniques
Authors: Wu Chia‐Hsing , Lin Yo‐Sheng , Wang Chien‐Chin
Published: July 2013

A 3.1–10.6‐GHz ultra‐wideband low‐noise amplifier (UWB LNA) with excellent phase linearity property (group‐delay variation is only ±19.46 ps across the whole band) using standard 0.18‐µm CMOS technology is reported. Current reused, self‐forward body bias and forward combining techniques are used to achieve low power and high‐power gain (S21). Both high and flat S21 and low and flat noise figure (NF) frequency responses are achieved by tuning the pole frequencies and pole quality factors of the second‐order gain and NF frequency responses to approximate the maximally flat condition simultaneously. The LNA dissipates 6.93‐mW power and achieves NF of 3.76 at 10 GHz. In addition, the LNA achieves input return loss (S11) smaller than −10.6 dB, and high and flat S21 of 11.02 ± 0.47 dB over the 3.1–10.6‐GHz band. The corresponding figure of merit (FOM) is 3.11 GHz/mW, one of the lowest FOMs ever reported for a 3.1–10.6 GHz CMOS UWB LNA. The measured input third‐order intermodulation point (IIP3) is −3.6 dBm at 6 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2296–2302, 2013
Broadband Printed Directional Bow‐Tie Antenna for the 500–1600‐MHz Band
Authors: Cacciatori Alessio , Modotto Daniele , Boscolo Stefano , Midrio Michele , Locatelli Andrea , De Angelis Costantino , Kovács‐Vajna Zsolt M.
Published: July 2013

A bow‐tie antenna, suitable for through‐wall radars working in the 500–1600‐MHz band, is designed, fabricated, and measured. The proposed printed antenna and its ground plane based reflector can be readily integrated in a circuit board. A thorough characterization of the prototype confirms the numerically calculated radiation patterns. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2329–2333, 2013
Graphene in Layered Medium Applications
Authors: Simsek Ergun
Published: July 2013

Graphene can be defined either as an infinitely thin material with an optical conductivity or as a thin layer with a finite thickness and an effective complex electrical permittivity. Layered medium Green's functions are calculated according to these two definitions for multilayered structures including a graphene layer. It is found that numerical methods show a good agreement especially in the far field. Moreover, finite thickness method requires significantly less computation time than the effective complex permittivity method. Thus, considering the computation time and accuracy, the finite thickness approach is a better alternative to analyze the electromagnetic wave propagation and scattering in multilayered media with a graphene layer. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2293–2296, 2013
Phase‐Locked Homodyne Measurement of Quasiprobability Q Function and Detection of Information‐Carrying Weak‐Coherent States
Authors: Garcia Edith , Mendieta Francisco J. , Lopez Josue A. , Alvarez Eduardo , Arvizu Arturo , Gallion Philippe
Published: July 2013

We present an eight‐port homodyne receiver implemented in free space technology for detection of weak coherent states that carry binary information. For transmitted power economy, we use suppressed‐carrier modulation, therefore, we have implemented an optical Costas‐loop‐type carrier synchronizer. We obtain the quasiprobability Q function from the in‐phase and quadrature observables that are simultaneously measured. Statistical results for the quadrature components are presented. We perform measurements for the bit error rate and the mutual information between transmitter–receiver. The results show that the proposed setup is suitable in quantum communications and continuous variable quantum key distribution systems. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2431–2437, 2013
Compact and High Selectivity Cross‐Coupled Broadband Microstrip Bandpass Filter
Authors: Deng Hong‐wei , Zhao Yong‐jiu , Fu Yong , He Ying , Gao Si‐ping
Published: July 2013

In this article, a new compact and high selectivity broadband microstrip bandpass filter (BPF) is proposed using one folded half‐wavelength resonator (FHWR) in the middle and two quarter‐wavelength resonators (QWRs). Due to the cross coupling between the source/load and FHWR, four transmission zeros can be created in the lower‐ and upper‐stopband. The transmission zero generated by the coupling between the QWR and parallel‐coupling feedline can sharpen the skirt and suppress the first harmonic of the FHWR. To verify the design concept, a microstrip BPF with 1‐dB fractional bandwidth (FBW) of 61% centered at 3 GHz is designed and fabricated. Measured results show low insertion loss and flat group delay in the entire passband as well as high out‐band rejection. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2501–2504, 2013
Small Size Antenna Based on Metamaterial Split‐Ring Resonators
Authors: Jimenez‐Guzman Gabriel Angel , Tirado‐Mendez Jose Alfredo , Pena‐Rivero Raul
Published: July 2013

In this work, a reduced size planarized antenna based on metamaterial split‐ring resonators (SRRs), for personal communications, is presented. The antenna is based on different size concentric SRRs that operates in the R band, centered at 2.3 GHz. The antenna area is about 15 × 25 mm2, approximately. The measured antenna gain is around −3 dB, with an omnidirectional pattern, and the measured bandwidth is about 1 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2345–2350, 2013
Compact Slot Antenna for Mimo Applications in the Wlan Bands
Authors: Naser‐Moghadasi M. , Danideh A. , Bakhtiari A. , Sadeghifakhr R.
Published: July 2013

A rectangular slot antenna fed by a coplanar waveguide is proposed for dual‐band wireless local area network (WLAN) operations. The measured −10‐dB bandwidth for return loss is from 2.1 to 2.95 GHz and 5.05 to 6.25 GHz, covering all the 2.4/5‐GHz WLAN bands. A multifeed four‐element planar array was designed and simulated. It shows that the features of small size, uniplanar structure, good radiation characteristics, and small mutual coupling are promising for multi‐input multi‐output applications. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2490–2493, 2013
Compact Double Band‐Notched Antenna with Nonequiwidth W‐Shaped Slot and “6”‐Shaped Resonance Loop for UWB Applications
Authors: Yang Tang , Song Gao Jin , Song Wang Yan , Guo Feng Xiao
Published: July 2013

In this article, a novel compact double band‐notched antenna with nonequiwidth W‐shaped slot and “6”‐shaped resonance loop on the two sides of the feed line is proposed, which consists of a cone‐shaped monopole patch with nonequiwidth W‐shaped slot and “6”‐shaped resonance loop on the two sides of the feed line, the metal earth‐plate with step slot is designed on other side of the substrate. The simulated and experimental results demonstrate that the proposed antenna can obtain the double band‐notched feature within the bandwidth of 3.3–3.8 GHz and 5.0–6.0 GHz, the impedance bandwidth can achieve from 2.4 to 11.6 GHz (VSWR < 2),which is more than 131%. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2405–2410, 2013
A Compact ACS‐FED Dual‐Band Meandered Monopole Antenna for Wlan and WiMax Applications
Authors: Li Yingsong , Li Wenxing , Mittra Raj
Published: July 2013

In this article, we present the design of a dual‐band (3.5 and 5.8 GHz), meandered monopole antenna for Wireless Local Area Network (WLAN)/Worldwide Interoperability for Microwave Access (WiMAX) applications, which is fed by an asymmetric coplanar strip (ACS). The proposed antenna is comprised of an asymmetric ground plane, an ACS‐fed structure, and coupled meandered monopole‐type of radiating elements that are designed to provide the two desired operation bands, namely 3.5 and 5.8 GHz. The two resonance frequencies of the antenna can be controlled by adjusting the dimensions of the radiating elements, namely the two meandered monopoles, and the gap between them which controls the coupling. The designed antenna has a small size, which is only 20 × 12 mm2 including the ground plane. Simulated and measured results are presented to demonstrate that the proposed dual‐band antenna is well suited for WLAN and WiMAX applications. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2370–2373, 2013
An Approach for Determining Equivalent Circuit Model of On‐Chip Inductors
Authors: Yan Na , Yang Chen , Gao Jianjun
Published: July 2013

A parameter‐extraction approach for the spiral on‐chip inductors, which combines the analytical approach and the empirical optimization procedure, is developed in this article. The model parameters determined from the analytical expressions are considered as an initial guess of a subsequent optimization procedure leading to the final model parameters. Scaling rule for the inductances of spiral on‐chip inductors has been developed, and very useful for predicting the performance of the on‐chip inductors with larger size. Good agreement is obtained between simulated and measured results for the spiral inductors with different size on silicon in the frequency range of 500 MHz–40 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2363–2370, 2013
Prediction of Transmission Path Loss in Indoor Environments with The Radiosity Method
Authors: Mouhtaropoulos Dimitris , Boursianis Achilles , Samaras Theodoros
Published: July 2013

In this work, we present the implementation of the radiosity method for path loss prediction inside indoor environments. We demonstrate its accuracy and computational efficiency by comparing our calculations to the results obtained with measurements and a full wave solution. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2401–2405, 2013
Multiresonance Monopole Antenna with Band‐Stop Performance
Authors: Ojaroudi Mohammad , Ojaroudi Nasser , Ghadimi Noradin
Published: July 2013

In this article, we present an ultrawideband (UWB) monopole antenna with band‐stop performance. By cutting a vertical rectangular slot in the ground plane and also by inserting a pair of horizontal rectangular slots extra resonances at higher frequencies can be achieved and provide a wide usable fractional bandwidth of more than 150%. A pair of Γ‐shaped strips protruded in the square radiating patch, were applied to generate a band‐notched performance in wireless local area network (WLAN) frequency range. The presented monopole antenna can operate from 2.74 to 16.02 GHz with VSWR < 2, and with a rejection band around of 4.96 to 5.91 GHz to avoid interferences from WLAN Communication systems. Simulated and experimental results obtained for the proposed antenna is suitable for UWB applications. Compact size, wide bandwidth and omnidirectional radiation pattern are of the other features of this antenna. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2398–2401, 2013
Reduction of Mutual Coupling Between PIFA Antennas for Dual‐Band WiMAX Operations
Authors: Zhai Huiqing , Ma Zhihui , Li Zhenhua , Liang Changhong
Published: July 2013

In this article, a simple and efficient approach is proposed to reduce the mutual coupling between two dual‐band planar inverted‐F antennas. The present isolation structures including one defected ground structure and two “F”‐type strips are introduced to effectively reduce the mutual coupling for two worldwide interoperability for microwave access/2.5 GHz/3.5 GHz bands. By the present method, at least 6 dB reductions of mutual couplings for the two working frequency bands have been obtained, which are verified by measurement results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2321–2324, 2013
Study on Curved Wedge Diffraction in NURBS‐UTD Method
Authors: Wang Nan , Dang Xiao‐jie , Yuan Hao‐bo , Liang Chang‐Hong
Published: July 2013

The curved wedge diffraction in nonuniform rational b‐spline (NURBS)‐uniform geometrical theory of diffraction method is studied in this article. The curved wedge is denoted as a NURBS curve while it is also treated as the intersection of two NURBS surfaces. Basic aspects are managed through numerical measures, and parameters used in the calculation of ray field are achieved by using the mathematic definition of NURBS and basic knowledge of differential geometry. Good results are achieved in the examples given and with the contribution of the wedge diffracted ray field to the total ray field, the computational accuracy can be slightly improved. Numerical results show the validation and the improvement. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2317–2321, 2013
Theoretical and Experimental Studies on Characteristics of An Equilateral Triangular Patch Antenna with and Without Variable Air Gaps
Authors: Biswas Manotosh , Dam Mihir
Published: July 2013

In this article, we present a simple, fast, and accurate CAD oriented cavity model to predict accurately the resonant frequency, input impedance, bandwidth, efficiency, and gain of an equilateral triangular patch antenna with and without air gap in between substrate and ground plane. The present model shows very close agreement with the previously reported experiments for a wide range of antenna parameters and feed locations compared to the other models. The experimental values of input impedance, bandwidth, efficiency, and gain with air gap are not available in open literature. So, we have performed a set of experiments to validate the present model with air gap. The present model without air gap for different substrate parameters are also validated with our own experiments. The accuracy of the present model is calculated with respect to the HFSS computation and experimental results. This model will be very useful for designing the MIC on semiconductor materials with εr > 10 and directly applied in portable wireless equipments. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2271–2277, 2013
Novel Ultra‐Wideband Filter Using Coplanar‐Waveguide‐To‐Microstrip Transition and Stubs
Authors: Sun Xiaofeng , Tan Eng Leong
Published: July 2013

This letter presents a novel ultra‐wideband (UWB) filter using coplanar‐waveguide (CPW)‐to‐microstrip transition and stubs. The proposed filter is implemented by the CPW series stubs and microstrip shunt stubs. The transition includes a via that not only connects the series and shunt stubs but also can improve the out‐of‐band rejection. The proposed filter has been analyzed, verified, and fabricated. Both simulation and measurement results demonstrate the higher rejection cutoff frequencies above 18 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2269–2271, 2013
A Compact Dual‐Passband Filter Using Stepped‐Impedance Resonators
Authors: Tsai Lin‐Chuan
Published: July 2013

In this letter, a new coupling configuration of the stepped‐impedance resonator (SIR) has been presented to design dual‐passband filters with the small circuit size. We design the filter with higher selectivity based on SIR direct‐coupling, input, and output external quality factors. Through resonance characteristics of a SIR, the second resonant frequency can be tuned by adjusting structure parameters. The agreement between measured results and full‐wave simulation prediction validates the feasible configuration of the proposed filters. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2514–2517, 2013
Design of an Integrated Lens for Separating Microwave and Optical Wave
Authors: Che Rongrong , Yi Zixuan , Zhu Qi , Xin Hao
Published: July 2013

In this article, we proposed a design of an integrated lens, which is composed of an optical Fresnel lens (OFL) and a microwave Fresnel zone plate lens (MFZPL). The MFZPL is constructed by a helices array. The OFL focuses the light wave whereas the MFZPL focuses microwave. Both, simulations and experimental results show that microwave and light wave can be converged in their respective focal regions. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2358–2363, 2013
Design of a Ka‐Band Microstrip Antenna Array with Sharped‐Beam Pattern and High Gain
Authors: Wu Yiwei , Zhu Qi
Published: July 2013

A Ka‐band microstrip array antenna is presented in this article. It operates at 35.1 GHz and can realize sharped‐beam pattern and high gain. The antenna array consisting of 14 ×8 elements is fabricated on Rogers RT5880 substrate with 0.254‐mm thickness. It is center‐fed by a coax probe, and the symmetrical feed network is two‐stage cascaded with unequal amplitudes and the same phase. The total size of the array is 110 ×67 mm2. The simulated and test results show that the antenna array has a gain of 25 dB, the 3 dB beamwidths in azimuth, and elevation plane are less than 6° and 10° respectively, the sub lobe suppression is −18 dB. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2517–2520, 2013
All‐Fiber Dual‐Wavelength Thulium–Bismuth Codoped Fiber Laser
Authors: Saidin N. , Zen D. I. M. , Damanhuri S. S. A. , Harun S. W. , Ahmad H. , Dimyati K. , Halder A. , Paul M. C. , Pal M. , Bhadra S. K.
Published: July 2013

We report a room temperature all‐fiber dual‐wavelength Thulium–Bismuth codoped fiber laser operating in 1900 nm region using a single fiber Bragg grating (FBG) in a ring configuration. The addition of Bismuth ions as codopant in the gain medium enhances the inhomogeneous broadening effect in the fiber and thus allows a dual‐wavelength oscillation with the assistance of the FBG that has a flat top reflection spectrum. By pumping the gain medium with 1552 nm laser, a dual‐wavelength output lines are obtained at 1901.09 and 1901.98 nm with a spacing of 0.89 nm and an optical signal to noise ratio of more than 45 dB as the polarization controller (PC) orientation is adjusted to balance the loss between the two wavelengths. The dual‐wavelength laser can also be switched to operate in single‐wavelength at either 1901.07 or 1901.98 nm by altering the intracavity polarization using the PC. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2324–2326, 2013
A Practical Approach: Design of Wideband Cylindrical Dielectric Resonator Antenna With Permittivity Variation in Axial Direction and its Fabrication Using Microwave Laminates
Authors: Chaudhary Raghvendra Kumar , Srivastava Kumar Vaibhav , Biswas Animesh
Published: July 2013

In this article, a practical approach for designing the cylindrical dielectric resonator antenna (CDRA) with permittivity variation in axial direction has been proposed for wideband application. The parametric analysis is performed for designing of homogeneous, two‐layer, three‐layer, and four‐layer multilayer multipermittivity (MLMP) CDRA operating at HE11δ mode. The effect of antenna parameters, such as the aspect ratio, layers' arrangement, layers' thickness, layers' permittivity, and probe length are investigated. Simulation study shows that if the layers are arranged in ascending order of their permittivities from bottom to top, the bandwidth can be improved significantly with broadside radiation patterns and low cross‐polarization levels. The detailed design guidelines are discussed for homogeneous, two‐layer, three‐layer, and four‐layer MLMP CDRA in separate sections. A prototype of three‐layer MLMP CDRA is fabricated using commercially available microwave laminates and experimentally verified for input reflection coefficient, radiation pattern, and gain profile. The good agreements between simulation and measured results have been observed. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2282–2288, 2013
Design of Compact High‐Gain Dielectric Rod Antennas and Arrays in Lossy Medium
Authors: Chen Panpan , Meng Ru , Zhu Qi
Published: July 2013

In this article, compact dielectric rod antennas with relatively high gain are presented, which are fit for use in lossy medium. A quasi‐monopole and a bifilar helix are used to simplify the feeding structure and guarantee high gain. Furthermore, antenna arrays with high gain and low side‐lobe levels are considered. Lower side‐lobe levels are achieved by lossy medium. Then, a C‐band dielectric rod antenna fed by a quasi‐monopole is designed and fabricated, and a Ku‐band antenna array, composed of four dielectric rod antennas fed by a bifilar helix is also displayed. Simulated results illustrate that the gains of the antenna are 9.53 dB and −0.29 dB in free space and in lossy medium, respectively, whereas the gain of the array is 12.2 dB with the side‐lobe level lower than 14 dB. The measured results of the antenna coincide with the simulated results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2277–2282, 2013
A Frequency Agile, Ultralow‐Profile, Complementary Split Ring Resonator‐Based Electrically Small Antenna
Authors: Tang Ming‐Chun , Ziolkowski Richard W.
Published: July 2013

The frequency agility of an electrically small, ultralow‐profile, VHF‐UHF antenna, which has evolved from a complementary split ring resonator unit cell design, is studied numerically. Simulation results demonstrate that when a varactor is integrated into the original 300‐MHz passive antenna and its capacitance is varied linearly from 0 to 5.8 pF, a tuning ratio of 2.02:1 and an effective fractional bandwidth of 67.6% (approximately 679.74 times the original value) is achieved while maintaining |S11| < −10dB (VSWR < 2), and a stable dipolar directivity pattern over the entire bandwidth. The overall dimensions of the proposed antenna at the maximum frequency fmax = c/λmin are 0.03(λmin)2 × 0.0066λmin. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2425–2428, 2013
A New Slot Antenna with Triple Stop‐Band Performance for UWB Applications
Authors: Akbari Mohammad
Published: July 2013

In this article, various methods for designing a slot antenna with triple band‐notched characteristics for UWB applications are proposed. The presented antenna contains a slotted ground plane with an extra inverted U‐shaped slot at its top, coupled rectangular element with circular slot on its center, and a L‐shaped strip. The experimental results show that the designed antenna, with compact size of 20 × 22 mm2, has an impedance bandwidth from 2.65 to 13. 5GHz for VSWR≤ 2, except three frequency stop‐bands WiMAX, wireless local area network, and ITU. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2350–2354, 2013
Compact Dual‐Band‐Notched UWB Antenna with High Notch‐Band‐Edge Selectivity
Authors: Wang Junhui , Yin Yingzeng , Wang Tuo , Liu Xianglong
Published: July 2013

In this article, a compact ultrawideband (UWB) microstrip‐fed antenna with dual‐band‐notched characteristic for the wireless local area network and the world interoperability for microwave access is presented. The proposed antenna is mainly comprised of a slotted shovel‐shaped patch, a beveled ground with a pair of square slots, a nested arc‐shaped stub, and a pair of stepped capacitively loaded loop (CLL) elements. By introducing the arc‐shaped stub on the back of the substrate, which is connected to the patch by a cylindrical via pin, the lower notched band from 3.4 to 3.7 GHz is achieved. The upper notched band with high band selectivity from 5.1 to 5.9 GHz can be obtained by adding a couple of stepped CLL elements close to the feeding line and embedding an arc‐shaped slot in the radiation patch. The proposed antenna has a total size of 26 × 27 mm2 and operates at the whole UWB with dual‐notched bands. Throughout this article, the simulated and experimental results of impedance characteristic, gain, and radiation patterns are presented and discussed. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2507–2513, 2013
Design of Low‐Power and High‐Gain CMOS LNA with Current‐Reused Topology
Authors: Wang Sen , Lin Wen‐Jie
Published: July 2013

This article presents the design of low‐power and high‐gain X‐band CMOS low‐noise amplifier (LNA) using a current‐reused (CR) topology. The proposed LNA is equivalent to a three common‐source stage cascade amplifier. With the CR technique, the amplifier is benefit to boost power gain without increasing power dissipation. The CR‐LNA is fabricated by a standard 0.18‐μm CMOS process with a chip size of 0.59 mm. The quiescent current of the circuit is merely 4.2 mA from a power supply of 1.3 V. Measured results demonstrate 20.4‐dB gain, 3.7‐dB noise figure, 11‐dB input return loss, 18‐dB output return loss, −32‐dBm input PidB, and −18.3‐dBm IIP3 at 10.7 GHz, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2429–2431, 2013
Epigenetic regulation of genomic imprinting from germ line to preimplantation
Authors: MacDonald William A. , Mann Mellissa R.W.
Published: July 2013

Genomic imprinting is an epigenetic process that distinguishes parental alleles, resulting in parent‐specific expression of a gene or cluster of genes. Imprints are acquired during gametogenesis when genome‐wide epigenetic remodeling occurs. These imprints must then be maintained during preimplantation development, when another wave of genome‐wide epigenetic remodeling takes place. Thus, for imprints to persist as parent‐specific epigenetic marks, coordinated factors and processes must be involved to both recognize an imprint and protect it from genome‐wide remodeling. Parent‐specific DNA methylation has long been recognized as a primary epigenetic mark demarcating a genomic imprint. Recent work has advanced our understanding of how and when parent‐specific DNA methylation is erased and acquired in the germ line as well as maintained during preimplantation development. Epigenetic factors have also been identified that are recruited to imprinted regions to protect them from genome‐wide DNA demethylation during preimplantation development. Intriguingly, asynchrony in epigenetic reprogramming appears to be a recurrent theme with asynchronous acquisition between male and female germ lines, between different imprinted genes, and between the two parental alleles of a gene. Here, we review recent advancements and discuss how they impact our current understanding of the epigenetic regulation of genomic imprinting. Mol. Reprod. Dev. 81: 126–140, 2014. © 2013 Wiley Periodicals, Inc.
In vivo GABA T2 determination with J‐refocused echo time extension at 7 T
Authors: Andreychenko A. , Klomp D. W. J. , de Graaf R. A. , Luijten P. R. , Boer V. O.
Published: July 2013

A method to measure the T2 relaxation time of GABA with spectral editing techniques is proposed. Spectral editing techniques can be used to unambiguously extract signals of low concentration J‐coupled spins such as γ‐aminobutyric acid (GABA) from overlapping resonances such as creatine and macromolecules. These sequences, however, generally have fixed and relatively long echo times. Therefore, for the absolute quantification of the edited spectrum, the T2 relaxation time must be taken into account. To measure the T2 relaxation time, the signal intensity has to be obtained at multiple echo times. However, on a coupled spin system such as GABA this is challenging, since the signal intensity of the target resonances is modulated not only by T2 decay but also by the J‐coupling, which strongly influences the shapes and amplitudes of the edited signals, depending on the echo time. Here, we propose to refocus the J‐modulation of the edited signal at different echo times by using chemical shift selective refocusing. In this way the echo time can be arbitrarily extended while preserving the shape of the edited signal. The method was applied in combination with the MEGA‐sLASER editing technique to measure the in vivo T2 relaxation time of GABA (87 ± 11 ms, n = 10) and creatine (109 ± 8 ms, n = 10) at 7 T. The T1 relaxation time of these metabolites in a single subject was also determined (GABA, 1334 ± 158 ms; Cr, 1753 ± 12 ms). The T2 decay curve of coupled spin systems can be sampled in an arbitrary fashion without the need for signal shape correction. Furthermore, the method can be applied with any spectral editing technique. The shortest echo time of the method is limited by the echo time of the spectral editing technique. Copyright © 2013 John Wiley & Sons, Ltd.
A cool tool for hot and sour Archaea: Proteomics of Sulfolobus solfataricus
Authors: Kort Julia Christin , Esser Dominik , Pham Trong Khoa , Noirel Josselin , Wright Phillip C. , Siebers Bettina
Published: July 2013

In recent years, much progress has been made in proteomic studies to unravel metabolic pathways and basic cellular processes. This is especially interesting for members of the Archaea, the third domain of life. Archaea exhibit extraordinary features and many of their cultivable representatives are adaptable to extreme environments. Archaea harbor many unique traits besides bacterial attributes, such as size, shape, and DNA structure and eukaryal characteristics like information processing. Sulfolobus solfataricus P2, a thermoacidophilic archaeal representative, is a well‐established model organism adapted to low‐pH environments (pH 2–3) and high temperatures (80°C). The genome has a size of 3 Mbp and its sequence has been deciphered. Approximately 3033 predicted open reading frames have been identified and the genome is characterized by a great number of diverse insertion sequence elements. In unraveling the organisms’ metabolism and lifestyle, proteomic analyses have played a major role. Much effort has been directed at this organism and is reviewed here. With the help of proteomics, unique metabolic pathways were resolved in S. solfataricus, targets for regulatory protein phosphorylation identified, and cellular responses upon virus infection as well as oxidative stress analyzed.
Metaproteomics to unravel major microbial players in leaf litter and soil environments:Challenges and perspectives
Authors: Becher Dörte , Bernhardt Jörg , Fuchs Stephan , Riedel Katharina
Published: July 2013

Soil‐ and litter‐borne microorganisms vitally contribute to biogeochemical cycles. However, changes in environmental parameters but also human interferences may alter species composition and elicit alterations in microbial activities. Soil and litter metaproteomics, implying the assignment of soil and litter proteins to specific phylogenetic and functional groups, has a great potential to provide essential new insights into the impact of microbial diversity on soil ecosystem functioning. This article will illuminate challenges and perspectives of current soil and litter metaproteomics research, starting with an introduction to an appropriate experimental design and state‐of‐the‐art proteomics methodologies. This will be followed by a summary of important studies aimed at (i) the discovery of the major biotic drivers of leaf litter decomposition, (ii) metaproteomics analyses of rhizosphere‐inhabiting microbes, and (iii) global approaches to study bioremediation processes. The review will be closed by a brief outlook on future developments and some concluding remarks, which should assist the reader to develop successful concepts for soil and litter metaproteomics studies.
Environmental proteomics reveals early microbial community responses to biostimulation at a uranium‐ and nitrate‐contaminated site
Authors: Chourey Karuna , Nissen Silke , Vishnivetskaya Tatiana , Shah Manesh , Pfiffner Susan , Hettich Robert L. , Löffler Frank E.
Published: July 2013

High‐performance MS instrumentation coupled with improved protein extraction techniques enables metaproteomics to identify active members of soil and groundwater microbial communities. Metaproteomics workflows were applied to study the initial responses (i.e. 4 days post treatment) of the indigenous aquifer microbiota to biostimulation with emulsified vegetable oil (EVO) at a uranium‐contaminated site. Members of the Betaproteobacteria (i.e. Dechloromonas, Ralstonia, Rhodoferax, Polaromonas, Delftia, Chromobacterium) and the Firmicutes dominated the biostimulated aquifer community. Proteome characterization revealed distinct differences between the microbial biomass collected from groundwater influenced by biostimulation and groundwater collected upgradient of the EVO injection points. In particular, proteins involved in ammonium assimilation, EVO degradation, and polyhydroxybutyrate granule formation were prominent following biostimulation. Interestingly, the atypical NosZ of Dechloromonas spp. was highly abundant, suggesting active nitrous oxide (N2O) respiration. c‐Type cytochromes were barely detected, as was citrate synthase, a biomarker for hexavalent uranium reduction activity, suggesting that uranium reduction has not commenced 4 days post EVO amendment. Environmental metaproteomics identified microbial community responses to biostimulation and elucidated active pathways demonstrating the value of this technique as a monitoring tool and for complementing nucleic acid‐based approaches.
Proteomic tools for environmental microbiology—A roadmap from sample preparation to protein identification and quantification
Authors: Wöhlbrand Lars , Trautwein Kathleen , Rabus Ralf
Published: July 2013

The steadily increasing amount of (meta‐)genomic sequence information of diverse organisms and habitats has a strong impact on research in microbial physiology and ecology. In‐depth functional understanding of metabolic processes and overall physiological adaptation to environmental changes, however, requires application of proteomics, as the context specific proteome constitutes the true functional output of a cell. Considering the enormous structural and functional diversity of proteins, only rational combinations of various analytical approaches allow a holistic view on the overall state of the cell. Within the past decade, proteomic methods became increasingly accessible to microbiologists mainly due to the robustness of analytical methods (e.g. 2DE), and affordability of mass spectrometers and their relative ease of use. This review provides an overview on the complex portfolio of state‐of‐the‐art proteomics and highlights the basic principles of key methods, ranging from sample preparation of laboratory or environmental samples, via protein/peptide separation (gel‐based or gel‐free) and different types of mass spectrometric protein/peptide analyses, to protein identification and abundance determination.
Selected hydroxycoumarins as antioxidants in cells: physicochemical and reactive oxygen species scavenging studies
Authors: Pérez‐Cruz Fernanda , Villamena Frederick A. , Zapata‐Torres Gerald , Das Amlan , Headley Colwyn A. , Quezada Elias , Lopez‐Alarcon Camilo , Olea‐Azar Claudio
Published: July 2013

A set of seven hydroxycoumarin derivatives (1–7) were tested to evaluate their antioxidant properties. These molecules were selected on the basis of the number of hydroxyl groups and the presence of electron‐donating and electron‐withdrawing groups in their scaffolds. Electrochemical studies showed that oxidation process occurs at low potentials, especially with the catechol‐containing coumarins. Electron spin resonance (ESR) experiments corroborated the formation of semiquinone radicals in all compounds. The antioxidant properties against peroxyl and hydroxyl radicals were evaluated using two different assays, namely oxygen radical antioxidant capacity (ORAC) and non‐catalytic Fenton system by ESR measurements. Our results indicated that monohydroxycoumarin derivatives (1 and 2) displayed better ORAC values relative to the standard molecule Trolox. These values are comparable with known flavonoids such as quercetin and catechin. On the other hand, compounds bearing catechol and resorcinol groups, including derivative 4, gave high hydroxyl radical‐scavenging properties. Antioxidant properties were further rationalized using density functional theory calculations. The theoretical results showed good trends among the obtained experimental data, calculated bonding dissociation enthalpy, highest occupied molecular orbital values, free energies of oxidation (ΔGox) and spin density distribution. Finally, in vitro studies revealed low toxicity for most of the coumarins studied. The cytoprotection assays in bovine aortic endothelial cells indicated that compounds 1 and 2 showed better protective properties against peroxynitrite and hydrogen peroxide‐induced cell death than dihydroxycoumarin derivatives. Using confocal microscopy, we have observed intracellular compartmentalization. These results confirm that 1 or 2 would be a good target for future in vivo studies against oxidative stress. Copyright © 2013 John Wiley & Sons, Ltd.
Dose finding when the target dose is on a plateau of a dose–response curve: comparison of fully sequential designs
Authors: Ivanova Anastasia , Xiao Changfu
Published: July 2013

Consider the problem of estimating a dose with a certain response rate. Many multistage dose‐finding designs for this problem were originally developed for oncology studies where the mean dose–response is strictly increasing in dose. In non‐oncology phase II dose‐finding studies, the dose–response curve often plateaus in the range of interest, and there are several doses with the mean response equal to the target. In this case, it is usually of interest to find the lowest of these doses because higher doses might have higher adverse event rates. It is often desirable to compare the response rate at the estimated target dose with a placebo and/or active control. We investigate which of the several known dose‐finding methods developed for oncology phase I trials is the most suitable when the dose–response curve plateaus. Some of the designs tend to spread the allocation among the doses on the plateau. Others, such as the continual reassessment method and thet‐statistic design, concentrate allocation at one of the doses with thet‐statistic design selecting the lowest dose on the plateau more frequently. Copyright © 2013 John Wiley & Sons, Ltd.
Modelling and control of a five‐degrees‐of‐freedom pneumatically actuated magnetic resonance‐compatible robot
Authors: Jiang Shan , Feng Wenhao , Lou Jinlong , Yang Zhiyong , Liu Jun , Yang Jun
Published: July 2013

Background

Magnetic resonance imaging (MRI) combined with robotic assistance has the potential to improve on clinical outcomes of biopsy and local treatment of prostate cancer. This paper introduces a pneumatically actuated surgical robotic system for prostatic interventions under MRI guidance.

Methods

A mechanical dynamics model was established using the Lagrange method and simulated using MATLAB software. A pneumatic actuator model was built through the use of system identification, and stability analysis was proposed based on the Nyquist criterion. In addition, a proportional‐integral‐derivative controller was implemented on the robot for accurate position control.

Results

Simulation results showed that the steady‐state error of a step response was 0.3 mm and the tracking error of a 1.0 Hz sinusoidal response was 1.5 mm. Experimental results showed that the insertion precision was 0.72 mm in the general laboratory environment.

Conclusions

The results demonstrated that the robotic system with the designed controller was effective in both position control and trajectory tracking. Copyright © 2013 John Wiley & Sons, Ltd.
Modeling of the perfect electromagnetic conducting boundary in the finite difference time domain method
Authors: Nayyeri Vahid , Soleimani Mohammad , Dehmollaian Mojtaba
Published: July 2013

The perfect electromagnetic conducting (PEMC) boundary, a nonreciprocal generalization of both perfect electric conducting (PEC) and perfect magnetic conducting (PMC) boundaries, is modeled in the finite difference time domain (FDTD) method. Since the PEMC boundary condition requires collocation of same components of both electric and magnetic fields at the boundary grids, which is not compatible with the original FDTD algorithm, its implementation in FDTD is challenging and requires modification in the algorithm. To do this task, first, the original FDTD cell is modified by inserting the required field components not present in the original cell. Then, a novel formulation is developed for updating fields' components at the boundary. Modeling of a PEMC planar interface, a corner point, and a wedge point are presented. Finally, numerical examples are presented to show stability, accuracy, and applicability of the proposed approach. Validation is achieved by comparisons with existing analytic methods and/or conventional FDTD for special cases of PEC and PMC boundaries.
Surface characterization of TEMPO‐oxidized bacterial cellulose
Authors: Lai Chen , Sheng Liyuan , Liao Shibo , Xi Tingfei , Zhang Zhixiong
Published: July 2013

In this study, we focused on the surface character of bacterial cellulose (BC) before and after oxidation mediated by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO).Solid‐state 13C NMR, XPS, SEM, contact angle and surface free energy analyses were performed to investigate the effects of various parameters (reaction time and oxidant and catalyst concentrations) on the surface composition, morphology and polarity of the BC. The results provided by the combined use of these techniques showed that hydrogen bonds were disrupted on the BC surface after carboxylation occurred; therefore, the surface of oxidized BC was rougher than that of the original BC, and the surface free energy, especially the polar components, increased after oxidation. Copyright © 2013 John Wiley & Sons, Ltd.
Extending model checkers for hybrid system verification: the case study of SPIN
Authors: Gallardo María‐del‐Mar , Panizo Laura
Published: July 2013

A hybrid system is a system that evolves following a continuous dynamic, which may instantaneously change when certain internal or external events occur. Because of this combination of discrete and continuous dynamics, the behaviour of a hybrid system is, in general, difficult to model and analyse. Model checking techniques have been proven to be an excellent approach to analyse critical properties of complex systems. This paper presents a new methodology to extend explicit model checkers for hybrid systems analysis. The explicit model checker is integrated, in a non‐intrusive way, with some external structures and existing abstraction libraries, which store and manipulate the abstraction of the continuous behaviour irrespective of the underlying model checker. The methodology is applied to SPIN using Parma Polyhedra Library. In addition, the authors are currently working on the extension of other model checkers. Copyright © 2013 John Wiley & Sons, Ltd.
Re: Umbilical vein flow and perinatal outcome in term small‐for‐gestational‐age fetuses. M. Parra‐Saavedra, F. Crovetto, S. Triunfo, S. Savchev, G. Parra, M. Sanz, E. Gratacos and F. Figueras. Ultrasound Obstet Gynecol 2013; 42: 189–195
Authors: Kiserud T.
Published: July 2013

Linked Comment: Ultrasound Obstet Gynecol 2013:42:189–195
Glycosaminoglycan metabolism defects and atherosclerosis: frequent association of endothelial dysfunction in patients with Mucopolysaccharidosis
Authors: Yano Shoji , Moseley Kathryn , Wong Lawrence , Castelnovi Claudia , Azen Colleen , Pavlova Zdena
Published: July 2013

Cardiovascular lesions, including coronary artery stenosis, are frequently associated and can cause sudden death in patients with genetic defects of glycosaminoglycan (GAG) metabolism. Early diagnosis of coronary artery lesions is difficult, although potentially lifesaving. Histopathological similarities between atherosclerotic changes in adults and in patients with genetic GAG metabolism defects have been known. Atherosclerosis is the result of a complex process involving metabolism of GAGs and proteoglycans preceded by endothelial dysfunction as a key event. Decreased nitric oxide (NO) bioavailability is considered the hallmark of endothelial dysfunction. Reduced NO synthase (NOS) has been reported in atherosclerotic arteries. Impairment in reactive hyperemia‐digital peripheral arterial tonometry (RH‐PAT) with EndoPAT has been validated to correlate coronary microvascular function in patients with atherosclerosis. RH‐PAT is thought to reflect endothelial NO production. Immunohistological staining of endothelial NOS was performed in the stenotic lesions in the coronary artery of a 3‐year‐old patient with Mucopolysaccharidosis‐I, showing decreased activities. This prompted a study to measure endothelial function in patients with GAG metabolism defects for early diagnosis of endothelial dysfunction in the coronary arteries as an early sign of coronary artery changes. Evaluation by RH‐PAT in 30 patients with variable genetic defects in GAG metabolism revealed significantly decreased Reactive Hyperemia Indexes compared with 12 controls. Evaluation of endothelial function with RH‐PAT in patients with GAG metabolism defects may detect coronary artery lesions that can be underdiagnosed by the other measures such as coronary angiography. Use of this method may prove vital in the management of patients with GAG metabolism defects.
Improved Pupil Dilation With Medication‐Soaked Pledget Sponges
Authors: Weddle Celeste , Thomas Nikki , Dienemann Jacqueline
Published: July 2013

Use of multiple preoperative drops for pupil dilation has been shown to be inexact, to delay surgery, and to cause dissatisfaction among perioperative personnel. This article reports on an evidence‐based, quality improvement project to locate and appraise research on improved effectiveness and efficiency of mydriasis (ie, pupillary dilation), and the subsequent implementation of a pledget‐sponge procedure for pupil dilation at one ambulatory surgery center. Project leaders used an evidence‐based practice model to assess the problem, research options for improvement, define goals, and implement a pilot project to test the new dilation technique. Outcomes from the pilot project showed a reduced number of delays caused by poor pupil dilation and a decrease in procedure turnover time. The project team solicited informal feedback from preoperative nurses, which reflected increased satisfaction in preparing patients for cataract procedures. After facility administrators and surgeons accepted the procedure change, it was adopted for preoperative use for all patients undergoing cataract surgery at the ambulatory surgery center.
Perioperative Cardiopulmonary Arrest Competencies
Authors: Murdock Darlene B.
Published: July 2013

Although basic life support skills are not often needed in the surgical setting, it is crucial that surgical team members understand their roles and are ready to intervene swiftly and effectively if necessary. Ongoing education and training are key elements to equip surgical team members with the skills and knowledge they need to handle untimely and unexpected life‐threatening scenarios in the perioperative setting. Regular emergency cardiopulmonary arrest skills education, including the use of checklists, and mock codes are ways to validate that team members understand their responsibilities and are competent to help if an arrest occurs in the OR. After a mock drill, a debriefing session can help team members discuss and critique their performances and improve their knowledge and mastery of skills.