bluuebunny/crossref_metadata_2025 huggingface dataset:
Small monopole antenna with multiresonance characteristic by using rotated T‐shaped slit and parasitic structure for UWB systems
Authors: Ojaroudi Nasser , Ojaroudi Mohammad
Published: January 2013

In this letter, we present a new design of small‐sized, low‐profile, and multiresonance monopole antenna for ultrawideband applications.The proposed antenna consists of a square radiating patch and a ground plane with rotated T‐shaped slit and conductor‐backed plane, which provides a wide usable fractional bandwidth of more than 130% (3.05–15.27 GHz). By cutting a rotated T‐shaped slit on the ground plane and also by inserting rotated T‐shaped parasitic structure, additional resonances are excited and hence much wider impedance bandwidth can be produced, especially at the higher band. The designed antenna has a small size. Simulated and experimental results obtained for the proposed antenna is suitable for UWB applications. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:482–485, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27358
A multiwideband planar monopole antenna for 4G devices
Authors: Asghar A. M. , Malick M. , Karlsson M. , Hussain A.
Published: January 2013

This article presents a compact multiband planar antenna designed for mobile phone applications.The antenna performance is achieved by designing a planar monopole antenna into distributed radiating elements. The proposed antenna is comprised of a chopped circular radiator appended with a meander line and an L‐strip coupled element, which is an extension of the ground plane. The combination of a chopped circular patch and L‐shaped coupling strip residing on the top side generates lower band while upper band resonances are attained separately by chopped circular resonator and meander line elements. The antenna shows a planar structure which occupies an area of 56 × 17.6 mm and can be directly printed onto a circuit board at low cost making it especially suitable for mobile phone applications. The manufactured antenna is experimentally verified and covers several wireless communication bands, such as LTE 750, GSM 850, GSM 900, DCS, UMTS‐2110, Bluetooth, WLAN, WiMAX, and UWB. The high frequency structure simulation is used to design and analyze the antenna performance, and a practical structure was fabricated and tested. The measured and simulated return loss show good agreement. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:589–593, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27360
Planar ultrawideband antenna with multiple band‐notches based on folded stepped‐impedance resonator and defected split ring resonator
Authors: Li Tong , Zhai Huiqing , Li Guihong , Li Long , Liang Changhong
Published: January 2013

To avoid potential inference problems due to the existing wireless communication systems within ultrawideband (UWB) operating frequency, a planar UWB antenna with triple band‐notches is proposed in this article. This antenna provides good rejection characteristic at 2.4/3.5/5.5 GHz bands by folded stepped‐impedance resonators (SIRs) coupled to the feed line, and defected split ring resonators below the folded SIRs. The stacked notch structure generates multiband notches but occupies only one area. Good agreement between the simulation and measurement is obtained, which shows that the proposed antenna achieves a wide bandwidth from 2 to 12 GHz with triple band‐notches successfully. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:600–603, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27364
UWB power divider with one narrow notch‐band and wide stop‐band
Authors: Chen Lei , Wei Feng , Jia Gao Chang , Qiang Liu Wei
Published: January 2013

A compact ultrawideband (UWB) microstrip power divider (PD) with one sharply rejected notch‐band and wide stopband is analyzed and designed in this article.The proposed UWB PD is based on conventional Wilkinson PD, while interdigital hairpin resonators are introduced in two symmetrical output ports to widen passband. The stepped impedance resonator is studied and used to generate one desired notched band. Defected ground structure is introduced to improved stopband performance. Theoretical and simulated results are presented, which are in good agreement with the measured results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:597–600, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27365
Optimization of slit structures for transmission enhancement of THz wave
Authors: Yuan Minghui , Huang Xin , Zhang Xuanfeng
Published: January 2013

Optimal transmission characteristics of THz wave through a slit aperture with parallel grooves on both sides are analyzed numerically by the finite element method. Simulations results show that the center transmissivity can be up to above 95% because of the enhanced transmission effect induced by surface plasmon polaritons. With the increase of periodicity length p or center hole width d or groove depth s, the center frequency shifts red linearly, the center transmissivity increases firstly and then decreases. Furthermore, with the increase of d/p, w/p, or s/t, the center transmissivity increases firstly and then decreases, which the optimal values d/p= 0.25–0.3, w/p= 0.5, and s/t= 0.2. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:559–561, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27366
Considerations on the backscattered wireless communication links
Authors: Duroc Yvan , Vera Gianfranco Andia
Published: January 2013

This article presents a study of the backscattered wireless communication links, in far‐field conditions, emphasizing new approaches.General expressions for forward and return link on the reradiating coexistence of antennas are presented. A formulation for the radar cross section parameter is proposed for taking into account the phase information in modeling. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:554–559, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27367
Hexaferrite slant and slot MIMO antenna element for mobile devices
Authors: Abo Gavin S. , Hong Yang‐Ki , Syslo Ryan , Lee Jaejin , Lee Woncheol , Kwon Hyuck M. , Jayasooriya Chandana K. K.
Published: January 2013

A hexaferrite slant and slot multiple‐input multiple‐output antenna with miniature antenna elements was simulated, fabricated, and characterized for antenna performance. Measured return loss and isolation were −33.9/−26.6 dB (for antenna 1/antenna 2) and −18.6 dB at 2.45 GHz, respectively. Measured bandwidth was 454/502 MHz at VSWR < 3. Correlation coefficient between antenna elements calculated from experimental S‐parameters was less than 0.00085 between 2.4 and 2.5 GHz. Radiation efficiency of the antennas was measured to be 82% at 2.45 GHz. The antennas have two lobes, omnidirectional, and flower patterns for potential mobile device applications. Simulated and measured antenna performance was found to be in good agreement with each other. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:551–554, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27370
Dual notched U—Slots triple band tunable rectangular microstrip antenna
Authors: Kulkarni Nagraj , Mulgi S. N. , Satnoor S. K.
Published: January 2013

This article presents a novel design and development of dual‐notched U slots rectangular microstrip antenna for quad band tunable operation. The antenna operates between 3.45 and 8.75 GHz at four different frequency bands. The middle two bands merge into a single band by changing the width of U slot on the patch. This change will also effect in tuning the three bands on either side of the frequency spectrum without changing the nature of linearly polarized broadside radiation characteristics. The proposed antenna gives a peak gain of 1.52 dB. The experimental and simulated results are in good agreement with each other. A design concept of the antenna is given and experimental results are presented and discussed. This antenna may find applications in WLAN, WiMax, and the fourth generation mobile communication systems. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:509–513, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27372
Compact parallel‐coupled line bandpass filter using double complementary split ring resonators
Authors: Ahn Chi‐Hyung , Jung Dong‐Jin , Chang Kai
Published: January 2013

A novel compact parallel‐coupled line bandpass filter (BPF) with complementary split ring resonators (CSRRs) is presented in this letter.The proposed BPF, with a combination of CSRRs and parallel‐coupled lines, has the advantages of compact size and simpler design procedure compared with conventional CRSS BPFs. The prototype filter achieves the measured insertion loss of 1.4 dB at 3.6 GHz. The implementing area is 0.35 λg × 0.14 λg, where λg is the guided wavelength at the resonant frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:506–509, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27373
AN ENG ZOR unit cell antenna using spiral inductors with enhanced bandwidth
Authors: Kim Jeongpyo , Yang Dooyeong
Published: January 2013

In this article, the characteristics of an epsilon negative zeroth‐order resonator (ENG ZOR) unit cell antenna are studied. The proposed ENG ZOR unit cell consists of two shunt inductors with a spiral inductor and a vertical post for epsilon negative property and a bent patch between two inductors for right‐handed property. The shunt inductors of the ENG ZOR unit cell are fabricated by using square spiral inductors and vertical posts. The impedance bandwidth and radiation efficiency of the designed ENG ZOR unit cell antenna are compared by adjusting dimensions of spiral inductors and fixing the patch between two spiral inductors. Under the constant resonant frequency, the bandwidth of the ENG ZOR antenna is proportional to the parasitic resistance of the spiral inductor without decreasing of the radiation efficiency. Therefore, the bandwidth of the ENG ZOR with a spiral inductor can be widened by narrowing the line width of the spiral inductor. Details of the antenna characteristics are described, and both simulated and measured results of the designed antenna are presented. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:567–571, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27382
An inverse problem for dielectrics that depend on two spatial variables
Authors: Hooshyar M. A. , Paudel Ajaya
Published: January 2013

The inversion method developed by Reese T. Prosser for waves in three dimensions is modified to solve inverse problems of back scattered data for TM plane waves incident on cylindrical structures with dielectric properties that are function of two spatial variables. Not only the bounds needed for convergence proof of the modified method are found but also the method is numerically implemented and its numerical performance examined. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:561–566, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27383
Two antipodal vivaldi antennas and an antenna array for microwave early breast cancer detection
Authors: Shao Wenyi , Adams Ryan S.
Published: January 2013

Two small antipodal Vivaldi antennas for ultrawide band early breast cancer detection are proposed. The antennas are designed to operate in the spectrum from 1 to 10 GHz, according to the requirements of wave penetration in the breast and imaging resolution. Simulated and measured reflection parameters of the proposed antennas are evaluated. Numerical results also show the proposed antennas have good near‐field radiation performance. Finally, an antenna array consisting of eight antipodal Vivaldi antennas, appropriate to collect the tumor scattering signal in the breast is presented. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:670–674, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27384
The use of lattice networks for modelling symmetric transmission line components and discontinuities
Authors: Abdo‐Sánchez Elena , Esteban Jaime , Martín‐Guerrero Teresa M. , Page Juan E. , Camacho‐Peñalosa Carlos
Published: January 2013

This article proposes the lattice network as a beneficial alternative to T‐ and
$ \Pi - $topologies for modeling symmetric transmission line discontinuities and components.The lattice network presents some important features, which make it a powerful tool to find realizable equivalent circuits. The limitations of the T‐ and
$ \Pi - $topologies and the validity of the lattice network in terms of realizability are highlighted in this article through two microstrip components: a dumbbell‐shaped defected ground structure and a microstrip stepped‐impedance hairpin resonator. Moreover, the lattice image impedance is proposed here as a parameter that allows determining whether a branch of the network is predominant. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:636–639, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27385
Novel 2:1 Wilkinson power divider integrated with bandpass filter
Authors: Gao Li , Yin Zhang Xiu
Published: January 2013

A novel 2:1 Wilkinson power divider integrated with two bandpass filters is presented in this article.The proposed device exhibits the unequal power splitting function with a bandpass response. The phase and impedance characteristics of the bandpass filters can be conveniently tuned to realize impedance transformation. Thus they can replace the quarter‐wavelength transmission lines of the unequal Wilkinson power divider. The integrated device results in lower insertion loss and smaller circuit area, as compared with the cascaded connection of an unequal power divider and two filters. For demonstration, a 2:1 power divider integrated with bandpass filters is implemented. Comparisons of the measured and simulated results are presented to verify the proposed design. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:646–648, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27395
Characteristics of optical fiber refractive index sensor based on surface plasmon resonance
Authors: Lin Yu‐Cheng
Published: January 2013

A refractive index optical fiber sensor based on surface plasmon resonance technology is demonstrated. The sensing device is a multimode optical fiber in which half of the core is polished away and a thin‐film layer of gold is deposited. We measure the spectrum‐difference variations and the resonance wavelength shifts for different refractive index solutions. In terms of the experimental data, the characteristics including resolution, sensitivity, and signal‐to‐noise ratio for the sensor are obtained. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:574–576, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27397
Lung morphometry using hyperpolarized 129Xe apparent diffusion coefficient anisotropy in chronic obstructive pulmonary disease
Authors: Ouriadov Alexei , Farag Adam , Kirby Miranda , McCormack David G. , Parraga Grace , Santyr Giles E.
Published: January 2013

Purpose

The goal of this work was to investigate lung morphological changes associated with chronic obstructive pulmonary disease (COPD) using hyperpolarized 129Xe diffusion‐weighted MRI.

Methods

Hyperpolarized 129Xe MRI was performed at three different nonzero diffusion sensitizations (b‐value = 12, 20, and 30 s/cm2) in the lungs of four subjects with COPD and four healthy volunteers. The image signal intensities were fit as a function of b‐value to obtain anisotropic diffusion coefficient maps for all subjects. The image signal intensities were also fit to a morphological model allowing extraction of length scales associated with the terminal airways: external radius (R), internal radius (r), mean airspace chord length (Lm), and depth of alveolar sleeve (h).

Results

Longitudinal (DL) and transverse (DT) anisotropic diffusion coefficients were both significantly increased (both P= 0.004) in the COPD subjects (0.102 ± 0.02 cm2/s and 0.072 ± 0.02 cm2/s, respectively) compared with the healthy subjects (0.083 ± 0.011 cm2/s and 0.046 ± 0.017 cm2/s, respectively). Significant morphological differences were observed between the COPD subjects and healthy volunteers, specifically decreases in h (68 ± 36 µm vs. 95 ± 710 µm, respectively, P = 0.019) and increases in Lm (352 ± 57 µm vs. 253 ± 37 µm, respectively, P = 0.002) consistent with values obtained previously using hyperpolarized 3He MRI in similar subjects.

Conclusions

Diffusion‐weighted hyperpolarized 129Xe MRI is a promising technique for mapping changes in human lung morphology and may be useful for early detection of emphysema associated with COPD. Magn Reson Med 70:1699–1706, 2013. © 2013 Wiley Periodicals, Inc.
Association between anti‐TNF‐α therapy and interstitial lung disease
Authors: Herrinton Lisa J. , Harrold Leslie R. , Liu Liyan , Raebel Marsha A. , Taharka Ananse' , Winthrop Kevin L. , Solomon Daniel H. , Curtis Jeffrey R. , Lewis James D. , Saag Kenneth G.
Published: January 2013

Background

Anti‐tumor necrosis factor‐α (TNF‐α) agents have been hypothesized to increase the risk of interstitial lung disease (ILD), including its most severe manifestation, pulmonary fibrosis.

Methods

We conducted a cohort study among autoimmune disease patients who were members of Kaiser Permanente Northern California, 1998–2007. We obtained therapies from pharmacy data and diagnoses of ILD from review of X‐ray and computed tomography reports. We compared new users of anti‐TNF‐α agents to new users of non‐biologic therapies using Cox proportional hazards analysis to adjust for baseline propensity scores and time‐varying use of glucocorticoids. We also made head‐to‐head comparisons between anti‐TNF‐α agents.

Results

Among the 8417 persons included in the analysis, 38 (0.4%) received a diagnostic code for ILD by the end of follow‐up, including 23 of 4200 (0.5%) who used anti‐TNF‐α during study follow‐up, and 15 of 5423 (0.3%) who used only non‐biologic therapies. The age‐standardized and gender‐standardized incidence rate of ILD, per 100 person‐years, was 0.21 [95% confidence interval (CI) 0–0.43] for rheumatoid arthritis and appreciably lower for other autoimmune diseases. Compared with the use of non‐biologic therapies, use of anti‐TNF‐α therapy was not associated with a diagnosis of ILD among patients with rheumatoid arthritis (adjusted hazard ratio, 1.03; 95%CI 0.51–2.07), nor did head‐to‐head comparisons across anti‐TNF‐α agents suggest important differences in risk, although the number of cases available for analysis was limited.

Conclusion

The study provides evidence that compared with non‐biologic therapies, anti‐TNF‐α therapy does not increase the occurrence of ILD among patients with autoimmune diseases and informs research design of future safety studies of ILD. Copyright © 2013 John Wiley & Sons, Ltd.
Safe lists for medications in pregnancy: inadequate evidence base and inconsistent guidance from Web‐based information, 2011
Authors: Peters Stacey L. , Lind Jennifer N. , Humphrey Jasmine R. , Friedman Jan M. , Honein Margaret A. , Tassinari Melissa S. , Moore Cynthia A. , Mathis Lisa L. , Broussard Cheryl S.
Published: January 2013

Purpose

Medication use during pregnancy is common and increasing. Women are also increasingly getting healthcare information from sources other than their physicians.

Methods

This report summarizes an environmental scan that identified 25 active Internet sites that list medications reported to be safe for use in pregnancy and highlights the inadequate evidence base and inconsistent guidance provided by these sites.

Results

These lists included 245 different products, of which 103 unique components had been previously evaluated in terms of fetal risk by the Teratogen Information System (TERIS), a resource that assesses risk of birth defects after exposure under usual conditions by consensus of clinical teratology experts. For 43 (42%) of the 103 components that were listed as ‘safe’ on one or more of the Internet sites surveyed, the TERIS experts were unable to determine the fetal risk based on published scientific literature. For 40 (93%) of these 43, either no data were available to assess human fetal risk or the available data were limited.

Conclusions

Women who see a medication on one of these ‘safe’ lists would be led to believe that there is no increased risk of birth defects resulting from exposure. Thus, women are being reassured that fetal exposure to these medications is safe even though a sufficient evidence base to determine the relative safety or risk does not exist. Copyright © 2013 John Wiley & Sons, Ltd.
Fast GaN based Schottky diodes on Si(111) substrate with low onset voltage and strong reverse blocking
Authors: Treidel Eldad Bahat , Hilt Oliver , Wentzel Andreas , Würfl Joachim , Tränkle Günther
Published: January 2013

GaN‐based heterostructure lateral Schottky barrier diodes (SBD) grown on Si(111) substrate are presented in this work. These SBDs own very low onset‐voltage, VF = 0.50 V, high reverse blocking VBR > 600 V for LAC > 8 µm, very low capacitive charge of 0.415 nC/A and a very fast recovery time of 6 ps extracted under large signal operation conditions. These unique qualities are achieved by combining lateral topology, AlGaN back‐barrier epitaxial structure, fully recessed Schottky anode (ϕB = 0.62 eV) and anode field plate extension (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron‐beam incident‐angle‐ resolved cathodoluminescence studies on bulk ZnO crystals
Authors: Onuma Takeyoshi , Yamaguchi Tomohiro , Honda Tohru
Published: January 2013

Electron‐beam incidence‐angle‐resolved cathodoluminescence (IAR‐CL) measurements on ZnO single crystals were demonstrated as an alternative way for the depth‐resolved cathodoluminescence (CL) study by scanning acceleration voltage of the electron‐beam. Incidence‐angle dependent near‐band‐edge CL intensities were well reproduced by analyses considering a radiation pattern, an expansion of the electron‐beam irradiation area, and an internal absorption factors. The quantitative agreement between the experimental and simulated results indicates that the IAR‐CL technique is suitable for practical use in the depth‐resolved CL study of device structures (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The impact of cloud‐affected IR radiances on forecast accuracy of a limited‐area NWP model
Authors: Stengel M. , Lindskog M. , Undén P. , Gustafsson N.
Published: January 2013

The impact of cloud‐affected satellite radiances on numerical weather prediction (NWP) accuracy is investigated. The NWP model used is the HIgh Resolution Limited Area Model (HIRLAM). Its four‐dimensional variational data assimilation (4D‐Var) system was used to assimilate cloud‐affected infrared (IR) radiances from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI). Cloud parameters are modelled internally in the observation operator and used in the radiative transfer calculations. The interaction between the cloud parameters and the model control vector variables is incorporated in the adjoint version of the observation operator, which is used to derive cloud‐affected Jacobians prior to the inner‐loop minimization of the cost function.

The developed framework supports an extensive usage of satellite observations with spatial coverage extended into cloudy regions, which therefore provides additional analysis increments and supports a more accurate description of the atmospheric state. In extended assimilation and forecast experiments the total number of assimilated satellite observations could be increased by approximately 10%. This was associated with a clear indication of a positive impact of cloud‐affected radiances on the moisture and geopotential height ﬁelds of the NWP model analysis and forecast accuracy when used on top of clear‐sky radiance observations. This is revealed by reduced analysis errors of the total integrated water vapour and by reduced forecast errors in the mid and upper troposphere.
Comment on “Statistical physics of a mesoscopic fermion system inside a rectangular box” by Radu Lungu
Authors: Toutounji Mohamad
Published: January 2013

This comment is to overemphasize that the mathematical treatment, calculations, discussions, and concluding remarks in the article by Toutounji[1] are limited to one‐particle system only; this is to the contrary of what the author in Lungu[2] tried to seize on. © 2012 Wiley Periodicals, Inc.
Deregulation and differentiation: Incumbent investment in green technologies
Authors: Kim Eun‐Hee
Published: January 2013

Integrating elements from industrial organization economics and the resource‐based view—coupled with path dependence as firm resources evolve over time, this paper suggests that deregulation may not always provide greater opportunities for incumbents, and the extent to which incumbents differentiate on the green dimension may be constrained by their prior resources, in particular, capabilities with respect to brown technologies and experiences with green technologies. Using data on U.S. investor‐owned electric utilities from 1992 to 2008, this paper finds that deregulation is associated with lower entry into the renewable generation market by incumbents compared to regulation. More capable firms using brown technologies, for example, coal‐based generation, are less likely to enter the renewable generation market. Also, incumbents are responsive to actual, not latent, demand for renewable energy. Copyright © 2013 John Wiley & Sons, Ltd.
Are there always synergies between productive resources and resource deployment capabilities?
Authors: Huesch Marco D.
Published: January 2013

While the independent impacts of particular firm resources and deployment capabilities on firm performance are unambiguous cornerstones of the strategy field, it is commonly assumed that their joint impacts are synergistic. This article seeks to understand whether this common misconception of resource‐based theory can be refuted empirically. Using data from hospitals conducting specialist surgery, I find hospital performance improves independently through better surgical resource quality and from more use of a streamlined form of resource management in which overall patient team leadership and operating team leadership are held by the same physician. Generally the interaction of these two firm activities had no impact on performance. These results contribute to the strategy field's understanding of whether and when internal fit affects performance, clarifying an incorrect inference commonly made about resource‐based theory. Copyright © 2013 John Wiley & Sons, Ltd.
Opportunity costs, industry dynamics, and corporate diversification: Evidence from the cardiovascular medical device industry, 1976–2004
Authors: Wu Brian
Published: January 2013

This paper examines how demand conditions across alternative markets impact diversification decisions and firm performance by influencing the opportunity costs of deploying non‐scale free capabilities. Using data within the cardiovascular medical device industry, this study shows that: (1) firms with a larger stock of pre‐entry innovation experience are more likely to diversify; (2) firms in a current market with greater relative demand maturity are more likely to diversify; (3) diversification is associated with a performance decrease in the current market; and (4) diversification is associated with a performance increase at the corporate level. These findings shed new light on the self‐selection process of corporate scope, the conceptualization of firm capabilities, and the connection between industry dynamics and resource deployment. Copyright © 2013 John Wiley & Sons, Ltd.
Social network contingency, symbolic management, and boundary stretching
Authors: Markóczy Lívia , Li Sun Sunny , Peng Mike W. , (Stone) Shi Weilei , Ren Bing
Published: January 2013

A firm's structural position within corporate networks may affect the extent to which it engages in boundary stretching practices. Since social norms support low CEO compensation, offering high CEO compensation in China can be seen as a boundary stretching practice. Setting up a compensation committee (CC) may be viewed as a form of symbolic management in China. We argue that firms operating within central corporate network positions opt to pay higher CEO compensation without engaging in symbolic management. On the other hand, firms operating in structural hole positions tend to either pay lower CEO compensation or use CCs as a symbolic management tool in order to pay higher CEO compensation. Our hypotheses are largely supported based on 7,618 firm‐year observations in China. Copyright © 2013 John Wiley & Sons, Ltd.
Venture capitalists' decision to withdraw: The role of portfolio configuration from a real options lens
Authors: Li Yong , Chi Tailan
Published: January 2013

When does a venture capital firm withdraw from an investment project prior to its completion? This study offers a real options view on this decision by examining the contingent effects of portfolio configuration. We explore how project withdrawal can be influenced by two distinct dimensions of portfolio configuration, portfolio focus in a strategic domain and portfolio diversity across multiple domains. The empirical analysis shows that while portfolio focus weakens the negative effect of industry‐level uncertainty on a venture capitalist's propensity to withdraw from a project, portfolio diversity strengthens the effect of uncertainty. This study informs current research on the boundary of real options theory and sheds light on the behavior of venture capitalists in financing entrepreneurship. Copyright © 2013 John Wiley & Sons, Ltd.
Strength in numbers or guilt by association? Intragroup effects of female chief executive announcements
Authors: Dixon‐Fowler Heather R. , Ellstrand Alan E. , Johnson Jonathan L.
Published: January 2013

We predict that the media reports on femaleCEOsas a coherent group, whereas maleCEOsare treated as individuals by the media. We also suggest that the resulting investors' perceptions of group entitativity of female‐led firms may not only influence the succession event–performance relationship at the focal firm, but may also have a significant effect on the value of other female‐led companies. Results of a text analysis and an event study of appointments of femaleCEOsto Fortune 1000 firms provide support for these predictions. Copyright © 2013 John Wiley & Sons, Ltd.
Twin anemia–polycythemia sequence in a case of monoamniotic twins
Authors: Diehl W. , Glosemeyer P. , Tavares De Sousa M. , Hollwitz B. , Ortmeyer G. , Hecher K.
Published: January 2013

Twin anemia–polycythemia sequence (TAPS) complicates up to 6% of monochorionic diamniotic twin pregnancies, typically in the late second or third trimester. The presence of only a few and very small arteriovenous vascular anastomoses characterizes the underlying angioarchitecture at the chorionic plate in cases of TAPS. In monoamniotic twins, large vascular anastomoses can usually be seen at the placental vascular equator, and therefore one would not expect the development of TAPS in monoamniotic twins. We report a case of TAPS in a monoamniotic pregnancy at 26 + 5 weeks' gestation which responded favorably to fetoscopic laser coagulation of the small placental anastomoses, resolving severe anemia in one twin and polycythemia in the other. The pregnancy continued until 32 + 5 weeks, when worsening cord entanglement with increased resistance and the development of postsystolic notches in the umbilical artery of one twin prompted delivery by Cesarean section. There was only a moderate difference in neonatal hemoglobin concentrations, with the former polycythemic twin needing a single partial volume exchange transfusion. The postnatal course of the neonates was uneventful, according to their gestational age at birth. To our knowledge this is the first case report describing successful laser therapy for TAPS in monoamniotic twins. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
Candida tropicalis BPU1, a novel isolate from the rumen of the Malabari goat, is a dual producer of biosurfactant and polyhydroxybutyrate
Authors: Priji Prakasan , Unni K. N. , Sajith S. , Benjamin Sailas
Published: January 2013

This unique study reports a new strain (BPU1) of Candida tropicalis isolated from the rumen of the Malabari goat, showing dual production of biosurfactant and polyhydroxybutyrate. C. tropicalis strain BPU1, a facultative anaerobe, was tuned to become an aerobe in specially designed flask, the Benjamin flask. The puffy circular colonies were smooth, white‐to‐cream in colour, with pseudo‐filaments. The strain fermented glucose, sucrose, maltose and dextrose, but not lactose and cellulose. It assimilated (NH4)2SO4, peptone, glycine and arginine, but not NaNO3, as the nitrogen source. Interestingly, it utilized groundnut oil (up to 0.3%) in a specially designed basal mineral salt medium (BSM). Its capability for dual production of a biosurfactant and a polyhydroxybutyarate (PHB) was explored by various methods from the BSM–oil medium. Extracted biosurfactant from 6 day‐old culture was biochemically characterized as a complex of lipid and carbohydrate with an Rf value of 0.88 by thin layer chromatography. Its PHB production was confirmed by specific staining methods with Nile blue sulphate, Sudan black B and Sudan 3. Briefly, this first‐ever report gives ample physical evidence for the dual production of a glycolipid (biosurfactant) and PHB by C. tropicalis strain BPU1 on a specially designed medium, which would open up elaborate research on this yeast. Copyright © 2013 John Wiley & Sons, Ltd.
Solutions to Exercises
Authors: Minty Michiko G. , Zimmermann Frank
Published: January 2013

From (1.12) at a fixed location s we can write
$$x = \sqrt {2{I_x}{\beta _x}} \cos {\phi _x},$$
where φx includes the initial phase φ0 We then have
$$\begin{array}{*{20}{c}}{{{ \in }_{x}} = \frac{{\left\langle {{{x}^{2}}\left( s \right)} \right\rangle }}{{{{\beta }_{x}}\left( s \right)}}} \\{ = \int {d{{\phi }_{x}}d{{I}_{x}}2{{I}_{x}}{{{\cos }}^{2}}{{\phi }_{x}}\rho \left( {{{I}_{x}},{{\phi }_{x}}} \right)} } \\{ = \int {d{{\phi }_{x}}d{{I}_{x}}2{{I}_{x}}{{{\cos }}^{2}}{{\phi }_{x}}\rho \left( {{{I}_{x}}} \right)\frac{1}{{2\pi }}} } \\{ = \int {d{{I}_{x}}{{I}_{x}}\rho \left( {{{I}_{x}}} \right) = \left\langle {{{I}_{x}}} \right\rangle .} } \\\end{array}$$
Orbit Measurement and Correction
Authors: Minty Michiko G. , Zimmermann Frank
Published: January 2013

In practice, there are many uncertainties whose presence must be appreciated when correcting the beam orbit in both linear and circular accelerators. Such uncertainties include the variations in the electronic and/or mechanical centers of the beam position monitors (BPMs), in the magnetic center of the quadrupoles (inside which the position monitors are often mounted), or in the electromagnetic center of accelerating structures. Consider the case illustrated in Fig. 3.1.
Beam Manipulations in Photoinjectors
Authors: Minty Michiko G. , Zimmermann Frank
Published: January 2013

The design of an electron source is a challenging task. The designer must reconcile the contradictory requirements for a small emittances, a high charge, a high repetition rate, and, possibly, a high degree of beam polarization.
Antenatal manifestations of mitochondrial disorders
Authors: Tavares Mariana Vide , Santos Maria João , Domingues Ana Patrícia , Pratas João , Mendes Cândida , Simões Marta , Moura Paulo , Diogo Luísa , Grazina Manuela
Published: January 2013

Mitochondrial respiratory chain diseases are a heterogeneous group of pathologies caused by genetic alterations affecting mitochondrial energy production. Theoretically, this deficiency may lead to any symptoms, in any organ or tissue, at any age even before birth. The aim of our study was to identify the frequency and characterize antenatal manifestations identifying possible associations between mitochondrial disease and more specific and earlier manifestation. We retrospectively review the files of 44 paediatric subjects with genetic and biochemical alterations of respiratory chain identified in the first decade of life and compare data with a control group (n = 88). Our results show that maternal age was similar in both groups. The female gender was predominant in patients group. Gestational age at delivery was similar in both groups. Concerning birth weight, it was significantly lower (p = 0.001) in patients (2899.9 ± 538.3 vs. 3246.6 ± 460.2 g). Fifteen pregnancies of the patients group were considered abnormal. Our findings show that intrauterine growth restriction was the most frequent antenatal feature observed. Neonatal morbidity was significantly higher (fivefold) in patients (p < 0.001). The clinical findings are independent of the molecular defect type. Our results are preliminary and more studies are needed, in order to learn more about mitochondrial physiology and activity in embryological development for the assessment of mitochondrial disease progress in fetal life. However, the present work is a significant contribution, given the scarcity of information in this field.
Nonlinear optimal perturbations in a Couette flow: bursting and transition
Authors: Cherubini S. , De Palma P.
Published: January 2013

This paper provides the analysis of bursting and transition to turbulence in a Couette flow, based on the growth of nonlinear optimal disturbances. We use a global variational procedure to identify such optimal disturbances, defined as those initial perturbations yielding the largest energy growth at a given target time, for given Reynolds number and initial energy. The nonlinear optimal disturbances are found to be characterized by a basic structure, composed of inclined streamwise vortices along localized regions of low and high momentum. This basic structure closely recalls that found in boundary-layer flow (Cherubini et al., J. Fluid Mech., vol. 689, 2011, pp. 221–253), indicating that this structure may be considered the most ‘energetic’ one at short target times. However, small differences in the shape of these optimal perturbations, due to different levels of the initial energy or target time assigned in the optimization process, may produce remarkable differences in their evolution towards turbulence. In particular, direct numerical simulations have shown that optimal disturbances obtained for large initial energies and target times induce bursting events, whereas for lower values of these parameters the flow is directly attracted towards the turbulent state. For this reason, the optimal disturbances have been classified into two classes, the highly dissipative and the short-path perturbations. Both classes lead the flow to turbulence, skipping the phases of streak formation and secondary instability which are typical of the classical transition scenario for shear flows. The dynamics of this transition scenario exploits three main features of the nonlinear optimal disturbances: (i) the large initial value of the streamwise velocity component; (ii) the streamwise dependence of the disturbance; (iii) the presence of initial inclined streamwise vortices. The short-path perturbations are found to spend a considerable amount of time in the vicinity of the edge state (Schneider et al., Phys. Rev. E, vol. 78, 2008, 037301), whereas the highly dissipative optimal disturbances pass closer to the edge, but they are rapidly repelled away from it, leading the flow to high values of the dissipation rate. After this dissipation peak, the trajectories do not lead towards the turbulent attractor, but they spend some time in the vicinity of an unstable periodic orbit (UPO). This behaviour led us to conjecture that bursting events can be obtained not only as homoclinic orbits approaching the UPO, as recently found by van Veen & Kawahara (Phys. Rev. Lett., vol. 107, 2011, p. 114501), but also as heteroclinic orbits between the equilibrium solution on the edge and the UPO.
A thermo-mechanically consistent Burnett regime continuum flow equation without Chapman–Enskog expansion
Authors: Dadzie S. Kokou
Published: January 2013

Chapman–Enskog expansion is the orthodox approach to derive continuum flow models from Boltzmann’s kinetic equation for dilute gases. Beyond the Navier–Stokes–Fourier order these models, known as Burnett hydrodynamic-regime equations, violate a number of fundamental mechanical and thermodynamic principles in their original forms. This has generated a widely investigated problem in the kinetic theory of gases. In this short article, we derive a Burnett hydrodynamic-regime continuum model that is systematically consistent with all known mechanical and thermodynamic principles without using any series expansion. A close comparison with the conventional Burnett hydrodynamic set of equations is made and the linear stabilities around an equilibrium point under small perturbations are presented.
Flows in annuli with longitudinal grooves
Authors: Moradi H. V. , Floryan J. M.
Published: January 2013

Analysis of pressure losses in laminar flows through annuli fitted with longitudinal grooves has been carried out. The additional pressure gradient required in order to maintain the same flow rate in the grooved annuli, as well as in the reference smooth annuli, is used as a measure of the loss. The groove-induced changes can be represented as a superposition of a pressure drop due to a change in the average position of the bounding cylinders and a pressure drop due to flow modulations induced by the shape of the grooves. The former effect can be evaluated analytically while the latter requires explicit computations. It has been demonstrated that a reduced-order model is an effective tool for extraction of the features of groove geometry that lead to flow modulations relevant to drag generation. One Fourier mode from the Fourier expansion representing the annulus geometry is sufficient to predict pressure losses with an accuracy sufficient for most applications in the case of equal-depth grooves. It is shown that the presence of the grooves may lead to a reduction of pressure loss in spite of an increase of the surface wetted area. The drag-decreasing grooves are characterized by the groove wavenumber $M/ {R}_{1} $ being smaller than a certain critical value, where $M$ denotes the number of grooves and ${R}_{1} $ stands for the radius of the annulus. This number marginally depends on the groove amplitude and does not depend on the flow Reynolds number. It is shown that the drag reduction mechanism relies on the re-arrangement of the bulk flow that leads to the largest mass flow taking place in the area of the largest annulus opening. The form of the optimal grooves from the point of view of the maximum drag reduction has been determined. This form depends on the type of constraints imposed. In general, the optimal shape can be described using the reduced-order model involving only a few Fourier modes. It is shown that in the case of equal-depth grooves, the optimal shape can be approximated using a special form of trapezoid. In the case of unequal-depth grooves, where the groove depth needs to be determined as part of the optimization procedure, the optimal geometry, consisting of the optimal depth and the corresponding optimal shape, can be approximated using a delta function. The maximum possible drag reduction, corresponding to the optimal geometry, has been determined.
Nonlinear stability, bifurcation and vortical patterns in three-dimensional granular plane Couette flow
Authors: Alam Meheboob , Shukla Priyanka
Published: January 2013

The effects of three-dimensional (3D) perturbations, having wave-like modulations along both the streamwise and spanwise/vorticity directions, on the nonlinear states of five types of linear instability modes, the nature of their bifurcations and the resulting nonlinear patterns are analysed for granular plane Couette flow using an order-parameter theory which is an extension of our previous work on two-dimensional (2D) perturbations (Shukla & Alam, J. Fluid Mech., vol. 672, 2011b, pp. 147–195). The differential equations for modal amplitudes (the fundamental mode, the mean-flow distortion, the second harmonic and the distortion of the fundamental mode), up to cubic-order in perturbation amplitude, are solved using a spectral-based numerical technique, yielding an estimate of the first Landau coefficient that accounts for the leading-order nonlinear effect on finite-amplitude perturbations. In the near-critical regime of flows, we found evidence of mean-flow resonance, characterized by the divergence of the first Landau coefficient, that occurs due to the interaction/resonance between a linear instability mode and a mean-flow mode. The nonlinear solutions are found to appear via both pitchfork and Hopf bifurcations from the underlying linear instability modes, leading to supercritical nonlinear states of stationary and travelling wave solutions. The subcritical travelling wave solutions have also been uncovered in the linearly stable regimes of flow. It is shown that multiple nonlinear states of both stationary and travelling waves can coexist for a given parameter combination of mean density and Couette gap. The 3D nonlinear solutions persist for a range of spanwise wavenumbers up to ${k}_{z} = O(1)$ that originate from 2D instabilities which occur beyond a moderate value of the mean density. For purely 3D instabilities in dilute flows (having no analogue in 2D flows), the supercritical finite-amplitude solutions persist for a much larger range of spanwise wavenumber up to ${k}_{z} = O(10)$. For all instabilities, the vortical motion on the cross-stream plane has been characterized in terms of the fixed/critical points of the underlying flow field: saddles, nodes (sources and sinks) and vortices have been identified. While the cross-stream velocity field for supercritical solutions in dilute flows contains nodes and saddles, the subcritical solutions are dominated by large-scale vortices in the background of saddle-node-type motions. The latter type of flow pattern also persists at moderate densities in the form of supercritical nonlinear solutions that originate from the dominant 2D instability modes for which the vortex appears to be driven by two nearby saddles. The location of this vortex is found to be correlated with the local maxima of the streamwise vorticity.
Invariants of the reduced velocity gradient tensor in turbulent flows
Authors: Cardesa J. I. , Mistry D. , Gan L. , Dawson J. R.
Published: January 2013

In this paper we examine the invariants $p$ and $q$ of the reduced $2\times 2$ velocity gradient tensor (VGT) formed from a two-dimensional (2D) slice of an incompressible three-dimensional (3D) flow. Using data from both 2D particle image velocimetry (PIV) measurements and 3D direct numerical simulations of various turbulent flows, we show that the joint probability density functions (p.d.f.s) of $p$ and $q$ exhibit a common characteristic asymmetric shape consistent with $\langle pq\rangle \lt 0$. An explanation for this inequality is proposed. Assuming local homogeneity we derive $\langle p\rangle = 0$ and $\langle q\rangle = 0$. With the addition of local isotropy the sign of $\langle pq\rangle $ is proved to be the same as that of the skewness of $\partial {u}_{1} / \partial {x}_{1} $, hence negative. This suggests that the observed asymmetry in the joint p.d.f.s of $p{{\ndash}}q$ stems from the universal predominance of vortex stretching at the smallest scales. Some advantages of this joint p.d.f. compared with that of $Q{{\ndash}}R$ obtained from the full $3\times 3$ VGT are discussed. Analysing the eigenvalues of the reduced strain-rate matrix associated with the reduced VGT, we prove that in some cases the 2D data can unambiguously discriminate between the bi-axial (sheet-forming) and axial (tube-forming) strain-rate configurations of the full $3\times 3$ strain-rate tensor.