bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel antennas for ultra‐wideband communications
Authors: Fortino N. , Kossiavas G. , Dauvignac J. Y. , Staraj R. 
Published: March 2004

AbstractTwo novel antennas for UWB communications, both inspired from bowtie and triangular patch structures, are presented and tested. This paper proposes their study and optimization in order to cover the new WPAN standard and facilitate their integration on communication devices. This work has then been centered around three specific goals: wide bandwidth, minimum size, and low cost. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 166–169, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20082
A multi‐wideband microstrip antenna designed by the square‐curve fractal technique
Authors: Siakavara K. , Tsaldaris F. 
Published: March 2004

AbstractA novel microstrip antenna is synthesized by the square‐curve fractal algorithm. The generator element is a rectangular microstrip ring and the antenna realizes multiband operation. This performance can also be achieved by using other fractal algorithms found in the literature. However, in all cases the frequency bandwidth is very narrow. In the present work, bandwidths up to 12% are achieved by the use of double feed and one pin. The antenna's additional figure of merit is its ability to be driven only by probes and without the need of any matching circuit. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 180–185, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20086
Analysis of RF scattering parameters and noise and power performances of RF‐power MOS in 0.15‐μm RF cmos technology for RF SOC applications
Authors: Lin Yo‐Sheng 
Published: March 2004

AbstractIn this paper, we demonstrate an analysis of the effects of transconductancegmon the kink phenomenon of the scattering parametersS11,S22,S21, andS12of RF powern‐MOSFETs in 0.15‐μm RF CMOS technology for RF SOC applications. It is found that either the increase of the device's width or the increase of the gate‐source voltageVGS(when its correspondinggmis smaller than the maximumgm) and the decrease of the measurement temperature can enhance the kink effect of bothS11andS22due to the increase ofgm. The anomalous dip in theS11andS22of RF powern‐MOSFETs can also be interpreted in terms of poles and zeros. In addition, we conclude that a device with larger gate width or largergmexhibits better RF noise and power performances because of higher gain (orgm) and the lighter effect of the parasitic extrinsic elements. The present analyses enable RF engineers to understand more deeply the behaviors ofSparameters, RF noise and power performances of RF power MOSFETs, and hence is helpful for them to create a fully scalable wideband RF‐power MOS or CMOS model for RF SOC applications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 191–196, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20089
A CPW‐fed broadband slot antenna with linear taper
Authors: Niu Jun‐Wei , Zhong Shun‐Shi 
Published: March 2004

AbstractA new coplanar waveguide (CPW)‐fed broadband printed slot antenna is presented. The impedance bandwidth is greatly increased by using a linear taper. The test antenna's impedance bandwidth of −10‐dB return loss reaches 40% with low cross‐polarization level. The impedance characteristics and radiation patterns of the slot antenna with different sizes of tapers are presented. The simulated results agree well with the measured ones. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 218–221, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20098
Planar‐fed compact circular‐polarised microstrip antenna with triangular‐slot loading
Authors: Elsdon M. , Sambell A. , Gao S. C. , Qin Y. 
Published: March 2004

AbstractA planar‐fed circular‐polarised (CP) microstrip patch antenna is presented and discussed. It is demonstrated that embedding four right‐angle triangular slots in a nearly square patch antenna and exciting with an offset inset feed, size reduction of up to 43% can be achieved while still maintaining planar impedance matching. The proposed design shows no significant reduction in the axial‐ratio bandwidth and has relaxed manufacturing tolerances. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 226–228, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20100
Stability and noise performance of resistively loaded microwave amplifiers
Authors: Post John E. 
Published: March 2004

AbstractResistive loading is a classic technique to guarantee the unconditional stability of microwave amplifiers at the operating frequency, but the amplifier is potentially unstable at other frequencies. A technique is proposed to predict microwave amplifier stability at all frequencies by solving for the stability parameter of the overall cascaded resistor/transistor network. Eight different stabilizing networks are investigated and shown to have very different stabilizing effects as a function of frequency. A method to determine the effect of resistive stabilization on amplifier‐noise performance is presented. These results allow the designer to choose a stabilizing resistor network that provides the best compromise between gain, noise, and stability for a desired application. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 228–231, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20101
Decrease of sidelobe energy by shifts in original training images for synthetic aperture radar image recognition
Authors: Chen Chewei , Chen Chulung 
Published: March 2004

AbstractFor synthetic aperture radar (SAR) image recognition, correlation filters were designed in our previous research by the nonzero‐ order joint‐transform correlator. Training images were placed at the presumed center in order to synthesize the reference function. However, this could not guarantee that the average cross correlation energy would be minimum. To improve this, training images are shifted pixel by pixel from left to right and top to bottom in this study. We synthesize the reference functions, hoping to find lower cross‐correlation energy. Finally, we obtain sharper correlation peaks and less sidelobe energy, which can increase the recognition ability. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 241–244, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20105
Optimization of parthenogenetic activation protocol in porcine
Authors: Lee Jang‐Won , Tian X. Cindy , Yang Xiangzhong 
Published: March 2004

AbstractThe effects of the electrical field strengths, number of pulses, and post‐activation media on chromatin conformation and parthenogenetic development were studied to optimize the activation protocol for porcine nuclear transfer. In experiment 1, electrical field strengths were examined. Oocytes were subjected to square direct current pulses at output voltages of 1.2, 1.7, 2.2, and 2.7 kV/cm for 1 × 30 μsec. The voltage resulting from experiment 1 was 2.2 kV/cm, in which 50.0% of activated oocytes developed to blastocysts in vitro. In experiment 2, the influence of 1, 2, and 3 pulses on blastocyst development was tested using field strengths and post‐activation medium described in experiment 1. Oocytes activated by a single 30 μsec pulse of 2.2 kV/cm DC yielded a higher blastocyst rate (56.3%) than oocytes activated by 2 or 3 pulses (<42.5%). In experiment 3 and 4, we investigated the effects of cytochalasin B (CB), cycloheximide (CH), and CB + CH on nuclear development stages and parthenogenetic development following a single 30 μsec pulse of 2.2 kV/cm DC. The percentage of activated oocytes was not different among CB (93.3%), CB + CH (98.3%), control (80.0%), and CH (80.0%) groups 12 hr after activation. Treatment with CB (57.5%) or CB + CH (53.8%) enhanced the blastocyst rate compared with other groups, CH (23.8%) treated‐ and control group (18.8%). The results demonstrated that a single 30 μsec pulse of 2.2 kV/cm DC followed by culturing in post‐activation medium with CB for 5 hr were effective parameters for parthenogenetic activation and blastocyst formation of in vitro matured porcine oocytes which suggests that a single calcium rise is sufficient to activate pig oocytes and to achieve high rate of blastocyst development. Mol. Reprod. Dev. 68: 51–57, 2004. © 2004 Wiley‐Liss, Inc.
Specific gene silencing in the pre‐implantation stage mouse embryo by an siRNA expression vector system
Authors: Haraguchi Seiki , Saga Yumiko , Naito Kunihiko , Inoue Hirokazu , Seto Akira 
Published: March 2004

AbstractRecently, small interfering RNAs (siRNAs) have become a powerful and widely used tool for the analysis of gene function in mammalian cells. Here we report that the microinjection of an siRNA expression vector into the nucleus is an efficient and powerful method of specific gene silencing in pre‐implantation mouse embryos. We used this method to examine the expression of two genes EGFP and Oct4. Vectors encoding siRNAs targeted against EGFP or Oct4 were injected into the pronucleus or nucleus of zygotes, which were then cultured until the blastocyst stage. When the effects of RNAi were examined in blastocyst stage eggs, there was robust inhibition of the gene product in a concentration‐dependent manner at both the mRNA and the protein level. The expression of other endogenous genes was not affected, showing the specificity of the vector‐mediated RNAi. In addition, this method was effective for inhibiting maternally expressed mRNA. To demonstrate that RNAi of Oct4 induced a similar phenotype to that of Oct4‐null embryos, the blastocysts were further cultured in ES medium. After the fourth day of culture, the embryos either had outgrown only a layer of trophoblast cells or showed developmental arrest at the blastocyst stage (>90%). Moreover, concomitant with Oct4 suppression at the blastocyst stage, we observed inhibition of Fgf4, a gene that is known to be induced downstream of Oct4 expression. Taken together, these results demonstrate that the use of siRNA expression vector is a powerful way to achieve gene silencing in the pre‐implantation stage embryo. Mol. Reprod. Dev. 68: 17–24, 2004. © 2004 Wiley‐Liss, Inc.
Bovine oocyte cytoplasm supports nuclear remodeling but not reprogramming of murine fibroblast cells
Authors: Park Sang‐Hyun , Shin Mi‐Ra , Kim Nam‐Hyung 
Published: March 2004

AbstractNuclear transfer (NT) is used to elucidate fundamental biological issues such as reversibility of cell differentiation and interactions between the cytoplasm and nucleus. To obtain an insight into interactions between the somatic cell nucleus and oocyte cytoplasm, nuclear remodeling and gene expression were compared in bovine oocytes that had received nuclei from bovine and mouse fibroblast cells. While the embryos that received nuclei from bovine fibroblast cells developed into blastocysts, those that received nuclei from mouse fibroblasts did not develop beyond the 8‐cell stage. Similar nuclear remodeling procedures were observed in oocytes reconstructed with mouse and bovine fibroblast cells. Foreign centrosomes during NT were introduced into embryos reconstructed with both fibroblast cell types. A number of housekeeping mouse genes (hsp70, bax, and glt‐1) were abnormally expressed in embryos that had received nuclei from mouse fibroblast cells. However, development‐related genes, such as Oct‐4 and E‐cad, were not expressed. The results collectively suggest that the bovine oocyte cytoplasm supports nuclear remodeling, but not reprogramming of mouse fibroblast cells. Mol. Reprod. Dev. 68: 25–34, 2004. © 2004 Wiley‐Liss, Inc.
Enriched gonadal migration of donor‐derived gonadal primordial germ cells by immunomagnetic cell sorting in birds
Authors: Kim Jin Nam , Kim Mi A , Park Tae Sub , Kim Duk Kyung , Park Hyun Jeong , Ono Tamao , Lim Jeong Mook , Han Jae Yong 
Published: March 2004

AbstractThis study was conducted to evaluate whether immunomagnetic treatment could improve the retrieval and migration capacity of avian gonadal primordial germ cells (gPGCs) collected from gonads in 5.5‐day‐old chick and 5‐day‐old quail embryos, respectively. Collected gPGCs were loaded into a magnetic‐activated cell sorter (MACS) after being conjugated with specific gPGC antibodies and either MACS‐treated or non‐treated cells in each species were subsequently transferred to the recipient embryos. MACS treatment significantly (P < 0.05) increased the population ratio of gPGCs in gonadal cells retrieved (0.74 to 33.4% in the chicken and 2.68 to 45.1% in the quail). This was due to decreased number of non‐gPGCs in total cell population. MACS treatment further enhanced gonadal migration of gPGCs transferred in both species (10% vs. 80–85% in the chicken and 10–15% vs. 70–80% in the quail). Increase in the number of microinjected cells up to 600 cells/embryo did not eliminate such promoting effect. In conclusion, MACS treatment greatly increased the population ratio of avian gPGCs in gonadal cells, resulting improved gonadal migration in recipient embryos. Mol. Reprod. Dev. 68: 81–87, 2004. © 2004 Wiley‐Liss, Inc.
Effects of oxidative stress and inhibitors of the pentose phosphate pathway on sexually dimorphic production of IFN‐τ by bovine blastocysts
Authors: Kimura K. , Spate L.D. , Green M.P. , Roberts R.M. 
Published: March 2004

AbstractBovine interferon‐tau (IFN‐τ), the anti‐luteolytic factor secreted by conceptuses of pecoran ruminants, is a product of autosomal genes, yet in vitro produced (IVP) female expanded blastocysts (EB) secrete about twice as much IFN‐τ as males. Two possible explanations have been tested here. One is that embryos of one sex are differentially susceptible to oxidative stress. The second is that female EB produce more IFN‐τ because pentose‐phosphate pathway (PPP) activity is elevated as a result of delayed X‐chromosome inactivation. IVP bovine zygotes were cultured to the 8‐cell stage and placed under conditions designed either to promote oxidative stress (±H2O2; 20 vs. 5% O2), or to inhibit glucose 6‐phosphate dehydrogenase (G6PDH) activity (addition of dehydroepiandrosterone, DHEA or 6‐aminonicotinamide, 6‐AN to the medium). At day 8, blastocysts were cultured individually for a further 48 hr to assess IFN‐τ production, and embryo sex determined retrospectively. Blastocyst numbers were reduced (P < 0.05) and their continued development impaired (P < 0.05) in presence of H2O2 (200 μM) and 20% O2, but neither IFN‐τ production nor sexually dimorphic expression of IFN‐τ were affected. IFN‐τ production was reduced, particularly in females (P < 0.05), and sexual dimorphic differences in production were lost in the presence of both DHEA (100 μM) and 6‐AN (1 μM). In the case of 6‐AN, these effects were achieved without a significant decline in blastocyst developmental progression, quality, or cell number. The data suggest that the higher production of IFN‐τ by female EB is an indirect outcome of the increased activity of the oxidative arm of the PPP pathway. Mol. Reprod. Dev. 68: 88–95, 2004. © 2004 Wiley‐Liss, Inc.
Primordial germ cells: what does it take to be alive?
Authors: Tres Laura L. , Rosselot Carolina , Kierszenbaum Abraham L. 
Published: March 2004

AbstractSpecification of primordial germ cells (PGCs) in the proximal epiblast enables about 45 founder PGCs clustered at the base of the allantoic bud to enter the embryo by active cell movement. Specification of the PGC lineage depends on paracrine signals derived from the somatic cell neighbors in the extraembryonic ectoderm. Secretory bone morphogenetic proteins (BMP) 4, BMP8b, and BMP2 and components of the Smad signaling pathway participate in the specification of PGCs. Cells in the extraembryonic ectoderm induce expression of the gene fragilis in the epiblast in the presence of BMP4, targeting competence of PGCs. The fragilis gene encodes a family of transmembrane proteins presumably involved in homotypic cell adhesion. As PGCs migrate throughout the hindgut, they express nanos3 protein. In the absence of nanos3 gene expression, no germ cells are detected in ovary and testis. During migration and upon arrival at the genital ridges, the population of PGCs is regulated by a balanced proliferation/programmed cell death or apoptosis. Paracrine and autocrine mechanisms, involving transforming growth factor‐β1 and fibroblast growth factors exert stimulatory or inhibitory effects on PGCs proliferation, modulated in part by the membrane‐bound form of stem cell factor. Apoptosis requires the participation of the pro‐apoptotic family member Bax, whose activity is balanced by the anti‐apoptotic family member Bcl21/Bcl‐x. In addition, a loss of cell‐cell contacts in vitro results in the apoptotic elimination of PGCs. It needs to be determined whether apoptosis is triggered by a failure of PGC to establish and maintain appropriate cell‐cell contacts with somatic cells or whether undefined survival factors released by adjacent somatic cells cannot reach physiological levels to satisfy needs of the expanding population of PGCs. Mol. Reprod. Dev. 68: 1–4, 2004. © 2004 Wiley‐Liss, Inc.
Strain localization in sand: an overview of the experimental results obtained in Grenoble using stereophotogrammetry
Authors: Desrues Jacques , Viggiani Gioacchino 
Published: March 2004

AbstractExperimental results are presented from the extensive program of drained plane strain compression tests on sand carried out in Grenoble over the last two decades. Systematic analysis of photographs of the deforming specimen allowed for measuring deformations and determining strain fields throughout the test, that is: prior to, at, and after the onset of strain localization. The principles, details and accuracy of the procedure are described, as well as its suitability to properly depict the patterns of deformation. Findings concerning the occurrence and progression of strain localization are discussed. The issues of shear band orientation and thickness are addressed, as well as temporary and persistent complex localization patterns, and the volumetric behaviour inside a band after its formation. The influence of such variables as initial state of the sand (effective stress and relative density), specimen size and slenderness, as well as grain size, is discussed. Copyright © 2004 John Wiley & Sons, Ltd
Minimum‐cost dynamic flows: The series‐parallel case
Authors: Klinz Bettina , Woeginger Gerhard J. 
Published: March 2004

AbstractA dynamic network consists of a directed graph with capacities, costs, and integral transit times on the arcs. In the minimum‐cost dynamic flow problem (MCDFP), the goal is to compute, for a given dynamic network with source s, sink t, and two integers v and T, a feasible dynamic flow from s to t of value v, obeying the time bound T, and having minimum total cost. MCDFP contains as subproblems the minimum‐cost maximum dynamic flow problem, where v is fixed to the maximum amount of flow that can be sent from s to t within time T and the minimum‐cost quickest flow problem, where is T is fixed to the minimum time needed for sending v units of flow from s to t. We first prove that both subproblems are NP‐hard even on two‐terminal series‐parallel graphs with unit capacities. As main result, we formulate a greedy algorithm for MCDFP and provide a full characterization via forbidden subgraphs of the class 𝒢 of graphs, for which this greedy algorithm always yields an optimum solution (for arbitrary choices of problem parameters). 𝒢 is a subclass of the class of two‐terminal series‐parallel graphs. We show that the greedy algorithm solves MCDFP restricted to graphs in 𝒢 in polynomial time. © 2004 Wiley Periodicals, Inc.
Low‐connectivity network design on series‐parallel graphs
Authors: Raghavan S. 
Published: March 2004

AbstractNetwork survivability is a critical issue for modern fiber‐optic telecommunication networks. Networks with alternate routes between pairs of nodes permit users to communicate in the face of equipment failure. In this paper, we consider the following low‐connectivity network design (LCND) problem: Given a graph G = (N, E) and a connectivity requirement di ∈ {0, 1, 2} for each node and edge costs ce for each edge e ∈ E, design a minimum‐cost network that contains at least dst = min{ds, dt} disjoint paths between nodes s and t. We present linear‐time algorithms for both node‐ and edge‐connectivity versions of the problem on series‐parallel graphs. Due to the sparsity of telecommunications networks, this algorithm can be applied to obtain partial solutions and decompositions that may be embedded in a heuristic solution procedure as well as exact solution algorithms for the problem on general graphs. © 2004 Wiley Periodicals, Inc.
The Ring Star Problem: Polyhedral analysis and exact algorithm
Authors: Labbé Martine , Laporte Gilbert , Martín Inmaculada Rodríguez , González Juan José Salazar 
Published: March 2004

AbstractIn the Ring Star Problem, the aim is to locate a simple cycle through a subset of vertices of a graph with the objective of minimizing the sum of two costs: a ring cost proportional to the length of the cycle and an assignment cost from the vertices not in the cycle to their closest vertex on the cycle. The problem has several applications in telecommunications network design and in rapid transit systems planning. It is an extension of the classical location–allocation problem introduced in the early 1960s, and closely related versions have been recently studied by several authors. This article formulates the problem as a mixed‐integer linear program and strengthens it with the introduction of several families of valid inequalities. These inequalities are shown to be facet‐defining and are used to develop a branch‐and‐cut algorithm. Computational results show that instances involving up to 300 vertices can be solved optimally using the proposed methodology. © 2004 Wiley Periodicals, Inc.
The 2‐path network problem
Authors: Dahl Geir , Johannessen Bjarne 
Published: March 2004

AbstractGiven a graph with nonnegative edge weights and a set D of node pairs, the 2‐path network problem requires a minimum weight set of edges such that the induced subgraph contains a path with one or two edges connecting each pair in D. The problem is NP‐hard. We present two integer programming models for the problem and study properties of associated polytopes, including cutting planes. Two approximation algorithms are suggested and analyzed. Some computational experience is reported. © 2004 Wiley Periodicals, Inc.
Do school accountability systems make it more difficult for low‐performing schools to attract and retain high‐quality teachers?
Authors: Clotfelter Charles T. , Ladd Helen F. , Vigdor Jacob L. , Diaz Roger Aliaga 
Published: March 2004

AbstractAdministrative data from North Carolina are used to explore the extent to which that state's relatively
sophisticated school‐based accountability system has exacerbated the challenges that schools serving
low‐performing students face in retaining and attracting high‐quality teachers. Most clear are the
adverse effects on retention rates, and hence on teacher turnover, in such schools. Less clear is the extent to
which that higher turnover has translated into a decline in the average qualifications of the teachers in the
low‐performing schools. Other states with more primitive accountability systems can expect even greater
adverse effects on teacher turnover in low‐performing schools. © 2004 by the Association for Public
Policy Analysis and Management.