Distribution by Scientific Domains

Kinds of Antenna

  • array antenna
  • biconical antenna
  • circular patch antenna
  • dipole antenna
  • dual-band antenna
  • horn antenna
  • light-harvesting antenna
  • mhz antenna
  • microstrip antenna
  • microstrip patch antenna
  • monopole antenna
  • patch antenna
  • proposed antenna
  • reader antenna
  • reflector antenna
  • rfid tag antenna
  • slot antenna
  • tag antenna

  • Terms modified by Antenna

  • antenna analysis
  • antenna application
  • antenna array
  • antenna bandwidth
  • antenna complex
  • antenna configuration
  • antenna design
  • antenna element
  • antenna gain
  • antenna length
  • antenna performance
  • antenna size
  • antenna structure
  • antenna system

  • Selected Abstracts


    R.S. Pappa
    First page of article [source]

    Efficient high gain with low sidelobe level antenna structures using circular array of square parasitic patches on a superstrate layer

    R. K. Gupta
    Abstract This article proposes efficient high gain with low sidelobe level (SLL) antenna structures using circular array of square parasitic patches (CASPPs) for wireless applications. The antenna structure consists of a microstrip antenna that feeds a CASPP fabricated on a low cost FR4 superstrate. The patches on superstrate are suspended in air at about ,o/2. The structure with 19-element CASPPs is designed, fabricated, and tested. The measured VSWR is <2 over 5.725,5.875 GHz frequency band. The antenna with a single square patch provides a gain of 12.6 dB; whereas, the antenna with 19-element CASPPs provides a gain of 18.3 dB with 93.4% efficiency, SLL of ,26.1 dB, and front to back lobe ratio of >20 dB. Antenna with CASPPs on finite ground requires 25% less ground plane size as compared to planar array. The proposed structure can be packaged inside an application platform. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2812,2817, 2010; View this article online at DOI 10.1002/mop.25613 [source]

    A novel internal antenna with high gain for wireless phone

    Ying Liu
    Abstract A novel internal antenna for synchronous code division multiple access band wireless phone is presented. Traditional internal antenna is monopole or Planar Inverted-F Antenna, which have no gain high enough in the limited space in phone. The proposed antenna is composed of two antenna elements with equal magnitude and 180° phase difference, to assure voice quality with high gain. The measured maximum gain is 2.69 dBi and maximum efficiency is 70.1% in the frequency band 450,470 MHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2112,2114, 2007; Published online in Wiley InterScience ( DOI 10.1002/mop.22708 [source]

    Supermassive black hole merger rates: uncertainties from halo merger theory

    Adrienne L. Erickcek
    ABSTRACT The merger of two supermassive black holes is expected to produce a gravitational-wave signal detectable by the Laser Interferometer Space Antenna(LISA). The rate of supermassive-black-hole mergers is intimately connected to the halo merger rate, and the extended Press-Schechter (EPS) formalism is often employed when calculating the rate at which these events will be observed by LISA. This merger theory is flawed and provides two rates for the merging of the same pair of haloes. We show that the two predictions for the LISA supermassive-black-hole-merger event rate from EPS merger theory are nearly equal because mergers between haloes of similar masses dominate the event rate. An alternative merger rate may be obtained by inverting the Smoluchowski coagulation equation to find the merger rate that preserves the Press,Schechter halo abundance, but these rates are only available for power-law power spectra. We compare the LISA event rates derived from the EPS merger formalism to those derived from the merger rates obtained from the coagulation equation and find that the EPS LISA event rates are 30 per cent higher for a power spectrum spectral index that approximates the full , cold dark matter result of the EPS theory. [source]

    A Mechanically Interlocked [3]Rotaxane as a Light-Harvesting Antenna: Synthesis, Characterization, and Intramolecular Energy Transfer

    Jie-Yu Wang
    Abstract Mimicking photosynthesis: The concept of light-harvesting by using a mechanically interlocked [3]rotaxane is developed through synthesis and characterization. Our results provide a new candidate for light-harvesting systems and also open up the possibility of creating intelligent or controllable energy-collecting machines (see figure). A mechanically interlocked light-harvesting system [3]rotaxane A has been synthesized in high yield through Cu(I)-catalyzed azide,alkyne cycloaddition; the hexyl-substituted truxene units are introduced into the wheels as donors and an oligo(para -phenylenevinylene) (OPV) unit into the axis as the acceptor. The structure and the purity of [3]rotaxane A were confirmed by 1H and 13C,NMR spectroscopy and ESI HRMS. The azide,alkyne cycloaddition is demonstrated to be an efficient stoppering method in the synthesis of the rotaxane containing dibenzo[24]crown-8 and dibenzyl ammonium units. Detailed steady-state UV/Vis absorption, photoluminescent, and time-resolved fluorescence spectroscopy were performed to investigate the photophysical properties of [3]rotaxane A and its reference compounds in solution and as thin films. Even in dilute solution, efficient energy transfer from the truxene-functionalized wheels to the OPV-based axis, through the dibenzo[24]crown-8 and dibenzyl ammonium interaction, is observed in [3]rotaxane A. The unique topology of [3]rotaxane A not only efficiently promotes the intramolecular energy-transfer process, but also prevents intermolecular aggregation in the solid state. The new antenna system opens up the possibility of controllable light-harvesting molecular machines or other optoelectronic devices on the nanometer scale. [source]

    Quantitative method for pheromone delivery in studies of sensory adaptation of moth antennae

    Abstract A pheromone sprayer and an electroantennogram (EAG) are used to study sensory adaptation in the antennae of male obliquebanded leafrollers, Choristoneura rosaceana and oriental fruit moths, Grapholita molesta, to the main pheromone compounds (Z)-11-tetradecen-1-yl acetate (Z11-14:Ac) and (Z)-8-dodecen-1-yl acetate (Z8-12:Ac), respectively. The atomization of 0.125, 0.25, 0.5 or 1 ,L ethanol min,1 into the EAG air delivery tube at an airflow rate of 2 L min,1, with resultant concentrations of 6.25, 12.5, 25 or 50 × 10,5,L ethanol mL air,1, respectively, does not affect the EAG response of C. rosaceana or C. molesta after a 30-min exposure period. The atomization of 0.125 ,L min,1 of a solution of 8 mg Z11-14:Ac mL,1 ethanol into the EAG air delivery tube at an airflow rate of 2 L min,1, with a resultant concentration of 0.5 ng pheromone mL,1 air, reduces the EAG response of C. rosaceana by approximately 70% after a 15-min exposure period. An additional 15 min of exposure to pheromone does not result in increased sensory adaptation. Antennae recover 32% of the lost responsiveness when exposed to pheromone-free air for 15 min. The atomization of 0.125 ,L min,1 of a solution of 8 mg Z8-12:Ac mL,1 ethanol into the EAG air delivery tube at an airflow rate of 2 L min,1, with a resultant concentration of 0.5 ng pheromone mL,1 air, reduces the EAG response of C. molesta antenna by approximately 80% after a 15- or 30-min exposure period. The antennae of this species do not recover responsiveness when exposed to pheromone-free air for 15 min. [source]

    Surface-Grafted Multiporphyrin Arrays as Light-Harvesting Antennae to Amplify Photocurrent Generation

    Mitsuhiko Morisue Dr.
    Abstract Organized multiporphyrin arrays were developed on the conductive surface by a novel coordination-directed molecular architecture aiming at efficient photoelectric conversion. The basic strategy employs the mutual coordination of two imidazolylporphyrinatozinc(II) units to form a cofacial dimer. Thus, meso,meso -linked bis(imidazolylporphyrinatozinc) (Zn2(ImP)2) was organized onto imidazolylporphyrinatozinc on the gold substrate as a self-assembled monolayer. The organized Zn2(ImP)2 bearing allyl side chains was covalently linked by ring-closing olefin metathesis catalyzed with Grubbs catalyst. Alternating coordination/metathesis reactions allow the stepwise accumulation of multiporphyrin arrays on the gold electrode. A successive increase in absorption over a wide wavelength range occurred after each accumulation step of Zn2(ImP)2 on the gold electrode, and cathodic photocurrent generation was enhanced in the aqueous electrolyte system, containing viologen as an electron carrier. The significant increase of the photocurrent indicates that the multiporphyrin array works as a "light-harvesting antenna" on the gold electrode. [source]

    Development of an Accurate Positioning System Using Low-Cost L1 GPS Receivers

    Masayuki Saeki
    This system employs an inexpensive L1 GPS receiver and a small patch antenna. As these devices are very inexpensive and small, they can be attached to an array of sensor nodes of a wireless network sensing system. In the present study, we first develop a program that can be used to estimate the relative positions of receivers and evaluate its performance. Next, a number of experiments were conducted to assess the performance of the inexpensive L1 GPS receiver with a patch antenna. Compared to the results obtained using a sophisticated antenna, the present measurement system, which uses a patch antenna, is less accurate. However, the present system achieves an accuracy of 1,2 cm. This system can be used as a localization system for the sensor nodes or, because of its accuracy, as a displacement monitoring system. [source]

    Drosophila CtBP regulates proliferation and differentiation of eye precursors and complexes with Eyeless, Dachshund, Dan, and Danr during eye and antennal development

    Chinh Q. Hoang
    Abstract Specification factors regulate cell fate in part by interacting with transcriptional co-regulators like CtBP to regulate gene expression. Here, we demonstrate that CtBP forms a complex or complexes with the Drosophila melanogaster Pax6 homolog Eyeless (Ey), and with Distal antenna (Dan), Distal antenna related (Danr), and Dachshund to promote eye and antennal specification. Phenotypic analysis together with molecular data indicate that CtBP interacts with Ey to prevent overproliferation of eye precursors. In contrast, CtBP,dan,danr triple mutant adult eyes have significantly fewer ommatidia than CtBP single or dan,danr double mutants, suggesting that the CtBP/Dan/Danr complex functions to recruit ommatidia from the eye precursor pool. Furthermore, CtBP single and to a greater extent CtBP,dan,danr triple mutants affect the establishment and maintenance of the R8 precursor, which is the founding ommatidial cell. Thus, CtBP interacts with different eye specification factors to regulate gene expression appropriate for proliferative vs. differentiative stages of eye development. Developmental Dynamics 239:2367,2385, 2010. © 2010 Wiley-Liss, Inc. [source]

    The molecular receptive range of an olfactory receptor in vivo (Drosophila melanogaster Or22a)

    Daniela Pelz
    Abstract Understanding how odors are coded within an olfactory system requires knowledge about its input. This is constituted by the molecular receptive ranges (MRR) of olfactory sensory neurons that converge in the glomeruli of the olfactory bulb (vertebrates) or the antennal lobe (AL, insects). Aiming at a comprehensive characterization of MRRs in Drosophila melanogaster we measured odor-evoked calcium responses in olfactory sensory neurons that express the olfactory receptor Or22a. We used an automated stimulus application system to screen [Ca2+] responses to 104 odors both in the antenna (sensory transduction) and in the AL (neuronal transmission). At 10,2 (vol/vol) dilution, 39 odors elicited at least a half-maximal response. For these odorants we established dose-response relationships over their entire dynamic range. We tested 15 additional chemicals that are structurally related to the most efficient odors. Ethyl hexanoate and methyl hexanoate were the best stimuli, eliciting consistent responses at dilutions as low as 10,9. Two substances led to calcium decrease, suggesting that Or22a might be constitutively active, and that these substances might act as inverse agonists, reminiscent of G-protein coupled receptors. There was no difference between the antennal and the AL MRR. Furthermore we show that Or22a has a broad yet selective MRR, and must be functionally described both as a specialist and a generalist. Both these descriptions are ecologically relevant. Given that adult Drosophila use approximately 43 ORs, a complete description of all MRRs appears now in reach. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source]

    Pinocchio, a novel protein expressed in the antenna, contributes to olfactory behavior in Drosophila melanogaster

    Stephanie M. Rollmann
    Abstract Most organisms depend on chemoreception for survival and reproduction. In Drosophila melanogaster multigene families of chemosensory receptors and putative odorant binding proteins have been identified. Here, we introduce an additional distinct protein, encoded by the CG4710 gene, that contributes to olfactory behavior. Previously, we identified through P[lArB] -element mutagenesis a smell impaired (smi) mutant, smi21F, with odorant-specific defects in avoidance responses. Here, we show that the smi21F mutant also exhibits reduced attractant responses to some, but not all, of a select group of odorants. Furthermore, electroantennogram amplitudes are increased in smi21F flies. Characterization of flanking sequences of the P[lArB] insertion site, complementation mapping, phenotypic reversion through P -element excision, and expression analysis implicate a predicted gene, CG4710, as the candidate smi gene. CG4710 produces two transcripts that encode proteins that contain conserved cysteines and which are reduced in the smi21F mutant. Furthermore, in situ hybridization reveals CG4710 expression in the third antennal segment. We have named this gene of previously unknown function and its product "Pinocchio (Pino)". © 2005 Wiley Periodicals, Inc. J Neurobiol., 2005 [source]

    Effects of radio-transmitter antenna length on swimming performance of juvenile rainbow trout

    K. J. Murchie
    Abstract,,, Technological advances have lead to the production of micro radio-transmitters capable of being implanted in fish as small as c. 5 g. Although the actual tags are small, transmitters are equipped with long antennas that can increase drag and tangle in debris. We examined the effects of radio-transmitter antenna length on the swimming performance of juvenile rainbow trout, Oncorhynchus mykiss, (N = 156, mean mass = 34 g, mean fork length = 148 mm). Although we tested a variety of different antenna lengths up to a maximum of 300 mm, only the longest antenna significantly impaired swimming performance relative to control fish (P < 0.001). There was no difference in swimming performance between the sham (surgery, but no transmitter) and the control fish (handled, but no surgery), suggesting that the surgical procedure itself did not negatively affect the fish. Regression analysis, however, indicated that there was a significant decrease in swimming performance associated with increased antenna length (R2 = 0.11, P < 0.001). In addition, when held in laboratory tanks, fish with the three longest antennas (150, 225 and 300 mm) frequently became entangled with the standpipe. We suggest that researchers, under the guidance of the tag manufacturer, trim antennas to the shortest possible length required to detect fish in their specific study area. Antenna length is clearly an important issue for small fish, especially for species that inhabit complex habitats where antennas may become entangled, and where fish must attain speeds near limits of their swimming capacity. Resumen 1. Los avances tecnológicos han llevado a producir micro radio-trasmisores capaces de ser implantados en peces de muy pequeño tamaño (,5 g). Aunque las marcas actuales son pequeñas, los trasmisores están equipados con antenas largas que pueden llegar a enredarse en los restos de vegetación. Examinamos los efectos de la longitud de la antena sobre la rutina natatoria de juveniles de Oncorhynchus mykiss (n = 156, peso medio = 34 g, longitud furcal media = 148 mm). 2. Aunque analizamos varias longitudes de antena, hasta 300 mm, solamente las de mayor longitud alteraron la rutina natatoria en relación a los peces control (P < 0.001). No hubo diferencia en la rutina natatoria entre individuos bajo cirugía pero sin trasmisores respecto de los individuos control (manipulados pero sin cirugía) lo que sugiere que los procedimientos de cirugía no afectaron negativamente a los peces. Sin embargo, análisis de regresión indicaron un declive significativo en la rutina natatoria asociado a la longitud de la antena (R2 = 0.11, P < 0.001). Además, al ser mantenidos en tanques, los individuos con las tres antenas mas largas (150, 225, y 300 mm) frecuentemente se enredaron con las tuberías. 3. Sugerimos a los investigadores que, bajo la dirección de los productores de marcas y antenas, consideren el uso de las antenas más pequeñas que permitan detectar a los peces en sus respectivas áreas de estudio. La longitud de la antena es una cuestión importante para los pequeños peces, especialmente para especies en hábitats complejos donde las antenas pueden llegar a enredarse y donde los peces pueden alcanzar velocidades casi al limite de su capacidad natatoria. [source]

    Differential expression of antenna and core genes in Prochlorococcus PCC 9511 (Oxyphotobacteria) grown under a modulated light,dark cycle

    Laurence Garczarek
    The continuous changes in incident solar light occurring during the day oblige oxyphototrophs, such as the marine prokaryote Prochlorococcus, to modulate the synthesis and degradation rates of their photosynthetic components finely. How this natural phenomenon influences the diel expression of photosynthetic genes has never been studied in this ecologically important oxyphotobacterium. Here, the high light-adapted strain Prochlorococcus sp. PCC 9511 was grown in large-volume continuous culture under a modulated 12 h,12 h light,dark cycle mimicking the conditions found in the upper layer of equatorial oceans. The pcbA gene encoding the major light-harvesting complex showed strong diel variations in transcript levels with two maxima, one before the onset of illumination and the other near the end of the photoperiod. In contrast, the mRNA level of psbA (encoding the reaction centre II subunit D1), the monocistronic transcript of psbD (encoding D2) and the dicistronic transcript of psbDC were all tightly correlated with light irradiance, with a minimum at night and a maximum at noon. The occurrence of a second peak during the dark period for the monocistronic transcript of psbC (encoding one of the PS II core Chl a antenna proteins) suggested the involvement of post-transcriptional regulation. Differential expression of the external antenna and core genes may constitute a mechanism of regulation of the antenna size to cope with the excess photon fluxes that Prochlorococcus cells experience in the upper layer of oceans around midday. The 5, ends of all transcripts were mapped, and a conserved motif, 5,-TTGATGA-3,, was identified within the putative psbA and pcbA promoters. [source]

    Experiments on space diversity effect in MIMO channel transmission with maximum data rate of 1,Gbps in downlink OFDM radio access

    Hidekazu Taoka
    This paper presents experimental results on the space diversity effect in MIMO multiplexing/diversity with the target data rate up to 1,Gbps using OFDM radio access based on laboratory and field experiments including realistic impairments using the implemented MIMO transceivers with the maximum of four transmitter/receiver branches. The experimental results using multipath fading simulators show that at the frequency efficiency of less than approximately 2,bits/second/Hz, MIMO diversity using the space-time block code (STBC) increases the measured throughput compared to MIMO multiplexing owing to the high transmission space diversity effect. At a higher frequency efficiency than approximately 2--3,bits/second/Hz, however, MIMO multiplexing exhibits performance superior to that of MIMO diversity since the impairments using higher data modulation and a higher channel coding rate in MIMO diversity overcomes the space diversity effect. The results also show that the receiver space diversity effect is very effective in MIMO multiplexing for maximum likelihood detection employing QR-decomposition and the M-algorithm (QRM-MLD) signal detection. Finally, we show that the real-time throughput of 500,Mbps and 1,Gbps in a 100-MHz transmission bandwidth is achieved at the average received Eb/N0 per receiver antenna of approximately 8.0 and 14.0,dB using 16QAM modulation and Turbo coding with the coding rate of 1/2 and 8/9 respectively in 4-by-4 MIMO multiplexing in a real propagation environment. Copyright © 2006 AEIT. [source]

    A new broadband uniform accuracy doa estimator,

    Mohammad Ghavami
    Conventional estimators of the bearing angle suffer from different accuracies for different angles. In the method discussed in this letter, a set of two-dimensional digital filters are employed for beamforming. Each filter is called a fan filter and performs broadband characteristics. It will be shown analytically that the accuracy of the bearing estimation is strongly dependent to the angle of arrival in such a way that it is maximum in the broadside and minimum in the endfire of the antenna. We will derive a simple expression for calculating the number of coefficients necessary for beamforming with uniform accuracy. A set of filters is then designed according to this criteria. It will be demonstrated by computer simulations that in the presence of noisy broadband incoming signals, the estimation of different arriving angles is accomplished with almost the same accuracy and hence using this method a complex and separately sectored antenna wilt not be required. [source]

    Array antenna assisted doppler spread compensator for OFDM

    Minoru Okada
    This paper proposes a novel array-antenna-assisted Doppler spread compensator for orthogonal frequency division multiplexing (OFDM), which is sensitive to fast time-variation of the radio propagation channel. In the proposed compensator, a linear array antenna is installed on top of the vehicle. The compensator estimates the received signal at a certain point on the linear array antenna by using space domain interpolation. Because the relative position of the estimated receiving point with respect to the ground does not change during the effective symbol duration of an OFDM signal, the time variation due to the movement of the vehicle can be compensated for. Computer simulation shows that the compensator can compensate for the bit error rate performance degradation due to time-variation of the channel when the velocity of the vehicle is up to 180km/h and a two-element array antenna is used at the carrier frequency of 600 MHz. The bit error rate performance can be further improved by using a four-element array antenna. [source]

    Exploiting the short,term and long,term channel properties in space and time: Eigenbeamforming concepts for the BS in WCDMA

    Christopher Brunner
    The deployment of adaptive antennas at base stations considerably increases the spectral efficiency of wireless communication systems. To reduce the computational complexity and increase performance of space,time (ST) processing, processing may take place in reduced dimension, i. e., pre,filtering takes place which is related to linear estimation theory based on second order statistics. To this end, long,term and short,term channel estimates are integrated into specific Tx/Rx systems. In this article, we present a new ST rake structure for uplink reception in WCDMA which operates in reduced dimension. Accordingly, our approach combines short,term and long,term spatial and temporal channel properties using an eigenanalysis. By choosing dominant eigenbeams in time and space, the algorithm enhances interference suppression as well as spatial and temporal receive diversity. In contrast to previously introduced well,known receiver structures, the ST eigenrake inherently adapts to different propagation environments and achieves higher spectral efficiency than other receivers. This is illustrated by Monte,Carlo simulations. Then we extend the proposed concept to the downlink. The downlink eigenbeamformer improves closed,loop downlink diversity compared to other proposals in standardization (3GPP) which only exploit short,term channel properties. Even though the short,term feedback rate remains unchanged, additional antenna elements can be included to increase antenna and diversity gain. We also present a tracking solution to the downlink eigenbeamforming in WCDMA. To this end, we propose a distributed implementation of the eigenspace/,beam tracking at the mobile terminal and base station (BS), respectively. Moreover, the specific nature of the deployed tracking scheme offers an advantageous feedback signalling. [source]

    Origin of the novel chemoreceptor Aesthetasc "Y" in Ostracoda: morphogenetical thresholds and evolutionary innovation

    Tomonari Kaji
    SUMMARY The morphology and developmental processes of the two types of ostracod chemoreceptors, the Aesthetasc "Y" and the "Grouped setae," were compared. Cypridoidea and Pontocypridoidea, belonging to Cypridocopina, have a large baseball bat-like seta as an autapomorphic character on the second antenna, whereas most ostracod taxa with plesiomorphic characters bear "Grouped setae" consisting of multiple setae on the second antenna. Their budding positions, morphology, and ontogenetic changes were compared, and our deduction is that the Aesthetasc "Y" originated from "Grouped setae-like" organ in the Paleozoic. The morphogenetic processes in the molting period of these chemoreceptors were compared at the cellular level. The observations suggest that the "Grouped setae" are formed by hypodermal cells and share sheath cells corresponding to those of the Aesthetasc "Y" as a common constraint in the molting process of setae. We conclude that modification of the morphogenetic processes in the molting period of the "Grouped setae" gave rise to the Aesthetasc "Y" as a novel organ in the evolutionary pathway of the Ostracoda. [source]

    Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroides

    FEBS JOURNAL, Issue 7 2002
    Francesco Francia
    The core complex of Rhodobacter sphaeroides is formed by the association of the light-harvesting antenna 1 (LH1) and the reaction center (RC). The PufX protein is essential for photosynthetic growth; it is located within the core in a 1 : 1 stoichiometry with the RC. PufX is required for a fast ubiquinol exchange between the QB site of the RC and the Qo site of the cytochrome bc1 complex. In vivo the LH1,PufX,RC complex is assembled in a dimeric form, where PufX is involved as a structural organizer. We have modified the PufX protein at the N and the C-terminus with progressive deletions. The nine mutants obtained have been characterized for their ability for photosynthetic growth, the insertion of PufX in the core LH1,RC complex, the stability of the dimers and the kinetics of flash-induced reduction of cytochrome b561 of the cytochrome bc1 complex. Deletion of 18 residues at the N-terminus destabilizes the dimer in vitro without preventing photosynthetic growth. The dimer (or a stable dimer) does not seem to be a necessary requisite for the photosynthetic phenotype. Partial C-terminal deletions impede the insertion of PufX, while the complete absence of the C-terminus leads to the insertion of a PufX protein composed of only its first 53 residues and does not affect the photosynthetic growth of the bacterium. Overall, the results point to a complex role of the N and C domains in the structural organization of the core complex; the N-terminus is suggested to be responsible mainly for dimerization, while the C-terminus is thought to be involved mainly in PufX assembly. [source]

    Time-resolved fluorescence analysis of the recombinant photosystem II antenna complex CP29

    FEBS JOURNAL, Issue 2 2001
    Effects of zeaxanthin, phosphorylation
    Nonradiative dissipation of excitation energy is the major photoprotective mechanism in plants. The formation of zeaxanthin in the antenna of photosystem II has been shown to correlate with the onset of nonphotochemical quenching in vivo. We have used recombinant CP29 protein, over-expressed in Escherichia coli and refolded in vitro with purified pigments, to obtain a protein indistinguishable from the native complex extracted from thylakoids, binding either violaxanthin or zeaxanthin together with lutein. These recombinant proteins and the native CP29 were used to measure steady-state chlorophyll fluorescence emission and fluorescence decay kinetics. We found that the presence of zeaxanthin bound to CP29 induces a ,,35% decrease in fluorescence yield with respect to the control proteins (the native and zeaxanthin-free reconstituted proteins). Fluorescence decay kinetics showed that four components are always present but lifetimes (,) as well as relative fluorescence quantum yields (rfqy) of the two long-lived components (,3 and ,4) are modified by the presence of zeaxanthin. The most relevant changes are observed in the rfqy of ,3 and in the average lifetime (, 2.4 ns with zeaxanthin and 3.2,3.4 ns in the control proteins). When studied in vitro, no significant effect of acidic pH (5.2,5.3) is observed on chlorophyll a fluorescence yield or kinetics. The data presented show that recombinant CP29 is able to bind zeaxanthin and this protein-bound zeaxanthin induces a significant quenching effect. [source]

    Variability of the photosynthetic antenna of a Pelodictyon clathratiforme population from a freshwater holomictic pond

    Frederic B. Gich
    Abstract A population of the green sulfur bacterium Pelodictyon clathratiforme was monitored during the stratification period of Coromina Lake, a freshwater, holomictic pond of the Banyoles lacustrine area (Girona, NE Spain). The chromatographic analysis of this population revealed the presence of a wide variety of both bacteriochlorophyll (BChl) d and BChl c homologues. Isolation of chlorosomes from cultured Pelodictyon cells and their further analysis by steady-state fluorescence indicated that, although both pigment were present in chlorosomes, only BChl c gave rise to an emission signal, suggesting a fast energy transfer from BChl d to BChl c. Likewise, chlorosomes isolated from natural samples were significantly larger (60,70 nm in width and 115,120 nm in length) than those isolated from cells grown in laboratory under optimal light conditions (48±6.8 nm and 100±15.8 nm in width and length, respectively). The potential role of heterogeneous BChl c - and BChl d -containing chlorosomes and the differences in chlorosome size measured are discussed in terms of the severe light limitation (available light intensity <0.1 ,mol photons m,2 s,1 at the bacterial plate) under which the population subsisted during the study period. [source]

    Reversibly Deformable and Mechanically Tunable Fluidic Antennas

    Ju-Hee So
    Abstract This paper describes the fabrication and characterization of fluidic dipole antennas that are reconfigurable, reversibly deformable, and mechanically tunable. The antennas consist of a fluid metal alloy injected into microfluidic channels comprising a silicone elastomer. By employing soft lithographic, rapid prototyping methods, the fluidic antennas are easier to fabricate than conventional copper antennas. The fluidic dipole radiates with ,90% efficiency over a broad frequency range (1910,1990,MHz), which is equivalent to the expected efficiency for a similar dipole with solid metallic elements such as copper. The metal, eutectic gallium indium (EGaIn), is a low-viscosity liquid at room temperature and possesses a thin oxide skin that provides mechanical stability to the fluid within the elastomeric channels. Because the conductive element of the antenna is a fluid, the mechanical properties and shape of the antenna are defined by the elastomeric channels, which are composed of polydimethylsiloxane (PDMS). The antennas can withstand mechanical deformation (stretching, bending, rolling, and twisting) and return to their original state after removal of an applied stress. The ability of the fluid metal to flow during deformation of the PDMS ensures electrical continuity. The shape and thus, the function of the antenna, is reconfigurable. The resonant frequency can be tuned mechanically by elongating the antenna via stretching without any hysteresis during strain relaxation, and the measured resonant frequency as a function of strain shows excellent agreement (±0.1,0.3% error) with that predicted by theoretical finite element modeling. The antennas are therefore sensors of strain. The fluid metal also facilitates self-healing in response to sharp cuts through the antenna. [source]

    Application of SAR interferometry to a large thrust deformation: the 1999 Mw= 7.6 Chichi earthquake in central Taiwan

    C. P. Chang
    SUMMARY Application of the interferometric method to four ERS2-SAR images acquired before and after the 1999 Chichi earthquake has allowed determination of the coseismic surface displacement in the footwall area of the Chelungpu fault. The interferometric results revealed a relative shortening in the round trip distance between the radar antenna and the ground of the footwall side of Chelungpu fault, during the earthquake. This shortening progressively increased from the west to the east and reaches the maximum amount of approximately 26 cm near the central segment of the Chelungpu fault. Our interferometric results have been precisely examined using a dense GPS network in the investigated area. We mapped the GPS coseismic measurements into the radar line of sight and implemented a forward simulation of SAR interferogram from this synthesized result to control our unwrapping performance. In this study, these two observations are compared with a 3-D dislocation model of the fault. Finally, a deformation analysis based on our interferometric result has indicated that a segment with irregular deformation behaviour can be distinguished in the footwall area of the Chelungpu fault. This segment may result from either the influence of inherited basement faults or the presence of a structural terrace that provide local opportunities for superficial deformation. [source]

    Adaptive pattern nulling design of linear array antenna by phase-only perturbations using memetic algorithms

    Chao-Hsing Hsu
    Abstract In this paper, the pattern nulling of a linear array for interference cancellation is derived by phase-only perturbations using memetic algorithms (MAs). The MAs uses improvement procedures which is obtained by incorporating local search into the genetic algorithms. It is proposed to improve the search ability of genetic algorithms. MA is a kind of an improved type of the traditional genetic algorithms. By using local search procedure, it can avoid the shortcoming of the traditional genetic algorithms, whose termination criteria are set up by using the trial and error method. The MA is applied to find the pattern nulling of the proposed adaptive antenna. This design for radiation pattern nulling of an adaptive antenna can suppress interference by placing a null at the direction of the interfering source, i.e. to increase the signal to interference ratio. This proposed method is that an innovative adaptive antenna optimization technique is also able to solve the multipath problem which exists in practical wireless communication systems. Two examples are provided to justify the proposed phase-only perturbations approach based on MAs. Computer simulation results are given to demonstrate the effectiveness of the proposed method. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Glycosylation status of haptoglobin in sera of patients with prostate cancer vs. benign prostate disease or normal subjects

    Tsutomu Fujimura
    Abstract We studied chemical level and glycosylation status of haptoglobin in sera of patients with prostate cancer, as compared to benign prostate disease and normal subjects, with the following results. (i) Haptoglobin level was enhanced significantly in sera of prostate cancer. (ii) Sialylated bi-antennary glycans were the dominant structures in haptoglobins from all 3 sources, regardless of different site of N-linked glycan. The N-linked glycans at N184 were exclusively bi-antennary, and showed no difference between prostate cancer vs. benign prostate disease. (iii) Tri-antennary, N-linked, fucosylated glycans, carrying at least 1 sialyl-Lewisx/a antenna, were predominantly located on N207 or N211 within the amino acid 203-215 sequence of the ,-chain of prostate cancer, and were minimal in benign prostate disease. Fucosylated glycans were not observed in normal subjects. A minor tri-antennary N-linked glycan was observed at N241 of the ,-chain in prostate cancer, which was absent in benign prostate disease. (iv) None of these N-linked structures showed the expected presence of disialylated antennae with GalNAc,4(NeuAc,3)Gal,3(NeuAc,6)GlcNAc,Gal, or its analogue, despite cross-reactivity of prostate cancer haptoglobin with monoclonal antibody RM2. (v) Minor levels of O -glycosylation were identified in prostate cancer haptoglobin for the first time. Mono- and disialyl core Type 1 O-linked structures were identified after reductive ,-elimination followed by methylation and mass spectrometric analysis. No evidence was found for the presence of specific RM2 or other tumor-associated glycosyl epitopes linked to this O -glycan core. In summary, levels of haptoglobin are enhanced in sera of prostate cancer patients, and the N -glycans attached to a defined peptide region of its ,-chain are characterized by enhanced branching as well as antenna fucosylation. © 2007 Wiley-Liss, Inc. [source]

    Achievable sum-rate analysis of correlated two-antenna MIMO uplink channels

    Jin-Woo Lee
    Abstract This paper analyzes the achievable sum-rate of correlated two-antenna multiple-input multiple-output (MIMO) uplink channels. Most of previous works have considered the case when a single user has multiple transmit antennas (i.e. multi-antenna single-user scenario). This paper considers the case when two-antenna MIMO uplink channels comprise two users with a single transmit antenna (i.e. single-antenna two-user scenario). The analytic and simulation results show that the achievable sum-rate of correlated single-antenna two-user MIMO uplink channels highly depends on the angle difference between the receive correlation coefficients of two users. It is also shown that the achievable sum-rate of correlated single-antenna two-user MIMO uplink channels is larger than that of correlated two-antenna single-user MIMO uplink channels and can even be larger than that of independent and identically distributed Rayleigh two-antenna MIMO uplink channels. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    A method of accurate determination of azimuthal distribution of received RF power

    A. A. Alexandridis
    Abstract In this paper, we introduce a method for the determination of directional distribution of received RF power, with angular resolution independent of receiving antenna radiation pattern. The proposed method is based on a series of measurements taken while rotating, at fixed predefined steps, a usual directional antenna of known radiation pattern on the azimuthal plain. It is proved that the resolution accuracy of the measurement method depends only on the angular step of the antenna rotation and it is independent of the antenna beamwidth. As a result of this feature, the proposed method allows the determination of the RF power angular distribution with fine resolution using a directional antenna of much wider beamwidth for the measurements. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    A global time domain circuit simulation of a microwave rectenna

    Brahim Essakhi
    Abstract The paper presents a global time domain simulation of a microwave rectenna studied for wireless energy transfer. The novelty of the work is to take into account both distributed electromagnetic parts of the antenna and the rectifier circuit including lumped elements. From a 3D finite element time domain electromagnetic modelling of the structure an equivalent circuit of the antenna is deduced: the input impedance is obtained as a function of frequency over a broad band. Then a rational approximation gives a corresponding PSPICE representation. The electromotive force induced between the ports of the antenna during the microwave illumination is directly computed from the 3D transient scattering problem. The resulting equivalent circuit of the antenna is finally incorporated into the electronic simulator PSPICE, together with the lumped components of the rectenna (ideal diodes and load). Thus a global non-linear time domain analysis of the whole structure becomes available. The results obtained with the methods presented in the paper are compared with those resulting from other techniques. The approach developed in the work could efficiently improve the design stage of rectennas devoted to microwave power transfer. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    The electromagnetic effect of cooling fins

    S. B. Chiu
    Abstract The electromagnetic effect of cooling fins is studied by solving Maxwell equations numerically using a FDTD method under high-frequency operating conditions. The fin is attached to a square IC chip to form a package. The overall size of the package is 25 mm × 25 mm × 17.5 mm. A smooth compact pulse with a reference frequency of either 1 or 2.5 GHz is used as the excitation source of EM waves. Six fin configurations are investigated. Computational results indicate that a fin can act as an antenna. For the present type of excitation source, resonance could occur roughly at frequencies of 2.5, 5 and 7.5 GHz, depending on the source reference frequency and fin geometries. Thus, fin effects should be considered in the electrical design phase since noises could be induced in the circuit due to the presence of fins. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    The computation of the input impedance of a biconical antenna by means of a method of segmentation based on 3D finite elements

    José Ma Gil
    Abstract The analysis of structures with complex geometries leads to the use of three-dimensional numerical methods. Such devices can be unmanageable unless a segmentation technique is applied. In this work, a hybrid 3D finite-element-mode matching method, based on the generalized admittance matrix (GAM) is applied to the computation of the input impedance of a biconical antenna fed by a cylindrical cavity loaded with resonant slots and matched by a coupling network composed of three multi-ridge circular irises and sections of circular waveguides. The structure is segmented into regions which are analysed separately and, by means of linking the partial matrices calculated, the generalized scattering matrix (GSM) is obtained. In order to validate the method, numerical results and measurements are compared. Copyright © 2003 John Wiley & Sons, Ltd. [source]